Looking farther afield, the prospects for learning more about the nature of supermassive black holes look very promising indeed - in both the near and distant future. Several major undertakings will improve our imaging and spectroscopic capabilities in both the radio and X-ray portions of the spectrum, and LISA (the Laser Interferometer Space Antenna) will open up a whole new window of opportunity for studying the distortions induced on the fabric of spacetime by violent gravitational interactions. As we have already seen (see Chapter 4), LISA's
3 See Green, Aldcroft, Mathur, et al (2001).
expected launch in 2010 will herald a bright new age of space exploration, stretching our frontier well beyond what radiation can let us see. By detecting gravitational waves undulating from distant blackhole sources, astronomers will be able to sense the behavior of massive objects in the presence of unimaginably strong fields, testing general relativity, and possibly even uncovering flaws that hint at new, more comprehensive descriptions and theories of nature.
The windows to be opened by ARISE (Advanced Radio Interferometry between Space and Earth; see Chapter 5) and more elaborate ground-based millimeter arrays will be equally fascinating and conducive to profound change in our communion with nature. Both of these developments - one stretching the baseline of radio interferom-etry into space, the other creating a worldwide baseline for interferom-etry at millimeter wavelengths - are geared toward greatly enhancing the resolving power of instruments designed to probe deeper and deeper into the bottomless well of gravity in supermassive objects. Many astrophysicists suspect that an image of the event horizon in a nearby black hole will be feasible within a matter of only years.4
Their impressive stature notwithstanding, existing radio telescopes (see Figs. 5.4 and 5.5) are not all usable at the shorter wavelengths because they cannot maintain sufficient structural integrity to provide a pure millimeter or submillimeter signal. So a major problem with conducting worldwide coordinated observations at these wavelengths is simply the paucity of appropriate sites.
The idea for developing a global network of millimeter telescopes, which has come to be known as CMVA - an acronym derived from Coordinated Millimeter VLBI Array - actually goes back to the mid 1990s, when members of the Haystack Observatory in Massachusetts developed plans to create the network for initial observations at 3 millimeters and additional experimental observations at 1.3 millimeters. Since then, the goal of the CMVA has been to
4 See, for example, Falcke, Melia, and Agol (2000), Bromley, Melia, and Liu (2001), and Melia (2003).
continually break new technological ground for later exploitation at progressively shorter wavelengths. Thus far, up to 12 stations around the world have been able to participate in global VLBI sessions at 3 millimeters, organized twice a year through the CMVA. Although unfavorable weather conditions and technical problems at some sites sometimes affect them, these campaigns are generally successful and provide good observations of compact emitting regions, including the galactic center.
At 1 and 2 millimeters, however, the number of telescopes is much smaller than at 3 millimeters, which greatly reduces the coverage. Thankfully, this situation is rapidly changing. For example, the new Heinrich-Hertz telescope on Mount Graham near Tucson recently participated in a VLBI experiment at 1 millimeter for the first time. Even more exciting is the proposed development of the giant radio telescope known as ALMA, which conveys better than any other project the growing enthusiasm from the world's astronomical community. The Atacama Large Millimeter/Submillimeter Array is conceived as a radio telescope composed of 64 transportable 12-meter-diameter antennas distributed over an area 14 kilometers in extent. In the early part of 2001, representatives from Europe, Japan, and North America met in Tokyo to sign a resolution affirming their mutual intent to construct and operate this facility in cooperation with the Republic of Chile, where the telescope is to be located. ALMA will be built on the Andean plateau at 5000 meters altitude near the Atacama Desert, and is considered to be the first truly global project in the history of fundamental science. The telescope is scheduled to be fully operational in 2010.
X-ray astronomy, on the other hand, must be conducted entirely above Earth's soupy atmosphere. The Chandra satellite - the latest NASA innovation - has merely given astronomers a taste of what X-ray images with exceptional spatial resolution can reveal. Scientists and engineers at the Goddard Space Flight Center in Maryland, at Columbia University in New York, and at CALTECH in Pasadena, among others, are conjuring up one of the most ambitious advances in the history of high-energy astronomy. Taking as their cue the lessons learned from the evolution of ground-based optical telescopes, in which many smaller units working in unison are in the end more powerful and easier to build than one single cumbersome device, these investigators are designing and building the Constellation-X Observatory (see Fig. 6.3). Four individual X-ray telescopes working together will have a combined sensitivity 100 times greater than any past or present X-ray mission.
More imaginative still is a NASA mission now under planning that purports to achieve nothing short of actually photographing the event horizon of several nearby supermassive black holes in X-ray light. A duo of powerful new NASA telescopes, with costs estimated in the billions of dollars, are being developed collaboratively by NASA and the University of Colorado at Boulder, and are proposed for flight before 2020. These telescopes are part of the Microarcsecond X-ray Imaging Mission, or MAXIM for short. The main mission would consist of a fleet of 33 spacecraft, each containing a relatively small telescope. But by combining the data gathered by so many separate instruments distributed over an extraordinarily large baseline in space, one may achieve a resolution of the sky about one million times better than what is currently attainable. A ground-based optical telescope with this same capability would enable us to read a newspaper on the lunar surface!
To put this achievement in context, note that at a distance of 60 million light-years, the event horizon of the 3-billion-solar-mass black hole in the nucleus of M87 (see Figs. 5.9 and 5.10) projects a diameter of 5 microarcseconds. MAXIM's intended resolution - the angular separation of features that it can identify - is about one microarcsecond, so future X-ray astronomers will be able to see the dark depression shimmering at the center of this giant elliptical galaxy. But with a projected width of over 30 microarcseconds, the easiest dark pit of all to photograph with MAXIM will be that projected by Sagittarius A* at the heart of the Milky Way.
This technology has its own problems to contend with.5 The wavelength of an X-ray is about 1000 times smaller than that of visible light, making X-ray telescopes very difficult to build. Surface irregularities that are too small to affect visible light can easily scatter X-rays. In addition, to obtain a true focus, X-ray photons must reflect twice from very carefully figured hyperbolic and parabolic surfaces, nested concentrically in very precise formation. Instead, MAXIM will utilize a method similar to VLBI, in which two or more telescopes are coupled in order to synthetically build an aperture equal to the separation of the individual instruments. Instead of precisely focusing X-rays with expensive mirrors onto a detector, the MAXIM team will use readily made flat mirrors to mix the photons, producing an even sharper image, similar to the way sound waves can be combined to either cancel each other out (resulting in silence) or amplify the sound when one crest adds to the other.
The concept calls for the fleet of smaller telescopes to be spaced evenly in orbit around the perimeter of a circle, the diameter of which will vary from 1 to 10 kilometers, and for the whole assembly to be orbiting about the Sun. From there they would collect X-ray beams and funnel them to a larger telescope stationed at the hub, which could then relay the accumulated data back to Earth, several million miles away.
6.5 is the universe itself a big black hole? The field of black-hole research is clearly in a period of renaissance, with wave upon wave of breathtaking discoveries creating headlines on a regular basis, it seems, and with future missions promising to take us to the edge of validity of current physical laws. Supermassive black holes are no longer the oddity of decades past, but rather a necessity in any comprehensive description of structure in the universe.
5 This work has been spearheaded by Webster Cash and his group at the University of Colorado, in collaboration with NASA's Marshall Space Flight Center in Huntsville, Alabama. They announced their design in the 14 September 2000 issue of Nature.
Some astronomers are taking this essential role to a rather daring conclusion, wondering, in fact, if we ourselves may be living inside the biggest black hole of all - the universe itself. Well, this question is not really well posed, as we shall soon see, but it does make for some intriguing reflection on cause and effect, and on the origin of all things.
A black hole is a parcel of closed spacetime embedded within a larger space (and time) that may contain matter, radiation, and probably other black holes as well. On the other hand, the universe as we know it is all encompassing, so for us to view it as a black hole, it would be necessary to hypothesize the existence of an undetected -and probably forever undetectable - hyperspace within which it is ensconced.
The major difficulty in maintaining a scientific posture with this discourse is that physicists do not yet have a complete theory unifying all the fundamental forces of nature at the instant of the Big Bang. They can say with some precision what transpired 10-43 second later, and any time thereafter, but that first fleeting moment borders on philosophy and aesthetics, not the rigor of verifiable hardcore science. For example, there is no possibility of linking current theories to experimentation with the early universe - that is, we cannot simply "build" another cosmos - so our theorizing must be accepted or rejected primarily on the basis of pure reasoning, and perhaps the power of prediction at later times.
The most unsettling, yet the most engaging, aspect of the Big Bang is the problem of beginning - the apparent singularity from which expansion started. An initial state of arbitrarily high density seems to be inescapable, just as catastrophic gravitational collapse evidently squeezes to zero volume matter falling into a bottomless well of gravity. In principle, understanding the process of gravitational contraction may resolve the mystery of our distant past, perhaps revealing new laws of physics along the way.
Still, certain issues pertaining to the question of the universe as a black hole may already be addressable within the current framework. Questions such as "Does the universe lie within its own gravitational radius, i.e., within its own event horizon?" and "What happens toward zero time in the current universe should we reverse the clock?" can at least be broached with the language of scientific principles already recognized and tested.
It may seem surprising to hear that the average density of matter within a black hole need not be extraordinarily large. Its value depends critically on how big the object is. The problem is simply to get enough material within a given radius to produce an event horizon at that radius. From Chapter 3, we recall that the Schwarzschild radius is 2GM/c2, so in effect the black hole's size scales directly with its total mass M. But for a given value of M, its density drops off inversely as the enclosed volume, which is proportional to the radius cubed. Thus, ponderous black holes actually have a significantly lower density than their lighter brethren. For example, if a 100-kilogram person were to suddenly shrink to black hole proportions, he would need to have a radius no bigger than about 10-23 centimeter, but his density would then rise to the extraordinary value of 1073 grams per cubic centimeter. The Sun, squeezed into a black hole, would have a 3-kilometer radius, but its density would be only 1016 grams per cubic centimeter.
Now consider what happens as we increase the mass further, to a value not unlike that of a typical supermassive black hole in the nucleus of an active galaxy. For a 100-million-solar-mass object, its Schwarzschild radius grows to 2.4 hundred million kilometers -roughly the size of Mars's orbit about the Sun. But its average density is incredibly only about 1 gram per cubic centimeter - the density of water!
An extremely large region of space, such as the universe, does not have to be very densely filled with matter in order to create curved light paths or even to entomb spacetime itself by forming an event horizon. Given that we see the universe from "inside," how does one then go about determining whether it is above its black-hole density or not? Part of the answer actually goes back to the work of Sir Isaac Newton who, in order to describe the moon's motion around the Earth, used the newly invented calculus to prove a very important theorem
122 the edge of infinity for his universal law of gravitation. He showed that the gravitational field outside a spherically symmetric body behaves as if the whole mass were concentrated at its center. In other words, the moon feels exactly the same gravitational influence from the Earth as it would from an object with the same mass, though only the size of an apple situated at the center of where Earth now stands.
In 1923, not long after general relativity was established, George Birkhoff (1884-1944) made the surprising discovery that Newton's theorem was valid even for this more comprehensive description of gravity, though with some appropriate corrections. He demonstrated that even if a spherically symmetric body were collapsing or expanding radially, the Schwarzschild metric describing its gravitational field in empty space would not change in time. In other words, the effect of gravity outside a spherically symmetric body does not depend on how big that object is - it is based solely on how much mass is enclosed within its surface.
The Birkhoff theorem seemed peculiar because in general relativity a nonstatic body generally radiates gravitational waves. We now know that in fact no gravitational radiation can escape into empty space from an object that looks the same from all directions, unlike the pair of black holes orbiting about each other in Fig. 4.5. His result may be applied with equal validity inside an empty spherical cavity at the center of a spherically symmetric (though not necessarily static) body. Here, however, there is no enclosed mass at any point within the cavity so, according to his theorem, there is no gravitational field anywhere inside it.
The value in Birkhoff's work is that, under the assumption of uniformity, we can calculate the gravitational field anywhere in the universe relative to another point a distance d away, by simply estimating how much mass is enclosed within a spherically symmetric volume of radius d centered on that other point. For the sake of specificity, let us just put ourselves in the middle and see how far out we need to go before we hit the universe's event horizon.
According to Hubble's discovery of an expanding universe back in the 1920s and 1930s, distant objects are receding from us with a velocity proportional to their distance. It turns out that this rate of recession approaches the speed of light for matter 12 billion light-years away, and this must therefore be the radius of that part of the universe with which we have interacted via influences that travel at the speed of light. (Two specific examples are electromagnetic and gravitational waves.) It is what astronomers call the size of the visible universe.
Birkhoff's theorem tells us that the average internal density required to produce an event horizon at 12 billion light-years is about 5 x 10-30 grams per cubic centimeter - an incredibly small number, the equivalent of only six hydrogen atoms per cubic meter. Even so, it exceeds the best current estimates astronomers have made by a factor of roughly three to five, depending on which newspaper vendor you talk to. Could the dark energy invoked to explain the universe's acceleration make up the difference (see Chapter 3)? Without it, the visible universe could not be a black hole in the strictest sense of the term, though it would come alarmingly close. Let us think about this for a moment. Of all the possible average densities that the universe could have had, why is it that the one with which it is apparently endowed is so strikingly close to the value needed to create an event horizon at the edge of what is visible?
Perhaps the answer lies in another important consideration we have so far ignored in this discussion. According to current cosmo-logical models, the expansion of the universe is driven not by matter moving through space, but rather by the stretching of space itself. This is more than just an idle concept since the very idea of inflation depends critically on the validity of an expanding space, and without inflation (see Chapter 3), many problems with the basic Big Bang model would go unsolved. The expansion of space, however, can proceed faster than the speed of light. The postulates of special relativity do not apply to this phenomenon, since they only specify what the maximum speed of transmission through the space can be, and that is the speed of light. So although we may not be able to see the "rest" of the cosmos beyond the visible limit at 12 billion light-years, it may nonetheless be there and expanding in concert with our own visible universe.
Can we therefore extend the radius of our Birkhoff sphere and intersect an event horizon by going beyond the "visible" limit? Well, no. For one thing, if this region is beyond the visible edge of the universe, then it is forever inaccessible to us, and we to it. The influence of gravity cannot travel faster than light either, so whatever mass is present there would never have communicated with the universe we can see, and they could never conspire to pool their influence and produce a common event horizon.
Nonetheless, the answer to the question "Is the universe itself a big black hole?" is a qualified "yes" because of several truly amazing observations completed by an international team of astronomers using the BOOMERanG experiment in 2000. We already touched on the significance of their findings in Chapter 4, but let us now revisit this discovery in the context of the present topic.
Designed to study the cosmic microwave background radiation with unprecedented accuracy, BOOMERanG surveyed 2.5 percent of the sky with an angular resolution of 0.25 degrees during a ten-day balloon flight over Antarctica. This microwave telescope was built to measure fluctuations in the background radiation (see Fig. 4.1) driven by pressure variations propagating throughout the nascent universe. A peak in the frequency of these variations was expected to occur 300 000 years after the Big Bang, when the matter and radiation ceased to interact via photon scattering. Earlier calculations had shown that a universe with a current average density of 5 x 10-30 grams per cubic centimeter would have produced fluctuations with a characteristic angular separation of about 0.75 degrees, well within BOOMERanG's resolving capability.
The team of astronomers who conducted this investigation, led by Paolo de Bernardis of the University of Rome and Andrew Lange of CALTECH, reported that BOOMERanG not only confirmed a primordial origin for the fluctuations, but also clearly identified a peak precisely where these predictions had placed it. The location of the peak means that the density of matter in the universe is within a statistically determined error of only 10 percent of its critical value.
Physicists already know that the combined density of visible and dark matter, and radiation, amounts to only about one-third of the required 5 x 10-30 grams per cubic centimeter. So the rest of it must be the "dark energy" inferred from the accelerated expansion of the universe. Although the evidence for this phenomenon is still rather tentative,6 cosmologists find it very gratifying that together with the completely independent determination rendered by BOOMERanG, they now paint a self-consistent picture. The cosmos is evidently dominated by dark energy, but in such a way that its overall equivalent mass density is precisely 5 x 10-30 grams per cubic centimeter. The universe, it seems, has an event horizon with a radius of 12 billion light-years, right at the edge of what we can see before the velocity of expansion exceeds the speed of light.
This universe, however, has no apparent singularity right now -its mass is spread out everywhere. Could it be that the Big Bang was nothing more than the initial collapse of the universe to something approaching a point, followed by a bounce? Yes, it's possible, but we may never know for sure because the first 10-43 second of the expansion is completely unresolvable with current scientific methods. Let us reverse the clock, and see how far back our present knowledge can take us toward the beginning, and why this interval of 10-43 second, known as the Planck time, appears to be impenetrable.
The shortest interval of time that can be probed with current physical laws pushes their applicability to the limits set by three so-called fundamental constants of nature. These are the measured values of quantities that characterize the strength of gravity, the speed of light, and the fuzziness of quantum mechanics. Physicists assume
6 See Brian P. Schmidt et al. (1998) and Saul Perlmutter et al. (1999).
that these quantities are constants in time, in the absence of any evidence to the contrary.
Quantum mechanics argues that we can never be entirely sure of a particle's position or its energy, because in order for us to even know of its existence we must disturb it to sense its presence. Thus, there should always be some positional uncertainty, or an imprecision in energy and time, and any description of the particle's physical behavior must therefore acquire some minimal level of "fuzziness." In our everyday lives, we develop the illusion of precision only because the fuzziness induced by these uncertainties is very small, and our mind clings to the apparent clarity of the outside world as a convenient simplification of the way things really are. Certainly, on a macroscopic scale, this fuzziness does not manifest itself readily, and our description of nature using exact positions and times is quite adequate for our need to interpret much of the activity in our environment. But on a microscopic scale, this fuzziness is paramount, and nothing can happen without the consequences of the implied imprecision.
The uncertainty in the particle's position is characterized by Planck's constant, h. The Planck length - the shortest distance we can probe - depends on how strong the effect of gravity is on such scales. This in turn is specified by the gravitational constant, G, in Newton's universal law of gravitation. The bigger this coupling constant is, the stronger is the attraction between two given masses. The Planck time is then the interval of time required to communicate information across this distance, given that the apparent maximum rate of transmission is the speed of light, c. Together, these constants yield the shortest physical time, (Gh/c5)2 (which is approximately 10-43 second), that anyone (or anything) can sample.
However, cosmologists do have some confidence in beginning to describe the expansion of the universe from 10-43 second onwards. This is where our quantum physics has meaning, because on this level the Schwarzschild radius from general relativity first becomes equal to the smallest scale permitted by the quantum fuzziness, roughly
10-33 centimeter, which is still much smaller than the nucleus of an atom. But there is still some remaining uncertainty because physicists diverge in their views of how one should best describe the universe at this point. They still do not know if extra dimensions exist (see Chapter 3), or if string theory is correct. One view has it that during the Planck era (when the universe was about 10-43 second old), the cosmos should best be described as a quantum "foam" of ten spatial dimensions containing Planck-length-size black holes, continuously being created and annihilated, with no cause or effect. The reason for the latter is that, on quantum scales, particles can be created without the conservation of energy, as long as they exist only fleetingly so that the violation falls within the uncertainty prescribed by Planck's constant.
One of the reasons our physics is incomplete near the Planck era is related to the hierarchy problem we discussed in Chapter 3. Science does not yet provide a description of how the forces of nature unify during this time. At the excruciatingly high energies and temperatures prevalent then, the forces of nature would have become symmetric, meaning that they would have resembled each other and would have acquired a similar strength - they would have unified into a single entity. Physicists are actively pursuing the grail of grand unification of all four forces, and have already achieved some notable success in this pursuit. Toward the end of the twentieth century, the interactions due to the weak and electromagnetic forces were framed into a single phenomenon known as the electroweak force by Sheldon Glashow, Steven Weinberg, and Abdus Salam, who were awarded the Nobel Prize in Physics for this effort in 1979.
The weak force, which is mediated by very heavy particles known as W and Z, is responsible for the transformation of a neutron into a proton within the nucleus of an atom, whereas the electromagnetic force provides an interaction between charged particles, such as the electron and a proton. At the time of their discovery in 1983, the W and Z particles were the most massive known - each weighing in at almost 90 times the mass of the proton - whereas the photon, the carrier of the electromagnetic force, is massless. The unification of these two forces occurs when the energy available for the process is so high that even this enormous mass difference between the two sets of carriers becomes inconsequential. In the early universe, this would have been the situation until the ambient temperature dropped below about 1015 Kelvin, after which the mass difference would have split the rates at which these particles could interact, thereby creating the appearance of two independent forces.
Attempts are now underway to unify the strong and electroweak forces, a process known as Grand Unification, but this is proving to be much more challenging, in part because what is required is the conversion of certain particles, such as electrons, into completely different types of entities, known as quarks. This unification, if possible, would result in a split of the rates of interaction when the temperature in the early universe dropped below about 1027 Kelvin, much closer to the Planck era.
The final unification, between the electroweak, strong and gravitational forces, is well beyond the realm of study with earthbound experiments, because the energies and temperatures required to approach the necessary scale of interaction are simply unreachable. It may seem peculiar, but learning more about the early universe may actually be necessary for this branch of particle physics to make progress of its own toward a "complete" understanding of what governs the substance and behavior of particles.
These unknowns impact the cosmologists' view progressively more and more, as they labor closer and closer to the Planck scale. The exploration terminates - indefinitely it would seem - at 10-43 second. Only the development of a completely new, overarching description of nature that obviates the fuzziness of quantum mechanics could change this situation. Still, physicists are a clever lot, so there is always hope. Is the Universe itself a big black hole? It now seems that the answer is yes, but how and why it got that way persist as the most profound mysteries in nature.
supermassive black holes in the universe 129 6.6 ultimate fate
Counterposing the uncertainty of what transpired at the very beginning of the Big Bang, the question of how the universe will play itself out may be easier to address, though, as always, the story unfolds through the prism of human perception and interpretation. It would be utterly presumptuous and self-debilitating for us to view this prognostication as absolute and fully written. On the contrary, it is an evolving narrative, likely to be swayed by many future developments and discoveries in particle physics and astronomy.
For now, the three leading characters in this play are the total mass enclosed within the visible universe, the Grand Unified Theory (GUT) that will ultimately account for the unification of all known forces, and Hawking radiation. Up until the era when the reservoir of primordial matter - primarily hydrogen and other light elements - is fully exhausted, stars will continue to form and galaxies will collide and grow. Looking into the future, however, matter will ultimately partition itself into several quasi-terminal states, among them dying stellar embers, white dwarfs and neutron stars, asteroids and planets, and tenuous gas dispersed throughout the cosmos. But regardless of what the eventual configuration will be, life as we know it will not be viable forever. Without the energy released from nuclear burning, life-sustaining environments will become untenable. In the meantime, supermassive black holes will continue to grow as clump after clump of gas succumbs to the inexorable inward pull of gravity, adding to the total mass entombed below the growing number of event horizons.
Life will undoubtedly evolve considerably and survive much longer than we could now imagine. In the absence of nucleosynthesis, our descendants may even find a way of using energy liberated by accretion onto black holes in order to power their survival. But certain processes predicted by the GUT will change the universe dramatically and irreparably, making any such attempts futile in the long run. In these theories, all sorts of particles can (and must) mutate into other entities, a process that may be induced by either collisions or spontaneous self-decay. A proton, for example, will eventually split into a positron (the electron's antiparticle) and a pion, the particle that helps to mediate the nuclear force. Neutrons are already known to be unstable; in a matter of only minutes, they decay into protons (this process is induced by the weak force), so they too must eventually split into sub-components. By permitting this conversion - nay, requiring it -the GUT will guarantee that the two most significant constituents of atomic nuclei will be removed permanently from the composition table. Diamonds are not forever!
Physicists still do not know the mass of several particles that mediate the unified force, so the time required for protons and neutrons to decay is uncertain. The best current estimates endow the proton with an expected lifetime somewhere between 1032 and 1041 years.7
By this time, galaxy collisions (see Chapter 4) will have been relegated to ancient history by the expansion of the universe, which would have continued to drive the participants apart. Supermassive black holes will therefore stop growing some day because they will have absorbed all the limited supply of matter in their environment. Estimates place the terminal mass of these objects somewhere between 1 billion and 10 billion Suns.
The universe in this era will be completely unrecognizable to sentient beings living now, since it would have mutated to the point where life itself would be impossible. As best as physicists can tell, the cosmos will be an extremely thin dark veil of fundamental particles, such as electrons, positrons, neutrinos, and highly redshifted photons. Very few atoms will be left, and these too will eventually vanish as their constituent protons and neutrons disintegrate. And floating aimlessly through this enormous sea of virtually nothing will be the ensemble of billion-solar-mass black holes roaming freely for a near eternity, sucking up whatever scant morsels they encounter.
7 A full discussion of the relevant parameters and other considerations may be found in Adams and Laughlin (1997).
Evidently, supermassive black holes appeared early in the history of the universe and will stay late - very late. After 1032 to 1041 years, they will be the only structures of any significance left in the cosmos. But in what appears to be the final act of fair play, even they will not exist forever. Once black holes stop growing, they slowly begin to shrivel via a loophole created by the application of quantum mechanics, a theory that is known to be correct, if not complete. General relativity is a classical theory, operating on the basis of precise measurements of physical quantities, such as distance and time. The very notion of defining an event horizon makes sense as long as we can precisely place this surface and particles around it at perfectly known locations. But quantum mechanical fuzziness requires some positional uncertainty, or an imprecision in energy and time. Physicists are therefore uncomfortable with the idea of a perfectly localized and sealed event horizon, since these notions completely ignore the quantum mechanical uncertainty on the smallest scales.
A phenomenon discovered in 1974 by Stephen Hawking may be the first step in the eventual resolution of this problem.8 The name itself, quantum mechanics, reveals the essence of the physical description on a microscopic scale. It tells us that at this level all measurable entities are to be thought of as comprising tiny bundles (or quanta) of "something," which in the case of light are known as photons. In the appropriate terminology, one says that fluctuations in a field, say the gravitational field, are associated with the manifestation of these quanta, which can appear or vanish as the fluctuations grow or subside. The connection between these bundles and the fuzziness is that their size, energy, and lifetime are directly related to the scale of the imprecision, that is, how fuzzy the measurements of position or energy turn out to be.
Quanta such as photons bubble up spontaneously out of vacuum if an adequate source of energy lies nearby. But a crucial fact that we
8 Readers who would like to learn more about the technical aspects of this phenomenon, and the evaporation of black holes in general, will find the discussion in Thorne, Price, and Macdonald (1986) very helpful. See also Wald (1984).
have gathered from the observed behavior of these fields is that when the bundles materialize spontaneously, they always do so in pairs, as if something must be split in order to create the fluctuation. So a quantum, or particle, with negative charge can only materialize if at the same time its counterpart, with positive charge, also comes into being. Given that every characteristic we can assign to this bundle must be matched by the opposite attributes of its partner particle, it makes sense then to talk of these as particles and antiparticles, or matter and antimatter.
The phenomenon discovered by Hawking9 is directly associated with this creation of quantum particles in vacuum due to fluctuations in the gravitational field of the black hole. Particles created in this way live fleetingly and then annihilate with each other's counterpart to re-establish the vacuum after the fluctuation has subsided. We note, however, that fluctuations in the gravitational field of the black hole have a wavelength commensurate with its size. So when these fluctuations manifest themselves as photons, or any other type of particle whose rest mass is small compared to the amplitude of the fluctuation, their wavelength, too, corresponds to the size of the black hole. The fleeting quanta produced beyond the event horizon of very massive black holes are therefore much redder, and hence of lower energy, than those associated with their smaller brethren.
The paired quanta produced in this fashion annihilate outside the event horizon very quickly (in about one-millionth of a millionth of a millionth of 1 second). But some pairs, argued Hawking, will have a member that dips below the membrane of no return, abandoning its partner to the whim of the outside universe. Without a partner to annihilate, the detached particle flees the black hole's sphere of influence and merges into the flux of escaping radiation headed for infinity. To an observer on Earth, this looks like the black hole is actually radiating, though the mechanism is clearly indirect. Nevertheless, the
9 Some of Hawking's early discussion on this topic appeared in a paper published by Nature in 1974.
source of energy for these fleeing particles is ultimately the black hole itself, and although we cannot claim that the radiation originated from within the event horizon, its energy surely did, and the dark object pays the price with a consequent decrease in its mass. If this simple application of quantum mechanics survives the test of time, it appears that all black holes must evaporate eventually.
The Hawking radiation from a black hole with barely the mass of 30 Suns has such a long wavelength, and is therefore so feeble, that it would take such an object 1061 times the current age of the universe to evaporate completely. But after 1098 years, even the 100-billion-solar-mass behemoths will be gone, completely and forever - the final act of fair play. And thus will end the saga of the most powerful objects in the universe, facing eternity as ghosts in a lifeless darkness.
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The Planetary Society Blog 22 Feb 2019, 00:24 UTC Japan's Hayabusa2 spacecraft has successfully touched down on the surface of Ryugu! The touchdown happened about 35 minutes earlier than expected, catching even some of the project scientists off-guard. During a live broadcast from JAXA's control room in Sagamihara, cheers suddenly erupted, causing some initial confusion about whether Hayabusa2 had actually touched down. Soon afterward, via a superb Japanese-to-English translator who narrated the broadcast, a JAXA scientist reported, "There was some deviation from the simulation graph, but the results are that everything went according to plan."
Spaceflight Now 21 Feb 2019, 22:23 UTC The Beresheet moon lander will attempt to become the first privately-funded spacecraft to reach the moon, and these photos show the robotic probe’s journey through testing inside a clean room at Israel Aerospace Industries, followed by its attachment to a multi-satellite stack for launch on a Falcon 9 rocket.
Japan’s Hayabusa2 is About to Shoot Up the Surface of Ryugu with Tiny Impactors so they can Collect a Sample21 Feb 2019, 17:54 UTC Japan’s Hayabusa2 mission is about to get down to business. After arriving at asteroid Ryugu at the end of June 2018, and dispatching its tiny rovers to the surface, the spacecraft is about to approach the surface of the asteroid and get some samples.
Starts With a Bang! 21 Feb 2019, 15:01 UTC There are people alive today who can remember a time where no human-made creation had ever crossed the line from Earth’s atmosphere into space. Even today, it’s incredibly costly to launch a device into space, and it requires even more power than that to escape from the gravitational pull of our planet entirely. As the space race unfolded, humanity left the bonds of Earth’s orbit, walked on the surface of the Moon, and sent space probes to every other planet in our Solar System. A couple of those spacecraft sent to the farthest reaches of space have now exited our Solar System: Voyager 1 and 2. On their way out, however, powered by their fading nuclear power sources, one of them took a look back at the planet that spawned its existence. On February 14, 1990, Voyager 1 captured this photo of Earth: the Pale Blue Dot. Our view of our home world has never been the same since.
The Planetary Society Blog 20 Feb 2019, 19:49 UTC InSight has placed its second science instrument on the ground and set it free.
Centauri Dreams 20 Feb 2019, 17:35 UTC It seems increasingly clear that the factors that govern what kind of a planet emerges where in a given stellar system are numerous and not always well understood. Beyond the snowline, planets draw themselves together from the ice and other volatiles available in these cold regions, so that we wind up with low-density gas or ice-giants in the outer parts of a stellar system. Sometimes. Rocky worlds are made of silicates and iron, elements that, unlike ice, can withstand the much warmer temperatures inside the snowline. But consider: While we now have 2,000 confirmed exoplanets smaller than three Earth radii, the spread in their densities is all over the map. We’re finding that other processes must be in play, and at no insubstantial level. Low-density giant planets can turn up orbiting close to their stars. Planets not so dissimilar from Earth in terms of their radius may be found with strikingly different densities in the same system, and at no great distance from each other.
Starts With a Bang! 20 Feb 2019, 15:01 UTC When it comes to the elements of the Universe, every one of them has its own unique story. Hydrogen and helium were created in the earliest stages of the Big Bang; light elements like carbon and oxygen are created in Sun-like stars; heavier elements like silicon, sulfur and iron are created in more massive stars; elements beyond iron are made when those massive stars explode in supernovae. But the most massive elements of all at the very high end of the periodic table — including platinum, gold, radon, and even uranium — owe their origins to an even rarer, more energetic process. The heaviest elements of all come from merging neutron stars, a fact that was long suspected but only confirmed in 2017. Here’s the cosmic story of how the Universe got there.


Published September 14, 2006
by AuthorHouse UK DS .
Written in English
|The Physical Object|
|Number of Pages||88|
This book did help me somewhat, but I just wish there was more information that incorporated the 13th sign, and its effect on us all. And as a bonus, she also introduced me to flower remedies, which I think could be beneficial to many, as well as certain foods which might help each of us improve our well-being.4/5(20). At the dawn of time, there were 13 Houses in the Zodiac Galaxy. Now only 12 remain Embark on a dazzling journey with ZODIAC, the first novel in an epic sci-fi-meets-high-fantasy series set in a galaxy inspired by the astrological signs. Astrology of the Thirteen Signs of the Zodiac is a book which explains a new theory in this ancient field of study. It was prompted by the fact that Western Astrology has outlived its lifetime and its elements have been rendered obsolete by its cousin, the science of astronomy. The precession of the. Book Review: Astrology of 13 Signs of the Zodiac: An Interesting Insight About Zodiacs Astrology is an interesting subject as far as most of the people are concerned. During my college days I read Linda Goodman’s Sun Signs many a times and every time I used to /5.
14 rows The 13th zodiac is Ophiuchus. Zodiac Signs Aries MarApr Taurus AprMay . The legend of Ophiuchus’s downfall exists mainly as a common myth in Zodiac storybooks, told as a cautionary tale to all the children across the galaxy. Each House tells different versions of the story, but the most common form of the legend goes like this. "I’m so grateful for an awesome store and workers at Nirvana! A mother and daughter combo that makes the shopping experience the best! Thank you for giving me a taste of Colorado in Fort Wayne 🏼🏔"😃. “Under the 13th sign, I would be a Libra, which makes absolutely no sense to me. As the people-pleasing and most indecisive sign of the zodiac, Libras like to weigh both sides of every story.
If we return to the true astronomical roots of the signs of the zodiac, we will see that there are 13 signs, not 12 as the modern horoscope tells us. Reclaiming the forgotten Ophiuchus invites each of us to discover our correct astrological sign and contemplate the spectacular zodiacal constellations that dominate the nights at this time of year. Read A/N Special: About this Book from the story Zodiac High: The 13th Zodiac by Lucid_fantasies_ (💖Destiny💖) with reads. aries, libra, fantasy. Three ye Reviews: 6. According to Zodiac Books, qualities of an Ophiuchus are: “House Ophiuchus represented unity. Its people were spirited, magnetic, impulsive, clever, flamboyant, and at times jealous, power Author: Tess Koman. Zodiac is a non-fiction book written by Robert Graysmith about the unsolved serial murders committed by the "Zodiac Killer" in San Francisco in the late s and early '70s. Since its initial release in , Zodiac has sold 4 million copies worldwide. Graysmith was a cartoonist for the San Francisco Chronicle and later also wrote Zodiac Unmasked.


Galaxy Zoo Talk
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Read the post, so I thought I would add the tag #asteroid
Posted October 9, 2015 12:56 PM
what are the green and purple "doughnuts" at about 2:00?
Posted November 24, 2015 8:02 PM
According to one of the project scientists they are asteroids 😃
Posted November 24, 2015 8:06 PM


November 30, 2020
Download MP3 (right click to save)
One vacation morning, my wife and I woke up real early for some reason - so we decided to make the most of that pre-dawn time. We went out to the porch of the mountain cabin we were in and we just sat there to watch the sunrise. It was awesome! We watched the eastern sky slowly brighten over the mountains, and it turned the sky these beautiful shades of pink and yellow. It took a while for the old sun to rise. I mean, we were waiting for almost an hour as the sky gradually got brighter. At last, there was this brighter spot over one particular peak, and then suddenly there it was - the sun crested the mountain. And even though we had to wait a while for the sun to come up, wow! Man, when it did, it totally cleared the mountain and it began ascending the sky in less than two minutes! Literally, as it rose, everything seemed to come to life across the valley. It's incredible to watch how God begins a day!


2:30 PM - 2:45 PM
[MTT48-04] Iron isotopic compositions of Luna 16, 20, 24 soils
At present, there are no lunar meteorites collected as fall, thus, returned samples of the Moon are important for lunar Fe isotopic studies. In this study, we have measured Fe isotopic ratios of soil samples from the Soviet Luna missions, Luna 16, 20, and 24, using MC-ICP-MS. A highly matured sample from Luna 16 shows clearly distinguished Fe isotopic compositions between the fine-grain and coarse-grain fractions, while such Fe isotopic discrepancies among different size fractions were much smaller in submature (Luna 20) and immature (Luna 24) samples. The Fe isotopic ratios of separated grains show that agglutinates have higher δ57Fe values than the bulk and monomineralic grains, indicating the abundant np-Fe0s in agglutinates and the partial evaporation of Fe during its melting.
The δ57Fe value for the coarsest grain fraction of very low-Ti basalt from Luna 24 was found to be 0.08 ± 0.04‰, which is the first Fe isotopic composition reported for very low-Ti mare basalts. This value is clearly lower than previously reported δ57Fe values for high-Ti and low-Ti basalts, and is nearly identical to those of Mg-suites. This observation is consistent with the Fe isotopic evolution model during differentiation of lunar magma ocean . Furthermore, the Fe isotopic ratio of the very low-Ti basalt is indistinguishable from that of the Earth’s mantle, thus, the bulk silicate Earth and Moon are considered to possess an identical or very close Fe isotopic composition.
References:  Poitrasson et al. (2009), EPSL, 223, 253-266.  Liu et al. (2010), GCA, 74, 6249-6262.  Sossi and Moynier (2017), EPSL, 471, 125-135.  Wang et al. (2015), EPSL, 430, 202-208.  Wiesli et al. (2003), EPSL, 216, 457-465.  Moynier et al. (2006), GCA, 70, 6103-6117.  Wang et al. (2012), EPSL, 337-338, 17-24.


Please note: the AAS Obituaries are temporarily being hosted on this website while their full content is being ingested into the PubPub publishing platform newly adopted by the Bulletin of the American Astronomical Society. When the migration is complete, your existing links will take you to the final, migrated content. Contact firstname.lastname@example.org with any questions.
An obituary for Phyllis Freier, cosmic ray researcher and longtime member of the Physics Department of the University of Minnesota, will appear in approximately the December, 1993 issue of Physics Today.
BAAS Citation: BAAS, 1993, 25, 1496


t When Patrick passed away , i made a comment that the show should be taken off air and a new show put in it's place. They can still use the same people and maybe a few new ones . It also needs a better time slot and a bigger slot too so younger audiences can also view. With all that is going on in the world of astronomy and Space, they will not run short of topics. Also should include a section on getting started e g :- teaching Constellations,all about the planets , equipment to use , so on and so forth. It saddens me that the program is ending , I grew up with it like most of us , but it was Sir Patrick's baby. The current team, I feel , are constantly walking in Sir Patrick's shadow while the show is called Sky at Night ? When I think of that program I think of Patrick . Also an half hour show is just not long enough for this type of program. If they had their own show , the team's own personality would come shining through , they may have their own ideas they would like included. It is so important for something to continue . I bet most of us got started with Patrick and sky at night , myself included. We have to give the younger ones the same opportunity. |Thank you for letting me make this comment . Pam Ward.


Two hi-tech Westcott based companies are working together to develop steam technology for satellites.
SteamJet Space Systems and Total Carbide will work together on producing a steam-fuelled propulsion system which will be used on small satellites including miniature CubeSats.
The companies met at the monthly Space Innovators networking event at the Westcott Space Cluster and realised their technologies had real synergy. As a result, Total Carbide, which specialises in highly durable tungsten carbide manufacturing, will support the production of SteamJet’s innovative propulsion system, believed to be the first of its kind in Europe.
Funding has come from support provided by the Westcott Incubation Centre (WBIC) which led to SteamJet receiving a £5,000 grant from the UK Space Agency.
Both firms are also part of the Westcott Space Cluster of companies and members of the Government’s SPRINT programme which provides funding for innovative firms in the sector.
SteamJet Director Dr Marco Pavan said: “We were the first company to join the Westcott Business Innovation Centre in June 2018 and it has been an ideal location as there is an ecosystem of space sector firms on the Park which has led to this collaboration.
“Total Carbide specialises in the sort of skilled, highly accurate manufacturing to deliver this type of production and we have also had business and funding support which has been really helpful.”
A prototype of the propulsion system has now been built and will be tested in space-simulated conditions in Southampton by the end of March with a patent due to be filed.
More than 3,000 CubeStats will be sent into orbit in the next five to six years driven by demand for earth observation and telecommunications. The technology will enable satellites to stay longer in space, change and optimise their orbit, avoid collisions, operate in constellations and de-orbit.
Andreas Hohmann, Managing Director of Total Carbide, said: “It’s great to be working with another Space Cluster business at Westcott. We have worked in the space and aviation sectors for years and produce components for the Rolls Royce jet engines and for Collins Aerospace, so this is an exciting addition to our client portfolio.”
With its six-strong workforce likely to expand, SteamJet will soon require larger office space and are hoping to move into the new Westcott Innovation Centre at the Park once built in 2020.
Nigel MacKenzie, Project Manager at Westcott, said: “A big part of our message is collaboration and we are committed to building a positive eco system which will attract like-minded companies and individuals to develop their ideas.
“It’s great to see SteamJet and Total Carbide working together to bring this new innovation to life.”


I was first hooked on the night sky when I was a much younger and much shorter version of myself. It was at a campground beside a creek that is the beginning of the Rio Grande River. The trout fishing was excellent. So was the stargazing because the campsite was near Creede, Colorado, elevation 8,700 feet.
The nights are chilly even in the summer, and the sky usually crystal clear. It took a couple such nights before I moved away from our campfire and into the surrounding darkness. I do not know why I looked up but I did and was stunned by the Milky Way and an uncountable number of stars — at least a billion it seemed to me. It appeared close enough to touch.


Mr Moon - The Mysterious Invention
Mr Moon, Episode 47 - The Mysterious Invention
During this intergalactic animated series, Mr Moon and his friends, Silva and Gold Star, explore the universe on his superfast moon rocket.
Episode 47 - The Mysterious Invention
Mr Moon finds Gold Star's latest invention - and everybody comes up with different imaginative suggestions as to what it is... until Gold Star returns and tells them it's an imagination sparker.
Previous Episode Synopsis
Episode 44 - Sunny's Funnies
Left alone to babysit Sigma, Sunny makes up a funny story about two Space Pirates - Draco the Dreadful and Captain Great Bear.
- 6:15pm Tuesday, April 02 (R)
- 6:15pm Wednesday, April 03 (R)
- 6:15pm Thursday, April 04 (R)
- 6:15pm Friday, April 05 (R)
- 6:15pm Saturday, April 06 (R)
- 6:15pm Sunday, April 07 (R)


This is a difficult question to answer without knowing the specific location of your house. In general, houses in the northern hemisphere will get more sun on the south side, while houses in the southern hemisphere will get more sun on the north side. The amount of sun your house gets can also be affected by trees or other buildings nearby.
- The Animals – House of the Rising Sun (1964) HQ/Widescreen ♫ 58 YEARS AGO
- Sun Path Over My House
- How Much Sun Does My House Get for Solar Panels
- Sun Path Over My House Google Maps
- Sun Path Over My House App
- Sun Position Calculator
- How Do You Know How Much Sunlight an Area Gets?
- Can Google Maps Show Sun Path?
- Where Does the Sun Hit My House the Most?
- What Part of My Roof Gets the Most Sun?
The Animals – House of the Rising Sun (1964) HQ/Widescreen ♫ 58 YEARS AGO
If you’re wondering how much sun your house gets, there are a few things you can do to find out. First, you can look at a solar map of your area to get an idea of the average amount of sunlight that hits your region. You can also use a compass to find out which direction your house faces and then look up the sunrise and sunset times for that day.
Finally, you can go outside and take a look around to see if there are any trees or other obstructions that might block the sun’s rays. Knowing how much sun your house gets is important for a few reasons. If you’re considering installing solar panels, for example, you’ll want to make sure there’s enough sunlight available to make them worth the investment.
Additionally, if you have plants inside your home, they’ll need a certain amount of sunlight to thrive; too little sun could result in unhealthy plants. So how much sun does YOUR house get? Take some time to find out and then use that information to determine whether solar panels or other measures are right for you.
Sun Path Over My House
The sun is one of the most important things in our solar system. It is the largest object in our solar system. The sun gives us day and night, it warms our planet, and it helps to keep us alive.
The sun is a star that is located in the Milky Way galaxy. It is about 150,000 times the size of Earth and has the mass of about 333,000 Earths. It is so large that it takes up about 99.86% of the total mass in our solar system.
The sun is huge and bright because it is made mostly of hydrogen gas. This gas makes up about 74% of the sun’s mass. Helium makes up about 24% of the sun’s mass while all other elements make up less than 2%.
The sun produces its own light and heat through nuclear fusion reactions. These reactions occur when atoms combine to form new atoms. This process releases a tremendous amount of energy that travels to the surface of the sun where it escapes as sunlight and heat energy.
Nuclear fusion reactions require very high temperatures for them to occur which explains why the inside of the sun is so hot! The temperature at the center of the sun can reach 27 million degrees Fahrenheit (15 million degrees Celsius). That’s almost 10 times hotter than what scientists think is necessary to fuse hydrogen atoms together!
All this heat energy creates convection currents within the Sun. Convection occurs when heated fluid rises while cooler fluid sinks due to gravity forces pulling downward.
How Much Sun Does My House Get for Solar Panels
If you’re considering solar panels for your home, one of the first things you’ll need to know is how much sun your house gets. This will determine the size and number of panels you’ll need to generate enough electricity to power your home.
There are a few ways to measure the amount of sun your house gets.
One is to use a solar tracker, which is a device that tracks the movement of the sun across the sky and calculates the amount of sunlight hitting your property. You can also use a digital camera or smartphone with an app like Sun Seeker to take pictures of the sun’s position at different times throughout the day. Or, you can simply observe how much direct sunlight hits your property at different times throughout the day and estimate from there.
Once you have an idea of how much sun your house gets, you can start sizing up solar panel systems. The average residential solar panel system ranges from 5kW-10kW, so if your house gets a lot of sun, you may be able to get by with a smaller system. Conversely, if your house doesn’t get as much direct sunlight, you’ll need a larger system to generate enough electricity to power your home.
So how much sun does YOUR house get? Get out there and find out! It’s an important step in going solar.
Sun Path Over My House Google Maps
When I was younger, I was fascinated by the sun. I would spend hours outside tracking its movements across the sky. As an adult, I still find myself drawn to the sun and its power.
So, when I found out that there was a way to track the sun’s path over my house using Google Maps, I was intrigued. To use this feature, simply go to Google Maps and type in your address. Then, click on the “Sun” icon in the top right corner of the map.
A box will pop up showing you the current position of the sun and its path for the next few hours. This is a great tool for planning outdoor activities or for simply admiring our amazing star. So next time you’re curious about where the sun is, be sure to check out Google Maps!
Sun Path Over My House App
Do you ever look up at the sky and wonder where the sun will be at different times of the day? Well, now there’s an app for that! The Sun Path Over My House app allows you to see a map of the sun’s path over your house at any time of year.
This app is great for planning solar projects, such as solar panels or solar ovens. It can also help you plan your garden so that you can maximize the amount of sun exposure your plants get. And if you’re just curious about where the sun will be at different times of day, this app is for you too!
The Sun Path Over My House app is available for iOS and Android devices.
Sun Position Calculator
There are a lot of things to consider when trying to calculate the sun’s position. The first thing you need to know is the latitude and longitude of the location where you want to calculate the sun’s position. You also need to know the date and time that you want to calculate for.
Once you have all of that information, you can use a sun position calculator like the one at TimeAndDate.com to get detailed information about the sun’s position. The results from the calculator will tell you things like the azimuth and elevation of the sun, as well as how long it will be until sunset. If you’re trying to figure out when sunrise will be, you can use the “inverse” function on most calculators to get that information.
Knowing the sun’s position can be helpful for a variety of reasons. For example, if you’re an astronomer, photographer, or even just a casual stargazer, being able to find the sun in relation to other objects in the sky can be very useful. Or, if you’re trying to get a tan without getting burned, knowing when the sun is at its highest point in the sky can help you plan your day accordingly.
How Do You Know How Much Sunlight an Area Gets?
There are a few ways to determine how much sunlight an area gets. One way is to use a light meter. A light meter is a device that measures the amount of light in an area.
It is important to note that the amount of sunlight an area gets can vary depending on the time of day and the season. Another way to determine how much sunlight an area gets is to use a solar calculator. A solar calculator takes into account the latitude, longitude, and elevation of an area to calculate how much sunlight it receives.
Can Google Maps Show Sun Path?
Yes, Google Maps can show sun path. To do so, simply search for a location and then click on the “Satellite” view. From there, you’ll be able to see an overlay of the sun’s current position and path.
Where Does the Sun Hit My House the Most?
Assuming you would like tips on how to maximize solar exposure for your home:
The sun hits my house the most in the morning, around 9 or 10 o’clock. This is when the sun is just starting to peek over the horizon and it’s not too hot yet.
The sun also hits my house in the afternoon, but it’s not as direct and it’s much hotter. I try to avoid being outside during those hours. There are a few things you can do to make sure your home is getting enough sunlight.
First, you can trim any trees or shrubs that are blocking the sun from hitting your house. Second, you can open up your curtains or blinds during the day so that sunlight can come in. And third, you can paint your walls a light color so that they reflect more light.
What Part of My Roof Gets the Most Sun?
If you are looking to install solar panels on your roof, it is important to know which part of your roof gets the most sun. The amount of sunlight that your roof receives will determine how much energy your solar panels can produce.
In the northern hemisphere, the south-facing side of a roof is typically the one that receives the most sun.
This is because the sun is generally in the southern sky during the daytime. If your home has a gable or hip roof, the south-facing slope will likely get more sun than the north-facing slope. However, if your home has a flat roof, both sides may receive an equal amount of sunlight.
To maximize energy production from your solar panels, it is best to install them on a south-facing slope that receives full sun exposure throughout the day. If this is not possible, another option is to install them on a east- or west-facing slope that receives partial sun exposure throughout the day.
How Much Sun Does My House Get?
It’s no secret that the sun is a powerful source of heat and light. But how much sun does your house actually get?
The answer may surprise you. The average house in the United States gets about 2,000 hours of sunlight per year. That means that if you were to spend every waking hour outside, you’d be exposed to the sun for about half of the year.
But of course, we don’t spend all our time outdoors. In fact, most of us spend the majority of our time indoors where we’re shielded from the sun’s rays. So how much sun does your house actually get?
It turns out that it depends on a few factors, including the location of your home, the orientation of your windows, and even the type of glass used in your windows. If you live in a sunny climate, like California or Florida, your house is likely to get more sun than if you live in a more temperate climate like Washington or Oregon. And if your windows face south or west, they’ll probably get more sun than if they face north or east.
Finally, if your windows are made with special “low-e” glass that reflects sunlight away from your home, they’ll also let in less light than regular window glass.


Astronomers have recently carried out further research on a planet called K141-2B to find out about the things and features that take place here, such as a hailstorm, about a kilometer from the sea of lava. It is deep and the wind travels four times faster than the speed of sound. It was discovered in 2018. Astronomer Tu Jian Newgen says that this planet is very interesting because the weather here is severe, mineral rain. It snows. According to Professor Nicholas Cowan, the place is uninhabitable, but there is much to study. Astronomers in India and Canada say it is a rocky planet similar to our Earth.
It is 202 light-years from Earth. What is special is that the planet 141-2B revolves around its star in a few hours, but does not revolve around its orbit like Earth. This means that the planet The two-thirds of which is always in the direction of its star is always there during the day and the temperature there reaches 3000 degrees Celsius. While in some parts it is always night and the temperature there drops to minus 200 degrees. Astronomers say that due to such different weather conditions, it rains here.
As water evaporates on earth, it goes into the atmosphere where its clouds form. Rains refill lakes and rivers and then the same process is repeated. The same thing happens with K2-141B, but there the process is done with rocks.
Researchers say we need to keep in mind that everything on this planet is made of rock. During the day the heat is so great that the rocks evaporate, but on the other hand the cold is so great that there is no air. And everything freezes and becomes solid.
Researchers say that due to the hot and cold sides of the planet, strong winds blow at the speed of sound. And sometimes they reach 5,000 miles per hour. Professor Cowan says that these winds rapidly take the rock vapor to the cool side and begin to form droplets of rock, then rain of rocks and bring down. The sea is formed.
According to Professor Newgen, by researching this new planet, we can learn about the origin of our earth and the lava planets tell us about important parts of planetary evolution. All the rocky planets, including Earth, began as a melting earth. Astronomers will continue to do more research on this in the future.


A Magazine for All Space Enthusiasts
Is print dead? Yes, certain large print publications are struggling. But we aren’t trying to compete with them. Our goal is not to provide a large dividend to shareholders. Our goal is to provide people with space related articles, especially those relevant to the Houston area, that are informative and interesting. This is why we will be able to cover costs even though we are printing less than 1% of the magazines some of these failing but popular magazines print. Plus…It really helps the bottom line when your entire staff are volunteers.
Our organization have a long history of writing on space, more than thirty years in fact for AIAA Houston Horizons. Our online newsletter is already read by thousands of space enthusiasts, engineers, and scientists. See the newsletters.
With a little more push, our reports on what’s new in space and reflections on the past in spaceflight can be spread to even more people around the country and the world!
Is space dead? We don’t think so. The shuttle may have retired but space is very much alive and kicking. Just look at the successful landing of the NASA Curiosity, the success of Space X’s Dragon capsule, Virgin Galactic’s plans to offer suborbital flights for space tourists this year, etc. Initiatives like Mars One and Inspiration Mars is taking people’s imaginations (and realities) even further! For the uninformed, space may seem to be dying but you don’t have to be uninformed. We’re here to inform you, if you’ll support us.
Who is behind this magazine?
The dedicated team of writers of AIAA Houston Horizons who all have studied and are working in aerospace engineering (aka rocket science) include:
Douglas Yazell, Chief Editor
Shen Ge, Writer and Kickstarter Manager
Ellen Gillespie, Editor and Writer
Dr. Steven Everett, Editor and Writer
+ It costs roughly $1500 to print 200 copies of 36 pages, full color, saddle stitched magazine.
+ $250 for kickstarter and amazon fees
+ The rest for prizes and postage to send out the majority of the magazines and letters of thanks


Full Moon (Travel Bug) For Geocaching
Trackable Tag – Unactivated
The moon has always been a celestial object used for navigation and time.
Now you can have your own moon and watch it travel around the world.
All tags are made of aluminum, just like travel bugs, and come with
a chain so that it may be attached to another item.
The Moon Tag measures just under 2″.
Trackable on Geocaching.com


Read full article on original website
It will take days to weeks for astronomers to confirm whether or not NASA's asteroid smasher DART changed the orbit of its target, asteroid Dimorphos.
On Monday (Sept. 26) at 7:14 p.m. EDT (2314 GMT), if all goes well, DART will crash into Dimorphos in an attempt to alter the moonlet's trajectory.
Astronomers are using the James Webb Space Telescope to look back in time. How is this possible? It's just the nature of light, according to NASA.
It's rare for spacecraft mission personnel to cheer at the words "loss of signal," but tonight, that's exactly what happened.
RELATED LOCAL CHANNELS
During a media briefing on Thursday (Sept. 22), the DART mission team said they are confident that the craft will smash into the asteroid Dimorphos as planned on Monday (Sept. 26).
NASA will crash a spacecraft into an asteroid on Sept. 26 and you can watch it through telescopes online for free
The Virtual Telescope Project will attempt to show DART's impact through its network of ground-based telescopes.
NASA's DART spacecraft is no more, but its final view is incredible.
An astronaut's photo of Mount Ruapehu, the real-life "Mount Doom" volcano shows the contrast between the hydrothermal lake at its summit and the snow surrounding its peak.
NASA's DART mission, which will slam into an asteroid on Sept. 26, is not just a planetary defense exercise; it's also an opportunity to learn how binary asteroids form.
This marks a rather auspicious week, for we will see Jupiter loom as large and as bright as it ever can get from our earthly vantage point.
Hurricane Ian made landfall on the Gulf Coast of Florida as a dangerous Category 4 storm, which NASA watched live from orbit as it reached the U.S. mainland.
For NASA's DART spacecraft, the drama happens in space, but mission success relies on telescopes back on Earth.
IN THIS ARTICLE
A Falcon 9 rocket launched 52 of SpaceX's Starlink internet satellites to orbit Saturday evening (Sept. 24) and also aced a landing at sea.
DART may have completed its journey, but the work is only just starting for scientists as they set about learning how much the asteroid Dimorphos was deflected by its impact.
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NASA will slam the DART spacecraft into an asteroid for target practice to get ready for the next big hit, but don't worry: nothing big is set to come at us for the next 100 years.
The iconic 20-sided Dungeons and Dragons die soared close to the 'Astral Plane' to advertise a new space campaign for the role-playing game.
Telescopes here on Earth captured the DART asteroid probe's spectacular deep-space death.
DART truly made a mess last night.


Full Rose Moon & Penumbral Lunar Eclipse Blessings. In a tight square with Mars, God of War and Revolution, this Full Moon Eclipse, also happening during the Inferior Conjunction of Venus with the Sun King, is calling forth our inner Warrior to tear down any barriers to Love and Unity, both within ourselves and in society.
For Resources on ‘Un-doing Racism’, please see Heather’s Resource page on her website, which she is updating regularly.
May these revolutionary energies serve the change that we all need to be.
With my love & blessings from Avalon
Annabel Du Boulay ?♥?
Photo by Yuzuru Gima / Getty Images


Welcome, celestial voyagers, to the cosmic dance of July 2023! This month, the stars have choreographed a celestial ballet that will guide us through lessons of responsibility, renewal, and reflection. So, fasten your cosmic seatbelts, and let’s embark on this astral journey together!
Full Moon in Capricorn: Embrace Your Responsibilities (July 3rd)
As the Full Moon bathes the sign of Capricorn in its silvery glow, we are reminded of our commitments to the world beyond our doorstep. This is not a time for shying away from responsibilities. Instead, it’s a cosmic call to action, urging us to step up, act maturely, and take charge. Remember, dear stargazers; the universe rewards those who are not afraid to roll up their sleeves and get their hands dirty. So, let’s embrace our duties with grace and determination!
New Moon in Cancer: Nurture Your Foundations (July 17th)
Mid-month, the New Moon nestles into the comforting arms of Cancer, prompting us to turn our gaze inward. This lunar event is a gentle reminder to nourish our personal lives, our homes, and our families. It’s a time to feed our foundations, both the physical ones we live in and the emotional ones we carry within us. Remember, the strength of a tree lies in its roots. Similarly, our strength lies in the love and security we derive from our personal circle of friends and family.
True North Node Enters Aries: Cultivate Independence (July 17th)
On the same day, the True North Node strides confidently into Aries, encouraging us to cultivate independence. This celestial shift is a cosmic nudge to address co-dependency issues and indecision. It’s a period of learning to love ourselves, trust our instincts, and lead without fear. Remember, the journey to self-love is the most rewarding journey of all. So, let’s embark on this path of self-discovery and empowerment!
Jupiter Semi-Square Neptune: Beware of Illusions (July 22nd)
As Jupiter forms a semi-square with Neptune, a thread of idealism weaves its way into our lives. While hope is a beautiful thing, this astral event warns us against unrealistic or inflated expectations. Beware of illusions, dear stargazers, for they can lead us astray. Remember, the universe encourages us to dream, but it also teaches us the importance of grounding our dreams in reality.
Venus Retrograde in Leo: Reflect on Relationships (July 22nd)
Venus, the planet of love and beauty, begins its retrograde dance in the flamboyant sign of Leo. This celestial backspin offers us a chance to review our affections, relationships, and finances. It’s a time for introspection, for looking back before moving forward. Remember, sometimes, the universe asks us to pause and reflect so that we can make better decisions in the future.
Chiron Retrograde: Heal from Within (July 23rd)
Finally, as Chiron, the wounded healer, turns retrograde, we are encouraged to reassess the mental and physical health programs in our lives. This is a time for introspection and healing. Remember, healing is not a destination but a journey. So, let’s embark on this healing journey with courage and compassion.
So, dear voyagers, are you ready to dance to the cosmic tunes of July 2023? Remember, the universe is always guiding us, teaching us, and helping us grow. Let’s embrace these celestial lessons with open hearts and open minds. Here’s to a month of responsibility, renewal, and reflection!


Disappointingly, scientists say they've been able to establish where the methane on Mars comes from - and it's not from living organisms.
British scientists say they've established a link between the sun's 11-year cycle and cold winters in Northern Europe and parts of America.
The bulky Polaroid camera - like bell bottom jeans and leg warmers - has (thankfully) been relegated to the trash heap of embarrassing fashion faux pas.
Scientists have created organic macromolecules by zapping a Titan-like atmosphere with UV rays. The discovery supports the idea that the moon of Saturn could support life.


Sunday, August 15, 2021 16:30 PM (GMT+7)
While the faces of Nasa’s Mercury Seven astronauts flooded the global press, the Russian cosmonauts trained in secrecy, unbeknownst to the public.
The first group of potential astronauts is reduced to just 20, including Yuri Gagarin, second from left.
On April 13, 1961, special correspondent Georgi Ostroumov of the Soviet newspaper Izvestia met the first man in space. The day after returning to Earth, “space pilot” Yuri Gagarin was, in Ostroumov’s account, “excited, healthy, and fit… a wonderful smile spread across his face. “
“Sometimes dimples appear on his cheeks,” Ostroumov wrote. “He appreciated everyone’s curiosity when he asked in detail about what he saw and experienced during the hour and a half he spent on Earth.”
In the pamphlet published to commemorate the flight, “Soviets in Space”, the interview with Gagarin spanned several pages.
The astronaut described the experience: “The horizon is unusually beautiful and extremely unique.” He also praised the Soviet Union: “I dedicate my journey to… all of our people who marched to the front lines of humanity and built a new society.”
In a political system where the press tends to propagate rather than portray facts, it is easy to assume that Gagarin’s words are fabricated. But while they may have been tweaked by the censors, it’s likely they’re still the cosmonaut’s true words.
A fighter pilot who grew up in a small Russian village, Gagarin is a beloved family man. Indeed, he is handsome, charming and especially has a party card, showing his loyalty to the communist party.
While the dramatics of the early stages of Nasa’s manned space program were well known to the public, it was not until recently that the full story of how the Soviets recruited and trained their cosmonauts became known. known.
After qualifying as a fighter pilot, Gagarin was assigned to a remote airfield near the border with Norway, and flew MiG-15s on the Western Front during the War. Cold.
At the end of the summer of 1959, two doctors arrived at the airbase, conducting interviews to pre-select a group of pilots.
After starting with a list of about 3,500 potential candidates, the doctors narrowed their search to about 300 pilots across western Russia.
“The interviewees had no idea why they were being interviewed,” said Stephen Walker, author of “Beyond”[Ngoại vi], spent years rummaging through Russian archives to piece together the full story of Gagarin’s mission.
The interview has quite intimate content such as asking about career, aspirations and family. Some people were invited to come back for a second interview. Although the doctors revealed that they were looking for candidates for a new flying device, they never revealed their true intentions.
“They’re looking for military pilots who accept the possibility that they’re willing to die for their country, which is really what you have to deal with, because the odds of coming back alive aren’t necessarily high,” Walker said.
While Nasa recruited military test pilots to serve as cosmonauts for the first time flying in the Mercury complex spacecraft, the Soviet Vostok’s cockpit was designed with remote control from the ground. Except in the event of an emergency, the pilot doesn’t do much to operate the flight.
“They’re not looking for people with that much experience,” Walker said. “What they were looking for was simply a human version of a dog – someone who could sit there and endure the mission, respond to the acceleration, and come back safely.”
And just like the cosmonaut dogs that Russian rocket scientists launched into space more than a decade ago, astronauts must be physically fit, obedient, and small enough to fit in the capsule. narrow driving.
In the end, 134 people selected – all young pilots, less than 1m68 tall – were given the opportunity to “volunteer” for a new and extremely secret mission.
Some were told the mission was to train to fly the spacecraft, others believed it was a new version of the helicopter.
None of the pilots were allowed to discuss work with colleagues or consult with family.
Meanwhile, in April 1959, the United States announced the names of the first seven astronauts to fly Mercury. Candidates must undergo a series of grueling physical exercises, medical and psychological tests – all written in the book by Tom Wolfe (followed by a movie and TV series). ) called The Right Stuff.
When asked during the press conference which exercise they disliked the most, astronaut John Glenn said: “It’s very difficult to choose which exercise to watch because if you find out how many holes, holes in the human body. and how deep you can go in each of those holes or niches… then tell me, which hole makes you most hesitant to go in.”
But with many questions remaining about how humans can adapt to the extremes of space flight – such as acceleration, zero gravity and solitude – the rationale is imperative. considered when choosing a person, that is the person chosen must have the best physical and most stable mentality.
The person in charge of the examination of candidates for the post of Soviet cosmonauts was Vladimir Yazdovsky, professor at the Moscow Academy of Aviation and Space Medicine.
Before that, he was the supervisor of the program to send astronaut dogs into space. Colleagues describe (in private) that he is arrogant and harsh.
“He’s kind of like a horrible James Bond character,” Walker said, “and he’s incredibly cruel to these people.”
In most cases, the Soviet exercise was longer, more difficult, and more intense than that of the American cosmonauts.
Within a month, the candidates had to experience pressure in holes and holes in their bodies, endurance tests in every part of their bodies, and being provoked to become easily agitated.
They were put in a room with a temperature as high as 70 degrees Celsius, or the room was gradually depleted of oxygen and forced to sit in a chair that caused the shaking simulation like when launching a ship. Some candidates fall, others give up.
This extremely austere training program places less emphasis on ship piloting skills than Nasa
During the process, attendees were prohibited from telling family and friends what they were up to. Even in the month of admission, some people still don’t know what they’re applying for.
In the end 20 of those young people passed their training at an astronaut training center.
This place was later renamed Star City, but at first it was just a place of a few military tents in a forest near Moscow.
No one held a press conference or announced anything. Officially, the Soviet spaceflight program did not exist on paper.
“If they leave the base, they’re told not to tell anyone what they’re doing, why they’re there, if someone asks, they’ll say they’re part of the athletic training team,” Walker described. . “Everything is controlled, everything is secret. Everything is hidden behind closed doors.”
The training program itself is similar to the US program, but has less content related to spacecraft control.
Like astronaut dogs, these people were rotated at increasing speeds on a centrifugal rotator, locked in a sealed, soundproofed cockpit for several days and subjected to constant physical and mental health checks. .
Another typical difference from the US space program is the amount of skydiving training that Russian cosmonauts have to do. That’s because they needed to escape the spacecraft during a rapid fall to the ground to avoid serious injury from the impact. The fact that the cabin and pilot would land separately is another secret that was not revealed until many years later.
With more and more people falling, the first group of six astronauts was selected for the first flight.
When Nasa publicly announced its hope to launch people into space for the first time in 1961, Soviet space program leader Sergei Korolev knew he had a chance in a limited amount of time.
Russian cosmonauts go through the same journey as many American cosmonauts, for example training in zero gravity.
On April 5, 1961, the astronauts arrived at the so-called Baikonur spacecraft launch site in the Kazakh desert, where Korolev’s massive R7 rocket was ready.
Until then, still none of them know who will be the first to fly into space. Finally, just days before the launch, Gagarin was allowed to fly.
Until it was officially announced that Gagarin was in Earth’s orbit, no one but those closest to the space program knew his name.
According to Ostroumov, a special correspondent for the Izvestia newspaper, on the morning of April 12, Gagarin “wagged for the last time to friends and comrades below. [tên lửa] when he entered the spaceship, a few seconds later the command was given… the giant ship rose from the fiery cloud to the stars.”
He returns to Earth and becomes the Soviet son that pops up all over the posters – Russian-style astronaut.
There are a number of places in the world that make everyone curious, because they are considered “top secret” and very few people have…


Mr Mark LintonPosition: PhD StudentE-mail: mark.linton(at port.ac.uk)
Telephone: +44 (0)2392 845165Office: DS2.05
Research interests: Interacting dark energy, The cosmological constant problem, Modified gravity.
I am a third year PhD student working with Dr Alkistis Pourtsidou and Prof Robert Crittenden. I am currently working on models of interacting dark energy with the aim of using recent cosmological data to examine which of these models best describe our Universe.
I completed a Theoretical Physics masters degree (MPhys) at the University of Sussex, graduating in 2015. My research here involved exploring how AdS/CFT holography could be used to model high temperature superconductors, I was supervised by Dr Veronica Sanz.Qualifications: MPhys University of Sussex, MSc University of Sussex
Publications from UKADS
Publications from INSPIRE
Publications from arXiv
Publications from the UoP Research Portal
External talks (academic)
External talks (outreach)


Watch: NASA astronauts perform spacewalk outside ISS
On Sunday, December 22, 2013, NASA astronaut Mike Hopkins tweeted on Saturday’s spacewalk, saying, “Wow… can’t believe that is me yesterday. Wish I could find the words to describe the experience, truly amazing.” Expedition 38 Flight Engineers Rick Mastracchio and Mike Hopkins wrapped up a 5-hour, 28-minute spacewalk outside the International Space Station completing the first in a series of excursions aimed at replacing a degraded ammonia pump module associated with one of the station’s two external cooling loops that […]
Posted at 7:51 AM, Mar 29, 2018
and last updated2018-03-29 13:03:09-04
HOUSTON – Two NASA astronauts performed a spacewalk Thursday outside the International Space Station.
NASA says Expedition 55 flight engineers Andrew Feustel and Ricky Arnold planned to install two new handrails with built-in wireless communications equipment, replace a malfunctioning camera, and remove a set of hoses from the ISS’s cooling system.
Fuestel and Arnold arrived at the ISS on March 23 after launching to the station on March 21 on board a Soyuz MS-08 spacecraft with Russian cosmonaut Oleg Artemyev.
According to Space.com, this is Fuestel’s 7th spacewalk and Arnold’s 3rd. It’s the 100th spacewalk overall by Expedition crew members and the 209th overall in support of ISS assembly and maintenance.


To go along with the rover tracking feature in MMB2.0, there will soon be a "Rover Model" feature, where you can move a 3D model of the rover along the rover's actual path to see what it looks like in relation to the surroundings. UnmannedSpaceflight.com maestro Doug Ellison created the 3D rover model that MMB will use. Check it out an early version in these QuickTime movies:
Opportunity Sol 1061-1066 w/model
Spirit Summit movie
And there are some screenshots here.