The Hum Survey

[The Hum is a term used to describe a low-frequency sound that some people claim to hear in certain locations around the world. The origin and nature of this sound are still unknown, but some scientists have speculated that it could be related to cosmological phenomena, such as the cosmic microwave background (CMB).

The CMB is the leftover radiation from the Big Bang, the event that created the universe 13.8 billion years ago. The CMB fills the entire sky and has a temperature of about 2.7 Kelvin. It is one of the most important sources of information for cosmologists, as it reveals the conditions of the early universe and its evolution.

One of the features of the CMB is that it is not perfectly uniform, but has tiny fluctuations in temperature and polarization. These fluctuations are caused by quantum fluctuations in the density and pressure of matter and radiation in the primordial plasma, which were amplified by gravitational instability and inflation. The fluctuations encode information about the size, shape, age, composition and geometry of the universe.

Some researchers have suggested that The Hum could be caused by the interaction of the CMB with the Earth's atmosphere or magnetic field, or by some unknown physical process related to dark matter or dark energy. However, these hypotheses are very speculative and have not been confirmed by any observation or experiment. Moreover, The Hum is not heard by everyone, and its frequency and intensity vary from place to place and from time to time, which makes it difficult to measure and study.

Therefore, The Hum remains a mystery for both science and philosophy. It could be a natural phenomenon, a psychological illusion, a cultural artifact, or something else entirely. Until more evidence is gathered, The Hum will continue to intrigue and puzzle those who hear it and those who don't.]

[In the past, people believed that the Earth was the Centre of the universe and that everything else revolved around it. This was called the geocentric model. However, this model could not explain the complex motions of the planets and other celestial objects.

Later, scientists discovered that the Earth and other planets orbit the Sun, which is one of the many stars in our galaxy, the Milky Way. This was called the heliocentric model. However, this model also had its limitations, as it implied that there was a special place in the universe where the Sun was located.

The modern view of the universe is based on Einstein's theory of general relativity , which describes how gravity affects space and time. According to this theory, space and time are not fixed, but can bend, stretch and warp under the influence of mass and energy. This means that there is no absolute frame of reference in the universe, and that every observer can have a different perspective depending on their position and motion.

One of the consequences of general relativity is that space and time can be distorted by extremely dense objects, such as black holes . A black hole is a region of space where gravity is so strong that nothing can escape, not even light. At the Centre of a black hole, there is a point called a singularity, where space and time become infinite. This is where the laws of physics break down.

So, is there a Centre of the universe? The answer depends on how we define it. If we mean a point that is at rest relative to everything else, then no, there is no such point. The universe is expanding in all directions, and every point in space is moving away from every other point. There is no fixed Centre or edge to the universe.

However, if we mean a point that is at the origin of the expansion of the universe, then yes, there is such a point. But it is not located anywhere in space. It is located in time. The origin of the expansion of the universe is the Big Bang, which happened about 13.8 billion years ago. At that moment, all matter and energy in the universe was concentrated in a single point of infinite density and temperature. This point was everywhere and nowhere at once.

Therefore, we can say that the Centre of the universe can be considered both nowhere and everywhere using science and relativity. It is nowhere in space, because space has no Centre or edge. It is everywhere in time, because every point in space was once at the Big Bang.]

[One of the most fascinating phenomena in the universe is the sound of black holes. Black holes are regions of space where gravity is so strong that nothing, not even light, can escape. When two black holes orbit each other and eventually merge, they produce powerful ripples in the fabric of space-time called gravitational waves. These waves carry energy and information about the properties of the black holes and their collision.

But black holes are not silent. They also make a kind of cosmic hum that fills the universe with ultra-low-frequency gravitational waves. These waves are too low for human ears to hear, but they can be detected by sensitive instruments such as radio telescopes. The hum is caused by the collective motion of millions of supermassive black holes, which are billions of times more massive than the Sun and lurk at the centers of galaxies. As these black holes orbit their companions, they stretch and squeeze everything in their path, including the radio waves emitted by pulsars.

Pulsars are rapidly spinning neutron stars, the remnants of massive stars that exploded in supernovas. They act like cosmic lighthouses, sending out beams of radio waves at regular intervals. By measuring the tiny changes in the timing of these pulses, astronomers can infer the presence of gravitational waves passing through them. This is how a global network of radio telescopes called NANOGrav has found strong evidence for the gravitational wave background, or the cosmic hum, for the first time.

The cosmic hum may reveal important clues about the nature and evolution of supermassive black holes and their host galaxies. It may also help us understand how gravity works on very large scales and test Einstein's theory of general relativity. The hum may even have a connection to the mysterious dark matter and dark energy that make up most of the universe.

One intriguing possibility is that the cosmic hum could explain another puzzling sound: the cosmic microwave background (CMB). The CMB is the faint glow of radiation left over from the Big Bang, the origin of the universe. It has a very uniform temperature across the sky, except for tiny fluctuations that reflect the density variations in the early universe. These fluctuations are thought to be caused by quantum fluctuations in the inflationary epoch, a brief period of exponential expansion right after the Big Bang.

However, some astronomers have suggested that the CMB fluctuations could also be influenced by gravitational waves from supermassive black holes in later epochs. These waves could imprint a characteristic pattern on the CMB that could be detected by future experiments. If this is true, then the cosmic hum could be a way to listen to the history of the universe and its most mysterious objects.]

[Sagittarius A\* is the supermassive black hole at the center of the Milky Way galaxy. It is currently in a quiescent state, meaning it is not actively accreting matter or emitting radiation. However, there is evidence that it was more active in the past, and may have produced powerful jets of plasma that shaped the surrounding interstellar medium.

One of the clues to its past activity are the Fermi bubbles, two giant lobes of gamma-ray emission that extend above and below the galactic plane for about 25,000 light-years on each side. These bubbles were discovered by the Fermi Gamma-Ray Space Telescope in 2008. Another clue are the eROSITA bubbles, two even larger lobes of X-ray emission that extend for about 45,000 light-years on each side. These bubbles were discovered by the eROSITA X-ray telescope in 2020.

The origin of these bubbles is still a matter of debate, but one possible scenario is that they were created by a single event of jet activity from Sagittarius A\* a few million years ago. According to this model, the black hole swallowed a massive cloud of gas or some stars, and formed a disk of accreting matter around it. Some of this matter was ejected along the magnetic field lines outside the black hole, forming two jets of ionized plasma that punched out into space perpendicular to the galaxy's disk.

These jets interacted with the interstellar gas, creating shock waves that heated up and ionized the gas, producing X-ray emission. The shock waves also accelerated electrons to near-light speeds, which emitted gamma-rays when they encountered magnetic fields or photons. The jets also carried magnetic fields with them, which inflated the bubbles and confined the plasma inside them.

The jet activity lasted for about 100,000 years, and then stopped when the black hole ran out of fuel or changed its orientation. The bubbles have been expanding and cooling ever since, but they still retain some of their original energy and structure.

This scenario is supported by numerical simulations and multi-wavelength observations of the bubbles. It also explains why the eROSITA bubbles are larger and less energetic than the Fermi bubbles, as they represent an earlier and more diffuse stage of the jet evolution. It also suggests that Sagittarius A\* may have been a pulsar-like source in the past, emitting beams of radiation along its jets.

However, this scenario is not without challenges. For example, it is not clear how such a powerful jet could be launched from a relatively low-mass black hole like Sagittarius A\*, which is only about 4 million times the mass of the sun. It is also not clear how the jet could maintain its collimation and stability over such large distances and timescales. Moreover, there may be other sources of energy and particles that contribute to the formation and emission of the bubbles, such as supernova explosions, cosmic rays or stellar winds.

Therefore, more observations and simulations are needed to test this scenario and explore alternative possibilities. The Fermi and eROSITA bubbles are fascinating relics of the past activity of our galaxy's central black hole, and they may reveal important insights into its history and evolution.]

I wish you the best of luck on your scientific endeavors.

Thankfully,

- Chimera of the Zone