welcome to the science for the public lecture series science for the public is an organization committed to bringing science information and issues to the general public visit our website for our program library for hosting this lecture series setting it up for us and her great help with these events tonight the subject is the dark age of the universe and our speaker is dr lincoln greenhill senior research fellow at the department of astronomy harvard university and radio astronomer at the smithsonian astrophysical observatory dr greenhill received his ph d in astronomy from harvard in  ninety and he's been served as a post doctoral fellow at the miller institute for basic research in science and as a university of california berkeley senior research fellow and then as a radio astronomy back here at the smithsonian astrophysical observatory in two thousand and seven he joined the harvard department of astronomy and as a senior research fellow and he has since that time has miller institute for basic research in science at berkeley and what he will focus on tonight the longwave or a and i'll let him explain that to you d hills focus in astronomy is on the dark age of the universe a very exotic little era and that is his topic tonight non related phenomena including i think the period called the and on super massive black holes and star formation all of this sort of coming together he actually does more than all of this but we'll keep it brief so that we can have plenty of time to hear him and to see the wonderful quit that he has brought with him tonight including this antenna it is a great pleasure to welcome dr lincoln green hell so thank you very much for the opportunity to speak to speak here so the talk will be in the center in real time on a feed from new mexico provided the wife i holds out we're going to have running on the left side normally i don't do this because it's distracting but running on the left side these are real time images of the sky in new mexico the radio sky and the radio skies dominated not by things like sun and stars it's in this case it's dominated by well you can see off to the left where it says very a that's a super massive black hole in the galaxy called m eighty seven and for radio a and you can also see the glass the plain and occasionally the display looks like that which is manmade interference which is coming into the antennas and these are the types of antennas that we're using so i'll refer back to that but this is a real time image of the sky every instant it covers horizon to horizon and that's something that we can't do with optical telescopes readily it's something that is particular to radio so let me let me go back to the circa two thousand and six and it's essentially showing the history of time today is here this is as you'll see this this is the modern universe it's full of galaxies it's dark in between the galaxies and this is the big bang and then we have a bunch of blank pages and the notion here they were communicating is there's a lot that we don't know during a critical early period in the universe of about a billion years we have lots of theory that tells us how the first galaxies formed the first stars when they formed but we haven't been able to look back far enough to actually say with certainty which theories are right which theories are wrong we're just beginning to get the first census of you know maybe only tens of galaxies maybe one hundred galaxies which are in this opening chapter so what i'll be discussing and and as yvonne mentioned the long wavelength the re and i'll bring in the name of the project that i work on we're attempting to find new ways to collect data that will take us back that far and that's good so the important thing is that galaxies that we see today pictured at the bottom are not the galaxy are not what those galaxies looked like at the beginning of the universe say of order thirteen billion years ago and this is along the lines of a backward progression of how galaxies appeared so they're large they're lustrous they're you know largely they're largely comprised of stars spiral galaxies the stars organized into a spiral arms for this type of galaxy they're also a loop to go galaxies which are just blobs of stars but then is you go back in time they get smaller the amount of gas in the galaxy doesn't necessarily change but the number of stars that have formed up to that point becomes smaller and smaller so that's why over here you see the galaxies a much smaller they're also redder and that's actually because as we refer to that in astronomy is redshift as you go further back in time or to greater distance thing the light is shifted to the re so this is actually just a useful trick and reminder so still the universe is almost fourteen billion years old we're only halfway back and so the question is well what if things look like if you go even further back and this is a beautiful picture taken with the hubble space telescope that shows a cluster of galaxies that you may be able to make out apart from the bright spots you know here is a galaxy seen face on you can probably make out the  the dust here's a galaxy that is that is edge on and this is in the foreground this is my maybe about five billion years old that is five if you go back in time about five billion years had to that equivalent distance you come up to this cluster and then behind it is what shown off on the left these these are images of something that was even further back something that was at about thirteen point two billion years so it almost just a few percent of the age and it's not terribly it's not terribly large which is the important thing large meaning it's probably a few tens of times smaller than our own galaxy or it's a few tens of times smaller than a galaxy in the modern era so things were smaller there have been less there have been fewer stars galaxies are smaller they were to get the gas just had not yet formed into into stars so the universe back then so this is about the limit of what we can see at this point using optical telescopes that are available to us now whether it's hubble things on the ground once we try to go beyond this to say the first percent or less than a percent of the age of the universe we're we're stuck we just don't have the tools right now to to do that so you know i'm going the wrong direction so let me now use a cartoon to tell you what we think based on theory occurred during that period of time so today is on the right and you can see the artist's conception of dark skies with get peppered with galaxies the big bang being an amorphous blob of energy on the left and so we're at fourteen giga years this is about ten gig years just using a ruler so at about one billion years after the formation after the big bang the universe changed abruptly and let's let me walk what i did in the previous slide was i walked back across this right hand third to a period when the galaxies were looking noticeably different and they were smaller they were less less developed but then once you go beyond that this is terra incognit and what this is intending to show now starting from the left after the big bang there were no stars the universe was just a sea of hydrogen and helium gas that is to say there was an intensely hot plasma after the big bang things cooled down and matter formed that is neutral gas formed hydrogen and helium but again they were this is going to be my own doing but there are no stars by definition over time gravity drew the gas together eventually stars formed and what you have here now say in the center are what looks like soap bubbles and that's trying to indicate that the stars formed they began to in pockets and there was intense ultraviolet radiation which destroyed the hydrogen around and so the universe goes from being a solid brick of cheese to being swiss cheese to being increasingly so it's cheese until eventually all of the neutral gas has been destroyed by ultraviolet or collected into galaxies as they are leaving this adolescent stage early on and then at a certain point again all of that medium all of the cheese is eaten away and you end up with something that looks rather familiar so just going to know stars only hydrogen helium to small pockets of stars possibly what we have optical images of in the previous slide to real galaxies that is things that would have say spiral arms and and lots of stars but still adolescent to today's modern galaxy so the question though is what if there are no stars how do we study this time period at the beginning and then the answer is i think the shortest one i could possibly manufacture it's this is just letter h for hydrogen look at the hydrogen don't try to look for bright spots just look for all that the few stuff that is around so by studying this diffuse material specifically measuring its temperature we can learn something about what's going on in the universe called gas we would mean that there's there are no stars to heat it for example so what are some of the important questions when did those first stars form and were they like the sun were they like any of the most massive stars that we have in our galaxy or were they completely different we think that they would be that they were completely different black holes and stellar remnants stars massive ours explode toward the end of their lives and they give birth to among other things black holes so that means the early universe began to build up a supply of quote unquote supply of black holes but  know that in the centers of galaxies we have super massive black holes that could be a billion solar masses or more and yet star that's exploding might give you a black hole of ten one hundred we don't know so how do you get from ten or one hundred to billion there must have been some sort of merger process we don't understand that but we do know that we see the evidence of super massive black holes at the end of this billion years so how is it you can build something in a billion years which is enormous especially since you have to start from scratch and then the last issue is somewhat exotic that is our black holes our supernova our stars the only ways that you can heat gas or was there evidence of something else so if we look at hydrogen if we use it as a thermometer if we look back to the beginning of time so to speak and we find out that the gas is hotter than theory tells us it should be we need an explanation and that's that's what this question's angling on so  a radio stratum or in the angle that i have when i don't necessarily have stars to to look for is going to be a study of a gas as i said use its temperature which is one of the easier things that one might detect though by no means terribly easy and then test hypotheses so so hydrogen thermometer use that as a term for for this talk and this plot shows the big bang is now on the right it was on the left and this is going to jump from left to right depending upon where i stole the figures from i apologize but again this is a plot that shows temperature on the y axis and redshift on the x a redshift is not necessarily easy to calibrate quantitatively outside astronomy so that's why i simply say that now is here the big bang is here and you can see the temperature drops as you go from then to now so it's dropping because the universe was gradually expanding this is just state this is at the same time as radiation which would be the cosmic microwave background of the cosmic background radiation left over from the big bang as the universe expanded it cooled off the equivalent temperature of that radiation cooled off and at the same time the gas in the universe cooled off but the physics is that they cooled off at different rates so that means that there are two temperature reservoirs in the early universe and the hydrogen gas you would think is just cooling off at this temperature but at this rate but what i'm referring there to when i say that it's the kinetic temperature it's you know the a banging against one another for instance or how fast the atoms are moving you know a hot air room full of hot air is full of has a has a speed of oxygen and nitrogen molecules that is much faster than if you say at that same room in antarctica so this is all a matter of the kinetic temperature of the gas but that's not the only way to measure temperature that's all i'll show some examples in the coming slides and it's those other measures of temperature where we're not just bending in we're not just interested in how fast the atoms are but moving but we're interested in for instance what the electrons are doing they have a temperature as well so that after the big bang just to summarize there is something called global reconfirmation that's when the plasma which is left over from the big bang collapsed it cooled enough i should say collapse of the electrons in the protons found each other they made hydrogen or the and found their electrons and made helium gas that that was referred to as recombination that occurred just a few hundred thousand years after the big bang what happened between then and a billion years after the big bang well theoretically the universe coasted for a lot of that time as i was saying until finally gravity drove things to collapse and form stars and at that point everything changed the it was not a universe regulated by just coasting it was the universe it suddenly had all of this input  energy and explosions and things like that as well i'll show an example in this computer simulation so i just want to point out this is point eight billion years so this is more or less this thread and fabric of places where stars have formed and are beginning to form galaxies it's moving a little quickly so i'm going to accelerate what you what you're seeing is in the blue and it's dark matter and all returned to dark matter later because of the speed of this but what you can see are these clusters of material are gradually getting larger and larger because gravity is pulling material together to form early galaxies so for instance where it's pink in the middle that's actually a place where there's something very massive and now you see green and red and you can see flashing for instance here and explosions this is these are the by products of galaxy formation stars form remnants formed black holes form supernova and you start to drive material out of these early galaxies so what so basically this is a demonstration that we go from a very passive universe to something that is quite extraordinary the extravagant too to quote a colleague's book's title so here again we have explosions are coming about because there are super massive black holes in the centers and they are impulsively throwing material out and what we have in the end is going to be our much more quiescent universe at about in and about this time we had the peak in the history of the universe of activity from these objects like a super massive black holes and from that point on we have a fairly diffuse medium which is surrounding which is part of these galaxy clusters we have material that is connecting galaxy clusters you saw these wisps early on anyway now this is a simulation so we take the physics we know and colleagues in the illustrious collaboration have generated our best understanding of how those mechanisms come together to give us what we see but the problem is that early on we don't have enough we don't have data work strap elating theory back and we're making our best guesses and coming up with a policies which need to be tested so again this is this is today in the context of we have clusters of galaxies all these bright spots but that came from an earlier era when the galaxies were forming and things were not the first super massive black holes in those regions were puffing out enormous amounts of material a relativistic speeds and before that we were strapped leading into what we refer to as the dark age so sensing temperature i had mentioned before well you can look at kinetic temperature as you know i'm  feeling that because i'm wearing this jacket and it's warm in the room that's because of things banging into one another but they're also and so that shown for instance here if i have a source of light that's generating a spectrum and then i put something cold in front of it and this is made of uses a gimmick hydrogen hydrogen has a characteristic frequency for frequencies for lines i mean for some of the electron transition so when it's cold it paints a dark line on that spectrum the light goes through it it's absorbed take away the light source and instead perhaps the warmth of that cloud is enough to excite that single frequency which would be characteristic of hydrogen hydrogen actually as many frequencies but but for this example i used this one so another way to to assess the temperature is just to look at whether there are excited electrons so i'll simplify this in the context of previously i showed a spectrum and i shown i took a light source centered through a cloud and most of most of the light just passed through there was no problem but occasionally you hit light when you get light at a certain frequency and it hits an electron which all  o loosely it hits a resonant frequency and the electron is it absorbs the energy that's how we got the dark line for instance but equally well if i have an electron which is in excel in an excited state and i don't have any light source behind it it may just drop back to the blue state might become the red state and it would emit light which is as we have here so energy conditions in the atom that a temperature is something that is  a temperature is is what you would use to characterize for instance well how many of these atoms are in this excited state how many are in this an excited resting state so let me go further so i mentioned things banging into one another well it's not just balls you can also be as this adam hits this out i'm it can actually have other effects it can knock off electrons leaving one pair atom it could you could send an electron hurdling at high speed very hot electron in to an atom same thing would happen so this is another form of or this is another ramification of temperature and that ultimately i'm building to this notion that what we're looking for is not just the what we're not just looking at the kinetic temperature or looking at a specific temperature of hydrogen one of the several which is something that we can measure with as radio astronomers since we don't have a spectrum  with a light source that we shining through so what we're looking at is if this is just a simplified hydrogen atom we have a proton we have an electron and electrons have spin and they carry angular momentum with them sometimes that spins aligned with the spin of the proton or sometimes it's anti aligned and the amount of energy is different depending upon which which state you're in so when the electron flips from being aligned to empty aligned it gives off a little bit of radiation that's the thing that we're going to detect which means what we're able to study is what we're going to be sensing is the temperature which we call the spin temperature how many atoms essentially how many a have two things are aligned versus two that are anti aligned and we understand that as that these other processes as atoms are banging into one another as radiation is passing through and interacting that changes the populations that are aligned and the populations are in to be aligned so we're not looking at say the temperature of the universe which at the time may have been one hundred degrees on the kelvin scale or you know minus minus almost two hundred degrees and celsius what we're looking for is a very particular type of temperature but nonetheless something that we can calculate nothing that we could ever feel as as people so this is f i'm going to ignore the fact that this is on the slope and just try to level it out so i can display it nicely left or right and what i have here this week only aligned is this alternate measure of temperature which is just how many atoms are like this and how many are like this and early on the temperature you see begins to fall and that corresponds to all these hydrogen atoms are losing temperature because the universe is gradually expanding and the matter is cooling that at its own rate at a certain point though the banging together of atoms just takes too long that is the universe becomes so rarified that this hydrogen it actually comes into an equilibrium with the radiation temperature i i will not not explain that in detail at the moment it's just a matter though to remember there are two reservoirs of temperature in the universe the temperature the spin temperature will be one or the other when the collisions become so rare you can't keep this temperature sync with the kinetic temperature it just drifts off to the temperature of the radiation however then something happens at about this point which is about one hundred million years after the big bang and this corresponds to in the first stars form or this occurs because of light from those first stars so this is labelled the dark age  the the universe is expanding it the hydrogen gas cools and temperature eventual lead that temperature with the kinetic temperature and the spin temperature no longer the same radio astronomy is because we're just looking at the this one particular transition which is created where the radiation is created when electrons go from this alignment to this alignment we are specifically looking for we are specifically studying when this transition i a measurement of temperature that corresponds to either the banging around of atoms or the background radiation so it's going to vary and all over the place to say and some and there is some advance that occur when  some advance occurred that change radically this is one of them when the first stars form this is another when those stars form in such great numbers that the swiss cheese begins to be more air than than she's so  i'd like to focus on what would we've been doing we have an experiment called the large aperture experiment to detect the dark age which is a rather strange acronym since we had to drop two words in order to make it work however we have we have a couple websites so twenty one centimeter cosmology or more usefully maybe cosmic dark age dot org so our experiment is sighted in california with another location in new mexico and that's why over here we are beaming pictures from new mexico our colleagues at the long wavelength the ray project  observing actively with with other science programs and this is coming live from them so let me know when this is on the nevada border it's just somewhat south of lake tahoe on par with san francisco and there's a long valley here that leads off the mojave desert which is down here so i'll be zooming in on that that location and the closest town is big pine mt whitney is in this vicinity so the highest mountain in the contiguous forty eight and now on this says zurich i don't know if you can read it in the early twentieth century there was actually a railroad running in this area and that was referred to as zurich station that google thinks that zurich is still there i find pretty amazing now i think it died in the one nine hundred forty s and any case i'm focused on on this here is the owens river which is one of the sources of water for los angeles and now i get to something that begins to look like nascar lines or crop circles so this is it is an arid very desert like environment despite the river and what you can see here is the ground disturbance that was created when we build when we and our colleagues at cal tech for whom this is this is the property started building a second long wavelength or a station that is a sister to this one and you can see a circle in the middle and then you can see some lines that go to a few antennas that are off off to off to the side and here we have some rather traditional radio antennas they look like to circles but these are like they look like giant tracking dish satellite tracking dishes but used to radio astronomy so now going going in a bit further you can begin to see well you can see what the brush looks like these black spots and then in here you start to see perhaps these very very light white bumps those are and tenders like this one and now using the marvel of google put into into perspective again here is our circle we have a few straight lines that go off to antennas that are at some distance but the important thing is we in this area we have five hundred antennas so we have five hundred of these set up running in parallel and we use that to make images of the sky as i mentioned originally are friends of the long wavelength the ray are using their sets of roughly five hundred antennas to make horizon to horizon images of the sky and so here we have the sun we have the galactic plane we now have horrifying we have her go away there so the important thing is that this at the celtic valley observatory we use supercomputing there is a supercomputer in a often in the middle to combine the signals from all five hundred antennas to make images of the sky and also we're using that to look back into the dark ages that is to try to measure the temperature of hydrogen so i mean zoom in further you can see the replica of what's off to the side and this is now looking north we have two parallel lines of mountains one reason this is a fantastic site is that you have mountains that rise ten thousand feet off the valley floor up to ten thousand feet and it blocks the radio the t v from from the coast and from las vegas and from reno and it's in that sense this is an outstanding location the supercomputer lives inside this the most impressive thing about this picture i believe is one of the world's largest i'm sorry the largest air conditioner for many tens of miles it is you probably could try to keep those antennas away from everything else so this antenna wouldn't be terribly useful right now because it's near metal it's near people it well part from being near digital television it's something that is going  know it interacts with its environment but so we try to keep some number of antennas very isolated except for four for us and pressure treated kind sorry pressure treated timbers and you can see that these are really what the scale is in terms of the brush which comes up to maybe maybe need knee height so what we do is we have ten of those antennas we attempt to measure the temperature of the hydrogen in the early universe and we're doing it one of the reasons we need isolation from the coast is were doing it at the same frequencies where you would find radio aeronautical beacons old television in the original lower v h f band and then we attempt to also take from the dark age so in order to do this we have to make images of the sky we have to measure the i honest fear and bring up the honest fear specifically if you think back to stories about you magnetic storms when the sun is very active communications is disrupted a lot of that is because the i honest fear which is which is normally relatively placid it's just a you could think of it as a sheet overhead it begins to get ripples and it has waves that are traveling through the plasma which interferes with smooth transmission of radio it might start reflecting radiation that it doesn't normally reflect and things become very difficult for radio stronger is nice conditions because a source which you know is always going to be there at nine pm suddenly starts drifting around and that is because the ionosphere is is acting up but the honest f everywhere and the iris fear here may be behaving differently from here due to proximity to say the sun or an event relating to a solar burst and so your sky becomes a rubbery sheet in some sense and we need to calibrate that out if we were observing the frequencies the normal frequencies of you know quote unquote normal frequencies of say cell phones or maybe radar navigational radar for cars this wouldn't happen the  transparent but that these are very low frequencies and this is one reason the radio astronomers don't normally work these frequencies were intensely sensitive to this sort of wobbly i honest here that distorts the sky so  again we need to actually make images of the sky so we can figure out what the eye on a sphere is doing so that we can ultimately then under stored the data which we're trying to collect from from the dark age so  is skip this in the interest of time except to note that what we're trying to measure is extremely faint by calibrating the data we go from we gain about a factor of fifty which is nice but not if you need to gain a factor of a million but it it's a start and this better get started ok so now this is similar to that this is now an image which is  galactic plane is rotating overhead here are two very bright sources one is a supernova remnant you can see this thing moving off just setting now that actually was the sun and if and i think this is going to come back around  think it's a couple days and what you'll see is that all the sources the bright sources are basically the same intensity but then the sun comes up and it starts bursting and that's an example of why for instance we don't want to observe during the day this movie is made during the day in any case the important thing or the impressive thing is again this is a horizon to horizon image of the sky that is to say ten seconds of data process it and out pops something that you would not be able to do readily with an optical telescope you also get an interesting feature here i'll play it up in the next slide but while this is the galactic plane there is something that comes off the  that we don't see when we look in the summer sky so on the left we have a halting image again from the radio and this is a fisheye lens looking at the optical sky so here's thing which i just pointed out it comes off the glass the plane but there's nothing there here's the galactic plane or the milky way the sun just came up but in any case this is an example of the radio sky is not it can be very different from the optical sky so the stuff that we have to look through in order to get outside our galaxy and to begin trying to sense the starcade signal that we can see through c because we're studying the temperature of hydrogen  very early times is you know it's not it it's not it's not a normal sky from from a regular person standpoint so i'm going to close with just this is a second to last slide and note for instance on the left this is a spectra a very simplified spectrum so we have a prediction from theory the prediction is we will see this we'll see a trough and early on i said well there are vents that change this temperature of hydrogen one of them is the formation of the first stars and so this is the trough for a couple different scenarios sort of the lowest curve is yellow so it probably doesn't show up but we go from calculations of how accurately with these error bars here how accurately we can make a measurement in i think it's one hundred hours so these are bars are small we should be able to trace this extremely well but thus far have only gotten to about one one thousand one one thousandth and we have about another factor of one hundred to go and this is some recent data and you can see it doesn't look as good as this because we don't yet have the sensitivity we need but that's something that we hope that will be able to overcome in in the next year the one thing i like about this plot specifically is that these troughs occur at a frequency of about sixty five megahertz and there is a trough here at about sixty five megahertz but it's not statistically important but it's very nice because it makes me think of what i wish could be the so i just want to end with this going back it's our book with blank pages the arrow is an indication of more or less where we're looking when worse trying to study the dark age and over time for instance with the murchison widefield array which richard von mentioned and with the long wave length ran the leader experiment that we're doing now we hope the project that our projects and projects like them will be able to fill in this entirety and we will not have this blank in the cosmological record during this period when all the important stuff happened in the first metals were generated by the first supernova without which that wouldn't be here  ok so yes it so the the problem that we have when we have five hundred and ten is like that is that you have a lot of cable and you have a lot of signals that you get and have to get into very compact space that you can funnel it in for computer processing so this is one of the receiver boards that was designed by the long wavelength array folks in new mexico which we have had replicated for the station in california and it has sixteen signal paths essentially you can see that there is more or less this colin yeah ready in the layout so the signals come in from here they are then distributed across the board the signals flow up and then they flow out on this side and this is really just an enormous amplifier which is generating tens of thousands in terms of gain that is the signal is amplified by tens of thousands of times and it has to be such an enormous such a large boards that you can fit in a reasonably small space without breaking the bank all of those signal paths so you could just imagine you know bringing five hundred coaxial cables into one space i don't have the slide to load it up but it makes for a lot of very modern art in terms of the photography that is again it's a matter of covering a wall full of connectors the cables come in on one side then they depart the other then you might reduce the number by a factor of four then you might reduce it by another factor created by the fact that you have sixteen all in one place and then you go on and on until you can fit it into the processing of quickly computer processing equipment without having to bring to bear on that computer five hundred cables so in this particular case i think we have  hundred and in california we have one hundred twenty eight cables that are coming in to the computer but every individual into the computer is plural but every individual computer only has what i'm having  danny i'm having a senior moment i'm sorry each of the roaches takes thirty two but it's eight cables right ok thank you so but again this is a level of game that you that is absurdly high simply because the signals need to because the signals are intrinsically weak if we had a satellite tracking dishes or something like a high frequency radio antenna  reflector it is a huge amount of collecting area concentrating all of the energy to a point a t v effectively a t v antenna is something with very low efficiency and that's one reason why we need five hundred of them or hundreds or in the future with other projects thousands in order to build up enough collecting area to have the sensitivity for whatever for for the phenomenon in some cases it could be x of planets in our case it's ah no so at higher frequencies cell phone radar type frequencies many many gigahertz frequencies yes you would want to use cryogenics to cool that because it reduces the contribution of the receiver to the overall signal so the sky and high frequencies gigahertz above is basically dark except for bright spots the bright spot might be something that's created by star could be signals from a black hole from a jet of material coming off a black hole but largely the the space around it is dark at these low frequencies we have actually the galaxy that is the milky way galaxy or the milky way or the galactic plane is not just a little narrow band on the sky it actually and it's not well shown there were you also see the milky way it's actually just a wide ribbon with all sorts of spurs i pointed out one of the wisps that are coming off of it and all of that gas isn't or all of that is intensely hot it's intensely bright and so what we end up with is a situation where the receiver noise is an important even if i might be a little flip when i said if i set that on fire my receiver noise would still be low compared to what i have in the sky so what we have heard of that is being sky noise dominated instead of receiver noise dominated once you know receive  noise dominated you can actually use fairly cheap components which is good because we have to replicate them so many times because we need so many antennas to build a collecting area so we have no cryogenics and therefore many fewer moving  i don't know the details however if you go to a lustrous hyphen project dot org you'll come across it but it's a very good question in that you can't make the computer infinitely powerful which is what you would need to send to simulate everything from the size of many clusters of galaxies which would be to simulate something that might be a billion light years across all the way down to what might be the size of i don't know a cloud out of which a solar system would form so you can't do that at a certain point it does truncate and they say ok there is physics going on at this and smaller scales but we can approximate it in the following way and come up with something which is a reasonable a reasonable replication of what we know happens when we're able to study say how stars form in great detail so the tricks that you can play for instance you can do the calculation on a grid of points the grid is very coarse and then you say ah there's something interesting going on here of stars forming and then you start making a very fine grid at that point and then you discover oh ok that's not one starts ten stars and then you go to a number of even finer grids but you're saving space time or computing time each time with each each sha transition from course to find a very find a very fine because you have a lot of space theoretically where you don't have to apply that very fine grid so if you had ten stars it's all the space in between those ten stars and the neighbors you economize so the actual granularity of that simulation i don't know it's the biggest i believe it is the biggest simulation that is ever been done and so it is it has it's basically a gold mine of information that we can study in terms of finding out so what's going on here and why does this look that way and things like that so but on the other hand it is a simulation it's based on our current understanding of physics and so you just can't push it back necessarily with certain accuracy and so that's why for the dark age we're desperate to get data so that we can actually start testing hypotheses figuring out which models to throw away which models to embrace ultimately to improve the accuracy of simulations like that yes opportunity to train and inspire students and those students don't go on to do necessarily astronomy or cosmology they go on to work in mathematics physics engineering computer science many other fields which they may not have actually which they you know in a different universe a parallel universe they might not have actually been attracted to had they not you know received that initial i guess spark of fascination  curiosity brought to them because they would be studying something else while looking up in the night sky as i said that might be overly simplistic there are also direct economic benefits that is to say what we are just to take our experiment as an example i mentioned we have a supercomputer it's sitting in the middle of effectively a desert in a shipping container in order to build that we took commercial products and we use them in very unusual ways  commercial products are graphics processing units you know for used for computer gaming however people had not previously used those two process to do signal processing in real time probably the military did but outside we people had not done it so the radio astronomy years needed to come up with a very efficient way to combine signals from this many antennas over you know twenty times as many of twenty times as many antennas as had previously been done if it's twenty times it's actually four hundred times harder you need some cheap way so we take from from the commercial industry what we can and what we end up with is actually something in one specific case it's a computer code an algorithm that is so well characterized because it has to process of signals like clockwork it's so well it's so well understood that it actually enables the company that makes those processing units it enables them to run benchmarks and to study what kind of features should we have why is this compiler for our computer for our codes not actually working in this case and so there's discovery there it's basically a lot of times you're pushing the envelope if i were an optical astronomy or i would talk about well see c d s came to optical astronomy from the military or from other applications and our sensitivity requirements were much much higher and so we started picking and choosing that is we would pick c d s that had just particular characteristics it might have been a one in a batch of one hundred that was particularly good and what do you end up with is  the development then that is done in this different field in astronomy pushing developments that might have commercial applications but and i could have gone to magnetic resonance imaging ultimately the mathematics that was developed for how we combine these signals and magnetic resonance imaging there combined there was there were intellectual exchanges i mean ideas flowed back and forth between these key two communities and obviously m r i is something of a benefit that if you talk to a writer stronger in one thousand and fifty they would not have necessarily guessed so it is tough but there are direct links i don't remember the citation but there is actually a book that i was referred to i haven't studied it in which there's discussion about you know what those commercial benefits have been for for some particular elements of radio astronomy you know like i could find i ah so so first i have to apologize because when an astronomer talks about metal anything that is more then helium is considered metal so  it's it it's pretty sad i just happen to have aluminum that i could point to but actually you know the carbon and oxygen is also considered a metal so the but having moved that out of that definition out of the way it comes from the centers of stars so stars will synthesize elements up to iron and every time it makes something that is a little bit further along in the periodic table with nuclei that are a little heavier it will generate extra energy that is that is the fusion process that goes into pushing two things together to make elements liberates more energy and that is more energy than you have when those things are separate and that's why stars burn at a certain point you get the iron and then that's the dead end you can't generate more energy want to make things that are heavier than iron and so actually stars then build up cores within very massive stars who build up cores that have carbon and oxygen and nitrogen etc etc up to iron and then you have a dead cinder which is in the center of the stars ultimately because that cinder just becomes dead weight literally the star tries to compensate not anthropomorphizing stars but it tries to compensate by burning the gas it can burn elsewhere ultimately that fails it just can't support itself and everything collapses with an explosion that's a supernova which sense much of the material that was created these metals carbon nitrogen oxygen out into the cosmos in a sort of cycle that is to say a cycle because it will form clouds ultimately those clouds too will collapse at some later point and maybe that's the star that comes from that will explode and you recycle this material so that's why people say we are made of well sorry that's why carl sagan's comment was we are made of star stuff because we only exist because of explosion exploding stars and the stars that i was referring to from you know the very first stars they may have only had lives  of a few million years before they blew up but they spread there they spread that the metals that they generated throughout the cosmos and then other stars formed out of that polluted gas and then they there was a that that that that is a really good question black holes come from stars with one exception which has not been demonstrated so let me go to the exception because it has a cool name so primordial black holes the concept is that that those actually came from the the period before the dark age and they would not necessarily be massive  in fact they might just evaporate over time they won't go into an evaporation why why black holes can evaporate but so that there's a special case they're called promotable black holes we have not ever observed them they're just a theoretical construct the black holes i was referring to are all the byproduct of stellar evolution so stars have to come first and very massive stars create super supernova create black holes and then they issue and then the question is i raised it is how do you get from something that might be a lot of ten solar mass black holes to something that might be a million solar mass black hole such as we find in li galaxies or a billion solar mass black hole such as we find in virgo way which is just on the left side of that display so the crushing force of the explosion in the in in the supernova and the collapse of material under the force of gravity for that stellar core is what creates a black hole and then i wouldn't say it wanders around but ultimately it will encounter other black holes and the theory is that then you have mergers black holes combine more black holes combine heavy weight black holes combine to make heavier weight black holes and it's perhaps a tree structure which ultimately gets you to say billion solar mass black hole and we know that those exist a billion years after the big bang that is at the end of the swiss cheese phase of the universe you had some small number of billion solar mass black holes that we know now there were there are probably more that we just have not detected yet but that there are any is rather remarkable that is how you know do you have to have ten million events where you  are merging things together to get a billion solar mass black hole and it does that mean it had to happen every thousand years every hundred thousand years at what rate so we don't understand yet why there can be such heavyweights so early in the universe but everything ultimately came from stars and in fact it was it's those remnants those black holes or the neutron stars or other things that actually played a key generated a lot of the x ray of mission that have that was necessary to reheat the universe but i won't go into that so they are not just some sort of i guess population genetics experiment how do i make this thing out of this you know a lot of little  lot of little contributors and i get to this these genetics at the end with a bunch of bill and of the genetics of the billion solar mass black holes black holes on the way are actually changing the nature of the game surround them they're raising the temperature and that changes for instance how readily stars can conform out of collapsing clouds of gas so it they they change everything it's not just a question of population it so let's see technology that would one of the one of the most difficult challenges that we have in using instruments like this and in conceiving larger ones for a reasonable price point is is the computing not just i'd like the technology part of that is like the technology to build a computer that is power efficient and one hundred times or a thousand times larger than the one that we have in that shipping container it's also a matter of the i classify this is technology having the algorithms the that is having the algorithms the equations that are cast into computer code that will operate efficiently enough that whatever the calculation i need to do if i had say ten thousand of these antennas i would like to be able to process that data efficiently the real time computing that i referred to using graphics processing units is pro is a solved problem that is we think we  know after having gone through this project and some other projects are doing the same we know how to do that but what comes next is how you make the images and so you're sensually you're taking the output from one supercomputer and you're putting it into a different supercomputer we don't know how to do that calculation efficiently yet we it's almost as if we have lots of building blocks and no one has actually come up with the building blocks that you would want to stitch together and try to do something for less than ten make a watts or i make up that number but the amount of power can be enormous there's a project called the project in development in in the real world outside this room called the square kilometer array it's an international project one of the goals is to build a huge array of antennas not an array of huge and tennis and the one of the great problems is how do you build such a large facility without requiring its own power plant or some people would say without creating your own nuclear power plant butt it's really just a matter of we we need high efficiency computing we need enormous amounts of it because the better the algorithm the better the images and those images are nice but those images were done on just a few computer servers running in real time are in the images that were that i showed in the movies here were also done with a relatively small number of computers but if i want to make a better image i probably need to iterate a bit that is to say to clean out the errors in calibration and if i started a rating i can iterate ten times and get a great it's incredibly expensive and i couldn't afford the computer to do that but at some point i'm actually he will be able to and so one of the tricks that when we learned how to combine the signals from this many large number of intel is one of our tricks was just sort of stay slightly behind the curve industry was then able to generate things that enabled us to do enough processing in a small space for a low enough power budget and then as i mentioned you know we were then able to start pushing in different directions and feeding back information and into industry so don't know if i want to really say that i'm yearning for computers i prefer warp drive because then we could just go there and look i would much prefer having warp drive because then i can actually go to the places rather than observe them remotely and in science fiction movies that always works best to have been tested question