Space Time Livestream: Ask Matt Anything

okay well we hit a thousand people so I think it's officially a party um so this is totally weird I'm used to talking to you through this channel and you're used to seeing me I guess but usually there's this time lag like you're in my future I'm in your past this is the first time I think I've talked to you in the present or is the present an illusion I'm not sure but I need to welcome you to my home my living room some of you men most of you probably you early guys have seen my living room before you've hung out here for the past few episodes this is the lockdown studio but having you here right now is extra exciting so welcome normally I would offer you a drink but there's one point four thousand of you and we don't have that technology yet so fetch yourself a drink please I already did and here's to you this is a Negroni by the way I don't know if any of you follow viral cocktail memes but recently stanley tucci the great actor made the rounds for there's little footage of him making a Negroni in his like caravan or whatever on shoot and everyone's like oh my god the perfect Negroni I beg to differ Stanley use too much gin he did use exactly the right type of vermouth but he shook rather than stirred I'll probably show you guys how to make the actual perfect Negroni there's a little secret I don't know if I'll have time today but for now here's to you that is Jewish so this is the first space time livestream I don't know why we thought this was a good idea except for the fact that you know I am locked in this apartment and it just seemed it seems like a time to do crazy stuff so how is this going to work well it's gonna work how how it always works when we have nearly 2,000 people in a room together we're gonna talk about whatever we want to talk about we're gonna talk about space stuff physics stuff but we're also going to talk about really anything else that that we get to you guys can put your questions in here as I see you are we also asked for questions pre questions in the community tab on the channel and we'll select a few of those questions and we also have some questions from the discord channel okay so the discord Channel like if you think this is fun the discord channel is internet space talk physics talk 24/7 you do need to be a patreon subscriber but lowest here a couple bucks a month grants you access and and there are people much smarter than me there so it's the place to get your your physics questions answered my microphone seems to a popped my shirt button that's unseemly okay so there's lots of types of questions we could we could go through I'm gonna just start by talking about the show and we'll get into some science and we'll get into some other stuff as we go along as it feels right so you know space time where what are we five years in six years in we've done I believe it's over two than 40 episodes now I don't think we have a thought that that would be possible starting a show with such a you know ostensibly narrow field of interest hardcore physics and astrophysics but it turns out that the universe is big end and deep and I cannot think of an end to topics that I want to talk about that said we have some very cool stuff coming up we just shot an episode on a cool topic the luminiferous ether I can now say that word it took many takes to be able to say it reliably the luminiferous ether which is this archaic notion about the medium through which light propagates and the death of the idea in the late 1900s late 1800s actually in the era of relativity and quantum physics and this is kind of you know Astro 101 except for the fact that I dearly love these old wrong theories I think they're so colorful and cool you know the the one electron universe of John Archibald wheeler or Paul Dirac's electron see I'm just a huge fan of the wrong old science that actually pushed the science forward so I'm really excited for that episode I think it came out really well it is of course right here in the apartment we're working super hard with our resident quantum physicist Graham Garcelle on a topic about electroweak unification ok so one for the hard core that I think it's going to be very beautiful because it really I think reveals how it is that the forces of nature our notion of of what a force is emerges from the simple concept of asymmetry so with with these super hard ones we struggle for weeks and weeks to get them right because it's you know it's it's tough doing quantum field theory in 10 to 12 minutes but it's it's really coming together nicely so those are two things that I'm really looking forward to and maybe I can give you some more hints about what we have going on down the line as I as I move through some of your questions which I should do right now so I'm gonna jump into a couple of questions that we got from from the discord and from the community Channel let's see we will start with questions about the show and then we'll jump into some sides okay so to tool from the discord asks how many hours of work do you put it into an average video well the answer for that is me personally it depends massively on the video if it's something I know well then I can write a script in you know a few hours but if it's something like gauge theory and electroweak symmetry breaking then working hard with the quantum physicist it takes us it can take us many many hours but but scattered over weeks it's really it's really hard to even enumerate them and presumably dreaming about stuff as well I was certainly dreaming about quantum with gravity and string theory when we were writing those episodes so so it varies massively but you know the show isn't you know me I do the talky part and I also you know I write most of the episodes with essential help in in some cases but the show wouldn't be the show if it wasn't very beautifully animated and currently we have an amazing animator animation team actually led by Leo in Brazil details were in every credit and these guys work hard with me as I you know try to somehow articulate what I think things should look like and what what scientifically accurate but they also put an incredible amount of their own artistic ability into it Andrew corn Hebert of corn Hebert Brown is the producer of the show directs the show and until the lockdown he shot the show as well that you know these days these days My partner bahar who-who you may meet sort of takes on the role of assistant director on camera and so you know it's a team of a few people and I mean you know in the end we do one show a week so it takes us that much time I also try to do other things and there are some questions about that so I hopefully get to those as well let's see so I think I just answered Emily also from the discourse question how do we develop the graphics and imagery really it's it's a collaborative thing and we iterate and I send bad mock-up graphics and and the graphics team produces beautiful graphics is the graphics team educated in physics Emily asks the answer is they're becoming increasingly educated in physics and the main thing is that they are just very smart and so you know that they get it very quickly so you know that's the show it's a labor of love and you know we'll keep doing it as long as we can but honestly it's your support and the the fact that you know PBS sees your extreme enthusiasm for us doing this that that ensures that we keeping able to do so let's talk about science because this you know really this is a science show and this is what we all care about so I'm gonna let's see maybe I'll take a question from the audience if I can locate my browser you guys are you guys are flicking through so fast favorite Mass Effect game there were multiple Mass Effect questions actually including let me see Oh we'll get to that later let's talk science for now Matt if your f is chemistry between us I guess that science what's your deal man this is these are unanswerable questions my favorite type of sandwich I don't know I really like a great tuna melt I make a great tuna melt why is the speed of light what it is that's a deep one so this question is one I asked also coming into thinking about physics and becoming a physicist and the I guess the the shorter answer is it's because we define it to be what it is we define the speed of light to be what it is because we define the length of the second and we define you know the meter and so we end up with a certain number of meters per second but I like to think of the speed of light as the speed of causality if you choose to think of the universe as a like an ensemble of little elements maybe they're pieces of space maybe there's something from which space emerges but aren't spaced themselves but they talk to each other at a certain rate okay a change in one part of the universe can lead to a change in the adjacent part of the universe and so on and so on and so on and that rate of communication that rate of causal influence is precedes propagates at the speed of light it's really the speed of information okay the speed of causality and it doesn't necessarily have a fundamental speed in itself what what's fundamental is that it can happen at all the the idea of the speed of light comes into it when we think about sort of the size scale of the observer the size scale of a human being relative to that propagation okay so how many little propagate eighteen blips does it take for that propagation to for example traverse you know the size of my head okay and so the speed of light use what it is because it's a statement about our scale relative to these fundamental tiny scales okay I see an episode here I think this is going to be a great episode at some point but but you know physicists like to set the speed of light as being dimensionless and set it equal to one which is totally reasonable if for the right definition of you know length and time and so speeding up the speed of light or slowing it down it's not even clear what that would mean for the rest of the universe lit so the the the idea of an an object in space or a most fundamental element of space influencing the next element and influencing the next element and so patterns emerging and so all this amazing emergent structure appearing in the universe this notion is sometimes referred to as as the idea of cellular automata okay so the idea that you can think of the simple set of rules for an element of space in interacting with neighboring elements and that will lead to this emergent complex structure okay and you know a the perhaps the most famous example of that is Conway's Game of Life which you've all seen it I think if not google it but by the way John Conway who who was the great mathematician who cannot with the game of life recently passed away so so ROP to John Conway sadly of of copán 19 but that so the idea of cellular automata I bring it up because it is was a question from our community tab Jake Montgomery asks what do I think of Stephen Wolfram's new idea for a theory of everything ok so again this one has been all over the news recently mostly because I think Stephen Wolfram the blasted over the media but but this is the the theory is a type of cellular automata theory in which these kind of connected structures have these rules by which they can evolve and then you can produce all sorts of geometries and according to Stephen Wolfram you can basically recover the laws of physics and our universe from the this notion of a cellular automata so what do I think of it well you know I skimmed the 450 page paper which means I certainly didn't read the flyer 50 page paper but I got a sense of of the fundamentals of the notion not enough to be able to say whether Wolfram's claim is right that it can recover special relativity general relativity quantum field theory and all this stuff so I maybe the best thing is for me to cede this answer to someone who would know much better than me now this is hearsay I got this secondhand a friend of mine is a surfing buddy of Garrett Lisi who some of you will know for his is a called the incredibly simple theory of everything there's a TED talk it's an e 8 theory for particle physics and Garrett Lisi found it says here say so so our leasing can can happily deny this it may not be the case but it seems reasonable to me that Wolfram's notion suburban Majesty majestic but probably a waste of time and to understand why well I think this is all in general I'm fascinated by cellular automata so I may do an episode on this in fact I think I must in in Wolfram's idea the essentially you can produce these emerging structures of space and time from these simple evolving rules you know like Conway's Game of Life but the problem is that there's no way to predict what universe will emerge from a given set of rules and wolfram calls this this this concept irreducible computability which is to say you can't use these set this set of rules to project whether this you know this particular set of rules will generate a universe of three dimensions that have this particular set of laws for gravity for particles whatever the only way to learn this to what to learn what universe emerges is to run a full universe simulation and see what universe emerges okay and so you know in the sense of a potentially being a waste of time it may not ever be testable that said some of the greats in physics have turned to these ideal ideas of cellular automata ok Gerard T Hooft you know the great string theorist or great every-everything physicist published at a cellular automata paper not necessarily saying that it was right but just to show that it was possible the idea that that you can have rules that take simple bits of information and and and generate something complex and John Archibald wheeler also with his notion of it from be OK in complexity and the idea of physicality emerging from from simple more like informational components that you know there's something compelling there okay so I wouldn't discard wheelers Wolfram's idea just yet but he probably should get that thing peer-reviewed which he has not and so it's only had to judge me being a lowly astrophysicist okay so I'm gonna turn to another question from there's a couple of good questions on conservation laws so Michael from the community tab asks if I can describe how dark energy and evaporating black holes with virtual particles do not violate conservation laws so let's start with let's start with dark energy because Thomas Lopez also asks if we can explain how what happens to the energy of photons that are redshifted okay and the restrict of gravitational waves what happens to their energy well so the answer is there are a couple of schools of thoughts on this regarding energy not being conserved in an expanding universe so school thought number one is that the loss of the energy of those photons and the creation of new dark energy in an accelerating expanding universe actually does violate the conservation of energy and that that's fine and the reason that could be fine is that conservation of energy is specifically valid for time symmetric systems so we did an episode on Emmy Noether x' theorem which reveals the sort why quantities are conserved at all and it's when there's a conserved quantity a symmetric quantity okay so if the laws of physics work same going forwards or backwards or work the same from one time versus another time in the universe then it's a relatively simple calculation shows that we must have this conserved quantity called energy now in an expanding universe time is not symmetric if you reverse the expansion then the universe is getting smaller rather than larger okay so the space itself is changing and if you look at different times in the universe they're not symmetric okay so this changing and with that change we lose the ability to say that energies could serve now it may be well there are there are other analogous conserved quantities that that you can invoke like the in general to be there are more complex conserved quantities that are analogous to to energy in that in that case but but your energy is such an abstract concept think about what it is kinetic energy half MV squared okay gravitational potential energy okay GM M over R okay these these are mathematical quantities that happen to be you know they happened to all that up to the same thing but there's nothing necessarily fundamental about the concept of energy although we have come to believe it and to feel that there's something so so fundamental okay so that's point of view number one point of view number two is that energy is actually conserved in the expanding universe and the addition of new dark energy and the loss of energy from red shifted photons is offset by the fact that as the universe gets bigger it acquires more and more negative gravitational potential energy okay and so if energy can be negative then it's possible to add positive energy now this doesn't sound very intuitive because you know you could just infinitely create an enormous amount of mass if you're allowed to continually borrow infant li from this this well of negative gravitational potential energy okay which of these is right possibly both are reasonable ways to look at it I'm I kind of prefer the first description just because you know I I think it's it's good for us to not be stuck you know ideas of what what is fundamental including potentially the conservation of energy ok so Michael also talked about conservation laws in black holes now black holes conserve energy because they grow in mass when they swallow things they conserve angular momentum and charge because they acquire those properties when they swallow things those properties the issuer think that for things like your particle physics things like baryon number okay so the number of protons neutrons can be changed but but more importantly quantum information okay so when black holes were first conceived and it became clear that that quantum information made it be destroyed in particular when Stephen Hawking realized that black holes must radiate and the radiation produced by black holes would be this totally random thermal glow okay of radiation which should contain none of the information of anything that fell into the black hole before it and that could should continue to happen until the black hole evaporates into a puff of of energy and and all of the quantum information that went in before should be gone now this if anything is fundamental that should be conserved it is quantum information and the reason is that quantum mechanics really really depends on the on the on this one concept on the conservation of quantum information of course we've done episodes on it now we think we now know that in fact black holes may actually of quantum information even through their hawking radiation and to answer why I'm gonna read the question from from Bob dead I hope you're okay Bob which is that when mass is just about the event horizon of a black hole is the event horizon slightly distorted due to the effects of the extra matter how is that related well Bob dead in that question just solved the black hole information paradox because that is exactly the proposal that Gerard T Hooft who I mentioned earlier for his cellular automata came up with to save quote the conservation of quantum information in black holes the idea being that in a black hole when things fall in they slightly distort the gravitational field at the event horizon at the location where they fell in okay so for someone exterior to the black hole what they see is this kind of frozen imprint on the event horizon where things fell through and in reality they don't see things fall through they just see objects falling and becoming frozen in time and that ultimately manifests as a a distortions in the gravitational field of the event horizon and those distortions then influence the hawking radiation but that black hole later emits and can give to that Hawking radiation the quantum energy showed the quantum information of the infalling objects and so the Hawking radiation should therefore carry out that quantum information ok so well done Bobby you solved the quantum information paradox a couple of decades late and by the way the the whole idea that you can have this information printed on the exterior of the black hole is what started the whole holographic principle which leonard susskind then came in and gave a full sort of string theoretical to and showed us that you know holy crap it may be that the whole universe is such a an information imprinted on the surface one second guys I'm gonna let you guys hang out with our friends for a minute while I do this guy's this is Simone Simone the cat she made a brief appearance in the comment responses a couple of episodes ago many of you are asking to meet her we'll introduce you properly Simone loves to watch the pigeons out the windows landed on the fire escape which is also a huge fan of treats well no she's too distracted right now by you like okay thank you for sitting through that short commercial break we're back live I hope Simone entertained you just as a an example of some of the challenges that we go through filming every episode these days just down the street there's a fire station and so particularly in these troubled times the sounds of New York in emergency cut off our recording of essentially every paragraph and so we have to go back to the start in the chord again that and the garbage trucks but you know it's the price of living in the big pandemic ridden city I guess okay so you know one thing that I thought this would be a cool opportunity to do would be to talk about some of the stuff that we're all doing in these difficult times you know I've been mostly stuck in this apartment I've been running a lot more because we're allowed to go running but I'm interested in what you guys are up to whether you have to for getting through quarantine if you are indeed locked down like we are please let us know it's not so bad say hi to everyone Simone alright so while you're typing those comments I'm going to show you around a little bit not too much because most of this apartment is this giant hoarders trash heap it's mostly floor-to-ceiling toilet paper rolls hand sanitizer and just bags of refuse that's a joke we have three rolls of toilet paper I'm actually slightly worried but I do want to show you a couple of things okay you've met Simone mostly I want to show you what I'm reading right now okay some of this you get a lot more time to read when when the outside world is deadly okay so well first up while we're here a number of you many of you have commented on this piece of art okay it's a it's a beautiful time to see it because the Sun shines off the gold leaf but what is it where did it come from well I'm pleased to say that it was created by my partner who his name is Behar and I would actually love it if she would come and say hi to all so the artist in residence this is the hi and Simone Simone is shy she's never had such a large audience before friends right you get used to the camera yeah maybe someone can go away just for the moment okay so this is bahar bahar created this amazing piece of art okay and so my own artistic taste was finding the right person the right woman and by chance this came with it but people are quite curious about this piece what what can what can you tell them it's the galaxy the galaxy plane to the crowd but oh it is gold leaf and goals was forged in some supernova well emerging of nutrients neutrons to see you learn a lot living in che mats and bahar so it's gold leaf painted with a variety of inks and and indeed gold we used to think it was forged in the hearts of the most massive stars before they well as they exploded as as they exploded yeah collapsed and exploded as supernovae but recent findings in particular watching that one merging neutron star pair that followed that gravitational wave signal indicated that in fact gold may be forged in the mergers of neutral sites as many of the heavy elements and many of the elements in your body okay so we have this is not really cool this is copper and zinc what what all this time the lies it's stunning maybe maybe we'll see more of a huzzah now the heart is only incidentally a great artist she's also a science writer and I actually thought that maybe she could help answer a question that that you all had or that so that someone had can I find that real quick well the question was what is my favorite fact and the the the fact that that our ask whose name I can't locate while I'm holding his laptop up there favorite science fact was about how radio-controlled I'm guessing planes can do a flip in the air and how it's all about the conservation of angular momentum well it so happens so this is about the cat okay this is about the cat cats always falling on their feet no matter how you throw them we could demonstrate that when we're not gonna drop Simone but yeah that it's been actually a huge mystery for over 300 years well how cat can turn themselves me there with without violating the conservation of angular momentum and you want me to explain well you say so but I wrote a New York Times article on this very topic it's the print edition so you can't book it up unless you have unless you're also quarters and have a stack of New York Times but you can give us a sense okay so I'm going to do it this is not this is not a trivial question it's been kind of stumped scientists for over at least 300 years but not just any scientists know like people like James Clerk Maxwell they tried to figure out how cats flipped midair without pushing in against anything without you know an internal engine literally by dropping cats by the way yeah apparently there was a rumor about him at Trinity that he he drops cats out the window hmm and apparently that's not true according to him he only dropped them two inches oh well trying to see how quickly they can do it and you can do it too two inches up they can still rotate enough that's great how can a body a free-falling body rotate itself minute do you want to tell us it can do it in vacuum I can do it can do it in you know outer space there are some amazing videos of astronauts trying to drop cats you like you need to know the army or know the airforce experiments in 60s very important research very important research so yeah so I do need to do an episode on that but but but the answer is really cool and it's especially cool because we don't actually know for sure there are just some proposals but it's it's it's pretty nifty yeah well essentially what it comes down to and there's a look there are a lot of details and not it's there's no like complete consensus and how it this happens but it does not violate conservation of angular momentum obviously that's a magical not in this case but what they do is that they're not a rigid body so they divide their body in two parts by bending their backbone and rotate them but stretching the arms and legs and the right combination so that in the end it all adds up doesn't violate anything it's perfectly legal as far as physics is concerned and cool enough that it really warrants a full graphics team to be on it yeah yeah so stand by for that okay Thank You bhai everyone thank Maha okay so beautiful art I I'm very lucky both you know mostly for Behar but also for the art there's here's another piece right here that's that's in the works this one is we has some amazing patinas on the copper it's it's going to be incredible I mean it is incredible already actually I want her to be done with it because we can hang it oh he's so I have telescopes this is a little show-and-tell well we're on our way to the books by the way this well this is a lamp I call it the Eye of Sauron because it's extremely like ominous and and we rarely turn it on because it's a little bit scary here we have a solar telescope yes this is a six centimeter aperture solar telescope its main job is to block light out rather than let it in middle it's only to only a tiny tiny wavelength band from an emission line hydrogen-alpha I think it is in the upper atmosphere of the Sun so you see these incredible details of the strung of the sun's structure you can see the convection cells where plasma is bubbling up from below the interior of the Sun you see the sunspots of course you see prominences on the edge where your giant streamers of plasma are channeled by magnetic fields it's a cool cool toy now but what have I actually been doing during the lockdown well this thing here is you know it's a block of concrete because there wasn't enough concrete jungle outside it's a coffee table and I made that it's actually super dodgy it's it's made of wood we had lying around the house then coated with this kind of concrete surfacing material and it actually is concrete but we didn't actually have to pour a full thing of concrete that's a draw it's a concrete block with a draw I know incredible inside the drawer there will be a projector there's going to be a speaker built into a game console all of this cool stuff hopefully I've come become very attached to my apartment during this time and I just really feel the need to do things that aren't just sitting at my computer okay so trying to build crap we try to fill the place with a lot of plants because it makes us feel a little less trapped here is another telescope now this is a little bit difficult to see in the light here but this is a rather large telescope okay so it's a 10 inch Dobsonian you can see the I mean the rings of Saturn are amazing with that telescope it's also a plan holder by the way I bet you didn't realise but but telescopes make amazing plant holders okay back here we have a Bissell reading nook okay that funny shape thing is one of Simone's little homes around the house okay piles of books some read some not read for the moment what I'm gonna do is place you all on top of the telescope it also makes a fantastic laptop holder as well as a plant holder okay so right here and there we go we have some books okay so the main I guess motivation for this bookshelf is that we're either reading right now and really into or that we want people to think that we're reading right now and they're really into that that's a joke we actually do our best to reading this stuff but you know there's also some much dorkier stuff that we wouldn't good here okay so I mean there's a lot here the worst book by far is my PhD thesis the host galaxies of radio loud active galactic nuclei I think it's only been read by the three examiner's my mother I don't think my advisor even read it actually but that's that's a oh the her asks who I got it signed by and the answer to that if I can find that chapter maybe I'll ask you to find that chapter while a well well I get back to this thing so so but how is a neuroscientist by training okay science writer by profession and so more of her stuff is here principles of neural science candle schwarz Jessel classic okay some other there's some some Oliver Sacks here so you know more brain stuff this one I love and I assume that this is on everyone's bookshelf this is malformed forgotten brains of the Texas state mental hospital okay obviously an academic classic it's just full of beautiful beautiful malformed brains of different types it's the ultimate coffee table piece this is a topical one right now poached okay so this is on the world of wildlife trafficking and you know clearly we are now seeing the consequences of wildlife trafficking which is that we have these emergent diseases which were safe in their reservoirs among you know different species like bats or pangolins but brought out of these remote places into human populations and then infect us and very likely the köppen 19 coronaviruses came from such a reservoir so poached the books that I'm actually reading now or read or read very frequently I just put here for you guys really the coolest thing here I think is this book by roger penrose okay so the road to reality it is not a light read now a number of you asked in the questions some questions about pursuing a career as a scientist a physicist or an astrophysicist and many of you talked about how the math is daunting or or even just asked what level of math you need so to quote Roger Penrose we cannot get any deep understanding of the laws that govern the physical world without entering the world of mathematics blah blah blah skipping forward in modern physics one cannot avoid facing up to the subtleties of such sophisticated mathematics it is for that reason that I have spent the first 16 chapters of this work on the description of mathematical ideas so this is a book this is like what do plain roses ultimate this is how the universe works and he honestly spends the first 16 chapters just giving you the background math so for anyone who wants the background math but you know isn't about to start a college degree Roger Penrose the road to reality the first 16 chapters would actually give you the grounding you know not not by themselves but they would they would show you what you need and you could you could go from there and direct perhaps your own study to get the grounding you need to understand relativity gauge theory all of this all this super mathematical stuff okay so so that's the answer to your question Roger Penrose is first 16 chapters all right so Roger Penrose is one of like my favorite all-time ever scientists another favorite all-time ever scientist is this guy Paul Dirac he's just so amazing so this is Paul directs biography the strangest man by grandfer mellow and just the the number of anecdotes about paul dirac the so in Cambridge that there were thing that Dirac's stories were think everyone had a direct story for you know some of their encounters with Paul Dirac no as an example when he first met the young richard fineman he it was at like a cocktail party and and it was a super awkward conversation because Paul Dirac was not the most verbose of all scientists he was a very physicist II okay he oh it was said of Paul Dirac that what or that he would he would not say one word when zero words would do there was also a unit of measurements in in Cambridge for the rate of speech where one Dirac equaled one word per hour so when Fineman comes up to him is like okay awkward silence awkward silence and then Paul Dirac says I have an equation do you have one - yeah so Paul Dirac had the direct equation which basically brought together all of quantum theory and you know it was in 1929 or there abouts predicted the existence of antimatter and you know eventually I should in quantum field theory yeah yeah he's amazing the theorists theorists they call him Einstein would always carry around his version of Paul Dirac's textbook on quantum mechanics and so when Einstein wanted to address a problem in quantum mechanics who he would be known to say where's where's my Dirac okay Paul Dirac so I'm a you an astrophysicist technically but I've had to learn a lot of quantum physics for this show I mean I learned it right I learned it in graduate school and and and but then you know didn't apply it for quite a while and so really had to come back to it I love my Sakurai okay which is a lovely treatment it's a little advanced but the the place that I started is this thing here Masaya quantum mechanics I wish I'd started with Paul Dirac Spock that but that's where I started that that requires a bit of math too but if you've read the first 16 chapters of Penrose you should be fine a book that's really close to my heart professionally is this thing astrophysics in a nutshell okay Dan Mouse so this is it's a graduate level book but it's insanely accessible for anyone who's okay with algebra and relatively basic calculus okay and you can see that it's very well worn it like I have three copies of this for all of the different places that I might want it it's just a beautiful beautiful like exposition of how we can derive the physical rules that govern Astrophysical events it's awesome okay Hawking in Penrose the nature of space and time somewhat pretentious title it's an OK read this is one that I really recommend to all of you this is very chewed up because well this is the house copy actually and she she got me onto this but this is Werner Heisenberg the so this publication is called physics and beyond but the original is called part and a hole or something like that but but this is but that Heisenberg is such he was a close friend of Paul Dirac that he's quite the opposite in personality he's very warm and and bright and poetic and philosophical and the the story of how he came up with I mean he invented quantum mechanics he did he got his stuff came before Schrodinger by a few months but he's he's a savant and I so I recommend physics and Beyond by Werner Heisenberg it's the story of his life also and and what it was like in those times when some of these great ideas were emerging it's in general good to not just read what you know modern people talk about this stuff so there's a good book by Einstein called relativity it's varying Lee a delightful read and extremely dry and Einstein actually says that he's not going to add unnecessary flower flourish or poetry to it because he wants it to be principally extremely clear and so if you're if you want to you know if you're down for that yet going to the original source is is a great idea I kind of just put this one up here because it was lying around the anthropic cosmological principle now this isn't we talked a lot about the cosmological principle recently and this is not your go-to source this is a book that came out later that kind of I think misinterpreted the original ideas the you know that about the logical sorry about the anthropic principle okay the idea that the universe that we when we try to understand the universe that we see around us we have to take into account that it must support observers like us okay that's there is an unavoidable observer bias in the universe that we observe okay and so I mean this is there's some interesting stuff in there anyway and this is just there because we were talking about it the black hole war okay Leonard Susskind had this famous bet with Stephen Hawking that about the conservation of quantum information or he thought that calm that quantum information would be destroyed in a black hole Susskind thought that it would not be a way to say that and ultimately Hawking of course seeded the BET and agreed that the quantum information could be preserved okay those are some books I asked you guys to let me know what you guys are up to during these harsh times I'm gonna take us back to our studio over here I'm carefully avoiding our piles of quartered toilet tissue framing is really everything in this game so so so this is what I'm doing I'm reading I'm building a concrete coffee table I'm working on this crazy clock puzzle that's one there going to be this cool wooden clock it's taking us a very long time to do it and drinking the grones what are you guys doing okay music yet so I'm gonna have my lovely assistant read me a few of these if that's okay blacksmithing damn now I'm jealous just learning film stuff here video games especially space ones video games we're gonna build a console into this coffee table I was originally planning to build a touchscreen like into the center of it so it could be all board games at once and then I realized that that was just like - tech bro nerd I should just build a coffee table first and then get to that stuff later learning code planting growing vegetables writing a piano concert oh wow okay so building a forge man I was like so excited to impress you guys with this stuff but waiting fancy novels okay alright impressive impressive I think let's see how we're doing I think we're gonna just answer a couple more questions and then we'll wrap up our first live stream we're already an hour and 10 minutes in okay one second okay so a few more questions from the live feed right here now I didn't choose these but I chose them for me and so this is going to be a fun game in which we see if I can answer things without any preparation I mean I didn't really have preparation for the previous ones but at least chose ones so in general relativity and quantum mechanics so Trevor asks both require observers why does science not take into the observer as a fundamental part of reality well I think so Brandon Carter who is I think the original guide the astrophysicist who came up with the anthropic principle would say that we must take the observer into account in the sense of the type of universe that we observe I think that John von Neumann and Eugene Wigner Vigna would say that the observer is essential because they collapsed the quantum wave function when a measurement is made and and both von Lehman and bigness seemed adherents to the sighting I believe that later on being was less convinced that the observer had to be a particularly a circle part or that the act of observation didn't have to be conscious however so so I think you know the answer to the question is that some people want the very act of observation to be fundamental I'm not convinced you know I think that something exists without the observer whether it bears any resemblance to how our brains process and construct that reality you know to present us with an image is highly debatable and certainly it's not completely so the real universe is very different to what we pursue to what we imagined it to be but even if we weren't even if we didn't exist I think something would be there so now we're getting down to the you know the interpretations of quantum mechanics and the the Vigna von Neumann rotation requires an observer you know of course the both the Dubrow Bohm and the pilot wave and also Everett's many-worlds do not require an observer observers are just emergent you know properties although we in our particular location in either the universe all the quantum multiverse defines what we see and so it's very important to take into account yeah I mean it's a super interesting question I think it comes down to the really some of the most fundamental questions about you know what is anything okay so another one okay so Charles watereth asks if time reversed direction for a while and then resumed how would we even know it happened wouldn't everyone's memory of those moments be unremembered so I think that's a nice way to put it if time reversed and went forward again what what would the effect be in a deterministic universe where every instant relies entirely on the previous instant for example in one of these cellular automata universes then rewinding it is just perfectly reversing those steps which will then proceed perfectly exactly as they did you know their first pass through and certainly nothing would be remembered and we wouldn't receive anything from it but that gets to a real kind of philosophical question you know what is time blah blah I think we'll do some more episodes on that but but what what would even mean to reverse time if you think in terms of what's called block time that that the dimensions of space and the dimensions of time in a sense just all exist space-time exists from the beginning of the universe to the end and we as observers over the universe kind of just like tracers world lines through that block time our conscious experience is just what happens when you trace a super complex path of many you know of the you know the patterns of the particles that make up our bodies through this four dimensional block space-time and so time moving forward does time with forward or backwards maybe not maybe this thing exists but our conscious experience is just a trace through that I would like to think of it in terms of playing a record okay so on a record this remember records CDs whatever okay the songs are there imprinted in the grooves of the record and they're always there and the whole song is there but the melody only emerges when you play the record in a certain direction okay you might then ask what is the needle of that record well I think they know he breaks down there but so so in a sense passing the to answer the question more succinctly you know rewinding and then going forward again may not actually have meaning okay the time just is okay okay so in the last minutes well first of all to wrap up the science there are two questions / comments that that I feel I must first of all been ill asks hi Matt hi Ben where do the fundament fundamental laws of nature come from thanks Ben you know I can't tell you that that that's obviously something we're saving for the last episode of space time in you know however long it's going to take us to get there you don't have to wait okay it's going to be more than ten rows and sixteen chapters where do the fundamental laws of nature come from I'm hoping we can keep making space time long enough that someone figures it out before we have to stop and one wife questions I can't find it maybe I'll find it later so the last thing I guess then is to talk about now what to do going forward and this was you know I'm inspired to think about this by Charles Copley's question which is that you say we need to know what is my favorite incarnation of the doctor dr. who that is and and so you know what were you going forward well we watch a lot of shows some of you came up with shows that you're watching in the chat or I'll mention a couple that that we are watching so I'm inspired by this question about Doctor Who and I will answer it because of the following so we started watching this show called devs devs and it you know it's a grits an amazing show it's about you know this tech genius who builds a quantum computer that does something that I can't tell you what it does but it involves a lot of cool talk about the interpretations of quantum mechanics is a debris boom is it Everett Everett's many-worlds and you know it's a fun watch it's very cool so this is a show by Alex Garland and I go onto it because our quantum physicist great Graham Cassell sent me a link to an interview in which Alex Garland is talking about his inspirations for the show and he starts saying oh and there's this I think he's an Australian guy and he has a beard and then they showed a clip of space-time so apparently Alex Garland watched or watch his space time and maybe got something because anyway it was it was very touching so Deb's you know and maybe maybe we played a small part that that some of the scienter is good you know they're really good discussions about determinism in quantum mechanics and you know and the different interpretations of quantum mechanics he took some liberties as you must but that I would recommend giving it a watch the reason though I bring this up is that you know although it you know it passed some time we found that kind of dark okay was it was it's quite an ominous show I can't say more but we realize that this these were the early days of the lockdown and we needed something uplifting and it was like what is uplifting Doctor Who Doctor Who is the ultimate like hope bringing series okay the doctor himself is you know such a cheerleader for Humanity and you know it's some of the episodes are soso some of the episodes are amazing but it but we found ourselves uplifted and after watching season six that's Matt Smith of Doctor Who we found we could go back and finish watching deaths okay so to answer your question my favorite doctor well I grew up with Tom Baker okay that ages me I'm Gen X sorry that you know I always thought no one grayble be Tom Baker and so crazy so colorful and none of the doctors after him it became close until David Tennant they date to me David Tennant really you know what Tom Baker was a genius he's very goofy though the David Tennant really brought the doctor to a new level and so so he'll always be the best doctor to me but you know I didn't have great hope for Matt Smith but after watching season six I use like making my equal second with Tom Baker you know and I can't even tell me about con Baker's just because you know I grew up with him I also think Jodie Whittaker did a fantastic job I think she was hampered by the writing of her series unfortunately the writing in in a lot of David Tennant's and a lot of Matt Smith's is just superb okay so the other thing that we're watching and that I strongly recommend is a little show called midnight gospel okay so write that down it's by what's-his-name [Music] by Pendleton ward who you you know him from adventure time obviously so it's very adventure time and in its animation and very science fictiony so you know it feels like you're watching a science fiction show except for the fact that yeah I'd only give away too much but it is deeply profound and it's yeah it really blew both of us away we watched it very quickly and I think we will watch it again it's artistically amazing so midnight gospel so I know you guys have been peppering the chat with your own recommendations and I'm going to go through those and because now we're actually done with midnight gospel we're done with Deb's I think hopefully you'll generate some more distractions for us oh yeah tales from the loop tales from the loop is the other one excuse me my anything for a minute but tales from the loop is this show it's it's so great but it's based on the art this artist Steinman's Stalin hug the electric state and and the vibe of it is the vibe of the electric state it's yeah check out tells from the loop okay so if anyone has to watch that alright so this has been a delight I feel like I'm not stuck in my apartment eternally so many great suggestions here so I had enough fun that I would love to do this again sometime maybe we see some more my place you know maybe when one day we do it one of your guys places I don't know but thank you so much for joining we'll keep making the show and now that we've realized that the past and future may be good but the prison it's actually a really cool place to hang out I hope to see you in the present again real soon so to end as always stay safe and blah blah space-time

Channel: PBS Space Time

Views: 282,538

Rating: 4.9242654 out of 5

Keywords: space, astrophysics, outer space, einstein, relativity, astronomy, cosmology, general relativity, black holes, black hole, Matt O'Dowd, PBS, PBS Space time, Space Time

Id: 9xIn1Ti7bz0

Length: 74min 15sec (4455 seconds)

Published: Tue Apr 28 2020

Reddit Comments

[u/R2c_one]

Literally tuned in right as he said "... Space Time.", then the stream ended.

[u/curiousscribbler]

Did we learn the name of the grey cat?

[u/[deleted]]

Dropping by to say thanks for all your work, me and my son watch your videos every night before bedtime, no idea why hes so fascinated as hes only 1! But glad he likes it too, means I get to watch ^{_^}

[u/caubrun8]

Ahhh I have such a pressing question

[u/samcobra]

TL;DW anyone?