The Other Side of Physics | Sabine Hossenfelder | TEDxNewcastle

physics describes the behavior of matter in space and time when we get to learn physics at school we get to know it as a discipline that describes the behavior of inanimate matter it tells us how lights work how atoms Decay or how rocks fall we don't think of physics as a discipline that tells us a lot about ourselves unless possibly that if you fall out of a window you fall pretty much like a rock but physics is so much more than this physics deals with the most fundamental laws of nature that describe the behavior of Elementary particles that everything is made up including us and yes that means that if we fall we fall pretty much like rocks but it also means that physics is the most powerful tool that we have to make sense of our own existence it's a tool that allows us to answer questions like how do we get here what can we do what can we know what are we made of and often it's given us surprising answers for example Einstein's theory of special relativity has taught us that the passage of time depends on how much you accelerate acceleration is a change of velocity and velocity does have a direction this means if you change direction for example by walking in a circle you accelerate and that slows the passage of time which means if you run in a circle you'll age slower that that's not a joke it's actually true and it's been measured not for people who run in circles but for airplanes that go around Earth but it's an extremely tiny effect for the velocities that we can move with so if you spend your whole life running in a circle you might save a few nanoseconds but maybe that's not how you want to spend your life Einstein's theory of special relativity has taught us a lot of amazing things but for me one of the most surprising things is that it has told us that our perception of this present moment of now as something special is entirely subjective it doesn't exist in the fundamental laws of nature to understand why I say this ask yourself whether I'm here now well you might say well that's kind of a weird question that only physicists can ask but the answer is not obviously yes the reason is that Einstein's theory of special relativity is based on the observation that the speed of light is not infinite it's finite and it's the same for all observers and nothing can go faster than light so by the time you see me standing here I've actually moved on into the future you only see me as I was a little bit in the past and yes it's a really really tiny delay but you have this delay to everything you see around you everything you see you see it as it was a little bit in the past and because no information can travel faster than the speed of light there's no other way that you can find out what really happens now so that's a little bit disturbing you might say well but by the time that the light arrives at you you could try to reconstruct say what you were doing when I was talking about rocks you could say well at this time I was just scratching my head because you know what the speed of light is and you could measure the distance to me and then you can figure out what happened simultaneously the problem is that if somebody else does that who's walking through the room they get a different result because some of the light would come out at them and it would take a little less time to arrive at them and some would come from behind it would take a little bit longer so they would reconstruct different things to happen at the same time this is what's called the relativity of simultaneity different observers come to different conclusions about what happens at the same time that's true when we're talking about the past and it's also true when we're talking about the presence there is an Einstein's theories no way to reconstruct a moment of now that everyone agrees on this notion of now that is so integral to our experience is entirely subjective it depends on the Observer this also means that your now could be somebody else's past or somebody else's future as a consequence the past and the future in Einstein's theories exist exactly in the same way as the present moment it's called The Block Universe because the block universe doesn't come into being it just sits there like a block already in place what's it mean well I don't know to be honest it's one thing to understand what the mathematics says and it's another thing entirely to interpret the mathematics I think what it means is that we are beings inside of space and time we don't see the full picture we think from one moment to the next we don't see how the universe has evolved and will continue to to evolve we don't see this entire big universe that we are part of physics has not only given us some surprising answers to questions that we might have asked it's also a source of inspiration think about how often you encounter in movies or in science fiction literature Concepts that have come out of physics there's the Multiverse there are wormholes time that slows down near black holes it's all physics really it just uh the way that those topics are portrayed in movies or in the literature is shall we say a little bit more exciting than they appear in the scientific literature take for example the Multiverse that's the idea that there are other universes besides our own that we cannot observe and not interact with the Multiverse does appear in some of the mathematics that we encounter in the foundations of physics but in in those multiverses you cannot travel between the universes we're stuck in our own those are the universes are completely disconnected from ours so we can't observe them we can't interact with them and we also can't test that they are there but mathematically there are copies of our universe and of our planets with minute alterations so each possible decision that you could have made was made by one of your copies in one of those other universes had chicken on the plane well in some other Universe you had the noodles in one of those universes you won a Nobel Prize in some other Universe you became prime minister maybe it's this one so you could say but wait if we can't interact with those universes if we can't observe them if we can't measure them then that's not scientific and that's right but just because it isn't scientific doesn't mean it's wrong there's no observation that can refute or confirm the existence of those other universes but we can't rule them out either I like to call such ideas a scientific that's a word which was coined by my friend Tim Palmer and when he came up with this I thought that's brilliant I'm totally going to steal this and I'll travel around and show off his word I hope you'll forgive me so the distinction between a scientific and unscientific is similar to the distinction between an atheist and an agnostic The Atheist doesn't believe in God and agnostic has no opinion about it in a similar sense unscientific means you believe in something that conflicts with the scientific method could be for example that if you dance that'll make it rain you can test it it doesn't work evidence speaks against it an a scientific idea to the contrary doesn't have evidence that speaks neither for nor against it for example the existence of copies of you in those other universes it's a science compatible belief another example of such a science compatible belief is that information is Immortal in some sense now information is one of those terrible words that is used in 50 different definitions overall fields of science for our purposes information is just all the data you need to specify a system at one particular time could be for example the solar system where it would be the mouses and initial positions and velocities of the planet could be all the data about the elementary particles that make up you now turns out that all the fundamental theories that we know work in a particular way which is that you take the state of the system at one particular moment of time then you have an equation that's also called an evolution law and from that you can calculate what happens at any earlier any later time the interesting thing about those theories is that you can do this forward and backward it's a one-to-one Association what this means is that the information in the state of a system it's reconfigured but it's never destroyed we don't experience this in practice if you say you burn a book for practical purposes for your practical purposes that destroys the information in the sense that it's no longer retrievable but according to the mathematics of our theories the information about the book that you burnt is still there it's contained in very tiny correlations between the atoms in the dust and the ushers and maybe the photons that came out that's all fundamental laws we know except for measurements in quantum mechanics and black hole evaporation in which we don't really know what's going on so to make a long story about this short you can pick either believe you want it's either distraught or it's not destroyed and physicists would buy it so um what this all means is that the information becomes irretrievable but it can't be destroyed it's something that we can't prove but it's compatible with all that we currently know another big thought so I was I was announced as the big thinking physicist so I'm trying to do my best to live up to that expectation is that the Universe can think and let me be honest when I talked about this the first time I think a lot of my colleagues thought all zabina has finally totally lost it but look I'm not saying that the Universe does think I'm saying everything that we currently know about the universe is compatible with the idea that it can think if you look at the universe from far distance then you'll see that the distribution of matter in the universe looks a little bit like the synopsis and Connections in the human brain that's galaxies Galaxy filaments and so on and so forth and that certainly suggestive but there's a very Sim simple argument for why the universe can't think which is that it's simply too big it takes a lot of time to send one single signal from one side of the universe to the other and that's leaving aside that we don't observe any such signals so even if the universe could think with all those synapses that will be the galaxies it wouldn't be able to do a lot of thinking that's the standard argument that argument has a big gap which is that it relies on Einstein's theory for Gravity which is general relativity and that theory is not compatible with the theories that we have for meta for the particles that live in that space-time which all have Quantum properties that they have Quantum properties means among other things that they can be in two places at the same time we also know that those particles have masses and masses generate a gravitational approach which brings up the question if you have a particle that's in two places at the same time where does the gravitational pull go well we don't know because Einstein's theory of generativity doesn't have Quantum properties so embarrassing as it sounds we actually don't know what the gravitational field is of a single particle what's all this mean well it means that we need a new theory for the behavior of space and time and gravity that theory which we still don't have is called quantum gravity in this theory of quantum gravity space and time can do wild things it can for example be sprinkled with non-local connections that are kind of like teeny tiny wormholes that can connect one end of the universe with the other and that can facilitate a lot of information exchange faster than the speed of light instantaneously it would give the universe a lot of connections through which it could interact with itself those tiny connections are too small for particles to go through we know this because otherwise we'd already have noticed but it does connect the universe with itself is that enough to allow the universe to think well we don't know to begin with because we don't actually know what Consciousness is but it certainly gives the universe a lot more connections than even the human brain has and this idea of those non-local connections has come up in various research topics in the foundations of physics I myself haven't worked on it I'm not that crazy but I want I want to make this clear that I'm not saying that there's any evidence that this is actually the case there's no evidence for those connections and there's no evidence against them it's compatible with all that we currently know that the Universe can actually think don't worry if you didn't totally understand what I was talking about I've been thinking about this for 20 years and just Among Us I don't totally understand it either but I hope I've given you something to think about and that I was able to explain what I mean when I talk about the other side of physics [Applause] [Music] [Applause]

Channel: TEDx Talks

Views: 114,992

Keywords: Big problems, English, Life, Physics, Science, Space, TEDxTalks, [TEDxEID:38497]

Id: Yx1k8q6PnWU

Length: 15min 49sec (949 seconds)

Published: Fri Dec 09 2022