Lee Smolin - How Can Space and Time be the Same Thing?

the space and time are things that we take for granted but we've been told and we're starting to believe that what einstein said that space and time are not quite as they seem but they're dynamic they're mobile they can curve they can slow they can they can expand and uh but the two are really unified together and we need to un to understand space-time is critical to understand the nature of our universe it's the most important question okay so what is time what is space okay even more important than what are the particles and what are the forces and we want to understand everything so it's it some people have thought of it is it's the arena in which all the act of particles and physics play out but it may be more than that the basic division in the subject goes back a long time it goes back to debates between newton and his contemporaries leibniz and other contemporaries and the big question is is space an arena in which things happen in which things come on and off or is there no arena is space just a network of relationships a way to ask the question is if the whole universe were moved entirely 10 meters to the left would it matter does it even mean something to say that because no relationships would change and newton said yes it is different and leibniz said no it's even wrong to ask the question because there's no discernible difference between the universe here and the universe 10 meters to the left and this very question of whether space is a framework an absolute background or whether space is an aspect of reality that grows out of a network of relationships of causality of change is the fundamental question as has been for 400 years okay so if we're trying to understand the nature of space at this point we're dealing with different concepts as well we're dealing with relationships yes we're dealing with causation yes and so those are very fundamental ideas but what you're saying is that to understand space we may have to understand those other two which may be more fundamental than space itself yes and indeed one can take general relativity and if you ask what in that sophisticated mathematics is it really asserting about the nature of space and time what's asserting what's it what it is asserting about space and time is that the most fundamental relationships are relationships of causality this is the modern way of understanding einstein's theory of general relativity and so if you think about the structure an event happens and light goes out of it we have these pictures of light cones going out and if your travel from there as light goes out over time at the speed of light it covers in greater and greater distances imagine a sphere going out right now if a later event happens within that sphere information could have reached there from the first event going at slower than the speed of light and so there could be a causal relation there will be a causal relation between the first event and the second if another event is so far away that light could not have gotten there then there's no causal relation and the interesting thing is if you write down a list of all the causal relations between all the events in the universe you describe the geometry of space-time almost completely there's still a little bit of information that you have to put in which is counting which is how many events take place so we don't have everything so whereas the common perception is that we have space and in the space there are relationships like my chair in your chair or there are causes that i push your chair and you you you move a little bit that that that is an artificial distinction that maybe it's the events themselves that create the concept of space yes yes i mean and that's not just a metaphor it's the best way of understanding both the principles and the mathematics of einstein's theory of general relativity now this sounds very profound are are there uh implications of this that you can say okay if that's if that's true then what follows what what would then happen that we can see an observation or learn about our world or is this just some philosophical idea for example the whole idea of what a black hole is comes from thinking about the causal relations a horizon is a boundary to what can be causally influenced by what's quote inside the black hole so if you want to really conceive of what a black hole is you have to think of it in terms of causality and causal relations the idea of the singularity at the beginning of the universe that space and time cannot be continued beyond a certain set of events came from thinking about the causality this was a kind of revolution in our understanding of gender relativity brought about principally by roger penrose in the 1960s okay so now we have sort of this new concept of space as perhaps an emergent property of relationships and causes between events now let's bring time into it because but time is already in it because causality is okay time because causality is is a sequence is causality is a sequence so so what you're saying is that time then is uh is also emergent because once you have the cause time is a natural product of that as opposed to time being something that we flow through yes if you take that point of view then causality is the fundamental aspect of time and the our experience of the flow of time is a product of that uh derivative a derivative of that okay okay now can you keep then space and time is is that one unit einstein's so-called block universe where every event had a three-dimensional location and a location in time so a four-dimensional piece so you can see the whole history of the universal beginning to end supposedly in this four-dimensional block universe where time is a coordinate you know from the point of general relativity classical general relativity you can have it both ways you can think of this black universe picture which you mentioned and you can get away with that to a certain extent when you bring in other questions about how quantum mechanics fits in to the whole picture about how thermodynamics fits into the whole picture in entropy i think it gets harder to maintain this black universe picture and for me this is one of the profound issues the issue is is time really fundamental so that it's the one thing that's not emergent or is time somehow emergent or a consequence of other things and of course we don't know the answer but different approaches to the fundamental questions about cosmology about quantum gravity line up on different sides of those questions and this is something i've been thinking about myself a great deal and i've been finding personally i'm thinking more and more in the direction that time is fundamental is not emergent differentiated from space yes so you are teasing apart space and time because in quantum gravity sounds quite radical sure it is but it's also maybe the most conservative solution to a set of conundrums that we face when we try to bring together quantum theory and gravity because the other alternative is that time goes away completely and in the view the time goes away completely and time is quote emergent then one imagines a world and and julian barber is the person who's best explicated this idea the world is nothing but a vast collection of moments with not necessarily any relation amongst them the the relations of time of causality dissolve and is just disconnected moments and this does represent a proper interpretation of certain mathematical approaches to quantum gravity but these approaches they succeed to a certain extent and then they fail they failed for technical reasons so i don't think i have to go into that here but when a problem confronts here's an interesting thing about being a theoretical physicist a lot is a matter of judgment and when you face a problem where you make technical progress on some aspects and nobody makes technical progress on some other things there comes a moment when you say is that over here really a technical problem or do we just have a conceptual misunderstanding are we conceiving of it the wrong way and that's why we can't make any technical progress that's what you think about that's what i think about time

Channel: Closer To Truth

Views: 259,090

Rating: 4.8975258 out of 5

Keywords: closer to truth, robert lawrence kuhn, lee smolin, quantum mechanics, quantum gravity, spacetime, time and space, space and time

Id: QOAcQCFNtbo

Length: 9min 18sec (558 seconds)

Published: Sat Apr 03 2021

Reddit Comments

[u/watersucks99]

Sometimes I think I’m smart and then I see this shit. I’m like oh yeah your just a fucking average dude. This guy is in a whole other universe .