This installment of our Biggest Ideas in the Universe series talks about Space. As in, the three-dimensional plenum of locations in which we find ourselves situated. Is space fundamental? Why is it precisely three-dimensional? Why is there space at all? Find out here! (Or at least find out that we don’t know the answers, but we have some clues about how to ask the questions.)
The Biggest Ideas in the Universe | 4. Space
This is likely one of my favorite Ideas in the series, as we get to think about the nature of space in ways that aren’t usually discussed in physics classes.
Update: here is the followup Q&A video. More details on Hamiltonians, yay!
The Biggest Ideas in the Universe | Q&A 4 - Space
Hello, I really like these videos. Some questions:
The question ‘why don’t we live in momentum space’ is really been addressed by physicists?
In string theory the space is necessarily continuous? What do you think about the possibility that space is discrete?
Are physicists considering other possibilities other than continuous and discrete for the space (not necessarily in string theory, maybe other theories)?
I am proposing in my coming book soon that space is a specific reality but it cannot be made of only 3 dimensions plus time. Three dimensions cannot comprehensively describe our ultimate realities including the fabric of spacetime because the three dimensional space is more than just spacetime.
In your entertaining discussion of the dimensions of space, you offered an analogy about the feasibility of shoe lace tying in third versus fourth dimension, suggesting that laces knots could not be secure in the fourth. I don’t recall any explanation that supported this assertion. Of course, three dimensional knots could fail with another free direction available in the next higher dimension, but what would rule out the availability of a fourth dimensional method of tying or securing?
Hi,Sean! Why did you say that when one of the entangled particles are measured, they will both have the same spin? Shouldn’t they have opposite spins? Thanks!
Lineu Miziara
Thanks for the wonderful videos!
Really enjoying your talks. Thanks for doing this!
Re phase space vs object space, can you comment the assertion that what makes spatial dimensions distict from and in some sense more fundamental than momentum dimensions is simply the fact that, at least as far as I know, fields spread only in spatial dimensions. To me, this seems to be more fundamental than and in fact the origin of locality.
Do the 3 dimensions of space have anything to do with the 3 dimensions of SU(2)? If the world is made from qubits (it from bit!), wouldn’t you need a 3-dimensional space for their transformations? It seems a spin-1/2 particle needs to live in a 3-dimensional space to realize all its spin directions.
Is there a sense in which all the tiny, wound up dimensions we can’t “see” but which are required in String Theory contribute to entanglement?
Could it be true that infinity and zero do not really occur in the natural world? You explained that energy is a concept whose role in nature is not necessary to explain the natural world. Does physics require that infinity be part of reality, or can we say that an equation with singularity at conceivable parameters fails to describe reality at that point?
Related to Change and Spacetime: how does the fact that we are moving with certain velocity in the solar system (and in the universe it self) affect out measurements? How could we define rest mass if we are always moving?
Thank you for delightful little chats, as you call them.
To what extent may we consider that an experiment such as Gravity Probe B proves beyond doubt that space is a “thing”, a substance, made of stuff not accountable by the standard model?
Sean, have you any thoughts on Stephan Wolfrsm’s physics project?
https://www.wolframphysics.org
Does it have any similarities to your ideas about spacetime and quantum mechanics?
I love the idea of a donut-shaped space with strings wrapped around it tying up a microscopic dimension in a way it becomes unnoticable to a macroscopic observer. In your fourth video on “The Biggest Ideas in the Universe” you describe two of these strings reconnecting as they collide and instantaneously releasing their tension. I have two questions about that:
1. When we think of strings as rubber bands, where does their tension energy go as they contract?
2. Is this the way we might understand the inflationary expansion phase of the universe?
The world is made of fields – so much for the first part of “in truth, only atoms and the void,” then. Once Sean tells us about dark energy and the cosmological constant, the “void” part will also be – sorry but I can’t resist – void.
This presentation is very cool. I’ve been taught Hamiltonians before, but this actually fits them into a bigger picture and thus makes them more intelligible.