The title of this blog post is a question posed on the cover of the February 2022 issue of Scientific American. It refers to a story in the issue, "The Origins of Space and Time."
I enjoyed the story, even though it was difficult to understand.
Here's an image that encapsulates the two main approaches to figuring out what space and time (or as relativity theory puts it, spacetime) emerge from -- assuming they emerge from anything.
So if you were expecting some explanation that could be fit, or crammed, into a religious or mystical worldview, expect again.
Science of this sort is complicated, mathematical, provisional. Currently there's no way to test whether space and time emerge from something more fundamental. But just raising that possibility is fascinating, since most of us view space and time as fundamental realities themselves.
One reason physicists are pursuing this issue is that while quantum mechanics and relativity theory are both fantastically accurate depictions of reality, quantum mechanics focuses on the very small and relativity theory on the very large.
Plus, quantum mechanics does an excellent job of explaining three forces of nature -- weak, strong, electromagnetism -- while relativity theory does an excellent job of explaining the fourth, gravity.
It's too simplistic to say that three are more than one, so that's why physicists are interested in finding a quantum theory of gravity, but probably there's some truth to that. Relativity theory isn't capable of explaining the other three forces, so the goal is to find a quantum way to explain how gravity works.
It is indeed strange that so far quantum mechanics and relativity theory aren't compatible with each other, even though each is amazingly successful at explaining the realm in which they operate.
Hence, the appeal of finding a theory of how spacetime emerges from something more fundamental, which would demote relativity theory into a non-fundamental theory and, hopefully, bring about a understanding that explains gravity without using relativity theory.
Here's how the story starts out:
Natalie Paquette spends her time thinking about how to grow an extra dimension. Start with little circles, scattered across every point in space and time -- a curlicue dimension, looped back on itself.
Then shrink those circles down, smaller and smaller, tightening the loop, until a curious transformation occurs: the dimension stops seeming tiny and instead becomes enormous, like when you realize something that looks small and nearby is actually huge and distant.
"We're shrinking a spatial direction," Paquette says. "But when we try to shrink it past a certain point, a new, large, spatial direction emerges instead."
Paquette, a theoretical physicist at the University of Washington, is not alone in thinking about this strange kind of dimensional transmutation. A growing number of physicists, working in different areas of the discipline with different approaches, are increasingly converging on a profound idea: space -- and perhaps even time -- is not fundamental.
Instead space and time may be emergent: they could arise from the structure and behavior of more basic components of nature. At the deepest level of reality, questions like "Where?" and "When?" simply may not have answers at all. "We have a lot of hints from physics that spacetime as we understand it isn't the fundamental thing," Paquette says.
These radical notions come from the latest twists in the century-long hunt for a theory of quantum gravity. Physicist's best theory of gravity is general relativity, Albert Einstein's famous conception of how matter warps space and time.
The best theory of everything else is quantum physics, which is astonishingly accurate when it comes to the properties of matter, energy and subatomic particles. Both theories have easily passed all the tests physicists have been able to devise for the past century. Put them together, one might think, and you would have a "theory of everything."
But the two theories don't play nicely. Ask general relativity what happens in the context of quantum physics, and you'll get contradictory answers, with untamed infinities breaking loose across your calculations. Nature knows how to apply gravity in quantum contexts -- it happened in the first moments of the big bang, and it still happens in the hearts of black holes -- but we humans are still struggling to understand how the trick is done.
Part of the problem lies in the ways the theories deal with space and time. While quantum physics treats space and time as immutable, general relativity warps them for breakfast. Somehow a theory of quantum gravity would need to reconcile these ideas about space and time.
One way to do that would be to eliminate the problem at the source, spacetime itself, by making space and time emerge from something more fundamental.
Physics told us long ago that solid objects were largely empty space and only appeared solid because of the fields of energy and particles holding them together.
Spooky physics taught us that linear space and linear time don't always function that way.
The big bang theory, at least one variant, states that the universe started as a particle infinitesimally small, but of nearly immeasurable density.
And mystics claimed this reality is largely a projection of another reality.
We still don't really know what gravity is. We can measure its effect on other things, understand its connection to matter, space and time. It functions like a property of matter, but it could be the other way around, that matter is a property of gravity. Or a property of space. Or something deeper.. Interlaced strings or a mesh of distinct loops forming a kind of space time foam.
Gravity works across millions of miles of empty space connecting matter with no visible or measurable strings. No energy or particles that could be called gravity have ever been detected. Only its effect on other things.
This brings up the fundamental mystery of the physical universe and while theoretical physics is hard at work uncovering more of that mystery, and successfully, at this point science has proven that as much as we have learned, there is even more we never had a clue about that we don't know. Today we know more than we did, and even more about what we don't know. Hail Science!!
All good scientists honor the mystery.
Posted by: Spence Tepper | February 02, 2022 at 05:14 AM
This piece from Scientific American begins and ends with: - " . . . making space and time emerge from something more fundamental."
I find this whole issue very complex, but in a limited non-academic way I understand the inflation theory a little more. Brian Cox (below) makes the 'emergence from something more fundamental' reasonably credible.
With the origins of the universe in tow, Prof Cox flipped the Bible creation story to tell what he coined the "science creation story".
He said: "In the beginning there was an ocean of energy that drove a rapid expansion of space known as inflation.
"There were ripples in the ocean.
"As inflation ended, the ocean of energy was converted into matter by the Big Bang.
"And the pattern of the ripples was imprinted into our universe, as regions of slightly different density in the hydrogen and helium gas that formed shortly after the Big Bang.
"The denser regions of gas collapsed to form the first stars and the first galaxies.
"And nine billion years later, a new star formed in the Milky Way: the Sun.
"The star was joined by eight planets including Earth.
"And, nearly 13,8 billion years after it all began, we emerged, blinking into the light."
Last year, Sir Roger Penrose argued a similar theory for the beginnings of the universe as he re-ceived his Nobel Prize for Physics.
Winning for his work proving that black holes exist, he said he had found six "warm" points in the sky, which he called "Hawking Points" after the late physicist Stephen Hawking, who theorised that black holes ‘leak’ radiation and eventually evaporate away entirely.
These points, he explained, were around eight times the diameter of the Moon.
The timescale for the evaporation of a black hole is on a huge scale, potentially longer than the age of our universe, making them impossible to detect.
But, Sir Roger believes that "dead" black holes from earlier universes or "aeons" are observable now.
If this is true, then Prof Hawkings' theories and life's work will be proved correct.
Sir Roger said: "I claim that there is observation of Hawking radiation.
“The Big Bang was not the beginning.
"There was something before the Big Bang and that something is what we will have in our future.
“We have a universe that expands and expands, and all mass decays away, and in this crazy theo-ry of mine, that remote future becomes the Big Bang of another aeon.
“So our Big Bang began with something which was the remote future of a previous aeon and there would have been similar black holes evaporating away, via Hawking evaporation, and they would produce these points in the sky, that I call Hawking Points.
Posted by: Ron E. | February 02, 2022 at 07:28 AM