Far out cosmology: Space fabric is like goo (Introduction)

by David Turell , Thursday, June 22, 2017, 15:01 (2709 days ago) @ David Turell

Einstein descried space as a space/time fabric. It acts gooier than that:

http://nautil.us/issue/49/the-absurd/what-is-space?utm_source=Nautilus&utm_campaign...

" Is space like an infinite void waiting to be filled? Or does it only exist in the context of matter?

"It turns out that we are fairly certain that space is neither of these things. Space is definitely not an empty void and it is definitely not just a relationship between matter. We know this because we have seen space do things that fit neither of those ideas. We have observed space bend and ripple and expand.

"If you are paying attention, you should be a little confused when you read the phrases “bending of space” and “expanding of space.” What could that possibly mean? How does it make any sense? If space is an idea, then it can’t be bent or expanded any more than it can be chopped into cubes and sautéed with cilantro. If space is our ruler for measuring the location of stuff, how do you measure the bending or expanding of space?

***

"To make sense of general relativity and think about modern ideas of space, you have to give up the idea of space as an abstract stage and accept that it is a physical thing. You have to imagine that space has properties and behaviors, and that it reacts to the matter in the universe. You can pinch space, squeeze it, and, yes, even fill it with cilantro.

"How can space be a physical thing that ripples and bends, and what does that mean?

"It means that instead of being like an empty room (a really big room) space is more like a huge blob of thick goo. Normally, things can move around in the goo without any problems, just like we can move around a room full of air without noticing all the air particles. But under certain circumstances, this goo can bend, changing the way that things move through it. It can also squish and make waves, changing the shape of the things inside it.

***

"And we know that space can expand because we have seen it expanding—this is how dark energy was discovered. We know that in the early universe space expanded and stretched at shocking rates, and that a similar expansion is still happening today.

***

" Light, for example, bends its path when it passes near massive objects like our sun or giant blobs of dark matter. If gravity was just a force between objects with mass—rather than the bending of space—then it shouldn’t be able to pull on photons, which have no mass. The only way to explain how light’s path can be bent is if it’s the space itself that is bending.

***

"Is it possible to have parts of the universe without space? In other words, if space is a goo, is it possible for there to be not-goo, or the absence of goo? The meaning of those concepts is not very clear because all of our physical laws assume the existence of space, so what laws could operate outside of space? We have no idea.

***

"If your brain is not yet hurting from all these gooey space-bending concepts, here is another mystery about space: Is space flat or curved (and if it’s curved, which way does it curve)?

***

"All the mass and energy in the universe is what gives space its curvature (remember that mass and energy distort space), and if we had just a little bit more mass and energy than we have right now, space would have curved one way. And if we had just a little bit less than we have right now, space would have curved the other way. But we seem to have just the right amount to make space perfectly flat as far as we can tell.

***

"Space can be flat and infinite. Or it could be flat and have an edge to it. Or, even stranger, it could be flat and still loop around itself."

Comment: Quantum space is also discussed. See the article. The cartoons are great.