If I understand correctly, space is what supports matter? Like a table supports dishes for instance (well, except that space is also "inside" particules) — and so if the table grows, the dishes don't.
I never actually even thought of what "space" means before. I thought that when we talked about space, matter was included in that (in the sense that quarks or whatever is the smallest — known? — particle take some "space" ; they're not points that can't be measured — or are they? ^^').
Anyway, it sparkled back an old interest of mine for astrophysics (well, I read one book from Hubert Reeves when I was a kid — and loved it).
Thanks again :)
(oh, as an added bonus: I guess we have no idea _why_ space is expanding, right? Because, I mean, it's a bit mind boggling...)
Edit: to be a bit clearer; I thought space was just void that "always" existed and extended indefinitely. Like, there was nothing except a small point with all the energy in the universe ; "everywhere" else a bit nothingness. Then, bim, the big bang, and matter was just booming away and making stars and planets and then galaxies and all that was just floating in this void/nothingness that was always there, never changing, still extending indefinitely. And that was why we were saying the universe was expanding — because galaxies were still speeding away from each others due to the big bang ; like an explosion with no friction perpetuing indefinitely. Now I guess I'm really confused about what "space" is...
The weird thing about the Big Bang is that it's really all of space that banged, and to a first approximation, space and time as we know it didn't exist before a singularity at the beginning of the expansion. It's very possible that's wrong (there may have been a "parent universe" or a "big bounce") but to a first approximation it seems to be that there may not have been a "before" the Big Bang.
So fine, but then why would we say that space is expanding, that would seem to imply we know there is some edge of space which is moving away from us, but what evidence do we have that space has such an edge?
Saying that "space is expanding" seems to hold the assumption that space has a (limited) width and height.
This makes me uneasy about your analogy. It’s like saying “relative to space” which is nonsense. Also, why would space limit itself to only expanding outside a physical body?
It is equivalent to asking why a car driving towards me does not turn blue due to doppler shifting. Except even more negligible than that.
Edit: the pearl is made from around bound by electric forces, so you can repeat the same argument for inside the pearl. You can repeat it all the way down until you have to admit that the approximations inherent in the concepts useful to describe the world at distances from nano meters to mega parsec eventually break down.
It doesn't, it's just that the forces within the body (the spring in the analogy) are stronger than the expansion.
The "relative to space" bit is the nonsense part of their analogy, but I'm not sure of a clearer way to describe things than what they did. It's not my field.
The mathematically precise statement is that you are not moving on a geodesic. You are therefore experiencing acceleration (the objects that are not bound and have increasing distance are on geodesics and do not experience acceleration).
But the expansion of space does "stretch" light- or at least, the wavelength gets longer, so it's not not happening.
It can actually end up making things very far away appear to move faster than light away from us, since there's a lot of space in between.
We cannot measure distance to super far away stars directly. Period.
10^-17 m/s is very high speed. Distance to Moon is 0.385E15 mm, and it can be measured at sub-millimeter accuracy, so this effect can be spotted. However, it will violate Conservation of Energy principle: no force applied, but job is done.
You don't have the decency to try to learn the basics but presume to lecture me/expect explanations? Take a course. Show a little humility. Even reading Wikipedia thoroughly would have informed you that it's galaxies, not stars that confirm the expansion of the universe. The expansion (not the acceleration of the expansion) is beyond doubt. Conservation of Energy is not a priory defined for the question at hand because in GR you can not just add the energy at different points in space.
Measuring the perturbation to the moon's trajectory from expansion would require knowing all parameters that enter the trajectory to this accuracy, not just the average distance.
This is all basic if you want to learn, but you seem to have a different agenda...
TLT predicts that value of "Speed of expanse" will be different when measured using different methods or frequencies, and it is: https://en.wikipedia.org/wiki/Hubble%27s_law#Measured_values... .
TLT predicts that there is much more stars, but we cannot see them yet because they are too dim, but more powerful telescopes will be able to pickup them. https://en.wikipedia.org/wiki/Tolman_surface_brightness_test https://www.nasa.gov/feature/goddard/2016/hubble-reveals-obs...
TTL predicts stars and galaxies older than BB (because of no BB), and they are found: https://en.wikipedia.org/wiki/List_of_the_most_distant_astro...
TTL predicts that Cosmic Background Radiation is just radiation of distant objects with Z=1000 .
And so on.
In short, mainstream theories doesn't hold against new data.
Tolman surface brightness test now looks much brighter. ;-)
Can we discuss something easier?
Why you think that photon is immortal? Why we have rule of right hand in EM? Why we see star formations older than BB? WTF is "physical vacuum"? What is waved by gravitational waves? What is happen in linear Sagnac interferometer? How photon is formed (it requires FTL to form)? What happens in double slit experiment? And so on.
Nothing is hidden, but it does take time and persistence.
Photons are not "immortal" they can decay if they have enough energy. Rule of right hand is a convention, could be left hand if you define the sign of charge differently. We don't see star formation older than BB but early universe physics is not easy to understand and there are lots of model uncertainties. Physical vacuum is what remains when no excitations are present. Gravitational waves are ripples in space itself. I don't understand what you mean by photons being formed.
You can not expect the concepts and intuitions that you formed by interacting with the macroscopic world to serve you well when thinking about the microscopic and fundamental. People used to think that you need some type of material aether that carries the waves of light. But that turned out not to be concepts that map well to reality. It took decades to learn to unthink these concepts, there is no shortcut to doing so yourself.
Expanding space doesn't necessarily imply edge of space. What if your universe isn't flat, what if it's a torus? It could hypothetically have a finite volume but no edge.
There's also no reason an infinite universe couldn't have local expansion everywhere.
Think of the changing pressure. If the box is tight and rigid and the pressure outside the box increases, the box will roughly stay the box until the pressure overcomes the the forces between the molecules that build the walls.
Same with space. If you could measure, the increase in the volume of space would put a constant pressure on every molecule to try to rip it from other molecules. The fact that the rate of change of space and the distances between molecules are so small means that it is not evident that it will ever be possible to devise an experiment to show this on very short distances.
We can only see this on very long timescales and between objects that are very far from each other because all other forces on those scales have diminished so much that only then the increase of volume of space can dominate.
This scales up to forces in between atoms, molecules, and bits of matter. It's only at the very large scales (larger than galaxies) that all the forces that are holding the stuff together starts getting overwhelmed by the expansion of space and it starts to pull things apart. The expansion is so gentle that even relatively weak gravity can hold galaxy clusters together even as space grows.
In other words: space gets bigger, but matter doesn't. It more or less stays the same size.