I understand how they can tell how big a planet is or how hot a star is. The thing I don’t understand is how do they know the universe is expanding? We cant see the edge of the universe also things are moving away and towards us. So how do they know its expanding? Also, what is it expanding to? For example, at the edge of the universe, is there a wall or is there complete nothingness? Like what is it expanding towards?
Edit: hopefully I used the right flair. I wanted to use “Astronomy” but there isn’t a flair for that
In: Physics
Edwin Hubble discovered that there was a redshift of light coming from far distances. This redshift phenomenon is caused by space expanding stretching out the frequency of the light reaching us causing it to go from the higher energy blue spectrum to becoming red and having a lower energy frequency then when it was emitted.
The reason space is expanding is a bit more unsure, it is normally said to be caused by something called dark energy. Dark energy is as I know
antimatter and (positive) regular-matter particle collisions, the energy of these ‘quantum fluctuations’ creates some extra energy causing space to expand. The more empty space the more expanding, as you may have already heard space is expanding exponentially.
The thing we are expanding towards isn’t anything we aren’t really going towards anything else then the future.
It is only the distance between stuff that is increasing. It’s the nothingness that is growing. If you went in a straight line off earth and all the way around the universe you would end up where you started, like a globe, a lot like earth actually. Except you are not looping back over the curve of the earth. You are moving over the curve of the gravitational pull on your trip, over the grid of spacetime.
You can not get outside the universe, it is everything we can observe. Not everything, but the whole observable thing.
The destiny of The Universe is therefore a bit harder to predict. Can gravity win over the expanding space?
We aren’t sure. There are many funny predictions of how the universe will end.
It will not be soon atleast.
Because of the expansion we can predict what happened In the early universe, currently being pretty sure about the Big Bang. We measure disorder since the “before picture” of Big Bang and now in disorder, also called entropy. As The Universe expands entropy increases and the distance of the stars turn light years as the stars explode into black holes.
If you actually read this far you are swag..
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