eli5: If space is expanding faster than light in all direction. Why hasn’t the space between our atoms expanded to infinite?
In: 530
Short answer is this WILL happen, just in billions of years. It’s constantly expanding, and the expansion is accelerating, but the timeline of the universe is so massive that we have just been here for the tiniest blip of time
I saw this explanation on another ELI5 and it was really nice so I shall use it here;
Let us imagine 4 evenly spaced objects in space, A, B, C, and D. Here is a visual representation:
A-B-C-D
Now I shall expand space (every dash becomes 4 dashes)
A——B——C——D
From the point of view of object A, object B has only moved away by 3 additional dashes. However, object C has moved away by 6 additional dashes, and object D has moved away by 9 dashed! For object B, it is A and C that has moved by 3 dashes, and D that has moved 6.
So it seems the farther an object is in space, the faster it seems to move away.
For the atoms in our bodies and other such objects, they are very very close to each other. They do move apart while space expands, but the distance they move is very very small, and they immediately come together due to the electromagnetic force, gravity, etc.
Maybe it is, we don’t have anything to compare it to. If we don’t know how it works, we don’t know where it’s going. A donut starts in the center goes out then returns to center.
Could the Heat death happen before the Big Rip? And if so would that have any effect on the expansion of space?
I thought science agreed that the universe was already shrinking in the middle of its oblong shape, and considered that the universe would split like an egg undergoing mitosis (as one of a few options, like decrease in expansion altogether and reforming a singularity)?
Space isn’t expanding at a speed (distance per time), so you can’t compare it to a speed like the speed of light. Space is expanding at a rate (proportion per time).
What that means is that if you imagine three galaxies in a line, `A-B-C`, after some time, expansion will increase the spacing to `A–B–C`. The distance between A and B increased by one dash, while the spacing between A and C increased by two dashes; the speed at which A is moving away from C is twice the speed at which A is moving away from B, because the distance between A and C is twice the distance between A and B.
To get a speed from the expansion rate you need to multiply the rate by the current distance between the objects.
Back to “space is expanding faster than the speed of light”: the correct statement is that there are things far enough from us that they are moving away from us faster than the speed of light. Expansion isn’t ripping atoms apart or doing other very noticeable-to-humans things because the current rate of expansion is so low that at the scale of atoms, or even at the scale of our solar system, the increase in distance due to expansion is negligible, and it’s overcome by other forces.
We are observing that the rate of expansion is itself increasing, so if it keeps increasing there will be a time when even atoms will be torn apart by expansion, but that’s not for a long while.
Maybe it’s me but it seems everyone is misreading the question? My ELI5 answer is space between our atoms is expanding (not at the speed of light though) but the force holding atoms together, electromagnetism, is strong enough to hold the atom together. Similarly the nucleus of an atom is held together by the strong force.
not just the space between the atoms would expand, but the atoms themselves would expand. How would we know if it had? There’s no absolute measure of this.
What the hell…are we?
It isn’t, at least not out to the horizon of what we can see. In any case, the “speed” of expansion is related to how far away you are from a point in space. If you look out one light year, space might expand (this a totally made up speed, not at all close to the actual speed that is happening) 1 meter in a second. Meaning each second you are looking at it, that point is 1 meter further away, then 1 more further again and again every second. But go out another light year past that, a total of 2 light years in a line, and there is an additional meter, that is, 1 more meter of new space in each of the two light years.
Saying that space is expanding faster than the speed of light means that more new space is created in a second than light could travel across in that second. It’s not a direct measure of how fast space is expanding, it’s a measure of how far away you have to look before light can no longer ever reach you from that point because the light will never have enough time to reach you.
Latest Answers