The observable universe. Does it mean the edge of space where nothing else is? Is it where the universe is currently at in its expansion after the big bang? Or is it just a barrier that our telescopes are yet to look beyond, and there are just more galaxies past it?
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Because the speed of light is finite, and the universe is only 13.8 billion years old, light from further away than 13.8 billion light-years needs more time than the universe has been around to make it to us, so we can’t see it!
This is very simplified and doesn’t take into account the expansion of the universe. Expansion makes our “observable” universe much larger. But it should give you an idea of what we mean when we say “observable universe”
This is a really dumb question as I have been able to understand the majority of the responses and I thank you all for dumbing it down far enough for me to do so. I am wondering what “c” stands for or represents as there has been responses with talk of 1c, 2c and 4c?
Thank you
Its the limited distance we can see in the universe due to it expanding.
Imagine you have a space that expands 1 meter per second for every 100 meters (obs made up numbers for easier understanding).
That means that if 2 objects are 100meters apart, space between them will expand so that they are receding from one another at 1meter per second.
If two other objects are 200 meters apart, they will be receding at 2meters per second. In other words the the further apart two things are the more space is expanding between them.
So if the speed of light in this madeup universe was 1 meter per second, we would only be able to see 100 meters in such a universe. Because everything further away than 100meters would be moving away from us due to the expansion than light could move, so light will never ever reach that object.
This is the so called “edge” of the observable universe. Things that are so far out that light it sends wont reach us due to the space between us and it expanding faster than the speed of light.
Now there are more to explain here but this is the most basic explanation. What more can be said is that there are some exceptions of things we can see that are beyond this above mentioned edge. We can see these things only because they sent their light very long ago when they were still within this range, we are seeing the old light they sent just before they went out of range to ever reach us with their light again! 😀
These superdistant faraway galaxys will gradually disappear forever from our skies over time.
Now as for whats beyond the observable universe. We dont know but leading hypothesis is… more stars and galaxies ofc. That the true size of the universe is much larger than the range we can see. Only way we will ever know is if we figure out a way to travel faster than the speed of light.
Bonus speculation: Or if we find something measurable that travels faster than light, etc gravity waves could’ve been a contender for this but it turns out they travel at the same speed as light. which might indicate that everything else also follows this cosmic speed limit.
This also would mean that no matter beyond the observable universe can affect us gravitationally. So that i would assume kinda kills the repeating big crunch hypothesis?
Alright, little buddy!
Imagine you’re inside a giant bubble. Everything you can see inside this bubble is the “observable universe.” It’s the part of space where light has had time to reach us, so we can see it. Outside the bubble, there’s probably more universe, but the light hasn’t reached us yet, so we can’t see it. As time goes on, our bubble gets bigger and we can see more! So, the “observable universe” is just everything we can currently see in space.
Its the furthest distance that light has had time to reach us.
So we might look at a star very faintly whose light started traveling to us back near the start of the universe.
There will be light sources further away, but their light has not reached us yet.
But it will in time.
So the observable universe is getting bigger at the speed of light.
Note: For two separate things to **cause** an effect on each other, something must travel in between. And the fastest travel is light. So the speed of causality is light speed.
Over great enough distances, space is expanding faster than the speed of light. This means that beyond a certain distance light will *never* reach Earth. Therefore there is a limit to how much of the universe we will ever be able to observe.
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