How do we know that the universe still exists and has not been swallowed up by some gigantic black hole?

Question

I'm not a scientist, but very fascinated to see your answers.
If we look out into space, we're looking at the past as it takes so many light years for the light from stars to reach us. So if a star "dies" do we know of this light years later?

Answer 1

First of all, a light year is a measure of distance, not time. And yes, when stars die we do not know it until the light from that star no longer reaches the Earth or our telescopes. For example the light from the sun takes about 8 minutes to reach us, so if the sun died out, we wouldn't know it until 8 minutes after it happened. The reason we know that we have not been swallowed up by a black hole is basically because we still have light and haven't been stretched into spaghetti, which is basically what happens when something gets eaten by a black hole.

Answer 2

Yes, we would know that the star died only after the light it emitted stopped reaching us. Depending on how far away the star is, that might be many light years later.

For example, our Sun is eight light minutes away. In other words, it takes light from the Sun eight minutes to travel the 93 million miles between the Sun and Earth and to reach us. If the Sun were to suddenly "go out" tomorrow at precisely 12 noon, we would not know it for another 8 minutes.

Same thing for a star that was farther away.

Interesting question about the Universe being swallowed up by a black hole. Some people think the Universe IS a black hole.

Answer 3

The basic answer is: because we're still here. We get our information from light, or radio waves, x-rays, ifrared--they're all electromagnetic waves, pick your poison. Light travels at a certain speed. 300,000kms. It's pretty fast but not instantaneous. Light from the most distant objects takes billions of years to get here so we don't get the news for billions of years. That's not to say that we can't get the news about very near obejcts like the other planets in our solar system.
The complex answer is: We might just be inside a black hole right now and not care because it doesn't make a difference. Some theorists think that the larger the black hole, that is, the more mass that it has, the less dense it needs to be to continue being a black hole. This is still up for debate. But it is interesting to think that someone outside of our universe might just see a black hole where the days of our lives play out.

There's a few other theories listed here:
http://abstractdimension.com/index.php/2006/06/is-the-universe-a-black-hole/

Answer 4

A black hole has, at its heart, a singularity where all the laws of physics breakdown. The gravitational pull is so enormous that not even light can escape.

Anything entering a black hole becomes infinitely heavy. We just couldn't survive under those conditions.

Regarding the stars, yes, a lot of the stars you see at night no longer exist - but there's no way for us to know which ones. Everytime you look at the night sky you are looking into the past. In actual fact, anytime you look at ANYTHING you are looking into the past.

If you look at yourself in the mirror it will take a fraction of a fraction of a fraction of a second for the light of the reflection to reach your eyes - so you are, in reality, looking at yourself as you were in the past. But obviously it's too fast a process for our brains to compute.

Answer 5

RE the "Black Hole" portion of your question:

Technically, the universe IS a black hole. It has an "event horizon" just like a black hole, where the escape velocity is that of light.

In the case of the universe, that "event horizon" is located just beyond the furthest galaxies we can see. As the universe expands, other galaxies appear to be moving away from our own galaxy. The further out you look, the faster the other galaxies are receding. As far as we can look, the velocities of those galaxies are about 90% the speed of light; thus the "event horizon" beyond which we can see nothing, is past them.

Also, it turns out that the larger a black hole is, the less "dense" it has to be in order to have an event horizon. A black hole the size of the universe would require a density just about the same as that which we observe in the universe.

So, by those definitions at least, the Universe itself is a black hole.

Answer 6

Well we see the universe as composed of 4% Atoms, 23% Cold Dark Matter, 73% Dark Energy. This is the definition of universe. To say that the universe does not exist would go against scientific evidence. Unless you're asking this in a philosophical sense. In fact, I don't really understand your question.

Answer 7

Inside a black hole, the escape velocity exceeds the speed of light. If the universe were inside a black hole, we wouldn't be able to see diddly squat since all the light given off would be sucked towards the singularity and redshifted beyond our ability to detect it.

Answer 8

If we had been swallowed by a black hole, time as we know it would have be stretched to the point where it appears to stop as we reach the event horizon. We'd be frozen in one time forever. But we are constantly observing time's progress, so we cannot have entered a black hole.

Answer 9

We don't. Looking at stars is looking into the past, we have no way of knowing what is happening at this instant accross the galaxy. We can see when a star dies (detecting x & gamma rays, and microwaves), but only after it has actually happened.

Answer 10

You are right, I think, I think thats what has happened during these years. Or it could just be the back hole of newspapers stories and orther horrors that makes me think that way.
Hope to see you in the black hole.

merry Christmas