Awesome Astronomy

General Relativity

General Relativity is… well, awesome. The number one reason is because after you really understand General Relativity you’re like, no way is that real, that’s something they just took out of a science fiction movie! But it’s not. It is real science.

I’m not going to attempt to give you an explanation of General Relativity because I’ll just confuse you, but I’d recommend taking a minute and watching this clip from Elegant Universe, it’s a little cheesy, but a really clear explanation with good computer modeling. Fast forward to about minute 3 and a half if you want to skip the Newtonian part, it’s interesting but not neccessary:

So, what sort of implications for awesomeness does General Relativity present us out there in the Universe?

Lets begin with my favorite, black holes.

You see General Relativity basically explains why black holes exist. If ordinary matter can never travel as fast as light, and if not even light can escape from a collapsing star, nothing else can either.

Black holes create a warp in spacetime, this leads to lots of interesting different effects the closer you get to one.

If you were on a spaceship watching another spaceship fall into a black hole as the ship approached the black hole you’d begin to see it slow down. It would take the ship an infinite amount of time to reach the black hole because it is so dense (and because time slows the closer you get to a dense mass). This means even as the ship is being ripped into bits you would see it hang there forever (although you’d need infrared goggles to see the redshift.) Time would essentially become an asymptotic function, if you’re calculus-ly inclined.

Black holes are so incredibly strong that they would rip the ship into atoms and then possibly even rip those atoms apart. If someone was on the ship falling into the black hole they would not see a slowing of time, and of course they’d be quickly disintegrated.

Here’s a video model of what it might look like to fall into a black hole:

This video shows what it would look like to see something fall into a black hole:

So what’s on the other side of a black hole?

That’s an excellent question. No one’s one hundred percent sure, but some astrophysicists think that rotating black holes could lead to wormholes.

Wormholes, as Einstein and Rosen described them, would happen almost instantaneously and then collapse, making them almost impossible to travel through. The wormhole modeled in this video is called an Einstein-Rosen bridge, which would theoretically form a bridge between two points in our universe. Not all of the narration in this video is accurate but the model’s good:

It’s also thought that wormholes could possibly form links between our universe and other parallel universes. This video’s longer but it’s interesting if you’ve got the time. They talk about theories for how you’d keep the wormholes open:

What other phenomena occur out there in space as a result of General Relativity? Well, one aspect of the nature of light that many people aren’t aware of is how long it takes light from other stars and galaxies to reach us and how this affects the way we see the Universe. For instance light from the Andromeda Galaxy, the closest galaxy to us, has to travel 6 million light years to reach us! That means that we’re seeing that galaxy right now as it existed 6 million years ago! Isn’t that awesome.

The Andromeda Galaxy

The same would be true of a person in Andromeda viewing the Milky Way. Astronomers aren’t even sure exactly what all of the Universe looks like because of this. It’s thought that Quasars are actually visual remnants of forming galaxies that no longer exist as Quasars but which we still see that way because it is taking so long for the light to reach our eyes.


Well, I guess that’s enough about General Relativity for today. But before I go we should talk about what we learned about modeling today. First of all modeling is pretty useful for talking about theoretical concepts like gravity waves and wormholes that you can’t create in a lab to test. It can also come in handy because of the fact that our ability to observe portions of the universe is limited by the time it takes light to reach our eyes. Models can help us to fill in the gaps between what we see and what we hypothesize is happening.

I didn’t talk much about Gravity Waves, but if you’re interested you should check out the LIGO expirement website. It’s very informative and they have some excellent astronomical models.

Next time I’ll be talking about Cosmology!

I’ll leave you with this as an appetizer:


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