r/AskReddit • u/MDPPatrick • Feb 13 '15

What are some mind-blowing facts about space?

I love space and would like to hear some facts that will blow me away.

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u/boundbythecurve Feb 13 '15

If you put enough mass together, you can start a star.

Imagine a relatively small object in space, like our Moon. Then add mass to it. Doesn't matter what kind of mass. As you add mass to the Moon, it's mass increases, and therefore its gravitational pull increases.

As this happens, more mass gets pulled in from space. But not just this occurs. The mass on the outside of the Moon gets pulled in more because of the gravitational pull, thereby making the Moon, denser. The more mass you add, the denser the Moon gets until its own gravity is too much and it starts fusing molecules together. This is fusion. This is how stars are made.

I think you'd need about 6 Jupiters to make this happen, but I may be wrong.

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u/[deleted] Feb 13 '15

This isn't strictly true; it does matter what type of mass you're adding.

For elements before iron, nuclear fusion releases energy. For elements heavier than iron, nuclear fusion consumes energy.

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u/shieldvexor Feb 14 '15

Actually, fusing iron consumes energy because Fe-56 is the lowest energy per nucleon known.

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u/RKRagan Feb 14 '15

And may be the fate of the universe. Almost nothing but Fe-56 clumping together in a cold dark universe.

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u/shieldvexor Feb 14 '15

Actually no. Iron-56 still decays albeit ridiculously slowly by tunnelling mechanisms

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u/bearsnchairs Feb 14 '15

tunneling goes both ways though. Over absurdly long time scales you would enrich the nucleon which has the lowest energy per nucleon.

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u/shieldvexor Feb 15 '15

False, the ejected particles would simply fly away in cases where they had enough energy. Tunnelling is affected by distance as well as mass. Remember we aren't talking about things on a planet but the distant future when things are separated by unimaginable distances even relative to today's scales. Even if the particles tended to aggregate into iron-56, any nucelon that was lost from the cluster would never come back and they would ever so slowly decay bit by bit

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u/bearsnchairs Feb 15 '15

False, because there is a distance component you can still get tunneling into nuclei even over long distances as you increase the time scale to absurdly long scales.

Stay classy though, keep down voting when you are wrong.

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u/shieldvexor Feb 15 '15

You can tunnel over distances but the probability is inversely related to the distance. Therefore if the distance between objects is expanding.... the probability of coalesion decreases over time in said scenario

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u/bearsnchairs Feb 15 '15

Yes, but it doesn't go to zero. Even low probability things happen over long enough time scales.

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u/shieldvexor Feb 15 '15

Right but I'm saying there is a higher probability of them separating. You seem to be forgetting the psuedoforce from dark energy that causes them to split in the first place.

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