re: Relax - Milky Way Collision with Andromeda Further in Future than Earlier Predicted

How do they even know how many grains of sand there are? Seems like a wild guess.

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I’m calling bullshite on this. We have thousands of collisions every year in our solar system. You can’t say there won’t be collisions when you have two systems each containing thousands of trillions of objects running into each other

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Stars that are neighbors in a galaxy have had a very long time under the influence of each other's gravity to move closer and closer together, and eventually collide.


Let's try to figure the odds of two stars colliding in a galactic "collision":

Let's go with a slightly above average sized star and say the diameter is 2 million km on average. And let's go with 1 trillion stars in andromeda, and 500 billion in the milky way. And we'll go with 100k ly diameter for the milky way, and 200k ly for andromeda.

I'll do it by figuring the total surface area of andromeda and the total surface area of its stars, then throw the milky way's 500 billion stars into it one at a time and figure the odds of getting at least one hit.

And since we are throwing stars at stars, and glancing blows count, I'll double the diameter of the average star to calculate the surface area.

Total star surface area: pi*(2million)^2 * 1 trillion = 1.25x10^25 sqkm

Total galactic surface area: pi*(100,000ly)^2 = 2.5x10^36 sqkm

So the odds of a single star from the milky way colliding with a star in andromeda as they fly through each other are roughly 0.000000000005 to 1, or 0.0000000005%. That means the chance of a single star NOT hitting another star is about 99.9999999995%.

Now, we try that 500 billion times, 0.999999999995^500 billion = about a 92.8% chance of at least one hit.


I have completely forgotten (if I ever really knew) how to figure the odds of more than one occurrence, or the most likely number of occurrences, but it's only a handful at most.



Of course this is just a back of the napkin calculation that assumes a uniform distribution of stars, and doesn't account for the pull of gravity between stars. But considering the speed at which the galaxies will collide and the generally huge distances between stars, I think the effect of gravity would be pretty much negligible as far as causing more collisions.

If everything is expanding out due to the Big Bang then why would galaxies ever collide? Shouldn’t everything be getting further apart?

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Hopefully someday we will figure out space travel.

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I think we have.

Does anyone really think that the human race is going to survive the next 4 billion years anyway?

We gonna be gone long before this celestial event occurs

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And rather than taking place in about 3.75 billion years, it’ll be in about 4.5 billion years.

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Will this mess up my trip to Punta Cana?

TIA

We will kill ourselves way before that.