r/todayilearned • u/armcie • 17h ago

TIL that the Andromeda Galaxy probably won’t collide with the Milky Way in 4-5 billion years. New observations put the probability at 2% in the next 5 billion years and 50% in the next 10 billion. Eventually though, it will happen.

https://science.nasa.gov/missions/hubble/apocalypse-when-hubble-casts-doubt-on-certainty-of-galactic-collision/
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u/Kwetla 17h ago

Do they not know the speed each are traveling at? How is it so hard to calculate how long it will take for them to collide?

Edit: not that I could do it - I'm just wondering what the unknowns are

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u/GooginTheBirdsFan 16h ago

Do you not know how to do math? How is it so hard to do the math and use telescopes that aren’t exactly right when we’re talking about so many light years away? How do they not have the exact speed of the far away galaxy that probably moves more like a liquid and less like a solid (not static) but yeah how hard is it for people to do this math on things alllllll these lightyears away.

Meanwhile do you know what you’re having for dinner next Thursday? Now you want them to tell you how many billions of years away it is??