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/sci/ - Science & Math

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10485053 No.10485053 [Reply] [Original]

Assuming the entire cosmos was empty, how long would it take two golf balls placed at the opposite ends of the observable universe to gravitate towards each other and eventually join?

>> No.10485069

>>10485053
They would never meet. If they're the same size, they might not orbit one another.
The result might be that they would drift away in the cosmos, lost in eternity.
Now, if one golf ball was bigger than the other, there situation might be different.

>> No.10485081

>>10485069
>retard

>> No.10485094

>>10485053
Gravity is not all that well understood so it's not possible to say

>> No.10485103

I think you can just use keplers laws to figure this out. Too lazy to do it right now.

>> No.10485114
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10485114

>>10485069

>> No.10485117

>>10485094
>Gravity is not all that well understood
except it is

>> No.10485120

Assuming newtonian gravity, t = π/(16√GM)⋅x^(3/2)
borrowing from https://www.physicsforums.com/threads/time-for-two-bodies-to-collide-under-gravity.246833/

So t = 2.9 *10^40 s, or 6.7*10^22 times the current age of the universe

>> No.10485123

youre retarded. they wouldnt meet because the universe is expanding.

>> No.10485124

>>10485123
>Assuming the cosmos is empty
I take that to mean no other matter, and no dark energy. Hence, no expansion.

>> No.10485126

>>10485081
>>10485114
The gold balls would become orphan balls which would be affected by a lagrangian point, from which there is no gravity.
The two objects wouldn't meet.
I stand by my point, cosmos empty, no attraction.

>> No.10485131

>>10485120
Actually I think I fucked up the exponent, should be 2.9*10^45 s

>> No.10485136

>>10485126
>orphan balls
There's not enough space welfare for the two golf balls to meet.

>> No.10485139

>>10485053
That depends, is it made up dark matter?

>> No.10485213

>>10485124
Those aren't the cause of the expansion.

Also, how large do you assume the universe to be?

>> No.10485284

>>10485213
diameter 93 bn ly

>> No.10485297

>>10485053
Cosmic inflation would separate them into different observable universes relatively quickly, but if cosmic inflation is deleted magically, they’d approach on the scale of trillions of years.

>> No.10485869

>>10485284
Observable universe
>>10485213
The actual universe could be infinite, impossible to determine with light traveling at a finite speed

>> No.10485876

>>10485297
They wouldn't even recognize each others existence for however far they were apart in light years, and only then would they interact with each other

>> No.10485956

>>10485126
>cosmos empty, no attraction.
'
It is not empty, there are two golf balls in it.

>> No.10485963

>>10485876
>They wouldn't even recognize each others existence for however far they were apart in light years, and only then would they interact with each other

HOLY FUCK, IS THAT ANOTHER GOLF BALL!!!!!??????????