<p>How can black holes spin if the event horizon isn't a surface but just the border between where light can escape and where it can't? A black hole is assumed to be a singularity or the &quot;entrance&quot; of an Einstein Rosen Bridge (while white holes are the &quot;exit&quot; of one) so how can it spin and how can you tell how fast it spins (on its event horizon or whatever)? Isn't it rather the accreted material that is spinning around the black hole?</p>

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2020-07-14T11:07:42.563Z
Related: https://en.wikipedia.org/wiki/Frame-dragging
PM 2Ring
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2020-07-14T14:14:02.857Z
See also https://astronomy.stackexchange.com/questions/18314/how-does-a-black-hole-spin and https://astronomy.stackexchange.com/questions/33359/how-do-we-know-that-black-holes-are-spinning
ProfRob
<black-hole><rotation>
How can black holes spin if they're singularities?
Ioannes
# How can black holes spin if they're singularities?

(Asked by: username_0 on 2020-07-14)

How can black holes spin if the event horizon isn't a surface but just the border between where light can escape and where it can't? A black hole is assumed to be a singularity or the "entrance" of an Einstein Rosen Bridge (while white holes are the "exit" of one) so how can it spin and how can you tell how fast it spins (on its event horizon or whatever)? Isn't it rather the accreted material that is spinning around the black hole?

**Tags:** black-hole, rotation

> **Comments:**
> **username_1**: Related: https://en.wikipedia.org/wiki/Frame-dragging  
> **username_2**: See also https://astronomy.stackexchange.com/questions/18314/how-does-a-black-hole-spin and https://astronomy.stackexchange.com/questions/33359/how-do-we-know-that-black-holes-are-spinning  

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