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HNQ
3:09 AM
3
Q: Why does rhenium get a pass on being radioactive?

Paul YoungThorium is thought of as radioactive and "dangerous" because its half life is 10 billion years. However, most rhenium is radioactive with a half life of 40 billion years even though rhenium does have a stable isotope which comprises a minority of natural rhenium atoms. Why don't we hear more ab...

 
 
19 hours later…
HNQ
10:36 PM
2
Q: Are black holes bound to merge once their event horizons touch?

Krzysiek KarbowiakEven if they move toward each other at relativistic velocities and not head-on? I looked at questions Black hole collision and the event horizon and Dynamics of Event Horizons between head-on colliding non-rotating black holes, but did not find the answer.

 

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