Season's Greetings

Mike0001

Well-Known Member
Merry Christmas, one and all.


Did you know that from the outside, you can never observe a star become a black hole? That all you see is it slowly collapsing in towards its event horizon and becoming dimmer and more and more red-shifted? (Not that red-shifted is a good term, as red will eventually be too high a frequency.) The bits outside the event horizon will never be observed passing through it.

Merry Xmas, anyway! :D
 

gomezz

Well-Known Member
Red-shifted is a very good term as it casts the phenomenon in a way which is understandable by our senses and which our brain can extend to meaning beyond that.
 
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Black Hole

Black Hole

May contain traces of nut
I forget what it was but there was something on telly recently - probably Brian Cox wittering on. He failed to point out that when an object crosses the event horizon and appears to become frozen in time, the mechanisms that emit radiation will also be frozen in time and therefore emit zero frequency (infinite wavelength).

Incidentally, it drives me mad when Marcus du Sautoy pontificates on physics - as he did when my question was used on The Material World asking how snowflakes achieve symmetrical growth over many billions of water molecules separation. I wanted to hear an answer from a solid-state physicist, not a bloody mathematician!
 

Mike0001

Well-Known Member
I forget what it was but there was something on telly recently - probably Brian Cox wittering on. He failed to point out that when an object crosses the event horizon and appears to become frozen in time, the mechanisms that emit radiation will also be frozen in time and therefore emit zero frequency (infinite wavelength).
Was that the Dr Who lecture? Actually, he did mention that. I only saw the end of the lecture, but he did mention it. What he may not have mentioned was that anything that crosses the event horizon does so at the speed of light.

Incidentally, it drives me mad when Marcus du Sautoy pontificates on physics - as he did when my question was used on The Material World asking how snowflakes achieve symmetrical growth over many billions of water molecules separation. I wanted to hear an answer from a solid-state physicist, not a bloody mathematician!

You will just love this, then:

http://arxiv.org/pdf/1202.1272v1.pdf

The maths may be too hard for a solid-state physicist!

But conventional symmetrical snowflakes are not the norm, are they? Don't they only form when ambient conditions are uniform over the size of a snowflake? (And some other conditions.)
 
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