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event horizon

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Marcus Henri Staffhorst

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Feb 2, 2009, 10:47:35 AM2/2/09
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Is there anyone who can tell me, in very simple English, what "event
horizon" means???

Thank you in advance

Marcus Staffhorst


mike

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Feb 2, 2009, 3:11:16 PM2/2/09
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>Is there anyone who can tell me, in very simple English, what "event
>horizon" means???

I'll give it a try for you Marcus. :-)

It’s to do with the force of gravity and the behaviour of
light.
When something is heavy it 'bends' space, get big & heavy
enough and space gets so distorted that it can form an
‘event horizon’, a part of space that light cannot escape.
(This is not a physical thing but a calculated distance from
the centre of gravity, usually (but not always,) within the
item.)
Most large planets have an event horizon (EH), and the Earth
has one, as does the sun. The Earth EH is about 1cm, and the
sun EH is 2km, so they are tucked well out of our way. :-)
If the sun was magicaly shrunk (squeezed) so its mass stays
the same and it is smaller than the EH, it would be unable
to shine and the weight would collapse to a point (called a
singularity). The EH would remain the 2km though and the
planets still orbit since the gravity wouldn’t have changed.
It would then be a ‘black hole’ (though Steven Hawking has
shown they ‘ant black).

So, any good for you?
Mik :-)

GeekBoy

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Feb 15, 2009, 7:32:04 PM2/15/09
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The distance from the center of a black hole where the escape velocity is
equal to the speed of light

"mike" <mike...@invariant.freeserve.co.uk> wrote in message
news:psjeo4pq5dniht0kq...@4ax.com...

Stephen Morais

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Mar 14, 2009, 7:38:00 PM3/14/09
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It is the point where the escape velocity is greater than or equal to
the speed of light.

Uncle Clover

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Mar 15, 2009, 4:09:52 AM3/15/09
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Or in other language, it's the point at which the only way to back away in
space is to also back away in time. You have to travel backwards through
time via the same route you got into the mess to begin with. I.e.,
literally "rewinding" yourself and the space around you.

The concept of "event horizon", when you wish to let yourself play with it
a little in a philosophical manner, can be quite illuminating. ;-)

Barry OGrady

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Jul 21, 2009, 6:18:38 PM7/21/09
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On Sat, 14 Mar 2009 18:38:00 -0500, Stephen Morais
<qm2...@sbcglobal.net> wrote:

Its a fictional thing.

Barry OGrady

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Jul 21, 2009, 6:19:19 PM7/21/09
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As long as you are aware its fiction.

Uncle Clover

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Jul 22, 2009, 1:11:16 AM7/22/09
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I am aware that it's an abstract description, like the bull in the china
shop and how that no scientifically observable reason exists as to why the
bull can't be run forward or backward in time, all perfectly acceptable to
the rules of physics. The fiction, to me, seems more to be the arrow of
time, not either direction of travel.

Still, I know what you're saying and yes, I am aware of it. :-)

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