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Warp wrote:
> Darren New <dne### [at] san rrcom> wrote:
>>> Not stopped. Asymptotically slowing down.
>
>> So, the steeper the gravity gradient, the slower he falls? That doesn't make
>> sense? He actually *slows down* as he falls? Nothing ever goes thru the
>> event horizon?
>
> No, it looks *from the outside*, from the point of view of an external
> observer, like his time is slowing down.
Right. Understand that my confusion is between these two sentences:
"He is slowing down."
"His time is slowing down."
> Remember that speed and time is always relative to who is observing.
I would think that from the outside observer, his time is slowing down even
while his velocity is increasing.
I find it hard to believe that in falling into a black hole, your velocity
decreases.
> Actually there are a few things which can be said of gravitons. In other
> words, "if gravitons existed, they must have these properties". For example,
> they would have spin 2.
Yep. Stuff like that. But I think that's because of where it would fall in
the tables.
> (And no, I haven't the faintest idea what "spin" means. I just read
> wikipedia. :P )
"Spin" is a fascinating concept related to symmetry. A "spin 1/2" particle
means if you turn it 180 degrees, it looks the same. So a "two of diamonds"
playing card would be "spin 1/2" - it looks the same right side up as upside
down. (Discounting, of course, that it's 3D, so has a back that's different
from the front.)
An "ace of spades" has "spin 1" - if you turn it 180 degrees, the spade in
the middle will be pointing down instead of up, so you have to turn it 360
degrees.
And yes, a "spin 2" particle really is as strange as it sounds. You have to
turn it around 720 degrees before it's symmetric again. Don't ask me how
that works out.
That's about all I know about spin, tho, so ...
>> If hawking radiation doesn't exist, then you have no way of seeing what's
>> inside the event horizon, and hence the information on the spin of the
>> particles in there is lost?
>
> Why is it lost? Just because you can't see it doesn't mean it doesn't
> exist.
It's lost because it cannot influence other particles in the local area. Of
course, that's because the particles outside the horizon are a spacelike
distance from the particles inside the horizon, so maybe you're right. Maybe
it's the equivalent of being outside the cosmological horizon.
> If something moves to the other side of the cosmological horizon (from
> our perspective), is the information "lost"?
Maybe. I don't know. It can't affect us, but it can affect other things in
the local area. Technically, the particles *could* affect things a spacelike
distance away, which is what all the yadda about "quantum teleportation" is
about.
>> I think that's what I was trying to express. With a sufficiently large black
>> hole, you might not know you crossed the event horizon because the rate of
>> change of curvature is so slow. Of course you know you're in trouble.
>> There's just no "bump" as you cross over. And if you're in free-fall
>> anyway, what might you notice?
>
> I think that you would notice everything being warped.
Sure. But would you notice it significantly more one inch inside a
galaxy-size event horizon more than you'd notice it one inch outside a
galaxy-size event horizon? I don't know, but I don't think that's how it
works - the event horizon, as I understand it, isn't a discontinuity.
--
Darren New, San Diego CA, USA (PST)
"Ouch ouch ouch!"
"What's wrong? Noodles too hot?"
"No, I have Chopstick Tunnel Syndrome."
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Darren New <dne### [at] sanrrcom> wrote:
> I would think that from the outside observer, his time is slowing down even
> while his velocity is increasing.
>
> I find it hard to believe that in falling into a black hole, your velocity
> decreases.
Cheating a little and looking ahead in my textbook, I find the following
sentence regarding the path of a particle falling radially into a black hole:
2/(3*sqrt(2m)) * ( (r_0)^(2/3) - r^(2/3) ) = tau-tau_0
"Looking at this equation, the mysterious surface r=2m makes no appearance. The
body falls continuously to r=0 in finite proper (inertial) time, in contrast to
the result seen by an outside observer. In fact, one can say that the entire
evolution of the physical universe has occurred by the time the body passes the
surface r=2m."
In other words, as seen by an outside observer, you reach the event horizon and
sit. Forever. As seen by you, on the other hand, you go speeding right on
through like it's not even there. The surface only has significance for an
observer far away.
- Ricky
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Darren New escreveu:
> Warp wrote:
>> (And no, I haven't the faintest idea what "spin" means. I just read
>> wikipedia. :P )
>
> "Spin" is a fascinating concept related to symmetry. A "spin 1/2"
> particle means if you turn it 180 degrees, it looks the same. So a "two
> of diamonds" playing card would be "spin 1/2" - it looks the same right
> side up as upside down. (Discounting, of course, that it's 3D, so has a
> back that's different from the front.)
>
> An "ace of spades" has "spin 1" - if you turn it 180 degrees, the spade
> in the middle will be pointing down instead of up, so you have to turn
> it 360 degrees.
>
> And yes, a "spin 2" particle really is as strange as it sounds. You have
> to turn it around 720 degrees before it's symmetric again. Don't ask me
> how that works out.
Wonderful explanation. So far, from my days of chemestry in college,
all I (thought I) knew was that spin 1 was an electron spinning in one
direction and spin -1 in the other direction, whatever it be. :P
>> If something moves to the other side of the cosmological horizon (from
>> our perspective), is the information "lost"?
>
> Maybe. I don't know. It can't affect us, but it can affect other things
> in the local area. Technically, the particles *could* affect things a
> spacelike distance away, which is what all the yadda about "quantum
> teleportation" is about.
quantum entanglement! Beam me into a blackhole! :D
>> I think that you would notice everything being warped.
Including your body! :P
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triple_r wrote:
> In other words, as seen by an outside observer, you reach the event horizon and
> sit. Forever.
So at what point does the black hole increase in mass? Why would a black
hole ever grow if nothing falls thru the event horizon?
And at what distance do you start slowing down?
If you take the Earth and condense it down to a black hole, then stop a
particle in orbit 100 miles above where the surface used to be, the particle
will accelerate towards the black hole, right? But to avoid crossing the
event horizon, it must logically decelerate, as seen from the POV of someone
in orbit (say). You wouldn't stop at the original altitude of the surface,
but you would stop before you get to the event horizon, so in this case,
gravity must be causing you to decelerate. Yes?
--
Darren New, San Diego CA, USA (PST)
"Ouch ouch ouch!"
"What's wrong? Noodles too hot?"
"No, I have Chopstick Tunnel Syndrome."
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Darren New escreveu:
> triple_r wrote:
>> In other words, as seen by an outside observer, you reach the event
>> horizon and
>> sit. Forever.
>
> So at what point does the black hole increase in mass? Why would a black
> hole ever grow if nothing falls thru the event horizon?
He's talking about what is seen from an external observer, which is the
same explanation Hawking gave in one of his books. The observer sees a
kind of after image that seems to ever approach the event horizon
without ever touching it, but in reality the crossing of the EH already
took place and nothing of what happens in the inside is seen...
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nemesis <nam### [at] gmailcom> wrote:
> Darren New escreveu:
> > triple_r wrote:
> >> In other words, as seen by an outside observer, you reach the event
> >> horizon and
> >> sit. Forever.
> >
> > So at what point does the black hole increase in mass? Why would a black
> > hole ever grow if nothing falls thru the event horizon?
> He's talking about what is seen from an external observer, which is the
> same explanation Hawking gave in one of his books. The observer sees a
> kind of after image that seems to ever approach the event horizon
> without ever touching it, but in reality the crossing of the EH already
> took place and nothing of what happens in the inside is seen...
Besides, the mass of a spherical object, as measured from outside the
sphere, is independent of how the mass is distributed. It could be all
in the center or it could be all evenly distributed. From the outside
it would measure the same.
That's the reason why you can eg. calculate orbits assuming the Earth
is a point, rather than a sphere. (Well, as long as the orbit doesn't
collide with the surface of the Earth, of course.)
--
- Warp
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nemesis <nam### [at] gmailcom> wrote:
> > Maybe. I don't know. It can't affect us, but it can affect other things
> > in the local area. Technically, the particles *could* affect things a
> > spacelike distance away, which is what all the yadda about "quantum
> > teleportation" is about.
> quantum entanglement! Beam me into a blackhole! :D
If quantum teleportation exists, I wonder if it would be theoretically
possible to teleport a particle out of a black hole.
--
- Warp
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nemesis wrote:
> kind of after image that seems to ever approach the event horizon
> without ever touching it, but in reality the crossing of the EH already
> took place and nothing of what happens in the inside is seen...
Hmmmm.... I'll have to think on it.
--
Darren New, San Diego CA, USA (PST)
"Ouch ouch ouch!"
"What's wrong? Noodles too hot?"
"No, I have Chopstick Tunnel Syndrome."
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Warp wrote:
> If quantum teleportation exists, I wonder if it would be theoretically
> possible to teleport a particle out of a black hole.
And therein lies the clash of QED and GR. :-)
--
Darren New, San Diego CA, USA (PST)
"Ouch ouch ouch!"
"What's wrong? Noodles too hot?"
"No, I have Chopstick Tunnel Syndrome."
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Darren New escreveu:
> nemesis wrote:
>> kind of after image that seems to ever approach the event horizon
>> without ever touching it, but in reality the crossing of the EH
>> already took place and nothing of what happens in the inside is seen...
>
> Hmmmm.... I'll have to think on it.
I think it has something to do with the last photons coming out of the
object entering the EH are severely slowed down by the massive gravity
and only reach you after much more time than normal has passed.
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