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Ravi Mandavi
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Since at event horizon, the escape velocity of black hole must be greater than speed of light but even light can't escape from black hole so is it possible that speed of gravitational wave > c?
Ravi Mandavi said:Since at event horizon, the escape velocity of black hole must be greater than speed of light but even light can't escape from black hole so is it possible that speed of gravitational wave > c?
Good, you answered you own question.skeptic2 said:On the other hand, there is an explanation that as matter falls through the EH, it leaves its gravitational field frozen at the horizon.
Orion1 said:
Power radiated by orbiting bodies:
[tex]P = \frac{dE}{dt} = - \frac{32}{5}\, \frac{G^4}{c^5}\, \frac{(m_1m_2)^2 (m_1+m_2)}{r^5}[/tex]
Orbital decay from gravitational radiation:
[tex]\frac{dr}{dt} = - \frac{64}{5}\, \frac{G^3}{c^5}\, \frac{(m_1m_2)(m_1+m_2)}{r^3}[/tex]
If gravitational wave velocity was greater than luminous velocity, then the amount of power radiated and the orbital decay of binary pulsars would be much less.
If gravitational wave velocity was less than luminous velocity, then the amount of power radiated and the orbital decay of binary pulsars would be much more.
However, the measurements of these functions in nature indicate agreement with these equations in which the intrinsic velocity of gravitational waves is exactly equal to luminous velocity.
Could the gravitational wave velocity be measured directly from nature with is equation?
Gravitational wave velocity:
[tex]c = \left[ \left( \frac{64 G^3}{5} \, \frac{(m_1m_2)(m_1+m_2)}{r^3} \right) \left( - \frac{dr}{dt} \right)^{-1} \right]^{\frac{1}{5}}[/tex]
Reference:
Gravitational wave - Wikipedia
Chronos said:Jimbaugh, do you think Hulse was not compelling evidence of gravitational waves and their Lorentz invariance?
Orion1 said:
What is the gravitational wave frequency equation for the Hulse–Taylor binary pulsar system?
Reference:
Gravitational wave - Wikipedia
PSR B1913+16 - Wikipedia
http://www.nobelprize.org/nobel_prizes/physics/laureates/1993/hulse-lecture.pdf
http://www.nobelprize.org/nobel_prizes/physics/laureates/1993/taylor-lecture.pdf
General relativistic model for experimental measurement of the speed of propagation of gravity by VLBI - University of Missouri - Kopeikin and Fomalont
strat1227 said:So if that's the case (if it's not then please just correct my misunderstanding and ignore this question), why does it take any time at all for gravity to permeate? If you drop a billiard ball onto a outstretched blanket, all points of the blanket are affected at the same time. Similarly, if you just spontaneously created a large amount of mass in the middle of empty space, would not the space-time field be instantly altered?
Nabeshin said:The disturbance propagates at something like the sound speed of the material (I have no idea what this is for a taut sheet, but certainly finite!).
Only when I change the situation (remove some mass somehow, or something like that), does the geometry need to respond, and these ripples travel outwards like waves on a pond at precisely the speed of light.
Why would this be so? Why does 'mathematically' mean you'd ignore propagation velocity?strat1227 said:Mathematically speaking, all points would feel it at the same time
DaveC426913 said:Why would this be so? Why does 'mathematically' mean you'd ignore propagation velocity?
Yeah but the movement must still propagate.strat1227 said:All the points are connected, so if you pull down on any of them they all move ...
DaveC426913 said:Yeah but the movement must still propagate.
A line segment doesn't move. You could measure the distance from your hand to your target as being one light year, then move your hand and measure again. But it's not the same line segment (since it's just a measurement), and it took a finite time between measurements.strat1227 said:Haha not to be off topic, but why? It doesn't in the line segment example ...
The model you used was a billiard ball on a blanket. You can ignore the physical traits of the system and only examine it mathematically, but it is a central cause and a radiating sequence of effects. In a cause/effect system the effect must propagate from the central cause at a finite speed.strat1227 said:The stretching of the plane could just as easily be simultaneous across the whole plane, the only limiting reason it wouldn't be are physical limitations
DaveC426913 said:A line segment doesn't move. You could measure the distance from your hand to your target as being one light year, then move your hand and measure again. But it's not the same line segment (since it's just a measurement), and it took a finite time between measurements.
The model you used was a billiard ball on a blanket. You can ignore the physical traits of the system and only examine it mathematically, but it is a central cause and a radiating sequence of effects. In a cause/effect system the effect must propagate from the central cause at a finite speed.
It's cool. I like discussing.strat1227 said:Haha ok, we're just kinda talking past each other at this point, and since it's not really relevant to the topic in any real way anymore I'll just say that I understand my mistake from earlier and thanks for helping me :)
DaveC426913 said:It's cool. I like discussing.
strat1227 said:Haha ok, cool :)
Basically what I was thinking is that the reason motion propagates is on the molecular level. If you push one atom it moves and then pushes the next one, and so on. Similar to how when a light turns green, the first car starts moving THEN the next car starts moving, etc, instead of all of them moving as soon as it turns green.
However, (presumably), the fabric of space-time isn't molecular. I'm not particularly knowledgeable about the subject, but I would assume that space-time is continuous, not discrete. So if I tug on a string of space-time, it's not individual atoms moving, it's a continuous string so as I pull on my end, the other end moves simultaneously.
Ravi Mandavi said:Since at event horizon, the escape velocity of black hole must be greater than speed of light but even light can't escape from black hole so is it possible that speed of gravitational wave > c?
Ravi Mandavi said:what i got is this- http://metaresearch.org/cosmology/speed_of_gravity.asp
According to it gravitational wave's speed faster than light, though i don't think so and feel its rubbish.
GTOM said:If gravity is the thing that defines spacetime, why is it necessary bounded by a speed, that is only meaningful, when we know exact parameters of spacetime, what is exactly one meter and one sec?
One sec in strong gravity and week gravity isn't exactly the same.
GTOM said:If gravity is the thing that defines spacetime, why is it necessary bounded by a speed, that is only meaningful, when we know exact parameters of spacetime, what is exactly one meter and one sec?
One sec in strong gravity and week gravity isn't exactly the same.