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beyubb
2008-Aug-25, 07:14 AM
First ever post! I am glad to have an outlet for the ideas that get kicked off from those Feynman CDs.

Please note I take the elegant buggy and know not Mr. Cal Culus…

Some thoughts and questions I have;

Is the centrifugal force conserved (relative to the increase in gravitation) in a collapsing star? I understand Angular Momentum is conserved in stellar collapse to a neutron star such that due to its smaller diameter, it spins much faster than it had. Would surface particles on the equatorial plain of a rapidly spinning neutron star occupy a drastically different reference frame than those particles that are located in the deep interior of the same star? Drastically different reference frames are actually created upon the event of a star undergoing gravitational collapse. An external observer who witnesses a mass falling into a black hole never sees it pass through the event horizon due to time dilation. Yet the same external observer whom watches mass fall to the same star prior to its collapse sees no such drastic time dilation.

Could time dilation occurring on the interior of a neutron star from one region to another account for any of the internal dynamics of a neutron star? (consider a reference frame in the shape of a ring/doughnut of matter around the neutron star like a belt...)

What about external dynamics (gas/radiation jets from poles)? After all, the surface particles at the poles of a very rapidly spinning neutron star would also be in a different reference frame than surface particles on the equatorial plain in this scenario due only to centrifugal force working against gravitation. Would a neutron star that was spinning slower than the above case have different internal dynamics due to less centrifugal force/dilation?

Taking this to the extreme I would guess that nature may find a mechanism of chance (collision, momentum gained from a companion stars mass feed…) that would indeed take neutron star rotation to some upper limit where by equatorial surface regions come apart or possibly achieve a nominal “earthlike” frame of reference.

Maybe I am in error. Maybe the shape deformations from rapid spin need consideration as well. Or maybe my assumption that centrifugal forces could be enough to lesson the otherwise steep gradient of frames of reference is wrong.

Maybe the more drastic time dilation does not occur until an environ such as a black hole. But hey, can not some of these same questions go on to that type of system as well. If centrifugal force does have influence to the negative of that of the gravitation upon frames of reference, maybe the shape of the event horizon is altered from that of how it would otherwise be considered.

In the end I suspect that time dilation, being so much amplified in the case of an event horizon, may also be somewhat amplified in cases such as a neutron star. Dilation/reference frames in a neutron star could seem to be greatly stratified, even just considering the inverse square and forgetting about my question of centrifugal force. If you could build a room at the center of the earth that could withstand heat and pressure, could you float in gravitational equilibrium? Is this not also an example of a drastically different reference frame? From the point of view of material closer to mid/surface regions, the mass in the center would be so accelerated as to decay faster...

Neverfly
2008-Aug-25, 08:14 AM
I'm sorry, but your post was very hard to follow, because you were answering your own questions as fast as you were answering them, sometimes I could not tell where you were going or what you were asking.. and you were not clear right away what you were talking about. You kind of jumped in halfway talking about Neutron Stars, then black holes...
I'm not trying to be mean.. But it was a pretty tough read there.

Mostly, you seem to be on the right track, albeit jumping to some conclusions, but I don't want to address much without there being more clarity.

If I was in a capsule in orbit around a Neutron star, and you went to the surface, YES, your time would be severally dilated to a much faster rate than mine. You would age much faster. If we set up some Subspace Communication or something, I would appear to be extremely slow, whereas to me, you would be moving and talking at blinding speed, if your movements and words would even be perceptible at all.

Cougar
2008-Aug-25, 07:54 PM
First ever post!
Welcome to the board! The more, the merrier.... generally speaking. :)


Could time dilation occurring on the interior of a neutron star from one region to another account for any of the internal dynamics of a neutron star?
In my unprofessional opinion, no. I tend to think that time dilation involves someone or something in one frame observing electromagnetic signals (light) in another frame. What observations are going on inside a neutron star? Besides, with such extreme density, I am skeptical about how well light propagates anyway. But the main point is, even an observer in a spaceship traveling at .99c relative to earth observes his own clock ticking away quite normally.


What about external dynamics (gas/radiation jets from poles)? After all, the surface particles at the poles of a very rapidly spinning neutron star would also be in a different reference frame than surface particles on the equatorial plain in this scenario due only to centrifugal force working against gravitation. Would a neutron star that was spinning slower than the above case have different internal dynamics due to less centrifugal force/dilation?

I doubt it. I'm not so sure the "internal dynamics" of a neutron star are all that complicated anyway. In a similar situation, Alan Guth said:



If cosmologists are so smart, you might ask, why can't they predict the weather? The answer, I would argue, is not that cosmologists are so smart, but that the early universe is much simpler than the weather!


Taking this to the extreme I would guess that nature may find a mechanism of chance (collision, momentum gained from a companion stars mass feed…) that would indeed take neutron star rotation to some upper limit where by equatorial surface regions come apart or possibly achieve a nominal “earthlike” frame of reference.

I believe neutron stars occupy a fairly small window of stability. If their mass exceeds a certain amount, we have an unstable situation. There are no neutron stars with masses above that amount.


In the end I suspect that time dilation, being so much amplified in the case of an event horizon, may also be somewhat amplified in cases such as a neutron star.

Near the surface, yes, to an outside observer.


Dilation/reference frames in a neutron star could seem to be greatly stratified....

I'm still not sure if this effect comes into play in the situation.


If you could build a room at the center of the earth that could withstand heat and pressure, could you float in gravitational equilibrium?

Yeah, but....


Is this not also an example of a drastically different reference frame?

No, I don't think so. You would float due to a simple Newtonian gravitation solution. General relativistic effects would be negligible in such an example.

beyubb
2008-Aug-27, 04:10 AM
Thanks for the feedback!!! A tough read indeed! Some of these concepts are hard for me to cough up and still keep concise. I just have to keep trudging though.

Time dilation in a neutron star seems to me to hold potential not just because of the change in frames of reference during one's approach to the surface of the star, but in that possibility that the star has wildly different frames of reference on the interior as well.

My consideration is that the interior of the star is solid (fluid possibly but all in contact with itself), and parts of it are "experiencing" change, time, entropy... at a much faster rate than are adjacent regions. The reason I say this is that it is my possibly flawed understanding that time dilation occurs when there may be a sense of weight or acceleration. In a manner of thinking the surface may be where the most intense dilation would occur, for at any other interior point inside the star gravitational attraction would be diminished, approaching zero at the center as it gets canceled out. Pressure of course would be greatest at the center, but the weight of a thing is heaviest at the surface.

It is on the surface of a neutron star, in this sense of thinking, that “time” would be going the fastest. Time in the center would be slower, approaching "zero?" -well let’s just say nominal...

On the whole, if the neutron star is strictly static, than there may be sections of the star that are several times older than other sections of the star, An interesting thought, even if not experimentally significant. If the star is at all dynamic, than the passage of material from one region to another would be subjected to acceleration in time when moving “up” and the opposite going “down”. Would surface temperature of the neutron star appear as if it were hotter than it might be if the temperature could be read while in the surface area’s frame of reference? Would this radiation perpetually heat the interior?

Thoughts about what the dynamics of actual collapse of the star itself may look like with this in mind are interesting to me as well, to say nothing of where all this gets to when a singularity is thought of. Much of the reading I do on these topics seems not to discuss the aspect of time dilation. Any suggestions?

Cougar
2008-Aug-27, 07:42 PM
...parts of it are "experiencing" change, time, entropy... at a much faster rate than are adjacent regions...

Yes, but only from the "perspective" of the adjacent regions. How is that perspective accomplished?


Neverfly said, "If I was in a capsule in orbit around a Neutron star, and you went to the surface, YES, your time would be severally dilated to a much faster rate than mine."

Now, understand that I could be wrong. I'm not a professional in this field. But from any other vantage point, including from the neutron star's center of gravity, wouldn't time appear to be going slowest on the surface of the neutron star?


If the star is at all dynamic, then the passage of material from one region to another would be subjected to acceleration in time when moving “up” and the opposite going “down”.

As viewed by an external observer. But from the viewpoint of the matter itself, its "clock" would always appear to run normally.


Much of the reading I do on these topics seems not to discuss the aspect of time dilation. Any suggestions?

Kip Thorne - Black Holes and Time Warps, Einstein's Outrageous Legacy [1994]