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  1. #1
    Senior Member Times Roman's Avatar
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    Next thought experiment - physics - think about this one for a bit...

    Again with the black holes.

    I'll just copy and paste from wiki, since I'm drinking wine, and my spelling sucks right at the moment....

    "A black hole is a region of spacetime from which gravity prevents anything, including light, from escaping."

    The issue with the event horizon is that the "escape velocity" in the region between the singularity and the event horizon is greater than the speed of light.

    Easy enough. We've heard this from the egg heads ad naseum, right?

    But what about a theoritical particle called a tachyon? This particle can ONLY move faster than the speed of light.

    So what difficulties would this particle have traversing the space inside a black hole? And once inside, would it be able to exit undisturbed?

    So have a drink, think abouut it, and let me know....

    ---Roman

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    Re: Next thought experiment - physics - think about this one for a bit...

    Tachyons follow space-like curves, and as such their world lines fall outside light cones, which are defined by the possible paths of massless particles that follow light-like curves such as photons. As black holes are defined by light cones, the idea of an event horizon doesn't really apply to a tachyon. (By contrast, non-exotic massive particles obey space-like curves, whose world lines are constrained by light cones, and thus they "fall into" black holes.)

    It's important to not that tachyons aren't "normal particles, but faster"; they're fundamentally different. Whereas non-FTL particles lose energy as they slow down, tachyons lose energy as they speed up. This means that, in particular, forming orbits is difficult for tachyons. One intuitive concept for the event horizon is that it is the orbit of a photon around a black hole. There can be no such stable circular orbit for a tachyon; photons may have a stable orbit, and normal particles might radiate energy and fall to lower orbits, but tachyons would (in general) radiate energy and follow a hyperbolic path out. (In a vacuum, this would take the form of Cherenkov radiation, bizarrely enough.)

    Tachyons without sufficient angular momentum certainly "bounce" out of black holes. (It's debatable what happens to tachyons with sufficient angular momentum. Probably they could be captured by certain types of black holes.) In fact, it's been proposed (semi-seriously) that black holes be be used to detect tachyons --- a feat not yet accomplished --- since tachyons would violate the rules governing all non-FTL particles around black holes and thus would stand out.

    (Most of this goes out the window when you start getting into string theory. I don't keep up with that so I don't know the current thinking, but some flavors of string theory place tachyons as mediators of some important properties of black holes. This isn't completely illogical, if you consider the fact that tachyons and black holes have one major thing in common: they **** with causality.)

    Thanks for the interesting question, been a while since I've thought about this stuff. If you haven't already browsed, there are some interesting semi-recent papers on arxiv.org on the subject, and I've been enjoying them over a couple drinks.

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    Re: Next thought experiment - physics - think about this one for a bit...

    If you want to think about something ****ed-up consider this: tachyons move faster than the speed of light, so you can't "see" them coming. That is, if your method of detection was "seeing" it --- detecting photons that interacted with the tachyon --- then you would detect it leaving you from both directions starting at the moment it reached you.

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    Veteran BigGameHunter's Avatar
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    Re: Next thought experiment - physics - think about this one for a bit...


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    Re: Next thought experiment - physics - think about this one for a bit...

    .....what the hell did I just read?
    sounded cool.

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    Senior Member oldskool954's Avatar
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    Re: Next thought experiment - physics - think about this one for a bit...

    Which parts do I highlight to help with my gains and controlling estrogen?

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    Senior Member Times Roman's Avatar
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    Re: Next thought experiment - physics - think about this one for a bit...

    Originally Posted by dj920 View Post
    Tachyons follow space-like curves, and as such their world lines fall outside light cones, which are defined by the possible paths of massless particles that follow light-like curves such as photons. As black holes are defined by light cones, the idea of an event horizon doesn't really apply to a tachyon. (By contrast, non-exotic massive particles obey space-like curves, whose world lines are constrained by light cones, and thus they "fall into" black holes.)

    It's important to not that tachyons aren't "normal particles, but faster"; they're fundamentally different. Whereas non-FTL particles lose energy as they slow down, tachyons lose energy as they speed up. This means that, in particular, forming orbits is difficult for tachyons. One intuitive concept for the event horizon is that it is the orbit of a photon around a black hole. There can be no such stable circular orbit for a tachyon; photons may have a stable orbit, and normal particles might radiate energy and fall to lower orbits, but tachyons would (in general) radiate energy and follow a hyperbolic path out. (In a vacuum, this would take the form of Cherenkov radiation, bizarrely enough.)

    Tachyons without sufficient angular momentum certainly "bounce" out of black holes. (It's debatable what happens to tachyons with sufficient angular momentum. Probably they could be captured by certain types of black holes.) In fact, it's been proposed (semi-seriously) that black holes be be used to detect tachyons --- a feat not yet accomplished --- since tachyons would violate the rules governing all non-FTL particles around black holes and thus would stand out.

    (Most of this goes out the window when you start getting into string theory. I don't keep up with that so I don't know the current thinking, but some flavors of string theory place tachyons as mediators of some important properties of black holes. This isn't completely illogical, if you consider the fact that tachyons and black holes have one major thing in common: they **** with causality.)

    Thanks for the interesting question, been a while since I've thought about this stuff. If you haven't already browsed, there are some interesting semi-recent papers on arxiv.org on the subject, and I've been enjoying them over a couple drinks.
    the other interesting thing abouut tachyons is that the premise of FTL and einsteins E = mc squared are still consistant due to the theory that tachyons have "imaginary" mass.

    Originally Posted by dj920 View Post
    If you want to think about something ****ed-up consider this: tachyons move faster than the speed of light, so you can't "see" them coming. That is, if your method of detection was "seeing" it --- detecting photons that interacted with the tachyon --- then you would detect it leaving you from both directions starting at the moment it reached you.
    yes, like watching a movie in reverse.

    I'm glad i'm not the only one that thinks about this stuff around here.

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