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Other Discussion Boards => Technology, Science & Alt Science => Topic started by: optimisticcynic on February 25, 2009, 05:32:51 PM

Title: tachyons
Post by: optimisticcynic on February 25, 2009, 05:32:51 PM
tachyons are particles that travel faster then the speed of light and can never go slower then the speed of light and travel back in time. they also have negative energy. Do they break any laws of physics and what would they mean for the universe.
Title: Re: tachyons
Post by: cmdshft on February 25, 2009, 06:06:17 PM
The Star Trek convention called, they want their warp core back.
Title: Re: tachyons
Post by: optimisticcynic on February 25, 2009, 06:24:00 PM
Just because it was in star trek does not mean that it is an idiotic theory. >:(
Title: Re: tachyons
Post by: Jack on February 25, 2009, 06:40:11 PM
Do they break any laws of physics
In terms of FTL, the tachyon definitely breaks a few laws in special relativity, but it seems reasonable in general relativity due to space-time distortions. E.g. worm holes. However, the tachyon and FTL are still only hypothetical terms in modern science.

and what would they mean for the universe.
Obviously, it's most likely used to propagate information.
Title: Re: tachyons
Post by: Soul Eater on February 25, 2009, 06:52:50 PM
In terms of FTL, the tachyon definitely breaks a few laws in special relativity, but it seems reasonable in general relativity due to space-time distortions. E.g. worm holes. However, the tachyon and FTL are still only hypothetical terms in modern science.
For the most part tachyons agree with special relativity, don't they?  What laws do they actually break?
Title: Re: tachyons
Post by: cmdshft on February 25, 2009, 06:58:34 PM
In terms of FTL, the tachyon definitely breaks a few laws in special relativity, but it seems reasonable in general relativity due to space-time distortions. E.g. worm holes. However, the tachyon and FTL are still only hypothetical terms in modern science.
For the most part tachyons agree with special relativity, don't they?  What laws do they actually break?


They would only break the law of causality if they were used to transmit data theoretically. The effect of a passing tachyon would be similar to the effect of a fighter jet breaking mach 1.

There's a wiki article on the subject, but it deals partially with string theory which I don't particularly subscribe to.
Title: Re: tachyons
Post by: JoshuaZ on February 25, 2009, 06:59:16 PM

In terms of FTL, the tachyon definitely breaks a few laws in special relativity, but it seems reasonable in general relativity due to space-time distortions. E.g. worm holes. However, the tachyon and FTL are still only hypothetical terms in modern science.

Obviously, it's most likely used to propagate information.

You know, it could help if you actually opened your mouth when you had some understanding. Tachyons don't have any special or general relativity issue. They were hypothesized precisely because they are consistent with the relevant equations. They have nothing to do whatsoever with worm holes. Tachyons would not travel through odd topological structures but in functionally normal space.

Tachyons also cannot be used to propagate information faster than light speed. Roughly speaking, that would require them to violate causality in somebody's light cone something which would make special relativity a sad panda.  The physics behind why they don't violate causality is more complicated (and the details are a bit beyond me).

For the more technically inclined: The total energy of a particle under special relativity is (mc^2)/(1- v^2/c^2) (There may be some normalization of units to get this equation. Not sure. Haven't done this in a while). Now, when v exceeds c, (that is you have a tachyon) the bottom becomes the square root of a negative number, so either energy or mass needs to be thought of as an imaginary number. This turns out to be more or less ok when tachyons are interacting only with each other but leads to bad stuff if they need to interact with normal particles. Thinking further along these lines is what leads morally speaking to the conclusion that tachyons can't go slow down to the speed of light or below it.  

There's an important alternative definition of a tachyon: A gluon that isn't quite dry.
Title: Re: tachyons
Post by: Jack on February 25, 2009, 07:20:02 PM
Tachyons don't have any special relativity issue.
Uh, yes they do. Special relativity forbids any object to travel faster than the speed of light. Relative to all inertial observers, massless particles travel at c. Relative to all inertial observers, massive particles (or any particles with mass) may approach c but never get to or past c. Get your facts straight.

They have nothing to do whatsoever with worm holes.
I never said they have anything to do with worm holes. I said general relativity may allow FTL due to space-time distortion, e.g. wormholes.

http://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/FTL.html#20

For the most part tachyons agree with special relativity, don't they?  What laws do they actually break?
Special relativity forbids anything to travel faster than the speed of light.
Title: Re: tachyons
Post by: Soul Eater on February 25, 2009, 07:25:11 PM
Tachyons don't have any special relativity issue.
Uh, yes they do. Special relativity forbids any object to travel faster than the speed of light. Relative to all inertial observers, massless particles travel at c. Relative to all inertial observers, massive particles (or any particles with mass) may approach c but never get to or past c. Get your facts straight.

They have nothing to do whatsoever with worm holes.
I never said they have anything to do with worm holes. I said general relativity may allow FTL due to space-time distortion, e.g. wormholes.

http://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/FTL.html#20

For the most part tachyons agree with special relativity, don't they?  What laws do they actually break?
Special relativity forbids anything to travel faster than the speed of light.
Special relativity doesn't forbid FLT.  It forbids anything from accelerating past the speed of light, which would require infinite energy.  Tachyons are always moving faster than light, thus there is no energy barrier to cross.
Title: Re: tachyons
Post by: cmdshft on February 25, 2009, 07:27:32 PM
http://en.wikipedia.org/wiki/Tachyon
Title: Re: tachyons
Post by: JoshuaZ on February 25, 2009, 07:28:15 PM

Special relativity forbids anything to travel faster than the speed of light.

No it doesn't. This is a common misconception. Please take a physics course.

If a particle's rest mass is a positive real number then the particle cannot accelerate to or beyond the speed of light. If a particle's rest mass is zero then it must travel at the speed of light. If a particle's rest mass is imaginary then the particle travels faster than the speed of light and cannot accelerate below it. (I'm abusing notation slightly with the term rest mass only being strictly valid for the first of the three cases)

Tachyons were in fact first thought about because they turned up as apparent consistent solutions to the equations for special relativity much as how the positron was first conjectured to exist because they turned up as additional solutions to Dirac's equation.

Also wormholes strictly speaking are not a form of FLT. Any traveler cannot beat light traveling through the wormhole.
Title: Re: tachyons
Post by: optimisticcynic on February 25, 2009, 07:53:05 PM
wouldn't tachyons not interact with matter anyway. They have negative mass which would give them negative gravity so they would be repelled by the galaxy.
Title: Re: tachyons
Post by: Jack on February 25, 2009, 07:55:39 PM
No it doesn't. This is a common misconception. Please take a physics course.
Yes it does, especially to objects with mass. No information can travel faster than the speed of light. Massless particles travel at c. It's compelling to think SR allows FTL due to the tachyon; that's a common misconception.

Quote from: http://en.wikipedia.org/wiki/Faster-than-light#Space-time_distortion
Space-time distortion

Although the theory of special relativity forbids objects to have a relative velocity greater than light speed, and general relativity reduces to special relativity in a local sense (in small regions of spacetime where curvature is negligible), general relativity does allow the space between distant objects to expand in such a way that they have a "recession velocity" which exceeds the speed of light, and it is thought that galaxies which are at a distance of more than about 14 billion light years from us today have a recession velocity which is faster than light.
As I've said, GR may allow FTL, but not SR.

Quote from: http://metaresearch.org/cosmology/gravity/LR.asp
The proof that faster-than-light (FTL) propagation is not allowed by nature is simple. Special relativity (SR) forbids it because, in that theory, time slows and approaches a cessation of flow for any material entity approaching the speed of light. One might immediately object that, in particle accelerators, the behavior predicted by SR is observed to happen as speeds approach c. No matter how much energy is added, the particles cannot be made to reach or exceed speed c.
As I've said before, relative to all inertial observers, a massless particle travel at c, whereas a massive particle may accelerate and approach c.

If a particle's rest mass is imaginary then the particle travels faster than the speed of light and cannot accelerate below it. (I'm abusing notation slightly with the term rest mass only being strictly valid for the first of the three cases)
So, what is the value of this imaginary mass of a tachyon?

Also wormholes strictly speaking are not a form of FLT.
Please read my link.

It forbids anything from accelerating past the speed of light
I'm pretty sure that's what I just said.
Title: Re: tachyons
Post by: optimisticcynic on February 25, 2009, 08:02:39 PM
In terms of FTL, the tachyon definitely breaks a few laws in special relativity, but it seems reasonable in general relativity due to space-time distortions. E.g. worm holes. However, the tachyon and FTL are still only hypothetical terms in modern science.
For the most part tachyons agree with special relativity, don't they?  What laws do they actually break?


They would only break the law of causality if they were used to transmit data theoretically. The effect of a passing tachyon would be similar to the effect of a fighter jet breaking mach 1.

There's a wiki article on the subject, but it deals partially with string theory which I don't particularly subscribe to.

Tachyons wouldn't break causality from what I understand. If you made a tachyon detector it would create tachyons that would create Something that would be considered static so you couldn't figure out which tachyon sent the info and which were created by the tachyon detector. thus no information is sent into the past.
Also tachyons would have been going faster then the speed of light since the big bang and would have never passed the speed of light
Title: Re: tachyons
Post by: cmdshft on February 25, 2009, 08:06:09 PM
wouldn't tachyons not interact with matter anyway. They have negative mass which would give them negative gravity so they would be repelled by the galaxy.

Actually, no. Technically, using that logic, knowing that having positive mass expands space-time (thus having positive time passage due to the distance between two masses), having negative mass would be the reverse. I'm not 100% on that, I'm just going by your logic to make more sense, I am not sure if that is actually how it would work, but it would explain why tachyons would be able to travel faster than light. They would not be repelled by any positive mass. If anything, they would be of the same nature of neutrinos as far as interactions go with our current knowledge and technology level.

Tachyons wouldn't break causality from what I understand. If you made a tachyon detector it would create tachyons that would create Something that would be considered static so you couldn't figure out which tachyon sent the info and which were created by the tachyon detector. thus no information is sent into the past.
Also tachyons would have been going faster then the speed of light since the big bang and would have never passed the speed of light

I know they wouldn't. Causality is only possible when handling data. As long as the tachyons aren't being used in a way to transmit data, they will not break causality.

Also, causality is not dependent on detection or any sort of cypher. If ANY data is sent on or by a tachyon, it could cause a breakdown. How much the extent of the breakdown is would be dependent on the type and amount of data transmitted.

Also, Jack, please read the wiki article.
Title: Re: tachyons
Post by: JoshuaZ on February 25, 2009, 08:12:09 PM
Yes it does, especially to objects with mass.

What does that mean? It either allows them or not, it can't not allow something and especially not in other cases.

Quote
No information can travel faster than the speed of light.

Not exactly but not relevant either. You can't use tachyons to transmit information faster than the speed of light.

Quote
Quote from: http://en.wikipedia.org/wiki/Faster-than-light#Space-time_distortion
Space-time distortion

Although the theory of special relativity forbids objects to have a relative velocity greater than light speed, and general relativity reduces to special relativity in a local sense (in small regions of spacetime where curvature is negligible), general relativity does allow the space between distant objects to expand in such a way that they have a "recession velocity" which exceeds the speed of light, and it is thought that galaxies which are at a distance of more than about 14 billion light years from us today have a recession velocity which is faster than light.
As I've said, GR may allow FTL, but not SR.

Mein Gott. Please take a physics course, don't just quote Wikipedia. Nothing in that statement is at all contradictory to anything I've said. Expansion of space is a completely separate issue which has nothing at all to do with tachyons.

Quote
Quote from: http://metaresearch.org/cosmology/gravity/LR.asp

The proof that faster-than-light (FTL)
propagation is not allowed by nature is simple. Special relativity (SR) forbids it because, in that theory, time slows and approaches a cessation of flow for any material entity approaching the speed of light. One might immediately object that, in particle accelerators, the behavior predicted by SR is observed to happen as speeds approach c. No matter how much energy is added, the particles cannot be made to reach or exceed speed c.
As I've said before, relative to all inertial observers, a massless particle travel at c, whereas a massive particle may accelerate and approach c.


I'm resisting the urge to flame here. Do you maybe want to check out what random websites you are quoting from? Metaresearch is some crank's personal site. In any event, this is a quite poor explanation Time dilation is a related effect but not the reason you can't accelerate an object with mass faster than the speed of light. And again, this is all only relevant if you have positive real rest mass.

Quote
If a particle's rest mass is imaginary then the particle travels faster than the speed of light and cannot accelerate below it. (I'm abusing notation slightly with the term rest mass only being strictly valid for the first of the three cases)
So, what is the value of this imaginary mass of a tachyon?

It is a function of the rest mass and the current velocity. But strictly speaking, there are no restrictions on the rest mass of a tachyon within special relativity beyond that it needs to be a non-zero imaginary number. But like all particles you have E= (mc^2)/(1- v^2/c^2)^(1/2) where m is the rest mass and E is the total energy (you get Einstein's well known equation from setting v=0 in the above).

Quote
Please read my link.

Please take a physics course.

Edit:Formatting
Title: Re: tachyons
Post by: optimisticcynic on February 25, 2009, 08:18:42 PM
wouldn't tachyons not interact with matter anyway. They have negative mass which would give them negative gravity so they would be repelled by the galaxy.

Actually, no. Technically, using that logic, knowing that having positive mass expands space-time (thus having positive time passage due to the distance between two masses), having negative mass would be the reverse. I'm not 100% on that, I'm just going by your logic to make more sense, I am not sure if that is actually how it would work, but it would explain why tachyons would be able to travel faster than light. They would not be repelled by any positive mass. If anything, they would be of the same nature of neutrinos as far as interactions go with out current knowledge and technology level.
you cant contract space. picture a piece of rubber stretched into a thin sheet. a piece of mass would seem to increase the space time. However if you put a balloon underneath it would do the exact opposite as a object with weight but would still increase the amount of space
Title: Re: tachyons
Post by: cmdshft on February 25, 2009, 08:20:06 PM
wouldn't tachyons not interact with matter anyway. They have negative mass which would give them negative gravity so they would be repelled by the galaxy.

Actually, no. Technically, using that logic, knowing that having positive mass expands space-time (thus having positive time passage due to the distance between two masses), having negative mass would be the reverse. I'm not 100% on that, I'm just going by your logic to make more sense, I am not sure if that is actually how it would work, but it would explain why tachyons would be able to travel faster than light. They would not be repelled by any positive mass. If anything, they would be of the same nature of neutrinos as far as interactions go with out current knowledge and technology level.
you cant contract space. picture a piece of rubber stretched into a thin sheet. a piece of mass would seem to increase the space time. However if you put a balloon underneath it would do the exact opposite as a object with weight but would still increase the amount of space

You can contract space-time, though. Space and space-time are two different things.
Title: Re: tachyons
Post by: optimisticcynic on February 25, 2009, 08:27:28 PM
wouldn't it just stretch space time out the opposite direction. Also matters with a positive mass is attracted to space time that has been warped in that direction tachyons stretch it in the other way so wouldn't it be repelled matters way of stretching it.
Title: Re: tachyons
Post by: Jack on February 25, 2009, 08:28:57 PM
What does that mean? It either allows them or not, it can't not allow something and especially not in other cases.
It means objects with mass cannot accelerate past (or, in layman terms, travel past) the speed of light. Make sense now?

Not exactly but not relevant either. You can't use tachyons to transmit information faster than the speed of light.
I said nothing about tachyons.

Mein Gott. Please take a physics course, don't just quote Wikipedia. Nothing in that statement is at all contradictory to anything I've said.
Sure there is.

Metaresearch is some crank's personal site.
Especially when the page cited quite a few sources to back it up?

Expansion of space is a completely separate issue which has nothing at all to do with tachyons.
We're not arguing about that. Please be consistent with the discussion.

Time dilation is a related effect but not the reason you can't accelerate an object with mass faster than the speed of light. And again, this is all only relevant if you have positive real rest mass.
You can't accelerate an object with mass faster than the speed of light, under SR. Period.

It is a function of the rest mass and the current velocity. But strictly speaking, there are no restrictions on the rest mass of a tachyon within special relativity beyond that it needs to be a non-zero imaginary number. But like all particles you have E= (mc^2)/(1- v^2/c^2)^(1/2) where m is the rest mass and E is the total energy (you get Einstein's well known equation from setting v=0 in the above).
So, what is the value of this imaginary mass of a tachyon just so it doesn't violate SR?

Please take a physics course.
Good, so you have nothing to add to your argument. Gotcha.
Title: Re: tachyons
Post by: cmdshft on February 25, 2009, 08:37:19 PM
wouldn't it just stretch space time out the opposite direction. Also matters with a positive mass is attracted to space time that has been warped in that direction tachyons stretch it in the other way so wouldn't it be repelled matters way of stretching it.

Mass creates gravity. Gravity stretches space-time. That's why if you were to fall into the gravity well of a black hole, an outside observer would see your body slow down to a near standstill as you approach it's event horizon. It takes longer and longer to reach the next point. An object such as a tachyon with negative mass would possibly shrink space-time, and could be why it propels through space at FTL speeds. It's basically shrinking the space-time in front of it, and stretching out space-time behind it as it moves.

(http://upload.wikimedia.org/wikipedia/en/7/7b/Tachyon-200px.gif)

It's also theorized (this is where Star Trek actually stole the idea from) that if you could somehow make a tachyon "field" you would effectively negate the mass of anything inside this field, which would allow the object to be exempt from GR and SR altogether and move along at FTL speeds. Although, Star Trek adds that it simply shifts the mass into subspace, but that's just to be special I believe.
Title: Re: tachyons
Post by: optimisticcynic on February 25, 2009, 08:52:47 PM
wouldn't it just stretch space time out the opposite direction. Also matters with a positive mass is attracted to space time that has been warped in that direction tachyons stretch it in the other way so wouldn't it be repelled matters way of stretching it.

Mass creates gravity. Gravity stretches space-time. That's why if you were to fall into the gravity well of a black hole, an outside observer would see your body slow down to a near standstill as you approach it's event horizon. It takes longer and longer to reach the next point. An object such as a tachyon with negative mass would possibly shrink space-time, and could be why it propels through space at FTL speeds. It's basically shrinking the space-time in front of it, and stretching out space-time behind it as it moves.

(http://upload.wikimedia.org/wikipedia/en/7/7b/Tachyon-200px.gif)

It's also theorized (this is where Star Trek actually stole the idea from) that if you could somehow make a tachyon "field" you would effectively negate the mass of anything inside this field, which would allow the object to be exempt from GR and SR altogether and move along at FTL speeds. Although, Star Trek adds that it simply shifts the mass into subspace, but that's just to be special I believe.
The fact something seems to slow down as it approaches a black hole has nothing  to do with stretching of space time. it has to do with what happens to the light in the gravity.
So if it did warp space time one way it should be attracted to things that warp it the same way and repelled by thing that warp it the opposite way. So it should still be repelled by the gravity of are galaxy.
Title: Re: tachyons
Post by: JoshuaZ on February 25, 2009, 08:53:48 PM
wouldn't it just stretch space time out the opposite direction. Also matters with a positive mass is attracted to space time that has been warped in that direction tachyons stretch it in the other way so wouldn't it be repelled matters way of stretching it.

The underlying material with gravity is complicated. I don't understand it well at all (my understanding of GR isn't very good). But I can be sure that the gravitational issues with tachyons are not going to be easily noodlable without a lot more math. This is a waste of time.

And now to deal with Jack...

Quote
It means objects with mass cannot accelerate past (or, in layman terms, travel past) the speed of light. Make sense now?
.

Ok, if that's what you meant then it is confused. This is only true for objects with positive real mass.

Quote
Expansion of space is a completely separate issue which has nothing at all to do with tachyons.
We're not arguing about that. Please be consistent with the discussion.

Well excuse me for replying to what you quoted from Wikipedia. You seem to be missing the point. That's about travel within space (roughly speaking, the details are more complicated).

Quote
You can't accelerate an object with mass faster than the speed of light, under SR. Period.

You can't accelerate an object with positive real rest mass faster than the speed of light under SR. That's not the same. Tachyons don't have a positive real rest mass.

Quote
It is a function of the rest mass and the current velocity. But strictly speaking, there are no restrictions on the rest mass of a tachyon within special relativity beyond that it needs to be a non-zero imaginary number. But like all particles you have E= (mc^2)/(1- v^2/c^2)^(1/2) where m is the rest mass and E is the total energy (you get Einstein's well known equation from setting v=0 in the above).
So, what is the value of this imaginary mass of a tachyon just so it doesn't violate SR?

Some number of the form ki for k a non-zero real number.

Quote
Please take a physics course.
Good, so you have nothing to add to your argument. Gotcha.

There's no need for a new argument. If you don't understand the relevant equations that's not my fault.  If you don't have time to take a physics course then crack open a book on special relativity.

Ok. Last attempt to explain this. Trying another tact. Let's think what goes wrong when we try to accelerate an object to the speed of light. Quick change of notation. I'm going to use capital M as the rest mass and little m as the relativistic mass. SR says in part that for normal particles relative mass is increases as we increase velocity. In fact, it says a bit more, namely that for any particle we have m(1- v^2/c^2)^(1/2)= M or if you prefer m= M/(1- v^2/c^2)^(1/2).  Now, if M and m are non-zero then we get a problem if v=c because in that case we would have 1-v^2/c^2=0 and so we would get M*0=0=m which would be bad. Now, if m=M=0 this isn't a problem. That's why particles with mass zero can go the speed of light (for other reasons they have to go the speed of light). We similarly get a problem if we let v exceed c because we get an imaginary number if we have v>c. But, that's ok if we allow M or m to be imaginary numbers. The equations are consistent. If you look at the other relevant equations of SR you'll find that they are also consistent but you get strange acting particles. In particular, these particles still have the same problem if you try to set v=c so you can't ever get these particles to the speed of light. There are some other weird issues here and I'm a number theorist not a physicist so I don't feel comfortable going into that much more detail without picking up a textbook but that's the basic idea.
Title: Re: tachyons
Post by: cmdshft on February 25, 2009, 08:54:35 PM
wouldn't it just stretch space time out the opposite direction. Also matters with a positive mass is attracted to space time that has been warped in that direction tachyons stretch it in the other way so wouldn't it be repelled matters way of stretching it.

Mass creates gravity. Gravity stretches space-time. That's why if you were to fall into the gravity well of a black hole, an outside observer would see your body slow down to a near standstill as you approach it's event horizon. It takes longer and longer to reach the next point. An object such as a tachyon with negative mass would possibly shrink space-time, and could be why it propels through space at FTL speeds. It's basically shrinking the space-time in front of it, and stretching out space-time behind it as it moves.

(http://upload.wikimedia.org/wikipedia/en/7/7b/Tachyon-200px.gif)

It's also theorized (this is where Star Trek actually stole the idea from) that if you could somehow make a tachyon "field" you would effectively negate the mass of anything inside this field, which would allow the object to be exempt from GR and SR altogether and move along at FTL speeds. Although, Star Trek adds that it simply shifts the mass into subspace, but that's just to be special I believe.
The fact something seems to slow down as it approaches a black hole has nothing  to do with stretching of space time. it has to do with what happens to the light in the gravity.
So if it did warp space time one way it should be attracted to things that warp it the same way and repelled by thing that warp it the opposite way. So it should still be repelled by the gravity of are galaxy.

No. Please educate yourself on newtonian physics and general relativity and how the two interact with one another as far as black holes and gravity are concerned.
Title: Re: tachyons
Post by: optimisticcynic on February 25, 2009, 09:02:19 PM
wouldn't it just stretch space time out the opposite direction. Also matters with a positive mass is attracted to space time that has been warped in that direction tachyons stretch it in the other way so wouldn't it be repelled matters way of stretching it.

Mass creates gravity. Gravity stretches space-time. That's why if you were to fall into the gravity well of a black hole, an outside observer would see your body slow down to a near standstill as you approach it's event horizon. It takes longer and longer to reach the next point. An object such as a tachyon with negative mass would possibly shrink space-time, and could be why it propels through space at FTL speeds. It's basically shrinking the space-time in front of it, and stretching out space-time behind it as it moves.

(http://upload.wikimedia.org/wikipedia/en/7/7b/Tachyon-200px.gif)

It's also theorized (this is where Star Trek actually stole the idea from) that if you could somehow make a tachyon "field" you would effectively negate the mass of anything inside this field, which would allow the object to be exempt from GR and SR altogether and move along at FTL speeds. Although, Star Trek adds that it simply shifts the mass into subspace, but that's just to be special I believe.
The fact something seems to slow down as it approaches a black hole has nothing  to do with stretching of space time. it has to do with what happens to the light in the gravity.
So if it did warp space time one way it should be attracted to things that warp it the same way and repelled by thing that warp it the opposite way. So it should still be repelled by the gravity of are galaxy.

No. Please educate yourself on newtonian physics and general relativity and how the two interact with one another as far as black holes and gravity are concerned.

The light closer to the event horizon of a black hole takes longer to reach you. SO the image that you see of someone who is almost about to fall into a black hole takes longer to reach you then it would without the gravity well. As you get closer and closer it takes the light longer and longer to escape. So you would never actually see someone fall into a black hole they would just get exponentially closer. even though the object probably fell through along time ago.
Title: Re: tachyons
Post by: cmdshft on February 25, 2009, 09:20:09 PM
No, that's not how it works at all. It has NOTHING to do with light at all, as light is subject to the same effects. As I said, please educate yourself a bit more, it's clear you don't understand how it works fully.
Title: Re: tachyons
Post by: Jack on February 25, 2009, 11:01:30 PM
Ok, if that's what you meant then it is confused. This is only true for objects with positive real mass.
What is a real mass?

Some number of the form ki for k a non-zero real number.
Right, you can't give me a number. Talk about hypothetical nonsense...

There's no need for a new argument. If you don't understand the relevant equations that's not my fault.  If you don't have time to take a physics course then crack open a book on special relativity.
I'm not asking for a new argument.

I'm going to use capital M as the rest mass and little m as the relativistic mass.
No, it's the other way around: m = invariant mass, M = relativistic mass.

SR says in part that for normal particles relative mass is increases as we increase velocity.
Not necessarily. Please, replace relativistic mass with energy, as it removes confusion. In fact, even Einstein disliked (http://www.weburbia.com/physics/mass.html) the idea of relativistic mass. When we say mass, we mean invariant (rest) mass.

Ok. Last attempt to explain this. Trying another tact. Let's think what goes wrong when we try to accelerate an object to the speed of light. Quick change of notation. I'm going to use capital M as the rest mass and little m as the relativistic mass. SR says in part that for normal particles relative mass is increases as we increase velocity. In fact, it says a bit more, namely that for any particle we have m(1- v^2/c^2)^(1/2)= M or if you prefer m= M/(1- v^2/c^2)^(1/2).  Now, if M and m are non-zero then we get a problem if v=c because in that case we would have 1-v^2/c^2=0 and so we would get M*0=0=m which would be bad. Now, if m=M=0 this isn't a problem. That's why particles with mass zero can go the speed of light (for other reasons they have to go the speed of light). We similarly get a problem if we let v exceed c because we get an imaginary number if we have v>c. But, that's ok if we allow M or m to be imaginary numbers. The equations are consistent. If you look at the other relevant equations of SR you'll find that they are also consistent but you get strange acting particles. In particular, these particles still have the same problem if you try to set v=c so you can't ever get these particles to the speed of light. There are some other weird issues here and I'm a number theorist not a physicist so I don't feel comfortable going into that much more detail without picking up a textbook but that's the basic idea.
I've yet to see a contradiction to my claim:

Relative to all inertial observers, massless particles travel at c. Relative to all inertial observers, massive particles (or any particles with mass) may approach c but never get to or past c.
Title: Re: tachyons
Post by: JoshuaZ on February 26, 2009, 08:05:26 AM
What is a real mass?

A mass that is a real number.

Quote
Some number of the form ki for k a non-zero real number.
Right, you can't give me a number. Talk about hypothetical nonsense...

I can't give you a specific number because any specific number will do, just as the standard equations for SR are valid for any chosen mass as long as you adjust energy and other values accordingly. You might as well ask for a specific mass for a regular particle.

Quote
I'm going to use capital M as the rest mass and little m as the relativistic mass.
No, it's the other way around: m = invariant mass, M = relativistic mass.
Sorry, screwed the notation up there.

Quote
I've yet to see a contradiction to my claim:
Relative to all inertial observers, massless particles travel at c. Relative to all inertial observers, massive particles (or any particles with mass) may approach c but never get to or past c.

Ok. Let's be explicit: Your statement is wrong.
Because that's only true for massive particles whose mass is a real number. If the mass is an imaginary number then the particle has to start out faster than c and can't slow down past c. See the issue?
Title: Re: tachyons
Post by: optimisticcynic on February 26, 2009, 08:47:37 AM
No, that's not how it works at all. It has NOTHING to do with light at all, as light is subject to the same effects. As I said, please educate yourself a bit more, it's clear you don't understand how it works fully.
here is a source http://math.ucr.edu/home/baez/physics/Relativity/BlackHoles/fall_in.html I can find more if you don't trust this one.
Title: Re: tachyons
Post by: MotherNature on February 26, 2009, 11:54:03 AM

lol some people in this thread haven't got a clue about physics or relativity.

I teach university physics I have a PhD, admitedly in condensed matter physics.

A particle can travel faster than the speed of light if it has zero rest mass i.e. the mass of the particle at rest in ALL inertial frames of reference. Any particle that moves has a mass associated with it due to it's movement.

Some of the physics stated in this thread is shocking tbh.
Title: Re: tachyons
Post by: Jack on February 26, 2009, 12:04:33 PM
I can't give you a specific number because any specific number will do, just as the standard equations for SR are valid for any chosen mass as long as you adjust energy and other values accordingly. You might as well ask for a specific mass for a regular particle.
Rest mass of a photon = 0. Not as hypothetical as the tachyon, doesn't it?

Ok. Let's be explicit: Your statement is wrong.
Really, so massless particles can go faster than the speed of light, while massive particles can accelerate past the speed of light?

Because that's only true for massive particles whose mass is a real number. If the mass is an imaginary number then the particle has to start out faster than c and can't slow down past c. See the issue?
I'm talking about my statement.

Here, if you can actually read.
Quote
Relative to all inertial observers, massless particles travel at c. Relative to all inertial observers, massive particles (or any particles with mass) may approach c but never get to or past c.
Title: Re: tachyons
Post by: cmdshft on February 26, 2009, 12:06:45 PM

lol some people in this thread haven't got a clue about physics or relativity.

I teach university physics I have a PhD, admitedly in condensed matter physics.

A particle can travel faster than the speed of light if it has zero rest mass i.e. the mass of the particle at rest in ALL inertial frames of reference. Any particle that moves has a mass associated with it due to it's movement.

Some of the physics stated in this thread is shocking tbh.

I've been trying to explain this as well, but no one seems to get it.
Title: Re: tachyons
Post by: MotherNature on February 26, 2009, 12:17:23 PM
I can't give you a specific number because any specific number will do, just as the standard equations for SR are valid for any chosen mass as long as you adjust energy and other values accordingly. You might as well ask for a specific mass for a regular particle.
Rest mass of a photon = 0. Not as hypothetical as the tachyon, doesn't it?

Ok. Let's be explicit: Your statement is wrong.
Really, so massless particles can go faster than the speed of light, while massive particles can accelerate past the speed of light?

Because that's only true for massive particles whose mass is a real number. If the mass is an imaginary number then the particle has to start out faster than c and can't slow down past c. See the issue?
I'm talking about my statement.

Here, if you can actually read.
Quote
Relative to all inertial observers, massless particles travel at c. Relative to all inertial observers, massive particles (or any particles with mass) may approach c but never get to or past c.

Have a read of this

http://en.wikipedia.org/wiki/Rest_mass
Title: Re: tachyons
Post by: JoshuaZ on February 26, 2009, 12:46:02 PM

lol some people in this thread haven't got a clue about physics or relativity.

I teach university physics I have a PhD, admitedly in condensed matter physics.

A particle can travel faster than the speed of light if it has zero rest mass i.e. the mass of the particle at rest in ALL inertial frames of reference. Any particle that moves has a mass associated with it due to it's movement.

Some of the physics stated in this thread is shocking tbh.

I don't think I've said anything wrong or contradicting what you've said. If I've said anything wrong in particular please let me know.
Title: Re: tachyons
Post by: MotherNature on February 26, 2009, 12:53:15 PM

lol some people in this thread haven't got a clue about physics or relativity.

I teach university physics I have a PhD, admitedly in condensed matter physics.

A particle can travel faster than the speed of light if it has zero rest mass i.e. the mass of the particle at rest in ALL inertial frames of reference. Any particle that moves has a mass associated with it due to it's movement.

Some of the physics stated in this thread is shocking tbh.

I don't think I've said anything wrong or contradicting what you've said. If I've said anything wrong in particular please let me know.

woops sorry I quoted the wrong person :P
Title: Re: tachyons
Post by: Jack on February 26, 2009, 02:53:59 PM
A particle can travel faster than the speed of light if it has zero rest mass i.e. the mass of the particle at rest in ALL inertial frames of reference.
So photons can travel faster than the speed of light?

Any particle that moves has a mass associated with it due to it's movement.
A photon can move without invariant mass, but with energy. You don't know what you're talking about.

Some of the physics stated in this thread is shocking tbh.
Says the "Ph.D professor" who doesn't even understand physics.

Have a read of this

http://en.wikipedia.org/wiki/Rest_mass
And?
Title: Re: tachyons
Post by: optimisticcynic on February 26, 2009, 06:11:06 PM

lol some people in this thread haven't got a clue about physics or relativity.

I teach university physics I have a PhD, admitedly in condensed matter physics.

A particle can travel faster than the speed of light if it has zero rest mass i.e. the mass of the particle at rest in ALL inertial frames of reference. Any particle that moves has a mass associated with it due to it's movement.

Some of the physics stated in this thread is shocking tbh.
A. I would like to hear your complaints about anything I have said.
B. If a tachyon went by a galaxy would it curve towards the galaxy or away from it because of gravity
Title: Re: tachyons
Post by: MotherNature on February 26, 2009, 06:24:01 PM
A particle can travel faster than the speed of light if it has zero rest mass i.e. the mass of the particle at rest in ALL inertial frames of reference.
So photons can travel faster than the speed of light?

Any particle that moves has a mass associated with it due to it's movement.
A photon can move without invariant mass, but with energy. You don't know what you're talking about.

Some of the physics stated in this thread is shocking tbh.
Says the "Ph.D professor" who doesn't even understand physics.

Have a read of this

http://en.wikipedia.org/wiki/Rest_mass
And?

Did you read it instead of putting And?

Also I'm not a professor. I don't teach in America. I teach in the UK.
Title: Re: tachyons
Post by: Jack on February 26, 2009, 06:29:42 PM
Did you read it instead of putting And?
How does your link contradict to anything I said?

Also I'm not a professor. I don't teach in America. I teach in the UK.
I feel sorry for your students.
Title: Re: tachyons
Post by: Euclid on February 26, 2009, 06:50:56 PM
Um, Jack, I don't think you are getting the fact that tachyons are able to travel faster than the speed of light because they have an imaginary mass.  There is nothing inconsistent with SR about it.
Title: Re: tachyons
Post by: Jack on February 26, 2009, 06:53:44 PM
I know that. I, however, is questioning MotherNature's credibility.
Title: Re: tachyons
Post by: Euclid on February 26, 2009, 06:55:14 PM
Oh, I was referring to your debate with JoshuaZ.
Title: Re: tachyons
Post by: Jack on February 26, 2009, 07:13:51 PM
Yeah, I was a little too rushy there. I was merely trying to question the existence of such particles.
Title: Re: tachyons
Post by: optimisticcynic on February 26, 2009, 07:16:37 PM
wouldn't it just stretch space time out the opposite direction. Also matters with a positive mass is attracted to space time that has been warped in that direction tachyons stretch it in the other way so wouldn't it be repelled matters way of stretching it.

Mass creates gravity. Gravity stretches space-time. That's why if you were to fall into the gravity well of a black hole, an outside observer would see your body slow down to a near standstill as you approach it's event horizon. It takes longer and longer to reach the next point. An object such as a tachyon with negative mass would possibly shrink space-time, and could be why it propels through space at FTL speeds. It's basically shrinking the space-time in front of it, and stretching out space-time behind it as it moves.

(http://upload.wikimedia.org/wikipedia/en/7/7b/Tachyon-200px.gif)

It's also theorized (this is where Star Trek actually stole the idea from) that if you could somehow make a tachyon "field" you would effectively negate the mass of anything inside this field, which would allow the object to be exempt from GR and SR altogether and move along at FTL speeds. Although, Star Trek adds that it simply shifts the mass into subspace, but that's just to be special I believe.
The fact something seems to slow down as it approaches a black hole has nothing  to do with stretching of space time. it has to do with what happens to the light in the gravity.
So if it did warp space time one way it should be attracted to things that warp it the same way and repelled by thing that warp it the opposite way. So it should still be repelled by the gravity of are galaxy.

No. Please educate yourself on newtonian physics and general relativity and how the two interact with one another as far as black holes and gravity are concerned.
Did you read the source? it agreed with what I said about seeing something falling into a black hole. would you like me to go and find other sources that also agree with me. I believe a brief history of time also mentions it . or would you rather keep saying I don't understand the subject?
Title: Re: tachyons
Post by: cmdshft on February 26, 2009, 07:37:24 PM
You're wrong because I am not talking about light, I am talking about space-time. The black hole metaphor was an example, you went off on the wrong tangent with it. So again, please educate yourself.
Title: Re: tachyons
Post by: optimisticcynic on February 26, 2009, 07:51:11 PM
You're wrong because I am not talking about light, I am talking about space-time. The black hole metaphor was an example, you went off on the wrong tangent with it. So again, please educate yourself.
I explained why an object appears to slow down as it approaches the event horizon. It will still go through the event horizon but to the out side observer they never reach the event horizon. If that doesn't demonstrate what you were talking about then you should have picked a better example.
Title: Re: tachyons
Post by: cmdshft on February 26, 2009, 08:01:41 PM
You're wrong because I am not talking about light, I am talking about space-time. The black hole metaphor was an example, you went off on the wrong tangent with it. So again, please educate yourself.
I explained why an object appears to slow down as it approaches the event horizon. It will still go through the event horizon but to the out side observer they never reach the event horizon. If that doesn't demonstrate what you were talking about then you should have picked a better example.

Again, not what we're discussing. The example was used to explain the idea of expansion and compression of space-time.
Title: Re: tachyons
Post by: optimisticcynic on February 26, 2009, 08:11:36 PM
You're wrong because I am not talking about light, I am talking about space-time. The black hole metaphor was an example, you went off on the wrong tangent with it. So again, please educate yourself.
I explained why an object appears to slow down as it approaches the event horizon. It will still go through the event horizon but to the out side observer they never reach the event horizon. If that doesn't demonstrate what you were talking about then you should have picked a better example.

Again, not what we're discussing. The example was used to explain the idea of expansion and compression of space-time.
It was a bad example. You are the one that brought up black holes and watching how it slows down as it approaches the event horizon. your reason for this phenomenon was wrong. You said my correction was wrong. I am just defending my correction.
Title: Re: tachyons
Post by: cmdshft on February 26, 2009, 08:31:48 PM
You're wrong because I am not talking about light, I am talking about space-time. The black hole metaphor was an example, you went off on the wrong tangent with it. So again, please educate yourself.
I explained why an object appears to slow down as it approaches the event horizon. It will still go through the event horizon but to the out side observer they never reach the event horizon. If that doesn't demonstrate what you were talking about then you should have picked a better example.

Again, not what we're discussing. The example was used to explain the idea of expansion and compression of space-time.
It was a bad example. You are the one that brought up black holes and watching how it slows down as it approaches the event horizon. your reason for this phenomenon was wrong. You said my correction was wrong. I am just defending my correction.

It was not a bad example at all, you're trying to break it down in a way that isn't applicable to the overall topic of how a tachyon manipulates space-time to achieve FTL speeds.
Title: Re: tachyons
Post by: MotherNature on February 27, 2009, 05:52:57 AM
Did you read it instead of putting And?
How does your link contradict to anything I said?

Also I'm not a professor. I don't teach in America. I teach in the UK.
I feel sorry for your students.

If a particle is moving it cannot be massless.

I see that as a contradiction to your argument.
Title: Re: tachyons
Post by: Jack on February 27, 2009, 12:28:03 PM
When we say mass, we mean invariant mass, not relativistic mass. Please replace relativistic mass with energy. A particle can move and still remain massless, while its energy continues to increase due to its motion.
Title: Re: tachyons
Post by: MotherNature on February 27, 2009, 01:50:33 PM
When we say mass, we mean invariant mass, not relativistic mass. Please replace relativistic mass with energy. A particle can move and still remain massless, while its energy continues to increase due to its motion.

Well in that case you should be discussing the scalar field. Since the imaginary rest mass is not a physical quantity.

/sigh

edit: also if a particle has any kind of movement it HAS to have mass (relativistic). The two are linked.
Title: Re: tachyons
Post by: Jack on February 27, 2009, 04:24:17 PM
edit: also if a particle has any kind of movement it HAS energy. The two are linked.
Fixed.
Title: Re: tachyons
Post by: MotherNature on February 27, 2009, 04:37:30 PM
edit: also if a particle has any kind of movement it HAS energy. The two are linked.
Fixed.

Really?


No seriously.




Really?
Title: Re: tachyons
Post by: Jack on February 27, 2009, 05:14:36 PM
Yeah.
Title: Re: tachyons
Post by: MotherNature on February 27, 2009, 05:24:03 PM
Yeah.

come on you can do better than that.

I am genuinly perplexed.
Title: Re: tachyons
Post by: optimisticcynic on February 27, 2009, 07:13:44 PM
You're wrong because I am not talking about light, I am talking about space-time. The black hole metaphor was an example, you went off on the wrong tangent with it. So again, please educate yourself.
I explained why an object appears to slow down as it approaches the event horizon. It will still go through the event horizon but to the out side observer they never reach the event horizon. If that doesn't demonstrate what you were talking about then you should have picked a better example.

Again, not what we're discussing. The example was used to explain the idea of expansion and compression of space-time.
It was a bad example. You are the one that brought up black holes and watching how it slows down as it approaches the event horizon. your reason for this phenomenon was wrong. You said my correction was wrong. I am just defending my correction.

It was not a bad example at all, you're trying to break it down in a way that isn't applicable to the overall topic of how a tachyon manipulates space-time to achieve FTL speeds.
Yes I know that time slows down when you are in gravity but that is not why objects come to a near stand still near the event horizon of a black hole. They don't stop next to the event horizon it just appears they do.
Title: Re: tachyons
Post by: cmdshft on February 27, 2009, 08:54:12 PM
You're wrong because I am not talking about light, I am talking about space-time. The black hole metaphor was an example, you went off on the wrong tangent with it. So again, please educate yourself.
I explained why an object appears to slow down as it approaches the event horizon. It will still go through the event horizon but to the out side observer they never reach the event horizon. If that doesn't demonstrate what you were talking about then you should have picked a better example.

Again, not what we're discussing. The example was used to explain the idea of expansion and compression of space-time.
It was a bad example. You are the one that brought up black holes and watching how it slows down as it approaches the event horizon. your reason for this phenomenon was wrong. You said my correction was wrong. I am just defending my correction.

It was not a bad example at all, you're trying to break it down in a way that isn't applicable to the overall topic of how a tachyon manipulates space-time to achieve FTL speeds.
Yes I know that time slows down when you are in gravity but that is not why objects come to a near stand still near the event horizon of a black hole. They don't stop next to the event horizon it just appears they do.

No, that's all relative.
Title: Re: tachyons
Post by: optimisticcynic on February 27, 2009, 08:57:33 PM
Not in this case.
Read this source http://math.ucr.edu/home/baez/physics/Relativity/BlackHoles/fall_in.html
Title: Re: tachyons
Post by: cmdshft on February 27, 2009, 09:26:19 PM
Are you dense?

Dude, EVERYTHING in this universe is done in inertial frames of reference.
Title: Re: tachyons
Post by: optimisticcynic on February 28, 2009, 02:17:45 PM
But it has nothing to do with the cause of this phenomenon. Read the bloody article. I can find more sources if you need me to
Title: Re: tachyons
Post by: cmdshft on February 28, 2009, 06:24:56 PM
But it has nothing to do with the cause of this phenomenon. Read the bloody article. I can find more sources if you need me to

How do you know it doesn't? A tachyon is like the higgs boson, we don't even know if it really exists right now, it's all hypothetical. I provided a very likely method on why it is able to travel at FTL speeds and be negative mass.
Title: Re: tachyons
Post by: optimisticcynic on February 28, 2009, 08:21:14 PM
But it has nothing to do with the cause of this phenomenon. Read the bloody article. I can find more sources if you need me to

How do you know it doesn't? A tachyon is like the higgs boson, we don't even know if it really exists right now, it's all hypothetical. I provided a very likely method on why it is able to travel at FTL speeds and be negative mass.
I was talking about how stuff appears to slows down as it approaches the event horizon.

If I understand what your saying is that if you went near a tachyon you would travel faster through time unlike when you are near a gravity well where time slows down for you.
Title: Re: tachyons
Post by: cmdshft on February 28, 2009, 08:40:08 PM
But it has nothing to do with the cause of this phenomenon. Read the bloody article. I can find more sources if you need me to

How do you know it doesn't? A tachyon is like the higgs boson, we don't even know if it really exists right now, it's all hypothetical. I provided a very likely method on why it is able to travel at FTL speeds and be negative mass.
I was talking about how stuff appears to slows down as it approaches the event horizon.

If I understand what your saying is that if you went near a tachyon you would travel faster through time unlike when you are near a gravity well where time slows down for you.

Close. I was more referring strictly to the mechanics of how just the tachyon might move through space-time at FTL speeds.
Title: Re: tachyons
Post by: optimisticcynic on February 28, 2009, 10:31:41 PM
Yeah that slow down of time is not why stuff appears to slow down to almost a dead stop when it comes close to an event horizon.
Title: Re: tachyons
Post by: REman on March 14, 2009, 10:12:12 AM
Just because it was in star trek does not mean that it is an idiotic theory. >:(

Is it a theory? Or just something someone made up?
Title: Re: tachyons
Post by: iznih on March 14, 2009, 10:23:53 AM
it is mathematically possible
Title: Re: tachyons
Post by: bowler on March 14, 2009, 04:47:30 PM
Hmmm. There are Tachyonic fields in quantum field theory. Occasionally they are mentioned in special relativity as a particle constrained to the region v>c on a plot of gamma against v. Although in practise there are obviously problems in such a particle existing, for example it cannot carry information or causality would be violated. Such a particle would have an imaginary mass also. I believe they come up in string theory but I've only ever really seen them in relation to spontaneous symmetry breaking. Here they exist only at unstable points and no real (importantly observable) particle can be associated to the field. Its pretty hard stuff I've never totally got to grips with it.