Physics question

[Soundproof]

Absolutely.

He-he!

[The new erato]

For what I know, the mass doesn't increase with speed at all. It is the Energy which increases,

But as we all know; E = Mc² so that statement is superfluous.

[head-case]

Soundproof, thanks for all your contributions here. My knowledge of more "advanced" physics is based primarily on popular science books, so it's nice to have someone clear up all those misunderstandings.

The notion that the incoherent musings Soundproof has put up on this thread could have cleared up any misunderstanding is quite astonishing, indeed.   

[Scriptavolant]

But as we all know; E = Mc² so that statement is superfluous.

Not really superfluos. The Mass is unvaried for what concerns the observer. The equation above is okay for rest condition, not for moving objects. If an object approaches the speed of light, we're talking about its energy.

[The new erato]

The Mass is unvaried for what concerns the observer.

Not sure what you're trying to say here, it all depends on the relative speeds between the object and the observer. If the observer is moving along with the speeding object, ie their relative speeds are 0, that is obviously right, ie no increase in mass is observed.

[71 dB]

But as we all know; E = Mc² so that statement is superfluous.

Only for objects not moving for observer. Otherwise:

[The new erato]

Ah, the good old Lorenz transform!

And PS 71 dB; that's what I am saying in my previous post.

[Sergeant Rock]

The mass increases with speed, and at the speed of light the mass becomes infinite...

If that's true, why didn't Captain Kirk and his crew get really fat when they went into warp drive?

Sarge

[orbital]

If that's true, why didn't Captain Kirk and his crew get really fat when they went into warp drive?

Sarge

But that's the point! The observers got fat with them, so everybody thought they were just normal   

[The new erato]

But that's the point! The observers got fat with them, so everybody thought they were just normal   

distance elongates proportionally to mass....so they would still have the same waist width

[Mozart]

So assuming mass does increase, if a large enough object travels fast enough, would it turn into a black hole? And would the black hole continue to move through space at the same speed?

[head-case]

So assuming mass does increase, if a large enough object travels fast enough, would it turn into a black hole? And would the black hole continue to move through space at the same speed?

Of course not.  A central premise of special relativity is that the laws of physics are the same in all inertial reference frames.  If a mass is not a  black hole in one reference frame, it is not a black hole in any reference frame.   The same premise indicates that the gravitation attraction for a moving body is the same as for a body at rest, since there is a frame of reference in which the moving body is at rest and visa versa.  (This argument, of course, applies to the gravitational force between two bodies that are moving at the same velocity.) 

[The new erato]

So assuming mass does increase, if a large enough object travels fast enough, would it turn into a black hole? And would the black hole continue to move through space at the same speed?

If a black hole with "infinite" mass moves at the speed of light relative to you there is no way its gravitational waves (or any other information) would reach you, so you would have no way of knowing it was there, and its effect would not be noticeable on you.....for all purposes it would be non-existent.

[71 dB]

And PS 71 dB; that's what I am saying in my previous post.

True, I got confused about who says what. This discussion has been disordered!

If a black hole with "infinite" mass moves at the speed of light relative to you there is no way its gravitational waves (or any other information) would reach you, so you would have no way of knowing it was there, and its effect would not be noticeable on you.....for all purposes it would be non-existent.

Not true. Black holes do radiate.

[The new erato]

True, I got confused about who says what. This discussion has been disordered!

Not true. Black holes do radiate.

Yes, they certainly do. And you can observe it because they DO NOT move at the speed of light relative to you. My point was not that they don't radiate, simply that (in answer to a previous post) if they did move at the speed of light relative to you, you would have no way of knowing. The same effect would be acheived if the blach hole was big enought that its radiation couldn't escape its gravitational field (remember, speed and mass are related)- so you only can observe black holes if they are small enough and stationary enough....

[head-case]

Yes, they certainly do. And you can observe it because they DO NOT move at the speed of light relative to you. My point was not that they don't radiate, simply that (in answer to a previous post) if they did move at the speed of light relative to you, you would have no way of knowing. The same effect would be acheived if the blach hole was big enought that its radiation couldn't escape its gravitational field (remember, speed and mass are related)- so you only can observe black holes if they are small enough and stationary enough....

You comments make no sense at all.  Every black hole radiates. Radiation occurs at the event horizon because when an electron-hole pair is created (which would ordinarily annihilate itself) half of the pair falls into the black hole and the other half of the pair escapes.  Every black hole, no matter how big, has an event horizon and will create such radiation.  Black holes can't move at the speed of light, so discussion of what would happen in this case is irrelevant.  If they moved near the speed of light the radiation and gravitational fields they generate would be observable just like any other source.

[The new erato]

Black holes can't move at the speed of light, so discussion of what would happen in this case is irrelevant. 

Exactly my point from a previous post...(re infinite mass, and 71db's formula with v = c)

If they moved near the speed of light the radiation and gravitational fields they generate would be observable just like any other source.

My comment was aimed at what would happen if they actually were able to move at the speed of light, which I'm perfectly aware that they can't - again see previous post.

My commenta were aimed at some previous postings ..... and was not a description of what I consider physically possible, so any opinions on lack of sense should be directed to the original posters. 



i

[Sean]

Hi Mozart, et al

I was really into relativity when I was about 20 and even gave a talk on it at my local astronomical society and later at university, always avoiding most of the maths.

I remember reading that as a large object approaches c it can create a black hole behind it; however whether this applies to the particles in an accelerator I don't know, and indeed layman's guides can be less than accurate sometimes.

One of many books I found on the subject listed problems that a student was supposed to tackle: I never quite worked this one out-

A space ship at 86.7% c (for instance) has a gamma/ Lorenz factor of 2, making it half its usual length. Hence it can pass a marker in less time, relative to a stationary observer, than it would if its length wasn't contracted. However, relative to the ship it is the observer's reference frame that is contracted, and it would take longer to pass the marker...

I don't know how this is supposed to work, or also how both clocks can be running slow, as they will appear to do so from both observer to ship and ship to observer: I read somewhere that it's the ship's initial acceleration that makes the two situations unequal and its observations can be seen as a relativistic illusion if it returns to the observer's reference frame.

But my impression is that it all becomes a right tangled mess.

[head-case]

Hi Mozart, et al

I was really into relativity when I was about 20 and even gave a talk on it at my local astronomical society and later at university, always avoiding most of the maths.

I remember reading that as a large object approaches c it can create a black hole behind it; however whether this applies to the particles in an accelerator I don't know, and indeed layman's guides can be less than accurate sometimes.

One of many books I found on the subject listed problems that a student was supposed to tackle: I never quite worked this one out-

A space ship at 86.7% c (for instance) has a gamma/ Lorenz factor of 2, making it half its usual length. Hence it can pass a marker in less time, relative to a stationary observer, than it would if its length wasn't contracted. However, relative to the ship it is the observer's reference frame that is contracted, and it would take longer to pass the marker...

I don't know how this is supposed to work, or also how both clocks can be running slow, as they will appear to do so from both observer to ship and ship to observer: I read somewhere that it's the ship's initial acceleration that makes the two situations unequal and its observations can be seen as a relativistic illusion if it returns to the observer's reference frame.

But my impression is that it all becomes a right tangled mess.

The resolution to this paradox is the notion that time is not an absolute quantity in relativity, as it is in classical mechanics.  To say that the ship is 1 meter long the front of the ship has to be next to one side of the meter stick and the back of the ship needs to be next to the other end of the meter stick simultaneously.  So to do the measurement properly you need to put synchronized clocks on both ends of the meter stick and register the alignment with the front and back of the moving ship at the same instant.  However, according to relativity events which are simultaneous in one reference frame will not appear simultaneous in another reference frame.  To an observer on the ship the two clocks will appear to be out of sync.  From the ship's point of view the clock registering the position of the nose of the ship will click before the clock registering the position of the tail of the ship, which makes his ship appear shorter.  However, if the person in the ship attaches synchonized clocks to the nose and tail of his ship, the observer on the ground will see the ships clocks as being out of sync.

[The new erato]

Veryu well put. And it all hinges on the fact that the speed of light, which defines the limits to simultanety for us, is finite.

Just as it isn't possible to diffenrentiate beetween gravitation and acceleration.

Together these observations spawns the two teories of relativity.