Absolute vs. Relative motion

[pgrmdave]

If mass increases with velocity, doesn't that mean that velocity has to be absolute? Is there a way to measure an objects velocity by comparing it's current mass to it's expected resting mass?

[Buffy]

Nope. The only velocity that is absolute is the speed of light, and the only thing that can travel of the speed of light is light, because at the speed of light, mass becomes infinite according to our friend Albert....all other velocities are relative to the observer...

Cheers,
Buffy

[Thelonious]

Originally Posted by Buffy

all other velocities are relative to the observer...

Right. Different observers in different reference frames will observe different velocities, masses, etc...

[zadojla]

Dave, this is covered in special relativity. I think I still have my college physics texts, that explain what an inertial frame of reference is. There is no absolute frame of reference.

[maddog]

Originally Posted by zadojla

Dave, this is covered in special relativity. I think I still have my college physics texts, that explain what an inertial frame of reference is. There is no absolute frame of reference.

The Absolute frame of Reference was basically invented with Newton and went out with
Einstein. The absolute reference was because time itself was thought by Newton as
being absolute (independent of observer). With SR of Einstein was found to not be.
End of story.

I will say that the speed of light will slow down for the medium it is passing in glass, etc.
In a vacumn the speed is c exact (and is NEVER faster) for any frame of reference. This
is so far all consistent and has been verified to high accuracy. You start to get strange
speculation when one tries to discern what happened very early in the age of the universe.

Maddog

[hefner]

Originally Posted by pgrmdave

If mass increases with velocity, doesn't that mean that velocity has to be absolute?

That's a misunderstanding that arises every day due to the poor way that much popular gossip explains why lightspeed is the cosmic speed limit. It is widely touted that a spacecraft cannot accelerate to lightspeed because it gets heavier and heavier at speeds approaching c. There is a kernel of truth to relativistic mass increase, but like everything else under Relativity, it depends entirely on the observer's vantage. Therefore, relativistic mass increase can NOT make for a satisfactory explanation of why a rocket propelled craft is unable to achieve lightspeed, since the thrust originates in the rocket's very own rest frame. High relative speed is NO barrier to rocket propulsion whatsoever. The real reason that a spacecraft cannot achieve lightspeed is due to the unusual way that velocities add.

On the other hand, it is pertinent to ascribe relativistic mass increase as the impediment preventing a charged particle in a particle accelerator from reaching the taboo speed. Why?? because those particles are being pushed along by electromagnetic field-producing coils positioned in the (relatively) stationary lab frame. From the viewpoint of that frame, the mass increase to the speeding particle becomes perfectly germane.

I hope this is all understood.

[BlameTheEx]

There is a sort of "Absolute frame of reference" inherent in the Hubble constant. Perhaps it already has an official name, but until somebody informs me of it I will call it "Local Absolute Zero Velocity."

The implication is that there is a zero velocity for any specific point in space. This is the reference frame such that the red shift of stellar objects are (once averaged out) even on all sides.

The popular belief is that this red shift is fixed to space itself rather than the matter in it. This must be true if the red shift is purely the product of our universe expanding. If so this Local Absolute Zero Velocity can be considered a fundamental property of space.

If space is expanding evenly as most believe then each part of space itself must have a different velocity. Each bit of space can be DEFINED by it's velocity. Of course this may be time dependent too. Current thinking is that the universe is not holding to a fixed rate of expansion.

Local Absolute Zero Velocity might be difficult to determine with absolute accuracy because galaxies and such will have velocity components due to other factors than the hubble constant, but it does seem that we can get very close indeed.

Ok. Now for the big question. Apart from evening out red shift, is there any other detectable or predictable property of Local Absolute Zero Velocity?

[hefner]

Originally Posted by BlameTheEx

Apart from evening out red shift, is there any other detectable or predictable property of Local Absolute Zero Velocity?

Yes, there'll be a location (NOT so of Earth's whereabouts) where the Cosmic Background Radiation (CBR) is uniform (of equal frequency) in all directions.

But I don't believe in that being at all pertinent to physics. I am a Special Relativity PURIST ie. there's no such thing as 'space'... space isn't a THING; space is the absence of any thing!!

[BlameTheEx]

hefer.

I did consider mentioning CBR. If the assumptions behind it are correct it is an even more accurate way of measuring Local Absolute Zero velocity. I just didn't want to get bogged down with more assumptions. Sadly I don't think CBR makes the case much stronger. It is too closely linked to the Big Bang - the same apparent source of the redshift.

Space exists because it has properties. Unless we are very much mistaken the BB was not a simple explosion of matter in space. If so space ether has the property of velocity, or at the least the property of apparent velocity.

Purely empty space might not have measurable properties, because it is free of measuring devices. Once there is something in space to be measured, the properties of space can be deduced by its effects. In this case the something is distant galaxies, and the property is redshift which is being interpreted as motion.

While I insist that space has this property you may be in practical terms correct. It may be that the (apparent?) velocity of space has no effect whatsoever on the laws of physics and Special Relativity is absolutely accurate as a method of defining what happens. Then again, perhaps it won't work out that way.

I would like you to at least consider the possibility that Special Relativity might not be the final and ultimate definition of reality. By defining yourself as a purist in this way you are turning a theory into a religion.

[hefner]

Originally Posted by BlameTheEx

hefer.
... I would like you to at least consider the possibility that Special Relativity might not be the final and ultimate definition of reality. By defining yourself as a purist in this way you are turning a theory into a religion.

Um, I also believe in General Relativity, but understand it a bit less well. Although I think that even under GR, space is the absence of any thing. Yes, space is curved by gravity, but that again relates to material objects and their influence. Absent of material objects, one is still left with space equalling nothingness. And I think "space curvature" is primarily palatable phrasing -- the real truth is wound up in the nitty gritty math. I fail to see how that GR wording eliminates "action at a distant". I mean, if space is warped 100 miles from the gravity source, isn't that also "action at a distance"?? Yes, the Einsteinian gravity tensor is mathematically a bit different than the rudimentary Newtonian gravitational field, but what's the big difference?? Wordplay is wordplay, but the math is truly telling. (That's an invitation for comment.)

As for equating my scientific allegiances to a RELIGION... BAH! NEVER! I'd change my mind in a nanosecond if the evidence were compelling. I just happen to like SR and understand it well. I'm even willing to backpedal about being some kind of 'purist'... okay??