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.RC.
02-23-2008, 10:21 PM
I was thinking today about the speed of light and how it is supposed to be unbreakable for anything with mass..

However I came up with this scenerio and wonder if it is possible...

I have managed to invent a gun that can fire projectiles at 250 000km/s..I have also invented a train that travels at 150 000km/s...

Now whilst the train is travelling at top speed I fire the gun in the direction the train is travelling....Now relative to me on the train the projectile is now travelling at 250 000km/s BUT relative to an observer who is watching the train go past he sees the projectile travelling at 350 000km/s and in fact is going faster than the speed of light..

Does that sound correct???

Lew Hartswick
02-23-2008, 10:28 PM
In a word NO!
...lew...

Evan
02-23-2008, 10:31 PM
No. The speed of light is the same for all observers in all frames of reference because of time dilation.

andy_b
02-23-2008, 11:33 PM
BUT relative to an observer who is watching the train go past he sees the projectile travelling at 350 000km/s and in fact is going faster than the speed of light..

Does that sound correct???

he won't see it moving faster than the speed of light because the light only moves at the speed of light. it doesn't matter if the object could go past him at 1 billion km/s.

andy b.

Fasttrack
02-23-2008, 11:53 PM
No. The speed of light is the same for all observers in all frames of reference because of time dilation.



And length contraction...

Ringer, pick up a copy of Einstein's "relativity". You should be able to find a translated copy for cheap at most book stores. I found a copy for 3 bucks a few years ago. Well worth a couple of bucks since it's not a text book. (i.e. its a great place to start learning about relativity because its written for the layman)


p.s. So to an observer on the ground, the length of the train (and therefore the path of the bullet) appears shorter. At the same time, the amount of time that the observer on the train measures is going to be slower than the time measured by the observer on the ground. This means that if, in one second (by the clock that the observer on the train uses) the bullet moves 250,000 km, it will take about 1.2 seconds for the bullet to travel that far according to the observer on the ground. (That was assuming the train was moving at 150,000 km). Thus the velocity measured by the observer on the ground is actually about 208,000 km/s - disregarding the observed contraction in length. When the contraction is figured in, the velocity drops to 216,506 km ... which works out to a velocity of 180,000 km/s. Now - you say well 180,000 km/s plus 150,000 km/s is still greater than the speed of light. But we only consider the time and length changes due to the speed of the train, not the speed of the bullet. Since the bullet is moving faster than the train, you can see that the effect will be even more pronounced.

If you actually plot the effects of velocity on time it draws to infinity while the length goes to zero. And, of course, 0/(infinity) is pretty slow ;)

p.p.s

t = t' / [sq rt (1-v^2/c^2)] and x = x' [sq rt (1-v^2/c^2)]

Rif
02-24-2008, 12:08 AM
Evan is partially correct. But time dialatation does not pertain to the energy required to change the speed that the object is travelling. Only to the amount of time that passes on the object relative to the passage of time on another object. However, the time dialation equations are very similar to the energy equations to determine the answer to relativistic questions.

The real problem is the amount of energy required to increase the speed. To accelerate an object, with mass, to the speed of light requires an infinite amount of energy. If you were to graph the amount of energy required, for an object's acceleration, it would look like a hyperbola. Once you reach about 70 to 90 percent (I am going from memory here.), the speed of light, the amount of energy required to accelerate faster becomes an exponential number....eventually ending at infinity. So, the reality is that if you were travelling at 196,100 miles per second and fired an object that normally travels at 500 miles per second (when you are not moving) it would only be travelling at slightly over 196,100 miles per second.

Bear in mind, there is no known location in the universe where nothing is moving. Relative to the Earth's rotation, I am travelling at about 1000 mph just sitting here typing this reply. Then you have to factor in the speed the Earth moves around the sun, the speed the sun moves around the galaxy, the speed the galaxy is moving. But, the speed the galaxy is moving could only (theoretically) be determined by having an object that is completely static otherwise it's speed is relative to that of another object. So, the speed of the galaxy relative to a static location is completely unknown.

In theory, to travel at or beyond the speed of light requires either creating a mini-universe where your ship is stationary and moving that universe within our universe. (Avagadros (not spelled correctly) warp drive.) Another possibility is to create a "worm hole" between your source and destination point and use that for travel. The third possibility is to "pull" the "fabric" of the universe towards your ship and ride it's wave as you release it. Imagine sitting on a gigatic rubber band, reaching out a mile away, pulling that part next to you, moving foward onto the pulled part, then allowing it to snap back into it's normal position. These are the theories that I can think of off the top of my head. I am sure that there are more. Oh, yeah, the warp drive theory is not only a Star Trek fabrication...it is a real theory.

Regards,

Brian

Fasttrack
02-24-2008, 12:24 AM
Oh Brian brings up an interesting point:

According to Einstein, the idea of increasing mass with increasing velocity should be disregarded because it posses some difficulties in determining "what" mass is and what to reference off of. Distance and time can be referenced off of light.

The energy argument, however, is used often in two places:
1) popular science (nova, science channel, etc)
2) high energy physics (i.e. particle physics) since it does require more energy to increase velocity. For instance, the particle acelerator at Fermi lab is in the TeV range. At 1 TeV a large hadron - i.e. proton - should be able to obtain a velocity of 13841114 km/s!! Of course, the proton only achieves a velocity of .99999 the speed of light.



(incidently, the time dialation and length contraction is the correct answer to the problem of the bullet being shot on a really fast vehicle. The energy argument is an implicit solution - its actually derived from the change in observed velocity at high "actual" velocity. From that, a change in mass can be determined, but it all starts with the lorentz transforms.)

A.K. Boomer
02-24-2008, 12:35 AM
is this the same arguement as taking a spaceship close to the speed of light and then shining flashlight off the front end of it? (it dont work)


Rif, i tripped over your reply and read as much as i should in my current cond.

I like what i read and will check it out in the monyadda...

Rif
02-24-2008, 01:10 AM
Oh Brian brings up an interesting point:

According to Einstein, the idea of increasing mass with increasing velocity should be disregarded because it posses some difficulties in determining "what" mass is and what to reference off of. Distance and time can be referenced off of light.

The energy argument, however, is used often in two places:
1) popular science (nova, science channel, etc)
2) high energy physics (i.e. particle physics) since it does require more energy to increase velocity. For instance, the particle acelerator at Fermi lab is in the TeV range. At 1 TeV a large hadron - i.e. proton - should be able to obtain a velocity of 13841114 km/s!! Of course, the proton only achieves a velocity of .99999 the speed of light.



(incidently, the time dialation and length contraction is the correct answer to the problem of the bullet being shot on a really fast vehicle. The energy argument is an implicit solution - its actually derived from the change in observed velocity at high "actual" velocity. From that, a change in mass can be determined, but it all starts with the lorentz transforms.)

You also brought up another interesting point about the "length contraction." As the velocity, of an object, increases it's length, in the direction of travel, becomes shorter. A person, travelling at close to the speed of light, would look like a pancake if they were able to be observed by someone who is relatively stationary.

The increase in mass is the true reason for the increase in energy required for acceleration to higher speeds. As an object increases in speed, it's mass increases.

I don't understand your claim that time dilation is the correct answer. Time dilation only pertains to the passage of time on a moving object relative to that of a stationary object. Time dilation is the reason why some high speed elementary particles can be detected from the Earth. Some particles only have a life span of thousanths or even millionths of a second. Yet, they travel for long distances (i.e. Thousands of miles above the surface of the Earth to the surface of the Earth.) and survive for a longer period of time (as observed by us). This is due to time dilation. For the elemetary particle it is only surviving for it's normal time period....relative to itself. But, relative to us, it is surviving a lot longer. Time dilation has also been proven by atomic clocks...one stationary and one in motion.

Regards,

Brian

Rif
02-24-2008, 01:18 AM
is this the same arguement as taking a spaceship close to the speed of light and then shining flashlight off the front end of it? (it dont work)


Rif, i tripped over your reply and read as much as i should in my current cond.

I like what i read and will check it out in the monyadda...


The example you mention happens only because light only travels at the speed of light. Light can never travel faster or slower that the speed of light. So, a beam of light shining off of the front of a fast moving spaceship will still only travel at the speed of light relative to a stationary observer.

There have been claims, however, of the speed of light being manipulated in the laboratory. Given the descriptions of how they have accomplished this, it sometimes makes me wonder if it is really the speed of light being manipulated or how the medium the light is travelling through reacts to the experiment.

There is a possibility, however, that the speed of light may change depending upon the proximity to a gravitational field.

Regards,

Brian

dp
02-24-2008, 01:44 AM
If that were possible then it would be possible to hear the shot before it was made. Time doesn't work like that.

pntrbl
02-24-2008, 03:04 AM
I've never forgot a Disney cartoon from when I was a kid that had Goofy standing there with a stopwatch as a beam of light bounced around the room on mirrors. Yep! 186,000 miles per second! But I wondered ever since who in the hell clocked it anyway?

Fast forward to the kids coming home from school one day talking about the speed of light and I decided it was time to do some digging and find out. Turns out an astronomer named Herod had it figured out 500 years ago when most of earth's population still thought it was flat.

What he was doing was watching a moon disappear behind Mars. At one point in the year it took 12 hours longer for the moon to re-appear than at the other. The difference of course is the amount of time it takes light to cross the dia of the earths orbit.

Still amazes me.

SP

Oldguy
02-24-2008, 03:27 AM
But would you use old iron or a new Asian import to build the train and gun?

Glenn

(Just trying to tie all of todays threads together.):)

Evan
02-24-2008, 04:52 AM
You also brought up another interesting point about the "length contraction." As the velocity, of an object, increases it's length, in the direction of travel, becomes shorter. A person, travelling at close to the speed of light, would look like a pancake if they were able to be observed by someone who is relatively stationary.
The Fitzgerald Contraction is not observable by any observer in any frame of reference. There are a number of misconceptions that have been spread even by the popular science press and teachers who really don't know any better. For instance, it is frequently said that the speed of light is constant. No, only the speed of light in a vacuum is constant. Light slows down when interacting with matter. The denser the matter the slower it goes.

Light does interact with gravity. Gravitational lensing of distant quasars and galaxies are proof of that. However, if it slows down is not measurable because gravity also affects any observer and his equipment who tries to measure it. Time slows down in a gravity well but again it cannot be observed. There seems to be some sort of shielding effect built into the rules that prevents paradoxes from occuring or being observed. They may exist but if they do they can never be seen.

John Stevenson
02-24-2008, 05:18 AM
It has already been done.
In the 1960's Lucas came out with their first alternator to be fitted to a motorcycle.
Amongst the first to use this was the BSA [ Bits stuck anywhere ] C11G and I was fortunate enough or unfortunate enough to own one of these fine ? machines.

The total output of these first alternators was 45 watts or wot's??
30 watts were used by the headlight, 5 watts were used by the tail light, 10 watts were used by the stop light and 8 watts by the ignition coil, the rest that was left over was used to charge the battery by the latest in electronic technology of the day, the selinium rectifier.

So 30 + 5 + 10 + 8 = 53 watts required by the system before charging the battery.

Now granted you don't go riding about all day with the rear brake on, not that it would have made much difference so deducting 10 watts for the stop light we now have a total night load of 43 watts less losses to charge the battery.

The result of this amazing amount of homework by the engineers at the Joseph Lucas, Prince of Darkness chapter was that at night even given the speed of light is 186,000 miles per second it was perfectly possible to run over your main beam.

It cannot be proved but I think this phenomenon was discovered a lot earlier by J M Barrie who used this information to write about Peter loosing his shadow in Peter Pan.

.

radish1us
02-24-2008, 05:52 AM
It has already been done.
In the 1960's Lucas came out with their first alternator to be fitted to a motorcycle.
Amongst the first to use this was the BSA [ Bits stuck anywhere ] C11G and I was fortunate enough or unfortunate enough to own one of these fine ? machines.


.


AAaahh John, think you forgot that magical letter in front of the C11G, the biggest piece of sorry garbage that I ever owned was the BSA 'Z' C11G, 250cc's of nuthin'.
Glad when the cap came of the bowl of the carby, fuel everywhere and it backfired, snot shot out the throat of the carby followed by that horrible whooshing noise, good B.B.Q by the roadside was had by a few friends, whilst I had to go change me nappy.
Marvelous memories you manage to bring up, thought I'd buried 'em decades ago.

John Stevenson
02-24-2008, 06:04 AM
AAaahh John, think you forgot that magical letter in front of the C11G, the biggest piece of sorry garbage that I ever owned was the BSA 'Z' C11G, 250cc's of nuthin'.


Ours didn't have the 'Z' just C11G but we were poor in those days :D

Perhaps the Z was the export model? Fascinating really when you look at the bikes that went to the far corners of the earth.
They probably did more miles on the deck of a steamer than under their own steam :rolleyes:

.

rantbot
02-24-2008, 06:23 AM
Turns out an astronomer named Herod had it figured out 500 years ago when most of earth's population still thought it was flat.

What he was doing was watching a moon disappear behind Mars. At one point in the year it took 12 hours longer for the moon to re-appear than at the other. The difference of course is the amount of time it takes light to cross the dia of the earths orbit.

Huh? You mean a moon of Mars? Both moons were discovered in the late 1800s.

The lag in the apparent orbits of the moons of Jupiter can be used to estimate the speed of light, but only if you already have a good handle on the size of the outer solar system. Historically, the scale of the solar system was determined by other methods (such as the length of the Jovian year, which fixes some of its orbital parameters), after which observation of phase shifts in the orbits of the Galilean satellites allowed an estimate of the speed of light.

lazlo
02-24-2008, 07:42 AM
Turns out an astronomer named Herod had it figured out 500 years ago when most of earth's population still thought it was flat.

What he was doing was watching a moon disappear behind Mars. At one point in the year it took 12 hours longer for the moon to re-appear than at the other. The difference of course is the amount of time it takes light to cross the dia of the earths orbit.

Wow, you got a lot of facts confused there! :) Herod was the King of Judea, mentioned in Gospel According to Matthew.

The first accurate measurement of light-speed came was by a Danish astronomer named Olaf Roemer in 1676. Like Ranbot implies, Roemer measured elapsed time between eclipses of Jupiter with its moons.

HSS
02-24-2008, 07:48 AM
Being the noob that I am, I think I made a big mistake getting into machining. You guys are talkin' way, way, way over my head. I don't think I'll ever make it.:confused:

A.K. Boomer
02-24-2008, 10:24 AM
It never fails --- anytime something of light or electricity is brought up S.J. and his cronies start beatin on lucas --- ungreatful - unapreciable people who forget the vast contributions of the inner genius ----- where the hell would we be?
Every time my coffee maker shuts off automatically im acutely aware of who laid down the ground work.
The simple blinker relay is nothing more than a glorified lucas electrical connection.
Last but not least --- the intermittent wiper, this contribution to mankind is actually engraved on the mans tombstone, shame on you people, shame on you all...

pntrbl
02-24-2008, 10:42 AM
Wow, you got a lot of facts confused there! :) Herod was the King of Judea, mentioned in Gospel According to Matthew.

The first accurate measurement of light-speed came was by a Danish astronomer named Olaf Roemer in 1676. Like Ranbot implies, Roemer measured elapsed time between eclipses of Jupiter with its moons.

Well anybody that believes everything I say is fool for sure! LOL! That obviously incorrect factoid was from memory when Kriston was in the 6th grade. She's 26 now and I'll plead advancing age ...

It still amazes me that someone used moons around a planet hundreds of years ago to figure this out tho. We stand on the shoulders of those that came before us.

SP

Lew Hartswick
02-24-2008, 11:00 AM
Johns treatise on Lucas is another "classic" in the style of his one
WAY back on "Christmas" and the wise men.
(Still havent seen one on Easter that was promised) :-)
...lew...

Evan
02-24-2008, 11:11 AM
I don't find it all that hard to beileve. The speed of light is a snail's pace when compared to the scale of the universe or even just our solar system. Heck, it's even a serious limiting factor for me on a purely "local" scale because of the latency it produces in my internet connection. Light travels about 1 foot per nanosecond which makes it easy to demonstrate on a good oscilloscope. All you need is a 50 foot roll of coax cable and a dual trace triggered sweep scope with decent RF response. Send a pulse in one end of the cable as well as triggering the scope direct and you can measure the speed of light in a cable, about 50% of the velocity in a vacuum.

The thing that is hard for most people to understand is that the conditions which would seem to cause a variance in the observed velocity of light in a vacuum are also always the same conditions that make it impossible to observe. The universe has built in mechanisms that assure consistency is maintained. This is logically necessary if the universe is to have rules, which it most certainly seems to have. If any situation existed that would expose directly a physical paradox then it would be an exception to the rules. If you have just one exception then the rules are invalidated completely.

The consequence of having an exception to the velocity of light "rules" would be to allow exceptions to any of the rules. That in turn would mean that the universe has no rules and cannot be described via logic. An example is a black hole as predicted by Einstein. It seems that it is always and must always be cloaked by the gravitationally produced Swartzchild Radius, or Event Horizon. The interior of a black hole is currently "undefined" and is likely to remain so. The only reasonable conjecture we have about the interior of a black hole is that it exists as a singularity. In the singularity all the rules break down as the values on which they are based trend asymptotically to infinity. The infinities are unresolvable so the protection of the event horizon prevents such a paradox from exisiting in our space time. Were a naked singularity to exist then we would be obliged to throw out the "rule book" and start believing in FM instead (freekin magic).

Fasttrack
02-24-2008, 02:50 PM
Oh my ... a discussion about relativity on a home shop machinist forum ... :)


1) Length contraction is real. If you consider only time dilation, you will find that it is still possible to exceed the speed of light. An easy calculation to do. I refer people to Hughston and Jansen (spelling?) on the theory of lorentz contraction. The lorentz-fitzgerald interpertation of contraction was fairly well disproved in like the 1920's by Trouton and Rankine.

2) The argument for increased mass, as i said before, can be derived from time dilation and length contraction. The concept that mass increases, while not strictly incorrect, is not a favorable interperation as you get into relativistic quantum mechanics. In fact, it makes several trivial problems almost impossible to solve. Trust me - i've made the mistake of trying to solve said problems when assuming an increase in mass. The problem turns into an algebraic nightmare. If you fail to solve a quantum mechanical problem because you screw up the algebra, then you have done something wrong - big time. Usually you get stuck because of related partial differential equations.


<edit> Just so you know i'm not making this up, i just found this on the first site that popped up after searching "mass increase with velocity" in google:

"Of the two, the definition of invariant mass is much preferred over the definition of relativistic mass. These days, when physicists talk about mass in their research, they always mean invariant mass. The symbol m for invariant mass is used without the subscript 0. Although the idea of relativistic mass is not wrong, it often leads to confusion, and is less useful in advanced applications such as quantum field theory and general relativity. Using the word "mass" unqualified to mean relativistic mass is wrong because the word on its own will usually be taken to mean invariant mass. For example, when physicists quote a value for "the mass of the electron" they mean its invariant mass."

Arguments against the term "relativistic mass" are given in the classic relativity text book Space-Time Physics by Taylor and Wheeler, 2nd edition, Freeman Press (1992).

Einstein's original papers can be found in English translation in The Principle of Relativity by Einstein and others, Dover Press.

Some other historical details can be found in Concepts of mass by Max Jammer and Einstein's Revolution by Elie Zahar

John Stevenson
02-24-2008, 02:52 PM
We stand on the shoulders of those that came before us.
SP

Is that why we can see further ?

It might account for the fact Sir Joseph Lucas was only 5' 1" tall, wheras his father was 4'10"


.

Fasttrack
02-24-2008, 02:57 PM
We stand on the shoulders of those that came before us.

SP


Funny story, actually. Newton, of course, said this in a letter to hooke. It is generally taken to mean that he was being humble when discussing his discoveries. (i.e. my work is the product of all the work done before me)

In reality, it was actually a sarcastic remark against Hooke - an "enemy" of newton. :)

Evan
02-24-2008, 04:11 PM
1) Length contraction is real.

Yes it is. However, it cannot be observed. This was shown by James Terrel in 1959.

More here: http://math.ucr.edu/home/baez/physics/Relativity/SR/penrose.html

A.K. Boomer
02-24-2008, 04:14 PM
Is that why we can see further ?

It might account for the fact Sir Joseph Lucas was only 5' 1" tall, wheras his father was 4'10"


.

Its sad, anything for a laugh i suppose ehhh Sir John? Funny how even the very intermittent connections that your using on your key board to be able to type with and I might add insult the man were actually created by him trying to complete a continuous circuit, what I find even more upsetting is the perverse fashion in which you seem to actually take pleasure in "sticking it" to one of your very own country men, Now thats quite a piece of work fella.............................:p (got anymore?:) )

John Stevenson
02-24-2008, 04:19 PM
Sorry AK if I have upset you with my missplaced information and I do stand corrected, he was 4'11" not 4' 10"

.

66glide
02-24-2008, 06:12 PM
Whooooooa.....I'm gonna start smoking weed again!

Fasttrack
02-24-2008, 08:18 PM
Evan - Ahh, i mis-interpted your previous post and was anxious to point out that length contraction is real. As i said, without length contraction the speed of light can be exceeded. I just draw a distinction between "observe" and "appear". The appearence is not contracted, but the length contraction can be measured, which is a form of observation.

Penrose had some fantastic theories, though. I've recently developed quite an interest in correspondence theory. Of course, Penrose had some very interesting theories regarding when wave collapse occurs and what causes it.

aostling
02-24-2008, 08:48 PM
I'll describe something which can go faster than the speed of light.

It's the apex of the Vee formed by the blades of an open pair of scissors. When the scissors are wide open the apex is virtually at the hinge pin. When you close the scissors down the apex races outward, toward the tip. Toward the end of its travel the outward speed of the apex will be faster than the speed of the closing handle grips, faster perhaps by a factor of ten or more.

So if you can manage to close the handles at a sizable fraction of the speed of light, that apex can be much traveling much faster than the speed of light.

The apex has no mass. It's only a position, but it is an observable one. If we are cutting a piece of paper with these scissors this position is the point separating the cut and uncut portions.

john hobdeclipe
02-24-2008, 09:09 PM
If I'm riding my bicycle down the road at, say, 25 mph, that part of the tire that is at bottom dead center is not moving forward at all while it is in contact with the ground. And that part of the tire that is at top dead center is moving forward twice as fast as I am, in this case 50 mph.

So here's what I've often stayed awake at night wondering about:

If I ride my bicycle at 3/4ths the speed of light, will the top of my tire be going at 1.5 times the speed of light? Or is the ultimate speed limit for a bicycle (or any wheeled or tracked vehicle) only 1/2 the speed of light?

And what happens if I crash?

Rif
02-24-2008, 09:44 PM
If I'm riding my bicycle down the road at, say, 25 mph, that part of the tire that is at bottom dead center is not moving forward at all while it is in contact with the ground. And that part of the tire that is at top dead center is moving forward twice as fast as I am, in this case 50 mph.

So here's what I've often stayed awake at night wondering about:

If I ride my bicycle at 3/4ths the speed of light, will the top of my tire be going at 1.5 times the speed of light? Or is the ultimate speed limit for a bicycle (or any wheeled or tracked vehicle) only 1/2 the speed of light?

And what happens if I crash?

Ok, I'll bite.

I would argue that the maximum speed, of a wheeled vehicle, completely ignoring the engineering challenges involved in this situation, would be slighty under 1/2 the speed of light. This is because, as you mention, the top of the wheel is going twice the speed in the opposite direction.

The centrifical force, created by such a wheel, would be phenomenal, and steering would be impossible.

If you were to crash, your atoms would probably be seived through whatever you crashed into. There wouldn't be anything left to even cremate. :D

Travelling at high speeds also creates a problem where various elementary particles would impact your craft and create intense radiation resulting in whatever life forms, travelling on that craft, not living too long due to massive irradiation.

Brian

Edited for accuracy....you could only go slighty under 1/2 the speed of light, not 1/2 the speed of light.

DancingBear
02-24-2008, 09:47 PM
...And what happens if I crash?

Your body is completely ground away in a record-setting case of road rash!

And with time dilation, it will seem to take forever... :D

Walt

aostling
02-24-2008, 09:57 PM
If I ride my bicycle at 3/4ths the speed of light, will the top of my tire be going at 1.5 times the speed of light?

No, but your example is thought-provoking. This Wikipedia article explains how relativistic velocities are not additive. http://en.wikipedia.org/wiki/Velocity-addition_formula

Evan
02-24-2008, 09:58 PM
The apex has no mass. It's only a position, but it is an observable one. If we are cutting a piece of paper with these scissors this position is the point separating the cut and uncut portions.

It not only doesn't have mass it isn't a "thing". What you describe is a phase effect. Even then, it cannot be observed to travel faster than light since all communications of information cannot exceed the velocity of light. Information has mass since it takes a certain non zero amount of energy to represent a bit of information. Because energy and matter are equivalent it is then impossible for the exchange of information to exceed the velocity of light in a vacuum. Because of that such superluminal phase effects cannot be used to transmit information.

Fasttrack
02-24-2008, 10:14 PM
Yep aostling is correct - classical mechanics can't be used here. The velocities don't sum "normally" and to further complicate things your wheel exsists in a non-inertial reference frame.

aostling
02-24-2008, 10:27 PM
It not only doesn't have mass it isn't a "thing". Even then, it cannot be observed to travel faster than light since all communications of information cannot exceed the velocity of light.

You are indisputably correct in saying that it cannot be observed traveling faster than the speed of light. If it can't be observed it must not exist, at least not after it has achieved "warp" speed. Describing it as nothing seems quite appropriate.

A.K. Boomer
02-24-2008, 10:38 PM
So here's what I've often stayed awake at night wondering about:

If I ride my bicycle at 3/4ths the speed of light, will the top of my tire be going at 1.5 times the speed of light? Or is the ultimate speed limit for a bicycle (or any wheeled or tracked vehicle) only 1/2 the speed of light?



Without all the other things that make it impossible (like centrifugal force and tire disintegration and such) Its impossible for the simple fact that the top forward part of the tire could never surpass the speed of light, so it would in fact hold the entire bike back to aprox. less than 1/2 the speed of light, it would do this because the said top part of the tire cannot go past the speed of light because it would grow in epic proportion and consume energies million fold as it even just approached the speed of light.

And yes, if you crashed at that speed - you could expect to get some pretty severe space rash, just for the fact that even the dust would tear holes in you, not to mention all the debris from all the Chinese and U.S. blunders:rolleyes:

darryl
02-24-2008, 11:19 PM
I've read that a photon doesn't travel smoothly, that it seems to go from point a to point b in no time, but spends a bit of time at each position. The time it waits, and the distance between points is what determines what we call the speed of light. If this is true, then either factor could change as long as the other changed to suit. The interaction with matter must change something, since we have the 'speed of light in a vacuum', implying that the speed is different in anything else except a vacuum. What would be changing- the wait time between points, or the distance between points? First of all, is this theory even supported nowadays?

Another things that crops up in my mind when I hear talk about the speed of light (in a vacuum) is that vacuum in not empty, as this statement seems to imply, it's actually rather full. So- fill it up more with its mysterious contents, and the speed of light might increase.

I better go take a vallium now. :)

Michael Edwards
02-24-2008, 11:24 PM
Had a piece come out of a four jaw chuck once, I swear it was going faster than the speed of light :)

ME

Fasttrack
02-25-2008, 12:25 AM
I've read that a photon doesn't travel smoothly, that it seems to go from point a to point b in no time, but spends a bit of time at each position. The time it waits, and the distance between points is what determines what we call the speed of light. If this is true, then either factor could change as long as the other changed to suit. The interaction with matter must change something, since we have the 'speed of light in a vacuum', implying that the speed is different in anything else except a vacuum. What would be changing- the wait time between points, or the distance between points? First of all, is this theory even supported nowadays?

Another things that crops up in my mind when I hear talk about the speed of light (in a vacuum) is that vacuum in not empty, as this statement seems to imply, it's actually rather full. So- fill it up more with its mysterious contents, and the speed of light might increase.

I better go take a vallium now. :)

That is a theory of light propagation - its based on the uncertainty prinicple. Thats actually where electrical and magnetic forces come from. The force is mediated by virtual photons that can exsist without detection because of the uncertainty principle. i.e. they pop in and out of exsistence.

Evan
02-25-2008, 01:09 AM
Another things that crops up in my mind when I hear talk about the speed of light (in a vacuum) is that vacuum in not empty, as this statement seems to imply, it's actually rather full. So- fill it up more with its mysterious contents, and the speed of light might increase.
You might be surprised to know that you aren't that far off. However, the trick is to reduce the contents of the vacuum. If one can restrict the possible modes of vibration of the sea of virtual particles in the vacuum as they pop in and out of existence then in theory the speed of light should increase. And so, in experiment it does. By placing two metal plates (very very smooth plates) extremely close together, on the order of wavelengths of light the possible vibration modes of electromagnetic waves are restricted in the space between the plates. It is then possible for a photon to travel at a velocity that is a tiny fraction faster than the usual velocity of light. Very tiny. somewhere around 10^-6 or -7 if I recall correctly. It's called the Casimir Effect. It doesn't represent something exceeding the velocity of light though. It represents the velocity of light being altered by changing the electrical characteristics of the vacuum.