Earth's absolute speed

Howedar · Post by **Howedar** » 2003-07-07 11:42pm

I'm probably crazy, but hear (read?) me out.

The speed of light is an absolute speed limit in the universe. Since it does not vary when one changes their reference point, the speed of light must be WRT some arbitrary point in the universe.

The general theory of relativity specifies that mass increases with speed. This increase is not linear.

If sufficiently accurate and precise equipment existed, it ought to be possible to find an object's mass very very precisely on Earth.

Then one could accelerate it a known amount and see the change in mass. I guess this could be repeated several more times for more data points, but I don't think it would be necessary.

This would give us the change in mass WRT the change in speed of a given object, with Earth's absolute velocity as a starting point. One could then take the data and match it to the curve of mass increase WRT percent of lightspeed.

One could find the absolute speed of Earth as a fraction of the speed of light.

Right?

Sindai · Post by **Sindai** » 2003-07-07 11:55pm

Nope. Earth has no "absolute" speed. Nothing does. All velocity measurements are relative.

The next best thing would be finding Earth's velocity relative to the point at which the Big Bang originated. But then, I believe it's been establshed that that's increasing.

The speed of light is an absolute speed limit in the universe. Since it does not vary when one changes their reference point, the speed of light must be WRT some arbitrary point in the universe.

This is also incorrect. The speed of light is absolute with regard to every point and at every speed in the universe. It is impossible to exceed the speed of light relative to another object.

Alyeska · Post by **Alyeska** » 2003-07-08 12:09am

So... If Earth was moving along at 50 kmh in its orbit and someone fired a laser beam from Earth in the same direction Earth was moving, that laser beam would be moving .C minus 50kmh?

kojikun · Post by **kojikun** » 2003-07-08 12:18am

Alyeska wrote:So... If Earth was moving along at 50 kmh in its orbit and someone fired a laser beam from Earth in the same direction Earth was moving, that laser beam would be moving .C minus 50kmh?

No, it would be moving at C. Thats the crazy part, if you have a flashlight moving at 99.999% C and turned on a light, from outside perspective if would be moving at 100% C, and from your perspective it would seem to be moving AWAY FROM YOU at 100% C. It ALWAYs appears to move at C.

Durandal · Post by **Durandal** » 2003-07-08 12:33am

Howedar wrote:The speed of light is an absolute speed limit in the universe. Since it does not vary when one changes their reference point, the speed of light must be WRT some arbitrary point in the universe.

The speed of light has the same value in all frames of reference.
There is no preferred frame of reference.

Welcome to the special theory of relativity.

If sufficiently accurate and precise equipment existed, it ought to be possible to find an object's mass very very precisely on Earth.

If you know a sphere's volume, it is a simple matter of measuring the curve of light as it passes at a distance r away from the sphere's center of gravity.

This would give us the change in mass WRT the change in speed of a given object, with Earth's absolute velocity as a starting point. One could then take the data and match it to the curve of mass increase WRT percent of lightspeed.

Earth has no absolute velocity. It is in orbit around the sun and therefore under constant acceleration.

Alyeska · Post by **Alyeska** » 2003-07-08 12:34am

kojikun wrote:
Alyeska wrote:So... If Earth was moving along at 50 kmh in its orbit and someone fired a laser beam from Earth in the same direction Earth was moving, that laser beam would be moving .C minus 50kmh?
No, it would be moving at C. Thats the crazy part, if you have a flashlight moving at 99.999% C and turned on a light, from outside perspective if would be moving at 100% C, and from your perspective it would seem to be moving AWAY FROM YOU at 100% C. It ALWAYs appears to move at C.

How the fuck does that work? If a ship is moving at 200,000 km per second and they fire a beam of light, will it appear to the ship that the beam of light is moving at .c+200,000km a sec? How the hell can it do that and still move at .c to a "stationary" observer?

Howedar · Post by **Howedar** » 2003-07-08 12:39am

Durandal wrote: The speed of light has the same value in all frames of reference.
There is no preferred frame of reference.

Welcome to the special theory of relativity.

Then how can c be considered to be 3e8m/s? If c is not an absolute limit, then how can it be a limit at all? It makes no sense to say that c is always 3e8m/s from any and every reference point. If I'm moving a .999c, light can't appear to move away at 3e8m/s.

kojikun · Post by **kojikun** » 2003-07-08 12:43am

Alyeska wrote:How the fuck does that work? If a ship is moving at 200,000 km per second and they fire a beam of light, will it appear to the ship that the beam of light is moving at .c+200,000km a sec? How the hell can it do that and still move at .c to a "stationary" observer?

Einsteinian magic and time dilation. From the ships perspective, the beam appears to be moving away from them at precisely C because time is slowed down for them or something like that. It's WIERD. I don't know how or why, but its been shown to be real.

Alyeska · Post by **Alyeska** » 2003-07-08 12:44am

kojikun wrote:
Alyeska wrote:How the fuck does that work? If a ship is moving at 200,000 km per second and they fire a beam of light, will it appear to the ship that the beam of light is moving at .c+200,000km a sec? How the hell can it do that and still move at .c to a "stationary" observer?
Einsteinian magic and time dilation. From the ships perspective, the beam appears to be moving away from them at precisely C because time is slowed down for them or something like that. It's WIERD. I don't know how or why, but its been shown to be real.

I don't care about appearances, I want to know absolutes. If a ship is moving at half light speed and fire a laser, its real speed is only half light speed?

kojikun · Post by **kojikun** » 2003-07-08 12:45am

Howedar wrote:Then how can c be considered to be 3e8m/s? If c is not an absolute limit, then how can it be a limit at all? It makes no sense to say that c is always 3e8m/s from any and every reference point. If I'm moving a .999c, light can't appear to move away at 3e8m/s.

It does anyway. Something to do with time dilation or some bullshit. But they've proven it. Thats one of the reasons I find relativity to be more insane then quantum mechanics. 'Improbability, not insanity!' I say.

Darth Garden Gnome · Post by **Darth Garden Gnome** » 2003-07-08 12:45am

Holy goddamn, relativity gives me headaches (especially 'cause I was last in 9th grade science; spare my puny mind!). How can people stand to learn this stuff? Oi.

kojikun · Post by **kojikun** » 2003-07-08 12:49am

Alyeska wrote:I don't care about appearances, I want to know absolutes. If a ship is moving at half light speed and fire a laser, its real speed is only half light speed?

The beams speed is C. Always, regardless of frame of reference.

Alyeska · Post by **Alyeska** » 2003-07-08 12:56am

kojikun wrote:
Alyeska wrote:I don't care about appearances, I want to know absolutes. If a ship is moving at half light speed and fire a laser, its real speed is only half light speed?
The beams speed is C. Always, regardless of frame of reference.

That is quite literaly impossible. Light can not travel at two different speeds at two different reference points. If light is traveling at .C PLUS the speed of the reference point, it MUST be traveling FTL to a "stationary" reference point.

RedImperator · Post by **RedImperator** » 2003-07-08 12:59am

What if two objects are moving away from each other at, say, 151,000 km/s each. From one object, would the apparent velocity of the other object be greater than c, or would it be that since the light from one object could never catch up to the other, it's impossible to measure and from the perspective of each object, the other doesn't exist?

Slartibartfast · Post by **Slartibartfast** » 2003-07-08 01:09am

kojikun wrote:
Alyeska wrote:So... If Earth was moving along at 50 kmh in its orbit and someone fired a laser beam from Earth in the same direction Earth was moving, that laser beam would be moving .C minus 50kmh?
No, it would be moving at C. Thats the crazy part, if you have a flashlight moving at 99.999% C and turned on a light, from outside perspective if would be moving at 100% C, and from your perspective it would seem to be moving AWAY FROM YOU at 100% C. It ALWAYs appears to move at C.

Wouldn't it describe some sort of curve?

kojikun · Post by **kojikun** » 2003-07-08 01:10am

Alyeska wrote:That is quite literaly impossible. Light can not travel at two different speeds at two different reference points. If light is traveling at .C PLUS the speed of the reference point, it MUST be traveling FTL to a "stationary" reference point.

Which is why when we see it occur in real life we are completely baffled and mystified.

RedImperator wrote:What if two objects are moving away from each other at, say, 151,000 km/s each. From one object, would the apparent velocity of the other object be greater than c, or would it be that since the light from one object could never catch up to the other, it's impossible to measure and from the perspective of each object, the other doesn't exist?

no, both objects would, from one anothers frame of reference, appear to be moving very close to but never crossing C.

Raxmei · Post by **Raxmei** » 2003-07-08 01:16am

For the relativistically impaired: Relativity in Simple Words

SyntaxVorlon · Post by **SyntaxVorlon** » 2003-07-08 02:00am

Gotta love AL.

kojikun · Post by **kojikun** » 2003-07-08 02:04am

SyntaxVorlon wrote:Gotta love AL.

I hate the incestuous German prick. EINSTEIN KILLED NEWTON!! And our hopes of FTL

Howedar · Post by **Howedar** » 2003-07-08 02:53am

Ah fuck. Damn science teachers, relativity is even more confusing than I thought.

Shadow WarChief · Post by **Shadow WarChief** » 2003-07-08 03:19am

There's the time dilation formula. Read and proceed with the weeping.

kojikun · Post by **kojikun** » 2003-07-08 03:37am

Howedar wrote:Ah fuck. Damn science teachers, relativity is even more confusing than I thought.

you bet your sweet ass it is

Cyborg Stan · Post by **Cyborg Stan** » 2003-07-08 03:43am

The velocities don't add up smoothly. Instead of w = (u + v) like in Newtonian mechanics, we have to use w = (u + v)/(1 + ((u*v)/c²))

Code: Select all

A=====x
                              B
                                         x======C

In this case, if A and C are both traveling .5c in relation to B, plug in .5c for u and v and we get a speed of .8c relative to each other in their own reference frames, instead of 1c we'd normally expect. If they were travelling .75c relative to B, we'd get .96c. If they were somehow going 1c relative to B each, it's easy to demonstrate that (1 + 1)/(1 + 1*1/1²) = 1. (You can also see that if only one of them is traveling at c relative to b, what the universe would look like. (1 + v)/(1 * 1*v/1²) = (1+v)/(1+v) = 1.)

(Edit : Please excuse the

Code: Select all

=====x

representation of a light beam.)

kojikun · Post by **kojikun** » 2003-07-08 03:53am

and to think einstein derived his equations from Maxwells theories.

ClaysGhost · Post by **ClaysGhost** » 2003-07-08 05:37am

Ok, this is a long post, but then if people ask these questions they should be prepared for a lot of reading, or pictures. Since I have no pictures, have to use words instead

Howedar wrote:Then how can c be considered to be 3e8m/s? If c is not an absolute limit, then how can it be a limit at all?

It is an absolute limit. Why? Special relativity makes two assumptions;

* That the speed of light is constant with respect to all observers

* That the laws of physics are the same for all inertial (unaccelerated) observers.

The second assumption was weakened by General relativity, which extends the relativistic principle to accelerating, non-inertial frames. The first assumption is of interest here (Incidentally, note that the "forbidden" nature of travelling FTL is not an assumption of special relativity - the assumption is merely that the speed of light is the same in all frames).

Why did Einstein use the first assumption? It's a boring fact that of the many webpages criticising relativity on the basis of its assumptions*, none of them that I have seen address the reason behind assumption 1. Einstein was motivated to include it by Maxwell's theories of electromagnetism. By substituting a sinusoidally oscillating electric field (i.e. the electric field of a lightray) into Maxwell's equations, you can determine that this is only a valid solution to Maxwell's equations if the oscillating electric/magnetic field travels at a constant speed - c, 3x10^8 m/s. Any other speed, and you haven't got a solution, and you haven't got a lightray/wave.

Einstein described a thought experiment where you fire a light ray off into the distance, and then you run faster and faster until you're travelling at c - at which point the lightray will appear static before you. But no such thing can exist according to Maxwell's equations. The lightray would cease to exist as soon as you moved even slightly with respect to its fields, because then the velocity of the lightray would not be precisely c as far as you're concerned. Even better, if you have two people looking at the same ray, and one of them is moving relative to the lightray and the other is not, you will get bollocks - one will see a lightray and the other will see nothing. One will measure an energy and the other will not. Hence you make a mockery of CofE, and of CofM.

Fine, said Einstein, then that must mean that the speed of a lightray with respect to all observers must be c. Otherwise we have to break conservation laws and explain why it is that the ground doesn't become invisible when you turn your head. Alternatively, Maxwell's laws are incorrect descriptions of light. Either way, something is wrong - either Galileo/Newton or Maxwell (Gauss, Ampere, Faraday and that jammy bastard Lenz++) are wrong because putting Newton's absolute time and space together with Maxwell's equations produces a physically incorrect result. Relativity preserves Maxwell's equations, not Newton's absolute time and space, and it looks like Maxwell beat Newton. In the end, Newton's laws break down every day in accelerators, both natural and artificial, and in many other contexts.

It makes no sense to say that c is always 3e8m/s from any and every reference point. If I'm moving a .999c, light can't appear to move away at 3e8m/s.

You have to ask; .999c with respect to what? You're putting in an absolute coordinate system when no such beast exists. Let's refine this. Two observers, A and B. In A's frame of reference, let B be moving with velocity .999c in some convenient direction, say in the direction of the positive X axis, and lets have it that B's X,Y,Z axes line up with A's X,Y,Z axes for simplicity. Now, B fires a light beam along its direction of travel. In A's frame of reference, the lightray travels at c. Now, let's switch to B's frame of reference. As far as B is concerned, A is moving "backwards" along B's negative X axis at .999c. The lightbeam is travelling along the positive X axis at c. So there must be a contradiction, mustn't there, because one observer moving with respect to another has come up with the same speed for the lightray?

Ok. What have we got?

A says B is travelling at 0.999c in its frame of reference (down the positive X axis).
A says the lightray is travelling at c (down the positive X axis).
B says A is travelling at 0.999c in its frame of reference (down the negative X axis).
B says the lightray is travelling at c (down the positive X axis).

So, how fast does A say that that the lightray is moving with respect to B? A has measured both the lightray's velocity and B's velocity in its frame of reference. So we don't need to do anything but subtract them. A says the lightray is moving at 1 - 0.999 = 0.001c with respect to B. The lightray is slowly getting away from B according to A.

What does B say about the separation velocity of the lightray and observer A? Again, B has measured all the velocities in its own frame, so no complicated transformation is necessary - the relative velocity is 1 - (-0.999) = 1.999c. B says the lightray is storming ahead of A.

This should all look familiar. No relativistic Lorentz transform was necessary, we can simply add and subtract velocities because we're only asking questions that involve velocities measured in the same frame. In your original statement, quoted above, I've replaced you with observer B, and you're moving at 0.999c with respect to observer A. Observer B thinks that the lightray is moving ahead of them at c. Observer A says that the lightray is only moving ahead of B at 0.001c, so according to A, light isn't moving away from you (observer B) at c. A says only that the lightray is moving away from them at c. Yes.

*Congratulations on making it to this footnote. I can't believe I wrote all that. Anyway, I was thinking of "collecting" relativity criticisms and putting the links on a webpage, but maybe it's been done already. Anyone know?

++I can't believe that Lenz got his name into physics on the back of a minus sign. That must be the shortest law in the whole of physics.