The Shalimar Treaty

[narf poit chez BOOM]

Do they have proof that gravity moves at the speed of light? The only arguements I've heard is that 'Nothing moves faster than the speed of light, so gravity can't move faster'.

[AngleWyrm]

As near as I can tell, the main argument against information travelling faster than the speed of light is that of causality. Most folks accept that effect cannot precede cause (in absolute time). Note how this is different from the assertion that time is relative. I tend to think that witnessing an effect before a cause does not necessarily violate causality. Like being struck by a bullet before hearing the gun go off. How is it different if we switch the media from sound to light?

Tom van Flandern has argued that the speed of gravity is much faster than light (like at least 200billion times c) in physics letters A 250. Steven Carlip argued against him in Aberration and the Speed of Gravity. Carlip accepts as a given that gravitic effects appear to arrive at earth from the sun much faster than the speed of light, even instantaneously. His argument against this effect is purely mathematical, and he suggests that some velocity-dependant factor in the formula almost cancels out the effects of propagation delay. He states other interpretation models are of course possible, but would cost the unity of the current mathematical model.

As for me, I've got my very own theory. It goes like this:
AngleWyrm's Gravitic Aether Pressure Theory.
Gravity is not an attractive force, it is a pressure experienced by all matter as it rushes "upward" through the aether. Aether is a sort of rain pressure/resistance that is the "downward" push that is imagined in the rubber-mat imagery, that causes things to roll downhill.

Hey, it seems to work for me

[Spoo]

AngleWyrm_2 said:I tend to think that witnessing an effect before a cause does not necessarily violate causality. Like being struck by a bullet before hearing the gun go off. How is it different if we switch the media from sound to light?

You CANNOT observe an effect before the cause, regardless of reference frame. You can be struck by a bullet before hearing it because the sound doesn't make the bullet hit you.

[AngleWyrm]

Spoo said:
You CANNOT observe an effect before the cause, regardless of reference frame. You can be struck by a bullet before hearing it because the sound doesn't make the bullet hit you.

Seeing the bullet exploding from the gun does not make the bullet hit you. Nor does observing the gunner shout "I will kill you now" and hearing the explosion that propelled the bullet. Observation of an event by an observer is something separate from the event itself.

I have clearly demonstrated a real and recordable instance of observing an effect before observing a 'cause'.

[Spoo]

AngleWyrm_2 said:

Seeing the bullet exploding from the gun does not make the bullet hit you. Nor does observing the gunner shout "I will kill you now" and hearing the explosion that propelled the bullet. Observation of an event by an observer is something separate from the event itself.

I have clearly demonstrated a real and recordable instance of observing an effect before observing a 'cause'.

Seeing the bullet leave the gun must happen first from anybody's point of veiw. Note that in this case there is a profound difference in using sound and using light to tell when the gun was fired. The speed of sound changes relative to the observer's motion. The speed of light, however, is always the same (by "speed of light" I mean the speed that photons travel at). This is why it's possible to hear the gun being fired after it hits you.

Let's say that the event of the bullet leaving the gun is the cause, and the bullet striking you is the effect. Suppose that I'm standing next to the gun. Clearly, I see and hear the gun go off before the bullet hits you.

Now let's say that I start running towards you at the speed of sound just before the gun is fired. I still see the gun go off before the bullet hits you, although I never hear the gun fire.

Finally, let's say I run towards you arbitrarily close to the speed of light. I still see the gun go off first. There is nothing that I can do, as an observer, to witness you being hit by the bullet before the gun goes off.

Regarding:

Observation of an event by an observer is something separate from the event itself.

Yes they are seperate. The actual event and it's observation are another example of cause and effect. You can't observe an event before it happens!

[Phoenix-D]

The speed of light is NOT always the same. You can very easily slow light down, you just can't kick it up past C.

"Finally, let's say I run towards you arbitrarily close to the speed of light. I still see the gun go off first. There is nothing that I can do, as an observer, to witness you being hit by the bullet before the gun goes off."

Say you have a gun that teleports the bullet to the target on firing. The target doesn't see anything, the bullet hits, and then a while later they see the flash, and hear the report.

This does notviolate cause and effect! The bullet was still fired before it hit..its exactly the same as seeing the hit then hearing it.

[Spoo]

Phoenix-D said:
The speed of light is NOT always the same. You can very easily slow light down, you just can't kick it up past C.

That's why I specified that I was refering to the speed that photons travel at. Light appears to move slowly through certain materials, but the individual photons still move at ~3x10^8m/s. In these cases what's happening is that photons are constantly being absorbed and reemitted, which makes the light appear to be moving slowly.

"Finally, let's say I run towards you arbitrarily close to the speed of light. I still see the gun go off first. There is nothing that I can do, as an observer, to witness you being hit by the bullet before the gun goes off."

Say you have a gun that teleports the bullet to the target on firing. The target doesn't see anything, the bullet hits, and then a while later they see the flash, and hear the report.

This does notviolate cause and effect! The bullet was still fired before it hit..its exactly the same as seeing the hit then hearing it.

Teleportation is science fiction.

[douglas]

Sorry, but just changing the direction you're ship is pointing won't change the measurements at all. You'd have to change your velocity for that, and you'd have to already know your velocity relative to the pulsar in order to tell when you had exactly reversed it, which renders the whole exercise pointless.

There's also another slight problem here. You know all these "stationary" observers we've been talking about? Technically whether something is stationary or not depends entirely on your frame of reference. There is no "absolute" or "superior" reference frame which defines what it means to be "stationary". The term "stationary" only really has meaning when you specify something like "stationary relative to the pulsar," which just means it's velocity is exactly the same as the pulsar's.

[AngleWyrm]

Spoo said:
Seeing the bullet leave the gun must happen first from anybody's point of veiw. Note that in this case there is a profound difference in using sound and using light to tell when the gun was fired. The speed of sound changes relative to the observer's motion. The speed of light, however, is always the same (by "speed of light" I mean the speed that photons travel at). This is why it's possible to hear the gun being fired after it hits you.

The Doppler effect applies to both sound (pitch changes) and light (red shift). It does not change the speed, only the frequency. The speed of sound changes with the rigidness of the medium through which it travels, and the speed of light changes with the refraction index of the medium through which it travels.

Now let's say that I start running towards you at the speed of sound just before the gun is fired. I still see the gun go off before the bullet hits you, although I never hear the gun fire.

Finally, let's say I run towards you arbitrarily close to the speed of light. I still see the gun go off first. There is nothing that I can do, as an observer, to witness you being hit by the bullet before the gun goes off.

These two examples are not orthinagonal. In the sound example, the traveller is accepted as travelling at the speed of sound, but in the light example the traveller is accepted as travelling less than the speed of light. It could be just as valid to switch the roles, and say running towards the target at light speed means you never see the gun go off, but running at some speed arbitrarily close to the speed of sound you still hear the gun go off.

[Slick]

That thump you just heard was Einstein rolling over in his grave.