The Shalimar Treaty

[Slick]

Not as of yet, no accurate method for determining gravity really exists. That method sounds to me like it would work, however its effect is very very small. The determination of gravity would obviously have to be a vector; strength and direction and be made extremely accurately such that the error in measurement is small compared to the value.


Since gravity has no maximum range, the earth is also being pulled by everything else in the universe (closer than the age of the universe x the speed of light). Since the force of gravity drops by the inverse square law, effects from mass outside our solar system will probably be too small to detect for a very long time, if ever.

There are other effects too that would affect the results:

Curvature of space - currently postulated, but measurement inaccuracy is far too large compared to numbers that we would need. At least our local section of space is "flat" i.e. not curved to the best of our measurements.

Dark matter - matter that does not give off light. Rocks, dust, gas, etc. Some scientists have postulated exotic forms of mass (wimps - weakly interacting, massive particles), but these too haven't been observed. But dark matter does exert gravitational forces. Based on rotational dynamics in the galaxy, there has to be a huge amount of dark matter; far more than the luminous matter that we can see. Not sure how much is in our solar system; or if it has a significant effect.

"Dark energy" - I really don't want to go there. Possible, but unobserved, and rather controversial. If it exists, though, it could/would affect gravity.

Expansion of space - the exact rate is debated, but it has upper and lower bounds based on observations. I'd have to see the numbers, but my guess is that this is too small to have an effect on our local orbit around the sun.

And of course the catch all - how can we know if there is something else that is currently totally unknown by us???

[Parasite]

Please don't forget about the speed of the sun around the galaxy and the galaxy through the universe. These would have to also all have to be taken into account. Check out the Michelson Morley experiment and what it failed to prove for more insight. There are also conservation of momentum issues with Jupiter speeding up around the sun. I suspect that there is a problem about the sun pulling Jupiter, then Jupiter pulling the sun, when the force is constant.

The state of gravity detector technology is such that they are not yet acurate enough to find the currently predicted size of gravity waves from things like galaxies colliding and black holes forming.

In regards to sound, the sonic boom rumbles on long after the plane has passed. This is the sound that started far away just now arriving (and echos and things). I suspect that a very good stereo microphone could do a back plot of a plane's position and path just from the sound it made when it passed and the boom afterward.

[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.

[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.