Optical Detection of Earth's Coriolis Force?

[Geremia]

Is there an experiment that uses photons or other particles to measure the effect of Earth's rotation on them? Thanks

 

[Dr Lots-o'watts]

Is that an indirect way to ask if photon experiences the Coriolis force?

Worded differently:

Suppose a beam of photons is emitted from the north pole, tangentially to the Earth's surface (so as to maximize a hypothetical Coriolis effect), will it follow the same trajectory as a beam of electrons emitted in the same direction (assuming no atmosphere)?

A mathematical (in)validation of this would also be interesting.

(hoping I'm not to far off your intended topic)

 

[Dale]

Laser ring interferometers can indeed measure the Earth's rotation.

 

[ttdb]

i'm sorry, I'm a newbie here. could you explain how a laser ring interferometer actually work?

 

[Geremia]

Is that an indirect way to ask if photon experiences the Coriolis force?

Not just photons but other particles, too, yes

Worded differently:

Suppose a beam of photons is emitted from the north pole, tangentially to the Earth's surface (so as to maximize a hypothetical Coriolis effect), will it follow the same trajectory as a beam of electrons emitted in the same direction (assuming no atmosphere)?

A mathematical (in)validation of this would also be interesting.

(hoping I'm not to far off your intended topic)

No, this is good.

 

[Dr Lots-o'watts]

Precision/correction to my earlier post : An initial direction that is tangential to the north pole maximizes our perception that the Coriolis effect accelerates things "towards the right". The Coriolis effect as such doesn't actually depend on latitude, only its lateral and radial components.

As for a mathematical proof that it doesn't affect a photon, it suffices to say that Fcoriolis as classically defined is proportional to the mass of the particle, which for a photon is zero, so Fcoriolis(photon) = 0, QED. If any corresponding effect can be calculated with GR, it is beyond my personnal scope.

As for ring lasers:

http://en.wikipedia.org/wiki/Sagnac_effect#Ring_lasers.

 

[Dale]

As for a mathematical proof that it doesn't affect a photon, it suffices to say that Fcoriolis as classically defined is proportional to the mass of the particle, which for a photon is zero, so Fcoriolis(photon) = 0, QED. If any corresponding effect can be calculated with GR, it is beyond my personnal scope.

This line of reasoning doesn't work. Remember, if something is massless then it doesn't require any force to accelerate it. I.e. by Newton's 2nd law a=f/m=0/0 which is undefined, not zero.

In fact, when a force is proportional to the mass what that implies is that the acceleration is independent of the mass, and it will therefore accelerate a massless particle exactly the same as a massive particle.

 

[Geremia]

This line of reasoning doesn't work. Remember, if something is massless then it doesn't require any force to accelerate it.

Okay, then let's work with, e.g., atoms of noble gases.

 

[Cleonis]

Is there an experiment that uses photons or other particles to measure the effect of Earth's rotation on them? Thanks

As DaleSpam pointed out, there is purely optical equipment that measures the Earth's rotation: a ring laser interferometer measures the Earth's rotation with respect to inertial space.

However, the operating principle of ring laser interferometry is unrelated to Coriolis-type effects arising from the Earth's rotation.



Even in the case of ballistics detection of Earth rotation effects is difficult, if not impossible. During the flight through the atmosphere there are several air drag effects that will always swamp out any rotation of Earth effect. That is, in ballistics it is pointless to take rotation of Earth effects into account; you won't be able to tell the difference anyway.

Bullets travel too fast, the duration of the flight is too short. The deviation arising from Earth rotation effect is far smaller than the accuracy of the gun shot; any Earth rotation effect will be swamped.

You may have a chance with bolts fired with a high performance crossbow. I have read descriptions of indoor sessions where an incredibly tight grouping was achieved. Crossbow bolts may move slow enough to allow Earth rotation effects to be discernable.


Clearly, light and close-to-lightspeed particles move way, way too fast. I am convinced there is no chance at all of detecting Coriolis-type Earth rotation effects with light or close-to-lightspeed particles.

 

[dlgoff]

... in ballistics it is pointless to take rotation of Earth effects into account; you won't be able to tell the difference anyway.

Not so.

The Coriolis effects became important in external ballistics for calculating the trajectories of very long-range artillery shells. The most famous historical example was the Paris gun, used by the Germans during World War I to bombard Paris from a range of about 120 km (75 mi).

http://en.wikipedia.org/wiki/Coriolis_effect

 

[Cleonis]

The Coriolis effects became important in external ballistics for calculating the trajectories of very long-range artillery shells. The most famous historical example was the Paris gun, used by the Germans during World War I to bombard Paris from a range of about 120 km (75 mi).

http://en.wikipedia.org/wiki/Coriolis_effect

Yes, the Paris gun did exist, but it's aim was so terribly bad that it was useless for military offensive. It could only be used as psychological weapon, and that is what the Germans did. The shells could land anywhere in a five mile radius or so. None of the shells that was fired hit the city centre, they all landed in suburbs. But the fact that the gun could reach Paris was a terror factor of course.

The explosions were so violent that a lot of material was scraped from the inside of the barrel. The shells had to be fired in a precise sequence. Each next shell was a bit bigger, to compensate for the successive enlargement of the bore. After a dozen shots or so the barrel had to be transported back to the factory for resurfacing.

With other artillary it was possible to home in on a target. You fired a shot, you noted how far off you were, and then you applied corrections to elevation and direction. But the shots from the Paris gun just didn't repeat, so there was no point in trying to correct.

Bottom line: the story of the Paris gun being corrected for Earth rotation effect is a myth.

This talk about ballistics is off-topic. I am as much to blame, I mentioned ballistics when I wanted to illustrate that in all kinds of cases the Earth rotation effect is indiscernible.

 

[dlgoff]

This talk about ballistics is off-topic. I am as much to blame, I mentioned ballistics when I wanted to illustrate that in all kinds of cases the Earth rotation effect is indiscernible.

bolding by me.

Still wrong. The Earth's rotation indeed does effect a massive particles trajectory. And the OP now is asking about massive objects.

For small arms, the Coriolis effect is generally insignificant, but for ballistic projectiles with long flight times, such as extreme long-range rifle projectiles, artillery and intercontinental ballistic missiles, it is a significant factor in calculating the trajectory.

http://en.wikipedia.org/wiki/External_ballistics#Coriolis_drift"

 

[Andy Resnick]

Okay, then let's work with, e.g., atoms of noble gases.

I don't have access to this paper, but they may need to make corrections in atomic fountain clocks:

http://iopscience.iop.org/0026-1394/42/5/012

 

[Cleonis]

http://en.wikipedia.org/wiki/External_ballistics#Coriolis_drift"

The question of the original poster was whether experiments are conducted to find a Coriolis-type Earth rotation effect for light or for close-to-lightspeed particles.
I don't think such experiments exist, and I don't think any physicist considers such a setup.


External ballistics:
As far as I know in extreme long range rifling (range 1.5 kilometer) grouping within a radius of a meter or so can be achieved. With a nozzle velocity in the order of two or three times the speed of sound I estimate flight time will be a couple of seconds. That gives an Earth rotation effect in the order of 10 or 20 centimeter.
That's interesting. I suppose manufacturing precision has by now been pushed to a level where Earth rotation effect just comes into play.

I'm unfamiliar with modern artillary aiming capabilities. I only know that for WWI and WWII artillary Earth rotation effect was swamped by other factors affecting accuracy.