What Are the Mysteries Behind Rotation in Mathematics and Astronomy?

[D H]

Whats the difference? My understanding of "equivalent" is that while inertial and non inertial observers tries to make sense of the motion of an object, both of them make use of the same set of laws. Nature's laws don't vary with the reference frames. Just like Einstein made all the inertial frames equivalent "again" after the michelson-morley debacle, i thought he made ALL the reference frames equivalent.

You are mistaken. Nature's laws do in a sense vary with reference frames. There are no fictitious forces in an inertial frame. You can't even begin to describe the laws of motion in a rotating frame unless and until you know the frame's angular velocity and angular acceleration with respect to inertial.

 

[Dale]

we could also say that the distance between two points,difference in velocities between any two particles and a host of other quantities as absolutes. All these are absolutes w.r.t an inertial frame.

That was a mistake. I meant absolute w.r.t all inertial frames. Not "an inertial frame"

Neither the distance between two points nor the difference in velocities between two particles are frame invariant. Different frames will disagree and therefore they are both relative quantities. Things which are absolute and which are relative are well understood and have a coherent mathematical framework (Minkowski geometry) where the relative things are the components of four-vectors and the absolute things are the Minkowski norm of four-vectors. It is completely unambiguous.

 

[sganesh88]

Neither the distance between two points nor the difference in velocities between two particles are frame invariant. Different frames will disagree and therefore they are both relative quantities.

At speeds<<c, they are frame invariants (all inertial frames will agree). Check it out. For relativistic speeds, even acceleration ceases to be absolute- going by the definition of dv/dt.

 

[Dale]

For relativistic speeds, even acceleration ceases to be absolute- going by the definition of dv/dt.

No, proper acceleration is absolute, even at relativistic speeds. I think you are confusing coordinate acceleration which (obviously) depends on your coordinate system with proper acceleration which is frame invariant and which is the acceleration measured by accelerometers. Proper acceleration is frame invariant, it is the Minkowski norm of the four-acceleration, all reference frames agree on it, it is coordinate independent, it can be measured using accelerometers and without reference to any external object.

 

[Shahin.Omar]

I came upon the phase locking answer differently.

Thanks for explaining it as things should be explained without throwing your weight around, you know what I mean.

"Sagnac effect and ring laser gyros", I have not understood it very clearly, however if you rotate the gyros around stationary Earth's orbit, or you rotate the source of light around stationary Earth's orbit, in one of which situations, different from the original situation you will get the same result? And is not the use of source of light akin to using external reference point, given that I have not understood it very clearly, sorry?

Cheers!

 

[D H]

"Sagnac effect and ring laser gyros", I have not understood it very clearly, however if you rotate the gyros around stationary Earth's orbit, or you rotate the source of light around stationary Earth's orbit, in one of which situations, different from the original situation you will get the same result? And is not the use of source of light akin to using external reference point, given that I have not understood it very clearly, sorry

You have a very understandable misconception of how ring laser gyroscopes work. The use of the word gyroscope in the name is a bit of a misnomer. In a basic ring laser gyro there are no moving parts (the laser beam excepted, of course).

BTW, this doesn't make a bit of sense: "stationary Earth's orbit". If the Earth is stationary it isn't moving; it has no orbit.

 

[Shahin.Omar]

Ok guys, time to close this thread!

Case 1.

"The procedures for synchronizing clocks all over the globe must take the rotation of the Earth into account. The signals used for the synchronizing procedure can be in the form of electric pulses conducted in electric wires, they can be light pulses conducted in fiber optic cables, or they can be radio signals.

If a number of stations situated on the equator relay pulses to one another, will the time-keeping still match after the relay has circumnavigated the globe? One condition for handling the relay correctly is that the time it takes the signal to travel from one station to the next is taken into account each time. On a non-rotating planet that ensures fidelity: two time-disseminating relays, going full circle in opposite directions around the globe, will arrive at the originating station simultaneously. However, on a rotating planet, it must also be taken into account that the receiver moves during the transit time of the signal, shortening or lengthening the transit time compared to what it would be in the situation of a non-rotating planet.

It is recognized that the synchronization of clocks and ring interferometry are related in a fundamental way. Therefore the necessity to take the rotation of the Earth into account in synchronization procedures is also called the Sagnac effect."

Courtsy: http://en.wikipedia.org/wiki/Sagnac_effect

Obviously you cannot tell whether it was the 'number of stations' rotating about stationary Earth or it is the Earth rotating about its axis.

You cannot tell if an object is rotating or the observer, that is relativity for you.

Case 2.

If I want to put the 'gravity gradient torque' term in simple english; can I say, strong local gravity causes gradual decrease in angular momentum of smaller bodies?

Case 3.

This is simply a matter of probability. Consider a gas cloud composed of a specific number of particles (trillions and trillions and trillions). Now, suppose that those perticles are moving around randomly. What is the probability that it has no measurable angular momentum? It is vanishingly small. Indeed, if we did discover a star with no angular momentum we would be surprised. The answer to your question is simple statistics.

How do I test this explanation, and what is the basis of this explanation?

Let me try whatever I can; this explanation does look good when I look at planet Venus' rotation or may be murcury, earth, mars, etc. but does not look very convincing when I look at say Saturn.

Again there are certain high density stars that rotate at extremely speeds; explanation is when they were in gaseous state they rotated slow, as they became more and more dense their angular speed shot up. Let's do some reality check, you rotate a body fast, what happens, it starts to bulge. The process has a reverse order.

And how does this explain the rotation of Galaxies?

Further more what is a testable evidence that all bodies, before they were formed, were in gaseous state?

Sorry to say but a testable explanation does not exist.

However I must thank you all for your time and interest. I thoroughly enjoyed talking to you guys and it was a pleasure.

Have a very nice day!
Shahin

 

[D H]

Ok guys, time to close this thread!

Yes, but not for the reason you think. The reason to close this thread is because you are advocating nonsense.

Obviously you cannot tell whether it was the 'number of stations' rotating about stationary Earth or it is the Earth rotating about its axis.

One slight problem with this nonsense: The stations are fixed with respect to the surface of the Earth.

 

[Dale]

Obviously you cannot tell whether it was the 'number of stations' rotating about stationary Earth or it is the Earth rotating about its axis.

You cannot tell if an object is rotating or the observer, that is relativity for you.

There are two obvious things here, first, that you failed to understand the very link that you cited. It directly contradicts your conclusion above.

Second, it is obvious that you are a troll with an agenda, not an honest student. The correct information (rotation is absolute and detectable without reference to an external body) has been given to you multiple times along with specific examples of physical devices that can be used to experimentally measure rotation. Since you continue to make the same wrong assertions despite repeated correction you are obviously trolling and probably espousing an unscientific personal theory.

For the non-participating readers consider the following scenario. Two ring laser interferometers are in deep space. If laser A exhibits no interference fringes then it is (absolutely) not rotating. In A's rest frame objects without any external forces will move in a straight line and Newton's laws take their textbook form (A's frame is inertial). If laser B demonstrates interference fringes then it is (absolutely) rotating. In B's rest frame objects with no external forces will not move in a straight line. Newton's laws will be modified with centrifugal and Coriolis forces. The fact that B is rotating and A is not is unambiguous, and both A and B agree that it is B who is rotating. It is absolute and not relative, again there is no ambiguity: B knows that it is rotating and can demonstrate it using purely "internal" physics experiments.

 

[jambaugh]

You cannot tell if an object is rotating or the observer, that is relativity for you.

Sit on a turntable with your eyes closed and move your head forward and back slowly.
Do this for about 10 minutes and you'll know if its you turning or not. You'll find your breakfast in your lap if you are in a rotating frame.

You can claim its all relative but your inner ear knows different. It doesn't know theory it knows empirical sensation.

 

[ernestpworrel]

Sorry to burst some of your bubbles, but Shahin's right about the rotation thing.

 

[Kurdt]

You cannot tell if an object is rotating or the observer, that is relativity for you.

I suggest you review a relativity textbook. Since rotating frames do not have constant velocity they are not inertial frames.

This thread is done.