Does Reciprocity Falsify Special Relativity?

Dale,

Fine, if you insist, let's get technical. The SI unit for mass is the kilogram. Since 1889, the SI system defines the unit to be equal to the mass of the international prototype of the kilogram, which is made from an alloy of platinum and iridium of 39 mm height and diameter, and is kept at the Bureau International des Poids et Mesures in Paris. The mass of that object is not determined by its volume, its composition, its resistance to change in motion, or the fact that it can't be accelerated to c. It is based on it's weight, or in other words, its gravitational attraction. In summary, the kilogram, which is the SI unit for mass, is derived only from an object's gravitational attraction. Since photons interact with gravity as well, they can be considered to have mass under SI units.

Now, you and other relativists, can add a whole bunch of other requirements that an object must possess in order for you accept that it has mass. You can claim that an object has to be a certain size, color, or shape, or that it has to smell a certain way. You can also exclude objects because they don't fit into the theories you adore (like relativity or string theory). I'll just stick to my old fashioned SI definition of mass, thank you.

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Let's take a hypothetical situation. Let's, for a second, assume that the speed of light is not equal to c for all inertial observers. Let's assume that photons use gravitational fields for propulsion, so the speed of light is only equal to c relative to the gravitational field that the light is passing through at the moment. If this is true, then an observer that is stationairy in a gravitational field will always measure the speed of light to be equal to c, while an observer that is moving through a gravitational field will measure a change in the speed of light. As a result, if an object is moving through a gravitational field, the speed of light in that object would increase or decrease depending on the lights direction. However, the average speed of light in an object that is moving through a gravitational field would decrease. Now if the average speed of light in an object that is moving through a gravitational field decreases, all of the fundamental interactions in that object that are the result of an exchange of light-speed particles would weaken. So chemical and other physical reactions would occur at a decreased rate, and all electronics would slow down since the average speed of the electric fields in their circuits would decrease. Of course this means that any clocks using these reactions to tell time would tick slower.

So how would you detect if time is slowing down or the speed of reactions is slowing down? First, you measure the speed of light in an object that is moving through a gravitational field. If the speed of light changes, then you measure the ticking rate of a light clock (a clock where a beam of light is bouncing between two mirrors) that is moving through a gravitational field taking into consideration the change in the speed of light. If the clocks ticking rate is equal to your calculations involving the change in the speed of light, then time is not slowing down. If the clock ticks slower than your calculations, then time is slowing down.

First, if you assume that time is slowing down, then you'll never find out why the reactions slowed down if it wasn't because of time. Second, why add another physical property (time) into physics if it's unnecessary.

 

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There's no problem with that, if you take the word "mass" to mean what most experts refer to as "mass/energy", or perhaps "relativistic mass". The notion of mass/energy is certainly meaningful.
The notion of relativistic mass is meaningful, though deprecated.

You do that

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. Did you notice that the SI mass is only useful if it's stationary?
If it's wiggling, its gravitational attraction is higher than 1kg!

So the SI standard is a rest mass standard. Do photons have rest mass?

 

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This is an old, old, argument. Have a read of this page for a summary of research on the topic back in the early 1900s.

Greater minds than ours have thought this through in detail long ago, Prosoothus.

 

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True, but the clock dilation factor wouldn't be the same as it is in relativity (which gives correct time dilation predictions), and would depend on the orientation in the case of the mirror clock, unless you include length contraction. If you include the length contraction formula you'd get all the same effects as in SR, including the apparent relativity of simultaneity, and c would still appear constant in all inertial reference frames.

Differences would be: no reciprocity (look out the window to see if people are going about their daily business faster or slower than usual), and there would only be one reference frame in which ALL moving clocks slowed down. In any reference frame in motion with respect to your aether or gravitational field, clocks travelling faster than the frame would slow down in the frame, but clocks moving more slowly than the reference frame would appear to be running faster.

 

Since we are communicating so nicely and politely on several other threads I really do not want to get irritating. I will politely point out that the SI definition of mass makes no reference to gravitational attraction (see NIST SP 330 pp. 5, 29). Instead it says:

"The kilogram is the unit of mass; it is equal to the mass of the international prototype of the kilogram."

In fact the SI definition goes out of its way to specifically exclude gravitational attraction from the definition when it says:

"Considering the necessity to put an end to the ambiguity which in current practice still exists on the meaning of the word weight, used sometimes for mass, sometimes for mechanical force ... The word “weight” denotes a quantity of the same nature as a “force”: the weight of a body is the product of its mass and the acceleration due to gravity; in particular, the standard weight of a body is the product of its mass and the standard acceleration due to gravity"

Now, obviously the SI definition of mass is circular, so it is not really a particularly good definition for settling this debate by appeal to authority. You certainly can note that the international prototype has f/a = w/g = m = 1kg as you expect. I certainly can note that it has |p|/c = m = 1kg as I expect. However, if we hurl the international prototype at .866c you will find that it suddenly has f/a = w/g = m = 2kg. On the other hand I note that it still has |p|/c = m = 1kg. The reason the standard definition is a preferable definition isn't because photons are massless, but because mass is frame invariant for any object using the standard definition.

Besides, if we use your definition of mass together with the SI standard we still wind up with massless photons. This is because by definition the kilogram standard cannot have a mass of 1kg at rest and 2kg at .866c and must instead always have a 1kg mass. Therefore, you would have to replace every occurance of m with γm in every physics formula. A theoretical 1kg mass going at c would thus have an infinite momentum and would give an infinite impulse as it collides with something. On the other hand, a photon going at c has a finite momentum and gives a finite impulse on collision and then must have 0 mass by your definition as well unless you abandon the SI standard. The SI standard, in this sense, is incompatible with the idea of relativistic mass as the "real" mass. In fact, the only way I can see to possibly have a massive photon is to use a system of units where force is the fundamental quantity and mass is a derived quantity.

-Dale

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I'm sure it was all clear, but:
|p| is the norm of the four momentum
c is the speed of light
γ is the time dilation factor
m is mass
f is force
a is acceleration
w is weight
g is the acceleration due to gravity

 

While this is a logical conclusion I point out that it is an assumption about how things might work in an absolute world. I don't think we have that luxury yet.

 

Pete,

I don't know. I've never stopped one.

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Pete,

Ah, the old stellar aberration arguement. In the dynamic aether model, as a photon travels into moving aether, it's path will change since aether is the photon's medium. And as you pointed out, there is no evidence that a photons path curves as it approaches the Earth.

In my model, the gravitational field is NOT the medium of the photon, space is. So in my model, as a photon enters a moving gravitational field, its path will not change (since the space did not change), only its speed will change so that it is travelling a c relative to the field. In other words, photons are not dragged around by gravitational fields as they would be with a dynamic aether.

 

przyk,

You're right, the clocks decreased ticking rate would not always be equal to the time dilation predicted by relativity. If the light clock's mirrors are faced forward and back, it's decreased tick rate would be greater than the time dilation predicted in relativity. If its mirrors are up-down, or left-right, its decreased tick rate would be equal to the time dilation predicted by relativity. But on average, the light clock's decreased tick rate would be a little bigger than the time dilation predicted by SR.

But let me stress that even though the tick rate of atomic clocks that circled the Earth was less then the same clocks that were stationairy on the Earth's surface, the recorded time dilation was not exactly equal to the time dilation predicted by relativity. The fact that the clocks ticked slower was proof enough for supporters of relativity.

Let me also say that because of an atomic clocks complex structure, the actual decreased ticking rate would not be that easy to calculate based on my model. But regardless, it's calculated decreased rate would not be significantly different than what is predicted by relativity.

Exactly.

 

DaleSpam,

The more I think about it, the more I believe that the term "mass" or "rest mass" should be excluded from physics. Maybe we should just use the terms "gravitational mass" and "inertial mass" to describe the different types of mass.

 

I certainly agree that some standardization of terminology would be quite useful. However, like all frame invariant quantities, the norm of the four-momentum (what most physicsts mean by "mass" or "rest mass") is much too useful of a concept to be discarded. I would instead tend to exclude "relativistic mass", which is what most people call the idea that you are describing as "mass", "inertial mass", and "gravitational mass".

However, as Pete pointed out on this thread and as BillyT has pointed out on other threads, relativistic mass can be a convenient concept. I think that the prefered (though not yet standard) practice is to allow both concepts. The norm of the four-momentum (divided by c) is usually called "mass" or "rest mass" and the norm of the three-momentum (divided by the three-speed) is usually called "relativistic mass".

-Dale