What would reality be like without SR?

[teachmemore]

I would like to start a brain storming thread, listing all the possible complications that would arise from NOT having SR.

SR is what makes our reality what it is, so I expect that without SR, some serious complications would arise.

Surely SR, is not just some insignificant nuance of reality. It must have some deeply profound effects on the way we perceive the universe and the way reality operates at the atomic level. So if we suddenly lost SR, what would happen to reality?

Edit: Maybe I should have made the topic heading "Why does reality depend on SR?", that may have been more accurate, since there probably wouldn't be reality without it. What I would really like to get at in this thread is "why" reality is dependent on SR. Why is SR important to our reality and how would a failing of SR implicate reality?

 

[HallsofIvy]

Well, reality was very well described long before SR so I doubt that much would change. The only time relativity comes into play is at very very high relative speeds or very very small distances. Atomic energy would not exist and neither would atomic bombs.

Oh, dear! Without the H->He reaction the sun would not burn! That would be a sizeable problem wouldn't it? Actually, I think the best answer would be that without relativity, we wouldn't be here to ask the question!

 

[matheinste]

What would reality be like without SR?

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Much less interesting.

Matheinste.

 

[teachmemore]

Well, reality was very well described long before SR so I doubt that much would change. The only time relativity comes into play is at very very high relative speeds or very very small distances. Atomic energy would not exist and neither would atomic bombs.

Oh, dear! Without the H->He reaction the sun would not burn! That would be a sizeable problem wouldn't it? Actually, I think the best answer would be that without relativity, we wouldn't be here to ask the question!

LOL! yes, that is what my speculation was. The physical properties of reality would break down to the point where none of our reality could be possible. I would like to use this thread to brainstorm all the reasons why this is case. Why our reality would be impossible without SR! You have got us on a good start!

 

[John232]

The speed of light wouldn't be a constant and could be measured to have different speeds from objects traveling at different velocities. The only reason why we have special relativity is because the speed of light doesn't change. How else could an object traveling at any speed measure another objects speed to always be the same?

 

[Mentz114]

Maxwell's equations demand SR. Without SR we would not have a working theory of the EM field.

That is to say that paradoxes would be predicted, wherein two observers would diagree on whether a third observer existed or not. Very tiresome.

 

[turbo]

The speed of light wouldn't be a constant and could be measured to have different speeds from objects traveling at different velocities. The only reason why we have special relativity is because the speed of light doesn't change. How else could an object traveling at any speed measure another objects speed to always be the same?

Read Einstein's book on relativity (Special and General). He said that the constancy of the speed of light could only be true in the absence of gravity, since the bending of light by massive objects was refraction, and had to involve the slowing of light in the presence of masses. Not a real popular concept these days, but it shows that he thought GR had superseded SR in significant ways. Check Chapter 22.

http://www.bartleby.com/173/

In the second place our result shows that, according to the general theory of relativity, the law of the constancy of the velocity of light in vacuo, which constitutes one of the two fundamental assumptions in the special theory of relativity and to which we have already frequently referred, cannot claim any unlimited validity. A curvature of rays of light can only take place when the velocity of propagation of light varies with position. Now we might think that as a consequence of this, the special theory of relativity and with it the whole theory of relativity would be laid in the dust. But in reality this is not the case. We can only conclude that the special theory of relativity cannot claim an unlimited domain of validity; its result hold only so long as we are able to disregard the influences of gravitational fields on the phenomena (e.g. of light).

 

[bcrowell]

The only time relativity comes into play is at very very high relative speeds or very very small distances. Atomic energy would not exist and neither would atomic bombs.

Oh, dear! Without the H->He reaction the sun would not burn!

I don't think this is right. You could still have nuclear interactions without SR. People like to use nuclear bombs as an example of E=mc2, but E=mc2 applies to a rusting nail just as much as it applies to a nuclear bomb. It's just a different amount of mass-energy.

I don't think it makes much sense to ask what reality would be like without SR. Too much of physics depends on SR. Maxwell's equations wouldn't be logically self-consistent. You'd have to decide what to replace SR with. You'd have to have an alternative cosmology.

IMO it's a valid scientific question to ask what the universe would be like with a small perturbation to a coupling constant, mass of a fundamental particle, etc., but if you ask what it would be like if Aristotle had been right, or if heat had really been described by a caloric fluid, you just can't say anything reasonable. There is a spectrum between these extremes, and dumping SR is at the same end of the spectrum as Aristotelianism and caloric fluid.

 

[JesseM]

Well, reality was very well described long before SR so I doubt that much would change. The only time relativity comes into play is at very very high relative speeds or very very small distances. Atomic energy would not exist and neither would atomic bombs.

Oh, dear! Without the H->He reaction the sun would not burn! That would be a sizeable problem wouldn't it? Actually, I think the best answer would be that without relativity, we wouldn't be here to ask the question!

But the older accounts of reality didn't really deal with atomic bonding (or other basic aspects of solid state physics) which we now know to be based on the electromagnetic force which is Lorentz-invariant. A world where intra-atomic forces obeyed Galilei-invariant laws would probably be fairly different even if you ignore the nuclear fusion issue.

 

[John232]

Read Einstein's book on relativity (Special and General). He said that the constancy of the speed of light could only be true in the absence of gravity, since the bending of light by massive objects was refraction, and had to involve the slowing of light in the presence of masses. Not a real popular concept these days, but it shows that he thought GR had superseded SR in significant ways. Check Chapter 22.

http://www.bartleby.com/173/

I don't see how changing the path of light to a curved path changes its speed. Have they measured the speed of light and showed a difference in speed near a mass and not? I don't see why spacetime dilation should even take place near gravity if the speed is altered. Then couldn't c change in order to fit the measurments of the observer for them to keep the same distance and time?

 

[turbo]

I don't see how changing the path of light to a curved path changes its speed. Have they measured the speed of light and showed a difference in speed near a mass and not? I don't see why spacetime dilation should even take place near gravity if the speed is altered. Then couldn't c change in order to fit the measurments of the observer for them to keep the same distance and time?

Very small effects, and the masses need to be large and well-understood. Einstein claimed that gravitational deflection of light is due to refraction. Of course, he also claimed in 1920 and in 1924 that space was an active player in gravitation, inertial effects, and light propagation. Don't hold your breath, unless you can wait until LQG can model the first, and infer the second, and observational astronomy can conform the third.

 

[bcrowell]

Read Einstein's book on relativity (Special and General). He said that the constancy of the speed of light could only be true in the absence of gravity, since the bending of light by massive objects was refraction, and had to involve the slowing of light in the presence of masses.

The local speed of light is still fixed in GR. GR simply doesn't have any meaningful way of talking about non-local speeds.

 

[turbo]

The local speed of light is still fixed in GR. GR simply doesn't have any meaningful way of talking about non-local speeds.

Not according to Einstein, who claimed that massive objects retard the propagation speed of light in their vicinity. He claimed that light-propagation speeds slowed in the presence of mass, causing light to bend in a refractive effect.

 

[JesseM]

Not according to Einstein, who claimed that massive objects retard the propagation speed of light in their vicinity. He claimed that light-propagation speeds slowed in the presence of mass, causing light to bend in a refractive effect.

But it's clear from the context he was talking about light slowing in some well-defined coordinate system such as Schwarzschild coordinates, and he would have been the first to acknowledge that all coordinate systems are equally valid in GR.

 

[turbo]

But it's clear from the context he was talking about light slowing in some well-defined coordinate system such as Schwarzschild coordinates, and he would have been the first to acknowledge that all coordinate systems are equally valid in GR.

Have you some writings from him that show him adopting that coordinate-system model? He was quite explicit about refractive effects in 1920, the same year that his Leiden address equated the vacuum with a variable ether. He expanded upon this 1924, with some improvements, but the theme was the same. In his ether mode. the vacuum plays a dynamic role in gravitation, inertial effects, and the propagation of light.

There have been hints of frequency-dependent delays in the arrival times of EM pulses. Perhaps we might approach the question from the experimental/observational side some day.

 

[JesseM]

Have you some writings from him that show him adopting that coordinate-system model?

Not sure what you even mean by this, do you disagree that "velocity" is an inherently coordinate-dependent concept? Leaving aside his verbal formulations and looking at the equations he wrote in any given paper, I'm sure that any time he calculates the velocity of a light beam it's always clear from the context what coordinate system he is using at the time, if you think there are any cases where it isn't clear please post them. And Einstein certainly emphasized the idea that all coordinate systems are equally good in GR, see here for example.

 

[PAllen]

Not according to Einstein, who claimed that massive objects retard the propagation speed of light in their vicinity. He claimed that light-propagation speeds slowed in the presence of mass, causing light to bend in a refractive effect.

Only when a nonlocal measurement is made, e.g. measuring light passing a dense, massive, object from a distance. A lab on surface of said object measures c in all directions. This follows trivially from the metric structure of GR (local lorentz invariance). If you think Einstein didn't understand this, you are seriously mistaken.

 

[lugita15]

Well, reality was very well described long before SR so I doubt that much would change. The only time relativity comes into play is at very very high relative speeds or very very small distances. Atomic energy would not exist and neither would atomic bombs.

Oh, dear! Without the H->He reaction the sun would not burn! That would be a sizeable problem wouldn't it? Actually, I think the best answer would be that without relativity, we wouldn't be here to ask the question!

I'm not so sure that relativity is necessary to explain atomic bombs. The idea that a group of particles can have some internal energy due to a binding potential, and the idea that you can use that energy by separating these particles, seem fully classical to me. I don't know why you would need mass-energy equivalence to explain it. I suppose that by knowing the mass of a Uranium nucleus you could determine how much of the mass is due to the binding of the nucleons, and so you could find out exactly how much binding energy there is to be tapped. But the physical phenomenon of nuclear reaction would still be possible, and thus I believe that the Sun would still burn. I may be wrong though.

 

[lugita15]

Maxwell's equations demand SR. Without SR we would not have a working theory of the EM field.

That's not quite correct, since Maxwell obviously didn't know about SR when he devised his equations. He interpreted c as the speed of light with respect to the aether, and he thought that other reference frames would measure the speed of light differently, depending on the motion of the aether with respect to that frame. Now, as a matter of experimental fact, we know that the speed of light is the same in all inertial frames, and thus Newtonian mechanics is incompatible with Maxwell's equations. But we can easily imagine a world in which the Michelson Morley experiment did not give a null result, in which there was such a thing as aether and Newtonian mechanics was completely correct. Electromagnetism and optics would largely go unchanged. Sure, there would be some differences, on the order of (v/c)^2, but they wouldn't make a huge impact on how the world operated.