Physics and Heisenberg

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Hi.

I am reading Werner Heisenberg’s *Physics and Philosophy/I]. Can anyone explain this to me?:

*“Michelson’s experiment by Morley and Miller in 1904 was the first definite evidence for the impossibility of detecting the **translational motion ***of the earth by optical methods… If the ether is at **rest **with respect to the sun and does **not move **with the earth, then this fast **motion **of the ether with respect to the earth should make itself felt in a change of the velocity of light… If in a certain system of reference the mechanical motion of bodies fulfills the laws of Newtonian mechanics, then this is also true for any other frame of reference which is in uniform nonrotating motion with respect to the first system. Or, in other words, a uniform translational motion of a system does not produce any mechanical effects **at all **and can therefore not be observed by such effects… Since all systems of reference that are in uniform translation motion with respect to each other are equivalent for the description of nature, there is **no meaning **in the statement that there is a substance, the ether, which is at rest in **only one **of these systems… The electrodynamics of moving bodies can be derived at once from the principle of relativity… The laws take the same form in all systems of reference, which are different from each other only by a uniform translational motion; they are invariant against the Lorentz transformation.”

Not one bit of this makes any sense to me. The rest of what I’ve read so far does, but these tidbits don’t, and when put together seem like a mess of nonsense.*
 
If I’m reading this correctly, this is Heisenberg’s refutation of a once-held physics concept known as The Ether. At one point it was believed that nothing could move without a substance to move through. For blood, we need veins, for sound we need air. This concept was extended to light, and the ether was thought up as a way of explaining light’s ability to move without any measurable medium to traverse, as well as it’s ability to move through the apparent emptiness of space.

Heisenberg is basically stating that in order for light to behave the way it does, the “ether” would have to be at rest compared to the sun, but moving with relation to the Earth, which would produce measurable difference in the velocity of light based on our relationship to the sun. Since these differences are not present, we can conclude that the ether is either moving in relation to the sun, or still in relation to us. Neither of these possibilities would allow light to operate in the way it does, in which case neither possibility can be true.

(Note: I’m not a physicist, so I may be misunderstanding something in this. Feel free to correct me physics people!)
 
What does the ether or electrodynamics have to do with relativity? His logic in my quote seems like the opposite of saying there is relativity
 
thinkandmull said:
What does the ether or electrodynamics have to do with relativity? His logic in my quote seems like the opposite of saying there is relativity
Click to expand...
Einstein’s theory of relativity has helped us understanding a lot of things about how physics works. The only reason it’s referenced here is in relation to how it helped derive laws of electrodynamics, which play a part in understanding how light works.

He’s not talking about relativity as in “relativism,” he’s specifically referencing the physical laws of relativity as defined by Einstein.
 
So we’ve seen through science actual examples of relativity in light within outer space?
 
Yeah, in space and here on Earth, at least I think we have. As I said before, I’m not a physicist, so this isn’t really my wheelhouse.
 
Theories of motion have always been of interest to philosophers because they have consequences for the nature of space. The influential papers that Einstein used to get to Special and General Relativity were being made about this time - prior to Einstein we had been using Newton’s theory of mechanics - which had been causing some problems. This looks like an argument for why Newtonian mechanics doesn’t work super-great.

en.wikipedia.org/wiki/Philosophy_of_space_and_time#Leibniz_and_Newton

Leibniz and Newton (through Clarke) argued back and forth about how their observations of motion contributed to their understanding of the nature of space - Newton holding a “substantivalist” or “absolutist” theory while Leibniz endorsed a Cartesian “relational” theory. They both offered thought experiments, too. Look up Newton’s Bucket Experiment and Leibniz’ Static Shift and Kinematic Shift arguments. Also, the Leibniz-Clarke correspondence might be of interest to you.
 
thinkandmull said:
What does the ether or electrodynamics have to do with relativity? His logic in my quote seems like the opposite of saying there is relativity
Click to expand...
Electrodynamics is intimately tied together with relativity; the equations of electrodynamics, Maxwell’s equations (the equations behind electric and magnetic fields), are invariant when a Lorentz transformation is applied to them. This Lorentz transformation is a set of equations that tell you how space and time relate to one another in the situations of special relativity, when things move close to the speed of light. It turns out that the equations behind electrodynamics already have special relativity “built into” them; this is why Einstein’s groundbreaking paper was called On the Electrodynamics of Moving Bodies.
 
thinkandmull said:
Hi.

I am reading Werner Heisenberg’s *Physics and Philosophy/I]. Can anyone explain this to me?:

*“Michelson’s experiment by Morley and Miller in 1904 was the first definite evidence for the impossibility of detecting the **translational motion ****of the earth by optical methods… If the ether is at **rest **with respect to the sun and does **not move **with the earth, then this fast **motion **of the ether with respect to the earth should make itself felt in a change of the velocity of light… If in a certain system of reference the mechanical motion of bodies fulfills the laws of Newtonian mechanics, then this is also true for any other frame of reference which is in uniform nonrotating motion with respect to the first system. Or, in other words, a uniform translational motion of a system does not produce any mechanical effects **at all **and can therefore not be observed by such effects… Since all systems of reference that are in uniform translation motion with respect to each other are equivalent for the description of nature, there is **no meaning **in the statement that there is a substance, the ether, which is at rest in **only one **of these systems… The electrodynamics of moving bodies can be derived at once from the principle of relativity… The laws take the same form in all systems of reference, which are different from each other only by a uniform translational motion; they are invariant against the Lorentz transformation.”

Not one bit of this makes any sense to me. The rest of what I’ve read so far does, but these tidbits don’t, and when put together seem like a mess of nonsense.

I love to see the " local " brains at work on Heisenberg and Einstein :D.

Linus2nd.
Click to expand...
 
thinkandmull said:
What does the ether or electrodynamics have to do with relativity? His logic in my quote seems like the opposite of saying there is relativity
Click to expand...
Michelson-Morley experiments measure the difference in the speed of light coming from perpendicular directions, for instance the direction the Earth is moving and a direction at right-angles to that.

If there was any substance to space (the ether hypothesis) then the Earth would be moving through the substance, and the experiment would find a difference in the speeds, but no difference is found, disproving the ether hypothesis.

This indicates that there is no such thing as a state of absolute rest in electrodynamics (light is an electromagnetic wave). This in turn means that various other measurements are always relative to the velocity of the observer. Einstein takes up the story in his famous paper, On the Electrodynamics of Moving Bodies (the intro. is non-technical).
thinkandmull said:
So we’ve seen through science actual examples of relativity in light within outer space?
Click to expand...
The speed of light in a vacuum is absolutely invariant, which means that space and time cannot be separate but have to be considered together. For example, time passes slightly more slowly in fast-moving satellites compared with the ground, and the GPS system takes that into account or it just wouldn’t work at all. That’s probably the best example of relativity in action.
 
Rhubarb said:
Theories of motion have always been of interest to philosophers because they have consequences for the nature of space. The influential papers that Einstein used to get to Special and General Relativity were being made about this time - prior to Einstein we had been using Newton’s theory of mechanics - which had been causing some problems. This looks like an argument for why Newtonian mechanics doesn’t work super-great.

en.wikipedia.org/wiki/Philosophy_of_space_and_time#Leibniz_and_Newton

Leibniz and Newton (through Clarke) argued back and forth about how their observations of motion contributed to their understanding of the nature of space - Newton holding a “substantivalist” or “absolutist” theory while Leibniz endorsed a Cartesian “relational” theory. They both offered thought experiments, too. Look up Newton’s Bucket Experiment and Leibniz’ Static Shift and Kinematic Shift arguments. Also, the Leibniz-Clarke correspondence might be of interest to you.
Click to expand...
I actually think the Cartesians agreed with Newton
 
Saying that we can’t detect ether doesn’t seem to imply that there can’t be a state of absolute rest.

Also, if gravity slows down time, wouldn’t time go fast at the speed of light?

On the history channel today they said that general relativity has more to do with gravity than with specific relativity. Does this relate to this perplexing paragraph? :

“There are something like ten million million million million million million million million million million million million million million (1 with eighty zeroes after it) particles in the region of the universe that we can observe. Where did they all come from? The answer is that, in quantum theory, particles can be created out of energy in the form of particle/antiparticle pairs. But that just raises the question of where the energy came from. The answer is that the total energy of the universe is exactly zero. The matter in the universe is made out of positive energy. However, the matter is all attracting itself by gravity. Two pieces of matter that are close to each other have less energy than the same two pieces a long way apart, because you have to expend energy
to separate them against the gravitational force that is pulling them together. Thus, in a sense, the gravitational field has negative energy. In the case of a universe that is approximately uniform in space, one can show that this negative gravitational energy exactly cancels the positive energy represented by the matter. So the total energy of the universe is zero.”

– Stephen Hawking, A Brief History of Time
 
Rhubarb said:
Perhaps some did? Descartes’ conception of space was purely relational. Newton had a more realist conception.
Click to expand...
Give me realism every time, three cheers for Newton. Space is real, time is real, gravity is real and never the three shall meet. 🙂

Linus2nd
 
According to relativity theory, space, time, and gravity are all real, and they are interconnected. Gravity acts similar to acceleration. As an object’s speed increases, it’s mass increases (because of the increased kinetic energy), time slows down, and length in the direction of motion shrinks. Hypothetically, if one were to attain the speed of light, your watch would stop, your length would be zero, and you would have infinite mass.

Of course the time slowdown effect as been observed, and as mentioned before is figured into calculations for GPS satellites. It is also observed in cyclotron or hadron collider type of experiments. The effects are negligible at slow speeds, but at near light speeds they would be quite apparent.

Gravity has the same effect as velocity, slowing down time in massive gravitational fields. I suppose that time would pass slower on a massive planet or in a massive star than on earth.
 
One of the things that the movie* Interstellar* got wrong. They were on the shallow water planet where time went by very fast compared to earth and the mother ship because the planet was close to a black hole. To make that serious a time difference the gravity on the shallow water planet and people on it would be tearing them all apart not just making waves in the water. An incredibly fast moving planet would help a little, but that would present other problems in reaching and escaping the planet. For a movie that professed to “get the science right” it took more suspension of disbelief than most. 2001 a Space Odyssey still beats it by multiple degrees of magnitude. Even the special effects are almost as good as today’s movies at least in what they attempted and needed to show.
 
3 things still confuse me:
  1. What does the concept of energy equally matter have to do with relativity
  2. Why cannot there be a state of absolute rest?
  3. If gravity slows down time, wouldn’t time go faster instead of slower at the speed of light?
 
thinkandmull said:
3 things still confuse me:
  1. What does the concept of energy equally matter have to do with relativity
  2. Why cannot there be a state of absolute rest?
  3. If gravity slows down time, wouldn’t time go faster instead of slower at the speed of light?
Click to expand...
As to #3, going faster slows down the passage of time, as does gravity. If there were a group of professional space travelers who consistently traveled at near light speed, they would age much more slowly than their relatives on Earth. They might return from a trip of a few years (to them) to find that centuries have passed on earth. If they spent a great deal of time in a massive gravitational field, the effect would be similar.
 
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