What happens in the restframe with lightsource?

  • Context: Graduate 
  • Thread starter Thread starter faen
  • Start date Start date
Click For Summary
SUMMARY

This discussion centers on the implications of time dilation in special relativity, specifically how observers in different frames of reference perceive the passage of time. The participants analyze a scenario involving two observers, A and B, where A moves close to the speed of light. They conclude that while A perceives B's clock as ticking slower, B sees A's clock as ticking slower as well, illustrating the relativity of simultaneity. The mathematical basis for these observations is rooted in the Lorentz transformations, which define the relationship between time and space in different inertial frames.

PREREQUISITES
  • Understanding of Special Relativity principles
  • Familiarity with Lorentz transformations
  • Knowledge of time dilation and length contraction concepts
  • Basic proficiency in algebra and geometry for solving equations
NEXT STEPS
  • Study the derivation of the Lorentz transformation equations
  • Explore the implications of simultaneity in different inertial frames
  • Investigate the twin paradox and its resolution in special relativity
  • Learn about experimental validations of time dilation, such as muon decay rates
USEFUL FOR

Students and professionals in physics, particularly those studying relativity, as well as educators seeking to clarify concepts of time dilation and frame of reference in special relativity.

  • #61
PAllen said:
Redirect this comment at yourself, where it belongs. ghwellsjr simply asked you how something is measured, and you suggest that is a bad question. It is the most important question in physics - you can' measure it, it isn't physics.
The speed of light hasn't been measured now? Do I really need to get into all that? It seems like it would be something for another forum. Why don't you actually do the math of what I am saying and not just assume that it is wrong without even checking into it? I see why now how this has come to be over a hundred years this has been overlooked.

Okay, a pitcher throws a ball it takes 2s to reach the catcher. He threw the ball at 10m/s. How far is the catcher from the pitcher? (2s)(10m/s) = 20 meters The value for secounds cancels and then you are left with only the unit meters...
 
Physics news on Phys.org
  • #62
John232 said:
I fear this is just going to be way over your head...
It is, but not the way you envision it. :)
 
  • #63
John232 said:
The speed of light hasn't been measured now? Do I really need to get into all that? It seems like it would be something for another forum. Why don't you actually do the math of what I am saying and not just assume that it is wrong without even checking into it? I see why now how this has come to be over a hundred years this has been overlooked.

Okay, a pitcher throws a ball it takes 2s to reach the catcher. He threw the ball at 10m/s. How far is the catcher from the pitcher? (2s)(10m/s) = 20 meters The value for secounds cancels and then you are left with only the unit meters...
When a pitcher throws a ball, you can watch it, you can see when he throws it and you can see when the pitcher catches it. But you are using light which is traveling millions of times faster than the ball to see those two events and so your error in timing is negligible and you don't have to factor out the time it takes for the light to travel from those two events to your eye.

But when Michelson's experiment emits a flash of light, how does he see it to know when that happened? When the light pulse hits the other end of the experiment, how does he see it to know when it arrived? He can only watch it with light, correct? So I need for you to tell me how he can factor out the light travel time from those two events so that he can get a meaningful measurement.
 
  • #64
He could move an entanglement experiment next to the Michealson-Morley experiment and then put an atomic clock on the end of it. Then have a switch linked to both experiments so that it is the same distance to each. When the switch turns on it measures the entangled particle and turns on the Michealson-Morley experiment. The atomic clock would then have a detector to see when the photon reaches it, it then turns on when the other entangled particle changes it's spin from being measured on the other side. The atomic clock stops and read time when the photon reaches the detector. That would be a bunch of trouble just to find that a particle follows d=vt. I thought it should be a given. Or he could just shoot a photon at a piece of material that alters when hit and then time how long it takes it to do it, other way could be a lot of trouble. I thought they already have done this and should be a given. Like when they found the wave properties of light. Why does it take over a hundred years for everyone to know that it was measured to always travel at the same speed? Why would particles travel with anything other than their velocity? Is there some kind of particle velocity I have not heard about? Maybe you could try using my equation to find the velocity in respect to time and get the same answer as the velocity you originally put into it and find that the other equation doesn't. If v=v', then gamma will always cancel so then it doesn't matter if you used the equation for dialated time or not they will reduce to the same equations. Sounds like that should be something you should see wrong with accepted equation.
 
  • #65
I found one link to particle velocity but I don't think it applies here, because I said it was in a vacuum with no resistance. Laws of motion don't even take into account resistance anyways...

http://en.wikipedia.org/wiki/Particle_velocity
 
  • #67
John232 said:
He could move an entanglement experiment next to the Michealson-Morley experiment and then put an atomic clock on the end of it. Then have a switch linked to both experiments so that it is the same distance to each. When the switch turns on it measures the entangled particle and turns on the Michealson-Morley experiment. The atomic clock would then have a detector to see when the photon reaches it, it then turns on when the other entangled particle changes it's spin from being measured on the other side. The atomic clock stops and read time when the photon reaches the detector. That would be a bunch of trouble just to find that a particle follows d=vt. I thought it should be a given.
We are not trying to measure how long it takes a massive particle to travel some distance, that would be like a baseball where you use light, which travels faster than the massive particle to identify when the particle left one end of the experiment and you use light at the other end to identify when the particle arrives there and so that both light signals can be used to start and stop a timer with only a minimal error caused by the ratio of the speed of light to the speed of the particle being less than infinity.
John232 said:
Or he could just shoot a photon at a piece of material that alters when hit and then time how long it takes it to do it, other way could be a lot of trouble.
How do you time how long it takes for the photon to leave the photon gun and arrive at the target? Let's assume that you have at the gun a very fast electronic circuit that produces a pulse precisely when the photon is fired and you have at the target another very fast electronic circuit that produces a pulse precisely when the photon hits the target. The problem is how do you use these two pulses separated in space to start and stop a timer to make your measurement? That's what I need for you to describe for me.
John232 said:
I thought they already have done this and should be a given. Like when they found the wave properties of light. Why does it take over a hundred years for everyone to know that it was measured to always travel at the same speed? Why would particles travel with anything other than their velocity? Is there some kind of particle velocity I have not heard about?
All measurements of the speed of light involve a round-trip for the light so that the two fast electronic circuits that I described earlier are located at the same place, at the photon gun. So the gun shoots a photon and starts the timer. The photon hits a reflector some measured distance away and a photon returns. This photon hits the second detector and stops the timer. Now we can calculate the "average" speed of light. It turns out that this value is a constant equal to c as long as the experiment is inertial. But we cannot know whether it took the same amount of time for the photon to travel from the gun to the reflector as it took for the photon to travel from the reflector back to the detector colocated with the gun.
John232 said:
Maybe you could try using my equation to find the velocity in respect to time and get the same answer as the velocity you originally put into it and find that the other equation doesn't. If v=v', then gamma will always cancel so then it doesn't matter if you used the equation for dialated time or not they will reduce to the same equations. Sounds like that should be something you should see wrong with accepted equation.
What is your equation that works and what is the other equation that doesn't work?

Gamma was proposed by scientists prior to Einstein as a way to explain how the measurement of light would always yield the same answer even though they thought light was only traveling at c in a fixed ether medium. So if the photon travels at a fixed speed with respect to the ether, that could cause the time for the photon to travel from the gun to the reflector to be shorter than the return trip or vice versa.
 
  • #68
John232 said:
I found one link to particle velocity but I don't think it applies here, because I said it was in a vacuum with no resistance. Laws of motion don't even take into account resistance anyways...

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

John232 said:
http://en.wikipedia.org/wiki/Particle_acceleration

Here is another link, do these equations look familiar?
These two wiki articles are about massive paritlcles and don't apply to the one-way speed of light. You should instead look up and study the wiki article called "One way speed of light".
 
  • #69
Einstein found the two way speed of light just by adding the times it reached both clocks and dividing it by two, in no way does this imply that the speed of light in two directions is different. The Michealson-Morley experiment proves that the two way speed of light is the same as the one way even in different directions. In no way does the Einstein synhronisation imply that velocity is different. I still don't get why you have a problem with this. Pretend your Isaac Newton, you measure a ball to be shot across the room. You find that it always travels a distance vt. Now you check every other distance across the room that it could travel and you find that the distance equals vt in every case. So then you know that d=vt. Now say the photon is the same ball Newton was measuring. You measure the photon to travel the same distance according to d=vt, and then do this at different distances. You find it always travels at a constant speed no matter what distance it traveled, so then you know that d=vt is true. How could you have some other equation where light comes to the same speed and the distance it travles is not inversely related to that velocity? If it traveled at different speeds in different directions then the speed of light wouldn't be constant and Michealson-Morley would have had a whole different story. I think you should look into the experiment into further detail and not mind any mention of aether...

It also says on the two way speed of light that an equation that describes this is the lorentz transformations, well what I did was in effect solving for my own lorentz transformation. But the main difference being that my velocity is different so that the two way speed of light is equal to the one way speed of light. That was actually found by the experiment it comes from. Like I said before v doesn't equal the length contraction equation divided by the time dilation equation you can find this by putting a velcoity in both equations and then solving for length and time then useing that to find the velocity, it doesn't come out to be the same, but in my theory it does. So then my theory it says the two way speed of light is the same.
 
Last edited:
  • #70
John232 said:
Einstein found the two way speed of light just by adding the times it reached both clocks and dividing it by two, in no way does this imply that the speed of light in two directions is different.
Can you show me a reputable reference for this?
John232 said:
The Michealson-Morley experiment proves that the two way speed of light is the same as the one way even in different directions.
Can you show me a reputable reference for this?
John232 said:
In no way does the Einstein synhronisation imply that velocity is different. I still don't get why you have a problem with this. Pretend your Isaac Newton, you measure a ball to be shot across the room. You find that it always travels a distance v/t. Now you check every other distance across the room that it could travel and you find that the distance equals v/t in every case. So then you know that d=v/t. Now say the photon is the same ball Newton was measuring. You measure the photon to travel the same distance according to d=vt, and then do this at different distances. You find it always travels at a constant speed no matter what distance it traveled, so then you know that d=vt is true. How could you have some other equation where light comes to the same speed and the distance it travles is not inversely related to that velocity? If it traveled at different speeds in different directions then the speed of light wouldn't be constant and Michealson-Morley would have had a whole different story. I think you should look into the experiment into further detail and not mind any mention of aether...

It also says on the two way speed of light that an equation that describes this is the lorentz transformations, well what I did was in effect solving for my own lorentz transformation. But the main difference being that my velocity is different so that the two way speed of light is equal to the one way speed of light. That was actually found by the experiment it comes from. Like I said before v doesn't equal the length contraction equation divided by the time dilation equation you can find this by putting a velcoity in both equations and then solving for length and time then useing that to find the velocity, it doesn't come out to be the same, but in my theory it does. So then my theory it says the two way speed of light is the same.
Until you show me the two references I asked for, nothing else in your post matters.
 
  • #71
I think even if I did give you references to that it wouldn't even matter, I am done talking to you. Google it and find out for yourself. How you question the michealson-morley experiment as not proving that light travels the same speed when sent into different directions is just mind boggling.
 
  • #72
John232 said:
I think even if I did give you references to that it wouldn't even matter, I am done talking to you. Google it and find out for yourself. How you question the michealson-morley experiment as not proving that light travels the same speed when sent into different directions is just mind boggling.
MMX concluded that the two-way speed of light is the same in all directions. It said nothing about the one-way speed of light. The scientists of the day, especially Lorentz concluded that the length of the arm traveling along the direction of the ether was contracted which gave the illusion that the two-way speed of light was the same as in the direction perpendicular to the direction of motion through the ether.

It was Einstein who came along later that postulated that in any state of inertial motion, you could define the one-way speed of light to be equal to the measured two-way speed of light, in other words, the light is defined to take the same amount of time to propagate from the single clock to the reflector as it takes to come back from the reflector to the clock. Einstein never started with two clocks located at either end of the experiment and measured the two times for the light to travel and then add them together to get the two-way speed of light. You have it backwards.

You have a lot to learn and it's a shame you want to leave in this state of ignorance. I hope you will reconsider. I've invested many hours of my time to help you and I'd hate to see it go to waste.
 
  • #73
Finally, you state that you actually know something about physics. So why ask me, if you already know? Is there a point to all this? If you can prove that you can't measure the distance a photon has traveled, then you would have proved that relativity itself is wrong because it does the same thing. So then what makes you think you can disprove 100 years of accepted physics? I find it upsetting to work hard in thinking about how to solve many of the problems faced in physics and then find an answer, just to have someone insult me the whole time about it. I tried as hard as I could to explain it well enough to make someone else understand it, but apperently it takes two geniuses to create new science, one to figure it out and another to say yes that is right.

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

He finds that you can add time 1 and time two and multiply it by one half. This only takes the average of the two times. Like you would find the avearge velocity in Newtons equations, for this to be true the velocity would have had to have been the same both ways. It is just a lot ado about nothing. It would be like telling Isaac Newton that his theory's of motion didn't mean anything because he can't prove that it works the same both ways...
According to Albert Einstein's prescription from 1905, a light signal is sent at time from clock 1 to clock 2 and immediately back, e.g. by means of a mirror. Its arrival time back at clock 1 is . This synchronisation convention sets clock 2 so that the time of signal reflection is .[1]
 
  • #74
Come to think of it I can believe Einstein had this same discussion...

Maybe it could mean something...
 
  • #75
Maybe they had to have this same discussion because he didn't get the same value for velocity!
 
  • #76
I think the only way someone could depict a more accurate theory using this method of algebra, would be to consider the coordinate system of a photon traveling at the speed of light. But, in the equations length and time would be contracted to zero. In another coordinate frame their would exist real distance. The problem is that these two coordinate systems do not agree with each other. In one the triangle would have a side with the length of zero (it would no longer form a triangle), and in the other it would have some other real value. Then you would have to find the relation between these two system so that in some way they agree on the speed of light, even though one of those planes was fully contracted. I don't think there is a way it can be done mathematically as we know it, but it may be possible to describe the length along with quantum uncertainty in some other way.
 
Last edited:
  • #77
John232 said:
Finally, you state that you actually know something about physics. So why ask me, if you already know? Is there a point to all this?
The point of these forums is to teach people who want to learn physics. I didn't make that rule but I follow it.
John232 said:
If you can prove that you can't measure the distance a photon has traveled, then you would have proved that relativity itself is wrong because it does the same thing.
I never said you couldn't measure the distance a photon travels, where'd you get that idea? I just said in post #67:
ghwellsjr said:
All measurements of the speed of light involve a round-trip for the light so that the two fast electronic circuits that I described earlier are located at the same place, at the photon gun. So the gun shoots a photon and starts the timer. The photon hits a reflector some measured distance away and a photon returns. This photon hits the second detector and stops the timer. Now we can calculate the "average" speed of light. It turns out that this value is a constant equal to c as long as the experiment is inertial. But we cannot know whether it took the same amount of time for the photon to travel from the gun to the reflector as it took for the photon to travel from the reflector back to the detector colocated with the gun.
John232 said:
So then what makes you think you can disprove 100 years of accepted physics? I find it upsetting to work hard in thinking about how to solve many of the problems faced in physics and then find an answer, just to have someone insult me the whole time about it. I tried as hard as I could to explain it well enough to make someone else understand it, but apperently it takes two geniuses to create new science, one to figure it out and another to say yes that is right.
Huh? Why do you think I'm trying to disprove 100 years of accepted physics? I'm trying to help you learn it. You're the one that wants to publish your own theory of Special Relativity, not me. I'm trying to dissuade you from that endeavor. Einstein is pretty much accepted as a genius by a great many other people that I would also consider to geniuses. What other geniuses are you talking about here? Do you see yourself in the role of a genius creating new science? Is that why you want to publish your own theory of Special Relativity?
John232 said:
Yes, the wiki article does not say that Einstein is measuring the time it takes for the light to go from clock 1 to clock 2 as you have been claiming. Rather it says τ1 is the time on clock 1 at the start of the light pulse and τ2 is the time on the same clock 1, not clock 2, after it has been reflected back, in other words, he is measuring the round-trip time of the light pulse. He also records the time on clock 2 when the light was reflected. Then he calculates the average of those two times measured on clock 1 and sees how far off the recorded time on clock 2 was from the average. He makes an adjustment to clock 2 (this is where he sets the time on clock 2). Now clock 2 should be synchronized to clock 1. If he repeats the experiment and if he did everything right the first time, then the second time, clock 2 should display the average of the two times on clock1 and he can now say, by definition--not by measurement, that the time it takes for light to go from clock 1 to clock 2 equals the time it takes for the light to go from clock 2 to clock 1. You should not think of the process of synchronization as a way to discover the truth about the speed of light but rather as a way of creating truth about the speed of light.
John232 said:
He finds that you can add time 1 and time two and multiply it by one half. This only takes the average of the two times. Like you would find the avearge velocity in Newtons equations, for this to be true the velocity would have had to have been the same both ways. It is just a lot ado about nothing.
It's not much ado about nothing. It's the foundation of Special Relativity and without Einstein's insight into the fact that until and unless you create the meaning of the time on clock 2, it can have no meaning. After he makes that definition, then you can conclude that the light takes the same amount of time to go both directions but only in that one frame of reference for which the definition holds true. In another frame of reference with its own application of the definition, the time it takes for light to get from clock 1 to clock 2 is not the same as it is for the light to get back from clock 2 to clock 1.
John232 said:
It would be like telling Isaac Newton that his theory's of motion didn't mean anything because he can't prove that it works the same both ways...
According to Albert Einstein's prescription from 1905, a light signal is sent at time from clock 1 to clock 2 and immediately back, e.g. by means of a mirror. Its arrival time back at clock 1 is . This synchronisation convention sets clock 2 so that the time of signal reflection is .[1]
This is incomplete so I don't know what you are saying here.

But the bottom line is that anytime you want to measure how long it takes for light to go from point A to point B with two different clocks, you have to first synchronize those two clocks via round-trip light signals that are assumed to travel at the same speed in both directions and therefore take the same time in both directions, then, of course, you will "measure" the speed of light to be the same in both directions, how could it be otherwise?

This whole discussion is a result of your rejection of the wikipedia article on time dilation in its explanation of a light clock based on Einstein's definition of remote time in a Frame of Reference and the constant speed of light, and your insistence that there was a better way in which you could measure the one-way speed of light apart from previously defining it.
 
  • #78
I read a book a long time ago, don't recal what one it was, but it said that the writer new about the instance where Einstein's theory was rejected by a particle physisist and the theory didn't work out with what they found in the experiment. They then had an argument about it because there was no clear way to define how someone could know that Newtonian physics still applied to quantum mechanics. It really started to make me wonder if you where that same guy because of the insidious questions about Newtonian physics. If so I apoligize if you ended up getting in a argument with both of us. But, i think he may have passed away, don't remember exactly who that was.

I guess the wiki claims that any type of lorentz transform theory would not follow the two way speed of light, but I think mine can because I derived gamma differently. The equations for velocity would not change if the value's canceled so in effect the equations that deal with velocity could stay the same, but then someone could calculate how long a particle lived by finding the amount of time dilation it experienced while under acceleration. Also the effects of gravity are negligible so it is not included in my theory yet, also it would work accurately for sure for any experiment done on Earth since the conditions of the observer would be guarnteed to be the same as the Michealson-Morley experiment with the case that an observer traveling relative to the MMX would detect the outcome to come out differently. I also think that the relation itself just does not exist anymore for an object traveling at the speed of light, since the triangle itself no longer exist. So if the photons frame of reference is in no way related to an observer at rest, then any value we find in our frame would not affect any value in the photons frame.
 
  • #79
John232 said:
the effects of gravity are negligible so it is not included in my theory yet
Personal theories are not permitted topics on Physics Forums.

John232 said:
So if the photons frame of reference
Photons do not have a frame of reference:
https://www.physicsforums.com/showthread.php?t=511170
 
  • #80
John232 said:
My simple proof.

An observer in motion observers a photon to travel straight out in a line a distance cΔt'. An observer at rest measures the photon to travel out at an angle along with the objects direction of motion cΔt.
...
So then, the distance traveled by the object in constant acceleration can be replaced with Δt(vi+vo)/2.
...
(cΔt')^2+(Δt(vi+vo)/2)^2 = (cΔt)^2 Pythagorean Theorem
This assumes that the postulates of relativity apply to non-inertial frames, which is wrong.
 
  • #81
DaleSpam said:
This assumes that the postulates of relativity apply to non-inertial frames, which is wrong.

I don't think it does. A non-inertial frame would not have a length (vt), so then instead of being able to insert c as the velocity, you would have to say that the triangle does not exist so that you can't obtain an answer as zero for the formula to work. So then going back to the inital question of does the distance light travel equal its velocity times time would be yes, because of the nature of the algebra itself. So then Δt=t√(1-(vi+vo)/4c^2) would only be true if vi≠c and vo≠c. That agrees with the intial assumption that the distance the photon travled is the same of the Newtonian equation d=vt.

I will stop here, I guess i would have to ask where I could be redirected to where these topics could be discussed?
 
  • #82
How does a theory become accepted by physics forums?
 
  • #83
John232 said:
you would have to say that the triangle does not exist
I wouldn't say that it doesn't exist, just that light doesn't travel in a straight line in terms of non inertial coordinates.
 
  • #84
John232 said:
How does a theory become accepted by physics forums?
Read the rules link at the top of each page. It has to be published in the mainstream scientific literature.
 
  • #85
DaleSpam said:
I wouldn't say that it doesn't exist, just that light doesn't travel in a straight line in terms of non inertial coordinates.

So then wouldn't that mean that the MMX wasn't in a non inertial frame, but was actually in an inertial frame because the outcome of the experiment showed that light beams sent in two different directions ended up haveing their wavelengths match up as though one beam had not traveled a longer distance than the other when they split up?

The mainstream literature I read on it suggest that the experiment actually was in a non-inertial frame and that the beam did travel in a straight line, and that Einstein himself didn't base his theory on that experiment, but the experiment itself is always mentioned in physics literature.
 
Last edited:
  • #86
John232 said:
So then wouldn't that mean that the MMX wasn't in a non inertial frame, but was actually in an inertial frame because the outcome of the experiment showed that light beams sent in two different directions ended up haveing their wavelengths match up as though one beam had not traveled a longer distance than the other when they split up?
The experiment was not in an inertial frame according to general relativity, but the apparatus was not sensitive to the gravitational effects. You can calculate the general relativistic corrections if desired, but you will see that they are far smaller than the noise.
 
  • #87
How could MMX not be in a inertial frame according to general relativity if there is acceleration of the rotation/revolutions of Earth? Putting gravity aside, you would think that since the theory predicts that a photon would propagate at a curve if the experiment was only accelerating at a different velocity. So how then can MMX get the result it did and still be in accordence with the general theory?
 
  • #88
John232 said:
So how then can MMX get the result it did and still be in accordence with the general theory?
As I said before, it is simply not sensitive to general relativistic effects.
 
  • #89
DaleSpam said:
As I said before, it is simply not sensitive to general relativistic effects.

Then why did MMX make the claim that they could calculate the acceleration relative to the aether when it did not accelerate enough to find the difference of acceleration according to GR? Seems to me that they would have had to have found an arc in the beam that was the same as GR predicted in order for the theory to be correct. Then they would have had to say that light bends when Earth accelerates through the aether. But, this is not what happened. I think this is why GR is not compatable with quantum mechanics, because in this sense it is just wrong. The beam of light isn't effected the same way from acceleration as it is affected by gravity.
 
  • #90
John232 said:
Then why did MMX make the claim that they could calculate the acceleration relative to the aether [..]
That's not exact, they hoped to be able to detect the speed of the Earth. You can read it here:
http://en.wikisource.org/wiki/Author:Albert_Abraham_Michelson
Apparently you are making statements about his papers of 1881 and 1887.
 

Similar threads

  • · Replies 12 ·
Replies
12
Views
2K
  • · Replies 33 ·
2
Replies
33
Views
2K
  • · Replies 87 ·
3
Replies
87
Views
5K
  • · Replies 15 ·
Replies
15
Views
2K
  • · Replies 16 ·
Replies
16
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 20 ·
Replies
20
Views
2K
  • · Replies 6 ·
Replies
6
Views
1K
  • · Replies 10 ·
Replies
10
Views
2K
  • · Replies 167 ·
6
Replies
167
Views
8K