Naked Science Forum
On the Lighter Side => New Theories => Topic started by: Petrochemicals on 12/10/2017 21:44:58
-
If light cannot exeed 'C' in a vacuum, and has a constant velocity that is independant and absolute, it must be possible to create a speed gun to measure an Absolute velocity ?
If you had a sphere with a vaccuum within, and at the centre a light source. At the periferies of the sphere detecting the light are sensors. The sensors read back to a display
You fire the gun
Would these sensors detect at which direction, and at which velocity you where going. Last time I got as far as relativity ie this being different time for different observers. You fire the gun (in your hand) and the readout says you are stationary ? Or would it work ? The mickelson morley says it would have no effect, but the rebka -pound disagrees.
Someone who observed you fire the gun as you passed by, reads the display ? What then. The clock is in the gun or do we observe a paradox ?
-
Admittedly, I'm not sure I completely understand the set-up. Does the gun make a laser-like beam of light that lands on only one point of the sphere, or does it emit light in all directions? If the light goes in all directions, then the sensors could tell from the relative values of redshift and blueshift at different points along the sphere's internal surface what direction and speed the gun was moving in.
If It was only hitting one particular spot on the wall, you could at least tell the direction that the gun was fired. Redshift measurement would only work in that case if you knew the frequency of the light that the gun was designed to emit, and that would only work if the gun wasn't moving perpendicular to the sensor that received the light and if you knew the angle that the gun was fired from. Of course, if it was moving perpendicular to the sensor, then other sensors could pick it up and tell by the relative timing of received signals how fast the gun was moving. The speed of light doesn't have to change for you to do any of these things.
All of this relative to the sphere itself, that is. Other observers in different reference frames will get different values for the gun's speed.
-
The mickelson morley says it would have no effect, but the rebka -pound disagrees.
I’m also having problems understanding the set up. And why pound Rebka should disagree with MM.
Could you explain please?
-
Yep a lightsource in a sphere emmitting light in all directions, with sensors all the way around the sphere.
The PR experiment would say that the red shift/blueshift should be be measurable and your absolute velocity and absolute vector would be apparent.
The MM experiment though found no lag in the aether, that wasnt there. But by firing light beams in two seperate directions 90 DEG to each other this would have replicated the process of light at different directions and aether or not, should have found some discrepancy in the light at the reciever. One light beam has a long parralell and short perpendicular to the reciever, the other has the opposite. The experiment has been repeted manytimes with different orientations, but no differences in speed have been detected otherwise they would have been said to be evidence of the aether.
Something has to happen as if two light beams pass and you are riding on one of them, the other is not going 2C.
-
Problem is that there is no such thing as absolute velocity.
Velocity is the rate of change of a distance vector. There being no absolute origin, any velocity is relative to some arbitrary origin.
-
The PR experiment would say that the red shift/blueshift should be be measurable and your absolute velocity and absolute vector would be apparent.
In that particular reference frame. In other reference frames, the redshift would be measured as having a different value.
Something has to happen as if two light beams pass and you are riding on one of them, the other is not going 2C.
Length contraction and time dilation.
-
The speed of light is the fastest velocity possible and yet cannot be reached by massive objects. This makes it the perfect yardstick. At a particular instant a photon is at position x. At a later time t it is at x + dx. This will not vary in a vacuum in the absence of other forces such as gravity. So that spacetime intervals can map to the path of photons if considering special relativity. All other velocities are relative and influenced by time dilation depending upon the frame of the observer. This makes it extremely difficult to make any determination of the one way speed of light. It will always be observer dependent.
-
Problem is that there is no such thing as absolute velocity.
Velocity is the rate of change of a distance vector. There being no absolute origin, any velocity is relative to some arbitrary origin.
You are travelling at 0.5c and you turn on your headlights, the light travels at 0.5c ? Light is not dependant on origin is it ?The speed of light is the fastest velocity possible and yet cannot be reached by massive objects. This makes it the perfect yardstick. At a particular instant a photon is at position x. At a later time t it is at x + dx. This will not vary in a vacuum in the absence of other forces such as gravity.
Thats the idea, only influenced by your velocity, and the gravitational field, which i hadnt taken into account !
The PR experiment would say that the red shift/blueshift should be be measurable and your absolute velocity and absolute vector would be apparent.
In that particular reference frame. In other reference frames, the redshift would be measured as having a different value.
Something has to happen as if two light beams pass and you are riding on one of them, the other is not going 2C.
Length contraction and time dilation.
But the point is that within the sphere with all going at equal velocity the red shift blue shift from the emitter should be apparrent. I got to time dilation last time. The observer is the readout, so if you who are travelling with the sphere and your best frien d who is observing your progress read the readout, you both observe the same reading.
Would forward momentum dilate time, so as to balance out the fore and aft readings ?
-
But the point is that within the sphere with all going at equal velocity the red shift blue shift from the emitter should be apparrent. I got to time dilation last time. The observer is the readout, so if you who are travelling with the sphere and your best frien d who is observing your progress read the readout, you both observe the same reading.
If your friend was moving by the sphere and could somehow see the readout on the sphere's sensors, they would indeed see the same numbers as a person who is on the sphere. If they performed their own measurements of the redshift of the light inside the sphere, in their own reference frame, they would get different numbers. There's nothing strange about it. The same thing would happen if you passed by a police car that was using a radar gun to measure the speed of another car, You'd see the same numbers on the cop's radar as the cop would. If you had your own radar gun, however, you'd get a different number because the redshift values would be different for you.
-
Ok so you both observe the reading, no paradoxes or anything. The readings in the sphere measure identical fore and aft ? As the sphere and you are in there own timeframe ? So if you turn your headlights on at 0.5c you see light as normal at 1c but your friend sees light al 0.5c as your friend is not at the same velocity and therefore time dilation.
That must mean the ad you are in your own clock and time dilation and light infront of you and behind you appears the same, you would have to have two time dilations for the light to appear constant in both directions, in reference to the observer on the ground, who is observing the constant C .
-
Petrochemicals,
I'm just trying to check that I understand the setup correctly.
You have a flash bulb in the middle of a sphere.The surface of the sphere has detectors on the inside.
If it's not moving, the flash from the bulb reaches the detectors at the same time.
The ideas is that, if the system is moving, the light will have further to travel to the "back" of the sphere than to the "front".
Is that what you mean?
-
Petrochemicals,
I'm just trying to check that I understand the setup correctly.
You have a flash bulb in the middle of a sphere.The surface of the sphere has detectors on the inside.
If it's not moving, the flash from the bulb reaches the detectors at the same time.
The ideas is that, if the system is moving, the light will have further to travel to the "back" of the sphere than to the "front".
Is that what you mean?
Yep thats what i mean. Seemed so simple when i wrote it down.
-
Yep a lightsource in a sphere emmitting light in all directions, with sensors all the way around the sphere.
The PR experiment would say that the red shift/blueshift should be be measurable and your absolute velocity and absolute vector would be apparent.
Ok, assuming you + light gun and sphere are moving together.
PR detects a red/blueshift if there is either a difference in gravitational potential or, by equivalence, an acceleration. If your sphere is accelerating you would feel a force as well as detecting a PR shift. If the sphere is constant velocity you won’t detect anything.
At constant velocity you will only detect a shift if the sphere wall is moving relative to you/gun.
PR does not disagree with MM, they are measuring different things.
Ok so you both observe the reading, no paradoxes or anything. The readings in the sphere measure identical fore and aft ? As the sphere and you are in there own timeframe ? So if you turn your headlights on at 0.5c you see light as normal at 1c but your friend sees light al 0.5c as your friend is not at the same velocity and therefore time dilation.
No, your friend measures the light as 1c, not 0.5c. Maxwell’s equations.
-
Ok, assuming you + light gun and sphere are moving together.
PR detects a red/blueshift if there is either a difference in gravitational potential or, by equivalence, an acceleration. If your sphere is accelerating you would feel a force as well as detecting a PR shift. If the sphere is constant velocity you won’t detect anything.
At constant velocity you will only detect a shift if the sphere wall is moving relative to you/gun.
PR does not disagree with MM, they are measuring different things.
ok i think i got it, the pr experiment is due to the acceleration of gravity and thus increacing velocity creating a doppler effect as you decend toward the earth surface, mot because of a doppler effect due to increaced speed in the light used, so at the constant velocity there is no red shift. So if a galaxy is departing from us at a constant velocity, no red shift is experienced
No, your friend measures the light as 1c, not 0.5c. Maxwell’s equations.
Ok to the rear your friend measure the light at 1c and forward he measures the light at 1c, the constant C. Your friend as he sees you move does not/would not see a doppler efect in the light due to the emmitter being in motion, he sees the light 1c relative to the emmitter.
You however also see the light fore and aft at 1c completley independant of your friend, due to time dilation due to your clock. Does that mean you do not need relativity as you both see the light ?
-
Ok to the rear your friend measure the light at 1c and forward he measures the light at 1c, the constant C. Your friend as he sees you move does not/would not see a doppler efect in the light due to the emmitter being in motion, he sees the light 1c relative to the emmitter.
Your friend sees a doppler effect if he is moving towards/away the gun because he is crossing the wave crests more/less frequently than if the gun were stationary relative.
You however also see the light fore and aft at 1c completley independant of your friend, due to time dilation due to your clock. Does that mean you do not need relativity as you both see the light ?
Its somewhat the other way round. Light is constant because Maxwell’s equations are the result of 4 very important physical laws covering electricity and magnetism and we have experiments that show that these laws are independent of the inertial frame. Time dilation and length contraction are a result of this - independence of the laws and the constant speed of light - rather than the cause. So we need relativity to explain why our measurements appear to be, at first sight, unbelievable.
Hope that helps.
-
The speed of light is the same in all references. To get an absolute speed, we need to measure with respect to the speed of light since this is a standard for all references. We make the speed of light become the zero reference. Relative reference only applies to two or more inertial references. Relative reference has no meaning at the speed of light.
Here is an analogy. Say we have a mountain coming out of the sea. Sea level is the same place for everyone no matter where you stand on the mountain. As we move up the mountain, the potential with sea level increases and will define an absolute hierarchy.
Relative to two people standing at different places on the mountain (ignore sea level), you can get the same potential difference for a large number of scenarios. It becomes relative. If one person is at the bottom and one person is half way up, this has the same potential as one person half way and one at the top. If we have the half way person and the top person both step down, one step, this is still the same potential. You cannot get an absolute reference on the mountain. You need to have one person always at sea level or C-level, zero potential separate from the mountain.
We live on the earth in an inertial reference. We still use the very ancient earth centric thinking since this is how the natural brain will process data; visual. Instead you need to think in terms of standing at C-level with the mind's eye, Then we can find the center of the universe with respect to C and absolute zero velocity.
When there was only the primordial atom, we only had one inertial reference and the speed of light reference. There was no such thing, yet, as relative reference, until the BB. The primordial atom set the maximum potential with C. It was the top of the mountain that was sticking out of the C-level reference. The BB lowered this potential. The universe is heading down the mountain.
-
Your friend sees a doppler effect if he is moving towards/away the gun because he is crossing the wave crests more/less frequently than if the gun were stationary relative.
So not acceleration ? The pr experiment was used to measure doppler effect in light under the influence of gravity wasnt it ? The light frequencies extended due to increaced speed because of gravity ?
-
The speed of light is the same in all references. To get an absolute speed, we need to measure with respect to the speed of light since this is a standard for all references. We make the speed of light become the zero reference. Relative reference only applies to two or more inertial references. Relative reference has no meaning at the speed of light.
Thats pretty much what I thought. And you do seem to agree.
By the way this mountain analogy, youve not been reading about Numenor in the silmarillion ?
-
So not acceleration ?
yes, my reply was for contstant speed scenario, but also for acceleration, however, the shift would vary as speed increased.
To get an absolute speed, we need to measure with respect to the speed of light since this is a standard for all references. We make the speed of light become the zero reference.
As this is new theories, please explain how you find your absolute speed by measuring wrt light?
[/quote]
-
In the 2D analogy, a moving circle is length contracted so that observer A in the center receives simultaneous reflections from a signal emitted from the center.
In the 3D equivalent, the sphere becomes an ellipsoid with the same results.
The moving inertial frame behaves like a rest frame.
The clock in the radar gun will be affected by time dilation. The device will sense an earlier time and calculate a shorter distance, just as a human would, resulting in the same relative speed for the target.
-
In the 2D analogy, a moving circle is length contracted so that observer A in the center receives simultaneous reflections from a signal emitted from the center.
In the 3D equivalent, the sphere becomes an ellipsoid with the same results.
The moving inertial frame behaves like a rest frame.
The clock in the radar gun will be affected by time dilation. The device will sense an earlier time and calculate a shorter distance, just as a human would, resulting in the same relative speed for the target.
So how about the ligth to the rear of you, this must mean 2 clocks for you (fore and aft to enable increaced shift and decreaced shift as you look at the light goin in the direction of your travel, and light at opposite to the direction of your travel), and one for your friend on the ground
. I know about the analogy of the rocket ship with you in it and your friend on the ground, both witnessing light at the same rate, yet you are travelling at 0.5c, thus time dilation, but how do you rectify the two clocks paradox depending on which way you look ? Esentialy if you experience time at a different rates and thuw c or light is constant, how do you rectify which time dilation you use depending on whether you are travelling along with the light or at an opposed 180 direction?
Edit.
So would this be a parabolic ellipsoid of some sort, contracted for half its mass/length, and elongated the other . That would add up.
-
yes, my reply was for contstant speed scenario, but also for acceleration, however, the shift would vary as speed increased.
Ok because the e mmitter and reciever are both travelling at the same constant velocity, the frequencies of waves as they strike the reciever are exactly the same, only difference is the duration and lengthof there passage inbetween emmitter and reciever, as one reciever is catching up to the waves, and one reciever is travelling away from the waves, in both cases the waves have been emmitted at intervals that are equal to the recievers collection of the waves. Standard logic no need for relativity there. No clock no redshift
Your friend who if could observe the same light as was emmitted by the emmitter travelling at 0.5c compared to him, should see some significant redshiftof the light, in like with the pr experiment d3pending whether the emmitter had pased him or not. No clock.
So the idea of relativity and you observing a different clock is uneeded as you are travelling along with the emmitter .
So if a pulse was fired within the gun sphere it would detect your absolute velocity if we had the technology refined enough , magnetism and gravity allowed for (touch complicated) and the difference between our velocities and c (0.000000001%) due to light pulse arriving at different times in the emmitter.
Blue shift of light is only if you are at closing/opening speed, relativity is only if there are two frames relative to the emmitter ?
Edited from the original
Your friend who if could observe the same light as was emmitted by the emmitter travelling at 0.5c compared to him, should see some significant redshiftof the light, in like with the pr experiment d3pending whether the emmitter had pased him or not. No clock no redshift.[\quote]
-
how do you rectify which time dilation you use depending on whether you are travelling along with the light or at an opposed 180 direction?
You don't. Time dilation has nothing to do with whether you are travelling with or against a light beam. It only has to do with the relative speed of you (with the emitter) and your friend.
Your friend who if could observe the same light as was emmitted by the emmitter travelling at 0.5c compared to him, should see some significant redshiftof the light, in like with the pr experiment d3pending whether the emmitter had pased him or not. No clock.
I'm not at all sure why you are mentioning PR, in that experiment there is no relative motion only a gravitational potential difference. PR was not a doppler shift.
Also, why do you say “no clock”? If your friend is travelling relative to the emitter then the emitter clock and your friend’s clock will differ.
So the idea of relativity and you observing a different clock is uneeded as you are travelling along with the emmitter .
But your friend isn't, s/he is moving relative to you so you each have differing clocks.
So if a pulse was fired within the gun sphere it would detect your absolute velocity if we had the technology refined enough , magnetism and gravity allowed for (touch complicated) and the difference between our velocities and c (0.000000001%) due to light pulse arriving at different times in the emmitter.
No, it won't tell you anything about absolute velocity, all you can work out is your relative velocities.
relativity is only if there are two frames relative to the emmitter ?
But there are 2 frames relative to the emitter, you (even though you might not think you are moving in space) and your friend. All you can ever work out is the speed of yourself relative to your friend and to the emitter. The sphere and emitter are not fixed to any absolute reference.
-
You don't. Time dilation has nothing to do with whether you are travelling with or against a light beam. It only has to do with the relative speed of you (with the emitter) and your friend.
well this is to do with the way of understanding it of relativity. Answered puppypowers thing on oval elliptical legngthing etc, answer this too. If you are travelling toward an ioncoming light beam your "clock " speeds up, showing you no doppler ? As you pass the beam you travel at the same clock speed, but to now have the light behind you with no blue shift, your clock must slow down, in a paradoxical way. If the elliptical time dilation happens it must mean a massive compression infront of you and a massive lengthening behind you giving you just the one clock ? I have a feeling the sphere will be round to you and your time frame but elliptical and lengthened to the observer? Thats the answer is it?
I'm not at all sure why you are mentioning PR, in that experiment there is no relative motion only a gravitational potential difference. PR was not a doppler shift.
i thought pr was to test wether gravity gave a doppler effect to light, ie travelled faster, and the speaker movement rectifying this ? It is to do with if you meet light oncoming and being able to tell your position. Incedentally why did they observe doppler shifts when increaced wavelength was met with slower clocks. Special relativity ?
Also, why do you say “no clock”? If your friend is travelling relative to the emitter then the emitter clock and your friend’s clock will differ.
/
as it is a lightsource, he can tell the doppler shift, the light source is moving and he can see the source ?
But your friend isn't, s/he is moving relative to you so you each have differing clocks.
is moving relative to the light source, in the way andromeda is moving away from us
No, it won't tell you anything about absolute velocity, all you can work out is your relative velocities.
relative velocity compared to the absolute C that is independant of gravity ?
But there are 2 frames relative to the emitter, you (even though you might not think you are moving in space) and your friend. All you can ever work out is the speed of yourself relative to your friend and to the emitter. The sphere and emitter are not fixed to any absolute reference.
they are fixed at set distances to each other, and whilst you stay fixed to them you are in there frame ? So one pulse, and measure the strike intervals on the sphere you measure the absolute velocity of the frame ? As c is absolute constant it would be your referance is the theory. The friend though will only be able to work out the speed of himself and the emmitter, as he cannot have the second reference. The theory.
-
well this is to do with the way of understanding it of relativity.
You asked why a light gun cannot measure absolute velocity and I have answered. If you wish to ignore that and develop your own theory, that's ok in this section, but it is worth baseing your theory on experimental facts rather than misinterpretations, so I'll answer your last set of questions.
If you are travelling toward an ioncoming light beam your "clock " speeds up, showing you no doppler ?
No, you will always see doppler if you are moving relative to the light source. At low speeds ordinary doppler dominates but at relativistic speeds you need to add a correction.
i thought pr was to test wether gravity gave a doppler effect to light, ie travelled faster, and the speaker movement rectifying this ?
No, it is not a doppler effect because if the emitter and receiver are not moving, ie fixed at top and bottom of the tower, then a shift still occurs - due to the difference between the clocks at top and bottom of tower. The has been verified using atomic clocks.
The loudspeaker was used to generate a doppler shift to cancel out the gravitational shift and provide a measurement of it's value.
It is to do with if you meet light oncoming and being able to tell your position.
No, you cannot tell your position, only the difference between the gravitational potential - you can get the same difference in potential at different positions.
Incedentally why did they observe doppler shifts when increaced wavelength was met with slower clocks. Special relativity ?
They didn't observe doppler shifts, although they used a doppler effect, using a loudspeaker, to measure the amount of shift due to gravity. The theory is described by General Relativity not Special Relativity.
relative velocity compared to the absolute C that is independant of gravity ?
C is not absolute. You will always measure your speed relative to light as c no matter how fast you travel, so it can't be absolute, it is only constant.
they are fixed at set distances to each other, and whilst you stay fixed to them you are in there frame ? So one pulse, and measure the strike intervals on the sphere you measure the absolute velocity of the frame ?
No, you only measure the time to get from the light gun to the sphere, this is not an absolute measuremet of the frame velocity.
Imagine you start out at 100mph relative to earth and take your measurement, now increase your speed to 2000mph, it will still take the same time for light to reach the sphere because you are moving together. So you cannot tell what speed you are moving. Adding an external observer doesnt help because neither of you really know who is moving, and you only started relative to earth, but that's moving.
As with the Box, I am happy to explain why absolute is not possible and then leave you to work through your own ideas, so enjoy developing your new theory, but try to keep it in line with experimental evidence. I'll leave you to it.
-
Which is it Colin either
A pulse in all directions equal to the velcity of the sphere going equally in all directions and hitting the sphere sides all at once
Or a pulse going at its own independant velocity to the velocity of the sphere , striking the sphere at differen TIMES.
As i mentioned phyti elongated elliptical sphere is the only way to rectify it?
-
Which is it Colin either
A pulse in all directions equal to the velcity of the sphere going equally in all directions and hitting the sphere sides all at once
Or a pulse going at its own independant velocity to the velocity of the sphere , striking the sphere at differen TIMES.
As i mentioned phyti elongated elliptical sphere is the only way to rectify it?
I don’t really understand your scenarios here. In order to answer the relativity view I need to be very specific about the scenario.
It doesn’t have anything to do with the pulse having any sort of independent velocity, it has to do with your velocity relative to the sphere.
If you are travelling at the same velocity as the sphere (whether you are inside or outside the sphere) and a 360 light pulse goes off at the exact centre of the sphere then you will see the pulse hit all parts of the sphere at the same time. Also, to be clear, the light gun does not have to be travelling at the same velocity as the sphere, it could be going in the opposite direction. Also, you will always see a sphere.
If you are not travelling at the same velocity as the sphere you will not see the pulse hit all parts of the sphere at the same time. It will hit what you judge to be the rear 1st. What you see of the sphere will depend on your velocity including angle of approach and will vary between a flattened disc - flattened front to back - and a sphere which appears to rotate as it goes by. You won’t see an elongated ellipsoid as you describe, that has been disproved by experiment with high speed gold atoms where they become a flattened disc - narrow front to back.
-
Adnit it colin it confuses you too, and phyti explaination is in the right area. Im gonna mark it best answer ............
Yes the light gun has to be travelling at the same rate as the sphere, i said so.
If you turn on your headlights at speed c no light is emmitted, if you turn your rear lights on at c light still emmits at c that is basically the paradox. Explained by the ellipsoid.
Also if the pound rebka was to see about time dilation, and gravity does not affect light, other than through dilation, why did the clock in the reciever need a doppler shift, as the clock in the reciever would have been faster/ slower in accordance with the light being faster /slower at that clock ?
-
Which is it Colin either
A pulse in all directions equal to the velcity of the sphere going equally in all directions and hitting the sphere sides all at once
Or a pulse going at its own independant velocity to the velocity of the sphere , striking the sphere at differen TIMES.
As i mentioned phyti elongated elliptical sphere is the only way to rectify it?
Let's set a scenario up this way: You have two flash bulbs(A & B), each located at the center of its own spherical shell made of a reflective material. The two bulbs are moving at 0.5c relative to each other, and pass through the same point. (we won't worry about how they and the reflective spheres pass through each other, but for the sake of argument, assume they can.)
At the instant they reach the same point, each flash bulb goes off, emitting light from that point.
First we will only consider what happens according to A, in terms of light reflecting off of its own sphere. Both flashes will expand outward from it spherically, strike the interior of its shell, reflect back and return to the center at the same time. Its light will not be shifted, while the returning light that was emitted from B will be variously shifted from red to blue depending on which direction is is returning from.
If A considers the light that reflects off of the interior of B's shell, the following happens. The light still expands outward at spherically from A. B's shell however, is length contracted and looks like an ellipsoid. B and its shell is also moving with respect to A, so B, and its ellipsoid does not remain at the center of this expanding sphere of light. Different parts of this expanding sphere will hit different points of the interior of B's ellipsoid at different times. So for instance, the light will hit the Trailing side of B's ellipsoid first, Be cause it is rushing towards that edge of the expanding sphere and the leading side is running away from the other edge of the expanding sphere. Once the light hits the sides of the ellipsoid it is reflected in the opposite direction, but is still traveling at c relative to A. So now light that is reflected from the trailing edge is "chasing after" B, while light that is reflected from the leading edge and B are rushing towards each other. The upshot is that A will note that both the light it emitted and the light emitted by B and A and reflected off of the interior of B's shell will meet at B at the same moment.
B will see the same thing, with the difference that it will be the light from A that it will measure as being Doppler shifted.
Both A and B will measure that it will take the flashes longer to return to the other bulb than it did to return to itself. If A measures the time for the flashes to return to itself is 1 sec, it will measure the time for the flashes to return to B as being 1.155 sec. B will measure the time it takes the flashes to return to itself as being 1 sec and the time for the flashes to return to
A, as being 1.155 sec. This is time dilation.
The ellipsoid shape each measures the other sphere as having is length contraction.
The fact that each measures the flashes as reflecting off the interior of the other shell at different times is the relativity of simultaneity.
A word about Doppler shift. There are two types of Doppler shift to consider. One is the classical version such as happens with sound. With this Doppler shift, there is a propagation medium, and both the transmitter's and receiver's velocity wiht respect to the medium needs to be taken into. You get a different shift if the receiver is moving relative to the medium and transmitter isn't than you get if it is the other way around.
When dealing with light( or any electromagnetic radiation) in a vacuum, you need to use relativistic Doppler shift. This Doppler shift is only dependent on the relative velocity between transmitter and receiver.
The point is that if you could use Doppler shift to measure absolute motion in a vacuum, then it would have to take the form of classical Doppler shift.
Now it turns out that not too long ago, and inadvertent test of which form works for light took place. It dealt with one of our probes to to moon of one of the gas giants. There was a ground probe and an orbiter. It turned out that there was a problem with the communication between the two. The communication protocol required a really tight frequency window, and it turned out that the ground transmitter and orbiter were out of match with each other by enough to prevent communication.
They addressed the problem by altering the orbiter's trajectory so that at during the moments of transmission the relative velocity between orbiter and ground was just the right amount to create a Doppler shift that shifted the ground transmissions enough to match the orbiter's protocol.
Now, if absolute motion effected Doppler shift, they would have had to take the Moon's orbital motion, and the orbital motion of the Planet it was orbiting, etc into account, and since the Moon's orbital motion with respect to the planet's orbital motion was constantly changing, they would have to be constantly changing the orbit of the orbiter in order to make sure that the Doppler shift was correct for reception. They did not have to do this; All they needed to concern themselves with was the relative velocity of the orbiter with respect to the Moon's surface. In other words, the form of Doppler shift which does not require absolute motion gave the correct answer, while the form that would have required absolute motion would have given them the wrong answer.
-
Petro;
Perceived doppler shift results from a difference in speed between emitter and receiver.
In the case of a sphere/ellipsoid, the distance between the center and any random element of the surface remains constant. Why would there be doppler effects?
-
AdWnit it colin it confuses you too
Why should I admit something that is untrue? I’m not the one who is confused, the answers I gave are correct and I’ve taken the trouble to explain under what circumstances they apply.
phyti explaination is in the right area. Im gonna mark it best answer ............
No problem with this, other than the fact you are misinterpreting what he said. Eg
The moving inertial frame behaves like a rest frame.
This is exactly the same as what I described, you see a sphere and the light hits the sphere at the same time all round.
Yes the light gun has to be travelling at the same rate as the sphere, i said so.
No it doesn’t. It can be travelling at a different velocity, it just has to go off at the centre of the sphere.
If you turn on your headlights at speed c no light is emmitted, if you turn your rear lights on at c light still emmits at c that is basically the paradox. Explained by the ellipsoid.
As no car can travel at c there is no paradox. At all speeds up to c you would see light emitted from both front and rear at c, there would be some odd effects as the road would appear foreshortened and any light reflected from it would blueshift - possibly beyond visible spectrum depending on speed. Anyone approaching you will measure light at c, but again shifted.
No, it is not explained by ellipsoid, the ellipsoid is the effect not the cause. As I described, what your friend who is moving relative to the sphere sees will vary from a flattened disc - which is an extreme ellipsoid - to a sphere. Your friend will see the sphere contracted in length, but not elongated vertically ie perpendicular to direction of travel, this ellipsoid will in the extreme case become a flattened disc. Also, your friend will not see the light hit the front and back of this ellipsoid at the same time.
Read what Janus says, it’s all the same thing.
Anyway, I’ll leave you to your New Theory.
-
Thanks for the answers.
The red shift stuff and pound rebka needing to compensate for the fixed position of the emmitter in relation to the reciever and as there is no difference in position in my emmitter reciever. The light forward of your emmitter within the sphere will be emmitted under increaced velocity, the light behind you under decreaced velocity. The redshift would be detectable in the pr experiment as with doppler to a fixed position, ie your friend, and thus be able to give the speed, however the mm experiment states thatlight goes equally inall directions.
But due to the elipsoid fashioned sphere the pound and rebka and mickelsonM both match,
-
The light forward of your emmitter within the sphere will be emmitted under increaced velocity, the light behind you under decreaced velocity.
(if I interpret correctly)
Light does not aquire the speed of the emitter. That is the subtle difference when adding velocity vectors of material objects. It is the reason for time dilation.
-
The light forward of your emmitter within the sphere will be emmitted under increaced velocity, the light behind you under decreaced velocity.
(if I interpret correctly)
Light does not aquire the speed of the emitter. That is the subtle difference when adding velocity vectors of material objects. It is the reason for time dilation.
Yep phiti thanks im beginning to get it. Like you say the shape fits the need, i can only think what shape the ellipsiod would take lengthening and narrowing ?, and how light would behave as suggested by Janus , if a reflection was used in the sphere ?
How much of the sphere is forward of the emmitter ?
How does the light bounce off the inside, given light emmitted sideways will end up along way to the rear of the emmitter, but for reflection purposes it would have to follow its course back ?
How long must the sphere become?
Would there be lensing as the light passes from the time dilation, to the other time dilation?
Pete
-
The light forward of your emmitter within the sphere will be emmitted under increaced velocity, the light behind you under decreaced velocity.
(if I interpret correctly)
Light does not aquire the speed of the emitter. That is the subtle difference when adding velocity vectors of material objects. It is the reason for time dilation.
Yep phiti thanks im beginning to get it. Like you say the shape fits the need, i can only think what shape the ellipsiod would take lengthening and narrowing ?, and how light would behave as suggested by Janus , if a reflection was used in the sphere ?
How much of the sphere is forward of the emmitter ?
How does the light bounce off the inside, given light emmitted sideways will end up along way to the rear of the emmitter, but for reflection purposes it would have to follow its course back ?
How long must the sphere become?
Would there be lensing as the light passes from the time dilation, to the other time dilation?
Pete
You are in a sphere "at rest". You fire the light at the inside of the sphere. it hits the reflective surface and comes back to you along the same path.
I am in a spaceship flying past you at 0.5c in a direction perpendicular to the direction that you fired the light. What do I see? Your sphere will be contracted by in the direction of our relative motion. I see the light leave you, hit the same spot of the sphere and return to you. If I were to trace the path the light took relative to my ship, it would trace out two sides of a isosceles triangle. Neither the outbound or return path will be perpendicular to our relative line of motion, nor will the return path, relative to my ship, retrace the out bound path.
Now let's say that is you that are "moving" at 0.5c, and I am the one at "rest" , Now what do we see? exactly the same thing.. It makes no difference which one of us we consider as be the one moving.
If you do the test with the light and see it reflect right back to you, and then accelerate up to some speed perpendicular to the direction you fired the light, and then repeat the experiment, you get exactly the same result (as long as you are not actively accelerating when you fire the light.)
While light will not gain or lose speed relative to you due to the relative motion of the emitter, It can have its velocity changed by way the direction it travels relative to you as compared to the angle it is emitted relative to the emitter. This is known as the aberration of light.