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Physics, Astronomy & Cosmology / Re: Can you measure the one way speed of light without synchronised clocks?
« on: 06/07/2021 07:32:24 »
I think we can measure one way speed of light.
we need to redefine simultaneity. My proposition is as follows:
if a rigid body AB of length l perpendicular to X axis is moving without any acceleration parallel to X axis and at time t0 its point A is at location (x,0) then simultaneously its point B is at location (x,x+l)
Let's now design the experiment to synchronize distant clocks and measure one way speed of light:
Imagine four spaceships flying as perfect square EFGH towards (or away from) not moving (at least relative to each other) points ABCD, where AD is parallel to EF and distance EF equals AD. Points EG should be collinear with points AB and points FH collinear with CD. Making sure that ABCD (and EFGH) is a square is relatively easy, since 2-way speed of light is constant:
we can measure (and correct, if necessary) distances BD and CA by sending light signals from B to D (and from C to A) and back
Now at certain time (clocks at A and D can be pre-synchronized using Einstein convention, but it is not absolutely necessary) we can measure distance from A to G (L) and from D to H (L’) using light (laser) signal send from A to G (and reflected back to A) as well as distance from D to H. If the distance AG (L) equals DH (L’) signals from A and D had been sent simultaneously; if not, it would be easy to adjust the clocks so they are synchronized.
Please let me know if I made any wrong assumption
Of course, theoretically it would be sufficient to have only the lines AD parallel to GH, but practically it could be difficult to make sure they are parallel to each other
we need to redefine simultaneity. My proposition is as follows:
if a rigid body AB of length l perpendicular to X axis is moving without any acceleration parallel to X axis and at time t0 its point A is at location (x,0) then simultaneously its point B is at location (x,x+l)
Let's now design the experiment to synchronize distant clocks and measure one way speed of light:
Imagine four spaceships flying as perfect square EFGH towards (or away from) not moving (at least relative to each other) points ABCD, where AD is parallel to EF and distance EF equals AD. Points EG should be collinear with points AB and points FH collinear with CD. Making sure that ABCD (and EFGH) is a square is relatively easy, since 2-way speed of light is constant:
we can measure (and correct, if necessary) distances BD and CA by sending light signals from B to D (and from C to A) and back
Now at certain time (clocks at A and D can be pre-synchronized using Einstein convention, but it is not absolutely necessary) we can measure distance from A to G (L) and from D to H (L’) using light (laser) signal send from A to G (and reflected back to A) as well as distance from D to H. If the distance AG (L) equals DH (L’) signals from A and D had been sent simultaneously; if not, it would be easy to adjust the clocks so they are synchronized.
Please let me know if I made any wrong assumption
Of course, theoretically it would be sufficient to have only the lines AD parallel to GH, but practically it could be difficult to make sure they are parallel to each other