The discussion centers on the constancy of the speed of light, as described by Einstein's special relativity. Participants explore the implications of light traveling from the sun to Earth and the role of observers, such as satellites, in measuring this phenomenon. Key points include the distinction between the speed of light as a constant (denoted as "c") and its variable behavior in different media. The conversation concludes that while we observe the speed of light as constant, the underlying reasons for this behavior remain unexplained.
PREREQUISITESPhysicists, students of physics, and anyone interested in the fundamental principles of light and relativity.
anuttarasammyak said:Say 8 minutes to Earth, it takes less minutes for sunlight to reach satellite.
I spy with my little eye something beginning with "p" ...?Vanadium 50 said:What is the question here?
Halc said:An ant walks 5 cm/sec (3m/min) directly towards my picnic, 24m away. It will take 8 minutes for it to reach my picnic. There is a bread crumb halfway, so it will pass that breadcrumb after only 4 of those minutes.
If the ant sees the bread crumb and decides it is enough, perhaps she will take the offering and go no further. Similarly, if your satellite actually observes the photon, the photon isn't going to get to Earth at all. It can't be measured in two different places.
I did not need to invoke relativity theory to work any of that out.
Fine. It being an observer or not has no bearing on when the light gets there.r731 said:I thought of the satellite as an observer (as in special relativity).
Same as the ant. So long as it is not accelerating, a small particle traveling at near c gets to the halfway point in half the time it takes to go the whole distance.r731 said:What about small particles that travel near the speed of light?
r731 said:I ask this
"C" is a constant in many physics equations and IS NOT the "speed of light" but represents(!) Maximum attainable velocity in this universe. The actual speed of light is variable depending on the optical density of a material.r731 said:Visualize the following scenario. A star such as the sun, and a planet such as Earth are located in a solar system. A photon travels from sun (x0) to Earth (x1), and a satellite is in the midway observing the photon. This is relates to Einstein's special relativity.
I ask this since it take light about 8 minutes to reach earth.
I'd not phrase it that way, since ##c## is not really attainable. Things either always travel at ##c## (light, for example) or cannot attain it ever. You are correct, though, that ##c## is better thought of as a fundamental constant, the invariant speed, that light just happens to travel at. That's a consequence of its masslessness - if we found that the photon had a mass then that would imply that light does not travel at ##c## in vacuum, but would not change relativity.shjacks45 said:"C" is a constant in many physics equations and IS NOT the "speed of light" but represents(!) Maximum attainable velocity in this universe.
We say that light does not have mass but what makes it then to change its direction when from a distant star as it reaches the sun?Why does it curve due to the effect of gravity and does not move straight?What about the fact that light cannot escape from the gravitational pull of a black hole?Ibix said:I'd not phrase it that way, since ##c## is not really attainable. Things either always travel at ##c## (light, for example) or cannot attain it ever. You are correct, though, that ##c## is better thought of as a fundamental constant, the invariant speed, that light just happens to travel at. That's a consequence of its masslessness - if we found that the photon had a mass then that would imply that light does not travel at ##c## in vacuum, but would not change relativity.
The geometry of spacetime, a.k.a. gravity.universe function said:We say that light does not have mass but what makes it then to change its direction when from a distant star as it reaches the sun?
Sorry perhaps the question was not needed it was quite obvious I just was not sure.Ibix said:The geometry of spacetime, a.k.a. gravity.