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originally posted by: Degradation33
a reply to: rounda
If we could build a ship to travel at 99.999999999999% the speed of light, with 12 decimal places, a person could travel the 2.5 million lightyears to Andromeda and only experience .35 TIME DILATED years.
To that, I can't say anything other than take it up with relativity.
I think you are mistaken when you say "which it isn't", though you're correct about the first part that relativity is based on the speed of light being a constant, or more specifically, here is more or less how Einstein phrased the two postulates of special relativity:
originally posted by: rounda
And if I'm not mistaken, relativity is based on the idea the speed of light is constant. Which it isn't....
1. The laws of physics, including electromagnetism, are the same in all inertial frames.
2. Every observer measures the same value c for the speed of light (in vacuum) in all inertial frames.
originally posted by: Arbitrageur
I think you are mistaken when you say "which it isn't", though you're correct about the first part that relativity is based on the speed of light being a constant, or more specifically, here is more or less how Einstein phrased the two postulates of special relativity:
originally posted by: rounda
And if I'm not mistaken, relativity is based on the idea the speed of light is constant. Which it isn't....
2 Postulates of Special Relativity
1. The laws of physics, including electromagnetism, are the same in all inertial frames.
2. Every observer measures the same value c for the speed of light (in vacuum) in all inertial frames.
By the way, relativity only applies to "normal" space ships. The speculated alcubierre warp bubble is sort of able to "bypass" special relativity by creating a separate space-time in the warp bubble, or so the hypothesis goes. Whether such a thing is possible has yet to be demonstrated, and it may not be possible, because you can go on a diet all you want but no matter how much weight you lose, your weight will never, ever be less than zero, yet it's such a negative mass that allegedly can create the alcubierre warp bubble.
What makes you think the speed of light in a vacuum is not constant?
originally posted by: rounda
"Which it isn't" means the speed of light is not a constant. Because it's not.
It may not be possible to "prove" anything with certainty, and general relativity may not be an ultimate theory, but so far it has been tested and observed test results match the theory. Some tests are discussed here:
But see, here's the thing. General Relativity can never be tested. It can never be proven. It can never even be observed.
I'm impressed by the incredible accuracy of those clocks to make such precise measurements of time dilation when the height of the clock only changes by 1 meter or even a little less than that. Some of the old time dilation tests flying atomic clocks on airplanes like the Hafele–Keating experiment seemed rather cumbersome in comparison, but those results too were consistent with special and general relativity.
Another consequence of Einstein's theory is that time runs more slowly in a deeper gravitational potential. For example, if two identical clocks are separated vertically by 1 km near the surface of the earth, the higher clock emits about 3 more second-ticks than the lower one in a million years. These consequences of relativity have been observed with atomic clocks at high velocities and with large changes in elevation. Previously, smaller relativistic shifts could only be seen in short-distance γ-ray Mössbauer spectroscopy measurements. Here we compare two optical atomic clocks to observe time dilation from relative speeds of less than 10 m/s and changes in height of less than 1 m. This sensitivity to small relativistic clock shifts is enabled by recent accuracy improvements...
But see, here's the thing. General Relativity can never be tested. It can never be proven. It can never even be observed.
The code inside the GPS satellites use the equation, plus some other variables, to calculate their individual amount of experienced time dilation. The satellites experience around 7 microseconds of 'delay' every 24 hours due to their speed.
originally posted by: Degradation33
a reply to: rounda
But see, here's the thing. General Relativity can never be tested. It can never be proven. It can never even be observed.
Are you sure?
You got the part about GPS satellites? Anything that needs a precise measurement.
I don't know what constitutes proof or observation for you, but I'm pretty sure a slightly red-shifted satellite qualifies as a demonstration of relativity.
The code inside the GPS satellites use the equation, plus some other variables, to calculate their individual amount of experienced time dilation. The satellites experience around 7 microseconds of 'delay' every 24 hours due to their speed.
Change in time equals rest time over the square root of 1 minus velocity squared over the speed of light squared.
This:
That's a plug and play equation for time dilation that works everywhere it's needed. You can prattle about general relativity not being proven all you want, but still be left to explain why all satellites have to account for the "theory" of relativity to keep precise time.
So why do satellites need to account for time dilation if relativity is BS? If relativity can never be tested why do satellites in orbit experience less time than clocks on earth and need to be compensated for?
If not "RELATIVE VELOCITY TIME DILATION" what else could it be?
originally posted by: Arbitrageur
What makes you think the speed of light in a vacuum is not constant?
originally posted by: rounda
"Which it isn't" means the speed of light is not a constant. Because it's not.
I must have missed that, care to enlighten me with some details?
originally posted by: rounda
originally posted by: Arbitrageur
What makes you think the speed of light in a vacuum is not constant?
originally posted by: rounda
"Which it isn't" means the speed of light is not a constant. Because it's not.
Scientists proving it isn't.
That's special relativity... And they figured out it doesn't work unless gravity moves at or faster than the speed of light.
The first direct observation of gravitational waves was made on 14 September 2015 and was announced by the LIGO and Virgo collaborations on 11 February 2016.[3][4][5] Previously, gravitational waves had been inferred only indirectly, via their effect on the timing of pulsars in binary star systems. The waveform, detected by both LIGO observatories,[6] matched the predictions of general relativity[7][8][9] for a gravitational wave emanating from the inward spiral and merger of a pair of black holes of around 36 and 29 solar masses and the subsequent "ringdown" of the single resulting black hole.
The velocity of a wave can be defined in many different ways, partly because there are many different kinds of waves, and partly because we can focus on different aspects or components of any given wave. The ambiguity in the definition of "wave velocity" often leads to confusion, and we frequently read stories about experiments purporting to demonstrate "superluminal" propagation of electromagnetic waves (for example). Invariably, after looking into the details of these experiments, we find the claims of "superluminal communication" are simply due to a failure to recognize the differences between phase, group, and signal velocities.
There are quite a few articles like that talking about light not traveling at the speed of light, but when it's in a vacuum they are all talking about things like group velocity or phase velocity, which the science writer you cited didn't even mention, maybe because he thinks his non-physicist readers won't know what those terms mean? They are explained in the link above if you're not familiar.
originally posted by: rounda
www.sciencenews.org...
You can play all sorts of tricks with group velocity, you can even make it faster than the speed of light, but it's a change in group velocity, and you can't send any information faster than light just because the group velocity is faster than light. I've seen science writers confuse that topic too, and claim we can send information faster than light when the group velocity is faster than light, but it's not true and the scientists don't claim that, just the science writers who don't understand what they are writing about very well.
We study the group velocity of single photons by measuring a change in their arrival time that results from changing the beam's transverse spatial structure.