What the heck is Time?

Discussions on classical and modern physics, quantum mechanics, particle physics, thermodynamics, general and special relativity, etc.

Re: What the heck is Time?

Inchworm » 10 Feb 2017, 21:41 wrote:If we have nothing faster than the speed of sound to measure sound, and if we cannot measure our speed through air, then I think that we will get the same result as for light: it would be impossible to know our speed with regard to air, so we would have to rely on a two way speed of sound. To measure our speed with regard to one another, we would thus have to decide which one of us is at rest, the same as for light.

You can at any time observe if your are at rest in air - otherwise there is no air and no sound, so what are we discussing then?

And if two aircraft determine that they are not static relative to the air (which they can always do), they cannot use Doppler with sound to determine their relative speed; they will each have to measure their own speed through the air and then subtract the two to get relative speed. I have given ample calculations to show this.

Doppler with e.m. waves does not suffer this limitation, as I have also illustrated. It is one of the many difference between sound- and light observations.

BTW, it is trivial to measure that the speed of sound external to the a/c and determine that it does not propagate at 1000 km/h relative to the a/c, but much more or much less, depending on the sound direction and the a/c's velocity through the air.

It is similarly trivial to measure the speed of light external to a spacecraft and determine that it always propagates at c relative to the spacecraft, independent of direction.

Failure to grasp these points will make it impossible for anyone to grasp high-speed physics.

BurtJordaan
Forum Moderator

Posts: 2595
Joined: 17 Oct 2009
Location: South Africa
Blog: View Blog (9)

Re: What the heck is Time?

So true Jorrie, if you can't even grasp what relative velocity means you start coming up with all kinds of wild theories to try to fill that giant hole in your understanding. The worst part is it takes years to convince someone that they don't understand this seemingly simple concept.
ralfcis
Banned User

Posts: 946
Joined: 19 Jun 2013

Re: What the heck is Time?

Jorrie wrote:

As long as you stick to the relativistic math and always come up with the right answers, it does not matter what interpretation you attach to it. If it works for you, it works.

I have checked your last posts, but your interpretations may not enable communication with them, or with other readers, for that matter.

A theory is an interpretation of facts. In fact, a standing theory is the simplest interpretation of facts. Yes I can barely understand it when I re-read it that's why I'll re-write it in simpler terms in the Doppler twins thread. It'll take months. Yes I use relativistic math to come up with answers similar to what relativity predicts. In my last example you could say both theories agree that Alice ages 2 years less than Bob. Relativity can only make that prediction when Bob is 10. I can make that prediction when Bob is 8. Relativity does not make the same prediction even though the same math is available to it. The prediction also comes with a whole new understanding of the nature of time that may further science in future investigations. This is another requirement of being a new theory.

P.S. I'll take your congratulations as a sign I've finally graduated.
ralfcis
Banned User

Posts: 946
Joined: 19 Jun 2013

Re: What the heck is Time?

BurtJordaan » February 10th, 2017, 11:18 pm wrote:You can at any time observe if your are at rest in air - otherwise there is no air and no sound, so what are we discussing then?
I think that all the waves travel the same way, I think that all their motion is independent from the motion of source or observer, so I'm trying to understand the way light travels with this only premise, while comparing it to sound. For that, I must imagine that it is impossible to know the speed of things with regard to air, while still knowing the way sound travels through it. The only difference is the speed of the waves, but doppler effect is independent from the kind of waves. It's a mind experiment, it's not reality, but it helps me understand light, so I hope it will for anybody.

And if two aircraft determine that they are not static relative to the air (which they can always do), they cannot use Doppler with sound to determine their relative speed; they will each have to measure their own speed through the air and then subtract the two to get relative speed. I have given ample calculations to show this.
If they can't measure their speed in air, won't they be in the same situation than with light? Won't they be forced to rely on doppler effect only?

Doppler with e.m. waves does not suffer this limitation, as I have also illustrated. It is one of the many difference between sound- and light observations.
Both are waves, and both waves are independent from the motion of bodies, so apart from their speed, where is the difference that you see exactly.

BTW, it is trivial to measure that the speed of sound external to the a/c and determine that it does not propagate at 1000 km/h relative to the a/c, but much more or much less, depending on the sound direction and the a/c's velocity through the air.
Can't find out what a/c means, sorry.

It is similarly trivial to measure the speed of light external to a spacecraft and determine that it always propagates at c relative to the spacecraft, independent of direction.
It is impossible to measure the one way speed of light, and I think it would also be the case for sound if we could not measure the speed of air and if we didn't have faster than sound devices to measure it.

Inchworm
Member

Posts: 604
Joined: 25 Jan 2016
Location: Val-David, Quebec, Canada

Re: What the heck is Time?

Inchworm » 11 Feb 2017, 17:02 wrote:It is impossible to measure the one way speed of light, and I think it would also be the case for sound if we could not measure the speed of air and if we didn't have faster than sound devices to measure it.

How about just installing two synchronized clocks, one in the nose and the other in the tail of the aircraft (a/c) and/or the spacecraft? To synchronize the clocks, we just put them next to each other, synchronize them and then slowly move each to its required position. As long as the vehicle stay inertial, the clocks will stay in perfect sync.

Then, with the necessary detectors outside of the craft, measure the speed of sound or the speed of light, whichever may be the case in question. Again, you will find that the speed of light is always c relative to the craft, but the speed of sound relative to the craft depends on its speed through whatever material medium the craft moves. No need for something faster than sound or faster than light to do any of these measurements.

There are other methods, using only one clock. The best I've seen is our resident expert, Dr Don Lincoln's Test of the one-way speed of light. He is a practicing scientists that has actually done this test.

BurtJordaan
Forum Moderator

Posts: 2595
Joined: 17 Oct 2009
Location: South Africa
Blog: View Blog (9)

Re: What the heck is Time?

Inchworm » 11 Feb 2017, 17:02 wrote:Both are waves, and both waves are independent from the motion of bodies, so apart from their speed, where is the difference that you see exactly.

Sound requires a material medium to move in and has a variable one-way speed relative to the source and relative to a detector. Light requires no material medium and has an invariant one-way speed relative to both source and detector. This is the crux of the matter.

BurtJordaan
Forum Moderator

Posts: 2595
Joined: 17 Oct 2009
Location: South Africa
Blog: View Blog (9)

Re: What the heck is Time?

Burt wrote:Again, you will find that the speed of light is always c relative to the craft, but the speed of sound relative to the craft depends on its speed through whatever material medium the craft moves.
I'm afraid an atomic clock is a faster than sound device Burt. I'm pretty sure that if we would use a clock that is no more precise than sound, we couldn't measure its one way speed. Light is probably traveling like any other type of wave since it has the same properties: it can also be reflected, refracted, diffracted, doppler shifted, aberrated, ...etc. Its only difference is that it seems to be the upper speed limit. I bet that a Michelson-Morley experiment made with sound instead of light would also show no motion through air. If I make it and it shows a null result, will you change your mind about relativity? :0)

Inchworm
Member

Posts: 604
Joined: 25 Jan 2016
Location: Val-David, Quebec, Canada

Re: What the heck is Time?

Inchworm » 12 Feb 2017, 17:46 wrote:I bet that a Michelson-Morley experiment made with sound instead of light would also show no motion through air. If I make it and it shows a null result, will you change your mind about relativity? :0)

Sadly, you will waste your time and money, because down-to-earth logic tells us that it will show you your speed through air.

I think we have beaten this particular topic to death now and the original question has been answered as well as physics can do it. After one more reply, I suggest that this thread be closed.

BurtJordaan
Forum Moderator

Posts: 2595
Joined: 17 Oct 2009
Location: South Africa
Blog: View Blog (9)
 ronjanec, RoccoR liked this post

Re: What the heck is Time?

Ok here's the closer:

The difference between science and philosophy is math. If you don't present your theories with math to back them up, they shouldn't even be in the personal theories section let alone the physics section, they should be in the philosophy section. People who speak in word salad or stream of consciousness should be even further removed into another separate section we could call Section 8.
ralfcis
Banned User

Posts: 946
Joined: 19 Jun 2013

Re: What the heck is Time?

And I suggest that people who say other people's writings is word salad see their threads restricted to Section 9. :0)

Inchworm
Member

Posts: 604
Joined: 25 Jan 2016
Location: Val-David, Quebec, Canada

Re: What the heck is Time?

I didn't say yours or Dave's posts are word salad, they are just un-math-supported philosophy pretending to be science. Word salad, on the other hand, is quite evident from the start.
ralfcis
Banned User

Posts: 946
Joined: 19 Jun 2013

Re: What the heck is Time?

Word salad, math dressing, its all goes at the same place if it's not digestible. :0)

Inchworm
Member

Posts: 604
Joined: 25 Jan 2016
Location: Val-David, Quebec, Canada

Re: What the heck is Time?

Gosh, I'd forgotten I'd asked this! I have to admit I never actually came back to it... But there's a lot there to digest.
Graeme M
Member

Posts: 159
Joined: 04 Nov 2015

Previous