## Relativity?

How does science work? And what's all this about quantum mechanics?

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davidm
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### Re: Relativity?

Viveka wrote: Mon Oct 30, 2017 6:32 pm Someone please respond to this:
Let us change the universe up a little. If light speed were 3 km per hour, and we had a light-clock, then if we moved the light-clock perpendicular to the path of the clocks' motion at 20 km per hour, (or whatever speed necessary) it would actually lag behind the mover and not even hit the mirrors that constitute the light-clock.
Right! But in that case, the universe and the laws that describe it would be completely different! You are positing a world in which a material object (physical light clocks) travel faster than light! That's not our world!
Viveka
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### Re: Relativity?

davidm wrote: Mon Oct 30, 2017 7:40 pm
Viveka wrote: Mon Oct 30, 2017 6:32 pm Someone please respond to this:
Let us change the universe up a little. If light speed were 3 km per hour, and we had a light-clock, then if we moved the light-clock perpendicular to the path of the clocks' motion at 20 km per hour, (or whatever speed necessary) it would actually lag behind the mover and not even hit the mirrors that constitute the light-clock.
Right! But in that case, the universe and the laws that describe it would be completely different! You are positing a world in which a material object (physical light clocks) travel faster than light! That's not our world!
It's called a Gedankenexperiment! - Albert Einstein
davidm
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### Re: Relativity?

Viveka wrote: Mon Oct 30, 2017 8:05 pm
davidm wrote: Mon Oct 30, 2017 7:40 pm
Viveka wrote: Mon Oct 30, 2017 6:32 pm Someone please respond to this:
Let us change the universe up a little. If light speed were 3 km per hour, and we had a light-clock, then if we moved the light-clock perpendicular to the path of the clocks' motion at 20 km per hour, (or whatever speed necessary) it would actually lag behind the mover and not even hit the mirrors that constitute the light-clock.
Right! But in that case, the universe and the laws that describe it would be completely different! You are positing a world in which a material object (physical light clocks) travel faster than light! That's not our world!
It's called a Gedankenexperiment! - Albert Einstein
What is the point of such an experiment? It bears no relation whatever to the world we live in, whereas Einstein's thought experiments DID bear such a relation. A world in which physical objects traveled faster than photons would be completely unintelligible to us. Almost surely it would not be able to harbor life of any kind.
thedoc
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### Re: Relativity?

thedoc wrote: Mon Oct 30, 2017 3:32 am
Viveka wrote: Mon Oct 30, 2017 1:26 am Yes, I completely understand what you are saying. I summed up the SRT in a sentence. However, if it is true that the photons are invariate, why do they always 'hit the target' when they are in a light-clock? Because of the variance of space and time? I addressed this in my previous post that I feel you should read. I basically say that the reason why the light-clock always 'hits the target' is because of Galilean Transformations or Light-Anchoring.

Just because Light-speed is invariate supposedly means that there has to be length-contraction and time-dilation because you are taking the invariate speed of light, and then making time and space variate in order to keep the invariancy of the speed of light. That about sums up Special Relativity.
Because the photon is aimed at the mirror even though that mirror is moving, the photon is aimed at where the mirror will be not at where the mirror is. The photon moves with the speed of the object that it is moving on, even though the speed of light is finite the distance is not, and the increased distance will require a longer time of travel.
It should be noted that the photons are traveling with the clock just as humans are traveling with the Earth as it rotates and orbits around the Sun but we don't notice this movement and the photon would not notice the movement unless there was acceleration.
Viveka
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### Re: Relativity?

davidm wrote: Mon Oct 30, 2017 8:10 pm
Viveka wrote: Mon Oct 30, 2017 8:05 pm
davidm wrote: Mon Oct 30, 2017 7:40 pm

Right! But in that case, the universe and the laws that describe it would be completely different! You are positing a world in which a material object (physical light clocks) travel faster than light! That's not our world!
It's called a Gedankenexperiment! - Albert Einstein
What is the point of such an experiment? It bears no relation whatever to the world we live in, whereas Einstein's thought experiments DID bear such a relation. A world in which physical objects traveled faster than photons would be completely unintelligible to us. Almost surely it would not be able to harbor life of any kind.
Yeah, I"m sure the Twin's Contradiction has great relevance to our common sense and the world as we know it.
davidm
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### Re: Relativity?

Viveka wrote: Mon Oct 30, 2017 10:36 pm
davidm wrote: Mon Oct 30, 2017 8:10 pm
Viveka wrote: Mon Oct 30, 2017 8:05 pm

It's called a Gedankenexperiment! - Albert Einstein
What is the point of such an experiment? It bears no relation whatever to the world we live in, whereas Einstein's thought experiments DID bear such a relation. A world in which physical objects traveled faster than photons would be completely unintelligible to us. Almost surely it would not be able to harbor life of any kind.
Yeah, I"m sure the Twin's Contradiction has great relevance to our common sense and the world as we know it.
The twin's "contradiction" is neither a contradiction nor a paradox. It is a verifiable prediction of special relativity.

Your "thought" experiment about material objects traveling faster than photons bears no relation to reality and could only be considered as a speculative alternative universe. I've no idea what such a realm would look like, but I'm pretty sure nothing would be alive in it. Maybe uwot would like to speculate.
davidm
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### Re: Relativity?

I should amend the above somewhat. There are ways to imagine alternative laws of physics, but to do so, we have to see if they coherently hang together . Can we coherently imagine a universe in which photons travel slower than matter?

Apparently we can, if the physicist Max Tegmark is to be believed. The way to bring about such a universe, says Tegmark, is simply to flip the standard dimensionality of spacetime (3 space dimensions wedded to one time dimension) to get the opposite: Three time dimensions wedded to one space dimension. If the universe were like that, Tegmark says, then all matter would consist of tachyons — particles that always travel faster than light, but can never travel as slow as light. (Our universe consists of tarydons.)

But, I’ve no idea what such a world would look like. I can’t even conceive what it would mean to experience one dimension of space and three of time, with the speed of light the lowest possible speed in the universe. Maybe uwot has some ideas, but I sure don’t!
davidm
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### Re: Relativity?

Fascinating paper by Tegark on the dimensionality of spacetime. Upshot: only a world of three spatial dimension and one time dimension has sentent observers. So our particular dimensionality is "fine-tuned," or rather a consequence of the weak anthropic principle.
Viveka
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### Re: Relativity?

davidm wrote: Mon Oct 30, 2017 11:21 pm Fascinating paper by Tegark on the dimensionality of spacetime. Upshot: only a world of three spatial dimension and one time dimension has sentent observers. So our particular dimensionality is "fine-tuned," or rather a consequence of the weak anthropic principle.
Wouldn't we perceive everything in spacetime in 4-d if we evolved in this universe? Space and time are not spacetime.
Viveka
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### Re: Relativity?

davidm wrote: Mon Oct 30, 2017 10:47 pm
Viveka wrote: Mon Oct 30, 2017 10:36 pm
davidm wrote: Mon Oct 30, 2017 8:10 pm

What is the point of such an experiment? It bears no relation whatever to the world we live in, whereas Einstein's thought experiments DID bear such a relation. A world in which physical objects traveled faster than photons would be completely unintelligible to us. Almost surely it would not be able to harbor life of any kind.
Yeah, I"m sure the Twin's Contradiction has great relevance to our common sense and the world as we know it.
The twin's "contradiction" is neither a contradiction nor a paradox. It is a verifiable prediction of special relativity.

Your "thought" experiment about material objects traveling faster than photons bears no relation to reality and could only be considered as a speculative alternative universe. I've no idea what such a realm would look like, but I'm pretty sure nothing would be alive in it. Maybe uwot would like to speculate.
I'm sure moving at light speed in a ship made of matter is a prediction of special relativity that is verifiable.
davidm
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### Re: Relativity?

Viveka wrote: Mon Oct 30, 2017 11:34 pm
davidm wrote: Mon Oct 30, 2017 10:47 pm
Viveka wrote: Mon Oct 30, 2017 10:36 pm

Yeah, I"m sure the Twin's Contradiction has great relevance to our common sense and the world as we know it.
The twin's "contradiction" is neither a contradiction nor a paradox. It is a verifiable prediction of special relativity.

Your "thought" experiment about material objects traveling faster than photons bears no relation to reality and could only be considered as a speculative alternative universe. I've no idea what such a realm would look like, but I'm pretty sure nothing would be alive in it. Maybe uwot would like to speculate.
I'm sure moving at light speed in a ship made of matter is a prediction of special relativity that is verifiable.
No, just the opposite. It is a verifiable prediction of special relativity that any object with rest mass (i.e., everything except photons) CANNOT move at the speed of ligtht.

You really should try to do some reading and study, maybe take a class, before going on like this.
davidm
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### Re: Relativity?

Viveka wrote: Mon Oct 30, 2017 11:33 pm
davidm wrote: Mon Oct 30, 2017 11:21 pm Fascinating paper by Tegark on the dimensionality of spacetime. Upshot: only a world of three spatial dimension and one time dimension has sentent observers. So our particular dimensionality is "fine-tuned," or rather a consequence of the weak anthropic principle.
Space and time are not spacetime.
Space and time are spacetime.
Viveka
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### Re: Relativity?

davidm wrote: Tue Oct 31, 2017 12:19 am
Viveka wrote: Mon Oct 30, 2017 11:33 pm
davidm wrote: Mon Oct 30, 2017 11:21 pm Fascinating paper by Tegark on the dimensionality of spacetime. Upshot: only a world of three spatial dimension and one time dimension has sentent observers. So our particular dimensionality is "fine-tuned," or rather a consequence of the weak anthropic principle.
Space and time are not spacetime.
Space and time are spacetime.
Then that means that Galilean Relativity and Special Relativity are not opposed. :/
Viveka
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### Re: Relativity?

davidm wrote: Tue Oct 31, 2017 12:15 am
Viveka wrote: Mon Oct 30, 2017 11:34 pm
davidm wrote: Mon Oct 30, 2017 10:47 pm

The twin's "contradiction" is neither a contradiction nor a paradox. It is a verifiable prediction of special relativity.

Your "thought" experiment about material objects traveling faster than photons bears no relation to reality and could only be considered as a speculative alternative universe. I've no idea what such a realm would look like, but I'm pretty sure nothing would be alive in it. Maybe uwot would like to speculate.
I'm sure moving at light speed in a ship made of matter is a prediction of special relativity that is verifiable.
No, just the opposite. It is a verifiable prediction of special relativity that any object with rest mass (i.e., everything except photons) CANNOT move at the speed of ligtht.

You really should try to do some reading and study, maybe take a class, before going on like this.
I already know this. For the sake of the Twin's Paradox, we must assume that we can travel at C. Therefore, it's a wasted thought-experiment in your eyes since it has no true relation to reality.
davidm
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### Re: Relativity?

Viveka wrote: Tue Oct 31, 2017 12:28 am
davidm wrote: Tue Oct 31, 2017 12:15 am
Viveka wrote: Mon Oct 30, 2017 11:34 pm

I'm sure moving at light speed in a ship made of matter is a prediction of special relativity that is verifiable.
No, just the opposite. It is a verifiable prediction of special relativity that any object with rest mass (i.e., everything except photons) CANNOT move at the speed of ligtht.

You really should try to do some reading and study, maybe take a class, before going on like this.
I already know this. For the sake of the Twin's Paradox, we must assume that we can travel at C. Therefore, it's a wasted thought-experiment in your eyes since it has no true relation to reality.
The Twin's (Non!) Paradox does NOT ASSUME THAT THE TWIN IN MOTION CAN TRAVEL AT C! It only postulates (correctly) that in principle, a twin in a space ship can travel at a substantial fraction of c, and then relativistic effects show up.

Please stop. This is becoming even more boring and ridiculous than ken's posts.