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Why is the speed of light?

by rogerp
Tags: light, speed
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exponent137
#37
May11-07, 08:26 AM
P: 287
Wilczek's article (I think, I need to read it again after few years) does not touch dimensionless mpl, lpl and tpl. I think that this is the main problem of duff's ideas.


So my article and Okun's article (in trialogue) are in contradiction to Wilczek's article.

Other will follows.
regards
rbj
#38
May11-07, 03:39 PM
P: 2,251
Quote Quote by exponent137 View Post
Wilczek's article (I think, I need to read it again after few years) does not touch dimensionless mP, lP and tP. I think that this is the main problem of Duff's ideas.
lessee, the title of the Wilczek article that i referred to is something like "Scaling Mount Planck". i think that it obviously has something to do with mP, lP and tP (the base Planck units). i think he makes and supports the same point of Duff (and Barrow quoted below), that it is the dimensionless quantities that matter. We measure time, length, and mass against some like-dimensioned standards. We do not measure anything without such comparison.

again, i am saying mP is only as dimensionless as any other mass. if you are expressing a mass m in terms of the Planck mass as m/mP, that is a dimensionless value. and the Planck mass expressed as such is the dimensionless 1.

So my article and Okun's article (in trialogue) are in contradiction to Wilczek's article.
i'm more confident of what Wilczek and Duff and John Barrow and John Baez (and practically any other physicist that has written about this on some blog) say about this than what you are saying about it. much more confident.

from Barrow:

[An] important lesson we learn from the way that pure numbers like α define the world is what it really means for worlds to be different. The pure number we call the fine structure constant and denote by α is a combination of the electron charge, e, the speed of light, c, and Planck's constant, h. At first we might be tempted to think that a world in which the speed of light was slower would be a different world. But this would be a mistake. If c, h, and e were all changed so that the values they have in metric (or any other) units were different when we looked them up in our tables of physical constants, but the value of α remained the same, this new world would be observationally indistinguishable from our world. The only thing that counts in the definition of worlds are the values of the dimensionless constants of Nature. If all masses were doubled in value [including the Planck mass mP] you cannot tell because all the pure numbers defined by the ratios of any pair of masses are unchanged.


Barrow does not include G in that, but the principle is the same. It's the dimensionless quantities that we measure and even perceive. Our perception of length is normalized to the ballpark size of us. Our perception of quantities of time has something to do with how fast we think. Our perception of mass is in comparison to the masses of things we commonly deal with which is in the same ballpark as the masses of us.

It's only the dimensionless parameters of the universe (there are currently thought to be 26 of them) that ultimately matter. variation of the dimensionful parameters (like G or c or h or e) are all conflated with whatever anthropometric units we choose to think of such parameters in terms of. the only way to remove such parochial anthropometric dependence is to express all such quantities in terms of some defined "Natural units". when you do that, the expressions of such mass, time, or length, are dimensionless.
birulami
#39
May14-07, 04:06 PM
P: 148
Quote Quote by rogerp View Post
Hi

I'm a confused layman, and was hoping to get some answers to the question: why is the speed of light? That's not a typo - I mean, why is it what it is?
.
Consider one of the very first computer games, http://en.wikipedia.org/wiki/Pong. I don't really know whether the "ball" had a fixed speed or could go faster too, but just consider it always had a fixed speed. Now you are trapped in the 2D world of Pong and want to build a clock. What comes to mind in this confined world is to count how often the ball goes back and forth. Nice clock. Now you start measuring the speed by looking at how far the ball goes within N clock ticks. Sounds silly? Bear with me a moment longer.

The next version of the game allows the outside players to change the speed of the ball. But you keep measuring speed with your click clicks. Would you notice a change of speed. Of course not. During N clock clicks, the ball still goes the same distance. For you the speed did not change.

What has this to do with your question? Just think of how the most accurate clocks are made. They rely on electromagnetic oszillations, as far as I know, exactly what light is too. So if light would slow down or speed up (for whatever reason), your clocks would likely suffer the same influence and slow down or speed up respectively. Consequently you would not be able to measure a change in the speed of light. And don't think you might 'feel' it. Your whole body chemistry relies on the same electromagnetic phenomena, so it would slow down or speed up in sync.

Personally I believe that this is exactly what special relativity describes with regard to time.-)

Harald.
gilowoskian
#40
Aug20-08, 01:24 AM
P: 1
Ok so i was wondering. If it were possible to travel faster then the speed of light wouldn't you just disappear, and if this was true couldn't there be things out there that travel faster then light but we just cant see them to know they exists?
cristo
#41
Aug20-08, 02:29 AM
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Quote Quote by gilowoskian View Post
Ok so i was wondering. If it were possible to travel faster then the speed of light wouldn't you just disappear, and if this was true couldn't there be things out there that travel faster then light but we just cant see them to know they exists?
It is impossible for a body with mass to travel at, or faster than, the speed of light.
Chronos
#42
Aug20-08, 10:40 PM
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Tachyons are entities theorized to travel at superluminal velocites. They are permitted to travel at any speed greater than c, but never equal to or less than c [pretty weird].
Dick
#43
Aug21-08, 12:01 AM
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Good news. You can have tachyons in various versions of string theory. Bad news, if you have a tachyon, it means you have a PROBLEM. You'd better get rid of it somehow.


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