PDA

View Full Version : Speed of light- why?

2006-Jan-06, 10:46 AM
I was wondering why is the speed of light about 300,000 km/s why isnt it slower or faster? why isnt it 1,000,000 km/s? Also when you compare the speed of light to the distances between galaxies you would see that the speed of light is very S L O W.... why so slow?

SolusLupus
2006-Jan-06, 10:58 AM
Because it's proof that God hates us all.

SolusLupus
2006-Jan-06, 11:09 AM
Seriously, though, this is a question that seems impossible to really answer without getting theological...

2006-Jan-06, 11:31 AM
i challenge a scientist to answer my question :)

Relmuis
2006-Jan-06, 11:39 AM
It comes to (nearly) 300,000 km per second because we chose a certain length for our (kilo)meter, and a certain duration for our second. so, there is probably not something very mystical about the number 300,000. A priori, the speed of light might have been zero, finite or infinite; it comes out finite.

There are however so-called dimensionless constants, combinations of things like the speed of light, Planck's Constant, the Gravitational Constant, Boltzmann's Constant, and such, which do not have the character of a length, a speed, a charge, a mass, a temperature, a force, or anything else. Here the numeric values are independent of our system of units (would have been the same if we had taken inches instead of meters, hours instead of seconds, degrees Rankine instead of degrees Kelvin, etc.) And one may well wonder where these numerical values come from.

2006-Jan-06, 12:02 PM
Anything beyond 13 billion light years from earth is invisible to us right? Because its electromagnetic radiation hasnt reached us yet. So does that mean anything beyond 13 billion light years has no affect whatsoever on earth? No radiation, gravity, nothing?

worzel
2006-Jan-06, 12:15 PM
In geometrized units the speed of light is 1. Apparently this (and a few other things like the gravitational constant being set to 1) makes all the relativistic equations much neater.

EsquireJ
2006-Jan-06, 12:37 PM
it is better to think of it as we chose the speed of light rather than light choosing its speed

desertmonk
2006-Jan-06, 01:24 PM
I think the question at hand is not why is the speed of light 186,000 miles per second or whatever it is, but why do electromagnetic waves travel at the speeds they travel at. So, it isn't a question of numerical values, but the physics behind the phenomenon of EM waves. I don't know the answer myself either.

rahuldandekar
2006-Jan-06, 01:57 PM
It's just a question of constants, and why they have the values they do. Maybe one day the Theory of Everything will explain the constants' values.

Sp1ke
2006-Jan-06, 04:08 PM
Anything beyond 13 billion light years from earth is invisible to us right? Because its electromagnetic radiation hasnt reached us yet. So does that mean anything beyond 13 billion light years has no affect whatsoever on earth? No radiation, gravity, nothing
No radiation, no light. And probably no gravity (assuming gravity effects propagate at the speed of light).

2006-Jan-06, 04:44 PM
Thanx for the comments, though I dont think my question is answered yet. Desertmonk was right, I am not saying why the value is 300000 km/s, I am saying why is the speed what it is why isnt it higher or lower? what makes it stop going any faster?

ToSeek
2006-Jan-06, 05:47 PM
Maxwell's equations include two values that represent the electrical permittivity and the magnetic permeability of the material that electromagnetic radiation is passing through. The larger these values, the slower the electromagnetic radiation. There seems to be no explanation of why these values aren't zero in a vacuum, though the explanation may lie in quantum physics and in particular with the virtual particles allowed by quantum physics.

Eric12407
2006-Jan-06, 06:44 PM
Hi Specialist ...

I was asking some laymans questions in another thread ""Light from a distant source".

The thing about the speed of light that is really weird is that in the light world transmission is instantaneous and in our world as you point out it is slow ... that doesn't make any sense ...

So what we have are 3 different worlds with different rules ...
1. The light world
2. The world of classical Newtonian physics
3. The quantum world ...

Titana
2006-Jan-06, 08:45 PM
I was wondering why is the speed of light about 300,000 km/s why isnt it slower or faster? why isnt it 1,000,000 km/s? Also when you compare the speed of light to the distances between galaxies you would see that the speed of light is very S L O W.... why so slow?

As i have read many times, it is not known why the speed of light has the specific value that it does. Why it is not more or less then 300,000 km/s is a mystery. We can also question other quantaties that are constants such as mass of a proton or the charge of an electron. There are cetain things in nature that have set values, but i think it is not known why they have the exact value that they do.

Titana.

Blob
2006-Jan-07, 03:00 AM
Hum,
it could be that photons are comprised of special tiny vibrating fundamental super strings (actually "branes").

The string is perhaps vibrating internally at a certain frequency or speed, (the speed of light), any faster and they will divide or break into two strings.

So that we see that the underlying `fabric` of space-time has a built-in speed limiter.
i.e.. The illusion of particles moving through space-time (which is really just information jumping from string to string) cannot move faster than the internal vibrations can travel across the string to another string.
http://en.wikipedia.org/wiki/String_theory

or not.

Ken G
2006-Jan-07, 09:05 PM
Although this is an insightful reply about the profundities of string theory, note it only pushes the question back one level, to why do the strings have these vibrational properties? I think we must accept that all chains of "why" questions must ultimately end in "just because". Note also there are two aspects of the speed of light question. One is why is the speed what it is, which is really a question about relative speed (absolute speed has no meaning, only relative to some standard). So the question is really, why is light so much faster than you or I can run? That might come down to the anthropic principle-- if it weren't, our type of life might be impossible.
The second question that has also been addressed already to some degree is the question of why is the speed of light not infinite? Well, there isn't any particle that could move infinitely fast because the physical world probably couldn't handle infinities. However, the c that appears in special relativity could have been infinite, and light could have had a finite rest mass and a finite speed. That would simply return us to Newtonian physics, but didn't happen to be right. Why? Just because.

Blob
2006-Jan-07, 09:24 PM
Hum,
yeah,
i agree it just moved the question down one level,
But my proposition also subtly transformed the `speed` into a `tensile strength` property that a superstring could withstand..

Just because, that is the properties of a super string...

<end hologram>
But, i should add that all this is really getting into the realms of philosophy, without any `observational science` behind it... </end hologram>

PhantomWolf
2006-Jan-08, 02:35 AM
Anything beyond 13 billion light years from earth is invisible to us right? Because its electromagnetic radiation hasnt reached us yet. So does that mean anything beyond 13 billion light years has no affect whatsoever on earth? No radiation, gravity, nothing?
In theory. Since we don't have a telescope that can see that far back yet we don't honestly know.