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Q: speed of light, why not? ( Answered,   3 Comments )
Subject: speed of light, why not?
Category: Science > Physics
Asked by: chefmarius-ga
List Price: $10.00
Posted: 17 Mar 2006 13:59 PST
Expires: 16 Apr 2006 14:59 PDT
Question ID: 708533
I'm no scientist, but what I would like to know is this. As far as I
know Einstein "proved" that u cannot reach the speed of light, u can
only approach it,I think its "c"  now, speed of light equels  300 x 10
to the power of 6. why cant we go faster than that, why is it
IMPOSSIBLE? Is it not just technology that is keeping us back? I know
that they say we will be as flat as you can possibly get it, but if
you accelerate slowly and eventually pick up the speed, and combined
with depresserization, we will be okay? but appart from that, what is
physically keeping us from going past 299 792 458m.s? Technology? I
think so!! pls explaine why not!!
Subject: Re: speed of light, why not?
Answered By: hedgie-ga on 17 Mar 2006 20:40 PST

This is a 'Frequently Asked Question', 
and also 'Frequentl Miss-answered Question'
and there is a reason for that:

Before we can ask 'why is it?' we have to understand 'what it is'.

Speed of light is not as simple as let's say speed of car on a freeway,
People tried for a centuries to  measure it, and then few more centuries
to understand the results.

Here is a brief outline of that history and an one instrument which can measure it.

There is more on the history bellow, under heading "Phase and Group Velocity".
In the vacuum (in the outer space) these two velocities are same, so let's for
now take this more simple case of speed in the vacuum:

It is not problem of technology.
The analogy with the 'sound barrier' which was proposed here
does not apply.

The limit on the speed of light comes from geometry. It is a bit like saying

'you cannot make a triangle where 'sum of angles' is more than 180 degrees.

And you say 'why not?' and take a piece of paper and draw different triangles
and (within the precision of measurements) it always adds to 180 degrees.

Then you study a bit more about geometry, your will even understand why it is so.

Then you may study even more geometry, you find it does not have to be so:
You draw a triangle on a sphere (a globe) and it  will have more then 180 degrees
(e.g. two points on equator and one at the pole).  That because the surface of the 
sphere is curved, and the usual 'plane geometry' does not apply too well. 

If the curvature is small, like surface of the Earth has, then plane geometry can
be used in most cases. Similarly, when speed of the objects in some
experiment is relatively
small (compared to the c) then 'usual geometry' (we call it E3 =
Euclidean three dimensional)
can be used. When high speeds are involved, another geometry (M4 =
Minkowski space-time) is
can help to understanding the results. The limit on the speed of light
is a result of the
way we apply this geometry to the experimental results (so called
'interpretation of the theory').

Because people ignore this simple fact, fact that some measurements,
some statements
 only make sense within within that geometry M4, we often read, even
hear, lot of nonsense
like : You would become flat, and overweight, and time will slow to a crawl ...
if you would try to move at such a high speed. 

That is a nonsense. In fact, I am moving near to the speed of light right now,
 and I am too flat. So are you, moving at very high speed. Whole planet Earth
is moving at near speed of light relative to some quasars.You can  see
 their pictures here:

and read about them here:

The current record Quasar has a redshift, z = 5.5  (that is very close
the speed of light).

They are very far from us, and move away from us very fast. Or, same thing,
we are far from them, and we move fast away from them.

We are not particularly flat and fat, but may we look  so, when
observed from a quasar,

To 'move at near speed of light'  as not a state of a body - like being hot.
Velocity is a relative concept, concept which helps to organize and understand
the measurementswe can make and signalswe are getting.

To understand that, requires to pick up a book on relativity and read it. 
It is worth it. Some easy books on the topic  are recommended here:

Before we can ask 'why is it?' we have to understand 'what it is'.


"Phase and Group Velocity

There are other less well known aspects of light velocity that are
absolutely crucial to understanding the significance of these recent
faster-than-light experiments. There are actually different types of
velocity that reveal themselves depending on which feature of light is
being examined"

Hope ths helps - rating appreciated.   hedgie
Subject: Re: speed of light, why not?
From: kingal-ga on 17 Mar 2006 14:22 PST
The formula for mass is given by m = m0 / sqrt(1-v^2/c^2), where m0=
rest mass, v=velocity, and c=speed of light. You can see that as v
approaches c, m approaches infinity, so you would require infinite
energy to reach the speed of light.
Subject: Re: speed of light, why not?
From: i_know_everything-ga on 02 Aug 2006 13:31 PDT
tachyons predicted by general relstivity goes faster then c but
nothing can ever travel AT c (except for photons) (in a vaccum).
Subject: Re: speed of light, why not?
From: martin33-ga on 04 Aug 2006 21:24 PDT
the faster you move the more you weight... and you need more energy to
keep 300000km/s you would just need too much energy
(infinite - as kingal said already).

At least according to Einstein's Theory of relativity.

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