Why is light so slow?

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Offline Geezer

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Why is light so slow?
« on: 08/12/2011 18:56:42 »
I think we tend to think of light as travelling incredibly fast. However, as anyone who does anything with electronics will tell you, it's really quite annoyingly slow. Heck, it's not even 1000 times faster than commercial airliners. It's almost as if spacetime was a big blob of treacle (molasses).

Why does it have to be so slow?
There ain'ta no sanity clause, and there ain'ta no centrifugal force ćther.

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Offline syhprum

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Why is light so slow?
« Reply #1 on: 08/12/2011 20:26:33 »
Right you have us all on tenterhooks now spill the beans.
I worked in electronics for many years and never had any problem with light moving too slow.
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Offline Geezer

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Why is light so slow?
« Reply #2 on: 08/12/2011 20:47:03 »
Right you have us all on tenterhooks now spill the beans.
I worked in electronics for many years and never had any problem with light moving too slow.

Well, if light travelled a lot faster, presumably electronic signals would propagate a lot faster too.
There ain'ta no sanity clause, and there ain'ta no centrifugal force ćther.

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Offline JP

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Why is light so slow?
« Reply #3 on: 08/12/2011 21:13:47 »
Heck, it's not even 1000 times faster than commercial airliners.

I think you're off by a few orders of magnitude.  Sound ~3E2 m/s, light ~ 3E8 m/s, so light ~ 3E6 faster than sound, and most commercial airliners go slower than the speed of sound.

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Offline Geezer

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Why is light so slow?
« Reply #4 on: 08/12/2011 21:21:32 »
Heck, it's not even 1000 times faster than commercial airliners.

I think you're off by a few orders of magnitude.  Sound ~3E2 m/s, light ~ 3E8 m/s, so light ~ 3E6 faster than sound, and most commercial airliners go slower than the speed of sound.

[:I] Oops! Got me hours and me seconds mixed up! (km/sec v km/hr f=3600)

Anyway, it's still not ALL that fast.

There ain'ta no sanity clause, and there ain'ta no centrifugal force ćther.

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Offline CliffordK

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Why is light so slow?
« Reply #5 on: 08/12/2011 21:22:49 »
Heck, it's not even 1000 times faster than commercial airliners.

What airline have you been flying on?

Mach 1 is 768 mph (although it varies with altitude).
The Speed of Light is 671 Million MPH.

Or...  about Mach 1 MILLION.

If you had 10G acceleration, (98 m/s2), it would take:
299,792,458 m/s / 98 m/s2 / ((60 s/m)*(60 m/h)*(24 h/d))
And, it would take you about 35 days of continuous Mach 10 acceleration to achieve the speed of light.

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Offline JP

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Why is light so slow?
« Reply #6 on: 08/12/2011 21:27:19 »
It strikes me that if you devise some electronic device that runs at roughly the speed of light, its always going to be limited by the speed of light, not matter if it were faster or not.  So long as there is a speed limit, you'll bump up against it.

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Offline CliffordK

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Why is light so slow?
« Reply #7 on: 08/12/2011 21:53:50 »
It strikes me that if you devise some electronic device that runs at roughly the speed of light, its always going to be limited by the speed of light, not matter if it were faster or not.  So long as there is a speed limit, you'll bump up against it.

Of course, there are many ways to phrase the question.

Why are atoms so HUGE?

Hydrogen is about 10-10m in diameter.
A proton is about 1.75 x 10-15m in diameter.

So, if atoms were the size of protons, then you could make your electronics much smaller, and about 10,000 times faster.  So much for nano-technology.

However,
We live in the physical universe.

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Offline yor_on

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Why is light so slow?
« Reply #8 on: 08/12/2011 22:17:58 »
I kind of enjoyed that first definition Geezer. It reminded me favorably of Terry Pratchett, who used some similar definitions.

"Light thinks it travels faster than anything but it is wrong. No matter how fast light travels, it finds the darkness has always got there first, and is waiting for it"

I wonder if Mark Twain ever wrote about light?
=

Can't withhold this one, also from Terry.

"It is often said that before you die your life passes before your eyes. It is in fact true. It's called living."
« Last Edit: 08/12/2011 22:20:22 by yor_on »
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Offline Geezer

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Why is light so slow?
« Reply #9 on: 08/12/2011 23:34:44 »
Er well, see, light only manages to travel about 100mm in one nanosecond, and electronic signals often only manage about one third of that, so they only travel about 30mm in one nanosecond. That means all the propagation delays have to be accounted for in high speed digital systems.

Sometimes you simply can't get from here to there fast enough. Now, if we could only get light to go a bit faster......
There ain'ta no sanity clause, and there ain'ta no centrifugal force ćther.

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Offline CliffordK

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Why is light so slow?
« Reply #10 on: 09/12/2011 00:44:06 »
Sometimes you simply can't get from here to there fast enough. Now, if we could only get light to go a bit faster......
You could try to design the first Neutrino Computer  [;)]

But, I imagine the design of such a machine would be more complicated, and not give you any true benefit.

What is happening is both making everything smaller, as well as making single chips far more complex.

The future of computers is likely to move towards single-chip computers, or single IC computers.  At least combining the Memory and CPU into a single device. 

Another thing that will likely come into play is the use of more dedicated sub-processors.  For example, with SCSI, most of the processing is offloaded to the SCSI controller.  I'm always cussing about my USB drives.  Frequently when I try a big dump from my hard drive to a USB device, it will bring the whole computer to a standstill.  There is no need for that to happen, but many computer specs fail to mention device throughput.

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Offline syhprum

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Why is light so slow?
« Reply #11 on: 09/12/2011 05:48:23 »
I have a SCSI board in my computer to feed my olde worlde HP scanner but it will only work with a 32 bit system.
I grew up with SCSI and like it but it seems to have fallen out of favour.
syhprum

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Offline CliffordK

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Why is light so slow?
« Reply #12 on: 09/12/2011 05:53:45 »
I have a SCSI board in my computer to feed my olde worlde HP scanner but it will only work with a 32 bit system.
I grew up with SCSI and like it but it seems to have fallen out of favour.

SCSI is still used a lot in servers, and the hot-pluggable SCSI RAID systems are pretty sweet.

Unfortunately, it remains quite expensive, and for servers, oddly, it is running a few years behind desktop systems for drive capacity.

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Offline MikeS

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Why is light so slow?
« Reply #13 on: 09/12/2011 07:54:08 »
Why is light so slow?

From its own 'point of view' it travels instantaneously so does not experience time.  We know that gravity dilates time and that space-time is curved or warped.  I imagine that 'curvature' is what slows the speed of light from instantaneous in its 'frame' to a finite speed in any other 'frame'.  That curvature is what we call time.

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Offline Don_1

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Why is light so slow?
« Reply #14 on: 09/12/2011 09:41:59 »
Heck, it's not even 1000 times faster than commercial airliners.

What airline have you been flying on?


Not this one.
If brains were made of dynamite, I wouldn't have enough to blow my nose.

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Offline CliffordK

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Why is light so slow?
« Reply #15 on: 11/12/2011 08:53:25 »
Ahh, I found it.

The Geezer Light
Quote
Researchers have succeeded in reducing the speed of light in a Bose-Einstein condensate to 38 MPH (61 km/h)

At that speed, you could outrun your Pinto's headlights!!!

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Offline Bill S

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Why is light so slow?
« Reply #16 on: 12/12/2011 20:48:40 »
Quote
speed of light in a vacuum, i.e., 186,000 MPH [300,000 km/h].

Its not just Geezer who gets his hours and seconds mixed up. [::)]


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Offline neilep

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Why is light so slow?
« Reply #17 on: 12/12/2011 21:07:00 »
As a firm believer in empirical study I stuck a small torch on a snail.....Observed it for five minutes !

Conclusion. This light moved very slowly.

Glad I could help !
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Offline CliffordK

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Why is light so slow?
« Reply #18 on: 12/12/2011 22:36:02 »
Quote
speed of light in a vacuum, i.e., 186,000 MPH [300,000 km/h].
Its not just Geezer who gets his hours and seconds mixed up. [::)]
Oh,
I see, that came from the article that I had quoted above on the Bose-Einstein Condensate.
Good Catch!!

So, then one must ask if their other units are correct.

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Offline MikeS

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Why is light so slow?
« Reply #19 on: 13/12/2011 07:25:25 »
neilep

Did the snail floresc?

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Offline Geezer

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Why is light so slow?
« Reply #20 on: 13/12/2011 08:17:45 »
Quote
speed of light in a vacuum, i.e., 186,000 MPH [300,000 km/h].

Its not just Geezer who gets his hours and seconds mixed up. [::)]



Well, there you are then. It's obvious that "c" is greatly overrated.

(Thanks Bill!)
There ain'ta no sanity clause, and there ain'ta no centrifugal force ćther.

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Offline CliffordK

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Why is light so slow?
« Reply #21 on: 13/12/2011 08:20:26 »
neilep

Did the snail floresc?

Only the transgenic snails...

Those crossed with fireflies give a new meaning to the speed of light!!!

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Offline Nizzle

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Why is light so slow?
« Reply #22 on: 13/12/2011 08:42:59 »
"c" is something weird isn't it. It's measured in m/s, but at the speed of light, time stands still, so s cannot be other than "0" and we all know that you shouldn't divide by "0". :p


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Offline imatfaal

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Why is light so slow?
« Reply #23 on: 13/12/2011 11:26:10 »
"c" is something weird isn't it. It's measured in m/s, but at the speed of light, time stands still, so s cannot be other than "0" and we all know that you shouldn't divide by "0". :p

Niz - you cannot extend Special Relativity to the local frame of reference of light, we just do not know what happens at the speed of light; massive particles do not go as fast as the speed of light (gran sasso excepted) - and those things that do are weird massless particles (photon, graviton, gluon).  we just cannot say that time is frozen or stopped for photons
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Offline Nizzle

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Why is light so slow?
« Reply #24 on: 13/12/2011 13:53:22 »
Maybe I should be less subtle with jokes and use a capital P in my smileys at the end :P
Roses are red,
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Most poems rhyme,
but this one doesn't

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Offline Bill S

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Why is light so slow?
« Reply #25 on: 13/12/2011 16:36:31 »
Quote from: imatfaal
we just cannot say that time is frozen or stopped for photons.

Presumably, by the same token, we cannot say that something travelling faster than light would travel backwards through time.

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Offline imatfaal

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Why is light so slow?
« Reply #26 on: 13/12/2011 17:31:18 »
Quote from: imatfaal
we just cannot say that time is frozen or stopped for photons.

Presumably, by the same token, we cannot say that something travelling faster than light would travel backwards through time.

If SR holds then something travelling faster than light will seem to contradict causality - where you go from there is anyone's guess.  massive particles cannot travel at light speed or greater, information cannot be transmitted at light speed or greater, and the minimum time between cause at A and effect at B is the distance over light speed .  boring and unimaginative ...
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Offline yor_on

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Why is light so slow?
« Reply #27 on: 15/12/2011 09:39:09 »
No, although I fully agree on your conclusion, I don't think it's entirely true to say that SR forbids it Imatfaal, even though FTL creates all kind of weird implausibilities. I mean, you and me both doubt it, especially if formulated as a way to travel 'backward' in time, to meet/shoot 'yourself', etc.

Special relativity uses a constant 'c'. That's what defines us living here, but it doesn't say anything about what's on the other 'side' of 'c'. This 'warp space' some dreams of may, probably even, exist, but a translation from its 'reality' to ours 'reality' I very much doubt to exist.

To me it's like a quantum computer 'inferring' answers to questions that may not even have been stated, according to some interpretations. It might be possible but, I think not.

"When Einstein wrote down his postulates for special relativity, he did not include the statement that you cannot travel faster than light.  There is a misconception that it is possible to derive it as a consequence of the postulates he did give.  Incidentally, it was Henri Poincare who said "Perhaps we must construct a new mechanics [...] in which the speed of light would become an impassable limit."  That was in an address to the International Congress of Arts and Science in 1904—before Einstein announced special relativity in 1905.

It is a consequence of relativity that the energy of a particle of rest mass m moving with speed v is given by

          E = mc2/sqrt(1 - v2/c2)

As the speed approaches the speed of light, the particle's energy approaches infinity.  Hence it should be impossible to accelerate an object with rest mass to the speed of light; also, particles with zero rest mass must always move at exactly the speed of light, since otherwise they would have no energy.  This is sometimes called the "light speed barrier", but it is very different from the "sound speed barrier".  As an aircraft approaches the speed of sound it starts to feel pressure waves which indicate that it is moving close to the speed of sound, and before the existence and effects of these waves were well understood, they destroyed several aircraft in the mid 20th century; hence the old name of sound "barrier".  In fact, with more thrust and the right aerodynamics, an aircraft can certainly pass through the sound barrier.

The situation is different for light.  As the light speed barrier is approached (in a perfect vacuum) there are no such waves according to relativity (destructive or otherwise).  Moving at 0.999c is just like standing still with everything rushing past you at −0.999c.  Particles are routinely pushed to these speeds and beyond in accelerators, so the theory is well established.  Trying to attain the speed of light in this way is a matter of chasing something that is forever just out of your reach.

This explains why it is not possible to exceed the speed of light by ordinary mechanical means.  However, it does not in itself rule out FTL travel.  It is really just one way in which things cannot be made to go faster than light, rather than a proof that there is no way to do so.  Particles are known to decay instantly into other particles which fly off at high speed.  It is not necessary to think in terms of the particles' having been accelerated, so how could we say that they could not go faster than light?  What about the possibility of particles that might always have been moving faster than light, and which might be used to send information if they can be detected without ever slowing down to less than the speed of light?  Even if such "tachyons" don't exist (and we don't believe that they do exist), there may be ways of moving matter from A to B faster than light is able to travel from A to B by the usual route, but without anything having to go at a FTL speed locally." From Is Faster-Than-Light Travel or Communication Possible?

It's the translation between 'reality's' I doubt. Because if that's possible, then the next step is Lorentz transformations assuming to translate into a 'same global reality' for all of SpaceTime. Then we will have only locality left, with a new question becoming what the he* that will mean in understanding how we ever can percieve a same 'arrow of time'. But I have my own reasoning there of course.
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Offline yor_on

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Why is light so slow?
« Reply #28 on: 15/12/2011 09:53:25 »
Hmm rereading, are you stating SR to be boring and unimaginative? Then we might be of two minds here :) I find it the most imaginative approach existing myself, that and GR is the most impressive framework existing still, a hundred years after its formulation.
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