# Light and my speed

shankar
if iam traveling along a light beam and if my speed matches (dosent happen,if) can i see the ligth standing still...

Staff Emeritus
Gold Member
No, light will always be measured to have speed c, for every observer, regardless of your speed with respect to other objects.

So if you were able to attain .9999c with respect to the Earth any experiment to measure the speed of light would yield c.

zoobyshoe
Allow me to modify the question
somewhat to satisfy my curiosity
laser beams traveling in space
as parallel as possible. The
photons in these beams are con-
sious and intelligent and they
have eyes. If the photons in one
beam look at the photons in the
other do they seem to be motion-
less or whizzing by at C?

Staff Emeritus
Gold Member
Photons do not know time or distance. To a photon the universe is a point, it takes zero time to traverse it. So they cannot observe antother photon, being as they spend zero time in transit.

zoobyshoe
How is it that crossing the Univer
-se takes 0 time from the photons
perspective when it seems to us
to take trillions, or whatever,
years? Why is the universe a
point to a photon?

Staff Emeritus
Gold Member
Are you familiar with the Lorentz transforms? When your velocity is c, time dilation and length contraction reduce time and distance to nothing. So as far as a photon is concerned, the instant it is emitted it is adsorbed, it has gone no distance in no time.

Edit: Typo

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zoobyshoe
Yes, I'm familiar with the Lorentz
Transformation, and, I see what
you're saying makes sense in light
of them (pun intended).

I'm sure you can understand that
this situation presents as a
to go at 300,000 kilometers a
second, but light perceives its
own travel as instantaneous. This
bothers me.

anations.

-Zoobyshoe

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Staff Emeritus
Gold Member
Perhaps it the precieved speed is in reality a Quantum effect, haveing to do with the Plack Time and Distance. I feel your pain, why if Light sees no time and no distance, do we preceive a finite speed.

Wonders of the universe.

quartodeciman
Once again, it has been forgotten that Lorentz transformations have been set up and derived for observer systems of coordinates with a speed v less than c between them. In order to arrive at the transformation, light must be capable of going from one observer to the other and back again, at any time, according to either observer's clocks. The transformation is not expected to work when v is set to c and the Lorenz factor becomes 1/0. Light itself cannot comprise an observer system under this scheme.

Echo 6 Sierra
Still learning here so help me out fella's. Photons do/don't have mass? If they do, and since they are already at c, why don't they have infinite mass already? If they don't, how can they be captured, stalled, and/or held as I've seen in so many experiments that have been reported as of late?

Does the time dilation and length contraction bit, for a photon, equate to tunnelling(sp)?

E6S

FZ+
Photons do/don't have mass?
Photons don't have rest mass. But they do have energy, which we translate to "relativistic mass".

If they don't, how can they be captured, stalled, and/or held as I've seen in so many experiments that have been reported as of late?
Uh... stalled/held? Which experiments?

The key postulate of relativity is that light travels at c regardless of frame of reference.

Tunnelling is IIRC a quantum phenomenon, due to quantum uncertainty in particle involved.

Echo 6 Sierra
I'm almost positive that I followed a link from this site to a BBC story where a group of Scientists were able to at least "delay" a photon a measurable amount of time. I want to say they were Nederlanders but that part I'm not sure of. I believe either AMES RC or SWRI duplicated it, but then again, I could be completely wrong.

DANG! Not a whole lot of concrete info coming from me nowadays. If I find it would you like a PM or a re-post here?

E6S

Staff Emeritus
Gold Member
Originally posted by Echo 6 Sierra
I'm almost positive that I followed a link from this site to a BBC story where a group of Scientists were able to at least "delay" a photon a measurable amount of time. I want to say they were Nederlanders but that part I'm not sure of. I believe either AMES RC or SWRI duplicated it, but then again, I could be completely wrong.

DANG! Not a whole lot of concrete info coming from me nowadays. If I find it would you like a PM or a re-post here?

E6S

What happens in these experiments is the the photon is absorbed by an atom, and the atom stores the properties of the photon until triggered. It then emits an exact copy of the original photon. The effect is as if the photon was delayed, but waht really happens is that it ceases to exist as a photon while its information is stored in the atom. As long as a photon exists as such, it will travel at c.

CJames
Originally posted by shankar
if iam traveling along a light beam and if my speed matches (dosent happen,if) can i see the ligth standing still...

SWEET work man! You just asked yourself the same question Einstien did before he invented relativity to deal with it. The answer (known before relativity) is that no matter how fast you go, light is always traveling the speed of light faster. You can never see a beam of light standing still. This is precisely why you can never REACH the speed of light, since it's always faster! This mind boggling answer is what leads to time distortion and all that confusing stuff.

FZ+
Janus: from the links he supplied, it looks like Echo etc was referring more to experiments involving the production of BECs, where what you said may not apply. (But then again, I am mostly ignorant as to the nature of Bose-Einstein condensates) In any case, can you (or anyone else) enlighten us?