Space and time at the speed of light

wrote:

I seem to recall reading somewhere that if a photon or, for that matter, any sentient being
travelling at the spped of light would experience a complete contraction of space and time.
That is a photon would be "everywhere in the universe" at the speed of time. I know I am
putting this badly, but unfortunately this is the best I can do. Can anyone care to
comment on this. What WOULD be the experience of time and space for someone travelling at
the speed of light??

You've answered your own question. From the point of view of a photon
time is infinitely dilated, so it experiences no delay between
leaving point A and arriving at point B. An alternative description
of the situation is to say that to a photon the universe appears
infinitely compressed, becoming a plane perpendicular to its
direction of travel -- so any segment of its path is infinitely
short. Of course a sentient being travelling at the speed of light
must have a means of leaving all of its mass behind!

A nicely illustrated description of the relativistic effects
experienced by high-speed (but not quite light-speed) observers, from
the Usenet Physics FAQ, may be found at

http://tinyurl.com/hvk7.

--Odysseus

Hi thx nb At light speed you would be every where at once. At light
speed you would weigh as much as the universe,and your inertia would be
infinite. However this is not reality,and that is why Einstien gave us
the SR theory. Electrons have been pushed to 99.999999999 of light
speed. They are made 20,000 times heavier. A greater accelerator
can make them go faster(add another 9) but never can an electron go at
the speed of a photon. Since objects foreshorten in the direction they
are moving,at close to light speed you would look like a playing
card,and be dead. Here you see fast accelerating motion,and gravity
being equivalent,for going into a blackhole you would be stretched out
like spaghetti Einstien told all this to us going on a 100 years ago.
Bert

In message 3f200ade@webster, writes

Thanks very much. The URL was very helpful. I take it that this is the
reason why certain
elementary particles that have very short lifetimes, but are travelling
at relativistic speeds,
are actually detected on earth. In particular, John Walker at CERN
talks about the detection of
an "Oh my God" particle that should have never been detected on earth,
but since it was
travelling at very high speeds made it all the way down.


If that's the one I think it is, it's a different problem and still
mysterious. Some cosmic rays have so much energy they should be
interacting with the cosmic microwave background and losing the energy.
So either they come from quite close by - millions of light years, not
billions - or there is some new physics going on.
But you're right; we see mesons in cosmic rays because of time dilation.
--
"Roads in space for rockets to travel....four-dimensional roads, curving with
relativity"
Mail to jsilverlight AT merseia.fsnet.co.uk is welcome.
Or visit Jonathan's Space Site http://www.merseia.fsnet.co.uk

Jonathan Silverlight wrote:

If that's the one I think it is, it's a different problem and still
mysterious. Some cosmic rays have so much energy they should be
interacting with the cosmic microwave background and losing the energy.
So either they come from quite close by - millions of light years, not
billions - or there is some new physics going on.
But you're right; we see mesons in cosmic rays because of time dilation.

I'm not sure whether it's a meson or some other particle, but I
believe the time-dilation effect was first observed in short-lived
'debris' from collisions of cosmic rays with nuclei in the
atmosphere. We don't usually have any way of knowing how far or how
long particles coming 'straight from deep space' have travelled.

--Odysseus

Odysseus wrote:
wrote:

I seem to recall reading somewhere that if a photon or, for that matter, any sentient being
travelling at the spped of light would experience a complete contraction of space and time.
That is a photon would be "everywhere in the universe" at the speed of time. I know I am
putting this badly, but unfortunately this is the best I can do. Can anyone care to
comment on this. What WOULD be the experience of time and space for someone travelling at
the speed of light??

You've answered your own question. From the point of view of a photon
time is infinitely dilated, so it experiences no delay between
leaving point A and arriving at point B. An alternative description
of the situation is to say that to a photon the universe appears
infinitely compressed, becoming a plane perpendicular to its
direction of travel -- so any segment of its path is infinitely
short. Of course a sentient being travelling at the speed of light
must have a means of leaving all of its mass behind!

A nicely illustrated description of the relativistic effects
experienced by high-speed (but not quite light-speed) observers, from
the Usenet Physics FAQ, may be found at

http://tinyurl.com/hvk7.

--Odysseus

Thanks very much. The URL was very helpful. I take it that this is the reason why certain
elementary particles that have very short lifetimes, but are travelling at relativistic speeds,
are actually detected on earth. In particular, John Walker at CERN talks about the detection of
an "Oh my God" particle that should have never been detected on earth, but since it was
travelling at very high speeds made it all the way down.

thx nb