From: ccasm@cc.newcastle.edu.au
Subject: Re: Elapsed Time near c (was Re: Q&A on Extraterr
Organization: University of Newcastle, AUSTRALIA
Date: Wed, 22 Jul 1992 03:17:39 GMT

In article <1992Jul21.002755.17265@news.eng.convex.com>, swarren@convex.com (Steve Warren) writes:
> Nope.  The fact is that nothing can travel faster than light, in any reference
> frame.  If it wasn't for the foreshortening effect, you would literally see
> the universe passing by faster than the speed of light.

I disagree. One cannot see anything passing faster than the speed of light, but
that does not stop objects travelling faster than c.

The speed-of-light is the speed of that light transmitted or reflected by any
object. It is a constant, no matter what the speed of the object is -
whether it is stationary, moving at 100 mph or 186,000 mph (all relative to
the observer on Earth). Like watching a car - stopped or going.

BUT LIGHT SPEED IS INDEPENDENT from THE SPEED OF THE OBJECT.
                   ^^^^^^^^^^^                     ^^^^^^

If an object travels SLOWER than the speed of light it would be observed as
being `where it is'. BUT it is only NEAR where it is (the difference is so
little). It takes time for the light to travel to our eye, during which the
object has moved on. But this is not obvious at relative slow speeds such as
occur in everyday life (like catching a ball or watching a car). This is
"convenient" else we would be run over by a car that was not there at the
time. :-)
 
If an object travelled FASTER than the speed of light, it would not be observed
as being where it actually is. This would not be significant until it travelled
at much higher speeds than light. So what? Sometime after it stopped its image
would catch up with it. Thus the object would not appear to have exceeded the
speed of light, to the stationary observer (who is only observing the image). 
Bad luck if the object is travelling straight at you. All that would be seen is
a black hole until well after it passed (or hit) you.

Compare this to the speed of sound. We can see an event such as a gunshot
before hearing it. The speed of the bullet is not effected by the observation.

To the observer aboard the object/craft, other objects around it would appear
to be the ones moving. Again they would not appear to be travelling at above
the speed of light but in fact they would not be where they appear to be.
Collisions would be unavoidable if navigation was based on sight. Computers
could adjust for known objects, but uncharted small particles would be
disastrous unless the craft was protected by a "forcefield", as they would hit
before they were seen. Using some means of detection other than light, it might
be possible to navigate ad-hoc at above-light speed. Is there any such method?
An expendable "pathfinder" might be possible - send another craft on the same
path slightly before your flight. The distance (time?) between the two flights
would be the reaction time of the second craft to navigational changes. I don't
think this will work. What if you ran into another pathfinder?

Inside the craft the observer would not notice any difference as all objects
would be travelling at close to the same speed, including the observer. However 
movements needing timing, such as eye-hand coordination, would they be clumsy?

Looking out of the craft the observer would in fact be looking forward/back in
TIME. Looking to the rear while overtaking the light that had been reflected
from the Earth the observer would see into the past. Or would he see nothing -
a black hole? Looking forward you would see into the future. All these
observations are of course relative to the observer on earth.

This thought exercise has been fun, but the practicalities are another thing.
How does one get all those molecules to accelerate enormously at the same time.
This is necessary if the craft is to avoid either dragging its tail or
squashing its nose. Or what if the destination is no longer there - how would
you know until you were under way.

Personally I don't see the point of travelling at these speeds. We don't need
to send humans anywhere around the universe - we can build observers for us,
but they can only communicate at c or less, unless the message is "attached" to
an object travelling above the speed of light. Our biology is not designed for
it. The Earth is our only home for some time, I'm afraid.

Big Al


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