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Q: physics ( No Answer,   13 Comments )
Subject: physics
Category: Science > Physics
Asked by: neverenoughtime-ga
List Price: $2.00
Posted: 27 May 2006 23:25 PDT
Expires: 26 Jun 2006 23:25 PDT
Question ID: 732978
I can't stop thinking about this.  If i travelled away from the Earth
at exactly the speed of light (let's pretend we can travel at light or
faster speeds)will my view of the earth always be the same (no change
in cloud formations or sunlight.  So if this is correct then if a
travel away from the earth at faster than light, then would i begin to
see the Earth of my past.  I am talking only here about what i can see
not what the actual state of the earth is.

I can't think why this experiment would not....can you?
There is no answer at this time.

Subject: Re: physics
From: elids-ga on 28 May 2006 07:21 PDT
Not really, while you are traveling faster than the speed of light the
light that left the earth would not be able to ?catch up? with you.
So, you would not see the earth at all. When you lower your speed to a
slower than light speed the light that left the prior to your
departure would be able to catch up with you and you would see it as
it was prior to your departure but always moving forward.
Subject: Re: physics
From: frde-ga on 28 May 2006 09:38 PDT
If you could teleport yourself to somewhere 100 light years away
- then you would see the earth as it was 100 years ago
Subject: Re: physics
From: myoarin-ga on 28 May 2006 10:02 PDT
Ah, Elids, but I think you would see the earth (forgetting everything
else involved), catching up with and passing light from earth that
started before you left, if you (could) move faster than the speed of
light, seeing the reverse of cloud development, for example.  If this
were so, then I expect that Neverenoughtime is right:  traveling at
the speed of light, you would be traveling along with an unchanging
image of the earth.
Subject: Re: physics
From: elids-ga on 28 May 2006 10:53 PDT
Hmm well you are correct if traveling faster than light and looking
away from earth he would catch up with the light that left before he
did and in fact see the earth going backwards in time. But if he is
looking at earth he would see nothing as light wouldn?t be able to
catch up with him.

Good point Myoarin.
Subject: Re: physics
From: mechted-ga on 28 May 2006 14:58 PDT
If you were traveling at the speed of light, you would see the earth
at a single instant in time. Traveling faster than the speed of light
would allow you to see the earth in your past. It's not a problem of
the light 'catching up' with you, it has already left. It's a matter
of you 'catching up' with the light.

However, there is only so much light at each distance from the object
being viewed (earth). Traveling at the speed of light would only allow
you to view the Earth for the instant that you reach light speed. The
information would be used up and, since you are moving at the pace of
the information, you would not recieve any more until you accelerated.

All this forgoing the fact that traveling at the speed of light would
require infinite energy and completely stop time for the travelers.
Subject: Re: physics
From: mathisfun-ga on 29 May 2006 22:31 PDT
Just a side question, but would you have to be transparent for this to
work (if it were possible)?
Subject: Re: physics
From: mathisfun-ga on 01 Jun 2006 00:07 PDT
I agree with elids that the only way it could work is if you were
looking away from Earth, but even then you would also be seeing all
other things in the direction of your movement at incresed time, as
well as the earth in reverse time, so I'm not sure exactly what you
would end of seeing.  However if you were facing the earth I think the
problem lies not in the ability of light to catch up but rather (even
if you were transparent) the light would not be able be focused by
your lens and reach your optic disc for you to be able to
see/comprehend it.
Subject: Re: physics
From: oliverisfat-ga on 01 Jun 2006 12:52 PDT
What is meant by "traveling the speed of light" or "traveling faster
than the speed of light?"  Assuming that this is meaning from the
earth's reference frame, you get a paradox (explaining using
Einstein's postulates why this is impossible as opposed to using
relativistic energy).  If you are going the speed of light, then you
are in the photon's rest frame.  However, going any speed, by the
postulates set forth for relativity, we can say the light will be
traveling the speed of light.  So, if you are going the speed of
light, somehow light traveling along with you is going the speed of
light with respect to you.  So basically, relativity falls apart at
these speeds.  That is why Star Trek is stupid.
Subject: Re: physics
From: epidavros-ga on 05 Jun 2006 03:40 PDT
Unask the question.

The problem with hypothetical discussions about things that cannot
actually occur is that the hypothetical conclusions are meaningless.

The speed of light (that is, the speed of any zero rest mass particle
- it applies to things other than photons) is the same for all
observers, however they are moving relative to one another. The first
measurement to indicate this was carried out famously by Michelson and
Morely in 1881 and 1887.

Because this is the case, it is impossible for anything in nature to
exceed the speed of light. As you supply energy to a particle to
accelerate it towards the speed of light, instead of all of the energy
going to speed it up, some of it causes its mass to increase. This
effect is immeasurably small at low speeds, but very important as you
get close to the speed of light.

The relationship between mass and energy that this implies is given by
the most famous equation in physics:

E = m c (squared)

So as you cannot ever exceed the speed of light you cannot reach parts
of the universe in which you would be looking back at the earth as it
was before you left - they are simply inaccessible.
Subject: Re: physics
From: the_iman-ga on 07 Jun 2006 19:36 PDT
hay did u realise if we travel at speed of light we cant see the earth
as the light wont be able to catch up 2 us ever unless we slow down
and stop also we can never travel at speed of light as our matter will
become will become unexisting.
only way to travel at or faster than speed of light it to teleport
Subject: Re: physics
From: rising_iceberg-ga on 10 Jun 2006 03:53 PDT
hey man i think what u r sayin is perfectly correct ur view will kind
of halt at that coz whatever new is happening at earth is not reaching
you in fact moving at the speed of light will disable ur ability to
know about the earth coz no means of communication will work for u coz
the fastest info can be transmitted is through encryption on EM waves
which also propagate at the speed of light...
yeh u know something i used to think the same thing when i was in 9th
grade...gud to see memories refreshed...
Subject: Re: physics
From: rising_iceberg-ga on 10 Jun 2006 03:58 PDT
hey epidavros pray dont try to extinguish the flame of curiosity man
would ne'er have furthered had he not wondered...also i believe
neverenoughtime realises your point when he states:"let's pretend we
can travel at light or
faster speeds".so thereis no need to unask the question...thx bye
Subject: Re: physics
From: kampator-ga on 10 Jul 2006 00:59 PDT
Actually, though it's physically impossible to travel at the speed of
light, you can consider it as a limit case.
In this case, the speed would 'aproach' lightspeed.
Actually, mechted mentioned an important thing, but didn't mention the
implications. When you travel faster, time (relative to the object to
which you compare your speed) will slow down, stopping if you reach
light speed. This means that there will be no time for you to see the
earth, or experience anything while you are traveling. This also means
that when you stop, no time will have passed, and you will have
experienced an instant translocation, or 'teleport'. For an observer
on earth however, it will have taken time.

So if you plan on traveling at light speed, there will be no possible
way to stop (no time to press a button, and a timer won't run). But
don't worry, you won't notice any of it.

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