Wesley Clark Support Warp Drive, Time Travel

Er, they are the same thing. Depending from where you are looking.


Yes you can witness someone going back in time so long as they are traveling
away from you faster than the speed of light. For Example:

We see the light of Alpha Centauri now, as it appeared 4.4 years ago. We see
the light reflected off out own Earth as it appears just about now. Now if a
spaceship were to travel from Earth to Alpha Centauri so fast that we could
follow it with an arbitrarily powerful telescope and see it pass Alpha Centauri
in the next minute, we are actually witnessing something traveling back in
time. The ship is not traveling into our own past, but into Alpha centauri's
past. Since we can't see Alpha Centauri's present, that star's past cannot
affect our own past so long as that past is less than 4.4 years ago. If that
starship where to turn around and head back toward us at that same speed, it
would disappear and we'd never see it again. Perhaps in another timeline that
ship would appear out of nowhere with no explaination as to its origin, but
we'd never see that ship again. There's no way to prove that anything could
travel into our own past, since any attempt to do so would change the present
and we'd would not be here to witness it.

Person A goes back in time and shoots President Kennedy from the Grassy
Knoll,
Person A is then the only person with the memory of President Kennedy _not_
being
shot on that day.

But the people he left behind in his own timeline will never see him again, as
far as they are concerned, his mission failed, since clearly they could see
that John F. Kennedy was never shot. Just as if we sent someone to go kill
Hitler, that mission would fail and we'd never see that time Traveller again.
That is how you maintain chronilogical consistency.

Luckily Person A remembered to take with him a DVD containing a complete
collection
of all interviews from the former future to show Person's B &c. as proof.


They might conclude that by random chance a cloud of material in outer space
suddenly coalesced for form him and the evidence of that alternate future. The
probability is the same. We have no received all that many visitors from the
future. I think a visitor from the future for us is cosmilogically improbable,
but for the time traveller, travelling into the past may be routine. He just
keeps traveling around, and as far as he's concerned, the timeline keeps
changing. But the people he visits see him only once. I think their may be many
different timelines containing all different possibilities including visitors
from a future.

everyone firm proof that time travel is possible.

And you know this, because?


Logic, if you go back into the past and alter history, its not really the past
anymore, its not the time traveller's past as he remembers something different,
for him its the new present. All his doing is unwinding past events and making
them happen differently when he moves forwar in time once more, he is never in
the past, he is just in a parallel timeline that shares a common history with
his own up until the point in which he arrived, he's not in his own past, so
its not really time travel by definition.

Tom

"TKalbfus" wrote in message
...
Er, they are the same thing. Depending from where you are looking.

No.

Yes you can witness someone going back in time so long as they are
traveling
away from you faster than the speed of light. For Example:

We see the light of Alpha Centauri now, as it appeared 4.4 years ago. We
see
the light reflected off out own Earth as it appears just about now. Now if
a
spaceship were to travel from Earth to Alpha Centauri so fast that we
could
follow it with an arbitrarily powerful telescope and see it pass Alpha
Centauri
in the next minute, we are actually witnessing something traveling back in
time.

Your example involves both faster than light travel and time travel. It is
possible to conceive of faster than light travel without time travel. You
have someone leaving Earth and arriving on Alpha Centauri 4.4 years ago.
Suppose instead that he arrived one minute later. We wouldn't see him
arrive until 4.4 years later.

The ship is not traveling into our own past, but into Alpha centauri's
past.

People on Alpha Centauri could synchronize their clocks with our clocks.
Suppose we agree to synchronize on a Lunar eclipse. They won't see the
eclipse until 4.4 years later, but they know that, so they add 4.4 years.
Time travel for them would be time travel for us. If two objects are
traveling very fast relative to each other, they would have trouble
synchronizing their clocks.

Since we can't see Alpha Centauri's present, that star's past cannot
affect our own past so long as that past is less than 4.4 years ago. If
that
starship where to turn around and head back toward us at that same speed,
it
would disappear and we'd never see it again. Perhaps in another timeline
that
ship would appear out of nowhere with no explaination as to its origin,
but
we'd never see that ship again.

I don't see why he couldn't make the return trip. Suppose the people on Alp
ha Centauri also had a big telescope and fast ship. They should be able to
do anything we can do.

If a ship leaves Earth at 9:00, arrives at Alpha Centauri at 9:01, and
returns to Earth at 9:02, that's not time travel, but it is faster than
light travel. The G forces would be pretty severe. Neither portion of the
trip is time travel and the round trip isn't time travel.

I'm inclined to think that time travel is impossible, but we will probably
achieve faster than light communication.

I'm inclined to think that time travel is impossible, but we will probably
achieve faster than light communication.

Yep, I'd agree with you, almost. Time travel is possible, but warp flight
doesn't create it. Our observation of an object does not control it's time
of occurance.

David

Your example involves both faster than light travel and time travel. It is
possible to conceive of faster than light travel without time travel. You
have someone leaving Earth and arriving on Alpha Centauri 4.4 years ago.
Suppose instead that he arrived one minute later. We wouldn't see him
arrive until 4.4 years later.


Yes there are three classes of velocities when you are traveling faster than
the speed of light, Superluminal, infinite, and Ultraluminal.

A superluminal spaceship moving away from us, and toward Alpha Centauri would
appear to be moving away from us at between half the speed of light and the
speed of light. We'll see its image recede from us at that velocity because you
have to allow time for the photons reflected off of it to reach our eyes and
light travels at the speed of light.

A infinite velocity spaceship would appear to us to be travelling away from us
at exactly the speed of light. In one instant in time, that spaceship would
cover all points between Earth and Alpha Centuri and in that instant, any
photons in its path would reflect off of it, but those photons are at varying
distances from Earth, the photons that are further away would take longer to
reach us than those closer to us, so this would produce an image of a spaceship
moving away from us at the speed of light.

A spaceship moving away at an Ultraluminal velocity relative to us would appear
to be moving backward in time. It will start in the present here on Earth and
be seen to quickly approach an object in less time than we know it takes light
from than object to reach us. The onlyway for the object to do that is to go so
fast that the magnitude of its velocity is negative, its still heading away
from us, but negative time units elapse with every increment of forward motion.

For the infinite velocity, no time units elapse with every degree of forward
motion.

For merely superluminal travel positive time units elapse with forward motion.
Once past the speed of light, there is no barrier preventing a spaceship from
accelerating from superluminal to infinite to ultraluminal velocities, none of
those velocities appear infinite when they are receding from us.

People on Alpha Centauri could synchronize their clocks with our clocks.
Suppose we agree to synchronize on a Lunar eclipse. They won't see the
eclipse until 4.4 years later, but they know that, so they add 4.4 years.
Time travel for them would be time travel for us.

People living on a planet orbiting Alpha Centauri would know they are seeing
Earth's past, they could calculate where Earth would be in their now, they
would also know the moment a Lunar eclipse would occur, this is essentially the
same as predicting a future lunar eclipse from the surface of Earth. For the
purposes of effecting events on Alpha Centauri, a beam of light starting on
Earth and reaching Alpha Centauri may as well have arrived in an instant.
People on alpha Centauri have no way of knowing what's happened on Earth until
the beam of light has reached their eyes. They can calculate where the Moon is
"now" but they have no way of telling for sure until that beam of light reaches
their eyes and confirms their prediction. Events on Earth in Alpha Centauri's
present may as well be 4.4 years in the future, because that's how long they'll
have to wait in order to see them.

Time travel into the past where the distance in space is greater than the
distance into the past does not cause time paradoxes, there is no way it can,
because the light from the space ship will always reach our eyes after it has
been sent and will appear to the senders to be in proper chronological order.

The possiblity of changing history only occurs when you travel further in the
past than you do in space. Of course you could never witness this happening
because you will be changed with history and the past will appear perfectly
consistent and unchanged. You won't be the same you of course, you'll be one
who had lived in a different timeline. This timeline will include a supposed
time traveller who appeared out of nowhere and you would not have sent him.

The you that sent the time traveller will never see him again, he disappears
the moment he travels further in the past than he does in space.


I don't see why he couldn't make the return trip. Suppose the people on Alp
ha Centauri also had a big telescope and fast ship. They should be able to
do anything we can do.


There are two timelines of Alpha Centauri beginning where the send the
ultraluminal spaceship back to us. We would only see the one where the
spaceship disappears from Alpha Centaui's telescopes as well as our own,
because that would be the only thing we could see that would be consistent with
our won past. We'd never see the other Alpha Centauri that witness a spaceship
traveling into our own past and that Alpha Centauri will never see us, because
by the time 4.4 years elapse they won't be seeing our present, but another
present with another version of us caused by the time traveller meddling in our
history and that time traveler's mere presence will alter the past, even if he
doesn't try to. The information of his existence will escape his body and
effect our molecules in a random way changing historical events and weather
patterns.


I'm inclined to think that time travel is impossible, but we will probably
achieve faster than light communication.


The way I define time travel, it is impossible, but travelling further into
space than in the past is not really time travel and is perfectly permissible
without effecting the order of events as we see them.

Tom

Joann Evans wrote in message ...
Explorer8939 wrote:

Whoa, you guys are letting partisanship blind you on this one.

Gen Clark clearly indicated that he knew that FTL violated the laws of
physics as we know them today, all he was saying he that he has faith
that some day we will find a way to exceed light speed. He did not say
we would do this tomorrow, or how we would do it.

Actually, I thed to agree with that.

But if I were running for President, Id've kept my mouth completely
shut on the matter, at least where I might be quoted. Isn't Clark smart
enough to know that some things aren't going to politically fly well,
however much one might believe them? Espically issues that are
irrelevant, and will be until such time as there are sound reasons to
think he may be right?

Give the guy a break, if Bush had said it, you guys would be falling
over one other to talk about what a visionary the guy is.

For the record, I'm a registered Democrat.

Wait, I am assuming you are all scientifcally mind peopl who have an
interest in space and science. You finally get a presidential canidate
who says his only "faith" is in science, and knows enough to about the
topic to quote einsteins theory of relativity and understand that it
forbids traveling faster than the speed of light and you are calling
hima quake or irresponsible because he says that he flipantly says his
one faith based initive would be to look into FTL travel because he
believes man can do it...Lets break his statments down into positive
and negative here.

Positive:
-Like's science, will most likely support it as president
-Shows an understanding of science...enough to know that FTL is a
debatable issue
-His understanding of science will lead him to make educated policy
decisions about social debates that are tangentially attached to
science
-The only faith he holds stronger than then his faith in the march of
scientific discovery and what it has proved so far is his faith in the
ingenuity of man to move beyound what we today believe is possible.

Negatives:
-Jackass will manipulate his statement to make him sound like a quake.

I think any informed scientifically minded human being will see this
is a tremendously positive statement and rejoice.

In article ,
Mike Rhino wrote:
If a ship leaves Earth at 9:00, arrives at Alpha Centauri at 9:01, and
returns to Earth at 9:02, that's not time travel, but it is faster than
light travel.

In a relativistic universe, there's no distinction between the two. As
Geoff Landis said in the Interstellar Propulsion panel at Torcon: "It's a
feature of the universe that faster-than-light travel and time travel are
the *same* *thing*."

Any trip using a faster-than-light drive will look to some observers as if
it arrived before it departed.

Note that we are not talking here about people standing by the side of the
road. Said observers may have to be passing by at a large fraction of the
speed of light, but their viewpoint is still just as valid as yours. (You
and they will disagree about measurements of both distance and time, but
neither set of measurements is "right" and the other "wrong"; both are
equally valid.) In turn, something that looks to *them* like a trip with
an FTL drive will look to *you* like time travel.

The parts of relativity on which this rests are, alas, experimentally
confirmed in a number of ways to quite high accuracy. Any escape clause
that permits getting around them is going to be very subtle indeed.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

TKalbfus wrote:
Wormhole physics, which may or may not be real and may or
may not be exploitable by human-available engineering,
may or may not allow useful FTL.

FTL is either impossible or possible. I think saying its too difficult to
engineer for all time is a cop out. If you say something is possible yet too
difficult, your ruling out bu fiat all possible solutions to this problem
without even looking at them. I think FTL may be possible, but time travel is a
logical contradiction. You may be able to reverse the time arrow with respect
to another point of view, but you can't go into your own past and change it.

What do you mean by altering the past anyway? How is it possible for anyone in
the present to notice a change in the past? I don't think such a thing is
possible. Reality isn't going to ripple and change in the present giving
everyone firm proof that time travel is possible. The most that may be
achievable is to cause the prospective time traveller to disappear. He may be
able to zip over to Alpha Centauri in two seconds, but the light would still
take 4.4 years and 2 seconds to reach us. This should allow travel 4.4 years in
the past so long as the time traveler also traveles 4.4 light years out as
well. The light from his arrival there will not get back here in time to affect
our own past, so this sort of time travel is permissable, but if he makes the
same trip back here, he will disappear from our universe as far as were
concerned, he could not arrive in our own past 8.8 years back in time because
he never did. This doesn't mean he's not in an alternate time line that
resembles our own past, but we'll never be able to prove it. So as far as were
concerned time travel into our own past is impossible because it didn't happen.

But this is making a rather special connection between ligh cones and time,
which need not really be the case. Unlike space, time clearly has a prefered
direction.


Tom

--
Sander

+++ Out of cheese error +++

TKalbfus wrote:
Er, they are the same thing. Depending from where you are looking.


Yes you can witness someone going back in time so long as they are traveling
away from you faster than the speed of light. For Example:

We see the light of Alpha Centauri now, as it appeared 4.4 years ago. We see
the light reflected off out own Earth as it appears just about now. Now if a
spaceship were to travel from Earth to Alpha Centauri so fast that we could
follow it with an arbitrarily powerful telescope and see it pass Alpha Centauri
in the next minute, we are actually witnessing something traveling back in
time. The ship is not traveling into our own past, but into Alpha centauri's
past. Since we can't see Alpha Centauri's present, that star's past cannot
affect our own past so long as that past is less than 4.4 years ago. If that
starship where to turn around and head back toward us at that same speed, it
would disappear and we'd never see it again. Perhaps in another timeline that
ship would appear out of nowhere with no explaination as to its origin, but
we'd never see that ship again. There's no way to prove that anything could
travel into our own past, since any attempt to do so would change the present
and we'd would not be here to witness it.

But this is just because you are involving only *one* observer, and having
there be consistency from his point of view. There is no real reason why
consistency in the universe would exist only as far as only slower than light
view is concerned.

* viewer on earth - the ship takes off and leaves a thin, stretched-out
view, and watching the progress to Alpha-Centauri takes 4.4 years
(the light generated by the ship when at AC takes that long to get back).
If the ship came back, he will be seeing two images, spaced by 4 seconds.

* viewer on Alpha-Centauri - the ship pops into existence, and its *past*
stretched-out image will start arrivig, culminating in the take-off
being visible in 4.4 years. if the ship returns to earth, they see the
same thing as the earth observer.

* viewer in the ship - sees the past 4.4 years of alpha centauri rush
forwards at a fast rate and sees the past 4.4 years of earth in reverse
order. coming back, alpha centauri and earth switch places


Tom

--
Sander

+++ Out of cheese error +++

In Mike Rhino wrote:

The big bang theory also violates the known laws of physics,

No it doesn't.

You may be thinking about inflationary expansion?

--
Geoffrey A. Landis
http://www.sff.net/people/geoffrey.landis

"Brett Buck" wrote in message
...

I do despise the Clintons and everything they stand for, like any
right-thinking person.

Bill Clinton had the somewhat unusual policy of being socially liberal
and fiscally conservative. If you despise everything Clinton stands for,
you must therefore be socially conservative and fiscally liberal. I
have to say, that's a very odd combination.

--
Geoffrey A. Landis
http://www.sff.net/people/geoffrey.landis