Interstellar travel
Ryan Mitchell Calbick
several allusions to the possibilities raised by special relativity,
particularly as Hawking proposes. As I understand it (and, I admit, it is
altogether likely I am mistaken), Special relativity allows for a mass to
defy the limits imposed by Einstein's equation. Instead of reaching the
99% barrier (where mass becomes an insurmountable barrier against thrust
potential), it seems possible to circumvent the problem. There might be
two ways: space-time compression or artificial 'worm holes.' Why not just
bring the two points in space and time together? It seems science fiction
has both of these covered.
The first method involves compressing the 'fabric' of space-time
behind an object (a spacecraft) like a wave for a surfer, or an elastic
band. This method was neatly described by writer and physicist, Lawrence
M. Krauss in his book (aptly entitled "The Physics of Star Trek" [1]).
The second method involves an actual break in the 'fabric' where
two distant points are brought together. This has been artfully
demonstrated in some very bad sci fi films and otherwise clearly described
in Hawking's "Brief History...," I believe.
I am stumped as to why these methods aren't discussed more often.
Is it a question of fuel type This might be an avenue for the application
of fusion energy (is it really that far from realization still?). It seems
that the question of trip duration and time dilation are covered by both
of these methods.
Any ideas?
[1] Lawrence M. Krauss, The physics of Star Trek.(New York, NY: Harper
Perennial, 1995)
Dan
Ryan Mitchell Calbick wrote:
> I am stumped as to why these methods aren't discussed more often.
> Is it a question of fuel type This might be an avenue for the application
> of fusion energy (is it really that far from realization still?). It seems
> that the question of trip duration and time dilation are covered by both
> of these methods.
Nasa has a scientist working on a fusion-based rocket. He has spent
over 40 years designing it, and the prototypes are just being built and
tested. They use magnetic fields to keep the super-heated plasma away from
the walls of the rocket. I saw a web site about it once, but any other news I
have
no idea.
Last but not least, he said this new rocket could carry a manned mission
to Mars in less than 100 days. Considering it takes most missions over 300
days to get to Mars, I think a 66% reduction is pretty good :)
So, to your question of feasable fusion energy, it is getting there ;)
The trouble is harnessing it without having it melt every container you put
it in ;)
Dan
Sean Ellis
>[... on warps and wormholes...]
>
> I am stumped as to why these methods aren't discussed more often.
>Is it a question of fuel type This might be an avenue for the application
>of fusion energy (is it really that far from realization still?). It seems
>that the question of trip duration and time dilation are covered by both
>of these methods.
>
> Any ideas?
It's not a question of fuel type; mere energy won't get you these
effects. Both rely on the weird concept of "negative energy density",
which is difficult to achieve, especially in the sort of quantities
required to stretch the space behind the ship (warp) or to thread
through a wormhole to keep it from collapsing (wormhole).
Add to that the fact that *any* method of FTL travel opens up the
possibility of time travel (which in turn implies causal loops,
paradoxes and closed space-time trajectories - all Very Bad Things),
and even warps and wormholes may be disallowed for reasons we don't
yet understand.
For the time being, at least, it looks like we'll have to go the long
way round.
Sean
|||||||| 012345678 Proportiometer(TM)
######## ^ [Non spammers: Delete "un-" after @ in reply-to field]
J. Scott Miller
>
> I have a question about interstellar travel. Over the years I've heard
> several allusions to the possibilities raised by special relativity,
> particularly as Hawking proposes. As I understand it (and, I admit, it is
> altogether likely I am mistaken), Special relativity allows for a mass to
> defy the limits imposed by Einstein's equation.
Nope. The limit on travel is specified by special relativity, for it is
special relativity that tells us that it would take more energy than
exists in the universe (let alone that we can manage) that will prevent
objects with even the smallest mass from approaching light speed.
> Instead of reaching the 99% barrier (where mass becomes an
> insurmountable barrier against thrust potential), it seems possible to
> circumvent the problem. There might be two ways: space-time
> compression or artificial 'worm holes.' Why not just bring the two
> points in space and time together? It seems science fiction
> has both of these covered.
Science fiction, good science fiction, is good because it allows us to
suspend the laws of physics. The fewer of those ideas that are
suspended, the more plausible the story. In the case of space travel,
they leave out the energy process, not specifying how much would have to
be generated to make things happen, but implying that it is small enough
that we could manage it. Else, everything would be carried out close to
home. Energy is the key, and as I stated above, we don't know how to
control all of the energy in the universe.
>
> The first method involves compressing the 'fabric' of space-time
> behind an object (a spacecraft) like a wave for a surfer, or an elastic
> band. This method was neatly described by writer and physicist,
> Lawrence M. Krauss in his book (aptly entitled "The Physics of Star
> Trek" [1]).
Which actually says how it might be done without indicating the energy
necessary to do it.
>
> The second method involves an actual break in the 'fabric' where
> two distant points are brought together. This has been artfully
> demonstrated in some very bad sci fi films and otherwise clearly
> described in Hawking's "Brief History...," I believe.
I assume here you allude to wormhole creation. Most theoretical
calculations published to date indicate that the introduction of the
slightest amount of matter near the mouth of a wormhole would snap it
shut because of their inherent instability and the gravity of that
insignificant bit of matter. Another point conveniently left out of
science fiction programs.
>
> I am stumped as to why these methods aren't discussed more often.
They have been often discussed in this group and sci.astro, perhaps
others that I don't frequent.
> Is it a question of fuel type This might be an avenue for the
> application of fusion energy (is it really that far from realization
> still?). It seems that the question of trip duration and time dilation
> are covered by both of these methods.
>
> Any ideas?
As indicated, energy is the problem, generating and controlling lots of
it. Nuclear energy is not the key, though it may get us a bit faster
than chemical energy. Suffice it to say, for now anyway, interstellar
travel will be multigenerational, if it happens at all.
--
J. Scott Miller, Program Coordinator jsmi...@athena.louisville.edu
Rauch Memorial Planetarium http://www.louisville.edu/planetarium
University of Louisville
PETEKWANDO
>several allusions to the possibilities raised by special relativity,
>particularly as Hawking proposes.
>There might be
>two ways: space-time compression or artificial 'worm holes.'
> I am stumped as to why these methods aren't discussed more often.
>Is it a question of fuel type This might be an avenue for the application
>of fusion energy (is it really that far from realization still?).
If only it were that simple. Unfortunately, the power requirements needed
to warp spacetime in these ways would require a LOT more than fusion reactors
could provide. I direct you to Krauss' second book on the subject, _Beyond
StarTrek_. It contains some rather depressing findings on spacetime distortion
schemes.
Still, keep hope alive. Somewhere out there, there is a better way to get
from here to there. Just a gut feeling (and yes, I know that gut feelings are
not exactly scientific).
Peter E. Vogel, Jr.
"(A cynic is) a man who knows the price of everything and the value of
nothing."
- Oscar Wilde
Paul Johnson
>rcal...@sfu.ca (Ryan Mitchell Calbick) wrote:
>>[... on warps and wormholes...]
>>
>Add to that the fact that *any* method of FTL travel opens up the
>possibility of time travel (which in turn implies causal loops,
>paradoxes and closed space-time trajectories - all Very Bad Things),
>and even warps and wormholes may be disallowed for reasons we don't
>yet understand.
Not necessarily. You have to appreciate that ANY faster than light
phenomonon invalidates relativity theory because it is based on the
assumption that NOTHING travels faster than light. Otherwise there
would not be the problem of synchronising remote clocks with signals
restricted to the speed of light.
So all you have to do is locate an FTL mechanism and we are into a new
paradigm.
_________________________________________
Paul Johnson : pal...@acslink.net.au
Perth, WA : +61 08 9405 2416
=========================================
Paul Johnson
>As indicated, energy is the problem, generating and controlling lots of
>it. Nuclear energy is not the key, though it may get us a bit faster
>than chemical energy. Suffice it to say, for now anyway, interstellar
>travel will be multigenerational, if it happens at all.
>--
>J. Scott Miller, Program Coordinator jsmi...@athena.louisville.edu
>Rauch Memorial Planetarium http://www.louisville.edu/planetarium
>University of Louisville
As I see it the problem really relates to applying an external force
to an object. Like pushing a car, if it is stationary you can apply a
large force, but as it starts moving you can't keep up with it and
cannot apply the same force.
Similarly with forces used in particle accelerators - you are trying
to apply an external electromagnetic force that propagates at the
speed of light. As the particle nears the speed of light the force
applied diminishes.
If you could carry sufficient energy with the object you are trying to
accelerate MAYBE you could continue to apply sufficient force.
However, a considerable amount of energy is still required.
I am of the opinion that space is an attribute of mass. A fast moving
mass cannot interact to the same degree as a stationary mass with the
space or other properties (gravity, electromagnetism that propagate at
the speed of light) associated with masses in relative motion to it.
Ryan Mitchell Calbick
: As I see it the problem really relates to applying an external force
: to an object. Like pushing a car, if it is stationary you can apply a
: large force, but as it starts moving you can't keep up with it and
: cannot apply the same force.
[snipped details]
: I am of the opinion that space is an attribute of mass. A fast moving
: mass cannot interact to the same degree as a stationary mass with the
: space or other properties (gravity, electromagnetism that propagate at
: the speed of light) associated with masses in relative motion to it.
This is exactly the type of 'propulsion' system I to which I
referred (see original posting). The idea of overcoming the limitations
imposed by special relativity is to 'cheat' by manipulating spacetime
around you. Sort of like imagining the road beneath your car is
accelerating but the car remains 'stationary.' The way I imagine it, this
eliminates two problems, inertia (that deadly acceleration/deceleration
curve) and the mass/energy stalemate at the upper limit of acceleration.
Ryan
Jim Morrison
Paul Johnson wrote in message <70bioj$ehm$1...@news1.mpx.com.au>...
>sel...@geocities.com (Sean Ellis) wrote:
>
>>rcal...@sfu.ca (Ryan Mitchell Calbick) wrote:
>
>>>[... on warps and wormholes...]
>>>
>
>>Add to that the fact that *any* method of FTL travel opens up the
>>possibility of time travel (which in turn implies causal loops,
>>paradoxes and closed space-time trajectories - all Very Bad Things),
>>and even warps and wormholes may be disallowed for reasons we don't
>>yet understand.
>
>
>Not necessarily. You have to appreciate that ANY faster than light
>phenomonon invalidates relativity theory because it is based on the
>assumption that NOTHING travels faster than light. Otherwise there
>would not be the problem of synchronising remote clocks with signals
>restricted to the speed of light.
>
>So all you have to do is locate an FTL mechanism and we are into a new
>paradigm.
It seems to me that the secret to interstellar
travel lies in discovering FTL communications mechanisms.
If you can maintain a real time data link that is FTL, you can
explore the universe at large, or perhaps just your own solar system.
An FTL data link would be useful for exploring our own solar
system for at least three centuries. Save the interstellar stuff
for a few thousand years, when it might make a difference in our lives.
Frank Crary
Paul Johnson <pal...@acslink.net.au> wrote:
>>Add to that the fact that *any* method of FTL travel opens up the
>>possibility of time travel (which in turn implies causal loops,
>Not necessarily. You have to appreciate that ANY faster than light
>phenomonon invalidates relativity theory because it is based on the
>assumption that NOTHING travels faster than light.
Special relativity makes no such assumption. It simply assumes
that light travels at the same speed in all (inertial) reference
frames. Everything else follows from that. When people say that
special relativity does not allow faster than light travel, they
are stating a conclusion/interpretation/opinion, not a basic
fact or assumption of special relativity. For example, special
relativity says that faster than light travel would, in someone's
reference frame, be the same as traveling backwards in time.
Most people, looking at that, conclude that faster than light
travel is, therefore, impossible. But, really, all special
relativity says is that either faster than light travel is
impossible _or_ causality (i.e. the idea that a cause of an
even must occur before the event) is simply a myth, and only
true to our (possibly limited) experience. Given the choice,
most people prefer to believe in causality and say that relativity
proves that faster than light travel is impossible.
Frank Crary
CU Boulder
Bruce Sterling Woodcock
fcr...@rintintin.Colorado.EDU (Frank Crary) wrote:
>But, really, all special
>relativity says is that either faster than light travel is
>impossible _or_ causality (i.e. the idea that a cause of an
>even must occur before the event) is simply a myth, and only
>true to our (possibly limited) experience.
Or that causality is *not* measured by speed of light, but rather
by some FTL mechanism. I think this is something often overlooked;
if you assume that a "causation" can only travel as fast as light,
then of course any FTL travel in the paradigm will appear to violate
causality. One could argue (and argue, and argue) that certain
aspects of QM demonstrate that causality travels faster than light.
Bruce
Hans Zekl
>
> In article <70bioj$ehm$1...@news1.mpx.com.au>,
> Paul Johnson <pal...@acslink.net.au> wrote:
> ...
> >Not necessarily. You have to appreciate that ANY faster than light
> >phenomonon invalidates relativity theory because it is based on the
> >assumption that NOTHING travels faster than light.
>
> Special relativity makes no such assumption. It simply assumes
> that light travels at the same speed in all (inertial) reference
> frames. Everything else follows from that. When people say that
> special relativity does not allow faster than light travel, they
> are stating a conclusion/interpretation/opinion, not a basic
> fact or assumption of special relativity. ...
Sorry,
that's not correct. Special relativity says, that the mass of a moving
object increases when it gets faster. At the speed of light it will be
infinetly large. So one needs more and more energy to accelerate the
object. Near the speed of light one needs incredibel amounts of energy.
In this sense the speed of light is the maximum velocity, one will never
reach.
As far as we we do not find another way for interstellar travel, it will
be very expensive to reach high velocities.
Greetings
Hans Zekl
Craig Berry
: It seems to me that the secret to interstellar
: travel lies in discovering FTL communications mechanisms.
: If you can maintain a real time data link that is FTL, you can
: explore the universe at large, or perhaps just your own solar system.
: An FTL data link would be useful for exploring our own solar
: system for at least three centuries. Save the interstellar stuff
: for a few thousand years, when it might make a difference in our lives.
But even this involves time paradoxes. What looks like 'simple' FTL
communication in your frame of reference (say, sending a signal from
Jupiter to Earth in 1 second) *will* become communication backward in time
in other frames -- that is, in a frame moving relative to the 'rest' frame
of communication, the signal will be received before it's sent. It's
difficult (for me) to imagine a universe in which such causality
violations can occur.
---------------------------------------------------------------------
| Craig Berry - cbe...@cinenet.net
--*-- Home Page: http://www.cinenet.net/users/cberry/home.html
| "Ripple in still water, when there is no pebble tossed,
nor wind to blow..."
Graham Nelson
<URL:mailto:l...@aa.net> wrote:
> It seems to me that the secret to interstellar
> travel lies in discovering FTL communications mechanisms.
I think you might as well say that the secret to world happiness
lies in discovering a ring of three wishes. There is no reason
to suppose that FTL anything is possible, and a very good deal
of evidence to suggest that it is not.
--
Graham Nelson | gra...@gnelson.demon.co.uk | Oxford, United Kingdom
Paul Morris
<ze...@rhein-neckar.netsurf.de> wrote:
> Frank Crary wrote:
> >
> > In article <70bioj$ehm$1...@news1.mpx.com.au>,
> > Paul Johnson <pal...@acslink.net.au> wrote:
>
> > ...
> > >Not necessarily. You have to appreciate that ANY faster than light
> > >phenomonon invalidates relativity theory because it is based on the
> > >assumption that NOTHING travels faster than light.
> >
> > Special relativity makes no such assumption. It simply assumes
> > that light travels at the same speed in all (inertial) reference
> > frames. Everything else follows from that. When people say that
> > special relativity does not allow faster than light travel, they
> > are stating a conclusion/interpretation/opinion, not a basic
> > fact or assumption of special relativity. ...
>
> Sorry,
> that's not correct. Special relativity says, that the mass of a moving
> object increases when it gets faster. At the speed of light it will be
> infinetly large. So one needs more and more energy to accelerate the
> object. Near the speed of light one needs incredibel amounts of energy.
> In this sense the speed of light is the maximum velocity, one will never
> reach.
>
Special Relativity implies that it requires an infinite amount of energy to
accelerate an object of nonzero rest mass to the speed of light. But, for
all we know, a source of infinite energy might exist in the Universe. For
example, if there is currently something travelling at transluminal velocity,
then a collision with an ordinary object might in principle cause a transfer
resulting in a transluminal velocity for the latter.
Paul
--
Email: lastname at best dot com. (no spam please)
Frank Crary
Bruce Sterling Woodcock <sirb...@ix.netcom.com> wrote:
>>But, really, all special
>>relativity says is that either faster than light travel is
>>impossible _or_ causality (i.e. the idea that a cause of an
>>even must occur before the event) is simply a myth, and only
>>true to our (possibly limited) experience.
>Or that causality is *not* measured by speed of light, but rather
>by some FTL mechanism. I think this is something often overlooked;
>if you assume that a "causation" can only travel as fast as light...
I don't really think of ``causation'' as traveling, so I'm not
sure what you mean. Causality simply means that the cause of
an event occurs before the event. Now, from _someone's_ point
of view, FTL travel isn't a problem: They see the cause occurring
before the event. But from someone else's point of view, FTL
travel means the event occurred before its cause. The basis of
relativity is that _all_ (inertial) frames of reference are
equally valid. So if FTL travel violates causality from in
_anyone's_ frame of reference, there is a problem. Either with
causality or the idea of FTL travel, take your pick.
Frank Crary
CU Boulder
Bruce Sterling Woodcock
fcr...@rintintin.Colorado.EDU (Frank Crary) wrote:
The last time I did the actual calculations (mind you, this was
college, so I couldn't do them now), this is incorrect. I know,
it's a common misconception that's the case, but it's not... it
only appears to violate causality because you assume the propgation
of things at the speed of light, like the light cone. I know you
don't think of "causation" as traveling, but this is a rhetorical
device - in as much as you can determine simultaneaity (or lack
thereof) you're talking about speed of light. You can do FTL
travel so that from *someone's* point of view, causation isn't
lost... you just have to be careful you don't sneak another
assumption back in when you reach a conclusion.
I'm not going to sit through a thread on this, go through many
relativity examples, and have a big flamewar. I don't have the
time. If you don't want to believe me, fine, but I stick by my
statement - you don't have to lose causality with FTL travel, in
any frame of reference.
Bruce
Trakar
In article <70mac0$i...@sjx-ixn8.ix.netcom.com>, Bruce Sterling Woodcock
<sirb...@ix.netcom.com> writes:
> (mind you, this was
>college, so I couldn't do them now),
Please, don't tell me how long it has been, I'll probably start feeling
older than I should. Even though I know that time is relative, contemporaries
begin to sound like "fundemental" speakers after a while!
Trakar
>I don't really think of ``causation'' as traveling, so I'm not
>sure what you mean. Causality simply means that the cause of
>an event occurs before the event. Now, from _someone's_ point
>of view, FTL travel isn't a problem: They see the cause occurring
>before the event. But from someone else's point of view, FTL
>travel means the event occurred before its cause. The basis of
>relativity is that _all_ (inertial) frames of reference are
>equally valid. So if FTL travel violates causality from in
>_anyone's_ frame of reference, there is a problem. Either with
>causality or the idea of FTL travel, take your pick.
>
"Causality", seems to be a primary function of time-flow in our
space/time existance. This is not to say that it is a prerequisite
for all potentials, but it seems to be a fundemental in our universe.
Trakar
In article <70ldut$q...@dfw-ixnews7.ix.netcom.com>, Bruce Sterling Woodcock
<sirb...@ix.netcom.com> writes:
> One could argue (and argue, and argue) that certain
>aspects of QM demonstrate that causality travels faster than light.
>
Such as?
Trakar
In article <70gl4k$e...@lace.colorado.edu>, fcr...@rintintin.Colorado.EDU (Frank
Crary) writes:
>Special relativity makes no such assumption. It simply assumes
>that light travels at the same speed in all (inertial) reference
>frames. Everything else follows from that. When people say that
>special relativity does not allow faster than light travel, they
>are stating a conclusion/interpretation/opinion, not a basic
>fact or assumption of special relativity. For example, special
>relativity says that faster than light travel would, in someone's
>reference frame, be the same as traveling backwards in time.
>Most people, looking at that, conclude that faster than light
>travel is, therefore, impossible. But, really, all special
>relativity says is that either faster than light travel is
>impossible _or_ causality (i.e. the idea that a cause of an
>even must occur before the event) is simply a myth, and only
>true to our (possibly limited) experience. Given the choice,
>most people prefer to believe in causality and say that relativity
>proves that faster than light travel is impossible.
Myth is a bit strong in my opinion, it is a "myth" if you don't comprehend the
the math behind the solution to the problem. Facts, tend to negate the
possibility
in many ways that are totally independant of the assumptions, or intuitive
building
blocks.
John Beaderstadt
>
> that's not correct. Special relativity says, that the mass of a moving
> object increases when it gets faster. At the speed of light it will be
> infinetly large.
That's about the point my brain shuts down. If the speed of light is
finite, how can it result in, or be partly composed of, an infinite?
Isn't "infinite" mathematically like "zero", conceptually useful but not
very practical?
--
If a man talks in the forest, and no woman hears him, is he still wrong?
bla...@my-dejanews.com
>
> >But, really, all special
> >relativity says is that either faster than light travel is
> >impossible _or_ causality (i.e. the idea that a cause of an
> >even must occur before the event) is simply a myth, and only
> >true to our (possibly limited) experience.
>
> by some FTL mechanism. I think this is something often overlooked;
> then of course any FTL travel in the paradigm will appear to violate
> aspects of QM demonstrate that causality travels faster than light.
The interesting thing is, causality allows for teleportation, such that an
object can disappear and reappear anywhere else instantaniously, now that can
be done is the 64 dollar question.
Greg
-----------== Posted via Deja News, The Discussion Network ==----------
http://www.dejanews.com/ Search, Read, Discuss, or Start Your Own
Bill Bonde
>
> In article <362F06...@together.net>,
> John Beaderstadt <be...@together.net> wrote:
> >> that's not correct. Special relativity says, that the mass of a moving
> >> object increases when it gets faster. At the speed of light it will be
> >> infinetly large.
>
> >That's about the point my brain shuts down. If the speed of light is
> >finite, how can it result in, or be partly composed of, an infinite?
>
> m = m_0/sqrt(1-v^2/c^2)
> where m_0 is its mass when at rest, v is its velocity and
> c is the speed of light. (I think... the square root may or
> may not be correct, but I don't feel like looking it up.)
> If v=c, then you are dividing by zero, and you get an infinite mass.
>
>
OK, but let's say that you could get a particle to move at close to the
speed of light in a vacuum. Then move it into a substance where the
speed of light is lower while the speed of the particle stays the same.
Presto, particle going faster than light. I don't know what the
substance of choice would be or the particle. An electron would be a
good practical choice but wouldn't it be affected greatly by the
substance in question? A neutrino would be great if we could control
them.
Frank Crary
>> that light travels at the same speed in all (inertial) reference
>> frames. Everything else follows from that. When people say that
>> special relativity does not allow faster than light travel, they
>> are stating a conclusion/interpretation/opinion, not a basic
>Sorry,
>that's not correct. Special relativity says, that the mass of a moving
>object increases when it gets faster. At the speed of light it will be
>infinetly large.
Apparently general relativity makes some exceptions to that. (In
effect: It allows the possibility of apparently faster than light
travel without encountering this problem. I have no idea about
the details, since I never got past the math involved in general
relativity...) In any case, special relativity does not rule out
the existence of particles that _always_ travel faster than the
speed of light. Special relativity and causality together, do
rule this out.
Frank Crary
CU Boulder
Frank Crary
>> object increases when it gets faster. At the speed of light it will be
>> infinetly large.
>That's about the point my brain shuts down. If the speed of light is
>finite, how can it result in, or be partly composed of, an infinite?
The mass of an object, according to special relativity is
m = m_0/sqrt(1-v^2/c^2)
where m_0 is its mass when at rest, v is its velocity and
c is the speed of light. (I think... the square root may or
may not be correct, but I don't feel like looking it up.)
If v=c, then you are dividing by zero, and you get an infinite mass.
Frank Crary
CU Boulder
Ed
back in my distant memory is that it was all about reference points of
both time and position.
If an object is travelling at 99% the speed of light compared to us
then from the people in that objects perspective they may be standing
still (engines off) and we are on one weird galaxy going past.
For them to accelerate they simply tur the engines on - as all their
propellant is travelling at 0 km per hour compared to them it still
imparts the same amount of propulsive force so it is not here that
infinite power systems are needed.
The problem as I remember comes down to time slowing down - the object
would appear to us to have near infinite mass but also it would be in
a different time speed - infinitely close to stopped, and therefore
since acceleration is linked to time - not accelerating. People on the
craft would be in the same time speed as the craft and not notice this
obviously, and to continue to state the iobvious so would all the
propellant onthe craft.
now I am even more confused and a headache is coming on :)
On 23 Oct 1998 01:48:02 GMT, fcr...@rintintin.Colorado.EDU (Frank
Crary) wrote:
>In article <362E44D7...@rhein-neckar.netsurf.de>,
>Hans Zekl <ze...@rhein-neckar.netsurf.de> wrote:
>>> Special relativity makes no such assumption. It simply assumes
>>> that light travels at the same speed in all (inertial) reference
>>> frames. Everything else follows from that. When people say that
>>> special relativity does not allow faster than light travel, they
>>> are stating a conclusion/interpretation/opinion, not a basic
>>> fact or assumption of special relativity. ...
>
>>Sorry,
>>that's not correct. Special relativity says, that the mass of a moving
>>object increases when it gets faster. At the speed of light it will be
>>infinetly large.
>
Ed
forces may be faster than light - or has someone shown gravity to have
a speed of disemination?
bla...@my-dejanews.com
Graham Nelson <gra...@gnelson.demon.co.uk> wrote:
> In article <70h041$1e5$1...@slave1.aa.net>, Jim Morrison
> <URL:mailto:l...@aa.net> wrote:
> > It seems to me that the secret to interstellar
> > travel lies in discovering FTL communications mechanisms.
>
> I think you might as well say that the secret to world happiness
> lies in discovering a ring of three wishes. There is no reason
> to suppose that FTL anything is possible, and a very good deal
> of evidence to suggest that it is not.
>
I thought this would be a perfect place to post this (from Physics News
Update);
SUPERLUMINAL TRAVEL REQUIRES NEGATIVE ENERGIES. Einstein’s special theory of
relativity asserts that no physical object can travel faster than the speed
of light. The theory also holds that mass and energy will have different
values depending on your frame of reference. The idea that the mass (energy)
density in any one frame would always be at least equal to or greater than
zero is called the “weak energy condition.” Ken Olum of Tufts
(k...@cosmos5.phy.tufts.edu, 617-628-5000, x2753) follows the reverse tack in
arguing that superluminal travel is possible in certain warped versions of
space/time but that this would entail the existence of negative energy. In
this case the concepts of superluminal motion and of negative energy need to
be explored. An object with negative mass would be less massive than empty
space. We don’t know of any such object, but physicists have detected small
regions of space characterized by a very slightly negative energy density
(the so called Casimir effect; see Updates 122 and 300). If you combine
negative energy with positive energy you get nothing, very different from the
explosion you get when you combine matter and antimatter. As for
superluminal travel---in Olum’s model objects and signals do not actually
travel faster than light. Rather, the curvature of a spacetime incorporating
a negative-energy density is such that one can arrive quickly at distant
places using sub-light speeds. (Physical Review Letters, 26 October 1998.)
Hal Hawkins
Frank Crary wrote in message <70onhl$e...@lace.colorado.edu>...
>>> object increases when it gets faster. At the speed of light it will be
>>> infinetly large.
>
>>finite, how can it result in, or be partly composed of, an infinite?
>
>The mass of an object, according to special relativity is
>m = m_0/sqrt(1-v^2/c^2)
>where m_0 is its mass when at rest, v is its velocity and
>c is the speed of light. (I think... the square root may or
>may not be correct, but I don't feel like looking it up.)
>If v=c, then you are dividing by zero, and you get an infinite mass.
>
Hey! I thought if you are dividing by zero your answer is undefined. That's
what they lernt me in skool.
Paul Johnson
>> > >Not necessarily. You have to appreciate that ANY faster than light
>> > >phenomonon invalidates relativity theory because it is based on the
>> > >assumption that NOTHING travels faster than light.
>> >
>> > Special relativity makes no such assumption. It simply assumes
>> > that light travels at the same speed in all (inertial) reference
>> > frames. Everything else follows from that. When people say that
>> > special relativity does not allow faster than light travel, they
>> > are stating a conclusion/interpretation/opinion, not a basic
>> > fact or assumption of special relativity. ...
>>
The point I was making is that according to the mathematics I have
studied (Kacser - special theory of relativity) the predictions of
special relativity are based on the absolute nature of the speed of
light, and the calculations are based on an observer and a moving
participant who COMMUNICATE with each other using electromagnetic
waves. It is the fixed speed of these waves according to the two
participants that leads to the Lorentz transformation.
If there was another mechanism of communication not bound by the
absolute speed of light the result would be completely different.
Once you accept the two relativity postulates the results are
inevitable.
You simply have to open your mind to an alternative that fits with
empirical evidence. Newtons laws were superseded by Einstein. We may
not have the final solution yet. It is all to easy to accept the
current theory as truth.
Peter Hayes
>In article <70h041$1e5$1...@slave1.aa.net>, Jim Morrison
><URL:mailto:l...@aa.net> wrote:
>> It seems to me that the secret to interstellar
>> travel lies in discovering FTL communications mechanisms.
>
>I think you might as well say that the secret to world happiness
>lies in discovering a ring of three wishes. There is no reason
>to suppose that FTL anything is possible, and a very good deal
>of evidence to suggest that it is not.
>
Within our ken.
Seti, the search for extraterrestial intelligence, doesn't seem to have
come up with anything. Maybe after a hundred years or so of radio
transmission ETs develop FTL "subspace" radio. If we knew how to look,
perhaps the "aether" is swarming with FTL signals.
Cheers,
--
Peter
"The only thing wrong with Microsoft is that they have no taste" - Steve Jobs.
Joachim Draeger
Hi!
>Sorry,
>that's not correct. Special relativity says, that the mass of a moving
>object increases when it gets faster. At the speed of light it will be
>infinetly large. So one needs more and more energy to accelerate the
>object. Near the speed of light one needs incredibel amounts of energy.
Ok so far
>In this sense the speed of light is the maximum velocity, one will never
>reach.
Sorry, that's not correct. You can not accelerate an object with v<c to c,
ok, but this does not mean that c is the maximum velocity. Look at the
theories about tachyonic particles for example, they allow faster than
light travel without violations of SR.
Joachim
Andrew Wood
> >m = m_0/sqrt(1-v^2/c^2)
> >where m_0 is its mass when at rest, v is its velocity and
> >c is the speed of light. (I think... the square root may or
> >may not be correct, but I don't feel like looking it up.)
> >If v=c, then you are dividing by zero, and you get an infinite mass.
> >
>
> Hey! I thought if you are dividing by zero your answer is undefined. That's
> what they lernt me in skool.
No, zero divided by zero is undefined. Anything other than zero divided
by zero is inifinite. Zero divided by anything other than zero is zero.
--
..Andrew...
From time to time I might take part in discussions in this forum in
which there are points of disagreement. Potential protagonists in those
discussions should note that lack of a response on my part in respect of
any or all of the points raised does not imply a realignment of my
position or opinions to those of said protagonist.
Opinions expressed here are my own, not those of my employer.
Peter Card
>
>
> OK, but let's say that you could get a particle to move at close to the
> speed of light in a vacuum. Then move it into a substance where the
> speed of light is lower while the speed of the particle stays the same.
> Presto, particle going faster than light. I don't know what the
> substance of choice would be or the particle.
Gamma rays will do.
> An electron would be a
> good practical choice but wouldn't it be affected greatly by the
> substance in question? A neutrino would be great if we could control
> them.
The particle decelerates when it enters the slower medium (such as
water) and you get Cherenkov radiation. It is blue. Just stand at the
edge of a used fuel rod storage pond and you can see it for yourself, a
ghostly emanation of blue radiance from the bottom of the pond. It is a
rather spooky experience.
--
----------------------------------------------------------
email Peter...@jet.uk || 10001...@compuserve.com
"But it fell over!"
<> Masquerade contestents at Bucconeer hail the winning entry
Peter Card
>
> Jim Morrison (l...@aa.net) wrote:
> : It seems to me that the secret to interstellar
> : travel lies in discovering FTL communications mechanisms.
>
> communication in your frame of reference (say, sending a signal from
> Jupiter to Earth in 1 second) *will* become communication backward in time
> in other frames -- that is, in a frame moving relative to the 'rest' frame
> of communication, the signal will be received before it's sent. It's
> difficult (for me) to imagine a universe in which such causality
> violations can occur.
On the plus side, ~funding~ the system becomes straightforward, as your
future self can simply supply tomorrow's stock market figures. You just
need to get the breadboard prototype working in the lab first ...
Velovich
>
>Seti, the search for extraterrestial intelligence, doesn't seem to have
>come up with anything. Maybe after a hundred years or so of radio
>transmission ETs develop FTL "subspace" radio. If we knew how to look,
>perhaps the "aether" is swarming with FTL signals.
>
>Cheers,
>--
>Peter
>
>"The only thing wrong with Microsoft is that they have no taste" - Steve
>Jobs.
>
I have always had this Kirk-ism about SETI (as in Capt. Kirk of Star Trek -
the guy that gave us, "Why does God need a Starship?")
What if the other ETIs are, just like us, listening ONLY?
<*> V-Man
A Knight is sworn to Valor
His Heart knows only Virture
His Blade defends the Weak
His Word speaks only Truth
His Wrath undoes the Wicked
Delete the ".CanDo" from my addy to reply!
Frank Crary
Bill Bonde <std...@mailexcite.com> wrote:
>> The mass of an object, according to special relativity is
>> m = m_0/sqrt(1-v^2/c^2)
>> where m_0 is its mass when at rest, v is its velocity and
>> c is the speed of light. (I think... the square root may or
>> may not be correct, but I don't feel like looking it up.)
>> If v=c, then you are dividing by zero, and you get an infinite mass.
>OK, but let's say that you could get a particle to move at close to the
>speed of light in a vacuum. Then move it into a substance where the
>speed of light is lower while the speed of the particle stays the same.
>Presto, particle going faster than light...
Yes and no. The ``speed of light'' (c) in special relativity (and the
above equation) is the speed of light in vacuum. Some odd things
can happen when a particle is moving faster than the speed of
light in a given medium, but that isn't really ``faster than light''
travel according to special relativity.
Frank Crary
CU Boulder
Frank Crary
Hal Hawkins <hhaw...@global2000.net> wrote:
>>>That's about the point my brain shuts down. If the speed of light is
>>>finite, how can it result in, or be partly composed of, an infinite?
>>The mass of an object, according to special relativity is
>>m = m_0/sqrt(1-v^2/c^2)
>>where m_0 is its mass when at rest, v is its velocity and
>>c is the speed of light. (I think... the square root may or
>>may not be correct, but I don't feel like looking it up.)
>>If v=c, then you are dividing by zero, and you get an infinite mass.
>Hey! I thought if you are dividing by zero your answer is undefined.
In a somewhat pedantic sense, yes. Strictly speaking ``infinity'' is
not a number (i.e. it is not an element of the set of real or complex
numbers), so, formally, anything divided by zero is not a well-defined
operation. If you want to worry about that, you have to look at
the limits: m approaches infinity as v approaches c.
Frank Crary
CU Boulder
je...@computer.com
> What if the other ETIs are, just like us, listening ONLY?
Seti has a lot of problems, and as much as I love science fiction and real
life science, I find seti surprisingly frustrating.
It is my understanding that current seti, in terms of the strength of a
signal they could detect, will only succeed if someone is intentionally
sending out such a signal; TV and Radio as we use it do not give out
strong enough signals.
I don't expect anyone is transmitting. Much more likely they have moved
on to other technologies and don't even use Radio.
It is kind of primitive, even by our own standards. Our systems on earth
are evolving towards less 'leakage' - cable systems, microwave, satellite
systems, and so on = less leakage into space.
We would be far better off to do more detailed studies of a much small
number of likely candidates. And to me, the most likely candidate are
star clusters where there are a number of stars relatively close together.
Imagine that we had several stars near us, say 1/10 or 1/5 light year
apart, and they each had planets. It would be wild - the urge to
communicate with life forms and even to travel there would be
irresistable. We ought to identify all such little groups of stars, and
study them for planets and for life. That would interest me far more than
the random listening we are doing now, for signals that are probably not
there.
What would columbus had found if he had tried to listen for life across
the ocean? He would have found nothing at all. He had to go there. In
our time, the analog of 'going there' is to use technology to study a
location. But you have to do it in enough detail to have a chance of
success. It might just be oceans of bacteria, which is probably the most
likely form of life when you do run into it; but it sure would be nice to
know. I love how they 'scan for life forms' on Star Trek. We need
something like that. Maybe the reflection of light off a planet is
different if the planet has atmosphere, than if it does not, in some way
we don't realize; of the reflection is different if it has both atmosphere
and an ocean.
I wish I could be a bigger fan of seti.
jeff
Matthew J Wilson
>>Seti, the search for extraterrestial intelligence, doesn't seem to have
>>come up with anything. Maybe after a hundred years or so of radio
>>transmission ETs develop FTL "subspace" radio. If we knew how to look,
>>perhaps the "aether" is swarming with FTL signals.
>>
> I have always had this Kirk-ism about SETI (as in Capt. Kirk of Star Trek -
>the guy that gave us, "Why does God need a Starship?")
> What if the other ETIs are, just like us, listening ONLY?
Not entirely accurate - I believe that Earth is the brightest radio source
in the solar system these days. We're not actively sending outwards, but
we're not being quiet, either.
--
Matt.
bla...@my-dejanews.com
Your right, but the wavelength's that the earth is as a radio source, gets
lost in all the other radio signals produced naturally. IMHO I would say
SETI's best chances are when we can setup a radio antenna on the far side of
the moon, where it would be shielded from the rest of the low EM radiation
from Earth, this will allow us to look for Low EM radiatiom from other Star
systems.
Greg
J. Kieffer-Olsen, M.Sc.(Eng.)
>
> What would columbus had found if he had tried to listen for life across
> the ocean? He would have found nothing at all. He had to go there. In
> our time, the analog of 'going there' is to use technology to study a
> location. But you have to do it in enough detail to have a chance of
> success. It might just be oceans of bacteria, which is probably the most
> likely form of life when you do run into it; but it sure would be nice to
> know. I love how they 'scan for life forms' on Star Trek. We need
> something like that. Maybe the reflection of light off a planet is
> different if the planet has atmosphere, than if it does not, in some way
> we don't realize; of the reflection is different if it has both atmosphere
> and an ocean.
Considering that it has been established that multi-celled bacteria
represent an advanced stage on the evolutionary ladder, you shouldn't
expect 'oceans of bacteria' a trivial find elsewhere.
--
Jens Kieffer-Olsen
Craig Berry
: Considering that it has been established that multi-celled bacteria
: expect 'oceans of bacteria' a trivial find elsewhere.
"Multi-celled bacteria" is a contradiction in terms (unless you're
referring to simple colonies).
---------------------------------------------------------------------
| Craig Berry - cbe...@cinenet.net
--*-- Home Page: http://www.cinenet.net/users/cberry/home.html
| "Ripple in still water, when there is no pebble tossed,
nor wind to blow..."
Bill Bonde
} }Frank Crary wrote:
} }>
} }> In article <362F06...@together.net>,
} }> John Beaderstadt <be...@together.net> wrote:
} }> >> object increases when it gets faster. At the speed of light it will be
} }> >> infinetly large.
} }>
} }> >finite, how can it result in, or be partly composed of, an infinite?
} }>
} }> The mass of an object, according to special relativity is
} }> m = m_0/sqrt(1-v^2/c^2)
} }> where m_0 is its mass when at rest, v is its velocity and
} }> c is the speed of light. (I think... the square root may or
} }> may not be correct, but I don't feel like looking it up.)
} }> If v=c, then you are dividing by zero, and you get an infinite mass.
} }>
} }>
} }speed of light in a vacuum. Then move it into a substance where the
} }speed of light is lower while the speed of the particle stays the same.
} }good practical choice but wouldn't it be affected greatly by the
} }substance in question? A neutrino would be great if we could control
} }them.
}
} speds in excess of that of light in water. The result is a blue glow
} called Cherenkov (sp)? radiation.
}
Yes, but what I was really wondering about was if you could keep the
particle moving at greater than the local speed of light. Perhaps a
neutrino would do this. What happens at the transition out of the local
media to vacuum when the particle is moving faster than the local speed
of light?
As I understand it, we detect neutrinos by looking for their Cherenkov
radiation in giant water detectors buried deep within the Earth. Is
there a way to look at the transition between superlumina in local media
and sublumina in local media?
Mark Preston
>sel...@geocities.com (Sean Ellis) wrote:
>
>>rcal...@sfu.ca (Ryan Mitchell Calbick) wrote:
>
>>>[... on warps and wormholes...]
>>>
>
>>Add to that the fact that *any* method of FTL travel opens up the
>>possibility of time travel (which in turn implies causal loops,
>>paradoxes and closed space-time trajectories - all Very Bad Things),
>>and even warps and wormholes may be disallowed for reasons we don't
>>yet understand.
>
>
>Not necessarily. You have to appreciate that ANY faster than light
>phenomonon invalidates relativity theory because it is based on the
>assumption that NOTHING travels faster than light.
[snip]
Not true, Paul. First there is the transient energy effect from
virtual particles (the Casimir effect) that allows negative energy
spaces - where light most certainly could exceed 'c'. Then there is
the problem of quantum entaglement, which has effects that certainly
exceed lightspeed. Both are well-know and observable, of course.
-------------------------------------------------
| Mark Preston Ma...@mpreston.demon.co.uk |
-------------------------------------------------
Jessica #84
> I have always had this Kirk-ism about SETI (as in Capt. Kirk of Star Trek -
>the guy that gave us, "Why does God need a Starship?")
>
> What if the other ETIs are, just like us, listening ONLY?
Only the smart ones; the noisy ones are obviously traps (like shark bait)
or just plain stupid (like us).
Jessica #84
.. Formatting Universe. 0.00000000000000000000000000002% complete.
MCZAND
to build a Bussard ramjet within 50 years. That would probably allow trips to
all stars within 5 to 10 lightyears within 20 to 30 years roundtrip wouldnt it?
Replace comspec.org with .com from the address to contact me
The Web Slinger
Zebulon A Haradon
mcz...@aol.comspec.org says...
>
>I havent been following this thread, but I would imagine it would be
possible
>to build a Bussard ramjet within 50 years. That would probably allow trips
to
>all stars within 5 to 10 lightyears within 20 to 30 years roundtrip wouldnt
it?
Can you explain what a Bussard ramjet is please?
>
>Replace comspec.org with .com from the address to contact me
>
>The Web Slinger
--
------------------------------------
Zeb Haradon
My web page:
http://www.acsu.buffalo.edu/~haradon
David C Baker
Bill Bonde wrote in message <363BFD95...@mailexcite.com>...
>Yes, but what I was really wondering about was if you could keep the
>particle moving at greater than the local speed of light. Perhaps a
>neutrino would do this. What happens at the transition out of the local
>media to vacuum when the particle is moving faster than the local speed
>of light?
>
>As I understand it, we detect neutrinos by looking for their Cherenkov
>radiation in giant water detectors buried deep within the Earth. Is
>there a way to look at the transition between superlumina in local media
>and sublumina in local media?
When the particle transitioned out of the medium into vacuum, the local
speed of light would be the speed of light. So, while the particle was
traveling faster than the speed of light in that medium, it never exceeded
lightspeed in a vacuum.
David C. Baker
te...@frontiernet.net
David C Baker
Mark Preston wrote in message <363b94b8...@news.demon.co.uk>...
>>
>>Not necessarily. You have to appreciate that ANY faster than light
>>phenomonon invalidates relativity theory because it is based on the
>>assumption that NOTHING travels faster than light.
>[snip]
>Not true, Paul. First there is the transient energy effect from
>virtual particles (the Casimir effect) that allows negative energy
>spaces - where light most certainly could exceed 'c'. Then there is
>the problem of quantum entaglement, which has effects that certainly
>exceed lightspeed. Both are well-know and observable, of course.
>-------------------------------------------------
>| Mark Preston Ma...@mpreston.demon.co.uk |
>-------------------------------------------------
First, Paul, relativity doesn't state that NOTHING can travel faster than
light. It states that nothing can carry a signal FTL. Mark notes quantum
entanglement. This is certainly a faster than light phenomenon, but it
cannot be used to send a signal (due to Heisenberg relations), so it is not
forbidden by relativity.
David C. Baker
te...@frontiernet.net