Space combat, travel, living...

[Gota]

Speed of shadow? you gotta be kidding me.

Here is a good example of what it means for shadow to "move" faster than light:
"let's say I'm standing by an omnidirectional
light source. I give it lots of time to send light outward- so that
observers in two different solar systems several light years apart, but
the same distance from me, see it. Now I block my source from one side,
taking a few seconds to do so. That will produce a moving shadow, and
one of the observers will enter the shadow a few seconds before the
other. You could say that the shadow "moved" from one observer to the
other very quickly- much faster than c. Of course, no information is
being carried between the two observers, and no individual photons are
moving faster than c."

[PicassoCT]

And if i appel-lie a magnet to the shadow, this rotates the shadow faster and faster, its called the feynmann spin, after the physicist feynman rotating in his grave when he discovered it. If you spin fast enough, you actually leave the laws of relativity behind, and break through the quantum states, that keep smaller minds confind in the physical universe.

But go ahead, this is fun, and maybee one day much more productive.

[TradeMark]

That doesnt make any sense

[AF]

This sounds like a failure to comprehend relativistic effects

[SirMaverick]

There are things that move faster than the speed of light [...]

No.

There are examples from nature where light moves faster than the speed of light.

No.

You could say that the shadow "moved" from one observer to the
other very quickly- much faster than c. Of course, no information is
being carried between the two observers, and no individual photons are
moving faster than c."

Shadows are a human concept to describe the absence of light (at a certain region).
In your example it's not the shadow that moves. It's that the light beams are blocked differently which only give you the illusion of a "moving shadow". Illusions aren't bound the laws of physics.

[bobthedinosaur]

http://panoptesv.com/SciFi/DamageAverage.html
was interesting.

Although space combat could be instrumental in a galatic / exo-system war, I would imagine that space warfare would be more or less similar to the Pacific theater in WW2 where the "island hopping" of planets plays a more important role, and thus the ground forces would be very important as well as the naval (space) forces. But like that detailed blogg was talking about. logistics would be the most important.

[Gota]

stuff

http://en.wikipedia.org/wiki/Faster-tha ... he_Heavens

http://en.wikipedia.org/wiki/Faster-tha ... nd_shadows

http://en.wikipedia.org/wiki/Faster-tha ... es_above_c

[SirMaverick]

stuff

http://en.wikipedia.org/wiki/Faster-tha ... nd_shadows

Linked in wikipedia: http://math.ucr.edu/home/baez/physics/R ... t/FTL.html (Light spots and shadows paragraph)

These are all examples of things that can go faster than light, but which are not physical objects. It is not possible to send information faster than light on a shadow or light spot, so FTL communication is not possible in this way. This is not what we mean by faster than light travel, although it shows how difficult it is to define what we really do mean by faster than light travel.

And my definition is bound to physical objects, not illusions.

[Gota]

stuff

http://en.wikipedia.org/wiki/Faster-tha ... nd_shadows

Linked in wikipedia: http://math.ucr.edu/home/baez/physics/R ... t/FTL.html (Light spots and shadows paragraph)

These are all examples of things that can go faster than light, but which are not physical objects. It is not possible to send information faster than light on a shadow or light spot, so FTL communication is not possible in this way. This is not what we mean by faster than light travel, although it shows how difficult it is to define what we really do mean by faster than light travel.

And my definition is bound to physical objects, not illusions.

http://en.wikipedia.org/wiki/Illusion

Phase velocity of a wave is not an illusion.

[PicassoCT]

shadow runs as fast as lightspeed, exactly, so if a planet casts a eclipse upon another, it is always the lightsecond or two behind schedule. If the sun went out like a oillatern in a storm, we still would have 8 minutes of sunlight, before the "shadow" would reach us. Sticky to a riddiculosis tobaktopics point? You sure you aint just in it for the trolly? Because i would, as i dont should, if i only could, i surely would.

[Gota]

Picasso Picasso Picasso

[hoijui]

Gota is talking about stuff in a very loose kind of "every-day" definition of "something moving", or.. stuff in general. the critics come from people, which, when hearing "speed of light" automatically switch to exact/scientist mode (assuming they were not already there), cause that is what you usually need when dealing with speed of light.

a shadow here, and a shadow there (some time later), in a scientific way of looking at it, are two totally different things, even if they "are created" by the same light source and object before that. thus, it is not one thing moving. it is so, in a humans mind of course, in "every-day" mode.

what makes no sense at all though, is comparing the speed of light in one medium to the speed of light in an other medium, and then saying light travels faster then the speed of light.

[Gota]

hehe well there are scientists who claim it is possible to move light faster than c and some even claim they have already done it.

[maackey]

I've always thought that light, specifically the speed of it was rather fascinating. If you think about it, light isn't that much different than sound. It's a transverse electromagnetic wave compared to a compressional wave of particles, but very similar nonetheless.

People think similar things of light as they did of sound barrier -- how could you travel faster than sound? It's impossible. But we did it. It is possible and is done all the time now. So is it really impossible for faster than light travel? I don't really think so. The effects of relativity don't really mean that an object increases mass to infinity, or that time stops, but that it just *appears* to increase or stop -- from your frame of reference, because that is the maximum speed at which you can observe the object going away by looking at it.

The observation of light is also interesting, because what if you were blind? You wouldn't know what light was, you couldn't observe it, have any idea what it was, it wouldn't exist at all unless you believed someone else that it was there. There are almost certainly things that we can't observe that travel faster than the speed of light -- we are just blind to them.

(disclaimer: I'm not some super scientist, this is just my personal playful speculation)

[bobthedinosaur]

http://en.wikipedia.org/wiki/Tachyon

[SirMaverick]

Phase velocity of a wave is not an illusion.

"[...] Thus a phase velocity above c does not imply the propagation of signals with a velocity above c."
"The superluminal phase velocity does not violate special relativity, as it carries no information." http://en.wikipedia.org/wiki/Phase_velocity
You learn something new every day...

[Gota]

We will probably go around this limitation eventually in some way that is completely different, definitively not by violating special relativity.

[bobthedinosaur]

Well if you are talking about FTL speed for interstellar travel, it really isn't necessary, because with time dilation long distances won't seem as long to the travelers. It would just make everything else age fast. http://www.thebigview.com/spacetime/timedilation.html

[Teutooni]

Time dilates significantly only very close to the speed of light. So if you don't want to pack food for years, the vessel would still need obscene accelration power (accelerating to c at 9.81m/s^2 takes around a year). Also, at relativistic speeds, to maintain accelration you need more and more power to account for the increased inertia caused by the vessels kinetic energy... Which is impossible since as velocity approaches c the kinetic energy (and inertia) approaches infinity.

We will probably go around this limitation eventually in some way that is completely different, definitively not by violating special relativity.

Yar, for sci-fi purposes, forget relativity. Say it's an outdated theory, later corrected by quantum gravity/whatever technobabble you come up with, which allows FTL (or achieving c without lorentz factor).

[bobthedinosaur]

Close to the speed of light, to me at least, is more feasible than FTL.