[Q] Apperence of a Space craft while moving

[freeztar]

I use IE , know anything about it?

 

Yeah, it sucks. Get firefox. :D

 

I don't know how to fix it. I looked for a dictionary file in the internet explorer folders on my comp and didn't see anything. You might have to reinstall, so you might as well just install firefox and enjoy safer and faster browsing.

 

I'm going to delete these unrelated posts from the thread to clean it up a bit after I'm sure you've read this. PM me if you have any other questions.

[freeztar]

No wait, it is 300,000,000 meters a second, i was thinking of kilometers there for a seceond!

 

Even if it were theoretically "blinking" at FTL speeds, it should still look continuous I would think. To see the individual jumps, it would have to be jumping at something like 16 per second or lower (at least that's what old movie projectors run at when you can see the blank/black between frames according to the wiki link I posted).

[freeztar]

Ok, if these jumps are not happening in spacetime (in other words, it's not moving from one place to the other) then, I guess, maybe... I'll throw this out there and let someone with a stronger grasp of physics shoot it down...

 

 

The example is slowed down. The ship jumps 6 of red's light-seconds then persists in reds frame of reference for 2 seconds, then jumps another 6 light seconds and persists for 2... and so on.

 

Red would see green disappear then reappear 6 light-seconds away. Red would then see green normally (normal rate of time, normal length, not redshifted) for 2 seconds after which green would disappear again. It reappears six seconds later, now 12 light-seconds away and appears normal for 2 seconds.

 

Green would presumably experience no time between jumps (although this seems somewhat arbitrary). After each jump, red will appear 6 seconds younger and 6 light-second more distant. Between jumps red would appear to move forward in time normally for 2 seconds (not redshifted or time dilated). Then another jump and red is again six seconds younger and 6 light-seconds more distant and moving forward in time normally for two seconds... and so on.

 

If this happen quickly enough, I suppose green would appear to move in slow-motion to red, and red would appear to move in fast-motion in reverse to green.

 

But, again, green is not following the laws of motion or SR between jumps in the above example, and everything I just said may be completely wrong. I'm uncertain.

 

... and I have no idea how to remove a word from the spelling dictionary.

 

~modest

 

That seems reasonable to me Modest if the ship jumps once every 2 seconds. But in this case, it is jumping 1,000 times per second.

 

Btw, what do you use to make your graphics and illustrations?

[modest]

That seems reasonable to me Modest if the ship jumps once every 2 seconds. But in this case, it is jumping 1,000 times per second.

 

I think if it were making a lot of jumps per second (per red's second) and the distance of each jump were greater than the time between jumps then it would appear to move in slow motion (green would appear in slow motion as viewed by red). But, I'm having a hard time considering this... the leapfroging thing doesn't reconcile with SR, so I'm finding it difficult to think about intuitively.

 

Btw, what do you use to make your graphics and illustrations?

 

I did that one in corel draw, but adobe illustrator is equally good at making spacetime diagrams.

 

~modest

[Moontanman]

Ok Modest, I've given it some thought and I see why the space ship would appear to be moving backward, you would see the light from it's last jump before you saw the light from the jump before that and so on, so from the stand point of the observer a space craft traveling faster than light using this method would seem to just appear and then you would see images of it moving away while the space craft it's self was sitting in front of you. That is really cool, If i write this story I'll give you mention in the credits! How would this equate to watching the space craft from the vantage point of high above the solar system as the space craft went from Earth to Pluto? Another really unusual problem would be what a person inside the space craft would see as he traveled along.

[modest]

Ok Modest, I've given it some thought and I see why the space ship would appear to be moving backward, you would see the light from it's last jump before you saw the light from the jump before that and so on, so from the stand point of the observer a space craft traveling faster than light using this method would seem to just appear and then you would see images of it moving away while the space craft it's self was sitting in front of you.

 

Yes, I agree. This would be if the spaceship (green) were moving toward the ground observer (red). The observer would first see the ship bump into them then see the ship get further away observing clocks move backwards on the ship (the clocks jump backwards from jump to jump). On a spacetime diagram, it would look like this:

 

 

Green meets up with red at second six. At seconds 10-12, red sees green as it appeared 6 light seconds away. At seconds 14-16, red sees green as it appeared twelve light seconds away, and so on. After they meet up, they see the ship move away from them seemingly faster than the speed of light would allow.

 

Interestingly, if green jumped such that the trip appeared not much faster than the speed of light from red's perspective then there would be a kind of sonic boom of light (a "photonic boom", I suppose). The images of the approaching ship would superimpose on one another. The photons would bunch together so that an intense flash of light followed green's arrival. In the diagram above, green would be jumping too quickly for this effect to happen.

 

That is really cool, If i write this story I'll give you mention in the credits!

:confused:

 

How would this equate to watching the space craft from the vantage point of high above the solar system as the space craft went from Earth to Pluto?

 

The easiest way to imagine this is to stretch a gigantic white linen cloth from Earth to Pluto. You make a film of a spaceship traveling for, let's say, 10 seconds. The film has 300 frames. You then put the film in a very powerful spotlight-like projector. You stand wherever you want to observe the trip from and play the film on the white linen that is stretched across the distance of the trip.

 

You would move the projector such that the first frame is pointed at earth and the last frame (10 seconds later) is pointed at Pluto. The other 298 frames are evenly spaced between—each frame representing a successive jump in the FTL ship. It only takes 10 seconds to pivot the projector from Earth to Pluto. You then wait for the movie to play.

 

When it does play (when the frames of the movie bounce back to you), that is how the FTL trip will look from your perspective. Shadows and and points of light (like the point at the end of a laser pointer) can travel faster than the speed of light and I believe this thought experiment should work no matter where you're standing. If, for example, you are halfway between Earth and Pluto, you would see the middle of the trip first, then see the start and end of the journey at roughly the same time (if you were exactly halfway then you would see the beginning exactly 10 seconds before you saw the end).

 

Another really unusual problem would be what a person inside the space craft would see as he traveled along.

 

If we're assuming this trip is like the diagram in this post and post #19, (and also assuming the ship is going from Earth to Pluto) then I believe the person in the ship would see clocks on Pluto very quickly move forwards while clocks on Earth very quickly move backwards.

 

~modest

[Moontanman]

Thought experiments are on of my favorites ways to spend time, the human mind can contain much more than reality and thinking of it can give some real insights into reality. I do love expanding my mind by thinking.

[Moontanman]

BTW, what would the universe look like to a person looking out the front and then the rear window of the space ship? If she was looking out the rear window I think the Earth would appear to get closer and out of the front window Pluto would appear to get further away as you approached Pluto. When you arrived Pluto would just appear suddenly and the Earth would disappear.

[modest]

BTW, what would the universe look like to a person looking out the front and then the rear window of the space ship? If she was looking out the rear window I think the Earth would appear to get closer and out of the front window Pluto would appear to get further away as you approached Pluto. When you arrived Pluto would just appear suddenly and the Earth would disappear.

 

I don't think so. During the trip, the spaceship should catch photons normally from both Earth and Pluto since the ship is always in Earth's and Pluto's frame of reference. Earth would get smaller as viewed in the rear window and Pluto would get larger in the front window.

 

The only odd thing would be the reversed direction clocks are moving on Earth as viewed from the ship. Actually, clocks would be moving forward on both planets from the ship's perspective, but with earth each jump would make clocks jump instantly backwards. Like a skipping record that's playing in the forward direction but keeps skipping backwards toward the beginning of the song. If the ship jumps quickly enough from stop to spot then the backward skips would make it look like Earth's clocks are moving in reverse very quickly. Clocks on Pluto would appear to move forward very quickly. Other than that, I don't think there would be any SR-type effects like Earth being redshifted and Pluto being blueshifted.

 

By the way, my movie projector thought experiment isn't exactly correct. I wasn't considering that light would have to travel both ways with the projector (to the screen and back to the observer) and only would travel one way with the FTL ship :D The projector image would take longer to view than the "real" thing.

 

Have you thought about what the person in the ship would feel as they instantly tunnel from one spot to another? If you're thinking about writing a story along these lines then maybe there's something the passengers or the ship would have to do in order to overcome tidal forces or some such... could make for an interesting subplot :shrug:

 

~modest

[CraigD]

Interesting thread – since I don’t pay attention to Q & A threads that don’t stay unanswered for a while, I missed it ‘til now :)

 

I think y’all’ve got the appearance of and from a “hop ship” down pat – lots of peculiar “film playing backwards fast” effects.

 

It reminds me of a magazine-published scifi boardgame I played a few times ca. 1980, where all the ships traveled via short “hops” of distances that varied according to the kind of ship – an interesting game with a lot of potential and simple paper game mechanics, which I’m regrettably unable to recall by name or name and date of publication.

 

I’ve long regretted that the many popular scifi franchises – nearly all of which have some sort of faster-than-light travel somewhat equivalent to what this thread’s discussing – don’t take advantage of the consequences of FTL travel. In particular, Star Trek, which in the late 80s-90s had several episodes that revolved around astronomy, never showed an interesting astronomical event such as a nova or supernova being studied by taking observations of different instants of the event by quickly traveling to different distance from the event to many centuries of observations in a few days or weeks. I vaguely suspect its writers may have had a rule against it.