Faster than light travel

[Agnostic_Jesus]

I had a thought the other day while watching the science channel shows about black holes.
And from what I understand, black holes can affect the passage of time where time slows down as you get closer to the hole. And once inside the singularity time stops all together, effectively creating a new reality (thats another topic entirely)
Hold onto that thought and chew on this.
According to theories, when the universe was born, "space" expanded faster than the speed of light but the matter within it did not travel faster than the speed of light because it was space itself expanding and not the matter doing the traveling.
Therefore the rules of physics were not broken.
OK so, combining both of these theories, was it the gravity of the collective matter at the beginning of the universe that slowed time down and allowed space to expand faster than the speed of light?
Think of it this way. The matter was not actually traveing faster than the speed of light. It was traveling at whatever pedestrian speed under light speed. But since time was slowed down it has the effect of allowing the matter to go from point A to point B fast than light speed relative to the observer. Speed and time are completely related. If you distort time and slow it down, from an outside observer not being distorted, you will appear to be going faster.
So, in theory, if you could create an artificial singularity and place a probe within it(without destroying it of course) or near it, you could slow that probes relative sense of time down. And when you accelerate the system to the highest speed possible, the probe will experience only that generated speed. But to an outside observer experiencing "normal" time that probe would seem to be going much faster relative to the amount of time distortion the probe is experiencing. So if the probe can reach 20% light speed and the probes time is slowed down by a factor of 10 than the probe would in effect be traveling at twice the speed of light without breaking any laws of physics.
Of course the technology and necessary energies needed to do this experiment are pure fantasy but its the idea extrapolated to this scale that I am curious about.
What do you guys think?

 

[dryson]

A move to the "Unexplained" would be the best observation point for this thread to receive it's sense of time.

 

[origin]

I had a thought the other day while watching the science channel shows about black holes.
And from what I understand, black holes can affect the passage of time where time slows down as you get closer to the hole. And once inside the singularity time stops all together, effectively creating a new reality (thats another topic entirely)
Hold onto that thought and chew on this.
According to theories, when the universe was born, "space" expanded faster than the speed of light but the matter within it did not travel faster than the speed of light because it was space itself expanding and not the matter doing the traveling.
Therefore the rules of physics were not broken.
OK so, combining both of these theories, was it the gravity of the collective matter at the beginning of the universe that slowed time down and allowed space to expand faster than the speed of light?

Couple of points here. There was no matter at the birth of the universe there was only energy - the universe was far too hot for matter to form. After the inflationary stage (which is what I think you are refering too) matter begain to form, which was still in the first second of life of the universe. Currently, far distant galaxies are receding from us faster than the speed of light.

Think of it this way. The matter was not actually traveing faster than the speed of light. It was traveling at whatever pedestrian speed under light speed. But since time was slowed down it has the effect of allowing the matter to go from point A to point B fast than light speed relative to the observer. Speed and time are completely related. If you distort time and slow it down, from an outside observer not being distorted, you will appear to be going faster.

You are right that the speed of the matter in the universe did not exceed the speed of light but that has nothing to do with the rate of expansion of the universe. It is not necessary to come up with a reason such a time dialation to account for the FTL expansion of the universe. Time is always relative and not constant so it just depends on the relative speed (inertial frame) and the gravitational field you are in. But this is about time and motion IN the universe. The speed of light in any situation is constant, even in a universe that is expanding at a rate faster than the speed of light, the speed of light IN the universe will be constant and NO matter can move above or even at that speed.

So, in theory, if you could create an artificial singularity and place a probe within it(without destroying it of course) or near it, you could slow that probes relative sense of time down. And when you accelerate the system to the highest speed possible, the probe will experience only that generated speed. But to an outside observer experiencing "normal" time that probe would seem to be going much faster relative to the amount of time distortion the probe is experiencing. So if the probe can reach 20% light speed and the probes time is slowed down by a factor of 10 than the probe would in effect be traveling at twice the speed of light without breaking any laws of physics. What do you guys think?

No this is incorrect.
If you are in a high gravitational field you would experience time at a 'normal' rate, In other words you would not feel like you were in slow motion. If you were traveling at 20% the speed of light and you measured a the speed of a light wave passing you would read that speed at c (or about 300,000 km/sec), whether it was going in your direction of travel or in the opposite direction.
Now someone outside of the graviational well would see you moving in slow motion. Now if you were traveling at 20% the speed of light the outside observer would see the light traveling at c and for a light traveling along your direction of travel would see that there is a relative velocity between you 2 of 80% of c. In other words c is always c, no matter who measures it and a mass will never reach c regardless of time dialation or length contraction, or gravity well you are in.

 

[csmyth3025]

I had a thought the other day while watching the science channel shows about black holes....

So, in theory, if you could create an artificial singularity and place a probe within it(without destroying it of course) or near it, you could slow that probes relative sense of time down. And when you accelerate the system to the highest speed possible, the probe will experience only that generated speed. But to an outside observer experiencing "normal" time that probe would seem to be going much faster relative to the amount of time distortion the probe is experiencing. So if the probe can reach 20% light speed and the probes time is slowed down by a factor of 10 than the probe would in effect be traveling at twice the speed of light without breaking any laws of physics.
Of course the technology and necessary energies needed to do this experiment are pure fantasy but its the idea extrapolated to this scale that I am curious about.
What do you guys think?

If your thinking about time dilation and the effect it has on a space traveler, it would be just as easy (as a thought experiment) to have the traveler's spaceship go very close to the speed of light. I believe the formula for such a traveler going to the Andromeda galaxy from here (~2.54 million light years) would be:

2.54 million years(sqrt(1-(0.9999999999999999c)^2/c^2))=~2 weeks

For the traveler, he would think his trip lasted about two weeks (a nice liesurely vacation cruise). Of course, if he came back to Earth (another two week cruise to him) he would find that everyone he ever knew died 5 million years ago.

Another major drawback with travelling this fast is that if his spaceship ran into a large grain of sand it would be like getting hit with a nuclear bomb.

Chris

 

[csmyth3025]

Just in case you're thinking that it's impossible for any physical thing to be accelerated to the speed I mentioned (0.9999999999999999c), there's an article on the so-called "Oh-My-God Particle" that can be found here:

http://www.fourmilab.ch/documents/OhMyGodParticle/

This article describes a cosmic "ray" (probably a proton) detected in 1991 that is estimated to have been traveling at 0.9999999999999999999999951c . A proton isn't a spaceship, of course, but this observation at least establishes that such velocities are possible. If you were traveling on this proton, the travel time (for you) from here to the Andromeda galaxy would be a mere 3.5 minutes.

Also, if you could find a way to accelerate constantly at 10 meters/second (about 1g), you could reach this speed in about 50 weeks (Earth time). I don't know the math to be able to figure out how much time you, as the traveler, would experience during this acceleration or your subsequent deceleration before you get to the Andromeda galaxy.

Chris

 

[SpeedFreek]

Also, if you could find a way to accelerate constantly at 10 meters/second (about 1g), you could reach this speed in about 50 weeks (Earth time). I don't know the math to be able to figure out how much time you, as the traveler, would experience during this acceleration or your subsequent deceleration before you get to the Andromeda galaxy.

Chris

It would only take 28 years to reach Andromeda, and that includes slowing down when you get there!

Have a read of this article, it explains all the maths involved.

http://math.ucr.edu/home/baez/physics/R ... ocket.html

 

[theridane]

2.54 million years(sqrt(1-(0.9999999999999999c)^2/c^2))=~2 weeks

In this case you can put c = 1.0 so it gets simplified to t sqrt(1 - beta²), where beta is your speed in terms of c (0 <= beta < c): 2.54e6 sqrt(1 - 0.9999999999999999²) ≈ 2 weeks.

 

[csmyth3025]

Thanks for the link SpeedFreek. It seems Mr. Gibbs did the correct calculation 14 years ago. Boy was I off the mark! It looks like I'd better try harder to understand these equations before I try to use them.

I'm thinking that you can be constantly accelerating at 1.03 ly/yr^2 (to you, as the traveler) and wind up going 0.77c at the end of the first year because to the "stationary" observer your light year distance seems to get progressively shorter (by your traveling measuring rod) and your year seems to get progressively longer (by your traveling clock) as you get closer to c. Does this sound right?

I think the section on fuel consumption is amazing. Also, I noted the caution at the end that essentially warns any would-be spacefarer that he'll be headed for a spaceship melt-down at relativistic speeds.

That whole Star Trek warp drive thing must work altogether differently. I suppose it's a lot easier to go zipping around the galaxy when you don't have to worry about these irksome details.

Chris

 

[SpeedFreek]

It looks like I'd better try harder to understand these equations before I try to use them.

I'm thinking that you can be constantly accelerating at 1.03 ly/yr^2 (to you, as the traveler) and wind up going 0.77c at the end of the first year because to the "stationary" observer your light year distance seems to get progressively shorter (by your traveling measuring rod) and your year seems to get progressively longer (by your traveling clock) as you get closer to c. Does this sound right?

Wow, you are really mixing the frames there, it makes it hard to untangle all the knots! From whose frame of reference do you want to explain the scenario?

 

[ZenGalacticore]

Yeah. 28 years to get to Andromeda, and 28 years back.

But almost 5 million years would've transpired on Earth.

"Agnostic Jesus". :lol:

That's the Jesus in an alternative universe that ran from the Crucifixion! (He just wasn't sure, one way or the other.) :lol:

 

[csmyth3025]

Wow, you are really mixing the frames there, it makes it hard to untangle all the knots! From whose frame of reference do you want to explain the scenario?

I think Mr Gibbs is using the stationary frame of reference for his velocity calculation:

The proper time as measured by the crew of the rocket (i.e. how much they age) will be denoted by T, and the time as measured in the non-accelerating frame of reference in which they started (e.g. Earth) will be denoted by t. We assume that the stars are essentially at rest in this frame. The distance covered as measured in this frame of reference will be denoted by d and the final speed v. The time dilation or length contraction factor at any instant is the gamma factor γ.

To do some example calculations it is easier to use units of years for time and light years for distance. Then c = 1 lyr/yr and g = 1.03 lyr/yr2. Here are some typical answers for a = 1g.
T..................................t.................................d..............................v........................................ γ
1 year.......................1.19 yrs........................0.56 lyrs..................0.77c.....................................1.58
2..............................3.75.............................2.90........................0.97......................................3.99
5..............................83.7.............................82.7.....................0.99993....................................86.2
8............................1,840...........................1,839..................0.9999998..................................1,895
12.......................113,243.......................113,242.............0.99999999996.............................116,641

Chris

 

[SpeedFreek]

"First of all we need to be clear what we mean by continuous acceleration at 1g. The acceleration of the rocket must be measured at any given instant in a non-accelerating frame of reference travelling at the same instantaneous speed as the rocket."

What I was talking about was your description and you seemed to be saying that the reason that the traveller could accelerate at a certain constant rate and reach 0.77c in a year is because of the way the distant observer back on Earth was measuring his ruler and clock from a distance!

I'm thinking that you can be constantly accelerating at 1.03 ly/yr^2 (to you, as the traveler) and wind up going 0.77c at the end of the first year because to the "stationary" observer your light year distance seems to get progressively shorter (by your traveling measuring rod) and your year seems to get progressively longer (by your traveling clock) as you get closer to c.

See what I mean?

But how do we explain it without using the observer back on Earth? After all, the laws of physics should apply inside that spaceship just as they do everywhere else, and the pilot of that spaceship should be able to work out what is going on from his own frame of reference. With acceleration this does get a little complicated, but the easiest way is to take his instantaneous speed and compare it with an observer in an inertial frame of reference, travelling alongside him at the same speed. We can consider his acceleration in terms of a series of these inertial observers, each of which is instantaneously moving at the same speed as him, right next to him!

What we might find is that distance and time for the universe change in his direction of travel, so it is no surprise that he can reach Andromeda in such a short length of time!

It amounts to the same thing in the end, but keeps all the relativistic changes outside of the frame of reference involved - length and time never change for you, they change for someone/somewhere else. Rather than saying it happens because a distant observer sees a change in his ruler and clock, we can say it happens because he sees a change in the universe around him - that's relativity!

You might think it is strange to think of the universe changing around him, but do you think he is really changing relative to the universe? He will tell you that his ruler and clock never changed at all and can perform many in-flight experiments to prove this! :shock:

 

[csmyth3025]

In my first post about Mr. Gibbs' table of time, distance,and velocity I was commenting on the fact that the traveler experienced a time of one year. During that one year period he constantly accelerated at a rate (by his measurement) of 1.03 ly/yr^2. The table indicates that his velocity at the end of that first year, however, is 0.77c, not 1.0c.

The reason for this discrepency is that the elapsed time is initially given in the traveler's frame of reference (1 yr). The distance traveled and the velocity at the end of the first year are given as seen from the stationary frame of reference.

At the end of the first year the traveler will still see himself continuing to accelerate at 1.03 ly/yr^2 (10 meters/sec). He will be able to verify this by allowing a small weight to "fall" from the front of his spaceship to the back of his spaceship. He will find that the weight does, indeed, "fall" to the back of his spaceship at 10 meters/sec^2. The weight becomes, in effect, a co-moving inertial frame of reference at the instant it's released.

He finds this result because his measuring rod has shortened and his clock has slowed down (as seen from the stationary frame of reference) due to relativistic effects. To the traveler, however, his measuring rod and clock haven't changed one bit.

If the traveler does this same experiment at the end of each succeeding year he'll find the same result. To him, he continues to accelerate at 1.03 ly/yr^2 (10 meters/sec). As the table shows, however, his actual acceleration through "stationary" space is very much less than this. In the stationary frame of reference, for the three year period from (his)year 5 to year 8 (over 1000 years to the stationary observer) he accelerates less than 1 mm/sec.

Chris

 

[SpeedFreek]

Sorry, I totally misunderstood your other post, as to the discrepency you were referring to. If you are interested in the reason I misunderstood you, it is that you seem to like explaining the situation in one frame by using measurements made in another.

He finds this result because his measuring rod has shortened and his clock has slowed down (as seen from the stationary frame of reference) due to relativistic effects. It's in this stationary frame of reference that the table gives the traveler's total distance traveled and velocity.

Yes, but it is not in the stationary frame of reference that he finds this result. He never finds that his rod has shortened or his clock has slowed, does he? How can he apply length contraction and time dilation to himself, when all experiments he can perform upon himself tell him that neither the length of his spaceship nor time inside his spaceship have changed?

I now know that this is not the discrepency you were referring to, but his rod has not actually shortened at all and nor has his clock actually slowed. He cannot find these effects, by experiment, so they don't happen in his frame of reference, they happen somewhere else. This can be considered an "issue" with Special Relativity that was addressed with General Relativity.

So when you asked me if your explanation sounded right, I had to say no, even if the part I didn't agree with wasn't the part of your explanation that you were asking about!

As to the part you were actually asking about, the discrepancy as to why you only reach 0.77c rather than 1c, is it because your rod is shorter (as seen by someone else) and your clock runs slower (as seen by someone else)? Or are those relativistic effects merely the consequences of you not being able to travel at c? Is the reason that you cannot reach c that you have mass, and the relativistic effects are a side effect of that?

At the end of a year, he is travelling at 0.77c. On Earth, we calculate he is travelling at 0.77c after 1.19 years. The reason for the discrepancy between T and t are the relativistic effects of time-dilation or length-contraction.

But the reason that he is travelling at 0.77c rather than 1.0c is not due to time-dilation or length contraction - these effects are merely the consequences of relative movement, as seen from somewhere else.

If the traveler does this same experiment at the end of each succeeding year he'll find the same result. To him, he continues to accelerate at 1.03 ly/yr^2 (10 meters/sec). As the table shows, however, his actual acceleration through "stationary" space is very much less than this.

Chris

Yes, of course.

 

[csmyth3025]

I think we're saying the same thing, just in different ways. One thing I'm curious about, though. Everything seems normal to the traveler inside his spaceship. What sort of measurement can he make to determine his ship's position relative to Earth and Andromeda, or its motion through space?

Chris

 

[dryson]

Regardless of how fast or slow you go will not create a time dialated effect as mentioned. If the ship travels at light speed and it takes 28 years to get to Andromeda and 28 years to return to Earth then the total amount of travled time will be 56 years. If the ship goes half the speed of light that means that the travel time would be 56 years of travel time to Andromeda and then another 56 years travel time back to Earth for a total of 112 travel years. If the ship were to travel at twice the speed of light so that the travel time was reduced to 14 years travel time to Andromeda and then 14 years back to Earth then the total travel time would be 28 years. Calculating travel time is not difficult science. What you are refering to is Einsteins brain teaser that is bunk. Einstein said that if you went fast enough that you would eventually end back up at the starting point in which you started out from. This is untrue as space is infinite. Regardless of how fast you went you would continue to travel through space never coming to the end of space or the beginning of space. You are also thinking about the psychological effect which because of the progress of the Earth during the travel to Andromeda would take 28 years the equipment used when you left Earth would be vastly outdated and deemed obsolete by the equipment that was developed while your ship was away for 56 years. Take a look at Moore's Law.Moore's law states that every two years technology will double because of the increase in technology. So if we take the 56 years and divide it by two we will have technology advancing 28 times. This means that the technology that your ship used when you left Earth will be 28 times less efficient than the technology that is currently being used when you arrived back on Earth. Technology would have evolved so much that your equipment would be like using two cans and a string to transfer date between two points when compared to the 100 Tb/s (Terbit/second) transfer rate. The technological progress would also make Earth seem like you have traveled into the future because every one would be more intelligent than the generation that you left behind when you started out on your travel to Andromeda and back to Earth.

 

[SpeedFreek]

Regardless of how fast or slow you go will not create a time dialated effect as mentioned. If the ship travels at light speed and it takes 28 years to get to Andromeda and 28 years to return to Earth then the total amount of travled time will be 56 years. If the ship goes half the speed of light that means that the travel time would be 56 years of travel time to Andromeda and then another 56 years travel time back to Earth for a total of 112 travel years. If the ship were to travel at twice the speed of light so that the travel time was reduced to 14 years travel time to Andromeda and then 14 years back to Earth then the total travel time would be 28 years. Calculating travel time is not difficult science.

You just got all that completely wrong, as gamma, or the relativistic change factor if you like, does not change in a linear fashion as you seem to have assumed.

What you are refering to is Einsteins brain teaser that is bunk. Einstein said that if you went fast enough that you would eventually end back up at the starting point in which you started out from. This is untrue as space is infinite.... {SNIP}

Please keep your ill informed opinions out of the physics forum.

 

[csmyth3025]

Regardless of how fast or slow you go will not create a time dialated effect as mentioned.

Dryson,

From your previous posts we already know that you think Special Relativity and General Relativity are bunk. We're discussing the effects that would be observed if these theories are correct.

Chris

 

[SpeedFreek]

I think we're saying the same thing, just in different ways. One thing I'm curious about, though. Everything seems normal to the traveler inside his spaceship. What sort of measurement can he make to determine his ship's position relative to Earth and Andromeda, or its motion through space?

Chris

Sorry I took so long to reply, Chris.

It took me a while, thinking about this question. At relativistic speeds there are many different effects to consider. Firstly there are the "apparent" effects, like Doppler shift and the aberration of light to deal with.

Presumably, you could measure the spectrum of the light coming in from your destination and make calculations based on the shift. The aberration of light is especially interesting, as objects in front of you apparently recede whilst objects almost directly behind you come into your field of vision! Must make navigation a nightmare, eh?

Then I considered the effects of the Lorentz contraction and time-dilation. After calculating out the effects of aberration from your view, you should calculate that the distance to your destination is contracted in your direction of motion (you can reach a destination was 2.5 million light-years away when you were at rest, but now you are in motion it will only take 28 years, whilst travelling at sub-light speed). What I am saying here is that you should be able to work out how much your view has been distorted, and thus calculate your relative speed.

And then I had a thought.. whilst the relative positions of Andromeda-spaceship-Earth would purely be a question of measuring the apparent view and performing the required calculations, how do we actually measure our motion through space?

I think we calculate it, using our apparent view.

 

[csmyth3025]

From John Walker's C-ship site, it appears that any attempt at navigation would be very difficult at speeds very close to the speed of light. I suppose that a computer could be programmed to compensate for the doppler shift, the Lorentz contraction, and the abberation of light, but in order to do so you would have to know how fast you're going relative to the star field you're in. This might be calculated from the accelerations your spaceship has experienced since you started your trip. I think this would amount to a kind of intergalactic dead reckoning.

On second thought, perhaps the distortions of the star field you're in can be used to determine your (nearly c) velocity.

Chris

 

[alphonsebelly]

I think the idea that it is the increase in mass that makes achieving lightspeed impossible is one of those "teachers lie to you" moments - to avoid having to explain something more complicated.This is the easies to make and can form a sort of engine that allows you to travel as fast or faster then light and you can stear effectively as well.

 

[MeteorWayne]

Wrong.

The incease in mass upon approching light speed is proved in particle accelerators every day.

 

[csmyth3025]

I think the idea that it is the increase in mass that makes achieving lightspeed impossible is one of those "teachers lie to you" moments - to avoid having to explain something more complicated.This is the easies to make and can form a sort of engine that allows you to travel as fast or faster then light and you can stear effectively as well.

There are a lot of people, including teachers, who sincerely believe that as you approach the speed of light (in a vacuum), relativistic mass (rest energy plus kinetic energy) approaches infinity. They believe this because Einstein's Theory of Special Relativity has been rigorously scrutinized by about three generations of scientific researchers and theoreticians and it's been verified by numerous and diverse observations and experiments.

If you feel you have something that's better (but more complicated), I'm sure we would all like you to explain it. Please keep in mind that any hypothesis you propose must be logical (i.e., it must fit in with other accepted science such as Maxwell's equations), self-consistent (no internal contradictions), quantifiable (i.e., it can produce numbers for mass and energy when approaching the speed of light), and testable.

On top of all that you'll have to explain, as MW points out, why numerous particle accelerators operating in diverse countries have, for the past 80 years, consistently shown that sub-atomic particles gain relativistic mass exactly as predicted by Special Relativity (no conspiracy theories, please).

Chris

 

[ramparts]

You could measure redshifts of stars along the direction of travel before and after accelerating.

 

[SpeedFreek]

You could measure redshifts of stars along the direction of travel before and after accelerating.

Or blueshifts, even.