Question/theory on faster than light travel

Hello to all. I'm hoping that a few people will chime in here to give me some insight into this idea in my mind. If it were possible to travel faster than light, would there be any way for us to see? Considering that light has to bounce off of an object for our eyes to actually "see," what would happen to our vision if we were traveling faster than the reflection off said object? If we travel faster, there would be no way for the reflection to bounce back fast enough to render vision. Is this an insane idea or something plausible?

reply to post by realeyes


Are you suggesting faster than light can't be seen, hence the object would be invisible, or are you suggesting how we would see our surrounding if we were to travel faster than light?

Great thought

This may help to start to answer your question..

Time Travel - Einstein's Big Idea - Theory of Relativity
www.youtube.com...

If you were to be in a spaceship and aim towards one particular star, and travel faster than light, you would see two types of "strangeness" going on. First would be behind you - there would be no light whatsoever behind you except off to the edges - depending on how much faster than light you are traveling. To the sides and front, I don't believe much would be different - photons would still be entering your field of vision, your relative speed wouldn't affect your perception of that light.

If you traveled from earth and to a far distance planet that is lit up by our sun. You probable wouldn't be able to see it to begin with. It is to far away to bee seen by your eyes. The moon would be to close for you to observe it, because of the speed. Earth would disappear at a instance.

You should be able to see the sun for a second or so. But the sun would probably disappear quite fast as well, because of the distance you have traveled from the sun at that speed.

It is not the light that is our problem. It is the amount of time we travel faster than the light that becomes the problem. It is the wast distance we travel in a very short time that makes it hard for us to observe.

In 1 second you have travel a distance of 299,792,458 m or more if you go faster than light.

Originally posted by Son of Will
If you were to be in a spaceship and aim towards one particular star, and travel faster than light, you would see two types of "strangeness" going on. First would be behind you - there would be no light whatsoever behind you except off to the edges - depending on how much faster than light you are traveling. To the sides and front, I don't believe much would be different - photons would still be entering your field of vision, your relative speed wouldn't affect your perception of that light.

Doesn't that slightly contradict the theory of red & blue shift / doppler effect? As you move away from the Sun, it's light should appear red shifted and in front, light from the star should be blue shifted.
And that makes me think... the Sun would go from being an optical emitter to a radio wave emitter, or would seem to do so, and what's approaching would go from optical, through ultraviolet and up to gamma ray energies. Not sure I'd want to try this experiment.

reply to post by realeyes

If it were possible to travel faster than light, would there be any way for us to see?

Baldly and bluntly, is not possible to travel faster than light. This is because objects increase in mass as they go faster, and when they reach the speed of light their mass becomes infinite. Since mass is proportional to energy, this means the amount of energy needed to accelerate something up to the speed of light is also infinite. So only things that have no real mass (like photons) can travel at the speed of light.

But I can answer your question anyway. The speed of light through a medium is always found to be the same, no matter where and when it is measured. You and I may be whizzing towards each other at a 95 percent of the speed of light, but when you measure the speed of a pulse of light coming from any direction, you will get the same value I do.

In Newtonian physics, time is the same for all observers and the speed of any light should vary depending on who is measuring it. In real life, it doesn't happen like that, though. Instead, we find that the speed of light never changes, but time expands or contracts to make the sums come out right. This is called relativity.

reply to post by realeyes


Well, physics tends to solve this problem by preventing you from going faster than the speed of light - at least in any conventional manner. I am not saying it is impossible to get from point A to point B in less time than it would take a beam of light - but that you are not going to be able to do it in a classical sense.

However, as you approach the speed of light, all objects not relative to your frame of reference (IE - your ship) would be blue-shifted or red-shifted, depending upon whether you were looking forward or backward. Your ship would appear perfectly normal to you (but would be blue-shifted to outside observers looking at your ship approaching head-on, or red-shifted if they were watching you zoom away).

This means that, if you were to go fast enough, the magnetic fields of 60hz power-lines would appear to glow in the visible spectrum (albeit for a very brief moment of time as you zipped past, and at a very low intensity - energy is conserved in that respect). Or, the light from a star would be attenuated into the ELF spectrum (no longer be visible).

One could theorize what would happen up until you hit the limits of plank energy constants. Light approaching would be red-shifted until it violated plank energy at your perspective. Since we don't really know what happens when you start doing that - it's anyone's guess. I would imagine that you would see interactions between you and light would begin to get a little funky - resulting in random particle formation (energy has to go somewhere - plank energy violated or not). Those particles could be ones we are familiar with, or all kinds of stuff we've no knowledge of. At that point - any additional energy expended in an attempt to accelerate will simply yield greater amounts of particle radiation spewing forth from your being. IE - the energy you attempt to put into accelerating will simply 'drop' into existence as particle radiation from outside perspective (and you would simply not go any faster via yours - not that you'd notice, as millions of years would fly by in picoseconds).

Although at that point, the interaction between light and frames of reference would have more in common with the physics of an 'event horizon' than anything else. And I'm simply not formally educated in that respect, nor have I followed much of the research and experiments into this type of situation.

However, one should remember that traveling faster than the speed of light (and thereby 'going back in time') is not the same as reaching point B before a beam of light would have (given the same starting point). "Spooky action at a distance" has demonstrated that instantaneous sharing of information does not alter or violate causality, and therefor going through a "star gate" or something will not amount to time travel, as you are never actually traveling at a velocity greater than the speed of light. If you were to 'quantum shift' to the moon, you would not be able to come back and shake hands with yourself or something weird like that. You would be able to see yourself leave (provided you had a large enough telescope) - but that is no different than saying "hello" - going mach 10 a mile away, and hearing yourself say 'hello.'

People take Einstein's theory of relativity and try to apply it in ways it was never meant to apply.

... OP is asking about first person perspective, not third (and concerning the theory of relativity, there is a huge difference). You won't see objects blue/red shifted, that will depend on how fast and the direction objects are moving *relative to you*.

When viewing everything from a first person perspective, you are simply not moving at all - at least that's one way to put what the second postulate states:

"As measured in any inertial frame of reference, light is always propagated in empty space with a definite velocity c that is independent of the state of motion of the emitting body." Source is wikipedia

Suppose you are riding a car, the fastest car on Earth, and the speedometer reads 50000000mph, if you turn on your headlights light would still travel at c (670616629mph) away from *you* in all directions. This means ligth would still be able to bounce on objects much sooner than you'd reach them.

From your own perspective, only other objects may break speed of ligth, but not you. Hope that clears that part.

To expand on the blue/red shift topic: If your speedometer read 670616628.9 mph, and you looked forward (in the direction you are moving), nothing would prevent you from seeing a red shifted galaxy, for all relativity cares, that galaxy could still be moving at 670616628mph relative to you in the direction you are moving. The other alternative is that if you looked forward (again, in the direction you are moving) you could also see a blue shifted galaxy approaching you at 670616628mph. Neither the direction you are moving nor your speed had any effect on the color (red/blue) you see.

Again, this is all from your own point of view, if you add an external reference frame (a third person looking at you) then things are much different, key thing in this escenario is that 'a+a' is not equal to '2*a'.

reply to post by daniel_g

You won't see objects blue/red shifted, that will depend on how fast and the direction objects are moving *relative to you*.

In principle, you're right, though light from the Sun we've left behind us would be redshifted if we were receding from it fast enough, and light from our destination star would be blueshifted.

On a cosmic scale, everything else would look pretty much the same. On a Galactic scale, though, you should be able to see some interesting Doppler effects.The Galaxy is rotating, which means all the matter in it is describing a more or less circular path around the centre. There is a general 'current', therefore, to stellar motion within the Galaxy, and a spaceship could set off from Solar orbit at any tangent to it. In whichever direction it travelled relative to that motion, the majority of stars, etc. ahead would be blueshifted and a majority behind redshifted; the effect would be most pronounced if the ship were plying 'upstream' against the motion.

As to the stuff all around, the SF writer Frederik Pohl thought travellers would see a rainbow circling the ship, made up of stars going through varying degrees of shift and shining different colours. He wrote a story about it called 'The Gold at the Starbow's End'. I don't know if it was very scientific, though. Relativity can be confusing.

Suppose you are riding a car, the fastest car on Earth, and the speedometer reads 50000000mph, if you turn on your headlights light would still travel at c (670616629mph) away from *you* in all directions.

To the OP and others, here's a visualization that can be really helpful in getting a feel for relativity.

Imagine a ship zooming through space. Watching from Earth, we see it moving at more than three-quarters the speed of light. Suddenly, its atomic rocket motor backfires----and lets off a huge puff of smoke. Now space is a vacuum, there's no air resistance, so what will happen to the gas and particles that make up the smoke?

To the crew watching from the ship, they will expand outward in all directions from the engine nozzle, forming the surface of a rapidly expanding spherical cloud. But to us watching from Earth, the cloud is not only expanding, it is moving in a straight line at three-quarters of the speed of light. That is because it still has the velocity of the ship. In fact, to us on Earth, it looks like the ship is moving through space in the middle of a rapidly expanding, spherical cloud of smoke.

Next, imagine a ship that is powered by some process that emits regular flashes of light 'atomic laser pulses', maybe. Each of these flashes of light is a burst of photons. These photons, like the smoke particles, will expand in all directions from the ship, forming the surface of a spherical cloud. Of course, this cloud is expanding at the speed of light. But--here's the thing--the centre of this cloud isn't moving through space along with the spaceship; it stays put. From our vantage point on Earth, we see a stationary point of light left behind in space, while the ship races away from it at three-quarters the speed of light.

I think it's pretty actually.

reply to post by daniel_g


I think people are really wondering something like: If I'm travelling at the speed of light and turn on my headlight, how fast is the light from my headlight moving? If it's travelling as fast as I am, it won't light up anything in front of me. To appear normal, relative to my speed, it would have to travel twice as fast as I am, in both directions: forward and reflected. However, since it can't travel any faster than I am, what is the significance of "relative" and how can you make that make sense?

And then, if it is relevant to me, I am relevant to it. Therefore if it is red (or blue) shifted to me, I am likewise shifted.

reply to post by abecedarian

The problem is, what seems like commonsense to you just doesn't happen in real life.

When a man in motion turns his flashlight on, the speed of his motion is not added to the speed of the light coming out of the flashlight. The light still travels at boring old c, the speed at which it always travels.

When the beam from his flashlight hits a moving object, the speed of the moving object is not added to the speed of the beam. The light still strikes the object at boring old c, regardless of the speed and direction in which the object is moving.

In other words, the concept of relative velocity doesn't apply to light. It always has the same speed. I flash my flashlight; photons stream away from me at 186,272 miles per second. The flashlight beam illuminates you; the photons strike your face and clothes at 186,272 miles per second. How we are moving relative to each other doesn't count in either case.

Obviously, this plays hell with Newton's equations. Something has to give. According to Einstein, what gives is time, which becomes relative, so that different observers see it running at different speeds. And this has been proved by experiment, over and over and over again, so we know it is true, however counter-intuitive it may seem to us. Scandalous, I know; but those are the rules.

reply to post by realeyes


One theoretical possibility to exceed the light speed limit of special relativity, is the warp bubble drive suggested by the understanding of how gravity warps timespace within general relativity. You would then travel within a local bubble of timespace and hence have no perception of the universe outside it, but within the warp bubble light would behave normally as it is not moving relative to your local timespace bubble.

One thing that plays into this is the belief that the speed of light is dictated by gravity - if you were in proximity to a large object that could distort space time the actual speed of light would change so in essence you could see faster than the static speed of light you see now. But to actually anticipate light IE see faster than light no I don't believe so. Could you warp space to see an object before light could have traveled that distance, yes I believe you could.

reply to post by circuitsports

One thing that plays into this is the belief that the speed of light is dictated by gravity - if you were in proximity to a large object that could distort space time the actual speed of light would change so in essence you could see faster than the static speed of light you see now.

Wrong, I'm afraid. Gravity has no effect on the speed of light in a freely falling frame of reference.

Could you warp space to see an object before light could have traveled that distance, yes I believe you could.

Would rays of light from the object be able to cross the 'warp', or would they have to travel through normal space at the normal speed? If you say they would be able to cross the warp, could you please explain how this is to be achieved?

Originally posted by abecedarian
reply to post by daniel_g

 

I think people are really wondering something like: If I'm travelling at the speed of light and turn on my headlight, how fast is the light from my headlight moving? If it's travelling as fast as I am, it won't light up anything in front of me. To appear normal, relative to my speed, it would have to travel twice as fast as I am, in both directions: forward and reflected. However, since it can't travel any faster than I am, what is the significance of "relative" and how can you make that make sense?

The light travels at the speed of light.

So, it will 'stack up' on itself. Since you can't be traveling at the speed of light, it will simply cause the light you are emitting to increase in frequency (and whatever you pass by will see your headlights as gamma-bursts, or whatever). If you were traveling at the speed of light, it would have an infinite frequency, or an infinitely small unit of space with an infinite amplitude, however you want to look at it. But the universe doesn't work that way. There are defined units of space that are the 'smallest' units of space we have to work with. And there is a maximum amount of energy that such a space can contain.

This is why, at some point, you will hit a 'wall,' at which point, you will never be able to go any faster. Since every object radiates heat (and thus, is emitting in the electromagnetic spectrum), traveling near the speed of light will net a violation of planck (misspelled it earlier) energy units. At which point - I would surmise you would get an eruption of particle radiation from your object approaching C. It should be noted that sources of higher-energy radiation would encounter this limit before lower-energy bodies (IE - a light would encounter this wall before you would).

Now, from your perspective, most things would appear normal. As you go faster, 'time' slows down, therefor, while the light may be blue and red-shifting to its absolute limits, you notice nothing out of the ordinary (although you will probably take note of the awkward behavior of your lights spewing strange particle radiation all over the place - though exactly how this would appear from your perspective is not really something I can predict).

But that wall would eventually be encountered. Attempting to break through it using any classic means of movement would simply result in more particles spewing out from every atom. Which means there are limits to the effects of time-dilation of velocity.

Granted - it's all theory, but I imagine it is what they will find one of these days. I have that much confidence in my analytical abilities.

And then, if it is relevant to me, I am relevant to it. Therefore if it is red (or blue) shifted to me, I am likewise shifted.

The field-effect of gravity is known to travel at - or very similar to - the speed of light. Why and how is not understood - but it stands to reason that, when limited to the speed of light, movement will result in your 'gravity field' (I hate calling it a field - but it's a limitation of language) stacking up on itself, much like a sound-wave stacking up on the leading edges of an aircraft moving near the sound-barrier. While the relationship between gravity and atomic activity is not understood - "time" can be said to slow down for anything traveling at a substantial velocity. Thus - anything traveling at the same speed as you will not appear to be shifted blue, red, or otherwise. It is the other objects that are not moving at the same speed as you that will appear shifted - blue if they are moving towards you (or you towards them) and red if they are moving away.

From this point, you can also consider what would happen if someone were to shine a light on you, and you were to try and pass through it at a speed sufficient for the net blue-shift you experience to violate planck energy?

This is where there are really no experiments with macro-scale objects approaching the speed of light. Anything we collide together at speeds approaching the speed of light are subatomic particles.

Keep in mind that I'm not trying to give a concrete answer - simply trying to demonstrate how I think of the situation, and what I imagine the outcome to be. We don't have many concrete answers on the matter.

As has been mentioned, the speed of light itself would still appear to you to be the same as it is when you are at rest. But the frequency of light is another matter. Items ahead of you would be blue-shifted and objects behind you would be red-shifted. You would not be able to see as you do now, as what once was optical light is now ultraviolet ahead of you and infrared behind you. Ahead of your position, you would actually see heat or even radio waves as light, while behind you you would be seeing ultraviolet radiation or even xrays as optical light.

Of course, it is impossible to surpass the speed of light by anything close to a classical scenario, so the way you exceed that speed limit would no doubt have more profound effects on what you would actually see than the relativistic effects. Example: in a separate 'warp field', you wouldn't be able so see anything beyond your field, and what was in it would look normal as you are not actually moving within that field.

TheRedneck

reply to post by realeyes

If it were possible to travel faster than light, would there be any way for us to see? Considering that light has to bounce off of an object for our eyes to actually "see," what would happen to our vision if we were traveling faster than the reflection off said object?

First of all, it IS possible to travel faster than the speed of light, provided that you qualify the medium that light is traveling through. In a complete vacuum, light does travel at the speed of approximately 186,000 miles per second. However, in a medium other than a vacuum, light slows down to:
(186,000m/s)/(refractive index of the medium).
In such a medium, it is, however, a fact that particles such as electrons can travel faster than light travels in that medium.

reply to post by Aim64C

although you will probably take note of the awkward behavior of your lights spewing strange particle radiation all over the place - though exactly how this would appear from your perspective is not really something I can predict.

Actually, it's well understood. Your lights wouldn't look any different to you at all--they'd still have the same frequency (and speed, of course). Other people's lights would be frequency-shifted, not yours.

Originally posted by abecedarian
reply to post by daniel_g

 

I think people are really wondering something like: If I'm travelling at the speed of light and turn on my headlight, how fast is the light from my headlight moving? If it's travelling as fast as I am, it won't light up anything in front of me. To appear normal, relative to my speed, it would have to travel twice as fast as I am, in both directions: forward and reflected. However, since it can't travel any faster than I am, what is the significance of "relative" and how can you make that make sense?

And then, if it is relevant to me, I am relevant to it. Therefore if it is red (or blue) shifted to me, I am likewise shifted.

edit on 9/14/2010 by abecedarian because: (no reason given)

I explained that, not sure that you understood me though. I'll try to put it simple with the following example:

Suppose the whole universe is nothing more than one baseball, one flahsligth, two notebooks, you, and me. You and I each hold a notebook, but I get to hold the baseball and the flashligth. There are also two universal rules:

1- The speed of ligth is 10mph, no matter what or where.
2- If I throw the baseball, it's speed as seen by you is given by u'=(u-v)/(1-(uv/c))
u is the baseball velocity *I* record on *my* notebook
v is *my* velocity as written on *your* notebook
c is the speed of ligth

So assume I'm approaching you at 4mph, then I turn on the flashligth and throw the baseball at 7mph (from my point of view). Here is what the notebooks would look lke:

My notebook
- Speed of abecedarian = 4mph
- Speed of ligth beam comning out of flashligth = 10mph
- Speed of baseball = 7mph

Your notebook
- Speed of daniel_g = 4mph
- Speed of ligth beam comming out of flashligth = 10mph
- Speed of baseball = 4.17mph

If we ignore all other weird rules we can safely state that's relativity on a nutshell. Because of the equation I gave you, the baseball could never exceed speed of ligth. Because of the first rule you are not allowed to write any other number for speed of ligth - that's basically the second postulate and experiments show it holds true.

Originally posted by TheRedneck
As has been mentioned, the speed of light itself would still appear to you to be the same as it is when you are at rest. But the frequency of light is another matter. Items ahead of you would be blue-shifted and objects behind you would be red-shifted.

Again, that's not true, like Astyanax said your ligths wouldn't look any different. Earth is moving pretty fast relative to the Sun. The Sun is moving pretty fast relative to the Milky Way. The Milky Way is moving somewhat fast in the universe relative to other galaxies. I think we (Earthlings) are going pretty darn fast relative to other stuff in the universe, yet most galaxies in the direction we are moving are red, not blue shifted. If you are the observer, then it's the speed of the other galaxies that matter, not yours. ie. Through your own eyes, you are the center of the universe.