Thread: Light again people...

Let me start by saying that I totally agree with the fact that we will never break the speed of light but what about the number? 186,000mps, it's just a number after all, isn't it?

I know that light seems to move at the same speed for a person whether they are at a standstill or traveling at 99.9999% of C. I figured that this must be the basis for Einstien's theory that you would need an infinite ammount of energy to travel faster than light and that the mass of said object would become infinite. Or basically (as I like to put it), we will never catch up to and/or overtake a packet of light.

Now, try to bare with me (simple mind here :? ), as we accelerate in our "space ship" the speed of light shoud remain the same for us, i.e. it should continue to move away from us at C. As we approach that magical number (186,000mps) should the speed of light not remain the same? What I'm trying to ask is that even though we are traveling at 185,999.99mps, we should still precieve light to be moving at C even though we are almost at C? (I'll try to clear that up a bit if you think that I'm crazy and taking rubbish ).

If light is always going to be traveling at 186,000mps, nomatter what the curcumstances, then what is stopping us from going beyond (appart from current technology) 186,000mps? If we were to reach 186,000mps then I think that we would not be (technically) breaking C at all as light, from the ships crew point of view, would remain the same as if they were stationary.


I'll do my best to to better explain where I'm going with this but if you feel the need to brand me a heretic and burn me at the stake then I will accept .

The trick here is that by your own frame of reference, you are not moving, and thus you are not traveling at near c.

But by someone else's frame of reference you could be moving at near c, measured with respect to the speed of light as they measure it. From their perspective you are always chasing lightspeed, getting closer and closer to it but never quite catching it.

The point is that there is no absolute frame in which to measure your speed. You can only say what your speed is relative to some frame of reference.

Originally Posted by IrishStu

Let me start by saying that I totally agree with the fact that we will never break the speed of light but what about the number? 186,000mps, it's just a number after all, isn't it?

I know that light seems to move at the same speed for a person whether they are at a standstill or traveling at 99.9999% of C. I figured that this must be the basis for Einstien's theory that you would need an infinite ammount of energy to travel faster than light and that the mass of said object would become infinite. Or basically (as I like to put it), we will never catch up to and/or overtake a packet of light.

Now, try to bare with me (simple mind here :? ), as we accelerate in our "space ship" the speed of light shoud remain the same for us, i.e. it should continue to move away from us at C. As we approach that magical number (186,000mps) should the speed of light not remain the same? What I'm trying to ask is that even though we are traveling at 185,999.99mps, we should still precieve light to be moving at C even though we are almost at C? (I'll try to clear that up a bit if you think that I'm crazy and taking rubbish ).

If light is always going to be traveling at 186,000mps, nomatter what the curcumstances, then what is stopping us from going beyond (appart from current technology) 186,000mps? If we were to reach 186,000mps then I think that we would not be (technically) breaking C at all as light, from the ships crew point of view, would remain the same as if they were stationary.


I'll do my best to to better explain where I'm going with this but if you feel the need to brand me a heretic and burn me at the stake then I will accept .

I see what you are saying, but that would mean that light has a relatively infinate speed. Which is simply not the case.

What is weird to me is that from our vantage point here on earth at our speed we see how far light goes within a year, but if you were travelling near c you'd feel like you arrived at that spot sooner even though people here would still see you take a year.

Originally Posted by Crim5

What is weird to me is that from our vantage point here on earth at our speed we see how far light goes within a year, but if you were travelling near c you'd feel like you arrived at that spot sooner even though people here would still see you take a year.

Yup. Time dilation



Where this:



Is the Lorentz factor .

Would it really require an infinite amount of energy to reach 186,000m/s?

Originally Posted by IrishStu

Would it really require an infinite amount of energy to reach 186,000m/s?

Or acting over an infinite time. Or you could if you had no mass, or any RELATIVE mass.

Originally Posted by IrishStu

Would it really require an infinite amount of energy to reach 186,000m/s?

Yes it would. and depending on your mass you probably wouldnt even reach half of C without ripping a whole in reality and disappearing down your own singularity.

Originally Posted by leohopkins

Originally Posted by IrishStu

Would it really require an infinite amount of energy to reach 186,000m/s?

Yes it would. and depending on your mass you probably wouldnt even reach half of C without ripping a whole in reality and disappearing down your own singularity.

I hope you're not suggesting that as you near the speed of light you'll collapse into a black hole.

Originally Posted by leohopkins

Originally Posted by IrishStu

Would it really require an infinite amount of energy to reach 186,000m/s?

Yes it would. and depending on your mass you probably wouldnt even reach half of C without ripping a whole in reality and disappearing down your own singularity.

If I may, I'd like to put this into a perspective that I do understand. If I can I'd like to (loosly) compare space-time to the Earths atmosphere and the spaceship to a supersonic jet.

As we all know, as the plane approaches the speed of sound a pressure wave builds up on the nose of the jet. Go faster and the jet "punches" through this pressure wave causing the sonic boom. I'd also like to compare the sound barrier to the light barrier (or to a critical speed below C).

Would space-time (atmosphere) somehow act like a force against a moving space ship (jet)? And if so, would the space ship "punch" a hole in space-time (like the jet punching through the sound barrier) as the ship approaced or at C? In effect, causing a temporary black hole or wormhole (or another fenomenon) that only the space ship can enter? I've been thinking of this and it's the only explanation that I can come up with in reply to your response. That if ,somehow, space-time were to start folding up (like water on the bow of a moving ship)?

I know that there are no similarities between air and space-time but this is the only way I can make sence of it.

Your answers are much appreciated! :-D

Originally Posted by Janus

Originally Posted by leohopkins

Originally Posted by IrishStu

Would it really require an infinite amount of energy to reach 186,000m/s?

Yes it would. and depending on your mass you probably wouldnt even reach half of C without ripping a whole in reality and disappearing down your own singularity.

I hope you're not suggesting that as you near the speed of light you'll collapse into a black hole.

Thats exactly what im suggesting! As your energy and thus mass would have increased to a point where you will literally collapse upon yourself.

Originally Posted by leohopkins

Thats exactly what im suggesting! As your energy and thus mass would have increased to a point where you will literally collapse upon yourself.

This is a common misconception, but it is wrong. In your own frame of reference, your mass and energy do not increase, so there would be no tendancy to collapse in a black hole in your frame. If you do not collapse into a black hole in your frame, you don't collapse into a black hole in any other frame.

Originally Posted by Janus

Originally Posted by leohopkins

Thats exactly what im suggesting! As your energy and thus mass would have increased to a point where you will literally collapse upon yourself.

This is a common misconception, but it is wrong. In your own frame of reference, your mass and energy do not increase, so there would be no tendancy to collapse in a black hole in your frame. If you do not collapse into a black hole in your frame, you don't collapse into a black hole in any other frame.

Hmmm. If that is true, then why does a pilot experience G-force? (if his mass and energy have not increased in his referance frame)

Originally Posted by leohopkins

Originally Posted by Janus

Originally Posted by leohopkins

Thats exactly what im suggesting! As your energy and thus mass would have increased to a point where you will literally collapse upon yourself.

This is a common misconception, but it is wrong. In your own frame of reference, your mass and energy do not increase, so there would be no tendancy to collapse in a black hole in your frame. If you do not collapse into a black hole in your frame, you don't collapse into a black hole in any other frame.

Hmmm. If that is true, then why does a pilot experience G-force? (if his mass and energy have not increased in his referance frame)

Angular momentum, it is equivalent to gravity in the feeling. Einstein postulated the idea once that if a spacecraft was an enclosed box with someone in and that ship accelerated with one equivalent G force and if they were later in an enclosed box on Earth then that person would not be able to tell which one they are on.

Hmmm. If that is true, then why does a pilot experience G-force? (if his mass and energy have not increased in his referance frame)

Yes, as swillmer said, it is a result of acceleration. If the pilot is traveling at constant speed, the only G-force he would feel would be the 1G from gravity in a downward direction.

Originally Posted by svwillmer

Originally Posted by leohopkins

Originally Posted by Janus

Originally Posted by leohopkins

Thats exactly what im suggesting! As your energy and thus mass would have increased to a point where you will literally collapse upon yourself.

This is a common misconception, but it is wrong. In your own frame of reference, your mass and energy do not increase, so there would be no tendancy to collapse in a black hole in your frame. If you do not collapse into a black hole in your frame, you don't collapse into a black hole in any other frame.

Hmmm. If that is true, then why does a pilot experience G-force? (if his mass and energy have not increased in his referance frame)

Angular momentum, it is equivalent to gravity in the feeling. Einstein postulated the idea once that if a spacecraft was an enclosed box with someone in and that ship accelerated with one equivalent G force and if they were later in an enclosed box on Earth then that person would not be able to tell which one they are on.

This is only true if you maintain a steady rate of acceleration at 9.8m/s to an infinite speed. If we can't go beyond C then our acceleration must eventually stop therefore making us weightless again (at least from our perspective) which would back-up what Janus said earlier. In our frame of reference we would not gain any mass and the same must be said for the spacecraft that we are travelling in. This is why I question the fact that we may never travel faster than C (or at least the number [186,000m/s]). Maybe I'm not getting the full picture but some things to me don't fit well with this theory. If we don't gain any mass then we must not need an infinate ammount of enerygy to reach (or pass) C. So I ask again, what is stopping us from getting to and/or passing C?

Originally Posted by IrishStu

Originally Posted by svwillmer

Originally Posted by leohopkins

Originally Posted by Janus

Originally Posted by leohopkins

Thats exactly what im suggesting! As your energy and thus mass would have increased to a point where you will literally collapse upon yourself.

This is a common misconception, but it is wrong. In your own frame of reference, your mass and energy do not increase, so there would be no tendancy to collapse in a black hole in your frame. If you do not collapse into a black hole in your frame, you don't collapse into a black hole in any other frame.

Hmmm. If that is true, then why does a pilot experience G-force? (if his mass and energy have not increased in his referance frame)

Angular momentum, it is equivalent to gravity in the feeling. Einstein postulated the idea once that if a spacecraft was an enclosed box with someone in and that ship accelerated with one equivalent G force and if they were later in an enclosed box on Earth then that person would not be able to tell which one they are on.

This is only true if you maintain a steady rate of acceleration at 9.8m/s to an infinite speed. If we can't go beyond C then our acceleration must eventually stop therefore making us weightless again (at least from our perspective) which would back-up what Janus said earlier. In our frame of reference we would not gain any mass and the same must be said for the spacecraft that we are travelling in. This is why I question the fact that we may never travel faster than C (or at least the number [186,000m/s]). Maybe I'm not getting the full picture but some things to me don't fit well with this theory. If we don't gain any mass then we must not need an infinate ammount of enerygy to reach (or pass) C. So I ask again, what is stopping us from getting to and/or passing C?

Closer you get to light speed your mass increases and with that mass requires an ever increasing amount of energy:

m = m0y

Where m = the mass
Where m0 equals the rest mass
Where y = the Lorentz factor

Lorentz factor:



Where y is the Lorentz factor (also called gamma)
Where v is the velocity of an object
Where c is the speed of light

Look at the image below, the closer the speed of light and the higher the Lorentz factor then you get an infinite number because it never reaches c, UNLESS the force acts over an infinite time or has infinite energy because anything with mass will reach infinite mass and 1c and will as a result require infinite mass to keep it there.



PS About that acceleration thing. You are right but I was talking about when something goes in a circular path, as a result they feel the same acceerating graviational 'force' as if they were steadily accelerating, (like on a bus ).

PS About that acceleration thing. You are right but I was talking about when something goes in a circular path, as a result they feel the same acceerating graviational 'force' as if they were steadily accelerating, (like on a bus ).

I get ya mate . Like these future concepts they have of space hotels that rotate to simulate gravity..... A good exaple is A Space Oddesy: 2001.

Originally Posted by svwillmer

Originally Posted by leohopkins

Originally Posted by Janus

Originally Posted by leohopkins

Thats exactly what im suggesting! As your energy and thus mass would have increased to a point where you will literally collapse upon yourself.

This is a common misconception, but it is wrong. In your own frame of reference, your mass and energy do not increase, so there would be no tendancy to collapse in a black hole in your frame. If you do not collapse into a black hole in your frame, you don't collapse into a black hole in any other frame.

Hmmm. If that is true, then why does a pilot experience G-force? (if his mass and energy have not increased in his referance frame)

Angular momentum, it is equivalent to gravity in the feeling. Einstein postulated the idea once that if a spacecraft was an enclosed box with someone in and that ship accelerated with one equivalent G force and if they were later in an enclosed box on Earth then that person would not be able to tell which one they are on.

Interesting, but again I ponder.......Why then does it take more and more energy to go a little bit faster. Energy and mass are equivelants, right ? So that said, if your kinetic energy increases, your mass should increase with it and at the same rate.

Okay, there seems to be basic misconception floating around here, both in the idea that you'll colapse into a black hole if you approach the speed of light and the that you will feel less and less acceleration as you approach the speed of light.

Both stem from neglecting one of the basic principles of Relativity: That there is no absolute or "prefered" frame of reference. (this is known as the "Principle of Relativity" , and actually predates the Theory of Relativity" )

Thus you can only measure velocity relative to some reference frame, and you chose any reference frame you want.

So while an astronaut may have one velocity relative to one reference frame, he can have another velocity relative to a second reference frame, and neither reference frame can be prefered over the other. In fact, you can use the astronaut himself as yur point of reference, in which case, the astronaut's velocity is zero. (he is not moving relative to himself.)

The upshot is that there is no test the astronaut can perform inside his spaceship that tells him how "fast" he is moving. He can look out his window and see objects rushing by, but that only tells him that there is relative velocity difference between the objects and himself, it does not tell him whether it is the objects, himself or both that are "moving".

If you apply this to your accelerating ship. While the astronaut can surely detect that he is accelerating, all this tells him is that he is changing velocities. It does not tell him from what velocity to what other velocity.

For instance, he can tell that he is accelerating at 9.8 m/sec², and thus his velocity in one second has changed by 9.8 m/sec, but he cannot say (in any abslolute sense) at any moment whether it is changing from 0 to 9.8 m/sec or 9.8 m/sec to 0, or even 290,000,000 m/s to 290,000,009.8 m/s or 290,000,009.8 m/s to 290,000,000 m/s. He could even be just changing direction and not altering speed at all. (At this point we will not delve inot GR, and assume that no gravitational fields enter the picture).

So when one say's that an object's kinetic energy increases to infinity, as the object approaches the speed of light, we mean "as measured from the frame which the object is moving at that speed relative to". The same goes for time dilation and length contraction. An object's time slows down and it contracts along the direction of motion, as measured by the frame in which it is moving relative to. Its time does not dilate, nor does its length contract as measured from the frame of the object.

Are we clear on this so far?

From what I understand, the reason a beam of light traveling parallel to you, and in the same direction, still seems to be moving at C is because your perception of time slowed down.

So, if you're traveling one kilometer per hour slower than C, and a beam of light goes past you in the direction you're moving, it is only moving at 1 kilometer per hour relative to you, but because your perception of time is so slow, it seems to be racing by at its usual speed.


Now, I don't know how this relates to say.... a beam of light passing you in the opposite direction of the direction you're moving. It seems to me like you'd perceive that beam of light to be moving at a speed considerably faster than C.

Originally Posted by leohopkins

Originally Posted by Janus

Originally Posted by leohopkins

Thats exactly what im suggesting! As your energy and thus mass would have increased to a point where you will literally collapse upon yourself.

This is a common misconception, but it is wrong. In your own frame of reference, your mass and energy do not increase, so there would be no tendancy to collapse in a black hole in your frame. If you do not collapse into a black hole in your frame, you don't collapse into a black hole in any other frame.

Hmmm. If that is true, then why does a pilot experience G-force? (if his mass and energy have not increased in his referance frame)

You're confusing acceleration with velocity. G force only happens of the plane changes speed or direction. If you change direction while you're going really fast, that means you're accelerating sideways very fast, and accelerating too fast can kill you.

Originally Posted by Janus

Okay, there seems to be basic misconception floating around here, both in the idea that you'll colapse into a black hole if you approach the speed of light and the that you will feel less and less acceleration as you approach the speed of light.

Both stem from neglecting one of the basic principles of Relativity: That there is no absolute or "prefered" frame of reference. (this is known as the "Principle of Relativity" , and actually predates the Theory of Relativity" )

Thus you can only measure velocity relative to some reference frame, and you chose any reference frame you want.

So while an astronaut may have one velocity relative to one reference frame, he can have another velocity relative to a second reference frame, and neither reference frame can be prefered over the other. In fact, you can use the astronaut himself as yur point of reference, in which case, the astronaut's velocity is zero. (he is not moving relative to himself.)

The upshot is that there is no test the astronaut can perform inside his spaceship that tells him how "fast" he is moving. He can look out his window and see objects rushing by, but that only tells him that there is relative velocity difference between the objects and himself, it does not tell him whether it is the objects, himself or both that are "moving".

If you apply this to your accelerating ship. While the astronaut can surely detect that he is accelerating, all this tells him is that he is changing velocities. It does not tell him from what velocity to what other velocity.

For instance, he can tell that he is accelerating at 9.8 m/sec², and thus his velocity in one second has changed by 9.8 m/sec, but he cannot say (in any abslolute sense) at any moment whether it is changing from 0 to 9.8 m/sec or 9.8 m/sec to 0, or even 290,000,000 m/s to 290,000,009.8 m/s or 290,000,009.8 m/s to 290,000,000 m/s. He could even be just changing direction and not altering speed at all. (At this point we will not delve inot GR, and assume that no gravitational fields enter the picture).

So when one say's that an object's kinetic energy increases to infinity, as the object approaches the speed of light, we mean "as measured from the frame which the object is moving at that speed relative to". The same goes for time dilation and length contraction. An object's time slows down and it contracts along the direction of motion, as measured by the frame in which it is moving relative to. Its time does not dilate, nor does its length contract as measured from the frame of the object.

Are we clear on this so far?

So relativly speaking, lets postulate here, if there was nothing else in the universe you could travel at far faster than light because you never actually know what speed you are doing right?

Originally Posted by svwillmer

So relativly speaking, lets postulate here, if there was nothing else in the universe you could travel at far faster than light because you never actually know what speed you are doing right?

If there's 'nothing' else happening, how can there be speed? It always has to be relative to some other event, even if that is a beam of light.

If there's 'nothing' else happening, how can there be speed? It always has to be relative to some other event, even if that is a beam of light.

If go through a peroid of acceleration, you would know it and when it stopped, it would be reasonable to assume that you are moving.

Okay, there seems to be basic misconception floating around here, both in the idea that you'll colapse into a black hole if you approach the speed of light and the that you will feel less and less acceleration as you approach the speed of light.

Both stem from neglecting one of the basic principles of Relativity: That there is no absolute or "prefered" frame of reference.

OK, so can't an object collapse into a black hole from the perspective of the observer in respect to which the object is moving close to the speed of light from?

Originally Posted by KALSTER

If there's 'nothing' else happening, how can there be speed? It always has to be relative to some other event, even if that is a beam of light.

If go through a peroid of acceleration, you would know it and when it stopped, it would be reasonable to assume that you are moving.

To accelerate (or even to accelerate in the sense of feeling gravity or centrifugal force, by the equivalence that forms the basis of the General Theory of Relativity) there has to be something else in the universe to counter it (Newton's law of motion - equal and opposite and all that). Willmer was positing the notion that there is genuinely nothing else in the uiverse. You cannot accelerate in the absence of something to accelerate against.

Originally Posted by kojax

From what I understand, the reason a beam of light traveling parallel to you, and in the same direction, still seems to be moving at C is because your perception of time slowed down.

So, if you're traveling one kilometer per hour slower than C, and a beam of light goes past you in the direction you're moving, it is only moving at 1 kilometer per hour relative to you, but because your perception of time is so slow, it seems to be racing by at its usual speed.


Now, I don't know how this relates to say.... a beam of light passing you in the opposite direction of the direction you're moving. It seems to me like you'd perceive that beam of light to be moving at a speed considerably faster than C.

This second part is why this is not the reason that c is sonstant.

The easiest way od explaining whay light always travels at c with respect to you is this. The speed of light in a vacuum depends on two physical constants The permeability and permittivity of space and only on these two constants. These two constants perform the same role for the magnetic and electric feilds as the gravitational constant performs for the gravitational field, IOW they are constants of proportionality.

If we assume that the laws of physics must be the same for everyone, regardless of their relative motion, then these two fundamental constants must also stay the same, and by extension, the speed of light in a vacuum. (If we assume that they do change with relative motion, then we have to abandon a bunch of other physical laws, like the conservation of momentum.).

So what it comes down to is that the invariance of c is fundamentally "built in" to the universe, and if it wasn't invariant, then the universe would behave a lot different than it does and we likely wouldn't even be here to discuss the issue.

Originally Posted by svwillmer

So relativly speaking, lets postulate here, if there was nothing else in the universe you could travel at far faster than light because you never actually know what speed you are doing right?

No. because at this point the whole concept of "speed" doesn't mean anything. In other words, you have no speed, because you have nothing to have speed relative to.

Originally Posted by KALSTER

If go through a peroid of acceleration, you would know it and when it stopped, it would be reasonable to assume that you are moving.

You could only know that you had a different velocity than you did before you accelerated, This tells you nothing about your absolute velocity. For example, the same accelertion will take you from 0 to some speed, or from that speed to 0. Or it could have changed the direction you are heading without changing your speed at all. It's all the same as far as you are concerened

OK, so can't an object collapse into a black hole from the perspective of the observer in respect to which the object is moving close to the speed of light from?

No, because that would violate the precept that the laws of physics must remain the same as for all inertial frames. IOW, if it collapses into a black hole from one frame, it collapses into a black hole in all frames. conversely if it doesn't collapse into a black hole in one frame, it cannot colapse into a balck hole in any other frame.

For example, assume you have an object the radius and mass of the Earth. If this object collapses into a black hole it will have a radius of less than 1 cm. Now, if the object were to collapse into a black hole in one frame but not another, then it would have a cross section 6378 km in radius in one frame and less than 1 cm in the other. Now imagine that this body is passing through a ring of 6300 km in radius. (remember Lorentz contraction only effect length in the direction of travel, so the ring will have the same radius in both frames.

Thus if the object collapses into a black hole in one frame, it passes through the ring without touching it. But in the frame in which the object does not collapse, the object cannot pass through the ring. This would lead to a physical contradiction.

Ok. So what would happen then to the object from your frame of reference? Would it simply gain mass indefinitely? Would light emanating from it be redshifted beyond detectability so that your frame of reference does not exist anymore? Would its gravity be able to affect other things it passes at close to C?

Originally Posted by KALSTER

Ok. So what would happen then to the object from your frame of reference? Would it simply gain mass indefinitely? Would light emanating from it be redshifted beyond detectability so that your frame of reference does not exist anymore? Would its gravity be able to affect other things it passes at close to C?

First off, it does not "gain mass" it gains energy. In modern science the term mass refers to the invariant or "rest" mass, which does not vary with velocity. Even the term "relativistic mass" is considered passe. What used to be called relativistic mass is now just considered energy.


Secondly, there would be no extra gravitational effect. The reasons for this delve into General Relativity.

there is more to this then just speculations? some real examples or just storys?