Faster than Light / Time travel
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For Harry999,
I crunched the numbers for a Space Shuttle at 17,000 mph, and it works out to about .7 seconds for a week in orbit. After only about 1.4 million shuttle missions, you can retire a year early! (Unless the bean counters hear of this and factor it into the next contract).
I crunched the numbers for a Space Shuttle at 17,000 mph, and it works out to about .7 seconds for a week in orbit. After only about 1.4 million shuttle missions, you can retire a year early! (Unless the bean counters hear of this and factor it into the next contract).
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Something to think about:
I've often wondered if thought ( the thing that rushes around inside your brain ) is faster than light. Discussed it once with an eminent scientist and while he said the idea had not occurred to him he did think it was just possible. The question is though how to measure it ?
KIFIS
I've often wondered if thought ( the thing that rushes around inside your brain ) is faster than light. Discussed it once with an eminent scientist and while he said the idea had not occurred to him he did think it was just possible. The question is though how to measure it ?
KIFIS
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I thought the sum total of mass/energy in the universe was constant, if you travel back in time you would be adding to this total.
Each molecule in your body would already be in use, ie the water molecules could be spread out in rockpools or combined into the bark of a tree somewhere, the trace iron in your blood could be thousands of feet beneath the earth.
The only way to do it would be to transfer a equal amout of mass /energy forward to your time at the same instant you left.
Think time travel is a no no.
Each molecule in your body would already be in use, ie the water molecules could be spread out in rockpools or combined into the bark of a tree somewhere, the trace iron in your blood could be thousands of feet beneath the earth.
The only way to do it would be to transfer a equal amout of mass /energy forward to your time at the same instant you left.
Think time travel is a no no.
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Icarus
I must disagree with your answer to Sky Yachts question. Yes, the person standing in front of the car will see the light being emmitted from the headlights but only at the same time as he is hit by the car because the car is travelling at the same speed as the light.
You say that the driver does not see the light emmitted from his own headlights. This is a false statement. It is a cosequence of Einstiens special theory that the speed of light measured by any observer whether moving or stationary will be the same (c is absolute as TR3 kindly points out). You infer however that in relation to himself, the driver measures the speed of the light emitted from his headlights as zero.
This result contradicts our elementary notion of relative velocities, and it may not appear to agree with common sense. But common sense is intuition based on everyday experience, and this does not usually include measurements of the speed of light.
Incidentally this answers the question posed by the original post. Nothing can travel faster than the speed of light. Suppose a spacecraft is travelling at the speed of light relative to an observer on the earth. If the spacecraft now turns on a headlight the principle of invariance of c asserts that the earth observer measures the headlight beam to be also moving at c. Thus this observer measures the beam and spaceship to be always at the same point in space. Our invarience principle also asserts that the beam moves at c relative to the spaceship, so they cannot be at the same point in space. This contradictory result can only be avoided if it is impossible for the spaceship to move at c.
[ 29 July 2001: Message edited by: Harry999 ]
I must disagree with your answer to Sky Yachts question. Yes, the person standing in front of the car will see the light being emmitted from the headlights but only at the same time as he is hit by the car because the car is travelling at the same speed as the light.
You say that the driver does not see the light emmitted from his own headlights. This is a false statement. It is a cosequence of Einstiens special theory that the speed of light measured by any observer whether moving or stationary will be the same (c is absolute as TR3 kindly points out). You infer however that in relation to himself, the driver measures the speed of the light emitted from his headlights as zero.
This result contradicts our elementary notion of relative velocities, and it may not appear to agree with common sense. But common sense is intuition based on everyday experience, and this does not usually include measurements of the speed of light.
Incidentally this answers the question posed by the original post. Nothing can travel faster than the speed of light. Suppose a spacecraft is travelling at the speed of light relative to an observer on the earth. If the spacecraft now turns on a headlight the principle of invariance of c asserts that the earth observer measures the headlight beam to be also moving at c. Thus this observer measures the beam and spaceship to be always at the same point in space. Our invarience principle also asserts that the beam moves at c relative to the spaceship, so they cannot be at the same point in space. This contradictory result can only be avoided if it is impossible for the spaceship to move at c.
[ 29 July 2001: Message edited by: Harry999 ]
The speed of thought is actually rather slow. Action potentials propagate along the fastest neurons in the human body at only about 120 metres per second. That's only 432km/h.
[ 29 July 2001: Message edited by: stagger ]
[ 29 July 2001: Message edited by: stagger ]
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TR3
I don't pretend to be a professor on the topic. I am but a lowly 2nd year physics student and can't answer your question "why is c absolute?" with any great confidence. But as far as I know it is merely a theory which agrees with experiment. The experiment being the Michelson Morley expt. If you would like further details you'll have to ask and I'd be happy to describe it unless anyones got any objections.
I don't pretend to be a professor on the topic. I am but a lowly 2nd year physics student and can't answer your question "why is c absolute?" with any great confidence. But as far as I know it is merely a theory which agrees with experiment. The experiment being the Michelson Morley expt. If you would like further details you'll have to ask and I'd be happy to describe it unless anyones got any objections.
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HARRY999...The most significant "negative-result"experiment ever performed,This baffling result was put to bed by Einstein after publication of "Special Theory" in 1905.Again this notion that light propagated through the "Ether"until the lack of "fringe-shift" proved otherwise ...Some readers will be unfamiliar with terms such as "Inertial Frames of Reference" if we continue with this thread,then perhaps, we should start with what relativity is all about, for readers who are interested but have not been exposed to the concept before...Any takers???
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If you were in a capsual traveling away from the earth at the speed of light, then if you could watch the earth, it would apear to stand still because you are traveling awayfrom it at the same speed as the light being emitted from it. If you then went faster than the speed of light, the earth would appear to rotate backwards, and it would appear that you are travelling back in time, where in actual fact you are just overtaking the light emitted from the earth.
Another interesting thought is imagine if you were staionary at a point in space, and a space ship that was traveling faster than the speed of light, slowed down and stoped infront of you......It would instantly appear and then a while after, you would see the ship approaching as the light emitted from the ship catches up
Another interesting thought is imagine if you were staionary at a point in space, and a space ship that was traveling faster than the speed of light, slowed down and stoped infront of you......It would instantly appear and then a while after, you would see the ship approaching as the light emitted from the ship catches up
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I believe the two foundation stones of the special theory of relativity are the principle of constancy (Michelson-Morley) and the principle of relativity (Galileo).
1. The velocity of light 'in a vacuum' is the same in all frames of reference (for al observers) moving uniformly, relative to each other,
I am not certain that the post mentioned that the car was being driven in a vacuum?
2. All laws of nature are the same in all frames of refernce moving uniformly, relative to each other.
The speed of light only 'appears' to be constant doesn't it? it is the measuring instruments that change from one frame of reference to the other in just such a way that the speed of light appears to be the same.
1. The velocity of light 'in a vacuum' is the same in all frames of reference (for al observers) moving uniformly, relative to each other,
I am not certain that the post mentioned that the car was being driven in a vacuum?
2. All laws of nature are the same in all frames of refernce moving uniformly, relative to each other.
The speed of light only 'appears' to be constant doesn't it? it is the measuring instruments that change from one frame of reference to the other in just such a way that the speed of light appears to be the same.
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Vapour trail,for every point along a given line that this ship would pass,then,light would reflect from the ship from each individual point it passed.So, the net effect is perhaps a large tail appearing in the objects wake...but a much smaller object...
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Icarus
Why would the measuring instruments "change"? wouldn't that defy your second postulate?
If the speed of light only "appeared" to be constant then there would be no problem with the absolutness of time. The fact that the speed of light is the same with respect to two observers in different inertial frames leads us to the conclusion that the two observers do not share the same time scale hence time travel. Also isn't the speed of light in a vacuum near as damn it the same in air?
Howzat? Maybe I'm wrong - I look forward to your reply
Why would the measuring instruments "change"? wouldn't that defy your second postulate?
If the speed of light only "appeared" to be constant then there would be no problem with the absolutness of time. The fact that the speed of light is the same with respect to two observers in different inertial frames leads us to the conclusion that the two observers do not share the same time scale hence time travel. Also isn't the speed of light in a vacuum near as damn it the same in air?
Howzat? Maybe I'm wrong - I look forward to your reply
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KIFIS.
It may sound like it comes from a Richard Bach story but I like the idea that thought is not only faster than light but more all-encompassing. Thus, an idea or piece of inspiration is a finished model and already exists, you've just got to make it exist for you! The Bach book 'ONE' is a quite understandable explanation of the many worlds theory.
Tony Draper
The mass/energy in the universe are constant in theory and relativity theory is based upon it being a closed system, which it is not; its expanding and we're missing nearly 90% of what was present at the Big Bang. Yes everbody stood well back!
It may sound like it comes from a Richard Bach story but I like the idea that thought is not only faster than light but more all-encompassing. Thus, an idea or piece of inspiration is a finished model and already exists, you've just got to make it exist for you! The Bach book 'ONE' is a quite understandable explanation of the many worlds theory.
Tony Draper
The mass/energy in the universe are constant in theory and relativity theory is based upon it being a closed system, which it is not; its expanding and we're missing nearly 90% of what was present at the Big Bang. Yes everbody stood well back!
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Icarus,
"The velocity of light 'in a vacuum' is the same in all frames of reference (for al observers) moving uniformly, relative to each other,
I am not certain that the post mentioned that the car was being driven in a vacuum?"
Just a quick question; If the speed of light is considered as constant then why does it matter if this is in a vacume or not? surely this would therefore make no difference to c?
AA
"The velocity of light 'in a vacuum' is the same in all frames of reference (for al observers) moving uniformly, relative to each other,
I am not certain that the post mentioned that the car was being driven in a vacuum?"
Just a quick question; If the speed of light is considered as constant then why does it matter if this is in a vacume or not? surely this would therefore make no difference to c?
AA
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Hey guys... Lets not get hung up on semantics,SMUDGER has raised a super topic and if anyone out there can explain how this universe works. Then I, for one will be an avid reader...Just think of those long flights when all the papers are read,Tell us what you think...who knows perhaps we can contribute to the search for the "Theory of Everything"...
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Yes but if the missing mass has been converted to energy ie, hydrogen to helium,the excess mass converted to energy this has been spread around, entropy, but it will still be there surely.
It always seemed to be a better reason for time travel being impossible than the grandfather paradox.
It always seemed to be a better reason for time travel being impossible than the grandfather paradox.
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This is a facinating topic isn't it guys?
TR3 has already mentioned time dilation, well try to get your heads round this one... length contraction - If L0 is the distance between two points that are at rest in a particular frame of reference L0 is called the proper length. If this frame moves with constant speed u relative to a second frame and the distances are measured parrallel to the motion, the distance L between the points as measured in the second frame is
L=L0root(1-sq(u/c))
So if our aeroplane could travel at c its length would become zero. And I have stated in a previous post that its mass would become infinite. So that means that our aeroplane would become infinitely dense- a singularity if you will. And you know what that means don't you? A black hole.
AA I guess that the actual speed of the beam within a medium remains c. I account for the apparent slowing of the speed of the light in that the distance travelled by the light in a medium is increased as a result of reflections off molecules of the medium. The general direction of the beam remains the same within the medium. Note that the spaces between the molecules are vacuum.
[ 29 July 2001: Message edited by: Harry999 ]
TR3 has already mentioned time dilation, well try to get your heads round this one... length contraction - If L0 is the distance between two points that are at rest in a particular frame of reference L0 is called the proper length. If this frame moves with constant speed u relative to a second frame and the distances are measured parrallel to the motion, the distance L between the points as measured in the second frame is
L=L0root(1-sq(u/c))
So if our aeroplane could travel at c its length would become zero. And I have stated in a previous post that its mass would become infinite. So that means that our aeroplane would become infinitely dense- a singularity if you will. And you know what that means don't you? A black hole.
AA I guess that the actual speed of the beam within a medium remains c. I account for the apparent slowing of the speed of the light in that the distance travelled by the light in a medium is increased as a result of reflections off molecules of the medium. The general direction of the beam remains the same within the medium. Note that the spaces between the molecules are vacuum.
[ 29 July 2001: Message edited by: Harry999 ]
A tangent here but…
Mr moto - can I assume that you're a dualist; i.e. you don't believe that mind and brain are one and the same thing. Or perhaps you didn’t see my little post on the previous page. I just pointed out that action potentials propagate along the fastest neurons in the human body at only about 120 metres per second. That's only 432km/h. So if thoughts are neuronal activity then they are rather slow and many contributors to this forum routinely travel faster than the speed of thought.
Mr moto - can I assume that you're a dualist; i.e. you don't believe that mind and brain are one and the same thing. Or perhaps you didn’t see my little post on the previous page. I just pointed out that action potentials propagate along the fastest neurons in the human body at only about 120 metres per second. That's only 432km/h. So if thoughts are neuronal activity then they are rather slow and many contributors to this forum routinely travel faster than the speed of thought.
Cunning Artificer
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There's one major problem for devotees of Einstein's theories. Einstein, being a scientist, defined his frames of reference; those things to be considered as given in order for the theory to work. A constant value for 'c' to all observers was one of them. So, 'c' is a constant for all observers simply because the theory requires it to be so. Subsequent experimental testing confirms that the theory explains the physical world better than Newton's Laws, while conveniently confirming Newtonian physics for the everyday velocities experienced by human beings. Relativity moves on to new technology, in applications such as satellite navigation, with corrections for relativity effects routinely factored into GPS navigational computations.
The problem now is in the observing, since all human observers live within the framework of space and time. For any development to the next stage, (as when Einstein stood on Newton's shoulders so that he could see further) a new frame of reference must be developed. Effects that seem to be beyond Relativity are already being observed. Further advances in physics will come from explaining these events. Personally, I'm not convinced that the velocity of light cannot be exceeded, though I don't see how super-velocities could be observed. But then I'm not a Particle Physicist, just a humble avionics technician.
Nevertheless, its interesting that even humble instrument bashers like me need to understand at least a bit about relativity as part of my job. Everyday acceptance and use is the driving reason for scientific research. No matter how esoteric it may be at the outset, good science eventually becomes practical. The mind boggles at what might come from chaos theory. Oh! I forgot! The weather forecasters already use that to help predict the movement of storms.
Mark my words. 'c' is NOT a constant in the REAL universe...
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Through difficulties to the cinema
The problem now is in the observing, since all human observers live within the framework of space and time. For any development to the next stage, (as when Einstein stood on Newton's shoulders so that he could see further) a new frame of reference must be developed. Effects that seem to be beyond Relativity are already being observed. Further advances in physics will come from explaining these events. Personally, I'm not convinced that the velocity of light cannot be exceeded, though I don't see how super-velocities could be observed. But then I'm not a Particle Physicist, just a humble avionics technician.
Nevertheless, its interesting that even humble instrument bashers like me need to understand at least a bit about relativity as part of my job. Everyday acceptance and use is the driving reason for scientific research. No matter how esoteric it may be at the outset, good science eventually becomes practical. The mind boggles at what might come from chaos theory. Oh! I forgot! The weather forecasters already use that to help predict the movement of storms.
Mark my words. 'c' is NOT a constant in the REAL universe...
**********************************
Through difficulties to the cinema