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Thread: The speed of light

  1. #1 The speed of light 
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    Just wondering, How do we know that the spped of light is the fastest? It could be that light is the fastest speed that we know of, but not somewhere else in the universe.


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    we know nothing for certain, its all just theories.........
    and because Einsten said so but years from now Einstein will probly be proven wrong like Newton was......


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  4. #3 Re: The speed of light 
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    Quote Originally Posted by Dagg
    Just wondering, How do we know that the speed of light is the fastest? It could be that light is the fastest speed that we know of, but not somewhere else in the universe.
    I think Einstein is may be right on this one. BUT might a light beam approaching a black hole speed up? Does anyone know of any experimental observation?

    Whilst the LIGHT from an object may have a limited speed the object itself could be travelling faster that its light. (Hence the blue shift of the Doppler effect)
    A jet plane can travel faster than it's sound so why can't an object travel faster than it's light?
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  5. #4 Re: The speed of light 
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    Quote Originally Posted by harryschneider
    A jet plane can travel faster than it's sound so why can't an object travel faster than it's light?
    Because that is the way the laws of the Universe operate. As the object moves ever faster its mass increases, requiring even more energy to accelerate this. It can only approach the speed of light asymptotically: it would never quite reach it, even if you were to supply the energy. In consequence it is certainly not going to travel faster than light.
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  6. #5 Re: The speed of light 
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    I think Einstein is may be right on this one. BUT might a light beam approaching a black hole speed up? Does anyone know of any experimental observation?

    Thats' a curious question and i have no idea of the answer. I mean a black hole's gravity can prevent light escaping but can it draw it in faster than it is already travelling? If anyone does have an answer, i'd love to hear it.
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  7. #6 Re: The speed of light 
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    Quote Originally Posted by GrowlingDog
    I think Einstein is may be right on this one. BUT might a light beam approaching a black hole speed up? Does anyone know of any experimental observation?

    Thats' a curious question and i have no idea of the answer. I mean a black hole's gravity can prevent light escaping but can it draw it in faster than it is already travelling? If anyone does have an answer, i'd love to hear it.
    It can only blue-shift. It is still traveling at the same speed though, and always will.
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  8. #7 Re: The speed of light 
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    [quote="Ophiolite"]Because that is the way the laws of the Universe operate.[quote]
    Yes I understand the theory but I am still uneasy at accepting blindly the implications just because Einstein said so. There is still a possibility that there are some unseen/unknown factors which should yet be taken into account. What they could be - I have no idea!
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  9. #8 Re: The speed of light 
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    Quote Originally Posted by KALSTER
    Quote Originally Posted by GrowlingDog
    I think Einstein is may be right on this one. BUT might a light beam approaching a black hole speed up? Does anyone know of any experimental observation?

    Thats' a curious question and i have no idea of the answer. I mean a black hole's gravity can prevent light escaping but can it draw it in faster than it is already travelling? If anyone does have an answer, i'd love to hear it.
    It can only blue-shift. It is still traveling at the same speed though, and always will.
    So, while a star can speed up say, a comet as it gets closer to it and stop it completely if the comet hits the sun, all from the effects of gravity, light cannot be drawn in faster, no matter how strong the gravity? Also, if a black hole can stop or trap a beam of light, can something with a gravitational effect a little less than a black hole slow a beam of light down a lot? I feel and probably sound like a 5th grader, i'm sorry.
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  10. #9 Re: The speed of light 
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    Quote Originally Posted by GrowlingDog
    Quote Originally Posted by KALSTER
    Quote Originally Posted by GrowlingDog
    I think Einstein is may be right on this one. BUT might a light beam approaching a black hole speed up? Does anyone know of any experimental observation?

    Thats' a curious question and i have no idea of the answer. I mean a black hole's gravity can prevent light escaping but can it draw it in faster than it is already travelling? If anyone does have an answer, i'd love to hear it.
    It can only blue-shift. It is still traveling at the same speed though, and always will.
    So, while a star can speed up say, a comet as it gets closer to it and stop it completely if the comet hits the sun, all from the effects of gravity, light cannot be drawn in faster, no matter how strong the gravity? Also, if a black hole can stop or trap a beam of light, can something with a gravitational effect a little less than a black hole slow a beam of light down a lot? I feel and probably sound like a 5th grader, i'm sorry.
    The thing you have to ask is the light speeding up relative to who? If light is travelling at c relative to us it can't speed up because time slows down. It may be convering a greater distance relative to us but the time slowing it takes relative to us near a black hole means the light is still going at c.
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  11. #10 Re: The speed of light 
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    Quote Originally Posted by GrowlingDog
    So, while a star can speed up say, a comet as it gets closer to it and stop it completely if the comet hits the sun, all from the effects of gravity, light cannot be drawn in faster, no matter how strong the gravity?
    Light does not slow down or speed up, it merely loses or gains energy. So, if light is being drawn towards a gravity well, it will increase in energy, and blueshift. If it manages to climb out of the gravity well, it will decrease in energy and move towards the red spectrum.

    Light will continue to travel at c as it's speed depends entirely on the properties of space: permittivity (electric) and permeability (magnetic).
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    So, while a star can speed up say, a comet as it gets closer to it and stop it completely if the comet hits the sun, all from the effects of gravity, light cannot be drawn in faster, no matter how strong the gravity? Also, if a black hole can stop or trap a beam of light, can something with a gravitational effect a little less than a black hole slow a beam of light down a lot? I feel and probably sound like a 5th grader, i'm sorry.
    When light is "sucked" into a black hole, it does so because of the curvature of space-time (gravity). So all the light does is follow the path of the curvature. The same happens inside a black hole, where space is curved to such a degree that light can't advance beyond the event horizon.
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    Quote Originally Posted by KALSTER
    So, while a star can speed up say, a comet as it gets closer to it and stop it completely if the comet hits the sun, all from the effects of gravity, light cannot be drawn in faster, no matter how strong the gravity? Also, if a black hole can stop or trap a beam of light, can something with a gravitational effect a little less than a black hole slow a beam of light down a lot? I feel and probably sound like a 5th grader, i'm sorry.
    When light is "sucked" into a black hole, it does so because of the curvature of space-time (gravity). So all the light does is follow the path of the curvature. The same happens inside a black hole, where space is curved to such a degree that light can't advance beyond the event horizon.
    Cool! thank you Kalster. Learning, ever learning.
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  14. #13 Re: The speed of light 
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    [quote="harryschneider"][quote="Ophiolite"]Because that is the way the laws of the Universe operate.
    Yes I understand the theory but I am still uneasy at accepting blindly the implications just because Einstein said so.
    I think the issue is that it is not just because Einstein said so, but because many studies of phenomena, based upon observation, experimentation and theoretical investigations, confirm the validity of the idea. As you note, something different may turn up. That is why the conclusions of science are provisional. However, at this point there seems an infinitesimally small likelihood of such being the case.
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    The unchangability of the speed of light is more than just theory. It's the main idea behind accurate clocks on moving vehicles (sattelites particularly) and as a result, the only reason that GPS systems work without needing to have radio transmitters on the ground every few hundred miles.
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    I read that if you were to get pulled into a black hole and hit the event horizon, you would gain an infinite amount of density, therefore be everywhere in the universe at the same time, making you travel infinitely faster than light. This would although, only cause time dilation, so that you would see the universe die in a second-with everything completely blue shifted to its deepest tone.
    Of all the wonders in the universe, none is likely more fascinating and complicated than human nature.

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  18. #17 Re: The speed of light 
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    Quote Originally Posted by Harry Schneider
    I think Einstein is may be right on this one. BUT might a light beam approaching a black hole speed up? Does anyone know of any experimental observation?
    Time to place yourself in a 'mind' experiment! If Einstein did it so can you!
    For a moment forget your training - I don't want you to be a conduit for other peoples ideas, theories or therum. Please - what do YOU think.

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  19. #18 Re: The speed of light 
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    Quote Originally Posted by GrowlingDog
    So, while a star can speed up say, a comet as it gets closer to it and stop it completely if the comet hits the sun, all from the effects of gravity, light cannot be drawn in faster, no matter how strong the gravity? Also, if a black hole can stop or trap a beam of light, can something with a gravitational effect a little less than a black hole slow a beam of light down a lot? I feel and probably sound like a 5th grader, I'm sorry.
    I recall that when a black hole is directly in between us and a distant galaxy the visual effect is of a cluster of galaxies whereas there is only the one.

    Have any observations been made to show that light from one image of the galaxy has traveled faster (or slower) than that of a different image of the same galaxy.

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    I know we have been able to slow down light and also speed it up in labs through fiber optics, special materials and such, and that black holes bend space causing the light to appear to curve around the event horizon of the black hole. But as for giving you infinite mass? I think you would just appear to be stretched continuously around the black hole, but in reality the amount of matter that makes you up would remain the same untill it got sucked into the black hole and converted to energy.
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    hi guys & gals!

    a little while ago a weird theory popped in my head.
    what if the speed of light (and of course all other electromagnetic radiation) is only apparent to us? i've got myself thinking maybe light only has a direction in space and travels in time.
    therefore, the "c" is not a speed of light but it's actually a speed of time.

    what do you think of that?

    cheers!
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    its a thry that we can use quantum tunneling to break the speed of light
    i found this artical to back up what im saying! :-D
    http://www.engadget.com/2007/08/16/g...peed-of-light/
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    It depends on how you look at it. I believe that the physical process in itself, or entity called time does not exist; though, time is apparent through the motion of other objects. Time is defined by the normal speed at which things occur to us. Light is only a maximum contrast to what we normally observe, making it through our perspective the "top speed of time" which is really only the top speed of any energy, since time and energy/speed of an object seem to be the same.
    Of all the wonders in the universe, none is likely more fascinating and complicated than human nature.

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    c is the constant. i am curious to know, hypothetically speaking, if we observed light traveling at us from two objects in space, a star in the western sky and another in the eastern sky, both at equal distance from our point of reference on earth. would the gap in distance between the two stars close at a rate exceeding c? (2 x c) ?
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    I'm not that great in this area of knowledge... but, there is one thing you might have to take into consideration...

    All light travels the same, whether it is a radio wave or a gamma ray.
    This is because, as you all know, light has a frequency, because it is a wave. As a red shift happens, the frequency becomes longer, and thus, the speed stays the same. The same thing happens with a blue shift, and ultraviolet rays...

    This is just a theory... If i am wrong, please tell me...
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    Einstein had to make certain assumptions. Otherwise, it would be impossible to explain his theory of relativity. He had to assume that the speed of light was an absolute. By doing so, he was able to explain what is true 99.999999999999999999999999999999999% of the time. What happens the other 0.000000000000000000000000000000001% of the time is pure conjecture.
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    I know this (the diagram by yours truley) is bound to fail, it's way too simple, I kinda did it... just to find out why it will NOT work.

    Edit: WAIT WAIT WAIT, I'm such a friggin' IDIOT, it won't work because the whole Solar System is flying through space, and with the empty vacuum infact being filled with Dark Energy and Matter etc., it's like the Solar System is contained within a Carriage of a Train moving along... a Train Track >_> Do not relate this to the Train metaphor further below, lol. Infact, nearly everything in the Universe isn't standing still, it's all moving around each other (according to the Masses of objects), also expanding as well. SO... there's the idiocey in my diagram, the great Attractor (considering the "size of the Universe" again) could be moving extremely fast as it is.

    So then it stands to reason, something somewhere in the Universe, is infact moving MUCH slower in comparison to our Earth. So then my Diagram comes into play again, as the Mysterious Giant Mass would infact still be moving in relation to the Earth significantly slower (Perhaps it's main drive of motion is only the continuous expanse of the Universe).

    ... so my Diagram isn't wrong, it just needs even MORE, many more Giant Masses in the chain, rotating around each other.

    To conclude, nothing is truley still and stationary in the Universe, with the exception of possibly the Centre of the Universe where the Big Bang occured... and presumably it's still extremely dense there where stuff is still trying to expand. The centre of that Denseness... is the definition of stationary. Oh god, tell me, these are all lies aren't they? Say it like Arnold Schwarzenegger does in his Sound boards, "These are all lies!".

    ... Anyway...

    But something did occur to me, as someone mentioned it similar elsewhere in the thread, allow me to quote someone (these aren't my words, and neither from anyone on this Forum), just to help illustrate a point:

    Dogfighting is useless in a Jet that flies at Mach 1 or higher. Why?
    Because the jet would be travelling faster then the Bullet, and thus the bullets would never leave the barrel and jam up inside.
    Obviously wrong, it's like standing in a Train, hanging you arm out the window while it travels 60Mph along the tracks, and you lob a stone forward the direction it's heading. In relative to the Earths floor, the stones traveling 65Mph or whatever, and then naturally slows down due to wind resistance.

    I can't imagine how on Earth it's possible, but could one not "Hoik" something onto a Beam of Light, and have it "Jump" off in the direction it's heading?
    We send Data down Fibre Optics, and computers interpret it as information, COMPLETELY going off into stupidness, could we not emulate something in the Beam of Light to interact with "The Computer Of Space", which would react with an aspect of Space in such a way to increase the speed of the said something, whilst it piggybacks the Light?

    I realise the Fibre Optics part and onwards is utterly ridiculous, but the concept it's based on...?

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    In theory, the speed of light is an absolute. In that case, the bullet could never leave the chamber. At Mach 1, in the "dogfight," the other pilot would not be able to hear the shot but would most certainly feel its effect.

    You may have inadvertently brought up another question, Ruro. Does gravity exist? Is the attraction between objects an actual "gravitational force" or is it something else? Could it be that space is bent causing the attraction?

    If you place a cue ball on a trampoline, you will cause curvature of the surface. If you then place a marble on the trampoline, it will be drawn to the cue ball. Is that a matter of gravity or simply "gravitation" to a greater depression in the surface? If you then place a bowling ball on the trampoline, both the marble and the cue ball will, most assuredly, "gravitate" towards it. Is it the mass of the object or the depression of space that caused this?
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    Quote Originally Posted by uncommonman
    You may have inadvertently brought up another question, Ruro. Does gravity exist? Is the attraction between objects an actual "gravitational force" or is it something else? Could it be that space is bent causing the attraction?

    If you place a cue ball on a trampoline, you will cause curvature of the surface. If you then place a marble on the trampoline, it will be drawn to the cue ball. Is that a matter of gravity or simply "gravitation" to a greater depression in the surface? If you then place a bowling ball on the trampoline, both the marble and the cue ball will, most assuredly, "gravitate" towards it. Is it the mass of the object or the depression of space that caused this?
    Thanks for the response to my rabble uncommonman. I have read in a couple of other threads here, particularly the Gravity - We know what is is. Do we know why it is? Thread, whether it's Gravitons and more Quantum Theory-esque, or just Space Curving (That was Natendo's view I believe) under the "pressure" of objects of Giant Mass.

    I'm not sure what to believe without getting Nitty Gritty and really studying them for myself XD One step at a time I tell myself, hehe.
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    Quote Originally Posted by Cold Fusion
    I read that if you were to get pulled into a black hole and hit the event horizon, you would gain an infinite amount of density, therefore be everywhere in the universe at the same time, making you travel infinitely faster than light. This would although, only cause time dilation, so that you would see the universe die in a second-with everything completely blue shifted to its deepest tone.
    This is nonsense. Depending on the mass of the BH you will experience almost nothing when you pass the event horizon. But after a while, you will be torn apart because the gravity is pulling stronger at the parts that are closer to the BH centre.

    It is the confusing thing about General Relativity that all observed phenomena have to be put in relation to a reference system. This is why somebody watching you falling into the BH will never actually see you passing the event horizon, because your personal clock decelerates with regard to an external observer the more you approach it until it finally stops completely.
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    Quote Originally Posted by ajg624
    c is the constant. i am curious to know, hypothetically speaking, if we observed light traveling at us from two objects in space, a star in the western sky and another in the eastern sky, both at equal distance from our point of reference on earth. would the gap in distance between the two stars close at a rate exceeding c? (2 x c) ?
    No. Independent of the (relative) velocity of the source, the velocity of the emitted light is always the same. This is probably the most confusing result of Relativity. The speed of light is a universal constant, independent of reference frames. The very result of this oddity is that time cannot be constant.
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    Don't forget that as you speed up, time (for you) slows down, which translates into time 'stopping' if you reach 'c' (speed of light). IF that is not strange enough, inside a black hole time may be ruptured or stretched, which creates even stranger scenarios.

    We know of no other particle/wave that travels as fast (or faster) than light. Our mathematics cannot compute anything faster, our understanding of the universe and physics says the same. At speeds in excess of C, things 'don't make sense' as we know, so when you ask if it is possible, as far as we know now, it is not.

    Having said all that, if we can shorten space (fold it, for example) then we can indirectly go faster. Think about that for a while!
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    Unfortunately as stated earlier mass increases as speed increases. If an object attains the speed of light it would have infinite mass (not possible unfortunately). However, many theories observe space to be manipulated by mass, this is why gravity pulls other masses towards it. It creates a 'dip' for want of better terminology in space. Think of it as a sheet of suspended cloth with a ball in the middle. Anything then put on the cloth with fall towards that ball. The greater the balls mass the faster the object will fall towards it as there is a bigger angle created.

    Now imagine a lead weight (or something much heavier) on this cloth which could be held loosely, it would stretch the cloth down so far that two points on the cloth that were originally not very close to each other have been moved closer together. This would be very similar to folding space as CShark said and effectively bypassing velocity altogether although to do it you would need a super-heavy object of incalculable proportions, dare I say, infinite like a mass traveling at the speed of light?

    Criticism as usual is welcomed.
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    Also, the theory of relativity means that while you are going near the speed of light, the planet you left is going away from you near the speed of light. Which would make it seem as though the people on the planet you left were aging slower than you. In order for a spaceship to go the speed of light, not only the ship but EVERYTHING in the universe would need infinite mass.
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    There seems to be some confusion here. One must remember that according to special relativity, all motion is relative. If a spaceship is travelling at close to the speed of light, it must be doing so relative to some observer. In that observer’s frame of reference, it will be as if the mass of the spaceship is approaching infinity. However, to the people inside the spaceship, the spaceship is stationary relative to them; hence they will not observe any change in the mass of the spaceship. If anything, the people in the spaceship will claim that it is the first observer’s mass that is approaching, not that of their spaceship – since, to the people in the spaceship, it is the first observer who is moving at close to the speed of light!

    So whose mass is actually approaching infinity? It depends on whose point of view you are referring. To the observer, it is the spaceship whose mass is increasing; to the spaceship, it is the observer’s mass. To claim that the mass of everything in the Universe is approaching infinity makes little or no sense. It would imply either that there is absolute motion (which contradicts the first postulate of special relativity) or that everything in the Universe is moving at close to the speed of light relative to some observer (which at best is just mind-boggling).
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    Sorry for the confusion, your explanation is much better worded!

    I simply meant that as you left a solar system at near the speed of light, all of the object's mass you were leaving would appear to be approaching infinity. Because from your perspective you are stationary and everything else is accelerating toward the speed of light.
    "It's no wonder that truth is stranger than fiction. Fiction has to make sense." - Mark Twain
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  37. #36  
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    Quote Originally Posted by JaneBennet
    or that everything in the Universe is moving at close to the speed of light relative to some observer (which at best is just mind-boggling).
    If you're feeling playful, consider that "everything in the Universe" at least approaches infinite mass... why? Is it moving?

    ***

    Question:

    A pair of space ships, thrusting parallel, mutually observing, gaining mass. Gravitational attraction increase as mass increases, right? So, steer away a hair to compensate... keep turning... Then eventually we have these apparently stationary space ships ('cause they're just observing each other) facing in opposite directions with French kissing thrusters, not getting any further apart. ???

    Or must we Hansel & Gretel observable breadcrumbs for this to "work"?
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  38. #37  
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    Quote Originally Posted by Pong
    A pair of space ships, thrusting parallel, mutually observing, gaining mass. Gravitational attraction increase as mass increases, right?
    No, not this mass. It is just an apparent mass, not real. Here is another post on this:

    http://www.thescienceforum.com/viewt...er=asc&start=3
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  39. #38  
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    Quote Originally Posted by Dishmaster
    No, not this mass. It is just an apparent mass, not real.
    Somehow I knew the accepted answer would be like that. How did I know? Er... enough said. I'll try to follow where you lead...
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  40. #39  
    Forum Masters Degree SuperNatendo's Avatar
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    Quote Originally Posted by Pong
    Quote Originally Posted by JaneBennet
    or that everything in the Universe is moving at close to the speed of light relative to some observer (which at best is just mind-boggling).
    If you're feeling playful, consider that "everything in the Universe" at least approaches infinite mass... why? Is it moving?

    ***

    Question:

    A pair of space ships, thrusting parallel, mutually observing, gaining mass. Gravitational attraction increase as mass increases, right? So, steer away a hair to compensate... keep turning... Then eventually we have these apparently stationary space ships ('cause they're just observing each other) facing in opposite directions with French kissing thrusters, not getting any further apart. ???

    Or must we Hansel & Gretel observable breadcrumbs for this to "work"?
    If they are thrusting parallel, in the same direction, relatively they are going the same relative speed. Now, is the earth stationary and they are moving at near the speed of light, or are they stationary and the earth is moving away at near the speed of light? You can argue it both ways. Your "speed" really cannot be measured unless you are measuring from a third object that is going at a different speed from the other two, and even then this measurement of your speed is also relative. Light is not like this though. People perceive light going the same speed no matter how fast they are going. For this phenomenon to be able to occur it must mean that your speed affects your perception of time, allowing for the light to always be traveling 299 792 458 m / s, no matter how fast you are going.

    This is where special relativity comes in, since their perceived speed and space-time are different than each others. the people on earth witness a distant supernova happening in a different frame of space-time than the people on the ship witness the same supernova.
    "It's no wonder that truth is stranger than fiction. Fiction has to make sense." - Mark Twain
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  41. #40 Time doesn't stop 
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    Just to clarify Time Dilation:
    Definitions:
    c = speed of light
    v = speed of rocket as measured on Earth
    t-Earth = time interval between clicks as measured on Earth
    t-rocket = time interval as measured on board the rocket
    t-rocket = t-Earth √[1 - (v/c)2]
    The square root factor is less than 1, so t-rocket (any time interval on the rocket) must be less than t-Earth (the corresponding interval on Earth).
    The effect is enormous for speeds approaching that of light. For example, if you travel at 99% the speed of light, then 1 - (0.99)2 = 0.02, the square root of this is 0.14, so your t-rocket would be only 14% of t-Earth. So if a space traveler left Earth at 99% the speed of light and returned 100 years later as measured on Earth, she would be only 14 years older by her biological clock.
    However, at v=c, the equation simplifies to
    t-rocket = t-Earth * 0
    So any amount of time on Earth, even an infinite number of years, could pass before a second passed on the rocket because it gets zeroed out. This doesn’t mean that time would stop on the rocket. If two seconds passed on the rocket, then two infinities would not pass on Earth, because this makes no sense. An observer on the rocket would see all the stars in the universe burn out and their protons turn to radiation in that first second at the speed of light, and then time on board would continue to pass.
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  42. #41  
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    Quote Originally Posted by SuperNatendo
    people on earth witness a distant supernova happening in a different frame of space-time than the people on the ship witness the same supernova.
    This is why I set the two spaceships as a kind of hourglass, intimate & inextricable. Their clocks run on mutual gravity. Now I'm confused. The ships' "apparent mass" & speed increase, but gravity between them does not. This is true for those aboard the ships? Is it true for those on Earth who watch the two points go and come back?

    I'm sure the problem has been well covered since orbiting bodies are pretty common.

    How would these light/time-bending stunts appear on gravity radar? Which is correct?
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  43. #42  
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    I don't know if I am right here or not, but this is my theory:

    Since gravity is the result of the bending of time-space, and your speed changes your perception of space-time, it also changes the rate at which you perceive the curved space-time affecting matter and energy. Therefore, your relativity makes it so that it appears larger bodies of mass have less of an effect on gravity than they used to.

    This would make your "gravity clock" an unreliable source.
    "It's no wonder that truth is stranger than fiction. Fiction has to make sense." - Mark Twain
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