Dilemma about traveling at the speed of light

weeman · Jan 17, 2007

So there are all kinds of posts on this board that deal with the speed of light, and traveling at or near the speed of light. Lets say for a moment, theoretically, that it was actually possible to travel AT the speed of light in a man made spacecraft. The closer we come to the speed of light, the greater time dilation that is experienced. Even though time seems to tick by at a normal rate on the ship, years and years are passing by on Earth, or elsewhere in the Universe. So what happens when the ship actually reaches the speed of light? Would time actually stop on the ship, or would it still tick by as if nothing changed? Why would time tick normally at any speed slower than the speed of light, yet when C is reached time stops on the ship? Lets say that time on the ship didn't stop at the speed of light. At this point, what amount of time would be passing by outside of the ship? <div class="Discussion_UserSignature"> Techies: We do it in the dark. "Put your hand on a stove for a minute and it seems like an hour. Sit with that special girl for an hour and it seems like a minute. That's relativity." -Albert Einstein </div>

vogon13 · Jan 17, 2007

Thought experiment: You pull a string between here and the Large Magellanic Cloud. (this will take />300,000 years BTW) Make sure the string has a knot every light year. Fly to the LMC at .99C, counting the knots as you go. (with out doing the math, let's say you age 100 years on the flight) You have counted 160,000 knots along the string on the way to the LMC. Recalling that D=RT, and noting that you have traveled 160,000 in 100 years, you are forced to conclude that your trip to the LMC was accomplished at a speed of 1600C. As far as you are concerned, the SOL is no particular proiblem at all. You have, in fact, travelled at 1600C. <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

dragon04 · Jan 17, 2007

So what happens when the ship actually reaches the speed of light? Would time actually stop on the ship, or would it still tick by as if nothing changed? No, time for you passes "normally". However, time is ticking by much much faster for everyone and everything outside your ship. I can't remember who it was (maybe Carl Sagan) who pointed out that at c, you could circumnavigate the known Universe in 52 years' "ship time". Unfortunately, billions of years would have passed on Earth and there wouldn't be a Welcome Back party forthcoming. <div class="Discussion_UserSignature"> "2012.. Year of the Dragon!! Get on the Dragon Wagon!". </div>

weeman · Jan 17, 2007

Who knows, if you travel the Universe long enough, you might eventually reach the end of time. Couldn't this be a possibility? Of course, you might have to live for a long time, and it would have to mean that the material universe is finite <img src="/images/icons/smile.gif" /> I have so many questions on this topic because the dilation of time in relation to a traveler's speed is by far one of the most bizarre things that I can comprehend! <div class="Discussion_UserSignature"> Techies: We do it in the dark. "Put your hand on a stove for a minute and it seems like an hour. Sit with that special girl for an hour and it seems like a minute. That's relativity." -Albert Einstein </div>

dragon04 · Jan 17, 2007

ho knows, if you travel the Universe long enough, you might eventually reach the end of time. In fact, Arthur Dent did just that. And lived to tell about it. <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> "2012.. Year of the Dragon!! Get on the Dragon Wagon!". </div>

MeteorWayne · Jan 17, 2007

How improbable <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

vogon13 · Jan 17, 2007

(In the thought experiment) I personally knotted the string every light year, and have no need to measure it's length during the flight. The string is 160,000 lightyears long, and has 160,000 knots in it. <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

SpeedFreek · Jan 17, 2007

Well according to special relativity, at the speed of light time dilation becomes infinite (also length contraction makes you infinitely small and with infinite energy or mass, but lets ignore this!) which means you reach your destination instantly. So time continues to pass normally for you at the speed of light, but the journey is instantaneous. Instantaneous for you, the ship you are in, and the control systems of the ship you are in. If outside observers could see you, supposedly they would see you frozen in time for the duration you were travelling at light-speed. But if the journey for you is instantaneous, this means your journey takes no time. There is no time for you to think and no time for your computers to process any commands. So how are you going to stop? <div class="Discussion_UserSignature"> _______________________________________________ SpeedFreek </div>

trumptor · Jan 17, 2007

"at the speed of light time dilation becomes infinite " Wouldn't this also mean that if you perceive yourself going at the speed of light for even an instant that time will have progressed infinitely outside? <div class="Discussion_UserSignature"> ______________Caution, I may not know what I'm talking about. </div>

trumptor · Jan 17, 2007

"also length contraction makes you infinitely small and with infinite energy or mass" So as you approach light speed do you become a candidate for the beginning of a new big bang? I'm assuming that you'd need all the energy and matter in the known universe to approach that speed so you don't break the conservation of matter and energy law. <div class="Discussion_UserSignature"> ______________Caution, I may not know what I'm talking about. </div>

trumptor · Jan 17, 2007

I was just pointing out that the "symptoms" of a particle with mass approaching the speed of light resemble the BB theory's beginnings. An unbelievable amount of mass in an incredibly tiny volume is supposedly what the universe started as, correct? And as you approach the speed of light you become incredibly tiny and massive. I do have a serious question here but I'm not sure if I should post a new subject or continue here. If we all came from this singularity then what's to say that if you keep going out in space you won't run into the remnants of another big bang that happened elsewhere? What if on a much larger scale, one that would make our known universe look like a speck of sand compared to our earth there were countless big bangs which had their own expanding galaxies and stars that in certain places may even cross paths with ours? Could these "universes" seem as numerous as stars in our galaxy to an observer looking from somewhere way out there? Why would this not be possible? <div class="Discussion_UserSignature"> ______________Caution, I may not know what I'm talking about. </div>

SpeedFreek · Jan 17, 2007

Wouldn't this also mean that if you perceive yourself going at the speed of light for even an instant that time will have progressed infinitely outside? Well, I suppose "approaches infinity" would have been a better way for me to put it. The amount that time progresses to observers "outside" is a product of the distance you would have travelled at the speed of light, to those observers. <img src="/images/icons/smile.gif" /> But as there is no way for you to stop yourself once you reach the speed of light, you may well travel forever, and thus infinite time may pass "outside". And the problems with it are, as others have said, that you need infinite energy to do this, so it is impossible. Thus any questions about becoming a new big bang are moot. Also, according to theory, even the big-bang didn't contain infinite energy or mass. So accelerating any mass to the speed of light is less likely than the big-bang! A gravitional singularity has zero volume and thus infinite density. Mass and density aren't the same. Any amount of mass compressed into zero volume would have infinite density. <div class="Discussion_UserSignature"> _______________________________________________ SpeedFreek </div>

lukman · Jan 18, 2007

According to some smart scientist, at light of speed, you will become light itself, at FTL, you will be teleported either to other dimension, or other point in the universe as you stop the FTL speed, since you will be out of sight (invisible) at FTL. Just like dark matter <div class="Discussion_UserSignature"> </div>

weeman · Jan 19, 2007

Lukman, with FTL are you basically talking about warp speed? Can warp speed be classified as the 5th dimension? When you reach C, if you become light itself, how would it ever be possible for anything to be thrusted to a speed that is greater than C? <div class="Discussion_UserSignature"> Techies: We do it in the dark. "Put your hand on a stove for a minute and it seems like an hour. Sit with that special girl for an hour and it seems like a minute. That's relativity." -Albert Einstein </div>

SpeedFreek · Jan 19, 2007

That's all very well, but this thread was specifically about traveling at the speed of light. This what my post was addressing, so I am trying to understand why replied to my post commenting about "smart scientists" theorising about FTL travel and other dimensions. <img src="/images/icons/smile.gif" /> As for becoming light itself at lightspeed, well other things travel at the speed of light (radio waves for instance). But radio waves do not become light itself - they exist in a different part of the electromagnetic spectrum from light. The problem is that you cannot accelerate anything with mass to lightspeed. Light has no mass so light can travel at c. Nothing with mass can travel at c, therefore nothing with mass can ever become light itself by travelling at c. <div class="Discussion_UserSignature"> _______________________________________________ SpeedFreek </div>

lukman · Jan 19, 2007

Forget about become light itself stuff, i dont mean it that way. Warp speed is not FTL, warp is warping space, like a worm hole, highway or stuff like that. What i mean is, if you somehow can travel at FTL speed, you will become invisible because you have will warp the time, while warp in startrek is warping space. because warping space is possible in theory, FTL is not, at least for now, may be there are FTL speed, but since it cant be observed, so we cant prove it. <div class="Discussion_UserSignature"> </div>

mako71 · Jan 19, 2007

<blockquote>In reply to:<hr /> lukman: because warping space is possible in theory, FTL is not, at least for now, may be there are FTL speed, but since it cant be observed, so we cant prove it. <hr /></blockquote> I had some difficultiess to follow your posting about "warping being not FTL", but I'd like to say, that something that is theoretically possible is not necessarily ever buildable. Newtons mechanics doesn't give us any speed limits (while still being usable), it's all the fault of Einstein & co :-( I found this very useful explanation, why FTL in any form breaks causality (if relativity theory is holding true): http://www.theculture.org/rich/sharpblue/archives/000089.html <div class="Discussion_UserSignature"> ________________ reaaliaika.net </div>

alkalin · Jan 19, 2007

There was a failure of the MM (Michelson/Morley) experiment that Dr E resolved that has been reinvented in different ways ever since. There is the velocity of c measured on any bench anywhere and even if traveling at velocity relative to us, to someone doing the measurement on their bench they will measure exactly c for the velocity of light. This is relativity but how can this be? Some distort the picture of our understanding of time to describe what is going on. But here is the way I see it: A photon of light can be described in terms of waves. The waves have certain frequency and are very much influenced by local matter as in the test bench. To put it as simple as I know how, the waves are engaged with other matter like a process of meshed gears (the test bench) and are influenced to produce a certain speed of the photon. But remember also that matter is made up of many frequencies and sub frequencies that can also produce the effect of discreet intervals or quanta. There are known other influences as well such as a person full of matter waves that can influence the experiment about light as well. Photons may travel at c, below c or above c in the universe, but this cannot be measured. So why make the assumption that c is the same everywhere when there are devices that prove otherwise such as laser gyros? The problem as I see it is that current physics relativity is hooked to matter in the Newtonian sense that time dilation means slowing of matter time that is in fast transit. I disagree completely on this. We in our reference frame see an object going close to the speed of light. We think we see a time dilation on board some fictional fast ship, but it is not about the matter on board that other ship, it is about the delay in signal that tells us about the ship as it was in the past. If the ship becomes FTL, then we would not see it any longer, but what happens on board seems perfectly normal and time has not stopped

lukman · Jan 19, 2007

True, FTL will break causality, but warp speed is not FTL, something like teleporting through worm whole, very much science fiction at the moment, but theoritically possible. Warping space is a way to get rid of the space between point A to B, so they become closer. no relativity theory is broken. Talking about causality, if i can recall it right, Einstein once said, the faster you move, the slower your time will tick, and if we can travel at light speed, our time will stop, then FTL will cause negative time, which make us travel back to past. For many good reasons, FTL will never be achieved, even if FTL is possible, God will not allow it to happened. http://www.orionsarm.com/intro/ftl-paradoxes.html <div class="Discussion_UserSignature"> </div>

mako71 · Jan 19, 2007

<blockquote>In reply to:<hr /> lukman: True, FTL will break causality, but warp speed is not FTL... <hr /></blockquote> Sorry that I don't understand, but if the ship with warp drive doesn't move FTL, what use it is for? Isn't then the same to use some more traditional methods to travel in space? Does this warp drive be more "fuel efficient" or what? <blockquote>In reply to:<hr /> lukman: (warp drive is) something like teleporting through worm whole, very much science fiction at the moment, but theoritically possible. <hr /></blockquote> I have a feeling that someone has said, that these theoretic worm holes allow time travels. So, yes, if time travels are possible, then why not FTL... I'll repeat my self saying, that Newton's mechanics doesn't set us any speed limits, so theoretic possiblities are not always possible in practice. Do you mean so called "Alcubierre drive" with this warp drive? http://en.wikipedia.org/wiki/Alcubierre_drive <div class="Discussion_UserSignature"> ________________ reaaliaika.net </div>

weeman · Jan 20, 2007

The Alcubierre Drive most certainly warps the space around it so that a ship may travel vast distances in a very short time. From what I understand in the Wikipedia article the Alcubierre drive does not require FTL to reach warp speed and travel through space almost instantaneously. Although it would appear that the ship traveled faster than light to reach its destination. Light leaves the Sun 93 million miles away, it takes about 8 minutes for it to arrive at Earth. Lets say I hop in my ship that has a brand new shiny Alcubierre drive in it (and a hemi <img src="/images/icons/laugh.gif" /> ), I blast towards Earth and arrive in about 4 minutes. Does this mean I went faster than light? Of course not, it just means I made the path shorter, in a sense, my ship is capable of making its own shortcut. If I am racing my friend on foot, and we both run at the exact same speed, what will my friend think if I arrive before him? He might think that I ran much faster than him, but in all reallity, I found a shorter path to reach our destination. Alkalin, I'm quite following you on your disagreement with time dilation. How do you explain the age difference between someone here on Earth, and someone who has traveled the Universe at high speeds? This is one thing that Einstein had elaborated on. Lets say I have decided to take a trip through space to search for another habitable planet. I say goodbye to my friend (who is the exact same age as me), and blast off in my ship. As I am traveling at very high velocities through space, the time dilation will cause me to age slower than my friend. So how would you explain it if I appear to have hardly aged a day, and my friend might appear to be an older man in his 60's or 70's? <div class="Discussion_UserSignature"> Techies: We do it in the dark. "Put your hand on a stove for a minute and it seems like an hour. Sit with that special girl for an hour and it seems like a minute. That's relativity." -Albert Einstein </div>

mako71 · Jan 20, 2007

<blockquote>In reply to:<hr /> weeman: Light leaves the Sun 93 million miles away, it takes about 8 minutes for it to arrive at Earth. Lets say I hop in my ship that has a brand new shiny Alcubierre drive in it (and a hemi), I blast towards Earth and arrive in about 4 minutes. Does this mean I went faster than light? Of course not, it just means I made the path shorter, in a sense, my ship is capable of making its own shortcut. <hr /></blockquote> Yes, true, but as far as I can see this would cause the time travel paradox of information, since mass = energy = information (right?) and there's no absolute "now" moment (relativity of simultaneity)... It would look really strange this kind of ship travelling towards you (if it is visible), since when coming faster than light in regular path, you would first see it near to you (when it's stopped). After that, you would see a "shadow" of it travelling backwards, when the light reflections from its more distant positions would reach you...

<div class="Discussion_UserSignature"> ________________ reaaliaika.net </div>

alkalin · Jan 20, 2007

Alkalin, I'm quite following you on your disagreement with time dilation. How do you explain the age difference between someone here on Earth, and someone who has traveled the Universe at high speeds? This is one thing that Einstein had elaborated on. Lets say I have decided to take a trip through space to search for another habitable planet. I say goodbye to my friend (who is the exact same age as me), and blast off in my ship. As I am traveling at very high velocities through space, the time dilation will cause me to age slower than my friend. So how would you explain it if I appear to have hardly aged a day, and my friend might appear to be an older man in his 60's or 70's? This is one of the problems if you assume c has a constant value everywhere, so what you have to do is manipulate the process of time to compensate. There is the possibility of looking at this entirely differently. If c is not a constant but varies per its nearness to other matter that is in motion, then different math applies. This assumption will give a very different picture of what happens when lets say a FTL ship has been heading toward you. The light from the ship leaves the ship in all directions relative to the ships reference frame, so light traveling toward your position from the ship is going FTL + c and therefore you will see the ship coming toward you. Now due to your own reference frame, the effect of frequency in your local matter waves will slow the light to your reference to the value of c. I see this as non-Doppler so frequency of light does not change, only its velocity. This notion allows FTL travel and certain levels of communication with signal as well. There is no need for exotic and nonsensical time manipulations to create wormholes which cannot exist, if we abandon defective math notions. But what do I know. As I see it, the questions you raise require thinking outsid

alkalin · Jan 21, 2007

You raise some important issues that might be involved if c were a variable in our reference frame and we are discussing some matter that is near light speed that produced the photons. I have indicated in previous remarks that c is a constant in our own reference frame which is our test bench, the only place c can be measured. Otherwise the value of c has to be inferred. Most matter in the universe is nowhere near traveling at light speed, so we will not actually see much effect from other sources when their reference frame is in motion relative to us. So the holy grail of c in vacuum everywhere would not be budged enough to measure perhaps. But bringing up the Fine Structure Constant could point to a clue of why photons engage in wave interaction with other matter and therefore have value c. The problem is what happens when something is actually traveling near light speed or even FTL that emits radiation? These things we seem only able to speculate about, yet they are just as interesting to me as anything going on in physics and cosmology.

control_group · Feb 2, 2007

Hasn't the time dilation effect been experimentally measured? IIRC, it made use of two clocks accurate and synced to billionths of a second, with one put aboard a plane and one kept stationary (relative to a given location on Earth, of course). The plane flew around for a bit, and when it landed, the clocks were out of sync by pretty much exactly the amount predicted by GR, given the relative velocities of the two clocks. I don't have a link handy, unfortunately - can someone confirm/deny?

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