Guest Posted October 20, 2008 Report Share Posted October 20, 2008 you are in a spacecraft moving at the velocity of light. u hold a mirror in your hand. will u be ever be able 2 see ur image? Quote Link to comment Share on other sites More sharing options...
0 Guest Posted October 20, 2008 Report Share Posted October 20, 2008 I'm gonna say yes because of the relative velocity between yourself and the mirror Quote Link to comment Share on other sites More sharing options...
0 dms172 Posted October 20, 2008 Report Share Posted October 20, 2008 No, actually you probably couldn't see anything except a blur, or you would be blinded by light entering yours eyes so fast Quote Link to comment Share on other sites More sharing options...
0 bonanova Posted October 20, 2008 Report Share Posted October 20, 2008 appears to travel the same speed to an observer in a gravitational frame, you will see your reflection.cannot travel that fast, the premise is incorrect and any conclusion can be validly reached. Thus, No, you can't see your reflection, and Yes, you can see your reflection. Quote Link to comment Share on other sites More sharing options...
0 Guest Posted October 20, 2008 Report Share Posted October 20, 2008 Yes, if you are facing the aft end of the ship and walk in the oppisite direction the ship is traveling then you would be able to see your reflection with a slight delay. (Technically, everyones reflection in a mirror has a slight delay anyways. This is just longer because you have to walk into the light that is reletivly stationary compared to the ship). If you are facing forward looking in to a mirror in front of you, then no. Quote Link to comment Share on other sites More sharing options...
0 Guest Posted October 20, 2008 Report Share Posted October 20, 2008 By holding the mirror in your hand, you are controlling its speed. If I were to throw a baseball on that spaceship, I wouldn't be throwing at the Speed of Light + 70 mph. By being on the ship, the relative velocity of each object becomes equal. I could walk from one side of the ship to the other because it's not the gross speed having that effect, but rather my relative speed. And thank you, Bonanova, for your excellent point Quote Link to comment Share on other sites More sharing options...
0 Guest Posted October 20, 2008 Report Share Posted October 20, 2008 you are in a spacecraft moving at the velocity of light. u hold a mirror in your hand. will u be ever be able 2 see ur image? The main requirement of vision is Light. You cannot see if it is dark inside the spacecraft You did not say if inside the spacecraft it was dark or had lights on or was getting the sun rays or any other means of light. Quote Link to comment Share on other sites More sharing options...
0 Guest Posted October 20, 2008 Report Share Posted October 20, 2008 I would say... It is not possible to see your reflection. Because, to see your reflection, light rays has to hit your face, go back and hit the mirror and the reflection from the mirror should come to your eyes for you to see the reflection. I don't see a way of managing to get a reflection in a ship moving at speed of light. Quote Link to comment Share on other sites More sharing options...
0 Guest Posted October 20, 2008 Report Share Posted October 20, 2008 Guess the spacecraft is completely shut (this means, no windows) and the light inside the spacecraft is from lamps and stuff... Could you see your reflection? I think yes, because you are stationary relative to the mirror, right? Althought the whole spaceship IS moving at the speed of light. I'm kind of confused on this, but it's interesting. Quote Link to comment Share on other sites More sharing options...
0 Guest Posted October 20, 2008 Report Share Posted October 20, 2008 (edited) Guess the spacecraft is completely shut (this means, no windows) and the light inside the spacecraft is from lamps and stuff... Could you see your reflection? I think yes, because you are stationary relative to the mirror, right? Althought the whole spaceship IS moving at the speed of light. I'm kind of confused on this, but it's interesting. JarZe's answer gives a good clue to a theoretical answer (in spite of bonanova already posting the correct practical answer). If you were, theoretically, in a spaceship moving at the speed of light (or very, very close to it), which was completely sealed to light, how would you know that you were travelling at the speed of light? Imagine you wake up on a train. Without looking out of the window, would you know if you are at a station or not? dms, MindPoison, and encyclopedia, do you want to change your answers? Mumbles, are you suggesting that you could walk sideways but not in the direction of motion? Edited October 20, 2008 by foolonthehill Quote Link to comment Share on other sites More sharing options...
0 Guest Posted October 21, 2008 Report Share Posted October 21, 2008 dms, MindPoison, and encyclopedia, do you want to change your answers? Mumbles, are you suggesting that you could walk sideways but not in the direction of motion? JarZe's answer gives a good clue to a theoretical answer (in spite of bonanova already posting the correct practical answer). If you were, theoretically, in a spaceship moving at the speed of light (or very, very close to it), which was completely sealed to light, how would you know that you were travelling at the speed of light? Imagine you wake up on a train. Without looking out of the window, would you know if you are at a station or not? The problem with that is that the maximum speed of light is absolute (without getting too much into theory of relativity). The "speed of light being reletive to the spacecraft" idea would work if you were talking about sound because the medium throught which sound travels (air) could be isolated and the speed of sound is not limited by physics. That's why pilots traveling at mach 2 can speak into their radios in front of them. However, the medium through which light travels (empty space) cannot be isolated. This is like that question "what would happen if you were driving at the speed of light and you turned on the headlights?" The answer is the light would scatter into a cone shape (like a sonic boom), but unlike a sonic boom, this would happen even if the light was inside the car. Therefore, if you are in a craft moving at the speed of light, all light around you traveling in the same direction would be relativly stationary and you would have to walk into it to see anything. Obviously, there are a lot of other scientific problems with this question but if your looking for an answer to a brain teaser, that's the most easily explainable answer without a Ph.D. Quote Link to comment Share on other sites More sharing options...
0 Guest Posted October 21, 2008 Report Share Posted October 21, 2008 The problem with that is that the maximum speed of light is absolute (without getting too much into theory of relativity). The "speed of light being reletive to the spacecraft" idea would work if you were talking about sound because the medium throught which sound travels (air) could be isolated and the speed of sound is not limited by physics. That's why pilots traveling at mach 2 can speak into their radios in front of them. However, the medium through which light travels (empty space) cannot be isolated. This is like that question "what would happen if you were driving at the speed of light and you turned on the headlights?" The answer is the light would scatter into a cone shape (like a sonic boom), but unlike a sonic boom, this would happen even if the light was inside the car. Therefore, if you are in a craft moving at the speed of light, all light around you traveling in the same direction would be relativly stationary and you would have to walk into it to see anything. You are right that the speed of light is absolute for any individual observer. The question comes down to who the observer is! When looking at the mirror as a passenger on your spaceship, the light, by your own admission, must travel at the (fixed) speed of light to the mirror and back. You should be very careful of comparing the speed of sound and the speed of light. I'm not going into a long discussion of relativity here, but my favourite analogy, is to imagine two men on a train travelling nearly at the speed of light and passing through a station platform. As they pass the platform, one shoots the other with a laser gun. Clearly, when I'm watching from the platform, the laser travels at the speed of light but is only just overtaking the train. Therefore, it takes a while for the man to die. However, how do the men know they are moving? What if it was the platform moving past the train? From their standpoint, they cannot know, so they could as easily be standing on a stationary train! Therefore, when the laser is shot, it must travel at the speed of light and kills almost instantly. Paradox? No, just the relativity of time. Obviously, there are a lot of other scientific problems with this question but if your looking for an answer to a brain teaser, that's the most easily explainable answer without a Ph.D. The crazy Physics of our world makes great brain teasers (to my mind ) and certainly doesn't always need a PhD! Quote Link to comment Share on other sites More sharing options...
0 Guest Posted October 21, 2008 Report Share Posted October 21, 2008 You are right that the speed of light is absolute for any individual observer. The question comes down to who the observer is! When looking at the mirror as a passenger on your spaceship, the light, by your own admission, must travel at the (fixed) speed of light to the mirror and back. You should be very careful of comparing the speed of sound and the speed of light. I'm not going into a long discussion of relativity here, but my favourite analogy, is to imagine two men on a train travelling nearly at the speed of light and passing through a station platform. As they pass the platform, one shoots the other with a laser gun. Clearly, when I'm watching from the platform, the laser travels at the speed of light but is only just overtaking the train. Therefore, it takes a while for the man to die. However, how do the men know they are moving? What if it was the platform moving past the train? From their standpoint, they cannot know, so they could as easily be standing on a stationary train! Therefore, when the laser is shot, it must travel at the speed of light and kills almost instantly. Paradox? No, just the relativity of time. The crazy Physics of our world makes great brain teasers (to my mind ) and certainly doesn't always need a PhD! Fair enough. I was more thinking you were suggesting that the speed of light was relative because it was inside the craft (that's why I compared it to the jet). I had also kind of assumed (probably incorrectly) that the light was coming from outside the craft (maybe from a star or something, I guess it just went with the spacecraft thing) and that the outside light was traveling along side the craft. I guess that's just how the picture formed in my mind. Oh well, you know what they say happens when you assume. Just out of curiosity, is there a correct answer for this brainteaser, or were we just supposed to figure out what we thought? Quote Link to comment Share on other sites More sharing options...
0 Guest Posted October 21, 2008 Report Share Posted October 21, 2008 you are in a spacecraft moving at the velocity of light. u hold a mirror in your hand. will u be ever be able 2 see ur image? yes, ofcorse u cane see u r image because u r inside the space craft Quote Link to comment Share on other sites More sharing options...
0 Guest Posted October 21, 2008 Report Share Posted October 21, 2008 My suggestion about walking on the aircraft was that the speed of the spaceship (once steady at the speed of light) will bring the relative speed of everything to 0 until it starts to move. On the spaceship, when I walk from one side to the other, I'm not traveling at the speed of light in addition to my walking speed, just like we don't calculate our speeds on earth in addition to the speed with which the earth rotates. And obviously, nothing can alter the speed of light--it is what it is, but that doesn't mean because the spaceship is moving at the speed of light that everything on it is moving at that speed. Think about this outside of a mirror. Holding your beliefs to the notion that you couldn't see yourself in the mirror, you could never see anything moving at that speed. If I were to try and look at the cockpit from the back of the plane, and you assume all objects inside were moving at the speed of light, they would all be a blur because they'd be moving too fast for my eyes to process. Quote Link to comment Share on other sites More sharing options...
0 Guest Posted October 21, 2008 Report Share Posted October 21, 2008 My suggestion about walking on the aircraft was that the speed of the spaceship (once steady at the speed of light) will bring the relative speed of everything to 0 until it starts to move. Relative to what? Relative to the outside observer (assuming he could somehow see it) nothing can 'beat' the ship's motion, so you could not, for example, throw a tennis ball from the back of the ship to the front. Relative to you, inside the ship and moving with it, there is no reason why you couldn't throw the ball. As far as you are concerned, your ship could be stationary and everyone else moving instead. On the spaceship, when I walk from one side to the other, I'm not traveling at the speed of light in addition to my walking speed, just like we don't calculate our speeds on earth in addition to the speed with which the earth rotates. We could. It just has little impact because we never get close to the speed of light, so the effect is negligble. (Also, the Earth rotating is not an inertial frame so it is not quite comparable - we can tell that the Earth is moving, unlike in the spaceship) And obviously, nothing can alter the speed of light--it is what it is, but that doesn't mean because the spaceship is moving at the speed of light that everything on it is moving at that speed. Think about this outside of a mirror. Holding your beliefs to the notion that you couldn't see yourself in the mirror, you could never see anything moving at that speed. If I were to try and look at the cockpit from the back of the plane, and you assume all objects inside were moving at the speed of light, they would all be a blur because they'd be moving too fast for my eyes to process. If it's in the spaceship, then from outside the ship everything in the ship is moving at the speed of light, no more, no less. From inside, everything is moving however you would expect it to move. Quote Link to comment Share on other sites More sharing options...
0 Guest Posted October 21, 2008 Report Share Posted October 21, 2008 You can feel the Earth moving? We know from observing objects outside of out atmosphere that we are moving, but while on Earth, you can't "feel" the effects of it moving. And you have proven my point by saying 'from inside, everything is moving however you would expect it to move'. The relative speed of your eyes bouncing off the mirror and coming back to show your face would act the same way whether the ship was traveling at the speed of light or was sitting still. And by "relative speed" I meant relative to each other. That is the whole concept of relative speed--not their gross total speed (which would be the speed of light in this situation) but the speed in relation to each other. Anytime an object on the ship is in motion, its gross speed is whatever velocity it is moving at + the speed of light. If you simply subtract the speed of light from each object's gross speed, you have the speed of each object relative to the other. Quote Link to comment Share on other sites More sharing options...
0 Guest Posted October 21, 2008 Report Share Posted October 21, 2008 And I'm actually very confused why you would reference anything outside the ship because that is completely irrelevant to the OP and serves no assistance in trying to answer the question Quote Link to comment Share on other sites More sharing options...
0 Guest Posted October 21, 2008 Report Share Posted October 21, 2008 (edited) You can feel the Earth moving? We know from observing objects outside of out atmosphere that we are moving, but while on Earth, you can't "feel" the effects of it moving. Just becuase things outside of our atmosphere appear to be moving, that says nothing about our motion, only our relative motion to them. By observation alone, there is nothing wrong with the theory that the Earth is at the centre of the universe - we could construct paths of motion for the stars which would agree. However, we can conduct experiments (eg Foucault's Pendulum) which demonstrate that we are rotating - a very special type of motion which is not comparable to a ship travelling in a straight line. And you have proven my point by saying 'from inside, everything is moving however you would expect it to move'. The relative speed of your eyes bouncing off the mirror and coming back to show your face would act the same way whether the ship was traveling at the speed of light or was sitting still. Yes. I never disgreed that the ship occupants could use the mirrors as normal. My question to you was regarding side-to-side motion against fore-and-aft motion. My apologies if I misunderstood, but I felt that your response suggested that you could move in one direction but not the other. My answer is that, in the spaceship, there can be no differece for the occupants, because they don't know (ie they can never conduct an experiment that proves) whether they are moving. And by "relative speed" I meant relative to each other. That is the whole concept of relative speed--not their gross total speed (which would be the speed of light in this situation) but the speed in relation to each other. Anytime an object on the ship is in motion, its gross speed is whatever velocity it is moving at + the speed of light. If you simply subtract the speed of light from each object's gross speed, you have the speed of each object relative to the other. There is no such thing except relative speed. One can only measure a speed compared to something else, so your notion of 'gross speed' is misleading: Space has no frame of reference. Anyway, I think that's enough Special Relativity for today and my apologies for letting it get away from the topic (as you pointed out ). My answer to the OP (modified to consider a speed very close to c, rather than at c) is: Yes, you would see your reflection no matter how you moved inside your ship. However, an observer watching you from outside your ship (ie someone who sees you moving past them at that speed), would see you seeing your reflection very, very slowly (tending towards never as you approach the speed of light!). Edited October 21, 2008 by foolonthehill Quote Link to comment Share on other sites More sharing options...
0 Guest Posted October 21, 2008 Report Share Posted October 21, 2008 If the mirror is in the ship with you, then i would guess a yes. But what if the mirror was outside the ship and moving at the same speed the ship was? Would that depend on the distance between you and the image? Quote Link to comment Share on other sites More sharing options...
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you are in a spacecraft moving at the velocity of light. u hold a mirror in your hand. will u be ever be able 2 see ur image?
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