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Thread: Special Relativity Theory

  1. #1 Special Relativity Theory 
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    Hi,

    i'm trying to learn something about this theory, but i wasn't successful in learning so much from browsing.

    Can someone please help me understand it by explaining the principle in simple words?

    thanks in advance,
    darmic


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    Forum Masters Degree SuperNatendo's Avatar
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    Basically, you know how if you threw a ball from a standing position and got it to go a spead of 90 MPH?

    well, if you threw it from the back of a truck going 90MPH, the ball would leave you at 90mph but to someone standing on the earth it just falls down. Throw it from the front, and it is leaving you at 90 MPH, but someone on the side of the road sees the ball going 180 MPH

    This is not how light works!

    Light is constant, no matter what speed the object is traveling when it makes the light;

    Now the implications of this observation are as follows:

    If light is leaving at the same speed no matter what speed the object making the light is traveling, it must mean that the speed you travel and the rate at which you experience time are related.

    The faster you go, the slower you experience time in relation to the rest of us.

    For example, you fire a beam of light from a spaceship while not moving, then, you chase after it as fast as you can. As you go faster, the rate at which time passes for you is different than the rate at which time passes for someone going slower than you, so that the light is constantly speeding away from you at the same rate it is for someone who is not going as fast.

    Say we develope the technology to send a ship to Proxima Centauri and back in approximately 8 years and six months, when we put a clock on the ship or a person, they claim only approximately 4 years and 3 months have passed!

    Knowing this, it is impossible to travel the speed of light, and also, it is impossible to exceed 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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    Forum Radioactive Isotope mitchellmckain's Avatar
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    It is important to understand however that the speed of light is not a barrier. It is more like the structure of space time makes an infinite speed look like it is only the speed of light. So you can take a giant spaceship and accelerate to half the speed of light moving away from the earth, then take a big space ship inside the giant space ship and acclerate to half the speed of light moving away from the giant space ship in the same direction. Then you can take a medium size space ship inside the big space ship and accelerate to half the speed of light moving away from the big space ship, then take a small space ship inside the medium space ship and accelerate to half the speed of light away from the medium space ship, again in the same direction. In this there is no limitation to how fast you can go. Where relativity comes in, is that all of the space ships figure that the earth is receding behind them at a speed less than the speed of light.

    the giant space ship figures that the earth receding at half the speed of light.

    the big space ship figures that the earth receding at 80% of the speed of light.

    the medium space ship figures that the earth receding at 93% of the speed of light.

    the small space ship figures that the earth is receding at 97.6% of the speed of light.

    I use the words "figures that" because this is not actually what they see because to see requires photons which travel at the speed of light and this adds a further distortion in what you see called the "aberration of light". As a result of this aberration you would actually see the earth receding behind you at speeds much slower than this. Appearing to be much closer than it acutally is, which by the way is a lot closer to you than it would be if you suddenly come to stop.

    As for getting to destination, the speed of light is also no limitation because although your destination never appears to be coming toward you faster than the speed of light, while you are moving at a constant velocity, every time you accelerate, your destination zooms toward you as space become squashed in the direction of motion. This is like a real life warp speed, where you travel great distances by "folding space" and making your destination closer to you so that your sub-light speed still gets you to your destination as fast as you would like.

    A very important quantity to understand in SR is gamma, the length contraction factor, which is given by 1/(square root of (1-v^2/c^2)). You can think of gamma-1 as your "warp" speed.

    "warp" 0 or gamma = 1 is for velocity = 0
    "warp" 1 or gamma = 2 is for velocity = 86.6% of the speed of light
    "warp" 2 or gamma = 3 is for velocity = 94.3% of the speed of light
    "warp" 3 or gamma = 4 is for velocity = 96.8% of the speed of light
    "warp" 4 or gamma = 5 is for velocity = 98% of the speed of light
    "warp" 5 or gamma = 6 is for velocity = 98.6% of the speed of light
    "warp" 6 or gamma = 7 is for velocity = 99% of the speed of light
    "warp" 7 or gamma = 8 is for velocity = 99.2% of the speed of light
    "warp" 8 or gamma = 9 is for velocity = 99.38% of the speed of light
    and so on where gamma (and your "warp speed") increases without limit while your velocity gets closer to the speed of light but never reaches it.

    However, as far as getting to your destination is concerned, your effective speed (for high gamma only) is approximately gamma times the speed of light, because the gamma makes the actual distance to your destination shorter by a factor of gamma, so even though you travel close to but less than the speed of light you get to your destination as if you were going gamma times as fast as your actual velocity.

    Anyway what I hope to show you is that all the science fiction movies and books that talk about actually going faster than the speed of light is pure nonsense because you don't need to go faster than the speed of light. Well, he he he, there is one thing I haven't told you and that is that there are two really big price tags on all this. First is that the energy requirement is enormous - basically gamma-1 times your mass energy ((gamma-1) times mass time the speed of light squared) just to accelerate to a velocity corresponding to gamma. Second is that time passes on earth gamma times faster than it does on your space ship so a one year trip in your space ship will mean that gamma years will have passed on earth.

    So for example, let say the nearest star is four light years away and that is your destination. At gamma=8 you can go there and back in only a single year right? Well eight years will have passed on earth. And the trip will have cost of twenty eight times the mass energy of your ship. The second price tag is of course the real problem. That is really an enormous amount of energy.
    See my physics of spaceflight simulator at http://www.relspace.astahost.com

    I now have a blog too: http://astahost.blogspot.com/
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    Forum Masters Degree SuperNatendo's Avatar
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    Quote Originally Posted by mitchellmckain
    It is important to understand however that the speed of light is not a barrier. It is more like the structure of space time makes an infinite speed look like it is only the speed of light. So you can take a giant spaceship and accelerate to half the speed of light moving away from the earth, then take a big space ship inside the giant space ship and acclerate to half the speed of light moving away from the giant space ship in the same direction. Then you can take a medium size space ship inside the big space ship and accelerate to half the speed of light moving away from the big space ship, then take a small space ship inside the medium space ship and accelerate to half the speed of light away from the medium space ship, again in the same direction. In this there is limitation to how fast you can go. Where relativity comes in, is that all of the space ships figure that the earth receding behind them at a speed less than the speed of light.
    No, No, No!

    You don't understand the theory of relativity then!

    The ships launched from the larger ships still have to follow the laws of physics!

    As the ship you launch goes faster, time slows down to make it so that the light is still leaving at the same speed for that ship as it was for the ship it launched from! This means the crew on the big ship, if they saw the crew of the little ship, would see the crew reacting half as slow as they were!

    When you launch at twice the speed of the big ship, time is going by twice as slow! Light is still moving at the same speed from the fastest ship as it is from the slowest, which means that the faster ships are spread out over more space-time! and the time is passing slower for the faster ships than the slower ones!
    "It's no wonder that truth is stranger than fiction. Fiction has to make sense." - Mark Twain
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    Forum Radioactive Isotope mitchellmckain's Avatar
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    Quote Originally Posted by SuperNatendo
    Quote Originally Posted by mitchellmckain
    It is important to understand however that the speed of light is not a barrier. It is more like the structure of space time makes an infinite speed look like it is only the speed of light. So you can take a giant spaceship and accelerate to half the speed of light moving away from the earth, then take a big space ship inside the giant space ship and acclerate to half the speed of light moving away from the giant space ship in the same direction. Then you can take a medium size space ship inside the big space ship and accelerate to half the speed of light moving away from the big space ship, then take a small space ship inside the medium space ship and accelerate to half the speed of light away from the medium space ship, again in the same direction. In this there is limitation to how fast you can go. Where relativity comes in, is that all of the space ships figure that the earth receding behind them at a speed less than the speed of light.
    No, No, No!

    You don't understand the theory of relativity then!
    LOL LOL LOL LOL LOL LOL

    My understanding of SR is not a mere undergraduate acheivement. Even most physics professors do not have the understanding of SR that comes from the personal work on a project to make a detailed computer simulation of how it all works. I assure you that even if this is not what you have heard before, it is 100% absolutely correct. You simply do not see how what you know (or have heard) is actually equivalent to what I have said.



    Quote Originally Posted by SuperNatendo
    The ships launched from the larger ships still have to follow the laws of physics!
    But perhaps what you have not grasped is that velocity is all 100% relative. Even going at half the speed of light relative to the earth, from the point of view of the giant ship, it is not moving at all, it is earth that is moving in the opposite direction, and the physics for the giant ship and all the ships and everyone on it is exactly the same as everywhere else. What is different is ONLY that they measure space and time differently.


    Quote Originally Posted by SuperNatendo
    As the ship you launch goes faster, time slows down to make it so that the light is still leaving at the same speed for that ship as it was for the ship it launched from! This means the crew on the big ship, if they saw the crew of the little ship, would see the crew reacting half as slow as they were!
    Yes but to complete this properly, you should also say that if the crew of the smaller ship saw the crew of bigger ship they would also see the crew of the bigger ship reacting half as slow as they are!!!

    I know that this is what you have been told. And it is correct in a manner of speaking. But talking about what people actually see is made greatly complicated by the aberation of light. What you are talking about are actually the results of calculations and not any actual seeing. It is an interpretation which actually lacks a great deal of clarity. It is really much better to understand things in terms of the relativity of simultaneity rather than this "slowing down of time". For the reality is that whose time has "slowed down" and whose time as actually "sped up" depends on what happens next.

    If the bigger ship were to accelerate and catch up to the speed of the smaller ship they would find out that it is their own time which had "slowed down" and not the time of the smaller ship. But if the smaller ship slows down to the same speed as the bigger ship, then they would find out that it is their own time which had "slowed down" and not the time of the bigger ship. So you see the problem here? All this talk of time slowing down is completely relative.


    Quote Originally Posted by SuperNatendo
    When you launch at twice the speed of the big ship, time is going by twice as slow! Light is still moving at the same speed from the fastest ship as it is from the slowest, which means that the faster ships are spread out over more space-time! and the time is passing slower for the faster ships than the slower ones!
    Careful! This phrase "When you launch at twice the speed of the big ship", does not make any sense. When the smaller ship leaves the bigger ship, the bigger ship is not moving at all. Remember that it is all relative, so you only talk about the speed of the smaller ship relative to the bigger ship, there are no absolute speeds here. So the correct way of saying it is, that the smaller ship accelerates to a speed of half the speed of light relative to the bigger ship.

    Then indeed each of these two ships would make calculations that suggest that the time on the other ship is going half as fast as their own time. But obviously the contradiction between the interpretations of the crews on the two different ships makes the meaning of this rather unclear. Yes you are quite correct that light emmited from the bigger ship would be measured by them as moving at the speed of light relative to the bigger ship and also measured by the crew of the smaller ship as moving at the speed of light relative to the smaller ship. And the reason this works out is because the measures of space and time on the two ships are completely different.
    See my physics of spaceflight simulator at http://www.relspace.astahost.com

    I now have a blog too: http://astahost.blogspot.com/
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  7. #6  
    Forum Masters Degree SuperNatendo's Avatar
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    Okay woah!

    I just re-read your post, I guess I was wrong!

    That just blew my mind though, never thought of it that detailed! Is there a video or picture record of the simulation you helped make? I'd love to see that! It has made me feel really dumb! LOL, especially since it appears everyone else is slowing down too!

    what would happen as you decelerated, or more correctly, what would happen as the two spaceships started matching speed again?
    "It's no wonder that truth is stranger than fiction. Fiction has to make sense." - Mark Twain
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    Forum Radioactive Isotope mitchellmckain's Avatar
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    Quote Originally Posted by SuperNatendo
    Okay woah!

    I just re-read your post, I guess I was wrong!

    That just blew my mind though, never thought of it that detailed! Is there a video or picture record of the simulation you helped make? I'd love to see that!

    But it is all starting to make sense to me know, I'd elaborate more but I need to sleep on it! This has totally rocked my view on SR!

    Need to sleep on this one for sure! get it logged into the memory banks LOL!
    If you look at the bottom of my posts you will see a link to my web page where you can download the simulator. This is a fully interactive simulation and the real difficulty will be learning how to use it. Let me know how it goes.
    See my physics of spaceflight simulator at http://www.relspace.astahost.com

    I now have a blog too: http://astahost.blogspot.com/
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  9. #8  
    Forum Masters Degree SuperNatendo's Avatar
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    what happens as the two ships going different speeds start to match speeds?

    Dude, you are a genius!

    It runs on my pc....slowly LOL!
    "It's no wonder that truth is stranger than fiction. Fiction has to make sense." - Mark Twain
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    Forum Radioactive Isotope mitchellmckain's Avatar
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    Quote Originally Posted by SuperNatendo
    It runs on my pc....slowly LOL!
    What do expect? It has to recreate nearby galactic space 10 times a second. So yeah it needs a good computer with a good video card too. That program will drain my laptop battery in 10 minutes.


    As for open source - my code was not written for public consumption! Yikes!
    See my physics of spaceflight simulator at http://www.relspace.astahost.com

    I now have a blog too: http://astahost.blogspot.com/
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  11. #10  
    Forum Masters Degree SuperNatendo's Avatar
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    After i saw you had programmed it yourself i took that part out, you have a right to expect payment for such an excellent program, it is your intellectual property, you have every right to not open-source it! That is a decision for the author and the author alone!

    I'm going to try it out when I get home, If I try it at work they might think it is a game lol!

    I knew it would be processor-intensive, that's why i originally asked for a video, but I think my home pc will manage it better!
    "It's no wonder that truth is stranger than fiction. Fiction has to make sense." - Mark Twain
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  12. #11  
    Forum Radioactive Isotope mitchellmckain's Avatar
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    Quote Originally Posted by SuperNatendo
    what would happen as you decelerated, or more correctly, what would happen as the two spaceships started matching speed again?


    what happens as the two ships going different speeds start to match speeds?
    I thought I answered that question in my other post. So let me try this to explain the relativity of simultaneity instead.

    Suppose earth built this chain of clocks to the nearest star, so that a space ship traveling to this star could look at these clocks that they are passing on the way to that star. Now what happens when a ship accelerates to gamma=2 or 86.6% of the speed of light, is that the distance to the destination becomes half as long and the clocks in the chain no longer all have the same time on them, but all have different times, each one ahead in the chain being slightly ahead of the one before it. So now if you focus (supposing you did not have to depend on photons to see the clock) on just one clock (or any of the clocks on the earth) you would find that it was going half as fast as the clocks on your ship. HOWEVER if instead of focusing on a single clock, you just read the time on what ever clock you happen to be passing and call this "earth time" then you would find that this "earth time" was actually passing twice as fast as the time on your ship clocks.

    Now what happens when you slow down to a stop relative to the earth is that the distance between the earth and the destination star goes back to its full distance and all clocks change so that they agree with the clock that is currently closest to you (including all the clocks on earth). That way you see that reading time off of whatever clock nearest you really was earth time and it was your ship clocks that were really going half as fast as the clocks on the earth and not the other way around as you first thought.

    PS. There is actually a simulation of this in my program. Look up simultaneity in the help menu.
    See my physics of spaceflight simulator at http://www.relspace.astahost.com

    I now have a blog too: http://astahost.blogspot.com/
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