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Trying to understand the Why or Relativity.

  1. Nov 8, 2009 #1
    Trying to understand the "Why" or Relativity.

    The thing I don’t like about Einstein’s theory is that he doesn’t really explain why it’s correct, just that it is correct, and he proves it mathematically, and with a few thought experiments and actual experiments. At first I always thought that it was just so complex that I didn’t fully understand it, or that nobody had really explained it to me well enough for it to make sense conceptually. The more I think about it though I’ve decided that I actually do understand it, but the theory it self just isn’t complete.

    Not that I think the theory is entirely wrong. Obviously the math and the various experiments do seem to support what Einstein is saying, but the problem I’ve always had is why would simply going fast cause time to slow down. More over why does the speed of light seems to be the point where time stops completely.

    I believe the answer must be that the mechanism that causes time to pass is moving at the speed of light, and the closer an object is to traveling at that speed, the less frequently the mechanism can move time forward. So the question is then – what makes up a part of every single object in the universe, and moves around at the speed of light? The answer seems pretty simple to me….Electrons.

    Before I get to far ahead of myself here’s the thought experiment that gets me here. Imagine a man in a golf cart sitting parked in a fairway. Then imagine another guy in a golf cart driving in circles round him. A golf cart has a fixed speed because of it’s governor. Lets just say that’s set at 10 mph. So as long as the first golf cart stays parked, there is a fixed time it would take the second golf cart to make one loop around it. Lets say 4 seconds. Two seconds to move from the front of the cart to the back, and two seconds from the back of the cart to the front.

    Now imagine what would happen though if the first golf cart started moving forward down the fairway. Lets say at 5 mph to start. Half the speed of the second cart. The second golf cart could continue to make loops around the first cart, but it would be more difficult and take more time. It would now take 4 seconds just to move from the back of the cart to the front, and only one second to move from the front to the back. A net gain of 1 second for a total of 5.

    The closer the first cart got to maxing out it’s governor the more dramatic the slow down would be. If the first cart was moving at 8 mph it would take 5 times longer to go from the back to the front, and 1/5 th as long to go from the front to the back, so 10 seconds to move from back to front, and 1/4th of a second to move from front to back.

    Then once the first cart hit it’s max of 10 mph the second cart would no longer be able to make a loop. It would have to stay in one position relative to the first cart in order to just keep up with it. The second cart could not change it’s position relative to the first cart without losing ground to the first cart.

    The same is true with the position of an electron relative to that of an atom. When the nucleus of an atom is not in motion the electron has no problem zipping around it at the speed of light, but as the nucleus of the atom accelerates towards the speed of light the frequency for which the electron could change it’s position relative to the nucleus would gradually be lessened.

    Once the nucleus reaches the speed of light, the electron would have to maintain the exact same position relative to the nucleus of the atom in order to stay apart of the atom as a hole. Since the state of the atom would then not be changing relative to itself, time stops for that atom.

    When you really think about it, time is really just the acknowledgment that things have changed. If nothing is changing time isn’t passing. That doesn’t mean that if you just stand still time won’t pass for you, because even if you don’t move your arms or legs, you’re still breathing, your heart is pumping, and the electrons that make up every atom of your body are still zipping around at the speed of light inside of you.

    In order to make time stop for an object, you must prevent the state of the object from changing in anyway relative to itself. The only way to do that is to speed the object up to the speed of light. Making every particle that makes up the structure of the object move in exact unison prevents it’s overall state from changing and therefore stops time from passing for that object.

    If this is correct, it would not effect any of Einstein’s calculations drastically at all. All the mathematics would be the same, the only difference might be that instead of time going backwards upon exceeding the speed of light, it would imply that an object would simply break apart and lose it’s cohesion upon exceeding the speed of light.

    This may even lend a possible explanation of why there is a difference between special relativity and general relativity since one is dealing with the motion of sub-atomic particles, and it is the motion of the particles themselves that are the basis for it all. I haven’t really thought to much about that though.

    Even if I’m wrong about electrons being the cause of time dilation, I think I do have the right idea, maybe just the wrong particle, or perhaps there’s an even smaller particle out there that also moves at the speed of light that we don’t know about.

    I’m no physics major though this is simply what I extrapolated from what I do understand. If someone could explain to me why I’m wrong about this, please do.
  2. jcsd
  3. Nov 8, 2009 #2


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    Re: Trying to understand the "Why" or Relativity.

    Personal theories are forbidden by PF rules.

    However, if you don't understand SR, please feel free to ask questions. We will try our best to help you understand it.

    The first thing to read up on is the concept that space and time are not separate. It is 4-dimensional space-time. This is why movement through space is inextricably linked to movement through time.
  4. Nov 8, 2009 #3
    Re: Trying to understand the "Why" or Relativity.

    Well my question is "why does going fast make time stop?" I understand that it does. I'm not denying that. The math, and experiments I've seen all seem to point to that, but why would simply increasing your speed slow down time for you?
  5. Nov 8, 2009 #4


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    Re: Trying to understand the "Why" or Relativity.

    I edited my post above.
  6. Nov 8, 2009 #5
    Re: Trying to understand the "Why" or Relativity.

    Which I have, and for the most part that makes sense. To me though the confusion comes in when people start talking about time like it's thing that exists rather than a description. As I understand it, every point in space has a 4 dimensional coordinate, it has an X,Y, and Z axis, and it also has a Time coordinate. (that might be an oversimplification, but...)

    It seems like what relativity is saying is that the pace at which an object moves from coordinate x,y,z to coordinate, x1,y1,z1, causes the time coordinate to change differently vs if it were sitting in motion.

    To me "Time" is like "Speed." You can't slow down speed, you can change the speed of an object, but you can't change speed it self. In the same token, you can change the rate for which time passes for an object, but you can't slow down time it self. So the question is what is it about speed the makes and objects time pass slowly? That seems to be something that is proven to happen, but no body has really explained why it happens yet.
  7. Nov 8, 2009 #6


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    Re: Trying to understand the "Why" or Relativity.

    If I drive West at 60mph, I'll make 60mph headway westward.
    If I drive northwest at 60mph, I will only make headway westward at about 42mph.
    The more northerly I head, the slower progress I make in the westerly dimension.
    Heading due North, my progress in the westerly direction stops.
    The West dimension and the North dimension are inextricably linked.

    A similar thing happens in 4D space time. Heading in a space direction at a significant speed affects the rate at which I "proceed" in the time direction.
  8. Nov 8, 2009 #7
    Re: Trying to understand the "Why" or Relativity.

    That's what I was looking for. Thank you.
  9. Nov 8, 2009 #8
    Re: Trying to understand the "Why" or Relativity.

    I think I am struggling with the same concept but I refuse to give up.

    I am guessing this has to do with the physical limits. c being the fastest anything can travel must (to me anyway) imply that there is a point where time has to stop.

    If that's the case than there is not reasonable why answer. At least I don't think one has been discovered yet.

    I think I just got to take the postulates of SR and somehow model them so it all works out right. I commend Einstein, I am super visual person I can't imagine how he thought out the basic implications.

    I just wish I could visualize time and space.

    To me time and space have to be connected somehow. Stationary objects move only through time. Time doesn't stop when you stop moving through space, that make sense ( guess that's relative, how do you know something is in motion without reference to something else). I assume that an object a can move through most space and not time....such as a photon, photons from what I gather are not affected by time.

    Speed is defined by movement in space/time.


    Is it because an object can't travel in spatial direction more so than time? like an object is bound to the space and time dimensions?

    ...I am probably totally lost here...

    Where is Einstein...I need him.


    Dave you are the man...if you were faster I could of saved myself the embarrassment.
  10. Nov 8, 2009 #9


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    Re: Trying to understand the "Why" or Relativity.

    I am very pleased to have been able to help.

    But note that my analogy with driving is a loose one. Don't take it too literally.
  11. Nov 9, 2009 #10
    Re: Trying to understand the "Why" or Relativity.

    Alright so initially I thought that answered my question, but after thinking about that for a little bit I don't think it really did.

    Based on your analogy if I drive straight west it means my rate of travel to the north is always 0. It doesn't matter how fast I move west or how slow I move west, as long as I'm only moving west I can't by definition be moving north also.

    It doesn't matter which direction you move in though time passes at the same rate. You can only change that by traveling faster or slower in that direction.

    To put it another way we say that time and space are linked, but do we actually know what links them? It just seems to me like we're saying that if you assume time is the 4th dimension, then all these calculations work out the way they should, and all these experiments turn out the way we expect them. I agree with that, but what is the mechanism that forces time to connect to space.

    It seems like time should be able to pass just as fast at 0 mph, 60 mph or the speed of light. We can mathematically show it doesn't, and we have experiments to show it doesn't. That just doesn't mean it can't though, just that it's never happened.
  12. Nov 9, 2009 #11


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    Re: Trying to understand the "Why" or Relativity.

    That's why it's a loose analogy. You can't carry it very far.

    Simply put: there are three spatial dimensions and one time dimension in the 4-dimensional spacetime that makes up our universe.

    Asking how they are "forced to connect" is like asking how length and width are forced to connect. They are simply different facets of the same thing.

    It may be a bit optimistic to hope for a satisfactory answer at this level of understanding. We're just skimming the surface here. Grab a book.
  13. Nov 9, 2009 #12
    Re: Trying to understand the "Why" or Relativity.

    "The thing I don’t like about Einstein’s theory is that he doesn’t really explain why it’s correct..."

    Einstein doesn't know either. He had several (at least) different formulations and it was the equivalence principle (between acceleration and gravity) that gave him sufficient insights to pick a mathematical formulation that he thought would be proven experimentally.

    Asking why a particular theory is correct is too much for physics to usually answer: if we can conceive a theory and make predictions which are confirmed experimentally, usually that's the best we can do. Nobody knows WHY space and time mix the way they do...after all nobody knows what either space nor time is....our lack of knowledge is daunting and now inlcudes dark mass and dark energy about which which have only the barest glimpse...so we recently found about 96% of of universe is "unknown"....
  14. Nov 9, 2009 #13
    Re: Trying to understand the "Why" or Relativity.

    Although General Relativity is slightly more complicated, many of the effects you mention are due to Special Relativity. Special relativity rests on two fundamental assumptions. All the other "weird" stuff like time dilation follows from these two simple postulates.

    1. Uniform motion is relative. There is no "absolute frame of reference" where the laws of nature are only correct if measured from that frame. According to this assumption, the laws of nature don't change if I get in my car and start driving at 50mph down the highway. If I have two rocket ships in space passing each other without either accelerating, then there is no experiment they can do to tell who is "really" moving and who is "really" at rest. The best they can do is talk about their speed relative to each other. This assumption is really nothing new in physics, Newton mentions it too.

    2. There is a finite speed of causality. Cause and effect take time. There is no such thing as instantaneous action at a distance. This is often stated as "the speed of light is the same to all observers" This is because it just so happens that the speed of light in a vacuum is this speed of causality. The maximum speed of causality must be the same to all observers via postulate 1. This postulate was all Einstein and allowed him to not only explain some experimental results, but make some startling predictions as well.
  15. Nov 9, 2009 #14
    Re: Trying to understand the "Why" or Relativity.

    Alright thanks to everyone who replied. I think I found what I was looking for. Basically I believed I understood Einstein's theory, but it seemed like he was making a jump in assuming time as the 4th dimension.
    I wasn't sure if this was because I was reading it wrong, or not. That's all I needed to know and it sounds like I was right. Thanks!
  16. Nov 9, 2009 #15


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    Re: Trying to understand the "Why" or Relativity.

    One thing to keep in mind is the motto "the proof is in the pudding".

    Einstein doesn't know "why" any of this is the way it is either. He made some assumptions and then tried to work out the implications. Turns out the implications match our observations excuisitely accurately in experiment after experiment. SR is one of the most well-tested theories in all of science.

    Why it is, we don't yet know. But we're pretty sure what it is.
  17. Nov 9, 2009 #16


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    Re: Trying to understand the "Why" or Relativity.

    I'm going to change up Dave's North-West analogy to bring it a little closer into line with Relativity. I'm going to do this by placing "West" with "forward" and "North" with "left or right".

    I am driving forward at 60 mph. If "forward" is the direction of time, then this is the same as saying that I am at rest. (since Left would be the direction of space.) From my perspective, I am always driving forward. (No matter which way I turn, I am always facing the direction I am traveling.) This is the same as saying that I can always claim to be "at rest", and also removes any notion of an absolute frame.

    Another person in also driving at 60 mph but at a 45° angle to my left. To my perspective, he is traveling at about 42 mph forward and 42 mph left. (As I travel forward through time, his distance from me to the left increases. He is moving through space.

    Note that from my perspective, he is traveling slower in my forward direction than I am. If forward is time, he is progressing through time slower than I am and is aging slower.

    Also note that from his perspective, I am traveling at 42 mph forward and 42 mph to the Right. According to his forward direction, I am the one making less progress and aging slower. We each see ourselves as traveling normally through time and the other aging slower. This is time dilation.

    Notice that time dilation never effects me, it only effects those that I measure as moving relative to me.
  18. Nov 9, 2009 #17


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    Re: Trying to understand the "Why" or Relativity.

    A general comment.

    The universe isn't obligated to work the way one thinks it ought to - it works the way it does. I'd like to suggest focusing on how it actually does work, and spend less time complaining about how it "should work".

    As far as time goes - the idea that it flows at all isn't all that useful. I'd suggest focusing on clocks. It's a fact that if you take one clock on a trip, and leave the other behind, when they get back, they won't have the same time reading. It's hard for some people to accept this as a fact, they don't think it ought to work that way, so they just reject it.

    If you accept this as a fact, and start trying to work out the consequences, though, y ou can start to get somewhere.

    One of the consequences is that time is not totally separable from space. Part of the idealization process that goes on is that time "ought to be" independent of motion. However, this turns out not to be the case as the twin experiment shows.
  19. Nov 10, 2009 #18
    Re: Trying to understand the "Why" or Relativity.

    Because nothing can travel faster then light speed.
    All the relativity arises from this simgle statement.

    Rather than thinking of it as a limit, think of it as a constant.
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