1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

How far does a photon move in the time dimension when it travels for one second?

  1. Dec 24, 2005 #1
    How far does a photon move in the time dimension when it travels for one second?
    How far does a photon move in the spatial dimension when it travels for one second?

    How far does a golf ball move in the time dimension when it stays stationary on a tee for one seceon?
    How far does a golf ball move in the spatial dimensions when it stays stationary on a tee for one second?
     
  2. jcsd
  3. Dec 24, 2005 #2

    Mk

    User Avatar

    1 second. When you say "how far," you imply distance, you're talking about a spatial dimension.
    The speed of light in a vacuum is defined to be exactly 299,792,458 meters per second. In one second how far does it go?
    :confused: How far do you think the golf ball moved if it didn't move?
    Are these homework questions? If so, you should post them in the Physics/Math Homework sections.
     
    Last edited: Dec 24, 2005
  4. Dec 25, 2005 #3
    Hello,

    I thought that Einstein said that distance and time could be measured in the same units--that they are both dimensions.

    Have you ever heard of relativity?

    I think it's fairly famous.
     
  5. Dec 25, 2005 #4
    I don't see any of the postulates of relativity translating directly to this. Spatial dimensions still have different units (or dimensions if you will) than time.
     
  6. Dec 25, 2005 #5

    JesseM

    User Avatar
    Science Advisor

    What do you mean by "moving in the time dimension"? If you got this term from Brian Greene's book, you should know that his description of relativity is sort of idiosyncratic and not how relativity is usually described in textbooks. He defines "movement in the time dimension" in terms of the amount of time ticked on a clock which is moving in some frame as compared with the time ticked on a clock at rest in that frame. Since clocks appear to slow down as they approach the speed of light, then under this definition, the amount of "movement in the time dimension" would be zero.
    One light-second, or 299,792,458 meters.
    Using Brian Greene's definition (which again, is not a standard one) the golf ball would have moved one second in the time dimension in the tee's rest frame, and 0 meters in the spatial dimension.
     
  7. Dec 25, 2005 #6

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    Yes, it is. You should look it up. Yes, Einstein said distance and time could be measured in the same units. He didn't say they should! For one thing, you would have to multiply by a factor of "i" to get back to standard time units (sec.). The answers Mk gave make the most sense.
     
    Last edited: Dec 25, 2005
  8. Dec 25, 2005 #7
    So you're saying that Brain Greene and Einstein are wrong?

    Briane Greene never contradicts Einstein, so if he is wrong then Einstein is wrong.

    Do any of you idiots have brains?
     
  9. Dec 25, 2005 #8

    Doc Al

    User Avatar

    Staff: Mentor

    Please refrain from insulting our members and advisors. (Especially when your knowledge of relativity comes from reading a pop science book!)

    Nonetheless, it is common when drawing space-time diagrams to use the same units to measure time and space. One measures time in units of length by multiplying the time by the speed of light (a universal constant). I think this is what you are talking about. (Talking about "how far" something moves in the "time dimension" makes it sound much more mysterious than it is.)

    So one second of time equals one light-second of "distance" in the "time-dimension". (One "light-second" = 3x10^8 meters.) Don't read too much deep meaning into this.

    You can also measure time in standard time units (like seconds) but measure distance in units of light-seconds. Again, this just makes it easier to draw diagrams and discuss relativistic effects.
     
  10. Dec 25, 2005 #9
    Hello Doc Al

    Thanks for giving a correct statement. I do appreiate it.

    Here are the pop science books which have taught me about relativity:

    Einsteins' Meaning of Relativity
    Wheeler & Taylor's Spacetime Physics
    Misner, Wheeler, Thorne's Gravitation

    I do hope that these pop physics books are up the standards of these forums.

    The reason that time and space can be measured in the same units is not for the sake of pretty pictures, but because they are both one and the same thing on a fundamental level.

    Doc Al--do you have a Ph.D.? If so, where from?
     
    Last edited: Dec 25, 2005
  11. Dec 25, 2005 #10

    Doc Al

    User Avatar

    Staff: Mentor

    :rofl: I don't for a second believe you've even cracked the cover of those books.

    Yes, but so what?
     
  12. Dec 25, 2005 #11

    Astronuc

    User Avatar

    Staff: Mentor

    Perhaps in the sense that they are coordinates in space-time, but the relationship between time and the spatial dimensions is different than the relationships among the spatial coordinates.
     
  13. Dec 25, 2005 #12
    Why don't you believe that I've read those books?

    I actually edited a book on space time physics.

    This site is an embarrassment to physics.
     
  14. Dec 25, 2005 #13

    rho

    User Avatar

    Maybe Doc Al has read them and feels you would have a better understanding of relativity than your posts show if you had also read them?
     
  15. Dec 25, 2005 #14
    rho--what don't I understand about relativity?

    why is everyone so negative on these boards?

    Merry Xmas everyone.
     
  16. Dec 25, 2005 #15

    Tom Mattson

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    You mean a factor of "c", right? Well regardless, "c" is the correct factor!
     
  17. Dec 25, 2005 #16

    Pengwuino

    User Avatar
    Gold Member

    You're a smart guy, i've collected all the data for you!
     
  18. Dec 25, 2005 #17

    Tom Mattson

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    We aren't negative. We do however have a history of taking negatively to smartass trolls who come here to play games. :smile:

    I don't believe that you are really seeking help, so I see no need to keep a thread open in our Homework Help section. Go play somewhere else.

    *lock*
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: How far does a photon move in the time dimension when it travels for one second?
Loading...