Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

99% The Speed of Light?

  1. Jun 27, 2011 #1
    99% The Speed of Light!?!?

    1. if we move at this speed time is slow for us so what about the outer world does it seems faster to us?
    2. people say that space also contracts in the direction so if we move at this speed for long time then will it contract constantly or will it just stop this process at one point?
    3. and the last thing is if we light a torch from our space craft(we are moving at 99%C) then we will see it fasten and at the speed of C(times must be slower for us to see light faster than it really is) and at the same time any other space ship moves to our opposite direction and light's a torch then how will we see that light ? our time must fasten for us to see light at that speed of C but at the same time our time must be slow to see our torch light at the speed of C! so how can these both processes take place at the same time? remember time can run differently 4 two observers but it can't run differently for 1 observers simultaneously

    in third question i know that time can run differently 4 two objects but how can it travel at different speeds for the same object simultaneously
    u know what i am asking this question third time cuz i don't get good answers anytime!!
  2. jcsd
  3. Jun 27, 2011 #2


    Staff: Mentor

    Re: 99% The Speed of Light!?!?

    Hi Rishavutkarsh, welcome to PF!

    SMS messaging shorthand is not acceptable, please use the best English you can.

    1) We always see our own time as normal and (assuming that we are inertial) we always see other people's time as going slowly.

    2) Again, assuming you are inertial, the amount of length contraction is constant.

    3) We always see all light at c regardless of the direction. What changes based on direction is the frequency of the light (i.e. Doppler shift).
  4. Jun 27, 2011 #3
    Re: 99% The Speed of Light!?!?

    Consider the different perspectives. Observer #1, Observer #2 and the object that is traveling at C.

    Perspective of observer one is there perspective only, not that of the other two. Spacetime is the variable that leads to different measurements that all calculate the object travelling to be moving at C.

    From the perspective of the object travelling at C, it's speed never changed. What's cool, is the two observers would agree. But the observers would have different measurements of time/distance (ie spacetime) assuming one observer is moving and the other relatively isn't.
  5. Jul 3, 2011 #4
    Re: 99% The Speed of Light!?!?

    i understand that ! the problem arises when an observer observes 2 rays of light at the same time from opposite direction consider that we are moving at 99%C in a direction and 2 rays of light are emitted from our from and back simultaneously , time can run different for 2 observers but can it be different for a single observer simultaneously huh!? :confused:
  6. Jul 3, 2011 #5
    Re: 99% The Speed of Light!?!?

    really!!? but it's highly confusing i mean think about twin paradox if we would see everything outside slow then everything happens there slow so we should be more aged than them!
  7. Jul 3, 2011 #6

    George Jones

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Re: 99% The Speed of Light!?!?

    Moving clocks are not always seen visually to run slow, sometime they are seen visually to run fast.
  8. Jul 3, 2011 #7
    Re: 99% The Speed of Light!?!?

    i get it thank you but clock can move slow or fast in respect to speed of light *time dilation* like if we are 90% speed of light in a spaceship and light a torch then our time moves 10 times slower than a object at 0%C (rest) but if at 99% C in a ship then it moves 100 times as slow as 0%C as these conditions let us see light at C the outer world is faster so it should appear fast rather than slower and also if we are slow in time our 1 year=10 years (of any object at 0%C )
    twin paradox the outer world must be faster
  9. Jul 3, 2011 #8

    George Jones

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Re: 99% The Speed of Light!?!?

    Here is what happens.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: 99% The Speed of Light?
  1. The speed of light (Replies: 4)

  2. The speed of light (Replies: 7)

  3. Light speed (Replies: 5)

  4. Light speed (Replies: 8)

  5. Speed of light (Replies: 18)