Register to reply 
Light doesn't travel through time? 
Share this thread: 
#1
Jan2013, 07:32 AM

P: 11

According to the special theory of relativity: The combined speed of any object’s motion through space and its motion through time is always precisely equal to the speed of light.
But light travels through space precisely at the speed of light. Doesn't that imply that light doesn't travel through time? What does that even mean? 


#2
Jan2013, 08:01 AM

P: 9

I'm no expert, but I'll take a stab here.
If you were able to completely stand still in space and did not move at all, you'd not be moving through space  only through time. Now, imagine you're in a spaceship with a speedometer, and you slowly accelerate. As you speed up, you move less through space and more through time. You can easily imagine time dilation taking effect when you're at speeds much greater than normal  you'd be experiencing more time for every unit time an outside observer is looking at you. One year for you could be a second for everybody else. The closer your speedometer reading gets to c, the slower the time goes for you. When you eventually do reach c, time will be so slow, it has stopped moving completely. An infinite amount of time can pass by for you, but not a millisecond has passed for the rest of the universe. At that point, you'd be moving through space completely, and not through time. Exactly what a photon does. 


#3
Jan2013, 08:03 AM

Mentor
P: 17,534

We have had a rash of threads on this exact topic recently (must be infectious). Please spend a few minutes looking. I am getting tired of this same discussion.



#4
Jan2013, 09:29 AM

P: 4,209

Light doesn't travel through time?
See: http://www.adamtoons.de/physics/relativity.swf When you pull the speed slider towards 1c, the rocket becomes light, and the proper time goes towards zero. 


#5
Jan2013, 12:08 PM

Emeritus
Sci Advisor
PF Gold
P: 9,530




#6
Jan2013, 01:25 PM

Mentor
P: 11,864




#7
Jan2013, 02:44 PM

Mentor
P: 17,534




#8
Jan2313, 05:28 AM

P: 10




#9
Jan2313, 06:32 AM

Emeritus
Sci Advisor
PF Gold
P: 9,530




#10
Jan2313, 07:40 AM

Mentor
P: 17,534




#11
Jan2313, 08:32 PM

P: 10

SR doesn't define coordinate system moving at velocity c. These corrections were made so that light travels at the same speed in all coordinate systems. 


#12
Jan2313, 09:47 PM

Mentor
P: 17,534




Register to reply 
Related Discussions  
Light and time travel  Special & General Relativity  2  
Universe doesn't equal Time travel  Astronomy & Astrophysics  5  
Is light travel time for event time calculation usually implicit?  Special & General Relativity  5  
Light yearsdistance or light travel time?  Cosmology  3 