View Full Version : How far can light travel?

01-10-2009, 03:18 PM
& What factors does this relate to? :hmm:

01-10-2009, 03:20 PM
depends if it has a cityrail ticket and whether the inspectors catch it early or not.

Those statues of Jesus show a lightshow coming out of his heart, that is strangely located in ht eexact middle of his chest rather than on the left, but could that light speed be different to common light speed. It would be godspeed I guess

01-10-2009, 06:05 PM

01-10-2009, 06:33 PM
& What factors does this relate to? :hmm:

As the link Scott provides says, it really depends what you mean by the question. A photon (loosely speaking a packet of light) will continue to move until it hits something. If it doesn't hit anything (empty space) then theory says it will continue to travel forever.

Mind you, extrapolation is always more speculative than interpolation.

02-10-2009, 04:31 PM
Did a photon have mass or not.. I forget?

02-10-2009, 04:37 PM
Did a photon have mass or not.. I forget?
No rest mass, but it does have momentum given by the de Broglie relation p = h/λ.

02-10-2009, 05:26 PM
Did a photon have mass or not.. I forget?

Why do you ask? A massive particle (an electron say) will also continue to travel unless something stops it.

What causes everyday things to slow down are dissipative effects like friction which don't apply to the the case of (say) a single electron (or photon) moving through empty space.

If your question is regarding gravity then light is affected by gravity. Although Newtonian gravity would not affect massless light, the relativity conception of gravity is that gravity can be thought of as altering the shape of the space that the light moves through. The affect of gravitation on light has been confirmed experimentally.

10-10-2009, 05:15 PM
Indeed, this was known in the middle ages. 14th-century logician John Buridan developed the concept of impetus, essentially the same as the modern concept of momentum. Previously, Aristotle’s followers argued that a moving object required a force to keep it moving, but Buridan proposed:

“…after leaving the arm of the thrower, the projectile would be moved by an impetus given to it by the thrower and would continue to be moved as long as the impetus remained stronger than the resistance, and would be of infinite duration were it not diminished and corrupted by a contrary force resisting it or by something inclining it to a contrary motion.”

This is a forerunner of Galileo's Law of Inertia, in turn a forerunner of Isaac Newton’s First Law of Motion.