Wiploc
Veteran Member
Photons travel at c, and therefore experience no time, and no distance.
People keep saying that, but I don't understand why.
Maybe they say it because understand relativity and time dilation. t = t0/(1-v2/c2)1/2.
In that equation, I understand only the equal sign.
Then again, if they don't understand relativistic time dilation, maybe they are just repeating what they heard someone who does understand it has said.
As I said, I don't understand. So I'm not trying to argue with you. I'm taking a position as an invitation to correction. I'll try to state my mathematically ignorant layman's position clearly, in the hope that you, or someone, will be able to see and correct my error.
Joe and Sara are twins. Sara gets on the rocket and blasts off for Alpha Centauri.
I don't understand t = t0/(1-v2/c2)1/2, but I assume it lets us calculate how much Joe's speed slows down (as viewed by Sara) and how much Sara's speed slows down (as viewed by Joe).
Those parentheses aren't intended to trivialize. Sara's time really does run slow for Joe, and Joe's time really does run slow for Sara. But Sara's time never runs slow for Sara, and Joe's speed never runs slow for Joe.
The faster Joe goes (relative to Sara), the slower he sees Sara's time go, until, as he approaches the speed of light, her time (from his point of view) approaches being stopped. But her time never even begins to slow down for her.
If we extrapolate, if we say, "Sara's time would stop if she got all the way to c," we're saying that Sara's time would stop for Joe. And Joe's time would stop for Sara. But their own time never even begins to slow down for either of them.
If Sara were to go the speed of light, her watch would (by Joe's reckoning) stop ticking altogether. But her trip would take over four years according to Joe. And it would take the same length of time according to Sara, because, for Sara, it is Joe's watch that has stopped ticking.
Her own time hasn't slowed down for her.
And the little photons traveling beside her, their watches haven't stopped either. So the trip takes just as long for them as it does for her.
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So, if I'm wrong, I hope someone can shed light on where my mistake is.