Originally posted by wolfgang59
Well light has a constant velocity through a particular medium - it does not move in fits and starts - so it does move continuously. Or at least that is how we perceive it.
I was thinking of time as a series of images like a film. We perceive continous movement on the screen but in fact we are really seeing a series of 'almost identical' states. Time ...[text shortened]... ta could define the speed of light?
Probably talking bolocks but its fun to speculate. 😀
Light has a constant velocity - fullstop. There is no particular medium - as far as I am aware we can't slow light down or speed it up therefore it is constant.
Someone earlier mentioned time dilation, which I think is really helpful in trying to explain what time is.
If you imgine that time is a specific distance travelled by light then you can measure time by the distance light has travelled.
I think it was Einstein that came up with the analogy of someone on a train and an observer on the platform watching the train go by.
Imagine the observer on the train had a light source that shone a light down to a mirror and the light bounced back up - this took one second (I know the figures are too slow - but this is a thought experiment). This would pulse and the observer on the train could keep time.
The observer on the platform would see the train rush by and see the light. He would measure the distance the light travels and would see that the time was longer than one second.
An explanation: the light would come on at point (a) the train would move to point (b) the light would hit the mirror at point (b), the train would move on to point (c), the light would be back at the source. Effectively making a V shape.
It's basically an inverted quadrilateral triangle and is a longer route than straight up and down therefore longer.
The answer to the question is that time is a measure relative to the observer. The observers on the Earth all have the same reference points and therfore have a common time frame.