What really is time?

Originally posted by DrKF
Sadly, no - and I think the book is in storage in London.

The Edge has a piece where he expands, if only a little, though:

"I am convinced, but cannot prove, that time does not exist. I mean that I am convinced that there is a consistent way of thinking about nature, that makes no use of the notions of space and time at the fundamental level. And t ...[text shortened]... am also convinced, but cannot prove, that there are no objects, but only relations." 🙂

Sounds very interesting. To scratch my back a little, it goes to the notion I've posted that our view of time is perceptual and rooted in our 3D bias. Of course, I'm sure he has a more precise idea of why exactly and I can only play with thoughts without being able to pin anything down...

Perhaps time is not continuous but progresses in quanta?

After all what we 'see' is not reality when we look at atomic level.

When we 'touch' something it is just electo-magnetic repulsion between electron clouds.

Our intuition and common-sense let us down the more we delve into the esoteria of Nature.

So maybe time is completely different to our perception ... but surely it exists?!?! (HELP!)😲

Originally posted by wolfgang59
Perhaps time is not continuous but progresses in quanta?

Does light move continuously? If not, then since nothing is faster than light, doesn't that imply that time is not continuous? [/out on a limb]

Originally posted by Palynka
Does light move continuously? If not, then since nothing is faster than light, doesn't that imply that time is not continuous? [/out on a limb]

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 could be the perception of moving from one state to another with imperceptible differences.

Perhaps the 'size' of those time quanta could define the speed of light?

Probably talking bolocks but its fun to speculate. 😀

Originally posted by wolfgang59
Perhaps the 'size' of those time quanta could define the speed of light?

Probably talking bolocks but its fun to speculate. 😀

Yeah, that was kind of what I was getting at. If those are quanta then they are not continuous, so "time" cannot be distinguished from continuous or discrete, as we will only be able to see as in a film reel. For all practical purposes, it would be as if discrete.

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.

Originally posted by Dolphin55
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 measur ...[text shortened]... servers on the Earth all have the same reference points and therfore have a common time frame.

well, the velocity of light does vary with the medium through which it travels, but I suppose it remians constant while traveling through any particular medium. So the only place it is not constant is at the interface of different materials?

Originally posted by joe shmo
well, the velocity of light does vary with the medium through which it travels, but I suppose it remians constant while traveling through any particular medium. So the only place it is not constant is at the interface of different materials?

...and if the medium is not homogenous, then the speed of light is not constant at all.

But that is besides the point. In perfect vacuum the speed of light is constant. According to definition.

Originally posted by joe shmo
well, the velocity of light does vary with the medium through which it travels, but I suppose it remians constant while traveling through any particular medium. So the only place it is not constant is at the interface of different materials?

Sorry old chap I think your wrong. When you say through a medium what do you mean - a gas?
The speed of light does not vary. Light travels in straight lines at a constant speed.
Light can be bent by gravity, which effects the distance it travels but it's speed does not change.

Originally posted by FabianFnas
...and if the medium is not homogenous, then the speed of light is not constant at all.

But that is besides the point. In perfect vacuum the speed of light is constant. According to definition.

No. The speed of light is found to be constant through experiments/proof.

If it was so by definition then most relativity problems could be solved by changing the (quite random) definition.

Originally posted by Dolphin55
Sorry old chap I think your wrong. When you say through a medium what do you mean - a gas?
The speed of light does not vary. Light travels in straight lines at a constant speed.
Light can be bent by gravity, which effects the distance it travels but it's speed does not change.

Wrong, wrong, WRONG

The speed of light depends on the medium through which it travels.

c = speed of light through a vacuum. (which is a CONSTANT)

if light did not slow up through various media (like glass) we would not have refraction and hence no lenses, no eye-glasses, no telescopes ... etc.

I believe the slowest velocity of light recorded is something like 50mph.... I know it is less than the UK motorway speed limit!! (That sort of sticks in my mind!!)

Originally posted by TheMaster37
No. The speed of light is found to be constant through experiments/proof.

If it was so by definition then most relativity problems could be solved by changing the (quite random) definition.

Experiments show the speed of light is dependent on medium as fabian has already stated.

Originally posted by joe shmo
well, the velocity of light does vary with the medium through which it travels, but I suppose it remians constant while traveling through any particular medium. So the only place it is not constant is at the interface of different materials?

Quite so.
Its at the interface that we get the refraction. e.g. looking at fish in a pond

Originally posted by wolfgang59
Experiments show the speed of light is dependent on medium as fabian has already stated.

If you look closely you'll see I responded to a claim that 'the speed of light is a constant by definition'.

As I said, that is not the case. I make no claim about different media.

Originally posted by TheMaster37
If you look closely you'll see I responded to a claim that 'the speed of light is a constant by definition'.

As I said, that is not the case. I make no claim about different media.

Apologies. The fisrt sentence of your repy to fabian is "no" ... seemed you were disagreeing whole-heartedly with his post. My mistake.