Speed of Light

[dleviwing]

undef00;
The speed of light is different when moving through glass, water, or other transparent mediums. The speed of light is also different in a vacuum at the surface of the Earth than in the vacuum of space. However when we measure the speed of light in these vacuums, we obtain the exact same value.
Thus the speed of light is not constant, only the measurement of it in a vacuum is constant. We can view this as saying that light moves through the same quantity of spatial density for any given time increment. Or you can use Relativity.

I find your English very good. No need to be self-conscious. I have trouble with the English language also and it is the only language I speak.

[undef00]

ok-i somehow thought that you were meaning measurement only is constant ... somewhere else i stated that i personally think you cannot accept all human made measurement instruments in an universal (or rather close to) meaning - sure we will find them very useful within our solar system - but beyond?? - i'm not sure if i shall accept or not .... i'll accept new measurements if humans ever get way beyond moon in person + instruments - but even then you cannot be 100% sure about measurements .... first thing we have to do is - (my guess) - getting some kind of instant messaging system (i'm not talking about msn messenger )between earth and probes/ships/+++ ...

and i do know basics about light travelling thru glass, water, sugar, salt, etc...

self-conscious can mean both the contraries??? you kind of confused me again?

[gs_cmans]

You try learning Feynman model of QED which helps you get clear about the propablistic speed nature of light.

Check the Feynman lecture ; QED : Strange theory of Light and Matter.

[HIGGSBOSONS]

What Helicity Is? How Can I Understand

[AntonioLao]

What Helicity Is? How Can I Understand

I'm using helicity to describe two distinct space-time structures of the quantum vacuum field, other definitions can be found at the link http://en.wikipedia.org/wiki/Helicity

[marksnl1]

Anyone give Julian Barbour's theory a chance here, that time does NOT excist....?

[mkirkpatrick]

Anyone give Julian Barbour's theory a chance here, that time does NOT excist....?

Hello Mark,not sure about Julian Barbours theory,but I think time is
an illusion?


regards michael

[Guille]

Anyone give Julian Barbour's theory a chance here, that time does NOT excist....?

If time does not exist then I've replied to your post in the same instant that you post it, wrote it, thought it... Also, the universe ended in the same instant that it started. You were born in the same instant you are now, and that you will die. There is no 'will' for it impplies temporality. Also, the second world war and the Nazi Holocaust never happened. I wonder what Barbour would tell to those millions of Jewish who have a grand parent or great grand parent who died in an extermination camp? Also, in the pathetic and absurd hypothetical universe, the TOE has been found in this same instant, so there is no sense in us psoting, in this web page. There is no sense or meaning or depth or direction or background or nothing behind the things, for all those impply time. Being, existence itself, requiers time in order to occur itself. Once a philosophe (term which was given by the religious inquisition to all thinkers about existence and god during the 16th, 17th and 18th century) said that he was because he thought. In a paradoxically parallel manner,--maybe showing the profound relation between time and mind--I say that we are because we change. The statement can be interpret in many ways (change relates to time, to progression, to action, to thinking...), but really it's importance resides in the fact that we are extended in time, we 'have' time, we have a past (or background, which gives us identity), we are situated and thus we become subjects:which are both relative and perspective. Although we must not forget one important thing: we cannot change change, we cannot be atemporal (for to be is to be in time), we can't undo what is done, events are events, history is history, future is future, the pass of time is the pass of time. I don't understand why most people are so amazed about travelling in time, we are doing that all the time, constantly. The incredible thing, would be to liberate ourselves from time, to be static, to be in a universe where Barbour's theory is correct, to stop time, and live the absolute perfectness of the moment.

[KAC]

As I understood it, Gravity, under General Relativity and Special Relativity does not act instantly, infact I believe it's one of the main points of the whole dissertation.

As I understand it, Gravity, or Space-time distortion propagates at a measurable rate of c. That is Gravity "waves" would measure to be c.

Real quick bit on Causality, based on Guille's expression. What if the only time their is, is the one we exist in this moment. It is implied that if time was non-existent then everything would have happened already, however as Guille demonstrated this would violate Causality. Knowing that TOE is developed I would cease work on it, and assuming that it was project through deterministic calculation, that I discovered TOE, I would then violate what would be a constant of such a universe.

However that is only if the universe as a whole has a "clock". If we take the clock and place it within locality, such that this time here is happening now, and relative to that place this other place is happening then, but that place which is happening then is happening now relative to itself. We suddenly have "time" as a change of a given locality to another state, without violating Causality. Everything that happened, was going to happen, would happen, could happen, should happen, happened in that "moment".

Time is a function of the memory of a given state of consciousness. That the "past" existed is simply a memory. Can you measure the past from the present? You can infer details of the previous state, but without having measured exactly that moment you can not measure exactly the past.


Now as for super-luminal speeds? Not likely. However that doesn't say allot. Super-luminal speeds if they exist would always measure as c. We can't see faster than information gets to us. at super luminal speeds all that we know would cease. All insturmentation, known to man, relies on recieving light.

[harmonygirl]

Guille and KAC, everything you've said is correct according to our perception, but I don't believe ultimately correct. Time does not exist, it is only necessitated by motion. We are only aware, however, of events as they occur in our life time and time as linear. But this does not mean that the universe only exists in our life time, or that time is not a microcosmic limitation that is placed on our perception, but not on reality. Okay, let's have it....