Time

[grey_beard]

Yes, light(not just visible light, but photons in general) determines time, because nothing moves faster than light. You could think it like this: Light is the speed of time because it moves freely in space without mass, while massive objects are sort of slowed down because in them, the energy that they are made out of is tangled up circling in one spot(this is basically what mass is) instead moving freely from point a to b like light does.

Time is essentially nothing but a moment of observation. And because the moment of observation cant happen before photon travels from point a to b, time is relative to observer and again because light is the fastest thing, it determines time:

But i think time as a general term is bit outdated because it can mean multiple things.

Google Cerenkov radiation, please? It is possible for massive objects to exceed the speed of light in a particular material (though not in vacuum).

 

[Xander]

In specific to the video, I need to do lots of reading for the rest it seems, what is the actual "real" outcome though? According to that setup the passenger on the train draws an incorrect conclusion due to her position and perspective. Doesn't that undermine the validity of her observation?

To my mind if I look at someone through the bottom of a pint glass they look very attractive but to everyone else who's sober they're actually a munter. Who's perspective is reliable to determine the actual state of the person being viewed? wouldn't we call that an impairment of judgement rather than a revelation in physics?

I guess what I need to find is an example that I understand of why this kind of stuff is worth knowing. How is it applicable to reality or is it just a cerebral entertainment piece dreamt up by people locked away with their books for too long?

 

[sprinkles]

In specific to the video, I need to do lots of reading for the rest it seems, what is the actual "real" outcome though? According to that setup the passenger on the train draws an incorrect conclusion due to her position and perspective. Doesn't that undermine the validity of her observation?

To my mind if I look at someone through the bottom of a pint glass they look very attractive but to everyone else who's sober they're actually a munter. Who's perspective is reliable to determine the actual state of the person being viewed? wouldn't we call that an impairment of judgement rather than a revelation in physics?

I guess what I need to find is an example that I understand of why this kind of stuff is worth knowing. How is it applicable to reality or is it just a cerebral entertainment piece dreamt up by people locked away with their books for too long?

That's the thing about relativity - both views are valid and neither are absolute, since if we add a third observer in the right place, both of the other two observers seem wonky. Such as an alien watching the train from orbit.

 

[sprinkles]

[MENTION=70]Xander[/MENTION]
And as for why it's worth knowing, the properties of light in relativity are useful for doing things with optics and lasers, such as laser gyroscopes which can determine the orientation of an object. Put simply, relative differences in the perceived speed of light to the observer (which is the gyroscope's light sensors in the case of the gyroscope) allows the gyroscope to detect how it is rotating, if at all. This is useful for guidance systems, such as telling a robot or satellite which direction it needs to point.

 

[INTP]

Google Cerenkov radiation, please? It is possible for massive objects to exceed the speed of light in a particular material (though not in vacuum).

Thanks for wasting my time googling this. Even tho this radiation goes from point a to b faster, its only because light travels a longer distance between a and b because its path is altered so much by electromagnetic fields in mediums where this radiation can go from point a to b faster than light. So no, it doesent actually go faster than light.

 

[grey_beard]

Yeah, but it makes such a pretty blue glow!
(Like the nuclear reactor at the end of James Bond's Dr. No.)

 

[INTP]

In specific to the video, I need to do lots of reading for the rest it seems, what is the actual "real" outcome though? According to that setup the passenger on the train draws an incorrect conclusion due to her position and perspective. Doesn't that undermine the validity of her observation?

To my mind if I look at someone through the bottom of a pint glass they look very attractive but to everyone else who's sober they're actually a munter. Who's perspective is reliable to determine the actual state of the person being viewed? wouldn't we call that an impairment of judgement rather than a revelation in physics?

I guess what I need to find is an example that I understand of why this kind of stuff is worth knowing. How is it applicable to reality or is it just a cerebral entertainment piece dreamt up by people locked away with their books for too long?

How should i explain this.. First of all your opinion of someone attractiveness in that situation is relative to how many beers you had, its also relative to the observer because someone in the world might see her as attractive even when sober. But back to the topic, because that has nothing to do with time, just how things are relative. The actual real outcome depends on position of observation. The whole point is that there is no one correct point in time, because its relative, and its relative because light has a speed and it takes a while for it to travel from point a to b.

Think about this; There is a spaceship that accelerates to you right near speed of light suddenly and it is directly in front of you really far away, but the ship is large enough for you to see it properly. Like this:

First pic is the spaceship stationary, second one the spaceship just after it started to accelerate and is already going near speed of light. Now if you look at it, you can see that in the second picture the light coming from the front of the ship needs to travel a longer distance than the light coming from back of it. So by the time that the light coming from the front sent by the moment on second picture comes to you, there is already light sent by a later moment coming from the back, so the spaceship appears to be shorter in your perspective(and also brighter) when it accelerates to near speed of light and is going away from you. Then again if the spaceship would accelerate before the middle point, you would perceive it to be longer and dimmer than when it is stationary. But the trick is that if that spaceship had any sort of effect on you(other than sending photons), those effects would be as if coming from the shorter version of the ship, so all that really matters from your perspective is that the ship is shorter for a period of time. This sort of stuff needs to be taken in account on stuff like gps navigation(gps satellite clocks run 38 microseconds faster per day than on earth due to relativity) and other real life situations, so this relativity of time is not just some purely theoretical stuff.

 

[grey_beard]

I think you would do well to study into quantum mechanics, my preference for this field of thought (and it appears you would take well to it also).

Quantum mechanics - Wikipedia, the free encyclopedia

If Einstein's take on the universe is analog, quantum mechanics is the digital age. Nice stuff.

Naah. You need to read more. Einstein was involved in quantum mechanics as well: his Nobel Prize was for the Photoelectric Effect, which kinda sorta demonstrated experimentally
that light carried energy in discrete, err, well, shall we call them 'quanta,' of energy? (He also did work on Brownian motion, which if you squint, has to do with little bitty particles
bumping and jostling another one in a random manner.)

Louis deBroglie's work postulating the wave nature of electrons was a hop, skip, and a jump from Einstein's quantization of light (if light can act like a particle, they what the hey,
why can't particles act like waves? Turnabout is fair play and all that.)

Secondly, quantum mechanics and relativity generally hold at opposite regimes, so to speak: quantum mechanics for items small enough compared to Planck's constant, that relativistic effects become apparent; and relativity for items moving fast enough, or items massive enough, that relativistic corrections to classical equations of motion apply.

The two *can* overlap -- for example in electronic structure theory, for inner electrons in heavier atoms, where their velocity is an appreciable fraction of c.