Physics question; re; Speed of Light conundrum

[SirFshAlot]

I am currently reading The Elegant Universe by Brian Greene.

According to this author, physics asserts that the speed of light is not relative to an observer.
That light moves at 670 million miles/hour regardless of your motion towards or away from it.


Hypothetical situation;

A photon leaves a celestial object that is one light year away from earth. A light year is 5,869,200,000,000 miles away, isn't it?
A being leaves that same object at the same time, but in opposite directions, and at only half the speed; i.e. 335 million miles per hour.
Let's wait six months.
The photon is now 2,934,600,000,000 miles from the earth. (right?)
And the being is 1,467,300,000,000 miles from it's source, and 7,336,500,000,000 miles from earth.
What would be the logical inference to the distance between the being and the photon? 4,401,900,000,000 miles?
If I read this assertion correctly about physics view on it, it would lead to the distance being 2,934,600,000,000 miles from the being.

Please help me out here.

Craig

 

[Viper GTS]

What is it with you & physics questions?

The way I understand it is if you were measuring the speed of that light as you were traveling away from it, it would read the same whether your were moving or standing still.

But I'm probably wrong, I'm used to it by now.

Viper GTS

 

[TripleJ]

I don't get what your conundrum is? A photon is moving in one direction at a certain speed, and the being at a certain speed in another direction. What is your question?

 

[Urinal Mint]

I think what he is saying is that light moves at the same speed regardless of how you perceive it. It will never appear to be faster or slower than 670E6 mph, whether you are moving in a way that you would logically think it would make you perceive it moving at a different velocity.

What he's trying to say is that even if you're moving at .5c (direction being irrelevant), light will always appear to be travelling at "the speed of light" to you while you move.

 

[Electric Amish]

I would think that the photon would appear to be moving slower if you were moving in the opposite direction and faster if you were moving towards it.

When, in all reality, the speed never changes.

amish

 

[Cattlegod]

<< If I read this assertion correctly about physics view on it, it would lead to the distance being 2,934,600,000,000 miles from the being. >>



yeah, that sounds right. i love this theoretical stuff a lot. as far as i know, we don't know why this is true, but this is just what happens. the interesting this is ( correct me if im wrong however ) that all time is stopped for the photon and for the person going the opposite direction, time is dramatically slowed down. slowed down infact that over the period of 6 months he *should* have been 4,401,900,000,000 miles, but didn't have enough time and only went 2,934,600,000,000. and this goes back to the theory that time is not constant either, hence the shorter distance.

am i making sense?

 

[SirFshAlot]

look at the hypothetical situation I offered

speed = distance over time

explain the distance of light, over time, for a being that is making distance over that same time in a different direction

 

[TripleJ]

That is incorrect then. For starters, you wouldn't be able to see the photon anyway because for you to be able to see it, it needs to hit your retina.

 

[SirFshAlot]

but didn't have enough time and only went 2,934,600,000,000. and this goes back to the theory that time is not constant either, hence the shorter distance.

thanks for making my head hurt even more

 

[SirFshAlot]

TripleJ,

you wouldn't be able to see the photon anyway because for you to be able to see it, it needs to hit your retina.

thanks, but that is irrelevant to measuring the distance

I don't care if the being is blind. We can still discuss the measurement.

 

[Cattlegod]

<< thanks for making my head hurt even more >>



ill try and clear it up a bit.

you said 6 months passed as an observer of the system. however, in reality, say, only a month (abstract guess, just for example) passed in the system, not 6 months.

 

[SirFshAlot]

ill try and clear it up a bit.

I've been reading on that issue, but didn't consider it in my scenario.

Baby steps

 

[Urinal Mint]

Let's do the time warp again!

 

[Viper GTS]

speed = distance over time

explain the distance of light, over time, for a being that is making distance over that same time in a different direction

But perception is not necessarily equal to reality.

And in the end, how will we really know? We can't get anywhere near the speed of light, not even .5c. So it's all theoretical anyway.

Viper GTS

 

[Cattlegod]

oh, here is another tid bit that might be interesting.

anything past about 10% the speed of light, about all physics equations begin to fall apart. the reason is time starts to distort significantly at that speed, and speed measurements (distance over time d/t) are dependent on time and are therefore skewed.

 

[Urinal Mint]

Cattlegod: Yep, that was a point I was about to bring up. Newtonian physics go right out the door at that point.

 

[SirFshAlot]

So it's all theoretical anyway.

yes it is

but for physics, it's paramount to understand light, before it can apply facts/assumptions to other theories that are based on light, and/or the speed of light.

 

[SirFshAlot]

about all physics equations begin to fall apart

what should we infer, then, about the physics equations?

 

[Urinal Mint]

You should basically infer that basic Newtonian physics doesn't apply anymore at the speed of light. d = v*t is null and void when v>.1c

Time distorts, and we open up a new can of worms that allows light to be the same distance away from you that it always has been.

 

[Netopia]

It's just one of those universal limitations.

Though the perceived speed would remain constant the distance travelled would not balance with what we would normally use to calculate the situation. Isn't this where Einstein's Special Theory of Relativity comes in? I don't thing you can use ideas of General Relativity to judge things at near light speed.

Joe

 

[SirFshAlot]

Time distorts, and we open up a new can of worms that allows light to be the same distance away from you that it always has been

That's pretty disconcerting, though, to think that all the work done in physics is only useful to the point that objects, other than light, stay in a relatively slow state of motion.

 

[Netopia]

Since the universe is finite, perhaps it's not so disconcerting when you consider that probably 99.9+% of the universe will always remain slow since there is only a limited amount of energy avialable to propel stuff.

Joe

 

[Athanasius]

<< about all physics equations begin to fall apart

what should we infer, then, about the physics equations? >>





That nothing measurable will ever supply us with a unifying connective principle?

That there is most likely a non-local, non-material Implicate Order behind all other implicate and explicit orders?

Now one can see why a fair number of physicists become mystics, idealists, and theists.

 

[TripleJ]

This 'conundrum' seems to be blown out of proportion. If we take SirFshAlot's first hypothesis:

Speaking relatively, we would not be able to see the photon(object) because we are travelling away from it at an overall speed faster than the speed of light. This means that photons bouncing off of it would be going .5 the speed of light slower than us.

Is that what you're trying to get at?

 

[Cattlegod]

one thing i've noticed in physics is that everything fails at extremes. when i noticed that, i applied it to everything else. the general theory of relativity failes at extremes ( sub atom level ), quantum mechanics can't explain things on the other extreme ( larger than sub atomic ). also things that fail at extremes are black holes, and the question about how big is space.

some real world examples about how things fail is rev your engine to far and it fails, squeeze a ketchup bottle to hard and it explodes.

i just thought of another example to answer your original question.

we know how physical objects act at slow speeds, as well as how fast ketchup comes out of the bottle at low pressure. so by what you are saying if to objects go a 2 mph away from each other, then they should be 8 miles apart after 2 hours. we can test this and say that it is true. now, if you take the extreme and have the objects go a 10 trillion miles per hour away from each other, then in two hours they should be 40 trillion miles apart. but this is false.

now, take my ketchup example, you put 2 psi of pressure on the bottle and it comes out at say a gallon per min. so after 2 min you will have pushed out 2 gall. ( its a big bottle ) so in theory if you put a million psi on the bottle it should come out really fast, but we know this is false because the bottle will explode.

see my point?