The speed of light; another perspective.

[wonderboy]

I was cycling to work this morning and my mind was doing somersaults as per usual and I thought of something quite peculiar and it occupied my mind for the full 10 mile trip to work...

Our little planet takes 365 (give or take a day or two) days to orbit our sun, this is known as a year. Simple stuff really.

For every second in this year, light will travel at 186282.4 miles per second, this is the speed of light, and there are 31536000 seconds (approximately) in a year.

Now...

Say you lived on a planet which took 1000 days to orbit its sun, then thats 86400000 seconds in a year. this is a much longer time to orbit your parent star than earth and gives an alien race a completely different outlook on what a year is.

My point is this...



If we class a light year based on what we call a year, then surely an alien race would have a fundamentally different view of what a light year is based on their understanding of a year.

With the difference in orbital time, would an alien race's light year be much further than our own? Or shorter, as the case may be?




Paul

[Henning Makholm]

Say you lived on a planet which took 1000 days to orbit its sun,
...
If we class a light year based on what we call a year, then surely an alien race would have a fundamentally different view of what a light year is based on their understanding of a year.

Sure, they would use the word (or rather the equivalent expression in their language) for a longer distance. But I don't think there is anything "fundamental" about the difference. A lightyear is a fairly arbitrary unit anyway.

Certainly I cannot see that it would make any difference for our more philosophical notions about lightspeed. We have absolutely no intuition about those speeds and distances anyway (and "a lightyear per year" would still work as well for illustrating the speed of light, that is, not at all).

[rstevenson]

On weekdays, I'm 72" tall. But on weekends, I'm 183 cm tall.

You just wasted an entire 10 mile (8.68976241167232 nautical miles) bicycle trip thinking about that.

Rob

[wonderboy]

i think I might have came across wrong. I was thinking more along the lines of time. Like a 3 light year distance to us, might be only a 1 light year distance to another race. I know the speed of light is constant.

But your right Rob, it was a wasted bicycle trip because it was only so I could get to work

Sadly I'm in till 5pm


Paul.

[Amir]

maybe we can use "light seconds" when talking to them! of course what we mean by Second should be explained first.
Wikipedia says:

Since 1967, the Second has been defined to be the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom.

actually i guess it would be a long story to explain what we mean by "atom", "radiation", "caesium",.... because they may also have another expressions for them in their language.
so i advice you Paul, to just ignore an alien if you saw one.

[wonderboy]

No way, id be asking them round for dinner, just hope its not me their they're (what a fool I make of myself because of my grammar) eating lol.

Paul

[The Code]

No way, id be asking them round for dinner, just hope its not me their they're (what a fool I make of myself because of my grammar) eating lol.

Paul

I wouldn't, From the last 100 years of radio signals streaming out into space, they may have a preconception of you.

But what you said was interesting. If a alien race lived on a planet which had ten times the mass of earth, there conception of time would be different. On the basis time runs slower to their understanding. One second for them, may be different for us. so our 186,000 m/p/s may be a greater distance for them. but what ever figure for them, it will be a constant figure.

Interesting.

tc

[Chris Peterson]

If a alien race lived on a planet which had ten times the mass of earth, there conception of time would be different. On the basis time runs slower to their understanding.

How do you figure? You're not talking about the GR relationship between gravity and time contraction, are you? Because it would require the most exquisitely sensitive instruments to measure the difference in time flow between a 1G and a 10G gravitational field. No living thing would be remotely capable of detecting the difference with natural senses. Beings living on a 10G world would see the Universe exactly as we do.

[swainy]

Because it would require the most exquisitely sensitive instruments to measure the difference in time flow between a 1G and a 10G gravitational field. No living thing would be remotely capable of detecting the difference with natural senses.

It would be the "second" that changes. The distance of light in one second is a long way. if 1 second for us is 1.1 for them. They would say the speed of light, is not 186,000 miles per second. Is all i was saying.

tc

[Chris Peterson]

It would be the "second" that changes. The distance of light in one second is a long way. if 1 second for us is 1.1 for them. They would say the speed of light, is not 186,000 miles per second. Is all i was saying.

Light would travel at exactly the same speed for them as us. The speed of light is a universal constant- in a vacuum it always travels at c. A gravitational field doesn't change that. Time would flow no differently for them, either. Each reference frame would experience normal time flow, and see other frames with different flows.

[swainy]

A gravitational field doesn't change that. Time would flow no differently for them, either. Each reference frame would experience normal time flow, and see other frames with different flows.

Yeah, You may find this article interesting:


http://www.intalek.com/Index/Projects/R ... Clocks.pdf

tc

[Chris Peterson]

Yeah, You may find this article interesting: http://www.intalek.com/Index/Projects/R ... Clocks.pdf

Sure, I know about how relativity affects satellite clocks. But you need to understand that if you were on the satellite, you would not be able to detect a difference. A second would be a second, light would still travel at c. You'd be writing articles about how relativity affects the clocks back on the ground. That's what relativity means!

[swainy]

Yeah, You may find this article interesting: http://www.intalek.com/Index/Projects/R ... Clocks.pdf

Sure, I know about how relativity affects satellite clocks. But you need to understand that if you were on the satellite, you would not be able to detect a difference. A second would be a second, light would still travel at c. You'd be writing articles about how relativity affects the clocks back on the ground. That's what relativity means!

And unless they where good a guessing, there second would not match our second. bigger planet, shorter/longer year, longer/ shorter day. And through in a relative change in time. There is no way, there clock will match ours. so there speed of light will be different to ours.

tc

[Chris Peterson]

And unless they where good a guessing, there second would not match our second. bigger planet, shorter/longer year, longer/ shorter day. And through in a relative change in time. There is no way, there clock will match ours. so there speed of light will be different to ours.

No it won't. If that were the case, there would be preferred frames, and there are not. All frames are local. After some period of time, a comparison of clocks will show a difference. But every frame will always see their clock as the "correct" one, with all the others "wrong". This idea is fundamental to relativity.

(Actually, talking about satellites kind of contaminates the discussion of the effects of gravity, because an orbiting satellite is in a clearly non-inertial frame, while the observer on the planet below is in a different non-inertial frame. A rigorous analysis of how the Universe appears from each frame is very complex.)

[swainy]

And unless they where good a guessing, there second would not match our second. bigger planet, shorter/longer year, longer/ shorter day. And through in a relative change in time. There is no way, there clock will match ours. so there speed of light will be different to ours.

No it won't. If that were the case, there would be preferred frames, and there are not. All frames are local. After some period of time, a comparison of clocks will show a difference. But every frame will always see their clock as the "correct" one, with all the others "wrong". This idea is fundamental to relativity.

(Actually, talking about satellites kind of contaminates the discussion of the effects of gravity, because an orbiting satellite is in a clearly non-inertial frame, while the observer on the planet below is in a different non-inertial frame. A rigorous analysis of how the Universe appears from each frame is very complex.)

From that, I get you have gone half way to saying yes. I was going to ramp it up to a full blown 5 years orbiting a s/m/b/h. and a five year difference in time. But I won't, hey check the time. This is England you know.

Cheers Chris

tc

[Beta]

...unless they [were] good [at] guessing, [their] second would not match our second. Bigger planet, shorter/longer year, longer/ shorter day. And through in a relative change in time. There is no way, [their] clock will match ours. So [their] speed of light will be different to ours.

No, it will be the same, they'll just use different units. Do you think that water boils at a much higher temperature in the US than in the UK because you use the metric system?

[Excession]

The mistake here is in the assumption that 'light year' is a fundamental measure, when it's a derived one.

You can derive any number you like from the constant.

the measures used (Length:Metre, Time:Second, Mass: kilogram.) are standards we 'measure' things by. Before we could compare our values for (Metre/Second) with an alien race's values for Length and Time, we have to make the conversion -- their equivalent of M/S/K for ours. THEN we can derive units.

The constant will be a constant, no matter if it's inches per nanocentury, or furlongs per fortnight.

Put this string into google: 2 furlongs per fortnight

Hope that helps.

[swainy]

...unless they [were] good [at] guessing, [their] second would not match our second. Bigger planet, shorter/longer year, longer/ shorter day. And through in a relative change in time. There is no way, [their] clock will match ours. So [their] speed of light will be different to ours.

No, it will be the same, they'll just use different units. Do you think that water boils at a much higher temperature in the US than in the UK because you use the metric system?

Thanks for correcting my spelling mistakes, I appreciate it.

tc

[swainy]

Excession:

Thanks mate.

comment noted,

tc

[Chris Peterson]

From that, I get you have gone half way to saying yes.

Nope. C is a constant. Everybody will measure the same value, regardless of where they are or how strong their gravity. A light year is the distance light travels in some unit of time. Everybody will measure the same light year, regardless of their local environment.

The only thing that can involve tricky math is comparing two non-inertial frames to each other. This has nothing to do with how those in one of the frames see constants.

[Henning Makholm]

(Actually, talking about satellites kind of contaminates the discussion of the effects of gravity, because an orbiting satellite is in a clearly non-inertial frame, while the observer on the planet below is in a different non-inertial frame. A rigorous analysis of how the Universe appears from each frame is very complex.)

Huh? The satellite is in free fall. You can't find a more inertial frame than that within GR.

[swainy]

Nope. C is a constant. Everybody will measure the same value, regardless of where they are or how strong their gravity. A light year is the distance light travels in some unit of time. Everybody will measure the same light year, regardless of their local environment.

But they will be wrong. because, light does not travel at ((300,000 Jarvek per Priniqual.) A nonsense statement Huh?) The speed of light is constant. But the speed of a universal second, will be different throughout the whole universe.

tc

[Chris Peterson]

But they will be wrong. because, light does not travel at ((300,000 Jarvek per Priniqual.) A nonsense statement Huh?) The speed of light is constant. But the speed of a universal second, will be different throughout the whole universe.

I'm afraid you don't understand the concept of a universal constant.

[makc]

This thread is so wrong on many levels I guess what mark/wonderboy are trying to say is that if the aliens had three legs, like in last War of worlds movie, their binary would have three digits - 0, 1 and 2. And that explains why we couldn't hack into their computers and turn shields off like we did in Independence day.

[swainy]

This thread is so wrong on many levels I guess what mark/wonderboy are trying to say is that if the aliens had three legs, like in last War of worlds movie, their binary would have three digits - 0, 1 and 2. And that explains why we couldn't hack into their computers and turn shields off like we did in Independence day.

negative. into positive. Check back up the list and see how many wanted to join in the conversation. But need somebody to dig a real big hole (dissection) in the universal gravitational constant to understand better why E=MC-^2

And if one person gets to grips with this, because of the above conversation, then we have won, Huh?

http://en.wikipedia.org/wiki/Gravitational_constant