whats the speed of light ?

[Dandmb50]

Is a light year the speed that light travels in one year? Well then 1 light year would be the time it takes light to travel in one year at the speed of light right ? So let's say we are travelling in a space ship at the speed of light and we have the headlights on the ship turned on. Would there be a beam of light out in front of our spaceship ? Well I may be wrong but thinking back, back I do remember that the speed of light was 186,000 miles per second. Has anyone travelled that fast yet well I mean other than the "next generation Star Trekkers".......And if the lights are on and we are travelling at the speed of light I guess there would be no beam of light out in front of us ???

Daniel .....Toronto light years from everyone.

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Please feel free to email me
Dandmb50@aol.com

[mr john]

La respuesta a todas sus preguntas está, " Sí. " Thank you Babelfish.

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Signitorily yours, Mr John
" Pardon me while I have a strange interlude."-Marx

[HeadlessCow]

A light year is a measure of distance. It is how far light will travle in a vacuum in one year.

[Undead Dude]

Aw, man. Not the headlights one again :)
Cecil actually answered this, but the article doesn't seem to be avail in the archive


So let's say we are travelling in a space ship at the speed of light -- Dandmb50
Problem #1. You cannot travel at the speed of light. Allow me to be the first one to introduce you to an almost 90 year-old idea called "relativity".

An object travelling at the speed of light would have infinite mass, no experience of time, would be flatter than a pancake, and would have needed to expend an infinite amout of energy to get to that point.

If anyone wants to discuss this more deeply, I'm willing. We certainly have before. :)

Would there be a beam of light out in front of our spaceship ? -- Dandmb50
Well, for the sake of argument, let's say that you were travelling at 99.99% the speed of light. So the beam of light is going to move away from you at 00.01% the speed of light, right? Well, from your point of view, this will definitely not be the case. From your point of view, that beam of light is going to eminate from you as if you were standing still. In fact, from your point of view, you are standing still, and it is the Earth that would be whizzing away at 99.99% the speed of light.

The most fundamental idea in relativity is that there is no absolute way to decide if something is moving or not. You can only describe something as moving relative to other things. It is just as valid to say that a spaceship is standing still, and a planet is moving very, very fast.

[EvilGhandi]

If you are traveling at warp 9 and turn on the headlights, the light beam will burst from your ass at ten times light speed!
This is accomplished by having a schrodingeringer Box tied in to your warp drive, In Fignewtonian phisics, this seems impossible, until you factor in the startrekian variable, which states: Plothickening+Hawkinsomation-Einsinination=Randumbatin.
But hey, I still dont get why, when veiwed from two separate points, they will be percived to be moving at the same smeed.

I did resubmit my TEEN FAQ as modified for the web site, but it's not been posted.

... boy, does Unca Cece EVER have job security!



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Ranger Jeff
The Idol of American Youth

[AWB]

To answer the topic question:

299,792,458 meters per second

In more common units:

1,802,613,894,550.25 furlongs per fortnight
:):):):):):):):):):)

Well, actually, to answer the topic question:

What's the second baseman.



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Ranger Jeff
The Idol of American Youth

[EnigmaOne]

{{{Is a light year the speed that light travels in one year? Well then 1 light year would be the time it takes light to travel in one year at the speed of light right ? }}}---Dandmb50

{{{What's the second baseman.}}}---R.Jeff

Yup, that's a pretty accurate assessment of the situation.

My condolences to your SN Jeff. Good to see you again! :D

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--Kalél
(The Original EnigmaOne)
Common ¢ for all ages.

[StrTrkr777]

You guys. Why won't you tell this poor lad the truth?

There are secret gov't experiments going on in Roswell, not Roswell, NM but Roswell, GA. I should know that is close to where I work. Anyway. Yes, there have been people who have traveled faster than the speed of light, other than those on Star Trek, BTW, the Original Series ships could also travel faster than the speed of light not just the TNG ones.

The question about the headlights came up not long after Einstein developed his theory of relativity. It is not widely known that his brother came up with the term the theory of relativity but it was about kin folk not one object relative to another. Anyway, our gov't has spent years working on craft that would exceed the speed of light, just to be able to answer the very question of what would the headlights do. There were two groups of scientists, those that believed that the headlight would shine on ahead and those that believed the light would not be able to clear the front of the vehicle. Also, it was pondered, that eventhough Einstein said one could not go faster than the speed of light, that if a craft were going at the speed of light and someone moved from one end to the other then that person would be going faster than the speed of light.

We began developing these space craft that could travel at these great speeds. The first issue to tackle was the great amount of fuel needed. So they decided that they would need to create a fuel replicator that would make the fuel and feed the engines. Since matter cannot be created or destroyed, then, they had to take matter floating outside the ship to convert into fuel. Once this was accomplished they began their mission to determine the answer to their questions. The next problem they encountered is if they tried to stop the craft too quickly, the person would end up a big greasy spot on the windshield of the craft. Due to inertia of course. They decided that they needed inertial dampeners to keep this from happening. The costs of building these things was more than the US gov't wanted to bear, so they decided to form a secret alliance known as the Federation to fund the ongoing research. After the development of the inertial dampeners, they had to be able to accelerate within a reasonable speed. They decided that the best way to move an object was the repulsion of two opposites. They tried huge magnets, but they could not repel with out tearing the hull apart. They then tried matter and anti-matter. This gave a better repulsion than magnets and since anti-matter does not really exist there was no reaction other than a forward movement, in fact one that went really fast. All they had to do was keep the anti-matter in a position that pushed the matter in the direction they wanted to go. Reverse it to stop.

This was completed some number of years ago. The results of the tests were amazing. It seems that it depend on the headlights used and whether or not the high beams are used. If you use the old headlights, they did not escape the front of the craft. As it turns out the light from these old lights did not travel as as the light from the new halogen bulbs. Also, if the high beams were not used the light did not travel as fast. If, however, the halogen bulbs are used on high beam, then the light does indeed shine out from the space craft, though only about 30 ft. and when you are moving at the speed of light that does not do much to help you see in the darkness of space.

As for the moving faster than the speed of light, it has been documented in secret classified documents that yes, a person walking in the ship that is moving at the speed of light is indeed moving faster than the speed of light, though you cannot see them as the light that travels to your eyes is moving slower than the person, so it looks as if they are moving normally. You just have to believe it and except it on faith. Our gov't wouldn't lie.

Jeffery

[ravenous]

Uh...I think a light-year is the _distance_ that light would travel in a year. The time it takes anything to travel 1 year is...disregarding relativistic effects for 1 second...1 year.

Of course if you take relativity into account, since light is moving at the speed of light, maybe time has stopped for the photons and they have no concept of what a year is? What I don't get is why light has to travel at that speed. Can't we slow it down? Slap it around? Smack it up, whip it, rub it down?

Rav

[Lumpy]

What I don't get is why light has to travel at that speed. Can't we slow it down? Slap it around? Smack it up, whip it, rub it down?

I can't quote the source exactly, but I did read in either Discover or Scientific American that some physicists were able to slow light down. They shined a laser beam through some special medium (ions or something like that), and the photons propagated through at some fantasticly low speed- 30mph, or something like that.

I don't think that they were actually altering the fundamental speed of light; more like the ions behaved like a transparent medium with an extremely high refractive index.

Regarding the effects of near-lightspeed travel-- increased mass and compression along the line of travel-- I've often wondered if in theory if your spaceship got to a high enough speed, would it collapse into a black hole due to relativistic effects?

[k0myers]

I don't think that they were actually altering the fundamental speed of light; more like the ions behaved like a transparent medium with an extremely high refractive index

I believe that is correct, yes. You can slow light down by having it go through anything with an index or refraction >1. The real interesting thing wasn't just that they slowed it down, it was the extent to which they did. But the speed of light in a vacuum is invariant.

Regarding the effects of near-lightspeed travel-- increased mass and compression along the line of travel-- I've often wondered if in theory if your spaceship got to a high enough speed, would it collapse into a black hole due to relativistic effects?

It has been a long time since I have studied this stuff, but I believe this isn't the case. There has always been this confusion between rest mass (m0) and relativistic mass (mr). Gravitational effects are manifested by the rest mass of an object, which is identical in all inertial reference frames. So you spaceship won't become a black hole as it gets close to C, since its rest mass is remaining the same. But it will still take more and more energy to get closer to C.

My understanding is that relativistic mass is, while still a perfectly workable model, sort of a deprecated concept because it leads to just this sort of confusion, and hardly anyone ever bothered to mention whether they were talking about rest mass or relativistic mass.

k0myers

[falcon2]

Diverging from the boring physics, I'm pretty sure dear old Gene avoided assigning any conversion factor a "Warp speed" to real units. You'll note that in ST4 they take the Klingon battle cruiser direcly at the sun and floor it from earth. The scene takes several minutes, eventhough the achieve warp 10. In STNG-2 First Contact, the phoenix just breaks warp 1, yet takes practicly no time to get out passed pluto. Its also explained in the ST tech manual that warp 10 is basicly infinite speed, but in the series finally of STNG, Admiral Bev orders the engines up to Warp 13. So although its fun to dream about, its just a bunch of technobabble...uhhh. except for ion engines of course.

And now back to reality.
You can't travel the speed of light, because:
Your kinetic enery goes up, energy has mass, and time slows down. So in your hypothetical starship your engine thrust would drop off with the time dialation, and your ship would get harder to push because of the increased mass.
Not to mention that under a constant accelleration of 10m/s^2 which is about 1g, it would take over 5 years to get close to the speed of light, and another 5 years to stop.
I beleive the human speed record is about 18,000 mph which is off c by a long sight.

Light does travel at different speeds depending on the medium, and some things do go faster than the speed of light, but not the speed of light in a vaccuum.

Would there be a beam of light out in front of our spaceship ?

The speed of light is constant, you cant add it to the speed of the ship. If you emmit photons from a fastmoving object, the frequency is compressed or doppler shifted. The time dialation from the ships perspective exactly cancels this out.

What I don't get is why light has to travel at that speed.

Electric field occilations create a magnetic field wave, magnetic field occilations create an electric field wave. The two constructively interfere at exactly the speed of light. Bammo, you get electromagnetic radiation, i.e. light.

[Czarcasm]

you guys have to do everything the hard way.
Step 1. Turn on the flashlight.
Step 2. Chuck flashlight in same direction you are pointing it.
Thus increasing the speed of light.

No, I don't share my medication.

[Undead Dude]

What I don't get is why light has to travel at that speed. -- rav
Electric field occilations create a magnetic field wave, magnetic field occilations create an electric field wave. The two constructively interfere at exactly the speed of light. -- falcon2

Well, I don't think it is considered interference, tho it definitely is a chain reaction. When we talk about the speed of light in these terms, we get a bit of a chicken/egg situation. Since the time of Maxwell, we have described light as a chain reaction of changing electric and magnetic fields, however, in the newer days of QM, we speak of electric and magnetic forces as being a result of interactions with virtual photons.

Like others have said, light does travel slower in various media. The speed of light in a vacuum has more to do with the nature of space and time than it does with light itself. The speed of light is akin to infinite speed in some ways. It is the speed that a massless particle that nonetheless has momentum will go. Light is massless, so it moves at that speed (in a vacuum).

[NanoByte]

I've never been able to get a reaction out of a chain. Every time I push one out of shape, it just doubles up on me.

Ray -- missing link (http://www.encounter.co.za/html/ples.html)

PS: The reason light travels at the speed of -- well -- light in a vacuum is because, to the abhorance of nature, all vacuums suck at that speed. (I found this out by removing the bags from a bunch of them and shining a flashlight into the suckers.)

[threemae]

When thumbing through the illustrated version of A Brief History of Time, I noticed a diagram describing the impossibility of determining who was truly standing still and who was moving due to the relative sense of motion. The example given was two couples playing ping-pong, one on the sidewalk and the other on a double decker bus. Perhaps I'm wrong, but it seems quite simple to find the solution to this problem, if one could observe the speed at which light was approaching you could determine who was standing still and who was moving. The person who noticed any change in the speed of light would obviously be the one moving because we know the speed of light is constant. While typing this post, I also came up with another question, refer to the diagram below.

d e
________________________

| |
| |
\ / \ /
\ /

Imagine the light emitter (e), plane, and detector (d) are all traveling in the direction of the arrows. When the emmitor shot light towards the ditector along the plane, would the light miss the detector? Assuming the speed of light is constant (c), using the distance formula for speed (the formulas name escapes me right now) and the downward velocity (v) and the speed the light exits the emmiter is the speed of light (c), c^2+v^2=/=c^2. Something dosn't work.

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"The first thing a man will do for his ideals is lie."

--Joseph A. Schempeter

[threemae]

Sorry the diagram didn't come out well, there is a line segment with a d and e above it's deffining points. The pipe symbols make two down arrows below the line.

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"The first thing a man will do for his ideals is lie."

--Joseph A. Schempeter

[mr john]

AH gimme a break ,16 posts since mine.That's the first bi-lingual pun I have ever accomplished.( HEY you don't ask me my lingual preferences I won't ask you your's)
str you are wrong,if you are in a spaceship traveling at +C,watching aperson walk in the direction of travel, you can see the light reflected by the person,and it does not look as if the walker is walking normal, it looks like the peson is walking backward.(can we just make 'they' singular to avoid the he/she?)
Ranger, Who gets the money
evil,you misspelled 9

[k0myers]

The person who noticed any change in the speed of light would obviously be the one moving because we know the speed of light is constant.

Hello threemae,

It's a clever idea, but these sorts of things don't actually work out because relativistic velocities are not linearly additive. The only intuitive reference we have is newtonian mechanics, in which velocities are linearly additive, so a lot of things that make intuitive sense in our slow moving world don't work out for velocities close to C.

Something dosn't work.

The velocity addition issue is the key, but you can rework most of the "common" equations using the relativisitic velocity addition formula. I can't quote it to you off the top of my head (been far too many years), but I'm sure a web search would turn it up.

k0myers

[Undead Dude]

threemae:
Sounds like you are paying enough attention to get your head messed with. That's the fun part for me. :)

Perhaps I'm wrong, but it seems quite simple to find the solution to this problem, if one could observe the speed at which light was approaching you could determine who was standing still and who was moving. The person who noticed any change in the speed of light would obviously be the one moving because we know the speed of light is constant. -- threemae
Ah, but that's just the thing! No one ever observes a change in the speed of light travelling in a vacuum! The detector on the bus and the detector on the sidewalk (pretending this is a vacuum rather than Earth air) are going to determine that the speed of light is that familar constant.


Re the emitter/detector diagram. Very good example. You are so ready for a course in special relativity. ;)

Lemme modify the example a bit to illustrate the point.

Suppose we have a light beem that is passing between two mirrors. The mirrors are positioned so that it takes the light exactly 1 second to get from mirror A to mirror B (i.e. they are 1 light-second apart).

Now, suppose we have mister observer C. Mister C sees the mirrors moving perpendicular to their flat surfaces at a high speed. According to Mister C, this bouncing light is not simply going back and forth. To Mister C, the light is travelling in a zig-zag pattern. He observes the distance between mirror A and mirror B to be one light second, but since A and B are moving, and the speed of light is constant, he observes that it takes the light longer than one second to get from A to B. Let's say he sees the trip to take 1.5 seconds.

Lovely. We have a contradiction here right? Nope. Because from C's perspective, time has slowed down for A and B. From C's point of view, in the time that 1.5 seconds has passed, only 1 second has passed for A and B.

[Babar714]

Umm, yes, you can slow light down. You don't need a doctorate, either. You need a glass of water and a pencil. Oooooooh. Wasn't that cool?

1 light year is the distance it takes for light to travel in one year. Right, we know that. Stuff can slow light down, like glass, water, other particals, or gravity. So the speed of light is not constant. That's why I'm not sure I buy the whole relativity thing. Why would it take infinate energy to send a rocket at or past the speed of light? And why does your mass become infinate? This is what we call Theoretical Physics, which cannot be proven. At least not yet. Al was a smart guy, but I'm holding my breath for proveable science.

[Undead Dude]

Umm. Babar? I guess perhaps you haven't been keeping up with physics for the past 50 years or so...

In high-energy physics experiments, it is quite commonplace to accelerate particles to very near the speed of light. The effects of increased mass and time dilation are have been very well demonstrated.

[typertrphy]

StrTrkr777 ? You frighten me.

[StrTrkr777]

Why would I frighten you?

Jeffery

[falcon2]

we have described light as a chain reaction of changing electric and magnetic fields, however, in the newer days of QM, we speak of electric and magnetic forces as being a result of interactions with virtual photons

I seem to rememer something about photons, being the same thing as light. This is not true anymore eh?

It is the speed that a massless particle that nonetheless has momentum will go. Light is massless, so it moves at that speed

Energy has mass and photons have energy. Course you meant rest mass didnt you.

[John W. Kennedy]

At one time, Star Trek's "Warp Factor" was translated as c*w3. However, I believe that was obviated as of TNG.

As to light, here's the skinny. It is a known, observed fact that every observer sees light moving at c relative to him. All the weird stuff that comes out of Relativity is just the result of Einstein (and others) working out the equations so that this known fact fits.

For example, you don't have to bring in relativistic mass and all that to explain why you can't go faster than light. All you have to do is realize that no matter how fast you go to chase light, it will always be going exactly c faster than you are. Space and time twist themselves around to force this always to be true.

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John W. Kennedy
"Compact is becoming contract; man only earns and pays."
-- Charles Williams

[Alan Q]

I've always thought that a good (if simplistic-that's the way I can deal w/it) way to get a grasp of what happens to mass, acceleration and all that other happy stuff is--to go back 2500 years. One of Zeno's paradoxes is that you can't really get anywhere because you have to get halfway there first, and to get halfway, you have to get half of that, etc. ad infinitum. Of course, it doesn't hold up walking across the room, but when you get to about .99999...c, I can see a parallel.
--Alan Q

[tracer]

John W. Kennedy wrote:

At one time, Star Trek's "Warp Factor" was translated as c*w3. However, I believe that was obviated as of TNG.

You are correct, the warp-x-equals-x-cubed-times-the-speed-of-light warp speed formula was never canonized by Paramount/Roddenberry, and was formally abandoned in the TNG Scriptwriter's Bible the first year. It has been replaced with, of all things, a graph on one page of the ST:TNG Technical Manual. A footnote claims this graph was based on "Warp X = X^3.33333... times c UP TO WARP NINE", and the graph appears to match this formula. So at least in the ST:TNG days of Trek, warp 1 is 1c, warp 2 is about 10c, all the way out to warp 9 which is around 1000c. Past warp 9, your warp-speed asymptotically approaches warp 10 as your acutal speed approaches infinity.

Now, in the series finale ("All Good Things..."), one possible future showed an aging Beverly Picard commanding her starship to go to "Warp Thirteen". However, this was many years after the main timeline of the show -- perhaps Star Fleet got sick of splitting hairs between warp 9.9 and warp 9.95 and decided to recalibrate the warp speed scale -- and they made it clear at the end of the episode that this future need not even happen at all.

We now return you to your regularly-scheduled program on special relativity, already in progress.

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I'm not flying fast, just orbiting low.

[NanoByte]

The nature of the
fields is dependent on the nature of photons.

I would say the two paradigms of light are strictly posed independently in parallel. Neither depends on the other.

Ray (a small particle in left field)

[Undead Dude]

I seem to rememer something about photons, being the same thing as light. This is not true anymore eh? -- falcon2
That was precisely my point. That's what I meant by the chicken/egg thing. Photons generated by electric/magnetic forces generated by photons. See what I mean now? I was pointing out that describing the speed of light in terms of the nature of the fields isn't the most fundamental description. The nature of the fields is dependent on the nature of photons.

Energy has mass and photons have energy. Course you meant rest mass didnt you. -- falcon2
Well, that's one way of looking at it, but massless particles are kinda a special case. They do have momentum, and you can calculate their energy, but then if you try to plug that energy back into an equation that determines its (relativistic) mass, it doesn't fit with any of the other relativistic mechanics equations. For one thing, you would now be describing an object that has finite mass at the speed of light. Technically, the only intuitive way to determine the mass of a photon is inaccurate. In E = mc<super>2</super>, m is specifically rest mass, and E is specifically rest energy. For a moving body, the equation is E = gamma * mc<super>2</super>, which gives you infinity times zero.

Conceptually speaking, I have heard of light referred to as having relativisic mass, but no rest mass. However, the photon is generally referred to as a massless particle, I have never seen an equation to determine that mass of a photon directly, and, come to think of it, the last teacher who described photons as having relativistic mass was my high-school teacher.

[Undead Dude]

I'd say that the QM version is the more precise (electric/magnetic forces arise from interactions of virtual photons). The Maxwell version (photons arise from a chain reaction of chaging electric and magnetic fields) is an effective and useful classical approximation, but does not represent physical reality as much as the QM version.

[Undead Dude]

But, yeah. Like you said. They aren't really dependent on each other. They are two different ways of looking at it.

[dougie_monty]

In the late 17th Century astronomers noticed that the eclipses of Io, one of Jupiter's large moons, were coming as late as 16 2/3 minutes after they should have. Someone finally realized that this was caused by the time it took for Io's reflected light to reach Earth, and that the farther away Earth got from Jupiter, the longer it would take for the light to reach us. The distance from Earth to the Sun had recently been calculated as 93 million miles, so the Earth's orbit is 186 million miles across. Since the "error" in the eclipses of Io were coming was 16 2/3 minutes, the astronomers concluded that it took light 16 2/3 minutes to travel the distance of 186 million miles, or 186,000 miles per second.