I herd a realy quick news bulletin where they said that Australian scientists thought they had found evidence for the speed of light slowing down
Is this bullshit?
Have any of you heard anything about this?

Heard it, thought it was fairly stupid.

What the're talking about is they were measuring very distant galaxies, and the light they were seeing didn't seem right. A few computations later and they come up with the theory that from the beginning of the universe until now the speed of light has slowed some. Chances are they were just seeing light that has passed through some stellar cloud or something, give them a little time to figure it out.

That is interesting. I've heard theories that in alternate universes speed of light could be different, but what would be the effect on our universe if light is actually slowing down?

The speed of light is not a constant.

Then what is 299792458 m/s?

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Originally posted by ThunderChunky:
That is interesting. I've heard theories that in alternate universes speed of light could be different, but what would be the effect on our universe if light is actually slowing down?

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Keep in mind that the numbers crunched by the star geeks are astronomical (sorry for the pun). We're talking over millions or billions of years the speed of light may have slowed down a few miles a second, its not like it dropped to half or something like that.

They actually thought that over time light particles have became 'lazy' and therefore this implys that the particles were atually breaking apart, slowing the overall speed of light.

Einstein's theory holds that if an observer moves at a uniform speed, no matter how fast or in what direction, the laws of physics and the speed of light are always the same. For example, if you stand still and drop a coin, it will fall straight down. Similarly, if you drop a coin inside a car while you're driving down the freeway at a steady speed, it will also fall straight down.

However, recent theories attempting to combine gravity and particle physics suggest that relativity might not always apply; changes in space and time may occur that could not be measured easily on Earth.

We cannot be absolutely certain at this point in time whether relativity will hold. We will have to wait untill after the experiment is conducted.



[This message has been edited by Dr Know (edited 08-25-2002).]

yeh, i thought it was a fairly well known fact that the speed of light changes some in certain conditions..and there havnt been THAT many tests on teh speed of light has there? also, maybe in 150 years time einsteins theories may be proven wrong when technology and thought progresses..do instantly dismiss the fact that tests have shown light slowing down is really quite stupid isnt it?

It's an interesting topic. I think that we should give it a chance. Relativity is just a theory, even if it's never been proven wrong before. It'd piss off a lot of people if the speed of light in vacuum was variable, though. Is it possible that it was slowed by another kind of radiation that we can't detect? Maybe this ties in with the dark matter bit.

when speaking of the speed of light, one must differentiate between the former and the constant c. c remains the same everywhere everywhen whatever as it is the speed of light *in a vacuum*. In conditions very different from a vacuum, such as on Earth, the speed at which light travels can be slightly lower. Light goes through water at about .75c, and it slows by a factor of about 2.54 in diamond. Photons moving through a Bose-Einstein condensate can be even slower; one particular lab, using a cloud of sodium atoms cooled to nearly 0 K slowed a laser pulse by a factor of 14, if i remember correctly. Just thought you all should know.

As you could tell I didn't have a clue anout what they were on about, but you've helped to clear it up a lot, I actualy thought that it had very different findings and conotations,
so thank you,

Dopeman: I believe they stopped light, not only slowed it down (as can be seen with a quick search on Google for 'scientists stop light')

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Originally posted by xenosss:
Dopeman: I believe they stopped light, not only slowed it down (as can be seen with a quick search on Google for 'scientists stop light')

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Damn! I was just about to mention that.

Interesting, though [I don't think], it's exactly what it sounds like.

Most things involving light and such sooner or later ends up twisting your head.

Though if you make it through it it is wonderful stuff.

[Anyone who has had anything more than just freshman college physics - for non-science majors - knows what I mean. The couple of weeks spent on relativity when I was at Cal [Berkeley] gave me headaches and I had trouble sleeping, just trying to get a grasp on some sort of foundation. Once I finally got a grasp on things I was totally absorbed. Chromodynamics even more so; though here I still find myself caught in it's rip tide].

I just thought of this, but arnt light particles still particles? And if they are, dont they still get affected by gravity? What if they are just being pulled, or slowed down by some gravitational force?

The problem is that light is both a particle and a wave depending on the situation. I agree with you Meta, first trying to grasp everything about light is confusing.

I forget who thought of it, but you're right: gravity does affect light. I don't think it slows it down (or enough for us to know) but it does pull on it. If you spread out two perfectly reflecting mirrors over a large distance and the two mirrors are parallel to each other you'd see when you shone a laser against one it wouldn't just bounce back and forth but go from the top to the bottom, because gravity is pulling it down.

Light isn't slowed by a factor of 14 in Einstien-Bose condencete, if I remember the article correctly it is actualy 14 meters per second.

Gravity can be seen bending light during a solar eclipse. The gravitational field of the sun bends the light from stars just slightly putting them out of place just a hair closer to the sun.

Gravity can also be seen acting on light in black holes, where the gravity is so strong that light can not escape.

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If you spread out two perfectly reflecting mirrors over a large distance and the two mirrors are parallel to each other you'd see when you shone a laser against one it wouldn't just bounce back and forth but go from the top to the bottom, because gravity is pulling it down.

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It depends upon the gravity factor. The only reason light cannot escape a blackhole is because of the extreme gravitational affects.

We must be mindful of escape velocity (The minimum velocity that a body must attain to escape a gravitational field completely.)

Well, there is always gravity and it is always affecting you. Whether or not the affects are noticeable is another story. Since in space gravity is almost non-existant the effects would be hard to see but they would be there.

How is gravity nearly non-existent in space? Look at the mass of earth, figure its inertia, then look at its distance from the sun. How much force does it take to keep something with that much energy in orbit? Quite a bit. Gravity in earth orbit is only about 15% weaker than on the surface.

Okay okay... I nitpick, you nitpick.

A stationary object will remain relatively stationary in space. It will move very slowly because there is gravity. I didn't mean it as there isn't a lot of gravity, just that the effect is very weak. (By space I am talking about outside the gravitational pull of any object)

I suppose that it comes down t the definition of "vacuum". If it means "a space void of all matter and force," then c is a constant. If it's only the absense of matter, then gravity could affect it. Unless, of course, gravitons exist, in which case they'd get flushed out with the rest of the particles and it would no longer matter which definition you used.

yes things do affect light. maybe since its in wavelengths its "slowing down" because of the doppler affect. They have slowed light down by passing it throuhg some substance that was black(i remeber hearing it on quarks and quarks[a CBC radio program]). the speed of light may also depend on the size of the universe and since our universe is expanding maybe that might have somehting to do with it?

[This message has been edited by ardene (edited 09-08-2002).]

Just a few comments. In regards to the experiments in which they stopped light, it seems rather they were able to encode those properties of the initial lightwave in the condensate and then later able to excite it in such a way as to release that same energy at a later point in time, so it was more of a light recording at the quantum level.

Also about the orbits of large objects of matter and their gravitational effects, one must remember that they are in fact moving in a straight line however gravity enforces the orbital view in three dimensional space.

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Originally posted by evolove:
I Australian scientists thought they had found evidence for the speed of light slowing down

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The article you're thinking of is in Australian New Scientist. Unfortunately, they don't put their cover stories on the website, you gotta buy the magazine. If anyone can get it, its the cover story on issue 2359, 7 September 2002.

They think that all sorts of constants of the universe are changing, but all by amazingly tiny fractions. It's not like light is ever going to stop like this. However, as to why, they have absolutely no idea.

i dunno,
i heard that it wos true cos the universe is slowing down in its rate of expansion and because everything else is relative it is slowing down too.

If everything were slowing down, we would still percieve the light to travel the same speed.

I read a brief history of time after a shroom trip. Physics still scares me.

Matter is energy, which causes gravity, which bends space, which is also time.

Am I alone in finding that worrying?

Not realy. It is what it is.

I am fairly sure that the speed of light does change, my reason for this are as follows:

1.Since light exist as a partical, photon, it should be affected by gravity.
2.Since light is created when an electron move down an enegy level and emits a photon light must acualy be stationary for a breif peroid of time.
3. Since light exist as a wave it must be speed up or slowed down as it bumps into other forms of matter.
4. If nothing can escape a black hole not even light than the light must be suck at a faster speed than ity can escape.

When those are GW 4 therorie of light, they make sence to me but im most likely wrong.

CTR

All of this discussion regarding C is all well and good...if you want to continue thinking "inside the box" (God! I hate that expression!) That is to say, Einstein was right... But... Currently there are also well respected theories that pose some what of a challenge to the idea that light has a constant speed. These theories deal with the nature of time...or, more to the point, the existence of time. Does time exist? If so, is it linear? If time does not exist, obviously speed, or velocity of a moving object, can not exist either... So... good bye C...
As a matter of fact, if you remove the "time" constant from the equation, discrepencies between Newtonian physics and quantum physics are reconciled... Removing the time constant unifies both branches of physics. Interesting...

I haven't studied physics since Year 10, so please excuse my incomprehension and ignorance.

About the theory that time slows down for an object as it approaches the speed of light, eventually time will stand still as it moves at lightspeed

As far as I'm aware, speed is the rate of change of displacement with regard to time.

If time stands still for an object moving at lightspeed, then how can its speed be measured, since speed relies on time?

Just some theory for people to play with, but the faster things move the slower time moves. It is my theory at the speed of light time stops. It wouldnt make sence to me that light would slow down after all a light particle is infinite. Maybe ,again just a theory all these particles in the clouds are infact little dust mirrors so that the light is traveling relativly straight but reflecting off of millions of mirrors causing it to take longer to get from point a to b, but only because its not a complete strait line. Or maybe I'm a dumbass, I dont know never studied it!

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Originally posted by nastradamnus:
It is my theory at the speed of light time stops.

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It's not just your theory; it's Einstein�s, too.

Actually it's one of the reasons nothing with any mass at all can achieve the speed of light. You can get closer and closer, the more energy you pour into the system, but never reach it - no matter the energy input.

It one of them thar Asymptote thingies.

It's the same with length and mass too. That is, they're both Asymptotes: as you approach C length and mass increase until, at C you have infinite mass and infinite length. Which is meaningless.

Better yet, it's undefined, which is exactly what is going on in the equations.

In the equations you have a situation where these properties [time, mass & length] are calculated by what boils down to a number divided by an ever decreasing number, as the bottom number approaches zero the value for length [or mass, etc.] increases. At C the bottom number is zero.

And you know you cannot divide by zero: it is said to be undefined.

Thank you! I dont have the time or money to go to collage so I spend my time reading the internet. It has more to offer than any collage and I'm working on my knowledge and most people if they saw my mistake would just attack me thank you for just showing me "the way"!

[This message has been edited by nastradamnus (edited 10-17-2002).]

Flaming, especially for an honest mistake, is not my style.

It's a rare occasion that I flame at all:

I'll do it, sometimes, as a response to being attacked first.

More often, though, I will do it to someone with an unreasonable over inflated sense of themselves and their input; especially when they do make a mistake and present it as an indisputable 'fact'.


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.It also depends where in the bipolar cycle I'm at ;-)

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Originally posted by ThetaReactor:
Relativity is just a theory, even if it's never been proven wrong before.

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*Sigh*

Lysander, if you wish to comment on my posts, do so. Save your condescension for the kewls in Bad Ideas.

If you've travelled at light speed and have a story to tell, please enlighten us.