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Light Traveling at 38 Miles an Hour
You can't let so many people be misinformed. Please let them know:
The speed of light IN A VACUUM is the constant c.
Science has been able to slow light down for centuries by making it travel through a different medium. The speed of light in air is less than c. The speed of light in water or glass or plastic is less than c. This is what makes lenses work. (check your encyclopedia for more information)
The reason this is a breakthrough is simply because they've been able to slow light down to a much lower speed than anyone else has ever been able to do. They have not changed c, the speed of light in a vacuum. The beam of light is only slowed down when it's in the condensate. Once it leaves the condensate and is travelling through air again, it returns to a speed of 186,000 miles per second. This does not contradict any law of physics. "
Heh. If you could slow it down even more, I'll bet wou could create some NEATO visual effects.
It goes to a page that says "this page has been redirect blah blah. Please go to XXX", where XXX is the same URL I just arrived at.
It's broken from the front of nytimes too. Any hints? Sounds like an interesting article.
use cypherpunks/cypherpunks
If light can be slowed to a certain speed, does that also mean it's -possible- to speed it up?
I've never really believed that the "maximum speed" of anything is the speed of light. It just seems odd placing a limit on something that we don't really know everything about.
*Disclaimer, I know very little about physics, etc.. so don't flame me for being wrong.
he he, so says Anonymous Coward...
have you forgotten?
:)
username: cypherpunks
password: cypherpunks
can't be bother to get an account
cheers
dave
YUP, once again the brave Danes show off their Inheritance...
:)
They didn't conquer the world in the Viking Age, but 20-century physics.. Does Niels Bohr ring a bell ??
About time Denmark gets another nobel prize. This should do it
Oh well, you have one try to see if you can guess what country I'm from....
--pug
Absolutely nothing. Light slows as it passes through any medium. If what I remember from my optics class is correct, this is because it is constantly being absorbed and re-emmited by the electrons of the medium. What they've done is create a special state of matter that does this much slower than normal molecules. You're not going to cheat relativity with this.
People - the light is only slowed down while it's in the Bose-Einstein condensate. Once it enters the air, it speeds right back up. That's exactly how it works if you replace "Bose-Einstein condensate" with "glass" or "water" or "plastic".
... a more accurate but less flashy headline would have been "In a Major Breakthrough, Danish Physicist Reduces the Speed of Light to One Much Slower Than Other Physicists Have Reduced it to in the Past"
Yes, if you shine a beam of light through glass, it will be slowed down - it travels slower than 186,000 miles per second while in the glass.
Of course, it only gets slowed down a little - the reason this is a breakthrough is the magnitude to which the light is slowed down.
The headline is "In a Major Breakthrough, Danish Physicist Slows the Speed of Light"
-Mike Schiraldi
-who knows what he's talking about
..than the speed of light!
for backward compatibilty with older slower 386s at this point. soon though it will be slow enough to make even older computers seem fast.
:)
At the top of this very same page the commercial banner of an ISP shouted: "The only thing
slowing us down is the speed of light" (http://adfu.blockstackers.com/servfu.pl?i,64)
They're probably scared to death of this guy!
No, the speed limit is absolute, not relative to the medium. You cannot exceeed the speed of light in a vacuum, but you can exceed the speed of light in a given medium. If you were in the weird stuff they are playing with, you could exceed the speed of light in that medium.
There are examples of particles exceeding the speed of light in a given medium, water for example. This produces a kind of optical shock wave called Cherenkov (spelling?) radiation - thus the blue glow in nuclear reactors. Stray radioactive particles can easily exceed the speed of light in water.
-josh
I sooooo agree with this. Adjusting to light is the hardest thing for me to do in the morning....
I thought the most interesting thing about the article was the medium though which she transmitted her beam of light. Within 50e-9 of absolute zero?? And practicle applications were only going to be about 10 years away?? That'll be interesting to see happen.
Uncertinty Principle jokes may become commonplace:
Speed of light is always a constant, regardless
of the medium. What's happening here is that
when light beams hit the atoms in the medium,
the beams get absorbed; then there is a short delay
before the light beam is re-emmitted again. However,
the speed of the light beams between collisions
is still equal to `c'.
A 38 mph value for C would lead to some interesting effects to people travelling, it would also render nuclear weapons rather useless.
And how, exactly, would slow light make nuclear weapons useless?
The slowdown is of course caused by a high concentrate of magic energy - everyone who has read the Discworld novels would know that light move slow in areas with much magic... :-)
I don't believe in the theorey of gravity...
:)
go back to school. this is not star trek. set your phaser on 'dipshit'.
Your country has a great wealth. But why do you allow child pornography?
Microsoft announces Windows 2000 will be released faster than light - If they can slow it down just a bit more
Does this mean the speed of light is not a constant?
What effect does this have on E=mc^2?
Now, as to your specific comments: even in a gravitational field, the local speed of light as measured by any inertial (= free fall) observer is always the same.
The speed of light is not really well-defined in other cases; it depends on what coordinate system you choose, and because there are no global inertial frames in a curved spacetime, there isn't any "best" way of choosing one.
I don't think I'd say that "if you could negate the force of gravity [...] you should see an increase in the speed of light". The speed of light (as that quantity is defined above) is never going to be anything other than 2.997*10^8 m/s^2, no matter what the gravitational field is.
The speed of light also does represent a maximum speed limit in that nothing can travel between two points in a particular spacetime faster than a light ray could travel between those same two points.
Yes, in a round about sort of way.
That is what relitivity is all about. You see, you can always accelerate. However, it only appears to you that you are accelerating. To everyone else, you are not speeding up. Everytime you speed up you are in theory gaining enerygy. But, as you gain energy, time for you is slowing down. So, if you are clocking yourself going
60.0000 mph. You are in fact going 59.999999 mph.
You don't really notice this until you get closer
to the speed of light (or are on the fringe of a
large gravity field, they are beginning to notice this in hi-earth orbit satalites). So, when you are going 99.995% of the speed of light, it will appear to you to be going the speed of light. When you are going 99.996%, you will appear to yourself to be going 2x the speed of light. But, you will still only be going 99.996% of the speed of light. As you get closer, 99.99999% of the speed of light, would mean you appear to be going (to you only) 1000X the speed of light. In theory, you could go from sun to sun in what would appear to you to be a few hours. But, to everyone else, you will still take 18 years to get to alpha centuri.
Everything you do while traveling would still appear to be normal. And the light going from you to your shipmates would in some cases appear to be going faster than the speed of light. However, if you were to look out your ship (or VW Bug, depending on your opinion of LSD), the light of the stars would appear to be streamed.
(Disclaimer, please forgive my liberal use of math, this isn't a damn thesis. But everything should still be sound, in theory)
Anonymous because I don't need another password.
Andy Robertson
robertson@rocketmail.com
The speed of light in a medium is given by its index of refraction, which is the ratio of its speed in vacuum to its speed in the medium (and as its name implies, governs the angle through which a light ray refracts upon entring the medium). For air it's 1.00029 and for water its 1.333.. so in water, light travels 1/3 slower than in vacuum.
I seem to remember IBM having a press release some years back (1993c) regarding an experiment in artificially entangled particles. I tried looking but can't seem to find it now.
They move as little as possible (will be in a ground state), but there will always be quantum uncertainty.
Hey, I've been to Copenhagen.. Not much to do there besides slow light down.. ;) ;)
If the refractive index is so high, wouldn't it be possible to send a beam of light into the condensate and trap it there permanently? Could you use this to store energy, HUGE amounts of energy?
This is of course assuming that there is no loss within the condensate. Does the condensate absorb the light or simly reflect most of it? The article didn't make it clear and it seems that it's extrememly low temperature indicates that energy isn't absorbed.
This is cool.
The picture given by the original post is roughly that presented by Richard Feynman in his excellent book Quantum Electrodynamics. So, while IANAP, I am very interested in why you would say it has been "turned upside down by the quantum theory".
Second, enulsions are a chemical phenomenon, I don't see how thewy would introduce any distinction at the Planck level.
--Uche
Light slows down in any medium. That's why a prism and telescope works. I believe relativity predicts this. The speed of light is constant within a medium. Always has been always will.
No effect. That "c" in E=mc^2 is defined as
the "speed of light in a vacuum"... thus it
has no bearing on the speed of light travelling
through a super-cooled substance-- or anything
else for that matter.
we're talkin bout a po-lice osifer.
A black hole bends time and space making a "downhill" and you can practicly arive at a spot faster then a particle moving at the speed of C.
So, "you" can move faster than light.
//Commie
Cool. Now if you can get light to move faster than 38mph through this medium, you can build up a nifty "light shockwave"!
It's called Total Internal Reflection and you can do it with a regular glass or plastic lens. That's why at certain angles it looks like a mirror.. like:
/\
/ \ (>
/____\
Where that thing on the right is your eye.. The bottom of the prism appears to have a mirror glued to it. I don't remember why this happens, but i'm sure you can look it up if you're really that interested.
Also, sending a beam of light into the BEC will warm it up.. then it won't slow down light any more. The reason light moves slower in the medium is because this happens:
---light---- atom atom
Light moves at c and gets absorbed by atom
-----atom atom
Atom waits a little bit and chews on the light
atom---- atom
Atom spits it back out in the other direction and the light once again travels at c
It's the pauses that make the speed of light appear to be slower. The more atoms, the slower light moves. The BEC has a lot of matter packed closely together, so the light spends a lot of time inside the atoms' "digestive tract"
Anyway, all this action heats things up. If you want to store lots of energy in a BEC, you're going to waste much much much more energy keeping it cool.
-Mike Schiraldi
-who is pretty sure he didn't say anything glaringly incorrect
It's called Total Internal Reflection and you can do it with a regular glass or plastic lens. That's why at certain angles it looks like a mirror.. like:
/\
/\(>
/____\
Where that thing on the right is your eye.. The bottom of the prism appears to have a mirror glued to it. I don't remember why this happens, but i'm sure you can look it up if you're really that interested.
Also, sending a beam of light into the BEC will warm it up.. then it won't slow down light any more. The reason light moves slower in the medium is because this happens:
---light----atomatom
Light moves at c and gets absorbed by atom
-----atomatom
Atom waits a little bit and chews on the light
atom---- atom
Atom spits it back out in the other direction and the light once again travels at c
It's the pauses that make the speed of light appear to be slower. The more atoms, the slower light moves. The BEC has a lot of matter packed closely together, so the light spends a lot of time inside the atoms' "digestive tract"
Anyway, all this action heats things up. If you want to store lots of energy in a BEC, you're going to waste much much much more energy keeping it cool.
-Mike Schiraldi
-who is pretty sure he didn't say anything glaringly incorrect
It's cold, but there wouldn't be enough of it to actually cause any damage to anything. The hard part is maintaining a BEC in a portable apparatus.
Umm, no. Light travles 1/1.333 == 3/4s the speed of light in air while in water. This does not mean 3/4s slower.
So Bill Clinton can say his limo travels faster than the speed of light, or something?
If you have to give something, it isn't free.
What if I keep pouring light into this medium? Does it accumulate or "pile up" somehow? If I stop sending in new light, presumably light continues to emerge for awhile (light that was busy crawling though the medium at 38 miles/hour). If I could take this technique to the theoretial extreme and essentially "suspend" light in my medium, have I not created a light capacitor? Can I sit my little light capacitor out in the sun for a few hours and capture sunlight for later use?
>Your country has a great wealth. But why do you allow child pornography?
What? This is a troll, I hope.
The minimum legal age for making pornography is 18 -- that's when you become 'myndig' (I don't know the english word. It's when you become legally responsible for yourself, your signature becomes valid, you get to vote, &c.)
Making and selling child pornography is very illegal and doing so will result in a long, and hopefully unpleasant, stay in jail.
With light slowed to these low speeds,
one could create a light buffer loop device to
achieve massive storage.
Optical data goes in one end of a long lossless
light path(big box/panel with with mirrored walls, and filled with slow light medium.
When light comes out on other end, it is read and
recirculated.
What do you mean by Einstein causality? If you mean some aspect of relativity theory, then there is no body of evidence currently disputing it. Or did you mean Einstein's idea on EPR-type effects in quantum mechanics (some of which are tied up with "causality" under some defintions of that term).
No.
Yes, gravity slows down light. So as the universe expands, the speed of light increases. As things get farther apart, distance in light-years becomes shorter. Weird, huh?
The higher the index of refraction, the smaller
the lens. Now your coke bottle glasses can become very small. Also if you can slow the light down in the xray or gama ray range (I don't know if you can cause I couldn't read the article) you can make good xray mirrors -- something we don't have now. Could help with xray lasers? or xray imaging? Something we can't do well now. Even so, you can make really good visible mirrors and lenses
I would like to see how an inductor or capacitor works in there!!! Might have some uses in E&M.
I just want to see what happens if they could slow it down to zero, could you collect a bucket of *stuff* that contained light going 0mph?
If the vacuum is actually a gas of virtual particles, doesn't that mean that the virtual particles are slowing down light, and that the "real" speed of light is somewhat greater than C?
Okay, I'm too lame to take the time to register /. So, what medium is the light passing
on the NYT site and too lame to even register
on
through which is making it move so slowly, and
is there any chance that sending a beam of
electrons into this would give a nice source of
Cerenkov radiation? Could there be useful
applications for this? Could it lead to cheap
table-top demonstrations of Cerenkov radiation?
There are substances (metals for instance) that have index of refractions less than one. Since the speed of light in a medium is c/n this means that their speed in that medium is greater than 3e8. If you don't believe me look it up in CRC Handbook of Chemistry and Physics. I also believe that water has an index of refraction that is less than one for certain frequencies in the infrared range.
Anyway, this does not break the laws of physics because the phase velocity can be greater than c, but the group velocity can't -- thus we can't send information at speeds greater than c.
Just an interesting side note.
Hmm... reminds me of the mercury delay lines used in some old old computers.
if you believe the tachyon theories...
In a single inertial frame it is. Sure, you can get time dilation between different frames (and length contraction intervenes to keep the speed of light constant), or gravitational time dilation between different locations, but the original statements stand.
As to quantum entanglement.. causality still holds in the sense that effects cannot precede causes, nor can you communicate information faster-than-light. There are instantaneous correlations between observables (see the FAQ on the EPR paradox).
Not even quite that. c is still a constant, vacuum or not. It is just the absorbation / reflection that slows things down and on its way from one, lets say, partical to another a photon travels with a speed of c, as will the newly created one and so on and so on.
... what a pity, how fast Monica would be gone than 8)
For faster than light, well, no problem and a well known effect too. It is just one cannot transport any *information* faster than with c
Yeah, and what happens if you lick a Bose-Einstein Condensate? We need to think about this now, before our kids are playing with these things in high school physics courses.
I know something which can run faster than C.
It's called assembler!!!
This is a very old idea! Of course for huge storage you actually want light going at full speed, not to slow it down. I forget who first proposed this, but the idea was to bounce lasers off mirrors on the moon..
"Black Holes and Time Warps:Einstein's Outrageous Legacy" by Kip Thorne. There is good background material here explaining various weirdnesses
surrounding special cases of supralight velocities, time dilations, Black Hole radiation, etc.
ICYDK, Kip Thorne
is a close friend and associate of Stephen Hawking and has worked with him on much of his black hole research, so this pretty much about as straight-from-the-source as you're going to get.
There are formulae/diagrams/math,etc. in here, placing it a step or two above BHOT in complexity
FYI.
Not anti-gravity, just a device that creates gravity. Specifically, gravity that repels, which doesn't occur in the universe, for some reason...
You missed it. You never pass the speed of light.
But, as time for you slows down. One second for you is three seconds for your base. So, in what you would have traveled in three seconds at the speed of like, went by in one second for you. Or three times the speed of light. But, you are never actually traveling above the speed of light.
By your logic, speed would have slowed down for earth as much as it would have for you. Hence, everything remains the same.
And they could have saved all that effort by running a beam of light through a computer running windows.
Sheesh.
You've addressed my question. I want to know why light goes slower through substances. It is because the photon interacts with atoms (sending electons to more energetic states). I'm assuming that photons are absorbed, then re-emitted (even in transparent substances). And that these actions essentially take some time. Or perhaps it is like a pinball in the bumpers; the photons spend time bouncing between atoms, before finally emerging from the substance (thus travelling a longer distance, on the microscopic scale, as you indicated).
The photons are always travelling at c, but they are deflected repeatedly (when not in a vacuum), thus slowing their effective progress. Different frequencies are deflected differently on the atomic scale, which is seen as a spectrum on the macro scale. Is this (roughly) correct?
PS. The previous comment was less than constructive.
this means that I've achieved FTL speeds just on my bike wheezing down from Mt. Tamalpais, that is;)
At absoloute zero, all elements should (has been mathematically proven) be frozen, except helium, which will still be in a liquid state.
Wouldn't such a material have an astronomical (relatively) refractive index?
Thin lenses, very small prisms.
It does have practical purpose after all?
To enhance/clarify: particles moving in a medium can move faster than (THE SPEED OF LIGHT IN THAT MEDIUM). They can't move faster than c (~= 3e8m/s).
If particles enter a medium faster than (the speed of light in that medium), they are slowed down to "acceptable" speeds. The kinetic energy dumped by the slowdown goes into heating the medium (obvoiusly) and into Cherenkov (sp?) radiation, as mentioned in other posts.
"Time going slower" might be one way of looking at it, but I've never seen it described that way.
:-)
Here's the really cool thing. Forget for a minute that c is the speed of light. Let's just say that c is some kind of "absolute speed limit." If you do your E&M and SR right (again, ignoring that SR CAME from studying light, Einstein could have derived his equations in other ways), you can see that in vacuum, the only way to get electric and magnetic waves to propagate in a self-sustaining interaction is if thay move at that magic "speed limit," c. THAT'S why light moves as the "speed limit," c.
Now, consider that when light moves through a medium, all of a sudden, there's other electric (and magnetic) fields around it! In that case, the "self-sustaining speed" isn't the "speed limit" (c) anymore, it's something else. In fact, you can prove that it's always less than c for any physical (=realistic) charge configuration in the medium.
Of course, interaction with the EM field of the medium IS "scattering," so you're right after all
How about for syncronisation in Fibre/Optical chips. Got 2 signals with a set difference, need them to be syncronised? fine. Just use this. Sort of a FIFO buffer for light. *grin*
That is a superior attitude. There is much we Americans can learn from you Danes.
If we were hypothetically able to cool an atom down to the point where its momentum were absolutely and ideally zero, then its position would become infinitely indeterminate. It would be anywhere/everywhere in the universe at once.
It reminds me of the time I gained fleeting access to universal knowledge when I created a temporary mental stillpoint though meditation.
Well, can we apply Heisenberg Uncertainty to photons? If their velocity becomes near zero, their location becomes uncertain. So you'd end up with a blob of photons. Or if they're waves...um.. waves with uncertain peaks and valleys? I'd better stick with "a bucket of dark light". (dark because not shining on anything)
Where there's gravity & mass, space is denser.
My SO's 2 eldest (7 and 9 years) are constantly looking at the naked diagrams in their picture dictionnary. It got me thinking : why is there no erotica for children? Why are they forced to "sneak" their sexual imagerie? It's not as if they don't need the "education". It's not as if they don't have a sex life (no where near as active as ours, though).
The adult porn is totaly inappropriate. It is gross to most adults, even.
I remember as a child looking and searching for pictures of bras, panties in catalogues. *anything*
make the blue glow in nuclear plant.Electron runs faster than the *local* speed of light.
(Or was it neutrons?)
I found it ironic that the bannder ad for /. at the time I read this article was for INTERNAP - "The only thing slowing us down is the speed of light." Hmmmmm.
c is the speed of light IN A VACUUM. No body has (or can according to physics) change that constant. The speed of light in this supercooled Bose-Einstein condensate has no bearing on the energy release by matter conversion such as in nuclear weapons, genius.
Furthermore, techincal terminology has nothing to do with whether or not the field is pseudoscientific hogwash. The science is what matters.
Note: So I don't have to put In theory in front of every single thing I put in this I'm going to state it once here. IN THEORY.
Ok, *if* you could get up to the speed of light many funky things would happen. For one, in the case of light itself it takes it zero time for it to get anywhere, but only because it's really not going anywhere. In it's own refrence frame its already there, or rather everywhere. Very strange.. but that's relativity for you.
-Rosenrantz rglasnap@nmt.edu
Well it is actually possible to go faster than the speed of light if you have imaginary mass or imaginary length.
-Rosencrantz rglasnap@nmt.edu
I don't think it's so much the slowing of light that's beneficial -- I think it's being able to use the 2nd laser to control whether the 1st laser gets through or not, or however that works. The benefit is being able to turn light beams off and on by shining light beams at them. This process can be miniaturized and applied to disgustingly fast circuitry.
From what I can tell, the speed of the light travelling through the BEC is dependent on the temperature of the BEC. Now, a few billionths of a degree above 0K is really damn cold. It take an enormous amount of energy to get something that cold (that's why they call it high energy physics!).
I can see using the properties that we learn elsewhere, but don't expect to ever see slow light yourslef...:)
The way I understand it is that mass increases as speed approaches c. If you actually went 100% of the speed of light, your mass would be INFINITE. But since acceleration takes force, it would be harder and harder to apply force to get you up to the speed of light. Eventually, just short of c, it would be impossible to get you going any faster.
woof :)
How would slow light make waking up in the morning easier?
You aren't going to be able to control the speed of the sun's light.
You could set up lights in your room to come on at a set time in the morning, (if it were still dark outside). But that would not benefit from slow light either.. You would have to control the power going to the lighting fixture, not the speed at which the light eminating from the fixture would reach you.
-=e
Posted by NeuroNomad:
For years we have tried to come up with a way to travel faster than the speed of light, hehehe, could not do that so now we have just decided to slow light down. They even are going to try to slow it down slow enough that a turtle could out walk a beam of light.
That is funny.
Posted by Tester TW:
Here's the URL
http://www.nature.com/cover/cover0218.html
Posted by tdibble:
No, the first poster was right. They cooled the tramsmitting medium such that the time between absorbsion/emmission was dramatically heightened. I look forward to seeing a video of this, personally.
This isn't a hard fact. There is a fringe branch of physics which is looking into *increasing* the "c" constant. The trick here is that a vacuum is devoid of matter, but not of energy ond forces; it is this which constrains the speed of light, and modifying the constraints may allow light to travel faster than the cvac.
In other words, the finality of the maximal speed of light is accepted generally, but not completely, and there is some evidence in favor of the vocal few.
Posted by skitzo:
hmmm...that's very cool.
Posted by Bill, the Galactic Hero:
The phase velocity is equal to the optical frequency divided by the magnitude of the wave vector (i.e., if optical freq. = omega & wave vector = k, vphase = omega/|k|. Remember omega and k from exp[ i ( omega t - k.r) ], the active ingredient in a wavefunction).
The group velocity is equal to the derivative of the optical frequency with respect to the magnitude of the wave vector.
Where the relationship between the optical frequency and the wave vector's magnitude isn't strictly linear, that's where the phase velocity and the group velocity differ.
Posted by AnnoyingMouseCoward:
There is a little problem - it's called zero point energy. This permeates all of space/time, and was predicted by the Dutch physicist Hendrik Casimir in 1948. It's existence has been experimentaly proven ( refer to "Physical Review Letters, vol 78, p 5 ") by Dr Lamoreaux at the Los Alamos labs back in 1997.
Zero point energy prevents any physical particle from ever being completly still. It's the residual energy left over from the Big-Bang. Acording to the American physicist Richard Fenyman, the ZPE content of a volume the size of a coffee cup would be sufficient to completly vaporise the Earths oceans.
ZPE manifests as the constant production of particle/anti-particle pairs, the duration of their existence being inversely proportional to their energy ( in accordance with the Heisenberg uncertainty principle ). This is the source of Hawkins radiation around black-holes and the main reason why cyrogenic preservation is limited to a few thousand years, even if you could get to absolute zero ( which the third law of thermodynamics says you can't ).
Turing used cycling mercury delay lines on his first computer. Anyone want to calculate how much this thing can store as a cycling optical signal? Include an overhead for error correction...
--
Xenu loves you!
unfortunately, this article requires a subscription.
Does anyone have a url of a version of this which is freely viewed?
-herb
your mom!
Now we can drive at light speed or faster. That should cut down on the commute. ;>
Weird that I first heard about her on slashdot.
It should tell something, either about me or about the Danish media.
Can the Flash outrun Superman?
So how exactly does the medium slow down light? Do the photons bounce off the molecules? If so, it sounds to me like light isn't really slowing down, but rather taking a longer path.
--
Timur "too sexy for my code" Tabi, timur@tabi.org, http://www.tabi.org
To a decent approximation, the speed of light (measured locally) is not affected by gravitational fields - the only thing that changes is the apparant frequency of the light as seen by different observers (known as gravitational redshift).
As others have noted, the speed of light in a non-vacuum medium is slower by a ratio known as the refractive index, which is less than 2.5 for most materials (I think diamond is 2.42 or something) and is exactly 1 in a vacuum. So, the real news story here is the creation of a material with a *huge* refractive index (which is really neat).
Depending on how you manipulate the equations, it *is* possible to have a refractive index less than 1 (and therefore a "speed of light" faster than in vacuum). These conditions can occur in an ionized gas, such as the layers of our atmosphere which bounce radio signals around the globe. However, it also turns out that you can't transmit any information through this medium faster than in vacuum, so it's really just a mathematical curiosity.
>What effect does this have on E=mc^2?
-----BEGIN RANT BLOCK-----
version 2.10a
None whatsoever; "E=mc^2" will continue to be a widely-parroted simplification of the more general definition of the total energy of a particle, (E^2) = (m0c^2)^2 + (pc)^2, where m0 is the particle's rest mass and p is its momentum, and c is the speed of light _in vacuum_ (which hasn't changed). This news story is about some unique optical properties of a new type of matter, but it doesn't affect electromagnetism or relativity theories.
E=mc^2 may have been a big deal back when the "wireless" and the "horseless carriage" were on the top of every geek's Christmas wish-list, but these days it's just a routine part of physics like Ohm's law (V=IR) is in electronics. It's not a big deal. The rest of Einstein's work is much more interesting (general relativity, stimulated emission (lasers), the photoelectric effect, etc).
"E=mc^2" may look good on a T-shirt, but apart from that there's little reason why this particular Thought McNugget deserves to be so widely quoted when so much more of the really interesting physics is completely ignored.
By the way, nuclear fission was observed in the lab by people like Otto Hahn, without the need for "E=mc^2" to explain where the energy came from. Nuclear bombs are just a matter of banging rocks together, once you have the right rocks - who cares if the total mass of the bomb fragments is slightly less after the blast? Your city still ends up as kitty litter thanks to the binding energy in the nucleus.
------END RANT BLOCK------
Oh dear... I'm confused. I thought speed of light was a constant ( c )? Or is that speed of light in a vaccuum? So what's the speed of light in vaccuum compared to the speed of light in air or water, then?
Feel free to flame away, I have absolutely no clue what I'm talking about and would appreciate it if someone could explain it in armchair terms.
At least now I know what computer illiterates feel like when I talk to them.
(it ain't my fault, my physics teacher was too attractive for 16-year-old boys to actually pay attention to what she *said*
Andrew Oakley - www.aoakley.com
For some strange reason too many people don't see the difference between
1. Raping children, recording it, trying to squeese out as much money as possible.
2. Beeing a pedophile and arousing yourself with sexual images of children, not produced using real children.
For me, people can have whatever strange sexual ideas they like, as long as they don't hurt people by, say, raping them.
So, what should be outlawed is of course not 'child porn' (wich can, for example, be drawn or computer animated) but raping or otherwise hurting children.
(Unlike here in Sweden where we have a new law since 1999 outlawing even the owning of any kind of child porn. Oh, they are so stupid! And over half the 'liberal' party voted for it (twice) and the largest 'conservative' voted against it. Just shows (again) that all they care of is votes/money/power and that ideologies and morals definetly comes in second place. Sigh.)
Einstein's 1905 work has been confirmed in many different contexts, from radio transmission to particle decay. The ironic thing about your statement is that physicists probably know more about light than any other phenomenon!
Any fun time dialation involved?
--
"Reactionaries must be deprived of the right to voice their opinions; only the people have that right." - Mao
I wonder what this means for fringe physics?
Like, if they get it going really slow, what's that mean for going faster than light?
-- haaz, playing Lead into Gold today..
-- haaz.
remember, indians a century ago put their ear on a railtrack so before they saw the train, they know if there was one or no (my english is not very good), they even were able to know the distance!
anyway, speed of sound is greater in steel that in air, as light speed is slower in water than vaccum, etc.
--
"Science will win because it works." - Stephen Hawking
Years ago a science fiction author called Bob Shaw
had a book predicated on a material called slow
glass. Basically it took light years to travel
through the medium, so you took a piece of glass
set it somewhere scenic for a year or two and then
hung it on your wall and enjoyed the view for
the same couple of years. A few more orders of
magnitude and we will be there..
-- Back to the shadows again...
I'm way out of my league in evaluating the use of slow light. So please, someone explain the benefit of slowing down light. It just seems a little weird to intentionally slow down the fastest known thing in the universe.
...and a monkey might shoot out my butt.
After reading about just how much work they went through to make a BEC (that's Bose-Enstien Condensate), they then suggest that this could be used for night vision goggles.
Does anyone else NOT want a substance at about a billionth of a degree kelvin near their head? This stuff makes liquid nitrogen look toasty by comparison.
BEC's have all kinds of "odd" properties that make them interesting, but I can't get excited about strapping one over my eyes. Call me silly, but that just strikes me as a Bad Idea.
If they can duplicate the same quantum states that allow this high index of refraction in something a little more stable, this could actually lead to something practical, but I'm not holding my breath.
Also of interest, someone used a BEC to create a coherent beam of matter. I don't remember the URL though.
--Mark
No, the actual wave packets, or photons, that carry the light are still travelling at 298,000 km/s (or whatever exact figure it is) it is just that they're being absorbed and reabsorbed. When a beam of light containing billions of these photons enters the condensate the condensate will absorb them and the atoms which then are excited by absorbing these photons re-emit them after a certain time. :-)
It isn't that difficult to comprehend unless you try and understand how they are abosrbed and re-emitted. THen it gets trickier to explain in normal words.
What about in the cold of space? Could this be used to trap solar energy? Space is near 0K and you would not need the energy requirements to maintain the low temp of the media. I see this as a very useful application of this technology.
pronoblem
I was thinking the same reading this article, if i remember correctly the book ended on a somwhat '84ish note, slow glass of different "speeds" (was'nt it calld retard or something) being used for surveillence and all
Somebody up there mentioned using BECs to make a kind of laser that shoots atoms instead of photons. Well, here's MIT's page on doing exactly that: ufn.ioc.ac.ru:8200/news/eng/1997/0397.html
\
...in car headlights. Sorry. Couldn't resist.
spawn_of_yog_sothoth
No, high energy physics is more usually used when talking about particle accelerators, etc. The energy requirements aren't huge - all you're doing is gently nudging a few billion atoms around with light.
Let's face it - you can't fully describe what happens to light in a transparent medium (of any considerable density) without looking at the quantum mechanics.
As a first approximation, what happens is that the light enters the material, is absorbed by an atom and then re-emitted after a tiny delay and in the same direction. It then gets absorbed by another atom, etc etc. The delay before being retransmitted is what causes the reduction in the speed of light.
Something similar to what you describe occurs in a translucent medium - here the photons are re-emitted in random directions (and after a longer delay), so they do indeed seem to bounce off the atoms.
Note that in a BEC, there's no such thing as "an atom", so the actual mechanism is almost certainly nasty enough to require a PhD to understand.
Light entering the medium gets held up in an optical "traffic jam" (not to be confused with "optical molasses"...), so a volume of BEC left in a beam laser light at the right angle and polarisation for a given time will contain more light than an equivalent volume of some other transparent medium. You cannot "suspend" light in a BEC because the BEC would have to be at absolute zero, and thus infinitely large (thanks to Heisenberg's uncertainty relation).
Would it neccessarily heat up? I think it would depend on the transparency of the material. I could be way off base here, but there are lenses for extremely high power lasers which do not melt when used. If the glass 'slowed' the light down, via absorbing energy, then you wouldn't be able to see anything out of it anyways.. (not in the visible spectrum at least)..
Maybe this hypothetical slowglass would make a great battery?
Sounds like he got his information in a college physics class; where were you when they covered optics and electrostatics?
The higher the index (i.e. slower the speed of light) in a material, the thinner the lens. That's why I can get 1/8" thick polycarbonate lenses for my glasses that do the same job as 1/2" thick glass.
Spectral dispersion is a problem in this application, though... however, if you're doing spectroscopy, a high-dispersion prism is useful... so therefore spectroscopy may be one of the first applications of a condensate prism.
As for the capacitor issue - The permittivity (capacitance/thickness) of a material is established by the speed of propogation of an EM wave (e.g. light) through the material. So a Bose-Einstein Condensate could make an outstanding dielectric for a capacitor, assuming its breakdown potential and leakage properties are acceptable.
I can see the fnords!
So if your driving at 38mph with the headlights on...
Yes, if you could push a mirror through the condensate faster than 38 mph you would definitely get some pretty cool Cherenkov radiation. This is essentially what Cherenkov radiation is, only Cherenkov radiation is produced by charged particles moving faster than 38 mph. Of course, moving a mirror through this gas would pose certain difficulties.
I heard an interesting story once regarding Cherenkov radiation. Apparently in some of the older accellerators, in order to line up the detector with the beam of electrons (or whatever), the experimentalist would put his/her eye in the path of the beam and look at the Cherenkov radiation (typically blue) in order to see precisely where the beam was. The electrons were travelling (once in the eye) faster than the local speed of light, so they spit off Cherenkov radiation. But I'm not sure I'd really want them shooting on through my brain!
--Artemisia
Actually, the neutrinos can't create Cherenkov radiation, since they're neutral. The neutrino detectors detect the charged particles created when the neutrinos decay. But you are right about them using Cherenkov radiation to do it.
--Artemisia
Actually, the BEC has a very tiny head capacity, so it probably wouldn't freeze your eyes... Of course, the vacuum chamber might break your neck...
--Artemisia
my car was faster than a beam of light!
-- NoWonder of WonderWorks/OmegaProject
Well, yeah, I guess...But since the slowing occurs in a lab environment, and probably inside some rather spooky equipment, I don't think it's gonna help much.
A bomb on the lab is still going to vaporize the whole shebang.
How did we get on this topic, again? I can't believe I'm talking about bombing a danish phyics lab.
So did anyone else think of that Bob Shaw short story 'Light of Other Days'?
c I believe was the speed of light in a vacuum that is constant speed of light through anything else isn't
Yeah but I'm too tired to punctuate....Actually I'm too lazy cause I never do it when I'm awake either..
Hmm... Here's an odd thought.. For a moment, assume that technology has advanced to a point where size no longer matters. Power no longer matters. Heat no longer matters, etc.
Ok, everyone has seen the light sabers in Star Wars. What if the handle contained a SUPER high powered laser and one of these devices. Then, when activated, the light would slowly extend until it reached a set limit. Then the device would get to 0 degs K and hold the light still.. Ok.. So I'm crazy.
Maybe I just like light sabers too much.
:-)
Hexy - a strategy game for iPhone/iPod Touch
If light can be slowed to a certain speed, does that also mean it's -possible- to speed it up?
I don't think it's implied by this approach.
I've never really believed that the "maximum speed" of anything is the speed of light. It just seems odd placing a limit on something that we don't really know everything about.
Not really. I don't know everything about my car, but I have a pretty good idea what its limits are. We may not know everything about light, but we know some things. More importantly, we know quite a bit about the behavior of mass as it approaches lightspeed -- it acts in a way that very strongly supports the idea of a lightspeed limit.
It *may* be possible to somehow "sidestep" the lightspeed limit, but that's another question.
This is, sort of, the first thing that popped into my mind too. Consider fiber optic networking.
There is a speed limit (not a bandwidth one) imposed on these networks because we can not pump data into them fast enough. But once data is in there, it's moving real fast.
It's moving so fast in fact, that a single bit of data takes up a whole lot of space. You need a very long piece of cable to 'pipeline' a very short burst of data. Hence, the lengths of cable in an optical FDDI ring must be pretty significant, else a data packet can start arriving at the original station before it's finished being sent. This poses a problem.
Now, with a EBC fiber, with light moving REAL SLOW, you can pump in individual photons for individual bits... So the data density per linear distance increases significantly, as the rate of transmission decreases proportionally. Not exactly a good solution for a networking medium...
But, consider a very short (distance) EBC optical buffer that data is stuffed into; and once full, a switch opens and a massive burt of data (oh, a GB) blasts down the pike at the speed of light.
-- What you do today will cost you a day of your life.
About ten years ago, I went to Florida on vacation. On the Ft. Lauderdale boardwalk, I bought a little tin can, roughly the size of a Coke can, labelled "Canned Florida Sunshine". A typical tourist novelty - like sand in shorts.
:)
I've never openned it for fear of the sunshine getting out. But now, if I have some of this supercooled atom soup, I can open the can, capture the sunshine, and enjoy it during the New England winter.
-- What you do today will cost you a day of your life.
The maximum speed of information is the speed of
light in vacuum. If information went faster you
would be messing up the sequence of cause and effect.
The light speed in non-vacuum hasn't got anything
to do with this though.
(and note that if it's not information it *can* go
faster than light, but it's useful for nothing anyway so..)
There's nothing stopping you from going faster than
light speed in non-vacuum (by that I mean faster than
38 miles/second in this case). It happens all the time in
physics experiments. It's a bit like going faster than the
speed of sound, it will be a light "boom" which is visible as a blue
corona. I'm not 100% sure but I believe the blue color
of the water in nuclear reactors are caused by this.
In any event I have seen many photos of the effect.
As far as I understand it: no. The "speed of light" that everyone hears about is the accepted speed of photons through space, with nothing to slow 'em down. The speed of light goes down as the photons pass through various substances, much like a person trying to run through water is much slower than on dry land. This is what causes all those nifty keen prismatic effects when light goes through glass and water at the right angle.
Now, just as the speed of light in space is a certain amount, so too is the speed of light in this substance the scientists are playing with. And just like you cannot exceed the speed of light while travelling through space, you can't exceed it if you were travelling through that super-cooled substance. Therefore, no object could accelerate even close to 38 miles per hour, inlcuding radio waves, fast cars, or Microsoft lawyers on their way to court with their latest faked video, while travelling through that substance.
Or something like that...
A nice black peice of paper will do that, you'll end up with a hot black peice of paper..
;-)
"Other Days, Other Eyes" was the name of the book. As I recall it ended with a scene of crop dusting airplanes seeding the entire countryside with slivers of slow glass, each a different thickness and thus having a different time constant. Talk about invasion of privacy . . .
VonSlatt
The Steampunk Workshop
It runs Windows 98. :)
...David
As well, as long as you BEC isn't perfectly transparent, you'd get heat deposited in there. Which might make it somewhat difficult to keep it at 50E-9 K...
Hurricane Application Group, Dept of Meteorology Control, Ministry of Proactive Defense
There was a Wired article on some guy that said he could reflect gravity. It involved a superconducting disk, and the Wired article made him out to be a loony, but they didn't discount the possibility.
The idea being that the superconducting disk would diminish the force of gravity between any objects on opposite sides of the disk.
Probably BS, but whatever.
--
There are no trails. There are no trees out here.
as username and password.
Petrus Vectorius
Oh, man, I read that story in highschool -- loved it.
One thing I brought up was that the slow-glass farms would have to be really secure against tresspassing, else pranksters could moon the glass (only to be seen 10 years later), or worse.
Also: once installed, light from inside the house would start traveling throught the glass. 10 years later, someone could watch what was going on in your house. (Imagine the year is 2006 and we finally get to see OJ kill his wife?)
_______
2B1ASK1
I remember seeing some japanese show that was doing that with big solor collectors on building roofs, and distributing it indoors via fiber optics. Bummer when it's cloudy out, tho.
_______
2B1ASK1
C is the speed of light in a vacum. What light does in gas, water or Bose-Einstein condensates is of zero consequence to relativity.
Is there anyone who could give us a more elaborate summary than this ? I can't get at the article either... (can you say /. effect ?)
superblog.org: all your favourite blogs on o
See, this is why Anonymous Cowards need to go away. This one couldn't be bothered to read the article before posting a stupid and arrogant comment. Besides, no one implied that c3e8; the slowing of light as it passes through other substances is a well known phenomen among bright, interested 12-year-olds.
The speed of light does not slow at all. It remains at the constant velocity of c, BUT takes a longer path through mediums other than vacume. It's like driving your vehicle 70mph from point a to point b, then driving it again at 70mph, but taking a detour to point c before arriving at b, taking twice as long and claiming the speed at being 35mph. The speed does not change on bit, but the distance travelled does. Just goes that the distance travelled through a medium is longer than trough a vacume so it would take longer for the light to travel through the medium, but the velocity of light is still the same.
Steve's Computer Service, Hobbs, NM
Slowing the speed of light won't change wavelength. I.E. you can't change visible light into x-rays because the wavelength remains the same. Wavelength velocity. x-rays and visible light travel at the same velocity.
Steve's Computer Service, Hobbs, NM
Hey, anyone know alot about Absolute Zero?
From what I remember when the temperature reaches Absolute Zero the atoms just stop moving?
Anyone have any info on it?
Speaking of neat visual effects, I wonder what the light looks like exiting the einstein-bose material.
When a laser is shot through a glass of light it refracts and generally keeps moving as a ray. Cherenkov radition creates a nice blue glow. The question being, when light exits the Danish material, does it exit as a general glow or as a a slightly diffracted beam?
Not quite. Cherenkov radiation is the shock wave (of light) produced by something travelling faster than the *local* speed of light -- e.g., something moving 50 MPH through our Bose-Einstein condensate with a 38 MPH local lightspeed. It's analogous to the shock wave produced by a supersonic object (bullet, jet, etc.) moving through the atmosphere faster than the local sound speed. But the "superluminal" object is still limited to travelling slower than the *vacuum* speed of light (c). (I suppose a tachyon *could* produce Cherenkov radiation, but you don't need one.)
Experimental physicists use this effect in things like neutrino detectors, such the AMANDA detector at the South Pole: fast-moving subatomic particles created by interactions between neutrinos and atoms inside the earth go zipping through South Polar ice faster than the speed of light *inside ice*, creating a flash of Cherenkov radiation. If you have light detectors embedded in the ice, you can pick up the flash; if you have enough detectors and good clocks, you can track the flash moving through the ice and figure out which direction the particle came from, which tells you where in the universe the parent neutrino came from...
I suspect the original poster's idea *won't* work because it relies on getting light to travel faster than the local light speed, which by definition may not be possible...but I'm not up on my relativistic shock wave theory.
-- Keysh (Peter Erwin)
Seems to me that the people that slowed light down didnt get enough attention from their parents as children or just wanted to be in the news because I don't see any use for this! Do you? (feel free to flame...I like flames...see the nickname!!!)
If you are going to do something like that, do something thats useful! (besides filling up space in the sunday paper!)
So you get this material with a mega-galactic refractive index, so the light passing through must presumably travel in some sort of spiral or helix pattern. Therefore the distance it must travel is MUCH further.
So how do you measure the speed?