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Light Can Twist as Well as Spin
NASA -- Astronomy Picture of the Day ^ | 11-19-03 | apod

Posted on 11/19/2003 3:30:55 AM PST by Boot Hill


Explanation:   Light is more complicated than we thought. When astronomers measure light, they are usually concerned with its direction, energy, and spin polarization (sometimes). Recently, however, it has been more broadly realized that photons can also have orbital angular momentum (OAM), an attribute classically analogous to the Earth orbiting the Sun as well as spinning on its axis. Pictured above, the wave-front of a photon with OAM is shown to be twisted, in contrast to the flat plane of zero OAM light. Light with OAM might be used to increase the information content of communication or to discern specific types of astronomical sources. Passing through a common lens, light without OAM focuses to a point, whereas light with OAM focuses to a ring. Most light bouncing around the cosmos, however, is expected to have so little (or zero) OAM that the created ring is too small to measure. Even given other promising methods for measurement, exploiting OAM for astronomical discovery might be as much an issue of observational practicality as theoretical possibility.


TOPICS: Extended News; Miscellaneous; Technical
KEYWORDS: light; optics
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Holy orbiting photon, Batman, we have a new "twist" to optical theory!

Let's see, Maxwell's equations require that the electric and magnetic components of the wave be orthogonal, but nothing requires those two components to be in phase with each other. Is this what's got the photons panties in a twist?

--Boot

1 posted on 11/19/2003 3:30:56 AM PST by Boot Hill
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To: Boot Hill
Given that the shape of photons with OAM is helical, I guess this now qualifies as a light meal.


2 posted on 11/19/2003 3:42:11 AM PST by ovrtaxt ( http://www.fairtax.org **** Forget ANWR. Drill Israel !)
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To: Boot Hill
So, if we consider light a wave of energy rather than a particle, what are the ramifications of other electromagnetic emissions, i.e. any waves across the spectrum such as x or gamma or micro waves, with OAM properties? Maybe a new Muslim Killer for the troops?


3 posted on 11/19/2003 3:48:12 AM PST by ovrtaxt ( http://www.fairtax.org **** Forget ANWR. Drill Israel !)
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To: Boot Hill
Out of phase orthogonals can certainly put ones panties in a twist. :-)
4 posted on 11/19/2003 3:54:41 AM PST by Mind-numbed Robot (Not all things that need to be done need to be done by the government.)
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To: Boot Hill; PatrickHenry; RadioAstronomer; Piltdown_Woman; longshadow; Physicist
Great post, Boot Hill
5 posted on 11/19/2003 3:57:35 AM PST by edwin hubble
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To: ovrtaxt

HOLY RAVIOLI! The way the light is twisting off the plate of pasta makes it seem as if you can see a face in there ;>)

6 posted on 11/19/2003 4:04:31 AM PST by BigLittle
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To: ovrtaxt
ovrtaxt asks:   "...what are the ramifications of other electromagnetic emissions, i.e. any waves across the spectrum..."

It would apply to all wavelengths.

--Boot Hill

7 posted on 11/19/2003 4:13:00 AM PST by Boot Hill
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To: edwin hubble
Thanks and thanks for pinging "the usual suspects".

--Boot

8 posted on 11/19/2003 4:14:18 AM PST by Boot Hill
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To: r9etb
"photons can also have orbital angular momentum"

--Boot

9 posted on 11/19/2003 4:34:31 AM PST by Boot Hill
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Comment #10 Removed by Moderator

To: ovrtaxt
Oooo, exactly! "Light ENERGY"! This she-layman is impressed.

11 posted on 11/19/2003 4:53:55 AM PST by bannie (The government which robs Peter to pay Paul can always depend upon the support of Paul.)
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To: Boot Hill
...we have a new "twist" to optical theory!

Well, plug that into your calculator and smoke it!

12 posted on 11/19/2003 6:01:30 AM PST by randog (Everything works great 'til the current flows.)
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To: Buckhead
Buckhead asks:   "Does this have any implications for the observed red shift..."

It might. While photons have no mass, they do have momentum and a spiraling photon might have to give up some of its momentum to achieve the orbital path described in the thread article. If this occurred, it would seem to imply a shift to a longer wavelength (i.e., red shift).

--Boot Hill

13 posted on 11/19/2003 6:58:07 AM PST by Boot Hill
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To: Boot Hill
Does light have its own DNA?
Looks like a DNA helix.
14 posted on 11/19/2003 7:08:33 AM PST by Chewbacca (I talk to myself because it is the only way I can have an intelligent conversation.)
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To: Boot Hill
Well, this is an odd twist....

If it really is an "angular momentum" in the usual sense of the term, then it should be possible to bend light by (somehow) exerting a torque on the wave front.

I guess that would be part of the explanation for refraction....

15 posted on 11/19/2003 7:46:58 AM PST by r9etb
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To: BigLittle
good one.
16 posted on 11/19/2003 7:49:43 AM PST by null and void (Lord Hildamort!™ - She Who Must Not Be Named)
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To: Boot Hill
But can light twist and shout?
17 posted on 11/19/2003 7:50:51 AM PST by null and void (Lord Hildamort!™ - She Who Must Not Be Named)
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To: Boot Hill; petuniasevan
APOD is a regular feature of the day thanks to one of our long-time FReepers. Get on the list, don't miss out.
18 posted on 11/19/2003 9:01:00 AM PST by RightWhale (Close your tag lines)
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To: Ernest_at_the_Beach; sourcery
ping
19 posted on 11/19/2003 9:13:35 AM PST by Libertarianize the GOP (Ideas have consequences)
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To: Boot Hill
TE and TM waves.......... I thought we knew that back in Maxwell's time...
20 posted on 11/19/2003 9:18:03 AM PST by richtig_faust
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To: BigLittle
BWa hahahhaah, pretty cool.
21 posted on 11/19/2003 9:18:49 AM PST by richtig_faust
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To: Amelia
I think you'll like this one. ;-)
22 posted on 11/19/2003 9:19:45 AM PST by Scenic Sounds (Hoy, no tengo ningún mensaje a compartir.)
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To: Buckhead
Does this have any implications for the observed red shift upon which the Big Bang theory rests?


No, the red shift is based on a doppler shift (frequency shift) it has nothing to do with this.
23 posted on 11/19/2003 9:20:03 AM PST by richtig_faust
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To: Boot Hill
Like this?


24 posted on 11/19/2003 9:27:24 AM PST by <1/1,000,000th%
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To: Boot Hill
Warp Nine now, Mr. Data!
25 posted on 11/19/2003 9:29:21 AM PST by AxelPaulsenJr (Excellence In Posting Since 1999)
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To: edwin hubble
Thanks for the ping.
26 posted on 11/19/2003 9:32:44 AM PST by PatrickHenry (Felix, qui potuit rerum cognoscere causas.)
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To: RadioAstronomer; All
I can't get a handle on this. If we observe light with OAM, what are we supposed to conclude about it's origin? What does this data tell us? If this is going to be an astronomical tool, what do we use it for? (In case all of this is obvious, then break it to me gently.)
27 posted on 11/19/2003 10:45:06 AM PST by PatrickHenry (Felix, qui potuit rerum cognoscere causas.)
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To: RightWhale
Thanks for the promo, RightWhale! :-)
28 posted on 11/19/2003 1:02:53 PM PST by petuniasevan (Kirk: Oh no! Ensign Pillsbury! Bones: He's bread Jim!)
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To: Boot Hill
Light Can Twist as Well as Spin

Holy Foot Candles Batman - Light has been taken over by the DemoncRATS!

29 posted on 11/19/2003 1:09:54 PM PST by N. Theknow (Be a glowworm, a glowworm's never glum, cuz how can you be grumpy when the sun shines out your bum.)
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To: richtig_faust
richtig_faust sez:   "I thought we knew that back in Maxwell's time."

Yes, it is amazing how all of man's discoveries about EM wave phenomena comport so exactly with Maxwell's equations.

--Boot

30 posted on 11/19/2003 1:49:57 PM PST by Boot Hill
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To: richtig_faust; Buckhead
richtig_faust sez:   "No, the red shift is based on a doppler shift (frequency shift) it has nothing to do with this."

You know, I almost answered Buckhead that way, but then I realized I was responding less to his specific question, than to where I sensed he seemed to be heading with his query (a short lifetime universe).

While it is true that the current state of science regarding the red shift is that it is due to Doppler shift, nonetheless, one would be taking an imprudent step to translate that "understanding" to a non-scientific limit of "proven and irrefutable".

Since the phenomenon described in the thread article is so new and there is so little understanding of how it would be created in nature, or how an existing "normal" light beam could be "twisted" or how twisted light could be detected, distinguished and observed, it might be more prudent to be a bit more circumspect in regards to such answers.

For instance, in #13 above, I present one possible scenario with "twisted" light that could account for an apparent lowering of its frequency like occurs with red shift. Could this account for the observed astronomical red shift? It's possible, but while I don't think so, I also believe that it is still too early just to give a blanket "No" to the question.

--Boot

31 posted on 11/19/2003 2:51:19 PM PST by Boot Hill
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P L A C E M A R K E R
32 posted on 11/19/2003 6:42:00 PM PST by PatrickHenry (Felix, qui potuit rerum cognoscere causas.)
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To: edwin hubble
Thanks for the ping :-)
33 posted on 11/19/2003 8:01:06 PM PST by RadioAstronomer
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To: PatrickHenry
I can't get a handle on this. If we observe light with OAM, what are we supposed to conclude about it's origin? What does this data tell us?

I need to look at this closer.

34 posted on 11/19/2003 8:52:50 PM PST by RadioAstronomer
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To: maxwell; Physicist; VadeRetro; RightWhale
ping
35 posted on 11/19/2003 8:54:26 PM PST by Chancellor Palpatine
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To: ovrtaxt
Hey! Whadda ya think yer doin' sneakin' around in my backyard taken pitchers. There oughta be a law ...
36 posted on 11/19/2003 8:58:39 PM PST by MHGinTN (If you can read this, you've had life support from someone. Promote life support for others.)
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To: Boot Hill
Except for the fact that color is based on FREUQUENCY not momentum or force.
37 posted on 11/20/2003 6:20:46 AM PST by richtig_faust
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To: richtig_faust
richtig_faust says:   "Except for the fact that color is based on FREUQUENCY not momentum ..."

Your statement is incorrect. Frequency is intimately connected to the photon's momemtum because when a photon looses momentum, the result is a loss of energy. And the consequence of a photon losing energy, is a decrease in frequency, i.e., a red shift. See below.

momentum:
p = m*v

energy of a photon:
E = h*f = mc2
      (where h = Planck's constant)

and by combining eq. 1 and eq. 2, we get the momemtum of a photon:
p = h*f/c
      (where c = speed of light)

From eq. 3 it can be seen that if the photon's momentum (p) decreases, the frequency (f) must also decrease.

--Boot Hill

38 posted on 11/20/2003 9:37:02 AM PST by Boot Hill
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To: Boot Hill
I don't get any of this, but I did stay at a Holiday Inn Express last night.
39 posted on 11/20/2003 9:39:13 AM PST by Principled
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To: Boot Hill
Anyone who lived through the disco era could have told them that.
40 posted on 11/20/2003 9:44:21 AM PST by rogers21774 (The guilty taketh the truth to be hard, for it cutteth them to the very center.)
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To: Boot Hill
You are making that assumption based upon the particle nature which is indeed related to plank's constant (but you forgot the divisor of 2*pi). BUT doppler shift is a frequency shift measurement, they are NOT measuring momentum, they measure FREQUENCY.


A good example of equipment that indirectly measures angular momentum is a Magnetic Resonance Imaging machine which catches frequency shift based upon the change in angular precession.
41 posted on 11/20/2003 12:02:49 PM PST by richtig_faust
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To: RadioAstronomer
Orbital Angular Momentum of Photons

MEASURING THE ORBITAL ANGULAR MOMENTUM OF SINGLE PHOTONS
http://www.physics.gla.ac.uk/Optics/projects/singlePhotonOAM/

and this one from Phys Rev Letters:
http://optics.org/articles/news/8/6/14/1

Single photons show momentum state
18 June 2002

An optical technique reveals the orbital angular momentum state of single photons for the first time.

A new technique that measures the orbital - rather than the spin - angular momentum of single photons could lead to the development of super-efficient quantum communication systems. Previously, physicists had only been able to measure this quantity for many photons in a beam, or detect a certain value of it for single photons. But the set-up devised by Johannes Courtial of the University of Glasgow and colleagues should be able to reveal any orbital angular momentum state of a single photon (Phys. Rev. Lett. 88 257901).

42 posted on 11/20/2003 3:40:11 PM PST by edwin hubble
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To: edwin hubble
Thanks for the links :-)
43 posted on 11/20/2003 8:34:34 PM PST by RadioAstronomer
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To: Boot Hill
Light penetrates the darkness like a drill?
44 posted on 11/20/2003 8:42:46 PM PST by ValerieUSA
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To: Chewbacca
The helix is so dynamic, it may be God's signature on His creation.....
45 posted on 11/20/2003 8:54:15 PM PST by ValerieUSA
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To: richtig_faust
richtig_faust says:   "you forgot the divisor of 2*pi."

I forgot no such thing. Energy equals h*c, not h-bar*c. The equation properly uses Planck's constant (h), not Dirac's constant (h-bar). Planck's constant is the correct choice in the above equations.

richtig_faust says:   "BUT doppler shift is a frequency shift measurement, they are NOT measuring momentum, they measure FREQUENCY."

Of course they measure frequency, nobody has suggested otherwise. However the result of a decrease in momentum of a photon is a commensurate decrease in the observed frequency.

--Boot Hill

46 posted on 11/20/2003 10:20:00 PM PST by Boot Hill
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To: ValerieUSA
Interesting way of viewing it!

--Boot

47 posted on 11/20/2003 10:22:02 PM PST by Boot Hill
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The old Chubby Checker Effect.
48 posted on 11/20/2003 10:22:17 PM PST by Consort
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To: BigLittle
Cute. Took a minute.
49 posted on 11/20/2003 10:23:54 PM PST by MaeWest (Reporting from behind west coast enemy lines.)
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To: Boot Hill
However the result of a decrease in momentum of a photon is a commensurate decrease in the observed frequency.


But not angular momentum
50 posted on 11/21/2003 6:12:20 AM PST by richtig_faust
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