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Breaking Down Time
Astronomy.Com ^ | 2/23/2003 | Pamela Gay

Posted on 02/24/2003 6:22:29 PM PST by NukeMan

Breaking Down Time Struggling scientists try to apply quantum theory to time, but time refuses to be quantized. by Pamela L. Gay

Quantum mechanics was born out of a mathematical leap of faith that wasn't initially thought to describe reality. Now, this still philosophically (and mathematically) difficult theory has grown to encompass most of physics. It successfully defines how large-scale physics breaks down at small scales for energy, momentum, position, and possibly time. It also specifies minimum measurable amounts (quanta) for these phenomena. However, observations by the Hubble Space Telescope have shaken the idea that time is quantized.

The quest of the last century has been to find a theory unifying general relativity with quantum mechanics. The Holy Grail of that quest is a theory of quantum gravity. While no complete theory has been established, scientists had some ideas of what it should include — a particle that carries the force of gravity and a quantum of time, for example. The gravity-carrying particle, dubbed a graviton by theorists, has too high an energy to be detected in current experiments. This leaves quantized time as the only testable aspect of quantum gravity.

If time is quantized like the energy of photons, there should be a certain minimum measurable quanta of time, called a "Planck time" (named after German physicist Max Planck, who originated the idea of quanta). This also means that life, like a movie, may appear to be a continuum of unfolding events but is really nothing more then a series of snapshots that together define the past and future.

One consequence of quantized time is that the speed of light should not be measurable with a precision better than one unit of Planck time, because time becomes undefined or "blurry" at smaller intervals. If light is quantized, it might have minute speed differences that we cannot measure.

If photons emitted from a source at the same instant have tiny speed differences, the light waves will arrive at Earth with different phases. Over short distances, these discrepancies aren't noticeable, just as differences between two cars going 90 and 92 kilometers per hour aren't evident after they've traveled just 10 meters. Over large distances, though, differences in the light become apparent, just as the velocity differences between our cars are obvious after they've traveled 1,000 kilometers.

Astronomers Richard Lieu and Lloyd Hillman at the University of Alabama in Huntsville used this idea to look for speed distribution in light from galaxies billions of light-years away that were imaged by the Hubble Space Telescope. If all photons are traveling from the galaxy at the exact same speed then all the light waves will arrive in phase. When they pass through a telescope's aperture, they interact with each other to create a pattern of bright and dark rings called an Airy disk. However, if the speeds are even the tiniest bit off, the light is not in phase. These light waves align chaotically, and no pattern is formed. Lieu and Hillman suspected that slight differences in the speed of individual photons would cause their light waves to get out of sync over great distances, preventing the Airy disk from forming. Much to their surprise, the light was all in phase and an Airy disk appeared, implying that time is not quantized.

The conclusion that time is not quantized poses large problems for scientists. According to Lieu, "The Big Bang theory supposes that at the instant of creation, the quantum singularity that became the universe would need to have infinite density and temperature. To avoid that sticky problem, theorists invoked the Planck time. They said if the instant of creation was also a quantum event, when space and time were both blurry, then you don't need infinite density and temperature at the start of the Big Bang."

Without quantum time, the universe becomes mathematically uglier at the moment of its inception. Like so many maps that were supposed to lead to the Holy Grail, our notions of quantized time have failed to lead us to a unified quantum theory.


TOPICS: Science
KEYWORDS: crevolist
Well, I understand the article, the results, what is at stake. etc. What I don't know is if this is a knockout punch - i.e. the theory of quantized time could never recover. Maybe some smart Freeper can weigh in on this....
1 posted on 02/24/2003 6:22:29 PM PST by NukeMan
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To: All
bookmark
2 posted on 02/24/2003 6:24:51 PM PST by OXENinFLA
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To: NukeMan; RightWhale; VadeRetro; ASA Vet; vannrox; blam; Physicist; RadioAstronomer; boris
Ping! Strike against quantized time.
3 posted on 02/24/2003 6:25:26 PM PST by NukeMan
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To: VadeRetro; jennyp; Junior; longshadow; *crevo_list; RadioAstronomer; Scully; Piltdown_Woman; ...
Quantized time ping.

[This ping list is for the evolution -- not creationism -- side of evolution threads, and sometimes for other science topics. To be added (or dropped), let me know via freepmail.]

4 posted on 02/24/2003 6:26:21 PM PST by PatrickHenry (Felix, qui potuit rerum cognoscere causas)
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To: Physicist
Ping
5 posted on 02/24/2003 6:29:14 PM PST by William McKinley (You're so vain, you probably think this tagline's about you)
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To: NukeMan
Turtles all the way down placemarker.
6 posted on 02/24/2003 6:33:54 PM PST by js1138
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To: NukeMan
Sleepy science night.
7 posted on 02/24/2003 6:44:54 PM PST by js1138
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To: js1138
Sleepy science night.

Learn to catnap between the quanta. That way you won't miss anything.

8 posted on 02/24/2003 6:46:57 PM PST by PatrickHenry (Felix, qui potuit rerum cognoscere causas)
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To: PatrickHenry; Physicist
They need to get in touch with the phone companies, who, judging by my bill and its one-minute billing increments, clearly understand and have mastered quantized time...
9 posted on 02/24/2003 6:55:33 PM PST by general_re (Friends help you move. Real friends help you move bodies.)
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To: NukeMan
The deal with the Airy disk in an astronomical telescope is that the source has to be an infinitely distant point source. That means that all the rays start out parallel and together.

If the optics are good enough and the magnification is high enough, the Airy disk might be visible. It forms a limit to the resolution of the telescope.

Most telescope don't resolve to the Airy disk limit. If the object is a galaxy, it automatically isn't a point source, and if it is far away the light might have to pass through gravitational fields that cause gravitational lensing. All this will ruin the chance of seeing the Airy disk. However, since the telescope is apparently resolving to the Airy disk limit, the distant galactic light source is acting sufficiently like a point source.

In any case, we are dealing with the useful fiction [model] of photons, which might be wavelike or particlelike depending how they are being perceived. We'll need something more sensitive to detect quantized time.

10 posted on 02/24/2003 7:02:21 PM PST by RightWhale
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To: NukeMan
There's a lot in this article I don't understand.

If time is quantized like the energy of photons, there should be a certain minimum measurable quanta of time, called a "Planck time"

Why does the quantization of gravity imply the quantization of time? I've never heard it stated that way before. My understanding is that the sense in which the Planck time can be said to be a "quantum" of time is different from the sense in which a photon can be said to be a quantum of electromagnetism.

If light is quantized, it might have minute speed differences that we cannot measure.

Light is certainly quantized. But what does "it might have minute speed differences" mean? Differences from what?

If photons emitted from a source at the same instant have tiny speed differences, the light waves will arrive at Earth with different phases.

If the photons have different velocities, they should have different frequencies, but in that case, they can't remain in phase at all. But assuming that two photons from a distant galaxy have exactly the same frequency, why should they be in phase? They weren't emitted in phase.

Without quantum time, the universe becomes mathematically uglier at the moment of its inception.

Without knowing what that mathematical description is, who can say whether it's ugly? The universe is the way it is, and not how we might wish it to be.

11 posted on 02/24/2003 7:26:12 PM PST by Physicist
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To: NukeMan
Quantum mechanics was born out of a mathematical leap of faith that wasn't initially thought to describe reality.

An extremely poor description of Planck's results. It would be better to say that QM was born out of an interpolation formula. There was no "leap of faith" only a (much) better explanation.

Planck invented a forumla that interpolates between low and high frequency black-box radiation behavior. The results of the formula were so good, that Planck asked the question, what physical mechanism could describe his formula. The rest is History.

Otherwise the article seems a reasonable description of things.

12 posted on 02/24/2003 9:37:55 PM PST by Doctor Stochastic (Vegetabilisch = chaotisch is der Charakter der Modernen. - Friedrich Schlegel)
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To: Doctor Stochastic; Physicist
Otherwise the article seems a reasonable description of things.

I agree with Physicist about his misgivings concerning "Planck time". I understand that the Planck distance is probably the minimum distance a photon can travel such that the distance has any meaning. But this isn't the same -- at least to me -- as saying that time is quantized.

Here's another article on this topic, in Nature.

13 posted on 02/25/2003 3:16:28 AM PST by PatrickHenry (Felix, qui potuit rerum cognoscere causas)
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To: PatrickHenry
The article does seem to say that experimental evidence is for continuous time. I don't remember reading about any time-quantization either. Even in the particle-in-a-box, space is continuous; allowed positions of the particle may be discrete. (But the allowed locations could be dense, I think.)

14 posted on 02/25/2003 6:23:29 AM PST by Doctor Stochastic (Vegetabilisch = chaotisch is der Charakter der Modernen. - Friedrich Schlegel)
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To: PatrickHenry; Doctor Stochastic; Physicist
Usenet groups can be your friend! Found a brief discussion with some pointers to the original paper (not the bowdlerized Astronomy.Com article) and criticisms as well:

http://groups.google.com/groups?dq=&hl=en&lr=&ie=UTF-8&group=sci.astro.research&selm=mt2.0-27823-1046092703%40star.bris.ac.uk
15 posted on 02/25/2003 5:06:52 PM PST by NukeMan
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To: PatrickHenry
LOL!
16 posted on 02/25/2003 7:15:17 PM PST by Savage Beast
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To: NukeMan; Physicist
"Astronomers Richard Lieu and Lloyd Hillman at the University of Alabama in Huntsville used this idea to look for speed distribution in light from galaxies billions of light-years away that were imaged by the Hubble Space Telescope. If all photons are traveling from the galaxy at the exact same speed then all the light waves will arrive in phase."

Would this not require finding a galaxy which is exactly normal to the line of sight?...

A 'tilted' galaxy may be 100000 light-years wide; hence the light from the far edge is under no constraint to be 'in phase' with the light from the near edge.

I've always been a little confused as to why "nearby" galaxies such as Andromeda do not look "smeared", since the light from more distant parts does not represent a true 'snapshot' of how the galaxy looked when the light from the nearer parts was emitted. Probably a stupid question, but I ask a lot of stupid questions.

--Boris

17 posted on 03/01/2003 6:43:31 PM PST by boris
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To: NukeMan
There's no absolute scientific basis to assert that time didn't just start -- NOW!
18 posted on 03/01/2003 6:47:02 PM PST by bvw
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To: NukeMan
Beware of quantum ducks. Quark, quark!

Garde la Foi, mes amis! Nous nous sommes les sauveurs de la République! Maintenant et Toujours!
(Keep the Faith, my friends! We are the saviors of the Republic! Now and Forever!)

LonePalm, le Républicain du verre cassé (The Broken Glass Republican)

19 posted on 03/01/2003 6:54:03 PM PST by LonePalm (Commander and Chef)
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