MY Thread - LQG and/or ST?

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  • #1
Tsu
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I think, pretty much - never mind. I tried to watch Integral's link to the PBS video, but I need to use Ivan's computer with the high-speed connection and that just isn't going to happen any time soon. I have so many questions, even I can't get them sorted out enough to make sensible posts. I can try to find more basic info about LQG and string theory somewhere on the net. Guess I'll first google "LQG for Dummies" first... Also probably "String Theory for Dolts". Once I have that all figured out, I'll be back with some questions. Maybe in my next life I'll be hard-wired for this stuff... :frown: (GOOD LORD! WHAT AM I WISHING FOR?)

Can anyone guide me to some sites about these two theories where they don't speak Greek? (you know, Greek - like 'sumthinorother diffeomorphism' - What the h*** IS THAT?) :frown:

Thanx anyway...

i should seek professinal help... i marry a nerd and i hang out with him and all his friends who just scramble my brains... YOU'RE ALL OUT TO GET ME, AREN'T YOU?! IT'S A CONSPIRACY! hmm... professional help it IS...:wink: Is there a 12-step group for physics wives?
 

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  • #2
Evo
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Have you tried Brian Greene's Elegant Universe for string theory? Both the book and the TV show are perfect for laymen (like me). He explains things in a very simple and entertaining way.

Hyperspace - A scientific odyssey through parallel universes, time warps & the 10th dimension - by Michio Kaku

Other books -

Not really related, but he's hot (and funny), so you might be interested. He wrote "Faster than the Speed of Light" Joao Magueijo. I saw him on C-SPAN a little over a year ago, after I read an article on VSL. His website is http://theory.ic.ac.uk/~magueijo [Broken]

Also, "The Fabric of Reality: The Science of Parallel Universes - And it's implications" by David Deutsch. He's more into multiverses and time travel, but an interesting read. http://www.qubit.org/people/david/David.html

People here may have differing opinions, they, having actual knowledge of these things, may say they're not worth the time spent reading them, so you may want to take whatever advice someone here gives on these over mine.
 
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  • #3
marcus
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Originally posted by Tsunami
I think, pretty much - never mind...Is there a 12-step group for physics wives?

that's well written
in a dramatic many-voiced spontaneous-sounding style
and its quite funny
the idea of a 12step group-----actually it should be
what is called a "support group"----for physics wives is
first rate. there should be.

a friend of mine, solid state physicist, did a stint in holland at
philips eidhoven and fell in love with a lovely dutch girl
who lived in the town near the research labs, but
she had no idea of physics----she was good with languages---and
they moved to Los Alamos and lived completely among physicists
and their wives in a kind of suburb. She could have used a support group for physics wives. Should have had one really.
Finally she ran off with a geologist. He liked mountains,
which she could understand.

I don't think it is a very good idea for someone in your situation to try to learn LQG or string theory for that matter. Much rather learn German or sing in the campus glee club. Singing 4-part harmony is very useful---it makes people happy.

You are good with one-liners, so I think you are handy with language. Do you know some other languages besides English? If that's not too personal a question.
 
  • #4
jeff
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Originally posted by Tsunami I can't get them sorted out enough to make sensible posts. I can try to find more basic info about LQG and string theory somewhere on the net.

If you want to avoid wasting time on ideas that are popular in these sorts of low-brow public forums but not among physicists, forget about LQG.
 
  • #5
marcus
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Tsunami,

As you have doubtless gathered, I am real lowbrow and you are welcome to waste time trying to discuss anything you want with me, popular or not among whomever. As for research "demographics", here are numbers from a Los Alamos archive database. This relates to "popularity among physicists".

Numbers of scholarly preprints by year in Loop Gravity research topics
(keywords "loop quantum gravity", "spin foam", or "loop quantum cosmology")

2000 46
2001 48
2002 64
2003 70


--------------
Numbers of scholarly preprints by year in String research topics (keywords "string", "brane", "M-theory"


2000 1457
2001 1496
2002 1500
2003 1265

That is, those where the abstract summary of the paper has in it somewhere the word string, or the word brane, or the word M-theory.

More about this, and links to sources in the "Rovelli's program" thread serving as a Loop Gravity link-basket for want of sticky.

https://www.physicsforums.com/showthread.php?s=&postid=128448#post128448

Anecdotal evidence, in my experience, tends to confirm what you see in the numbers. I have repeatedly come across papers by authors who formerly did string research and have largely or entirely switched over.
 
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  • #6
Tsu
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Evo,
I've been watching the Elegant Universe on-line (the link that Integral posted). Actually listening would be more like it, as I don't have enough of something computer (ask Ivan) for the video to come through. I need to go down to his office to watch it on his system - except that he uses it for work, which he is ALWAYS doing! Listening is fine, but I'm a visual person, so I miss the visuals.

Kaku is excellent. Hyperspace is what made me realize 'HEY! I CAN understand this stuff!' As long as I can stay away from the math and keep to the concepts (is that possible?) I'll be fine. I can't sit and read a lot of this stuff at one time because I end up with such a twisty-face trying to force an understanding that I end up with a headache! So I take it small chunks at a time - let it sink in and then go back for more. :wink: I know I'll never be able to understand it the way these folks do. They seem to be able to instinctively see, feel and understand it - like it's a PART of them. I've always envied that ability. I've always WANTED that ability! But... On the other hand, none of these folks are as good as I am at being ME, so...

Marcus,
Many-voiced? You mean, like - SCHIZOPHRENIC?! Funny you should use the word 'dramatic'. I was 'this close' (*shows miniscule space between fingers*) to auditioning for Tony and Tina's Wedding. And I do speak Spanish and love languages. I have MANY interests - including the directions that all sciences are heading - which is why I want to learn more about LQM & ST.

Jeff,
*blows raspberry* Killjoy. Then tell me, what ideas ARE popular among physicists these days? I'll google them, too! :smile: Might as well have a well-rounded perspective, right?

Anyway, thank you all for your posts. I've started my own list of links to hit whenever I get the intense desire to get all twisty-faced, but feel free to post any others that you think might be excellent for non-nerds like me trying to exist amongst you genious types. It will take me awhile to get through it all, but I'll pop in at times with a question or 50. Ivan is really excellent with answering my questions, but lots of times I want a different perspective. Frequently, someone will come up with some off-the-wall phrase that just pulls it all together for me. Why am I even here, you ask? Don't ask ME! Like I said, professional help is probably MORE than indicated here...
 
  • #7
Evo
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I watched Elegant Universe when it originally aired & went online & ordered the video. It's also available on DVD now. Worth the few bucks. You can order it here http://shop.wgbh.org/webapp/wcs/stores/servlet/CatalogSearchResultView?storeId=11051&catalogId=10051&langId=-1&pageSize=20&searchText=elegant+universe [Broken]

Since I don't have a life (single & no desire to go hunting) I read at night in bed before I go to sleep, so I read a LOT! You're lucky to have Ivan, although he looks terribly pale... :wink:
 
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  • #8
Nereid
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Scientific American?

SciAm has had quite a number of 'forefront of physics' articles in the past year or three, and there's nary a Greek letter or equation on any page. Furthermore, many of the articles are written by those regarded as leaders in their fields - Smolin, Greene, Tegmark, Kane (maybe not a leader?), Bekenstein, ... All articles have a "More to Explore" section too.

Many local libraries carry subscriptions, your budget may stretch far enough for you to take out one of your own, and there's a (fee-based) online service too.
 
  • #9
Ivan Seeking
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You all should feel honored!

She won't talk to me about physics any more.

well...only on rare occasion and only with her eyes closed and her face all scrunched up.

...sometimes she even makes funny sounds...like she's in pain...
 
  • #10
Tsu
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Originally posted by Ivan Seeking
You all should feel honored!

She won't talk to me about physics any more.

well...only on rare occasion and only with her eyes closed and her face all scrunched up.

...sometimes she even makes funny sounds...like she's in pain...
Yer so funny, honey. BUT, I DO *TOO* TALK TO YOU ABOUT PHYSICS! It's just that, after 20 years, I'm becoming a little weary of the direct-heat version of Scrambled-Eggs-For-Brains. I'd like to check out the microwave version for a bit. :wink:

I don't know how 'honored' they should feel, either. I would think 'annoyed' would cover it better. I half expect that they're thinking as they post a few links for me "Here. Read these, kiddo, and come back when you can talk more than nonsense.":wink:

Thanx for that link, Evo. I think that's probably the way for me to go. (*reaches for credit card* 'oh boy... more Hawaiian Miles!' )

Nereid, with that on-line service of SciAm, I would have access to past issues, right? And I could run searches on different topics through their archives? (*reaches for credit card AGAIN* 'oh boy... even MORE Hawaiian Miles!' I go visit my cousin again!)

THANX, EVERYONE! You can ignore me now if you want. (But if you don't want to, that's nice, too!)
 
  • #11
Nereid
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Nereid, with that on-line service of SciAm, I would have access to past issues, right?
That's true; or rather, it was the last time I looked (I now have my very own, personal subscription, which the mailman (oops! not PC - postperson? letterdeliverer??) kindly brings me every month.
http://www.sciam.com/
You'll have to put up with pop-up ads though.
 
  • #12
Tsu
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Originally posted by Nereid
That's true; or rather, it was the last time I looked (I now have my very own, personal subscription, which the mailman (oops! not PC - postperson? letterdeliverer??) kindly brings me every month.
http://www.sciam.com/
You'll have to put up with pop-up ads though.
Why do you choose hard copy over on-line service?

edit: WAIT! OF COURSE! You don't have a computer in your bathroom?
 
  • #13
selfAdjoint
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Originally posted by Nereid
That's true; or rather, it was the last time I looked (I now have my very own, personal subscription, which the mailman (oops! not PC - postperson? letterdeliverer??) kindly brings me every month.
http://www.sciam.com/
You'll have to put up with pop-up ads though.

Mail carrier. In the US.
 
  • #14
Nereid
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Originally posted by Tsunami
Why do you choose hard copy over on-line service?

edit: WAIT! OF COURSE! You don't have a computer in your bathroom?
Trains and boats and planes (laptop batteries only last so long). The back patio, with a glass of Prosecco (laptop screens can't compete with the Sun). In bed (laptops don't take too kindly to hitting the parque if you drop them while falling asleep). Etc (Evo would understand, so would SelfAdjoint and marcus).
 
  • #15
Evo
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Nereid, you're right about needing the paper copy. BTW, I got my first subscription to Scientific American when I was around 16. It's what got me interested in Quantum Physics. They sent me a free book one time called "Phenomena of Physics" or vice versa, and I got hooked.

Actually, I do take my laptop to bed with me. I have a big bed and lots of empty space and I don't move around in my sleep, so...

Sad huh?
 
  • #16
Tsu
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I have questions.

From this page by Smolin's site (I think that's where I am anyway )
http://www.edge.org/3rd_culture/smolin03/smolin03_p3.html

My questions are in red.

"The key thing that Amelino-Camelia and others realized is that we can use the universe itself as an experimental device to probe the Planck scale. There are three different ways the universe gives us experimental probes of the Planck scale. First, there are accelerators in distant galaxies What accelerators? What causes them? that produce particles with energies much higher than we can produce in even the largest human-made accelerators. Some of these ultra-high-energy cosmic rays have been observed hitting our atmosphere with energies more than 10 million times those we have ever produced. These provide us with a set of ready-made experiments, because on their way to us they have traveled great distances through the radiation and matter that fill the universe. Indeed, there are already surprises in the data which, if they hold up, can be interpreted as due to effects of quantum gravity.

Second, we detect light and particles that have traveled billions of light years on their way across the universe to us. During the billions of years they travel, very small effects due to quantum gravity can be amplified to the point that we can detect them."
What do we use to detect them?
 
  • #17
Nereid
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Tsunami quoted: First, there are accelerators in distant galaxies that produce particles with energies much higher than we can produce in even the largest human-made accelerators.
then she asked: What accelerators? What causes them?
In the words of Stecker (p6)*: "In most theoretical work in cosmic ray astrophysics, it is generally assumed that the diffusive shock acceleration process is the most likely mechanism for accelerating particles to high energy. (See, e.g., Jones (2000) and references therein.) In this case, the maximum obtainable energy is given by Emax = keZ(u/c)BL, where u ≤ c is the shock speed, eZ is the charge of the particle being accelerated, B is the magnetic field strength, L is the size of the accelerating region and the numerical parameter k = O(1)
(Drury 1994).
" Very crudely, the same sort of thing that happens in accelerators at CERN, only over far, far larger distances, greater magnetic fields, or both (p7 has a good chart ("Hillas plot") showing the B-L relationship).

*reference to the Stecker paper in this marcus thread: https://www.physicsforums.com/showthread.php?s=&threadid=11309
Tsunami quoted: Second, we detect light and particles that have traveled billions of light years on their way across the universe to us. During the billions of years they travel, very small effects due to quantum gravity can be amplified to the point that we can detect them."
then she asked: What do we use to detect them?
CCDs at the focii of telescopes. Here's a thread - started by wolfram - on our very own PF on this topic:
https://www.physicsforums.com/showthread.php?s=&threadid=9367

I'm sorry to say that I've not followed up with an analysis of the HST images of distant supernovae (there are some excellent images, taken as part of the GOODS project: https://www.physicsforums.com/showthread.php?s=&threadid=11216)
 
  • #19
selfAdjoint
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Charge coupled device, I believe. Ultra sensitive electronic gizmo for detecting faint light "at the focus of large telescopes".
 
  • #20
Tsu
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Originally posted by selfAdjoint
Charge coupled device, I believe. Ultra sensitive electronic gizmo for detecting faint light "at the focus of large telescopes".
Excellent. Thank you.

From above:
"diffusive shock acceleration" - from a supernova? Are there other sources of cosmic rays that we measure?
 
  • #21
Nereid
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SelfAdjoint is right; they're the heart of your digital camera, and your videocam (and much else). Astronomers used to use photographic emulsion, on glass plates, but CCDs have now almost completely taken over (long list of reasons why).

In a nutshell, the 'wolfram thread' is about an analysis of a Hubble Space Telescope (HST) image of a relatively nearby supernova. One possible test of LQG is whether really distant 'point sources' (objects whose angular size is way below the resolving power of the telescope) become blurred. LQG predicts that they might; in effect, Planck-scale distortions can get amplified over billions of light-years to become detectable, by the HST.

The image of the nearby supernova is nice and sharp; but it's only a weak test of LQG.

What's really neat is that you, SelfAdjoint, marcus, wolfram, and I could do the tests ourselves - the relevant HST images are in the public domain, and the image analysis software is probably free too.

'PF members find evidence to support LQG' - it'd be a nice headline, don't you think?
 
  • #22
Tsu
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You guys are awesome. Thanks so much. Good, short concise answeres (so I can get back to my reading ) and NO MATH EQUATIONS. I like that!

Originally posted by Nereid
What's really neat is that you, SelfAdjoint, marcus, wolfram, and I could do the tests ourselves - the relevant HST images are in the public domain, and the image analysis software is probably free too.

'PF members find evidence to support LQG' - it'd be a nice headline, don't you think?
That would be SO COOL! I'll get started on that right away!
 
  • #23
Nereid
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Tsunami wrote: "diffusive shock acceleration" - from a supernova? Are there other sources of cosmic rays that we measure?
Again, very crudely:
- in interstellar and inter-galactic space there are electrons and ions (atoms with some electrons missing) floating around - a plasma
- there are also weak magnetic fields embedded in the plasma
- something like a supernova explosion causes the plasma to get compressed, as the electrons and ions screaming away from the explosion smash into the calm plasma that's there (this is the shock)
- within and around the shock front, the magnetic fields get all tangled up
- some electrons and ions get bounced back and forth between the tangled knots of magnetic fields (which also keep moving - the shock front isn't standing still!); each time they bounce, they gain energy (this is the diffusive acceleration)
- eventually, some break free and head on to the Earth.

What can accelerate charged particles to such high energies? Neutron stars (very high magnetic fields, short distances for acceleration), the hearts of active galaxies (magnetic fields as strong as CERN magnets; distances about the size of the solar system), to halos of Milky Way type galaxies (really weak magnetic fields; huge huge distances).
 
  • #24
Tsu
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Ooo. Good visuals, Nereid. Those help me a lot. Thanx! My bulb is getting brighter!

But my face is beginning to hurt. :frown: I'm takin' a break...
 
  • #25
Tsu
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Ya know - except for magnetic fields. For some reason, imaging magnetic fields in space in my own mind...doesn't work. I can't seem to 'see' it. Much less tangled up ones...

This is something that Ivan and I discuss quite a lot. You guys are just hard-wired to 'see' this stuff. I'm sick of being blind!
 
  • #26
Nereid
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What makes you think I'm a guy?

(Actually, this is the internet, and I'm a dog! Shh! :wink: )
 
  • #27
Ivan Seeking
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Originally posted by Tsunami
This is something that Ivan and I discuss quite a lot. You guys are just hard-wired to 'see' this stuff. I'm sick of being blind!

Don't get me into this...I still can't understand why everyone doesn't study physics. All other subjects are just a subset of physics anyway!
 
  • #28
Ivan Seeking
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Originally posted by Nereid
What makes you think I'm a guy?

Obviously Nereid is a guy's name.
 
  • #29
Nereid
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  • #30
Ivan Seeking
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Uh oh...I'm not up on my sea nymphs!

Please forgive my ignorance.
 
  • #33
Tsu
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Originally posted by Ivan Seeking
Don't get me into this...I still can't understand why everyone doesn't study physics. All other subjects are just a subset of physics anyway!
Yeah, yeah, yeah...
Nereid, I was using 'guys' generically. Would it help if I said 'youse guys'? (Like in 'HEY! Youse guys! What say we stop by Dauber's [Tav] catch a few beers, hey! ) 'Course, selfAdjoint might be the only one who understands this...:wink:
 
  • #34
selfAdjoint
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Originally posted by Tsunami
Yeah, yeah, yeah...
Nereid, I was using 'guys' generically. Would it help if I said 'youse guys'? (Like in 'HEY! Youse guys! What say we stop by Dauber's [Tav] catch a few beers, hey! ) 'Course, selfAdjoint might be the only one who understands this...:wink:

When I was in high school (1947-1951) "guys" could refer to a mixed gender group. Especially if you thought you were talking to a bunch of, you know, GUYS, and discovered there was a girl along too.
 
  • #35
Tsu
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Originally posted by selfAdjoint
When I was in high school (1947-1951) "guys" could refer to a mixed gender group. Especially if you thought you were talking to a bunch of, you know, GUYS, and discovered there was a girl along too.
It was the same when I was in high school in Wisconsin 20 years later. The part I thought YOU'D really understand was the 'YOUSE guys'. I never heard that term anywhere except your part of the country (Wisconsin, Minnesota, Michigan...does that term reach up into Canada, I wonder?). I always got a charge out of the Winsonsin 'accents' of my friends - they teased me unmercifully about my 'southern' accent [I was from CALIFORNIA! - where they got 'southern' I'll never know! Oh wait! I spent the summer in Texas before I started HS in Wisconsin! THAT'S where it came from! I'll be... I'm just a magpie when it comes to accents... ]).

Nevertheless... I DO appreciate all the help given by 'youse guys'(AND GALS)! Yer TOPS! Thanks BUNCHES!
 

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