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Astrophysics and Cosmology - Discuss the Universe here

Started by Agent : Orange, October 16, 2013, 09:02:47 PM

Quote from: valdez on December 07, 2013, 06:52:43 AM
      So I was watching some videos on the possible shapes that our universe may have, and I came across the concept that since light from a star beams out in all directions a star close to us, say five light years, would be seen in the sky as it was five years ago, but the light from that same star would be zooming out towards the other end of the universe taking a zillion light years to hit us from the other side of sky and so we would see two stars in the sky that are actually the same star at different times in its history.  As if life ain't mean enough.


or something to that effect

There are many kinds of these "hall of mirrors" effects that nature could play on us if she is spiteful. Not sure how seriously they are considered nowadays as there are now precise enough measurements that would rule out self-intersections anyway. But a few years ago there was a lot of speculation about these kinds of universes and all of it was fascinating. Look here for a good popular article (http://cosmos.phy.tufts.edu/~zirbel/ast21/sciam/IsSpaceFinite.pdf).

zeebo

Quote from: valdez on December 07, 2013, 06:52:43 AM
So I was watching some videos on the possible shapes that our universe may have...

I giggled when I first heard Michio Kaku say that the farthest point from you in the universe may be the back of your own head.  ???


area51drone

Quote from: zeebo on December 12, 2013, 01:11:20 AM
Ok, some of these are pretty awesome.

http://www.buzzfeed.com/donnad/40-breathtaking-nebulas

Definitely.  I wish they would explain the colors though - so many nebulas are colorized based on various things that you never really know what you're looking at.   It would be neat to see all these in just flat out visible light.   I like that rotten egg one the best, I think.

A few interesting stories out this week.

There may be systematic problems with the results from the Planck satellite. Turns out that if you remove one specific frequency then the Planck results and the older WMAP results match up nearly exactly, meaning the standard cosmology does even better than one might expect from Planck. If so this means that much of the arguments for the "anomalies" that are pointed to from Planck may not have a solid foundation. This is surprising and may be quite newsworthy in the next few weeks. The results between Planck and WMAP only vary by a few percent but that is quite important when every tiny detail counts.
http://www.nature.com/news/cosmologists-at-odds-over-mysterious-anomalies-in-data-from-early-universe-1.14368

A new holographic principle found that maps high dimensional gravity onto low dimensional quantum field theories without any gravity. So this means you can solve specific kinds of high dimensional gravity problems in a much simpler low-D quantum theory. Then the question is if these types of mapping can be done for other space-times, is it possible to do something similar for our 4D universe? Of course the article goes further and implies this is already proven, it is not - but the new results hint there might be more interesting developments in this direction. Maybe the universe is really like a hologram....?
http://www.nature.com/news/simulations-back-up-theory-that-universe-is-a-hologram-1.14328

Wish I could post more often but I am still swamped with stuff to do.

aldousburbank

Quote from: Agent : Orange on December 16, 2013, 12:12:00 PM
A few interesting stories out this week.

There may be systematic problems with the results from the Planck satellite. Turns out that if you remove one specific frequency then the Planck results and the older WMAP results match up nearly exactly, meaning the standard cosmology does even better than one might expect from Planck. If so this means that much of the arguments for the "anomalies" that are pointed to from Planck may not have a solid foundation. This is surprising and may be quite newsworthy in the next few weeks. The results between Planck and WMAP only vary by a few percent but that is quite important when every tiny detail counts.
http://www.nature.com/news/cosmologists-at-odds-over-mysterious-anomalies-in-data-from-early-universe-1.14368

A new holographic principle found that maps high dimensional gravity onto low dimensional quantum field theories without any gravity. So this means you can solve specific kinds of high dimensional gravity problems in a much simpler low-D quantum theory. Then the question is if these types of mapping can be done for other space-times, is it possible to do something similar for our 4D universe? Of course the article goes further and implies this is already proven, it is not - but the new results hint there might be more interesting developments in this direction. Maybe the universe is really like a hologram....?
http://www.nature.com/news/simulations-back-up-theory-that-universe-is-a-hologram-1.14328

Wish I could post more often but I am still swamped with stuff to do.
Yeh, figure this shit out for us all will you?


aldousburbank

Quote from: Agent : Orange on December 16, 2013, 12:24:47 PM
AB!! How's south of the border treating you?
Went South, came back North, heading South again next week after hogtying a few loose ends at the compound.  Mexico is waiting while I finish getting my ya yas out in the Sonoran Desert for a few weeks.  I have precious grandaughters to spend time with, and my momz.
Life is short.  It's a big universe.  I still have a hard time not posting around here when I should be re-packing my bags and such.  But the woodstove requires another log and I'm probably going to watch it burn...

Quote from: aldousburbank on December 16, 2013, 12:43:56 PM
Went South, came back North, heading South again next week after hogtying a few loose ends at the compound.  Mexico is waiting while I finish getting my ya yas out in the Sonoran Desert for a few weeks.  I have precious grandaughters to spend time with, and my momz.
Hey, enjoy! Happy holidays and all the best and all that stuff.


area51drone

Quote from: Agent : Orange on December 16, 2013, 12:12:00 PM
A few interesting stories out this week.

There may be systematic problems with the results from the Planck satellite. Turns out that if you remove one specific frequency then the Planck results and the older WMAP results match up nearly exactly, meaning the standard cosmology does even better than one might expect from Planck. If so this means that much of the arguments for the "anomalies" that are pointed to from Planck may not have a solid foundation. This is surprising and may be quite newsworthy in the next few weeks. The results between Planck and WMAP only vary by a few percent but that is quite important when every tiny detail counts.
http://www.nature.com/news/cosmologists-at-odds-over-mysterious-anomalies-in-data-from-early-universe-1.14368

A new holographic principle found that maps high dimensional gravity onto low dimensional quantum field theories without any gravity. So this means you can solve specific kinds of high dimensional gravity problems in a much simpler low-D quantum theory. Then the question is if these types of mapping can be done for other space-times, is it possible to do something similar for our 4D universe? Of course the article goes further and implies this is already proven, it is not - but the new results hint there might be more interesting developments in this direction. Maybe the universe is really like a hologram....?
http://www.nature.com/news/simulations-back-up-theory-that-universe-is-a-hologram-1.14328

Wish I could post more often but I am still swamped with stuff to do.

Great quote at the end of the first article .. "“Precision cosmology is hard; accurate cosmology is even harder.”    I like how the one team is saying the 217ghz data needs to be thrown out because the other frequencies match up to what they expect.   Typical scientists.    I'll bet you 2-1, Agent, that the data is fine and they need to start thinking out of the box to explain what's going on.    The *real* question to me is what do the differences mean?  The article didn't really go into that at all, and nor did you!  :)

As for the second article, this is interesting, but read the last two paragraphs and this is kind of a big let down.   I have a thought for you though.  What's to say there aren't infinite dimensions?   

I really want to know what it takes to start understanding some of these theories on a mathematical level.   I go to read much lower level stuff on Wikipedia, and immediately you are thrust into equations where you're like "hey, where did they get that variable, or how was that derived?"   And then you're on to learning 50 other things to just try to truly understand what one equation means.   I want to start from the bottom and work my way up.   Someone tell me, please, what is the path?   Algebra -> Geometry -> Trigonometry -> Calculus -> Vector Analysis ?? -> Differential Equations ?? -> Topology ??

Quote from: area51drone on December 16, 2013, 11:09:36 PM
Great quote at the end of the first article .. "“Precision cosmology is hard; accurate cosmology is even harder.”    I like how the one team is saying the 217ghz data needs to be thrown out because the other frequencies match up to what they expect.   Typical scientists.    I'll bet you 2-1, Agent, that the data is fine and they need to start thinking out of the box to explain what's going on.    The *real* question to me is what do the differences mean?  The article didn't really go into that at all, and nor did you!  :)
They're not saying the 217 ghz data need to be thrown out because they disagree with what they expect. They're saying the analysis and data reduction might not be right, that there's a systematic effect which is problematic for these data and are skewing the results. Then it happens to be that when the 217 ghz observations are excluded, all of the others give us back results which are closer to the WMAP data. That is an interesting result.

It means that the "anomalies" might not be real but artificial, problems caused by the data reduction procedures. The data may have been incorrectly handled in the first place. I should say that the difference only comes out to a few percent but again that's enough of a margin to separate "precision" and "accurate" cosmology. Here's a great brief review of the Planck anomalies from the ESA: http://sci.esa.int/planck/51551-simple-but-challenging-the-universe-according-to-planck/
Now if this is a problem with the analysis then I'd expect the CMB "cold spot" to make it through unscathed because that was also noted in WMAP. But we shall see what happens in time! What we really need is another set of deep and high resolution CMB observations to put this controversy to rest. I expect in the next few weeks the Planck team will re-analyse their data independently and respond to this criticism. It will be interesting to see what they have to say about the 217 ghz maps especially when they noted problems with them in the first place on release of their data.

And, as for thinking outside the box, that's exactly what the community has done since the data were released, there has been a ton of chatter about new models for inflation and the significance of the anomalies from Planck and how to deal with them, their implications, etc etc. So that's why this is a bit of a surprise, it may be that the weirder models for inflation are still on the table. The Planck data wiped out a lot of interesting ideas.

Quote from: area51drone on December 16, 2013, 11:09:36 PM
What's to say there aren't infinite dimensions?   
Well if you're talking about physical dimensions then as long as there are only four large ones in that scenario then maybe it's possible. Without any observable consequences anything's possible. But there should be some consequences of this, like how many particles there are (ie how many independent mods of vibrations exist for strings) and other such tests. But until we can reliably observe those kinds of things who's to say.

If you're talking about mathematics, standard quantum mechanics is already formulated in a state space with infinite dimensions called Hilbert space (http://en.wikipedia.org/wiki/Hilbert_space), and it's possible to make extremely accurate predictions of the real world with it. Whenever quantum mechanics contains continuous quantities like momentum and position (as opposed to degrees of freedom like spin, which have a finite number of states) you need this kind of language.

Quote from: area51drone on December 16, 2013, 11:09:36 PM
I really want to know what it takes to start understanding some of these theories on a mathematical level.   I go to read much lower level stuff on Wikipedia, and immediately you are thrust into equations where you're like "hey, where did they get that variable, or how was that derived?"   And then you're on to learning 50 other things to just try to truly understand what one equation means.   I want to start from the bottom and work my way up.   Someone tell me, please, what is the path?   Algebra -> Geometry -> Trigonometry -> Calculus -> Vector Analysis ?? -> Differential Equations ?? -> Topology ??
I don't know that I can suggest a single path to take, all of that stuff is useful depending on what you want to do with it. In my first year undergrad I took calculus, vector geometry and linear algebra. So maybe I would recommend starting with those? Mathematics is one field where the higher up you go the more the lines between it's sub-disciplines are blurred.

Quote from: area51drone on December 16, 2013, 11:09:36 PM
Someone tell me, please, what is the path?   Algebra -> Geometry -> Trigonometry -> Calculus -> Vector Analysis ?? -> Differential Equations ?? -> Topology ??

First, avoid DeVry University.

Har har.

But seriously, I recommend kicking back and relaxing with this fun filled tome:

A World Without Time by Palle Yourgrau, a book about the relationship between Einstein and Gödel and various mathematical shenanigans that ensue.

I think it could be a great catalyst on some subconscious level as to how to proceed in your search. I was laughing throughout the book (though others I recommended it to were unable to get into it.) But judging by your posts, I am confident you possess the proper gears and cogs to appreciate it more than some of the jackasses (no offense!) I hang out with...

(burp)

((Anytime I need to get out of jam, I simply say "no offense." I find myself using it more and more all the goddamned time.))

www.calculatorcat.com/moon_phases/phasenow.php

area51drone

Quote from: Camazotz Automat on December 17, 2013, 12:27:38 AM
A World Without Time by Palle Yourgrau, a book about the relationship between Einstein and Gödel and various mathematical shenanigans that ensue.

Thanks, I'll check that out.

area51drone

Quote from: Agent : Orange on December 16, 2013, 11:53:16 PM
I don't know that I can suggest a single path to take, all of that stuff is useful depending on what you want to do with it. In my first year undergrad I took calculus, vector geometry and linear algebra. So maybe I would recommend starting with those? Mathematics is one field where the higher up you go the more the lines between it's sub-disciplines are blurred.

Well I think even understanding how Einstein's derived his equations is a good start.  I'm sure its out there, I just need to plow through it.    I took calculus my first year undergrad, and then the following years I took linear algebra, differential equations, vector analysis, abstract algebra and number theory.   I may have taken a couple more courses that would qualify as math courses in my comp sci program as well (discrete math comes to mind), but I did this program in high school called running start that let me skip a year so I couldn't fit everything in that I wanted in the 3 that I was in college.    So a lot of the basics are floating around in my head, I just have to brush up on it and then head down whatever path can take me to the next step I guess.   Certainly what you say is true and I'm sure there are applications of nearly all math in physics.    How about recommending some undergrad physics textbooks, or a spell out a quick list of physics course titles for undergrads perhaps so I can research what profs use for their textbooks?   Since I only took the 3 part physics course required for the CS program, I never knew what came after.  The course texts we used (and I still have) are a 2 volume set "Physics" by Resnick, Halliday and Krane.  Looking briefly through it now (after all these years) I'm surprised to find at least a chapter on relativity in them so I guess that's a starting point.

Quote from: area51drone on December 18, 2013, 03:04:21 AM
Thanks, I'll check that out.

You're welcome. Don't draw any conclusions based on the extremely low prices it goes for on Amazon, both new and used.

It's a damn shame that such a fine book is relegated to backwash prices when E L James' Fifty Shades of Crap (No offense, E L) and Dan Brown's various Semen Demons (No Offense, Dan) sell in the millions of copies.

Back to lurker mode for me.

I must digest the holidays.

Quote from: area51drone on December 18, 2013, 03:18:19 AM
How about recommending some undergrad physics textbooks, or a spell out a quick list of physics course titles for undergrads perhaps so I can research what profs use for their textbooks?   

I like the Physics textbooks by Chabay/Sherwood (Matter and Interactions, Electric). Older editions are available for a few dollars and I like their approach.
I think I four of five different Physics' texts and Chabay is my favorite. It has an emphasis on simple programming to solve problems as well. I cracked these open recently because I am looking to develop some google glass apps and need to process the motion of moving objects.
Not a traditional textbook, but I think When Least is Best: How Mathematicians Discovered Many Clever Ways to Make Things as Small (or as Large) as Possible by Paul Nahin is really great for putting many things in context.

valdez

Quote from: Camazotz Automat on December 17, 2013, 12:27:38 AM
A World Without Time by Palle Yourgrau, a book about the relationship between Einstein and Gödel and various mathematical shenanigans that ensue.
Quote from: area51drone on December 18, 2013, 03:04:21 AM
Thanks, I'll check that out.
Maybe I will too.  I've heard that you can't really get this stuff unless you get the math.  Those supposed eleven dimensions of string theory are, according to what I've read, only seen and revealed in the math.  But who has time for that?  Sadness.  Here’s a cool video of the Chinese "Jade Rabbit" thing landing and the rover in motion, without any annoying comments from...commentators.
 


area51drone

That's a cool video, it's surprising how hard it looks like it lands, unless that was sped way way up.   Also, WTF is with the sound?  How can there be any sound unless I guess it's vibration within the machinery itself.     I wish there were some altitude readings on it as it landed too, that would have been cool.

I don't care what anyone says about the Chinese.. good for them that they're making efforts to go to the moon and hopefully beyond.  Someone needs to do these things.   

That book by Haliday is very good to start. For an intro to electromagnetism find the book by Griffiths (I think with the same name, "Griffiths EM textbook" in google will probably do it), that goes through Maxwell's laws and into Special Relativity. The book is great and you can pretty much just pick it up and read it straightaway. Great review at the beginning too. Then afterward on to Ray D'Inverno's Introduction to General Relativity, he goes over differential geometry and tensor calculus in the first section and onto the meat of GR in the second part including the Schwarzschild solution, and the last part he devotes to cosmology and derives the Friedmann equations and talks about Einstein's cosmological constant. You can usually find D'Inverno for a pretty good price on Amazon. I love both of the Griffiths and D'Inverno books. Make sure to work through the problems too otherwise you won't really get it. For starting out these books are excellent.

I realize I am dumbing down this thread, but am I the only one who thinks that it would be extremely funny for NASA to quickly send a rover to the moon for the sole purpose of messing with China's rover? Perhaps deposit some cow bones in the area for China to discover...

The outrage...

The suspense...

The endless pranks...  and the hilarity born.... on...

Rover Wars

area51drone

According to Richard C Hoagland, bones are already there.   That's why the Chinese landed at 19.5º, to find Data's head.

Quote from: area51drone on December 20, 2013, 01:56:30 AM
According to Richard C Hoagland, bones are already there.   That's why the Chinese landed at 19.5º, to find Data's head.

There's a Family Guy joke in there somewhere... 

Oh! here it is:

Peter: Geez, this reminds me of when I had lunch at the Golden Rooster Egg last week:

Peter:  Uh, yeahhhhh...  I'll take the Wonton Data Head Soup with the Sweet and Sour Face on Mars... And a little Noory sauce...

Waiter:  You wanna try Garlic Lunar Cow Bone with that?

Peter:  No.  I do not believe in Garlic Lunar Cow Bone.  I do not. That is a hoax. A conspiracy by NASA.

Waiter: Okaaaaay.  You want fork or chopsticks with that?

Peter: What? You think I'm an animal? Fork, please. Don't get smart with me, Hop Sing, or I will march right out of here and take my business to the Iron Horse Scrotum. Don't  f&%$ with me, Hop. Do not f&%$ with me.

Waiter: You prepay.

area51drone

So I bought a CMOS CCD for my microscope that came in today.  It looks like it might work with my telescope... very hopeful and now I can't wait for these clouds to go away.

Quote from: area51drone on December 21, 2013, 01:04:42 AM
So I bought a CMOS CCD for my microscope that came in today.  It looks like it might work with my telescope... very hopeful and now I can't wait for these clouds to go away.
Nice!!

zeebo

Quote from: valdez on December 18, 2013, 06:01:38 AM
...I've heard that you can't really get this stuff unless you get the math.  Those supposed eleven dimensions of string theory are, according to what I've read, only seen and revealed in the math....

I have a theory that people who get higher math have a kind of visual ability to "see" the math.  I base this on my limited talent for visualizing the simpler math I use for data processing programming (2d grids, sets, simple algebra etc.)  When it comes to advanced calculus, analytic geometry, linear algebra etc. I just cannot visualize what all those mathematical symbols are doing.  That's why I'm not an astrophysicist or 3d game programmer.  And 11 dimensions?  Frig I can barely handle 2.

Quote from: zeebo on December 22, 2013, 06:04:27 PM
I have a theory that people who get higher math have a kind of visual ability to "see" the math.  I base this on my limited talent for visualizing the simpler math I use for data processing programming (2d grids, sets, simple algebra etc.)  When it comes to advanced calculus, analytic geometry, linear algebra etc. I just cannot visualize what all those mathematical symbols are doing.  That's why I'm not an astrophysicist or 3d game programmer.  And 11 dimensions?  Frig I can barely handle 2.
No one can *really* handle more than that. It's a necessity for survival that we have an intuitive grasp for three dimensional thinking, but that is not a law of nature. Mathematicians just have a solid intuition of how they expect things to work out but are often surprised when extending basic ideas into higher dimensions. This is especially true in physics (see http://en.wikipedia.org/wiki/Kaluza%E2%80%93Klein_theory)

Quick Karl

I am not sure that I would ever have believed such a lucid and informative discussion could ever be taking place on an internet discussion forum had I not seen this with mine own eyes. This is the first thread anywhere, that I have read from start to finish.

Excellent!

Thank you.

area51drone

Quote from: Quick Karl on December 23, 2013, 11:36:51 AM
I am not sure that I would ever have believed such a lucid and informative discussion could ever be taking place on an internet discussion forum had I not seen this with mine own eyes. This is the first thread anywhere, that I have read from start to finish.

Excellent!

Thank you.

Well that's something to say for Agent Orange, and sheer embarrassment for me.

Quick Karl

Quote from: area51drone on December 23, 2013, 11:40:21 AM
Well that's something to say for Agent Orange, and sheer embarrassment for me.

Don't be shy A51, you're no Forrest Gump yourself. The discussion would not be what it is without your participation and contributions!

Quote from: Quick Karl on December 23, 2013, 11:36:51 AM
I am not sure that I would ever have believed such a lucid and informative discussion could ever be taking place on an internet discussion forum had I not seen this with mine own eyes. This is the first thread anywhere, that I have read from start to finish.

Excellent!

Thank you.

Hey Karl, good to hear from you.

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