Loop Quantum Gravity and the Big Bang

[yevaud]

<b>What happened before the Big Bang?</b><br /><br />What happened before the Big Bang? Does that question even make sense?<br /><br />When astronomers think about the Big Bang, in general they don’t actually mean that one singular moment when the Universe burst into being. It’s really the name given to the model used to describe what happened an infinitesimally thin slice of time after that moment.<br /><br />The problem is, right at that moment, at T=0, our laws of physics… well, they stall out. You wind up dividing by zero a lot, which causes a lot of headaches. You get things like zero volume and infinite density of matter and energy. It’s not that this moment didn’t exist physically, or that something impossible happened, it’s just that the math we currently use can’t describe it. And let me be clear: what happened after that one moment we can model fairly well. We may not have a complete picture, and the model may yet be supplanted (more on that in a moment), but we have a relatively (har har) good grasp on how the Universe behaved after T=+0.0000000000000…1 seconds. But at T=0, fuggeddaboutit. And T<0? The way the math works, that question doesn’t even make sense.<br /><br />The basic trouble is that Einstein’s relativity gives us a good description of some things (large scale gravity, for example), and quantum mechanics tells us about other things (how particles behave), but no one has ever successfully combined the two, and they must be combined to understand that First Nanonanonanonanonanosecond. Einstein himself tried, and failed.<br /><br />It’s possible, now, that this has changed.<br /><br />Martin Bojowald, an assistant professor of physics at Penn State University, may have broken through this barrier for the first time. He is working on a theory called Loop Quantum Gravity, and it combines relativity and quantum mechanics. Using this new math, something amazing happens: at T=0, the volume of the Universe is not zero, and the density is <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[bdewoody]

I used to think I was half way smart but when I start reading about quantum mechanics, string theory, membrane theory or watching physicists write out those long equations that are supposed to verify one theory or another I begin to feel my brain has a lot missing.<br /><br />Is there a quantum physics for dummies book that explains this stuff for people who stopped at calculus? <div class="Discussion_UserSignature"> <em><font size="2">Bob DeWoody</font></em> </div>

 

[docm]

<br /><b><font color="yellow">Taking the Quantum Leap: The New Physics for Nonscientists</font></b>/a> by Fred Alan Wolf (theoretical physicist).<br /><br />Also;<br /><br /><a target="_blank" href="http://www.amazon.com/exec/obidos/ASIN/0691024170/internetinfidelsA/"%20target="_blank">Feynman,%20"QED""><font color="yellow"><b>QED: The Strange Theory of Light and Matter</b></font>/a> by Richard Feynman. <br /><br />QED = quantum electrodynamics, a relativistic field theory of electromagnetism.<br /><br />Look for the 2006 edition. According to Feynman, to learn QED you have two choices: you can go through seven years of physics education or read this book. Humble man that Feynman <img src="/images/icons/wink.gif" /><br /><br />That or you can watch the lectures online (RealMedia files) at the Vega Science Trust here;<br /><br /><a target="_blank" href="http://www.vega.org.uk/video/series/5">http://www.vega.org.uk/video/series/5<br /></a></a> <div class="Discussion_UserSignature"> </div>

 

[yevaud]

Well, it <i>is</i> very interesting, true. Usually, I see people go off on long, involved calculations that are terribly fraught to do. Yet some of the simplest descriptions of physical behavior are quite simple, elegant even. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[SpeedFreek]

Well, it's a solution along the lines that have mooted for years (a cyclic universe), but now we might have a means to test it. <img src="/images/icons/smile.gif" /><br /><br />It has always seemed one of the neatest solutions to me, that the beginning of one universe might come from the end of another. It might answer so many fundamental questions whilst posing an even deeper fundamental level to question, and who knows, one day we might actually solve the whole causal paradox! <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[yevaud]

<i>one day we might actually solve the whole causal paradox!</i><br /><br />Causality and Cyclical Universes make me wonder just how discreet each manifestation of our Universe is relative to another.<br /><br />E.g., does a "new" time occur each time a new Universe is created? Everything reset?<br /><br />Sorry, just a vagrant thought. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[MeteorWayne]

{music}<br />Tiiime, is on your side, yes it is...<br />{/music} <br /><br />Oops, sorry thought this was another thread <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[yevaud]

<img src="/images/icons/tongue.gif" /><br /><br />Damnit. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>