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#43436 - 05/01/12 02:06 AM All about energy
Bill Offline
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Registered: 12/31/10
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Loc: Oklahoma, USA
In "The energy that holds things together" Physicist Matt Strassler in his "Of Particular Significance" blog discusses how things are held together by the energy of the fields that make up the universe. It gives a slightly different view of things from what I am used to seeing. Good stuff.

Bill S. He mentions potential energy, but doesn't want to call it that because the usual explanation is much different from the modern description.

Bill Gill
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#43442 - 05/01/12 07:06 AM Re: All about energy [Re: Bill]
Orac Offline
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I have seen several lectures and discussions from Matt and I will leave my discussion till when he finishes.

However I will make two comments already.

Note the title "the energy that holds thing together" and my question posed to you is how do you know that .... I mean why the direction???.

A few people in the comments have already picked up the problem

Originally Posted By: aa. sh. | April 30, 2012 at 11:38 AM

As the minus sign must be related to a fixed agreed-upon datum , what is the datum with which comparing binding energy we find that it is less / opposite / the other way around / ÖÖetc.from that datum ?



I was interested how he was going to bridge gravity into this theory but it appears I am to be very disappointed.


Originally Posted By: Matt Strassler | April 30, 2012 at 3:50 PM


Not heretical in the slightest. Itís standard fare; every university in the country with a particle physics program has a Quantum Field Theory course.

Space-time isnít quite the field itself ó this is a tricky point. Thatís why I glossed over it. The fields in gravity are a bit more complicated than that. But I donít think I want to try to answer this clearly now.

In flat and unchanging space, gravity doesnít break Lorentz symmmetry at all.

Of course, the universe is expanding, and that defines a preferred sense of time (in the part of the universe that we can see, at least). And that does mean that the gravitational fields in our universe do, on the largest distance scales, break Lorentz symmetry, yes. And no other fields break Lorentz symmetries on the large scale, no.

But the answer to your last question depends upon exactly what you meant. Globally across the universe, nothing but gravity breaks Lorentz symmetry (at least no one has ever detected of any other source of Lorentz breaking.) In small regions thereís all sorts of breaking by all sorts of things. For instance, there are stray magnetic fields in all sorts of places around the universe, and so locally those break Lorentz symmetry. And hey, even the earth breaks Lorentz symmetry (thatís why up is different from down, for instance, when youíre near the earth.)


So I am going to be left with the rather ugly situation at least for me with gravity.

No science journey is not worth the trip so I encourage people to stay with the series because it is a fairly modern spin on Quantum Field theory.


Edited by Orac (05/01/12 07:08 AM)
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