Wednesday, September 24, 2014

BICEP2 + Planck + Foreground = Good Physics

     The Planck CMB polarization paper came out this week and its results were not good news for the BICEP2 team as shown herehere, and here. I'd commented on the BICEP2 result earlier here, Basically saying that this is how science gets done.  Now we have the future to look forward to and more results coming in at other frequencies and maybe better energy resolution so hopefully in the future we will know about primordial gravitational waves.  Again may you live in interesting times!

     What only gets briefly mentioned is that what we do have is really good data on galactic dust and the galactic magnetic field.  So people who study that should be very happy.  Again what is one research groups hindrance is another groups prize.  This happened else where in physics.  At the LHC looking for the Higgs boson its signal sits on top of a large background.  Understanding this background is important so that you can be confident in your Higgs signal.  Understanding this background means understanding the physics that gives rise to this background and here understanding and computing QCD processes becomes important.  Hence you have large groups that look at all the QCD processes that can contribute to this background and then calculate their cross sections and then see how these match the background.  So here you get more understanding and conformation of the Standard Model in trying to understand the background underneath your Nobel prize winning discovery of the Higgs boson.

    In my own research years ago in looking at the excitation of giant resonances in nuclei excited with inelastic proton scattering, the resonances sat on top of a background.  One minimized this background as much as possible but it was still there and didn't go away.  That was because as we learned that background was there because there was real physics going on that caused this background.  The background was a real signal and not instumental problems.  The background as we determined was caused by quasifree scattering of the incident protons from nuclei in the targets.  The target nucleus being a collection of nucleons acted like a collection of nucleons sort of like a collection of pool balls racked up and we were hitting these pool balls and sometimes we were exciting the nucleons  in that manner instead of other nuclear processes.  This area of study led to other experiments studying this quasifree scattering.  So looking for one signal our background signal became interesting in itself.

     Funny how science moves ahead.

Tuesday, September 9, 2014

The Question of What is Now?

     One of the cool things about physics is that every now and then a question comes up and it makes you go "what a fascinating topics for physics to look into and I'm surprised I've not heard more about it".  One of those moments happened earlier this year when in the March 2014 issue of Physics Today there was a commentary by N. David Mermin entitled "What I Think About Now".  It is a fascinating article and when I read it I wonder about that I know I've thought about my moments of Now but never really thought about what the physics meaning of Now means.  I'm capitalizing Now in the ways Mermin does to point out the Now that is being discussed.  Now being your personal conscious feeling about your Now.   Physics treats  objects as just things that don't perceive a Now.  Objects are a rock or baseball or a proton..  Physics tries to understand what these objects are made of and the forces that they interact with and the understanding of these forces.  The objects perception of Now then gets into the area of consciousness and self awareness.     In Mermin's article he mentioned about Einstein's feeling of the Now which is the following:

Einstein said that the problem of the Now worried him seriously. He explained that the experience of the Now means something special for man, something essentially different from the past and the future, but that this important difference does not and cannot occur within physics. That this experience cannot be grasped by science seemed to him a matter of painful but inevitable resignation. 2

This would seem to say that Einstein thinks physics cannot describe the Now as experienced by the individual.. The personal, conscience, self awareness of  Now..  It reads to me that Einstein didn't think that consciousness could be understood by science. Interesting.  The idea of the Now in physics is fascinating.  In the September issue of Physics Today there are third letters about Mermin's  Now commentary they are here, here, and here.  The last letter has a reference to an arxiv paper about the physics of the Now.  Finally there is a reply by Mermin to these letters.  

     There seems to be two Nows.  One the physics Now of a point in spacetime described by its coordinates i and the worldline that the objects experiences in spacetime as described by the laws of physics.  Very impersonal and sounds like the stuff that physicists do. The other is the personal, psychological, conscience Now that physicists are beginning to seriously study as mentioned in an earlier post entitled Quantum Consciousness.  

    The personal Now has to do with self awareness.  Self awareness is an emergent process of your consciousness.  It is something your consciousness develops with time./Somehow and sometime, which is not understood, your brain and body become conscious but not self aware.You then do not know the concept of Now until you are self aware.  Because Now is a subjective experience of your  self aware consciousness.  Now becomes the present state in spacetime of your self aware consciousness.  You as a person.don't know of Now until that self awareness turns on in your consciousnesses.  Then you have a feeling of time.  That the world is changing and that you perceive that change and that is what we call rime or the flow of rime.  So your subjective idea of Now starts when you become self aware.  This is probably obvious to everyone..   

Tuesday, September 2, 2014

Quantum Weirdness

     What do I mean by quantum weirdness?  Its the observation of things that cannot be explained with the classical laws of physics and need to be explained or are the results of quantum mechanics that seem odd, strange or just plain weird.  Maybe quantum bizarre would be better word.  What effects or thing do I mean that are quantum weird?  Here are some examples:

Schrodinger's cat  This is the most famous cat in physics.  Also apparently Schrodinger owned a cat when he thought of his thought experiment in 1935 I think.  This is the paradox that can arise when one applies quantum mechanics to macroscopic sized objects in which we can not observe.  The paradox is that the state that describes the cat quantum mechanically has to have the cat both alive and dead at the same time.  This is because Schrodinger equation is linear so the most general solution is a linear combination of all the solutions.  This is also known as superposition.  It leads to a just weird situation.

Image without detecting light  Another article on the same experiment is here.  This is a recent experiment using entangled photons.  Entanglement can led to many weird quantum effect.  Basically using entangled photons physicists were able to make a photograph of an object where the entangled photons never were involved in the illumination or reflection from the object whose picture was taken.  The photons didn't see the object or have  anything to do with the object yet they could be used to make a picture.  Of course the picture was of a cat.  This is just plain weird.  Einstein called entanglement "spooky".

Quantum computing  Where in a qubit does the calculation take place in a quantum computer?  This has to do with superposition.

The uncertainty_principle can lead to many odd effects.

Wave particle just plain weird.  How a particle can both be a wave and a particle.

     You can probably think of other weird quantum effects, or in quantum mechanics things are different.  This quantum weird is something that all students of physics talk about partially because it is just plain weird.  Some people learn about quantum weirdness in reading about science in newspapers or other popular media.  Recently a meeting was held to help educate science journalists about quantum mechanics and some of its weirdness.  One of my favorite blogs Backreaction has a post about this meeting because blog author helped organize the meeting.

     One of the problems with quantum mechanics is that physicists don't really understand what quantum mechanics is trying to tell us.  Quantum mechanics has many interpretations.  The equations of quantum mechanics are well known its just what do they mean?  Some blog discussions about this are very illuminating on this subject.  One is in the blog quantum frontiers posted here.  This is written by John Preskill a physics prof at Caltech.  Another is posted by Sean Carroll here.entitled "The Most Embarrassing Graph in Modern Physics".  The graph mentioned is about a poll taken at a meeting showing that physicists can't agree on which interpretation of quantum mechanics is correct.  As is usual the comment sections of the posts are very educational..  I have also talked about the problems with quantum mechanics here.  This is one of my earlier posts and might be poorly written.