Well I was offsite this weekend attending the American Physical Society "April" meeting in Washington, DC. The "April" meeting is one of the two main APS annual meetings and it is at this meeting where particle physics, gravitation, astrophysics, cosmology and nuclear physics are the main topics being presented. It just turns out this year, due to
hotel scheduling issues, that the April meeting is held in January. The APS "March" meeting, which deals primarily in condensed matter physics and atomic physics, is still actually held in March and this year will be in New Orleans. Um, too bad, I am not that interested in condensed matter because New Orleans could be fun.
But here I am in Washington, DC, not to protest anybody, but just to catch up on the latest events and continue on my physicist wannabe journey. I woke up this morning to find a light dusting of snow outside the hotel window, but since the conference meeting was held in the hotel, I didn't mind the snow. In fact, I sort of missed being in DC and riding the metro and enjoying the sights and I could remember how when I was actually working for a living, I would end up in DC 5-6 times a year for various work related meetings and conferences. Now, however, the rest of my unpaid staff, Resident Astronomer Peggy and Astronomer Assistants Ruby, Danny and Willow remained at the observatory to keep things running.
There were too many interesting presentations and discussions for me to list or mention them here. I had high hopes of blogging about daily happenings over the four days, but I was so tired by just trying to keep up with what was being discussed that I ran out of energy at the end of the day. In addition, the hotel where the conference was held only offered free wifi in the lobby and the conference area, so I couldn't blog very easily unless I left my room. But, I do want to mention two main points about a breakthrough in my understanding of general relativity, black holes, thermodynamics, gravity waves and rubber ruler paradox, quantum information theory and the fundamental aspect of nature that is now beginning to appear as an integrated picture of reality where we are almost at the point in time where the complete description of reality can be derived from general relativity principles.
So, where to begin this discussion, which really was an epiphany for me, which began with my finally getting together again with Searching for Gravity Waves, Dr. Gary, who I first met two years ago at the APS meeting in Baltimore. We had an instant connection, in that we were both on separate, by closely aligned journeys, he by adding on top of his medical career, and me adding on top of my engineering career, an overriding interest in developing a much better and deeper understanding of physics and how physics presents one of the most fundamental descriptions of the nature of our world and universe. He has also turned his interest in analyzing gravity waves into actually helping do some signal analysis on detector signals. Pretty neat Gary!
I first posted about the rubber ruler paradox associated with detecting gravity waves in the May 2, 2016 post, and remember trying to resolve the issue and even asked Dr. Gary about the issue too. He explained the issue, but it didn't quite seep into my brain and I couldn't get the image of a passing gravity wave as causing a force on particles, which would then distort and change shape and thereby even my ruler would bend and stretch, as if it were made out of rubber and therefore my measurement of the gravity wave would show no measurable effect. Wrong!
I had even earlier asked another physicist author, Dr. Janna Levin, after she signed a copy of her book for me, if she thought that the gravity wave effect, if the wave were strong enough, would someone be able to actually hear the wave as it passed by. She said yes, it could be in the right frequency range and it seems possible, and again, I couldn't get the rubber ruler paradox out of my head. If you want to follow up on her book on black holes, check out my April 13, 2016 post.
Well, Dr. Gary kindly accepted the challenge of bringing me alone on my physics education and over the course of a couple of meals, with wine and martinis, one at one of my favorite DC restaurants, Lebanese Taverna, I finally got it. Dr. Gary's analogy of the gravity wave, as "inviting the test particles or objects to move, not by a force, but by an invitation", that I finally got it. The gravity wave is not a force per se, but a distortion and stretching of spacetime and if the test particles are not constrained by other forces, then the space between them will be stretched and compressed as the wave passes by. It is not as if they are forced, but just "invited' to move as the space changes, just like we are "invited" to fall toward the center of the earth by gravity. We are invited but we do not fall through the earth because we are restrained by other forces, notably the electromagnetic forces that support our feet on the surface. Likewise, any ruler in the path will not be distorted or stretched because the electromagnetic forces keeping its structure together are much more powerful than the weak gravity wave. The ear drum on the other hand is small, lightweight and only lightly constrained, and actually built to respond to small forces, and when a gravity wave, of the right amplitude, much stronger than the ones currently detected, would cross its path, the eardrum would move slightly due to the "invitation" It is not a force per se, but just the natural path an object would follow in a gravitational field, that is on what is called its natural geodesic, which is defined by the surrounding gravitational field caused by the energy and mass there.
Ok, I finally got it. Thank you for that discussion, and everything else, Dr. Gary. Also, there was the recognition that the effects of gravity waves and the effects of the expanding universe are already contained in Einstein field equations of general relativity. The expansion of the universe as described by the equations as being due to the relative amounts of matter, dark matter, radiation and dark energy, just flows from the equations. Normal objects like galaxies that are bound together by gravity and ourselves, bound together by strong electromagnetic forces, will not be disturbed by the expanding universe until a much further in the future. Then, as the universe starts accelerating faster and faster, even the strong electromagnetic force will not be able to keep us together.
Another good idea from Dr. Gary, after I complained about what we each recognized about studying general relativity, is the lack of a more gentle textbook to help the new student and physicist wannabe, find their way into better understanding, he recommended this textbook by Peter Collier. Well, I picked up a copy and yes, indeed, it makes the whole subject much easier for the senior student or physicist wannabe who is not part of the normal school curriculum.
|This is a fantastic introduction to general relativity, much easier than most texts|
Then with Hawking and Beckenstein formulation of black holes having a temperature and capable of evaporation and potential loss of information, the connection to information theory is established. Again, why is this the case?
Any, Professor Bousso went on to discuss the generalized 2nd law of cosmology, with the same general features of that law in thermodynamics. Now I used to work with the 2nd law of thermodynamics in studying efficiency of steam turbines and fuel cells, but why and how thermodynamics should have anything to do with gravity and general relativity was never on my radar. And yet, this is just what Bousso was saying that thermodynamics, as well as an understanding of other laws operating in the universe can almost be derived by examining the precepts of general relativity alone. How is gravity and entanglement connected and thermodynamics derivable from general relativity. I don't know, but this field is just really getting going and it seems that the answer and tying of gravity and quantum mechanics together is really making a lot of progress. What will the future bring? I guess I'll just keep my bags packed for the next APS April meeting!
Since black holes are central to this fantastic integration of these concepts, one other particular point about black holes that I found interesting was brought up in several sessions and that was the mechanism by which black holes can exhibit the very powerful jets of energy that flow out from the poles of the rotating black hole and these jets are extremely bright and can be seen across very large distances. The effect by which these magnetic jets form seems to be mostly explained by something called the Blandford-Znajek effect. I don't quite understand all of it but I found a Wikipedia article that explains more of the details. Check it out at:
Finally, I should mention something about the often emotional discussion that several speakers and much audience support was apparent was the recent travel ban on folks entering the US from a half dozen Mideastern countries. I guess it was just too much to hope for not much discussion of politics, but the issue was certainly of importance. While it was often described as a ban on Muslims, a more balanced review found that the ban was only temporary, and driven by a review of terrorist vetting practices, even though the way it was introduced over the weekend was somewhat botched. Regardless of the specific events over the weekend, the main important point to keep in mind is that the study of physics is truly an international venture. Many large teams, often in the thousands, are necessary to make the progress of recent discoveries, such as those for LIGO and at the LHC. The best and brightest students from around the world come here to the US to study and do research. The world is better off because of this collaboration. Now if only the rest of the political world could get along.
Until next time,