Well, there was just time this week to attend the OCA Astroimagers SIG before packing up the bags and driving to Santa Barbara for HartleFest at the Kavli Institute of Theoretical Physics (KITP) at the University of California Santa Barbara (UCSB).
So, I met up with Science Nerds and Theatre Impresarios, Scott and Sandy, for the OCA Astroimagers SIG in Costa Mesa, where OCA Dave Kodama led us through some practical considerations for the upcoming trip to Chile to observe the total solar eclipse on July 2, 2019. Dave presented many anecdotes of events from his previous eclipse tours. One story in particular was when observing from a hotel site, the hotel staff was preparing a huge bonfire in celebration of the eclipse. Fortunately, they were able to talk the staff out of doing that. Thanks for alerting us to some of the practical considerations, Dave!
It turns out that we will spend about four days in the Atacama Desert and will have a chance to visit some of the larger observatories there. In the map below you can see many observatories, just about an hour from the airport in Calama, including ALMA and the Event Horizon Telescope.
|Google Map showing some or the observatories in the Chilean Atacama Desert (Source: Palmia Observatory)|
Ok, so driving up to Santa Barbara is not quite as difficult as flying to Chile, but the drive through Los Angeles always takes a lot of extra time, but the drive up the coast is beautiful. The UC Santa Barbara campus is so beautiful and its location by the sea is so nice. This trip was for HartleFest, which was a celebration of Professor Jim Hartle's 80th birthday. The celebration and day of speakers illustrating his over 50 years of physics research was held at the Kavli Institute of Theoretical Physics (KITP).
|KITP at UCSB (Source: Palmia Observatory)|
Just a short couple of hundred feet walk up the sidewalk you can get a glimpse of the ocean. Better views were available close by but I only had about 5 minutes before the start of the session.
|View of the ocean just across the street from KITP (Source: Palmia Observatory)|
Now, I have never met Professor Hartle, other than maybe seeing and hearing him at a conference here and there, but his gravity textbook has been my goto source during my study of general relativity. I knew of his work with Stephen Hawking, but had no idea about the depth and breadth of his influence on the development of physics. So, it was very recently, that I decided that yes, I had to attend Hartlefest and hear more about his impact on physics. I was glad to be a guest there! I can only offer some brief summaries of key points of some of the several presenters making comments about the impact of Jim Hartle on the development of physics and probably missed some of the key points made by more experienced attendees.
|Stephen Hawking and James Hartle at a workshop in 2014 (Source: Quanta Magazine)|
Kip Thorne, who shared a Nobel Prize for work on LIGO, kicked off the session of speakers describing their interaction with Hartle. Kip interacted a lot with both Hawking and Hartle. During the long development of LIGO it was important to understand what the gravitational wave signal from merging black holes and neutron stars might look like and what information could be learned from observations.
|Nobel winner Kip Thorne shares some aspect of Jim Hartle's impact on physics (Source: Palmia Observatory)|
So, Hartle and Hawking had worked together to describe the gravitational effects near black holes and their environments. The interplay between the matter falling into the black hole and the angular momentum transfer under different conditions of black hole spin were just being understood or conjectured. The moon rises tides on the Earth and a black hole does sort of the same thing for material in orbit around the hole, but because of its spin, the tide raised occurs at a different phase than does the tide on Earth. Hartle and Hawking were able to work out and described some of these effects.
|Kip Thorne explains how, now after 50 years, Hartle/Hawking ideas can be observed (Source: Palmia Observatory)|
Professor Gary Gibbons, Cambridge, offered some other comments regarding 55 years with Jim Hartle. He described Hartle as one of those rare physicists that mastered the "twin peaks" of physics: General Relativity and Quantum Mechanics. It seems that in the modern study of astrophysics both disciplines must be integrated.
|Professor Gary Gibbons, describes Jim Hartle as expert in physics' twin peaks: GR and QM (Source: Palmia Observatory)|
At the lunch break, four members of our local science squad of physicist wannabes met up to share what we heard. It was great to see everyone, Dave, Ken, and Larry!
|Lunch break at HartleFest with physicist wannabes George, Dave, Ken and Larry (Source: Palmia Observatory)|
My other gravity and general relativity textbook that I go to is Sean Carroll, "Spacetime and Geometry: An Introduction to General Relativity", so I always look forward to hearing anything that Sean has to say because he always makes some interesting philosophical points along the way also. At Hartlefest, he spoke about Hartle's early work about entropy and complexity and how complexity arises in the universe after the big bang.
|Sean Carroll, Caltech, explores Hartle's ideas on origination of complexity (Source: Palmia Observatory)|
Jim Hartle's 2004 paper, "The physics of now" discussed a series of questions about time and what if meant by past, present and future and about how they are not defined in physics because the physical lays all seem to be time reversible and the future only means any thing because of the very special low entropy initial condition of our universe. He says that past and present and future really only make sense to what he calls "Information Gathering and Using Systems (IGUSes), by which he means beings like us or even just programmed robots.
Sean's presentation carries this idea further and asks how complex systems like IGUSes come about in the first place. You also see the famous shuttlecock diagram illustrating the no boundary evolution of the universe. Don't get confused by the shuttlecock illustration and think that their is some orientation to the expansion of the universe; it just shows the changing rate of expansion. The question is how the IGUSes arise in this big bang universe.
|Sean Carroll discusses where Hartle's IGUSes and complexity come from (Source: Palmia Observatory)|
|Sean Carroll compares entropy of the universe with mixing cream and coffee (Source: Palmia Observatory)|
So we see in the following slide the generalized concept of how complexity can arise in a system, reach a maximum and then fall back to zero at a later stage of the system. The blue line shows entropy continuously increasing, while the red curve shows complexity rising, reaching a maximum and then falling to zero.
|Sean illustrates how complexity rises and then falls, even as entropy continuously increases (Source: Palmia Observatory)|
So, Hartle summed up this whole history of the universe as going from simple, early, to complex in middle life, and back to simple again at the end.
|Sean shows Hartle's path from simplicity and back again at Hawking's 70th (Source: Palmia Observatory)|
So, how do we explain this rise and fall? Sean goes on to consider the mixing coffee example and uses a "coffee automaton" to explore how and why complexity can arise in a system where the rules of physics allow flow with positive time or negative time. It all has to do with a concept called "coarse graining." At a very low level, the laws of physics are completely reversible, and yet at a higher, more coarse grained vantage point we see complexity and the coffee automaton will allow us to explore under what conditions this can occur.
|Sean Carroll and apparent complexity and the coffee automaton at Hartlefest (Source: Palmia Observatory)|
Sean goes on to explain that by adding an alternative dynamics to the model it can generate the type of complexity that we are working for. He called this the "tectonic" model in that, I assume, that just like layers of rock and soil and continents, if you move whole layers in the simulation model, you get the complex behavior.
So, the results of the tectonic coffee automaton are shown below and you can see the blue line, representing some notion of complexity, rises and falls as the system of coffee mixes goes from the initial state to the final state. Pretty neat!
|Now the coffee automaton creates complexity with the tectonic model (Source: Palmia Observatory)|
After the real coffee break, not made in the coffee automaton, Neil Turok, Perimeter Institute, spoke on the Hartle-Hawking "no boundary" proposal. This 1983 paper, "The Wavefunction of the Universe", on the big bang birth of the universe has been the source of much work and study ever since. Turok said that even though some of the initial description seems to not quite be right, the initial idea has triggered much ongoing research. The idea of "the wavefunction of the universe" has been very productive. I downloaded the paper and hope to make some progress in understanding it, but just trying to work through the first page convinced me that I need to do more preparatory work.
|Neil Turok, Perimeter Institute, on continuing analysis of the 1983 no boundary proposal (Source: Palmia Observatory)|
It was a lot of fun hearing more of the details of Hartle's influence on the development of physics. He was often described as a very humble person who was always eager to help students and associates. He would often stop in offices and ask how things were going? He actually wanted a serious discussion and would listen very carefully, even if he disagreed with the idea. He was very productive in his career and helped so many others at the same time. Other illuminaries in the audience that I recognized included Bob Wald, author of the 1984 classic "General Relativity" (a book to difficult for me) and David Gross, who shared a Nobel prize for developing the concept of asymmetric freedom in particle physics. Also Mark Srednicki, UCSB, author of Quantum Field Theory, also made a presentation on Bayesian quantum cosmology.
|Hartlefest dinner break on the KITP patio (Source: Palmia Observatory)|
After dinner several other physicists and former students offered testimonials and appreciation for Jim Hartle. Finally, Hartle himself made a few remarks, mostly in a humble way about how he was lucky and appreciative of being able to do the work with the help of his colleagues and being able to provide the support and encouragement of his many students.
|Finally, Jim Hartle offers some humble thanks and comments on being lucky in physics (Source: Palmia Observatory)|
Well, Hartlefest comes to an end and it is time to return to OC. At dinner there, we shared a table with Professor Steven Carlip, UC Davis, and in our conversation, I asked him what textbook they used there for General Relativity. He said that he had been using Sean Carroll's book and recently, just started using his own textbook "General Relativity: A Concise Introduction." The book just came out in 2019 and it sounded so good that I clicked on my friends at Amazon and had the book shipped. Now, how is it possible that I can click on the book on Friday and by the time I drive from SB to OC, the next day the book is on my doorstep! Pretty neat! A quick review of topics covered showed me that in many instances, the author had identified the topics that stump students or that cause confusion if not properly understood and I could see right away that the book was going to be very helpful for me. Thanks for the quick delivery, my friends at Amazon and thanks for the recommendation, Professor Carlip!
|General Relativity by Steven Carlip, UC Davis, is indeed a concise introduction (Source: Palmia Observatory)|