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Dropping Schrödinger's Cat Into a Black Hole
Combining gravity with the process that transforms the fuzzy uncertainty of the quantum realm into the definite classical world we see around us could lead to a theory of quantum gravity.
In the news round-up, Brendan Foster and I chat about the MICROSCOPE satellite experiment, which was launched in April to put the equivalence principle--and general relativity--to the test.
General relativity's prediction of gravitational waves was famously vindicated last February, when the LIGO team announced the discovery of gravitational waves. But could these ripples in space-time be used to look for violations of general relativity and give us clues about quantum gravity? Brendan has put together a special report, including interviews with LIGO team member Alessandra Buonanno and FQXi's own Ted Jacobson, and expert on quantum gravity, to find out.
Sticking with quantum gravity, FQXi's Sabine Hossenfelder talks about her search for signs of defects in the fabric of spacetime--which could reveal if spacetime has a discrete structure--to reporter Colin Stuart. You can also read Colin's profile of Sabine, "Wrinkles in Spacetime," too.
And we have a bit of a treat to round off the podcast. The Centre for Quantum Technologies in Singapore recently ran a short story competition, with a quantum theme. Joining us is their first prize winner, author Liam Hogan, who chats about his physics background and how he comes up with the ideas for his stories. Then you get to listen to Hogan reading out his award-winning story, "Ana," in full -- recorded by Wandsworth radio's Blackshaw Arts Hour, and reproduced here with their permission.
Ooh, and if you like short stories, you might enjoy a couple of the entries to last year's Trick of Truth essay contest, asking you to explain the mysterious connection between physics and mathematics. A compilation volume of the winning essays--which have been updated and expanded--has been published by Springer and is now available to buy in a rather nice hardcover, to keep on your coffee table. You can also download individual chapters from Springer's site.
We all just enjoyed the detection of gravitational waves due to two colliding black holes. David Ritz Finkelstein, who passed away in January, was the first, in 1958, who identified Schwarzschild's solution of the GR equations as corresponding to a region in space from which nothing escapes. This compelled Penrose and Wheeler to believe that those things actually do exist. He is of course also known for the related Eddington-Finkelstein coordinates.
Personally I first met David Finkelstein, not in a Black hole, but in Prague, in 1994 at a quantum structures conference. David's main concern had always been the fundamental structures of nature, for quantum theory, for GR, and even more so, for the two together. He indeed very early on accepted von Neumann's concern that something is fundamentally wrong with Hilbert space. This was the start of a quest in a world of exotic structures, and his travels have inspired many scientists, and continue to do so. Among many others, this includes quaternionic quantum theory and quantum sets. David was a proper maverick scientist, and this statement is intended in entirely positive terms. Not only his outstanding intellect, but also his integrity and generosity where exceptional.
But he was a lot more than that. The second time I met him was in 1997 in Atlanta Georgia, where he lived and was hosting a meeting again on quantum structures. In the weekend he took some friends and me out to the movies, to watch Seven Years in Tibet. A bit cheeky that was, since he was to meet the Dalai Lama two days after. Indeed, David was for a while the Dalai Lama's physics teacher.
The last time I met David Finkelstein, in 2014 in Cambridge, was at a meeting dedicated to Eddington. During the conference dinner I had geared up for producing a wall of electronic noise and guitar distortion, with Ian Durham featuring on harmonica. Not surprisingly, we successfully emptied the senior common room where the conference dinner had taken place, with one notable exception. David Finkelstein, then 84 years young, was still there and clearly enjoying it. He later explained that he always has had an interest, not surprisingly, in experimental music and other weird stuff. More generally, David had a great interest in art, history, and many other things, and their interwovenness with science. Why not have a look at David Finkelstein's analysis of Albrecht Durer's engraving MELENCOLIA I, that can be found on the arXiv.
A truly original thinker, and equally so, a truly original human has passed away.
Updated 4:15pm Feb 11: Congratulations to the LIGO collaboration for successfully detecting gravitational waves from the merger of two black holes. Follow @FQXi on Twitter for live updates.
I’m opening this thread as a place to watch and discuss Thursday’s big announcement from the LIGO collaboration about the hunt for gravitational waves from the merger of black holes. The press conference takes place at 3:30pm GMT, 4:30pm CET, 10:30am ET, 7:30am PT. You can watch the live stream here:
Sabine Hossenfelder has some nice background on gravitational waves over at Backreaction. At New Scientist, there’s a nice diagram using NASA’S WMAP image of the cosmic microwave background to attempt to located where a possible gravitational wave signal may have been found, accompanying an article by Joshua Sokol.
There are a host of other good articles out there—so feel free to link to any good ones that you find in the comments below.
Rest In Peace astronaut Edgar Mitchell, the sixth man to walk on the moon and the last member of the Apollo 14 mission. He was oddly credulous for a man of science, confusing the public with his proclamations that alien visitors interceded in the arms race, the Roswell incident was not a lot of tin foil and sticks but a downed saucer, and the like, on which I commented in a previous blog.
But we remember him this weekend for the uncommon bravery involved in his work as an aviator, test pilot, and NASA astronaut. Without sound data and dedicated skepticism (not cynicism), we are likely to believe any old thing. But without a passion for trying on new and even radical ideas, what we know will be surely chained by expectation.
Flaws notwithstanding, here was an explorer's mind.
On Dec. 8, 2015, two different groups (sharing an author) posted papers to the arXiv announcing the possible detection of planet-sized objects in the far outer solar system (Vlemmings et al, arXiv:1512.02650v2 and Liseau et al, arXiv:1512.02652v2). There was a brief flutter on Twitter and in the media, which shortly died down. As far as I am aware, no large-scale effort has begun to confirm or refute these potential detections, and both papers have since been withdrawn, until further data is available.
Six weeks later on January 20, a paper appeared in The Astronomical Journal adducing strong circumstantial evidence, based on solar system object orbits, for a large 9th planet in the outer solar system (K. Batygin and M. E. Brown, The Astronomical Journal Volume 151, Number 2). The media attention was staggering, and the paper downloaded 243,547 times of this writing. There are almost certainly numerous intense efforts underway to try to detect the object.
While it may be surprising to see much more attention (and resources) directed toward circumstantial evidence for a 9th planet than to direct potential observation of one, this is the sort of decision with which researchers — and research funders, and journalists — are confronted all the time.
These decisions are, in essence, predictions about how things are going to unfold; this has gotten me interested in how to better solicit and aggregate expert predictions in science and technology, and helped motivate a new project I and several other physicists have been developing, called Metaculus.
To be more specific, there is an important class of decisions that can be posed in the form of "what is the expected return on my investment of time/effort/attention/funding in X?" For some science-based examples:
— "What is my expected return in using my time on telescope X to search for the planet suggested by this data?" Here the potential "return" is fame and satisfaction at discovering a planet.
— "What is my expected return in skimming/reading/studying this new paper?" Here the return might be insight gained, entry into a promising new research direction, etc.
— "What is the expected return in funding this research grant?" Here, the return could be papers published, talks given, meetings run, or more abstractly intellectual impact on a field or set of questions.
— "What is the expected return on building this instrument?" The impact here would be scientific discovery, possibly measured by papers, citations, etc.
A central idea in these questions is that of expected return. Most simply, this could be the likelihood of success times the return if successful. Or, if there are multiple possible outcomes, it could be the sum/integral of the probability of each outcome times that outcome's impact.
The idea of high expected return (per dollar) is part of FQXi's core philosophy (and grantmaking criteria). To make a financial analogy, government funding agencies tend to purchase the equivalent of a diverse-but-safe portfolio of bonds and index funds: decent returns, fairly safe. These agencies tend not to fund the science equivalents of startup companies — projects where the chance of major success is fairly low, but the impact if successful is very high. We believe that in the science, as in the corporate, world, both types of investment are very important, and one role of FQXi is trying to fill in this end of the research funding portfolio.
Evaluating the "probability of success" is, though, rather difficult. It's often not hard to assess which of two projects is more likely to be successful. For example, I would say the Wendelstein 7-X fusion experiment and subsequent efforts are more likely to lead to useful energy generation than Brillouin Energy's LENR experiments. But how much more likely? Ten times? A thousand? A million? The 7-X’s funding is probably about 1000 times higher, so which experiment has the higher per-dollar expected return on investment depends on this likelihood ratio! Or what about tabletop quantum gravity experiments versus a bigger version of the "holometer"?
The idea of Metaculus is to generate quantitative and well-calibrated predictions of success probabilities, by soliciting and aggregating expert opinion, and by (in the process) helping people improve their skills at quantifying and predicting impact. Metaculus poses a series of questions, for example "Has a new boson been discovered at the LHC?", with relatively precise criteria for resolving the question after a specific time. Users are invited to predict likelihoods (1-99%) for these questions, and later awarded points for accuracy in their predictions. Studies show that by carefully combining the predictions of many users, better precision and calibration can be achieved.
My experience so far suggests to me that there are several ways a prediction platform like this, when applied to scientific research, can be complementary to traditional peer-review. The effort of creating precise criteria for 'success', and in trying to assign numbers to success likelihood, has a quite different feel than just reading to understand whether a paper/proposal is intellectually sound or correct. It also makes me realize that in all of the peer review and assessment that I have done, I've never been asked (or asked someone) to supply a number like "what is the probability that X will be the result of funding/publishing Y?" Since that's a significant part of what peer review is, isn't that a bit odd?
Perhaps there is an opportunity for real improvement here. A recent study made the case that prediction 'markets' are quite effective — and more effective than surveys even of experts — in forecasting whether given research (in this case in psychology) would be successfully reproduced (PNAS, Vol 112, no. 50).
I'm very interested in everyone's ideas for how something like Metaculus could be used in trying to make the biggest impact we can out of the limited resource society throws in the direction of us scientists — please comment!
Measuring Consciousness in the Lab By MAX TEGMARK
[picture]If you're driving, you're having a subjective experience of colors, sounds and vibrations. But does a self-driving car have a subjective experience? Does it feel like anything at all to be a self-driving car, or is it a zombie in the sense...
2015 in Review: New Podcast on Planets, Particles... By ZEEYA MERALI
We’re taking our annual look back at the physics highlights of the past 12 months — as chosen by FQXi member Ian Durham, a quantum physicist at Saint Anselm College in New Hampshire. Ian will be counting down his top 5 picks in a special podcast...
Detecting Parallel Universes Hidden Inside Back... By ZEEYA MERALI
[picture]It’s hard to say what’s the most exciting element of this new paper on parallel universes, the inflationary multiverse, and black holes, by Tufts cosmologist (and FQXi member) Alex Vilenkin and colleagues. Is it the idea that black holes...
New Podcast: Shifty Neutrinos Win Big, a Cosmic... By ZEEYA MERALI
[picture]Congratulations to the 1300-strong group of physicists who won the Breakthrough Prize in physics on Sunday, for the discovery of neutrino oscillations—confirming that neutrinos can switch identities and have mass. This is the same...
“Spookiness” Confirmed by the First... By ZEEYA MERALI
[picture]Spookiness, it seems, is here to stay. Quantum theory has been put to its most stringent “loophole free” test yet, and it has come out victorious, ruling out more common sense views of reality (well, mostly). Many thanks to Matt Leifer...
Jacob Bekenstein (1947-2015) By ZEEYA MERALI In remembrance of Jacob Bekenstein, a guest post by his friend and colleague Eduardo Guendelman, Physics Department, Ben Gurion University, Beer Sheva, Israel.
It is with great sorrow that we report on the passing of Professor Jacob D....
The Physics of What Happens Grantees By BRENDAN FOSTER
This past winter, FQXi announced it's fifth Large Grant program, on the topic of The Physics of What Happens – a call for proposals for research and outreach projects on "Events". I am happy to announce that from an initial group of almost 250...