Saturday, December 31, 2022

Favorite science fiction invention?

 In the forward-looking spirit of the New Year, it might be fun to get readers’ opinions of their favorite science fiction inventions.  I wrote about favorite sci-fi materials back in 2015, but let’s broaden the field. Personally, I’m a fan of the farcaster (spoiler warning!) from the Hyperion Cantos of Dan Simmons.  I also have a long-time affection for Larry Niven’s Known Space universe, especially the General Products Hull (a single molecule transparent to the visible, but opaque at all other wavelengths, and with binding somehow strengthened by an external fusion power source) and the Slaver Disintegrator, which somehow turns off the negative charge of the electron, and thus makes matter tear itself apart from the unscreened Coulomb repulsion of the protons in atomic nuclei.  Please comment below with your favorites.

On another new year’s note, someone needs to do a detailed study of the solubility limit of crème de cassis in champagne.  Too high a cassis to champagne ratio in your kir royals, and you end up with extra cassis stratified at the bottom of your flute, as shown here.

Happy new year to all, and best wishes for a great 2023.

Tuesday, December 27, 2022

The difficult need for creativity on demand

Thoughts at the end of another busy year…. Good science is a creative enterprise.  Some stereotypes paint most scientists as toiling away, so deeply constrained by logic that they function more like automatons grinding out the next incremental advance in a steady if slow march of progress. In practice, originality and creativity are necessary to develop and grow a research program.  Some of this is laid out (paradoxically, in a methodical list) by Carl Wieman in this article here.   Picking the right open questions to address (hopefully ones that are deep and interesting to other people as well as you), and figuring out how to address them given the tools at your disposal, frequently requires intuition, leaps beyond incrementalism, and some measure of intellectual risk-taking.

One aspect of modern science as practiced today with which I find myself struggling is the issue of time. We live in a short-term world.  Grants are generally brief in duration compared to doctoral student timescales and the time it takes to tackle big questions.  There are many more demands on our time than in the past, and it seems like most funding sources profess to want fresh, new, ground breaking ideas that are both high-risk/transformative/disruptive and yet somehow very likely to produce rapid, high-profile glossy results.  Some also want to see brand new approaches to education and outreach each time.  Finding the time to think deeply about the science and the educational aspects, reinventing research programs like clockwork, is something that I find very challenging.  One answer is, since creativity doesn’t generally respond to on-demand calls, always be thinking and noodling on ideas, but that’s much easier to say than to do consistently.   I’d be curious to hear others’ strategies for dealing with this; while I’m pretty set in how I work at this point, a discussion could be fun and useful.

Saturday, December 17, 2022

Brief items - LOC, GPT, etc.

 This year was a busy one and my overall posting rate is down.  Hopefully the coming year will be a bit less frenetic, but who knows.  A few brief items:

  • First, in the odd self-promotion department, this blog is officially going to be indexed by the Library of Congress as part of their Science Blogs Web Archive.  This is another sign that I am officially ancient in blogging terms.  This blog has never had the huge readership of some, but thanks to you for raising it above whatever the threshold of notice is for this.
  • This was a cute story.  Folks at ETH have shown that a thin, barely percolating layer of gold can act as an anti fogging coating on glasses, since it can locally heat up due to its infrared absorption, while still being sufficiently transparent for use in eyewear.  At the risk of costing myself a lucrative potential patent, it seems to me that you could do the same thing using TiN, which has similar near-IR optical properties, and should be easy to integrate with the TiO2 coating that the researchers already use.  
  • In a headline that is not a repeat from September, there is a new contender for world’s largest dilution refrigerator under construction, this time from FermiLab.  Multiple quantum computing platforms benefit from the sub-100 mK temperatures, so it’s not surprising to see efforts along these lines, but 5 cubic meters of sample chamber seems a bit much.  Time to invest in my Canadian 3He futures.
  • I’m glad to see that someone has been thinking like my sci-fi-loving brain, and working out whether gravitational wave detectors could be used to detect evidence of some types of interstellar spacecraft.  While the paper concerns conjectural accelerating planetary-mass ships, certainly exotic propulsion ideas (warp drives, wormholes) would also have gravitational radiation signatures.
  • Speaking of science fiction, like a lot of people I spent some time this week playing with chatGPT, the language model that may be the end of high school English essays, college admissions essays, and quite probably a lot of jobs.  Its output is uncanny and worrying, especially since it has no problem just brazenly lying and making up sources.  (For fun, see what happens if you ask it to explain why 51 is a prime number.). Still, it’s hard not to feel like we are right at some threshold, where expository and creative writing, historically the province of at least somewhat educated humans, is no longer ours.  This could mean great things for education (I asked it to explain Stokes’ theorem to me, and it did a pretty nice job), but it could mean terrible things for education (why learn to write well when a free tool can do a decent job for you?).  The calculator and computer did not eradicate math education or math literacy, so hopefully we will reap more of the positives than the negatives.  This post was written 100% by me, btw, with no GPT assistance, though remember that chatGPT lies….
  • At the risk of being deemed a dangerous website by Twitter, where I am here, I’m on a mastodon instance now as well. was started by Charles Seife and hosts a bunch of scientists and science journalists.

Tuesday, December 13, 2022

The fusion story of the day

There is a press conference going on right now announcing a breakthrough at the National Ignition Facility at Livermore.   The NIF is an inertial confinement fusion facility that uses 192 laser beams to compress a fuel pellet containing deuterium and tritium.  The pellet is inside a gold hohlraum, and it's really the x-rays from the gold that do a lot of the heavy lifting in this experiment.  The claim is that the energy output from the D-T fusion (which comes in the form of energetic helium nuclei, 14 MeV neutrons, and x-rays) has now exceeded the energy input from the lasers.  That's clearly necessary if there is ever to be any hope of using this approach to generate actual electricity, but it is far from sufficient. 

There is some very interesting materials science at work throughout the project that bears on this.  Right now, the lasers used in the NIF are based on doped glass amplifiers, and those get very hot under use, so that there needs to be hours between shots.  Also, they basically rebuild the sample mounting for the hohlraum after each shot.  This is fine for proof-of-concept physics experiments, but it's very far from a workable power plant.  

This is an exciting time for fusion research, in that there is a fair bit of activity, including startups.  (Note also that some of these approaches are aiming for scales closer to US Navy sized, like 20 MWe, rather than city power which is more like 2 GWe.)   To give a sense of my age and the timescale for these projects, when I was an undergrad, I spent a summer doing heat transfer calculations for the cable-in-conduit conductors for the D magnets for ITER.  That was in 1992.  The cliché is that fusion is always 20 yrs away, but we should know considerably sooner than that whether the startup approaches are likely to get there.  

Saturday, December 03, 2022

The wormhole kerfuffle, ER=EPR, and all that

I was busy trying to finish off a grant proposal and paper revisions this week and didn't have the time to react in realtime to the PR onslaught surrounding the recent Nature paper by a team from Harvard, MIT, Fermilab, and Google.  There are many places to get caught up on this, but the short version:

  • Using their Sycamore processor, the experimentalists implemented a small-scale version of the SYK model.  This is a model that has many interesting properties, including the fact that it is a testbed for holography, in which a bulk system may be understood by the degrees of freedom on its boundary.  For an infinitely large SYK system, there is a duality to a 2D gravitational system.  So, a protocol for moving entanglement in the qubits that make up the SYK system is equivalent to having a traversable wormhole in that 2D gravitational system.  
  • The actual experiment is very cool.
  • The coverage in the press was extensive (Quanta, NY Times, e.g.).  There was a lot of controversy (see Peter Woit's blog for a summary, and Scott Aaronson for a good take) surrounding this, because there was some initial language usage that implied to a lay-person that the team had actually created a traversable wormhole.  Quanta revised their headline and qualified their language, to their credit.  
Rather than dogpiling on the media coverage, there are two main points at issue here that I think are worthy of discussion:
  1.  What do we mean when we say that we have experimentally implemented a model of a system?     When atomic physicists use ultracold fermionic atoms to make a 2D lattice governed by the Mott-Hubbard model (like here and here), we say that they have made a Mott insulator.  That same model is thought to be a good description of copper oxide superconductors.  However, no one would say that it actually is a copper oxide superconductor.  When is a model of a thing actually the thing itself?   This is at the heart of the whole topic of quantum simulation, but the issue comes up in classical systems as well.  My two cents:  If system A and system B are modeled extremely well by the same mathematics, that can give us real insights, but it doesn't mean that system A is system B.  Better language might be to say that system A is an analog to system B.  Physicists can be sloppy with language, and certainly it is much more attention-getting to editors of all stripes (be they journal editors or journalism editors) to have a short, punchy, bold description.  Still, it's better to be careful.  
  2. What do theorists like Lenny Susskind truly mean when they claim that entanglement is genuinely equivalent to wormholes?  This is summarized by the schematic equation ER = EPR, where ER = Einstein-Rosen wormhole and EPR = Einstein-Podolsky-Rosen entanglement.  I think I get the core intellectual idea that, in quantum gravity, spacetime itself may be emergent from underlying degrees of freedom that may be modeled as sorts of qubits; and that one can come up with fascinating thought experiments about what happens when dropping one member of an entangled pair of particles into the event horizon of a black hole.  That being said, as an experimentalist, the idea that any kind of quantum entanglement involves actual Planck-scale wormholes just seems bonkers.  That would imply that sending a photon through a nonlinear crystal and producing two lower energy entangled photons is actually creating a Planck-scale change in the topology of spacetime.  Perhaps someone in the comments can explain this to me.  Again, maybe this is me not understanding people who are being imprecise with their word choice.