Friday, December 2, 2016

A Quantum Limit on How Fast You Can Talk

Is there a fundamental upper limit on how fast we can communicate? If you're like me, that limit is set by your despised cable provider (in my case, Comcast, which avoids being the most disliked company in America only by virtue of being ranked ahead of Time-Warner in most of those surveys).

But recently, Raphael Bousso at the University of California has proposed that quantum mechanics sets an absolute upper limit on how fast information can be transmitted. The limit he proposes in his paper is not all that interesting, but the reason for the limit is rather astonishing.

Monday, November 21, 2016

How will the Universe End? The Big Rip and the Little Rip

Some say the world will end in fire,
Some say in ice.
I say it will end in an infinite-density singularity driven by a scalar field with a negative kinetic term.

Who knew that Robert Frost had such a deep grasp of cosmology?

A couple of weeks ago, New Scientist asked me to comment on a recent paper about the Big Rip. What's that all about?

As the universe expands, all of the ordinary matter becomes less dense. That makes intuitive sense -- if you have a fixed amount of matter in an expanding box, then the amount of mass per unit volume has to go down. But in 1999, Rob Caldwell at Dartmouth made a radical suggestion: suppose that as the universe expanded, the density of the dominant form of energy increased instead of decreasing. This leads to very weird behavior -- the Universe enters a superaccelerated phase, with the expansion factor going to infinity at a finite time, at which point the equations break down at a singularity. It was later pointed out by Caldwell, Marc Kamionkowski, and Nevin Weinberg that as the universe approaches this singularity, it expands so rapidly that all of bound structures in the universe would be torn apart. First galaxies would dissolve, then the solar system would disintegrate, followed by the destruction of the earth, our bodies, and then the atoms in our bodies and the nuclei inside the atoms. And we would be dead by then. Caldwell, Kamionkowski, and Weinberg coined the term "Big Rip" to describe this fate for the universe.

So what was my contribution to this? Nothing, actually. I later worked with Paul Frampton and Kevin Ludwick to come up with the "Little Rip." In what sense is the Little Rip "littler" than the Big Rip?

Friday, November 18, 2016

A Dubious Honor

Today I received my subscriber's copy of the Dec. 2016 issue of Analog, which includes my short story, "Fermi Meets Sagan."  I also received a card in the mail letting me know that as of the next issue, Analog is moving to a bimonthly publication schedule, putting out six issues a year. So I have the dubious distinction of having a story appear in the final monthly issue of Analog. Ever.

Monday, November 14, 2016

Reality Intrudes

Blogging will be light to nonexistent until the beginning of December, as I am working on a grant proposal to the NSF. Given the increasing fraction of time that my colleagues (especially in biomedical research) seem to devote to proposal writing, along with a decreasing success rate, I am beginning to wonder if the research funding system is starting to impede scientific research instead of promoting it. But that's a discussion for another time.

Thursday, November 10, 2016

So You Want to be a Scientist

I often meet with high school students interested in pursuing a career in physics or a related field. A lot of the advice I give them regarding their high-school course work is obvious. Take the most advanced math classes that your school offers. Take the most advanced physics classes. But one bit of advice regarding high school courses is both surprising and often unwelcome to these students.

Monday, November 7, 2016

How to Experience a Parallel Universe

I'll admit it -- I'm a sucker for parallel universe stories. The book that really got me hooked on science fiction around 3rd grade was Alan E. Nourse's The Universe Between. I don't think Nourse was a household name in the world of science fiction even back then. He was a medical doctor mostly known for his column in Good Housekeeping. But he wrote a lot of other science fiction that I enjoyed as a kid, including Star Surgeon, which has an astonishing revelation about halfway through the book. Sadly, I suspect his books are all out of print by now.

Among the more recent parallel universe novels, I highly recommend Paul Melko's The Walls of the Universe, based on his Hugo-nominated novella of the same name. And when it comes to parallel universes, the Star Trek episode in which Spock has a beard is sheer genius. That episode was written by Jerome Bixby, who also penned one of the most disturbing science fiction stories ever written. (As I noted in my previous post, Bixby was something of a two-hit wonder, although that's better than being a no-hit wonder).

What I like the best are stories in which the differences between the parallel universes are subtle, not striking. The latter are rather cliched by now. Kennedy assassination averted? Check. Hitler wins World War II? Yawn. And now I'm going to tell you how to experience these subtle differences yourself.

Thursday, November 3, 2016

My Election Prediction

I am going to make my prediction for the upcoming election:  a tie in the Electoral College, throwing the election into the House of Representatives.  How do I know this?  It's based on a very simple fact.

The Three-Body Problem, Final Verdict

In an earlier post I gave my initial reactions to Liu Cixin's novel, The Three-Body Problem, which I had just begun reading. I've finished it now and can give my final opinion. I would give the novel a B+. (Damn professors, always handing out grades...)

Monday, October 31, 2016

Bilbo Dies

William Bowen, who served as president of Princeton when I went there, has died. A very important fact went missing from the published obituaries: all of the students (and who knows how many professors) habitually referred to him as "Bilbo." The card catalog for the main library (yes, there were card catalogs back then) even had the following entry:  Bilbo, see Bowen, William G. I don't know if this entry vanished when the university library catalog went electronic -- it would be a pity if it did.

Wednesday, October 26, 2016

The Day They Nuked Mississippi

Once upon a time, the U.S. government detonated two nuclear bombs in Mississippi.

Was this the sequel to the burning of Atlanta? Did Ulysses S. Grant possess a secret nuclear arsenal? No, these were underground explosions near Hattiesburg back in the 1960s, designed to see how easy it would be to detect nuclear tests using seismic data.

The U.S. engaged in all sorts of wacky nuclear high jinks back in the day. There was Project Plowshare, which explored the possibility of using nuclear bombs for the purposes of earth moving. Just imagine if we had built the Interstate Highway System that way -- you wouldn't need street lights because the highways would glow in the dark.

Monday, October 24, 2016

Chinese Science Fiction - The Three-Body Problem

Traduttore traditore. That was a favorite saying of one of my college Russian professors. It means "the translator is a traitor." Or at least I think that's what it means. I don't speak Italian.

I almost never read science fiction in translation from another language. And the main reason is that most science fiction is written in English. If you can read English, as many readers of this blog can, then you automatically have access to 90+% of the world's published science fiction. There are a few exceptions -- there has long been a thriving parallel world of Russian science fiction -- but most science fiction remains stubbornly Anglophone.

Monday, October 17, 2016

Pokemon? Or Prescription Drug?

My nephew, a fourth-year medical student, is visiting for a month to do an externship at Vanderbilt. He told me about a game that the medical students play: one person announces a name, and the other person has to guess whether it's the name of a Pokemon or a prescription drug.

Here's a sample for you to try.  See if you can figure out which of these are Pokemon, and which are the names of drugs:

A. Remelteon
B. Remoraid
C. Empoleon
D. Zingo

Answer after the break...

Monday, October 10, 2016

In Memoriam: Debbie Jin

I was saddened to learn of the death of Debbie Jin several weeks ago -- she was only 47 years old. Debbie worked at NIST (what used to be called the Bureau of Standards) in Boulder, Colorado. I first met her in my previous incarnation as an Ohio State professor, when we tried to hire her into a faculty position there. Over the years, I've tried to keep track of all of the young superstars who turned down our job offers -- Debbie became by far the most outstanding of all of the "ones who got away."

Debbie worked on ultra-cold systems of atoms. These are the famous "Bose-Einstein condensates" -- bosons are particles that like to clump together, and when you make them cold enough, they all pile into the same quantum state. Fermions, on the other hand, hate each other and don't like to be together. Debbie was the first to produce a "fermionic condensate" in the laboratory. Had she lived, I think she would have been a strong contender for the Nobel Prize. I invited Debbie to give our 2011-12 Slack Lecture here at Vanderbilt, and she gave a spectacular talk. She was also one of the nicest people I've met in the world of physics.

Tuesday, October 4, 2016

The Man Who Knew Infinity: Why are Senior Mathematicians so Calm?

Time for some amateur psychoanalysis. I recently saw The Man Who Knew Infinity, which tells the amazing story of the Indian mathematician Ramanujan and his relationship with the English mathematician Hardy. It's an excellent film, but I won't spoil it for you -- let's just say that if it were fiction instead of a true story, nobody would believe it. The movie does an amazing job of portraying the actual process of doing mathematics. (I wrote earlier about the difficulties of writing math-based science fiction in this post.)

I should admit at this point that I thought seriously about going into mathematics in college.  But I was a good enough mathematician to realize that I was not a good enough mathematician to do mathematics professionally. So I went into theoretical physics instead. I've never regretted my decision, but I do envy the more senior members of the mathematics community for their relative calm, as compared to those of us in theoretical physics. What do I mean by that? You'd think that senior tenured physicists would eventually kick back and relax, instead of continuing to seek awards and other kinds of validation for their work. But it ain't so (and I am as guilty as anyone else). On the other hand, I've found senior mathematicians to be relatively more relaxed about such things. And I have a theory as to why this is the case.

Monday, October 3, 2016

Marvel Superhero Day at School

My daughter's school is sponsoring "Marvel Monday," when everyone is supposed to dress up as a Marvel superhero. What to do? I suggested that she go as the Fantastic Four's Sue Richards, who can turn invisible. Then just skip school that day.