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...)