Robert Heinlein’s classic short story -All You Zombies- is being adapted into a movie titled Predestination, starring Ethan Hawke.

Reading the smart, tightly plotted, but sadly dated* Heinlein story before going to see the movie will unavoidably damage your enjoyment of the film. And don’t let anyone tell you what it’s about, either.

The only information that can’t ruin it for you is this: It’s about time travel. “Zombies” is a metaphor. There are no undead corpses in the story, and should be none in the film. Unless Peter Jackson is somehow involved, I suppose, in which case there will probably be attractive female zombies with hang gliders and large rubber feet.

* It was written in 1958, and Heinlein’s attitudes towards women were formed considerably earlier.

Time Domain Reflectometry visualized

Wikipedia provides this excellent graphic to help explain how you can determine where the fault is in a very long cable.

Reflection of an electric pulse back towards point of origin

Time delay reflectometry is a clever trick where you can calculate the location of an imperfection in a conductor by timing when the “bounce” returns, as long as you know the speed of signal propagation in the wire (which you generally do).

The impedance of the discontinuity can be determined from the amplitude of the reflected signal. The distance to the reflecting impedance can also be determined from the time that a pulse takes to return. The limitation of this method is the minimum system rise time. The total rise time consists of the combined rise time of the driving pulse and that of the oscilloscope that monitors the reflections.

Plumbers will note that the behaviour of the electric flow here is analogous to water hammer. I think it should be possible to find the distance to an obstruction in a pipe as a TDR calculation, as long as you know how compressible the fluid medium is.

Averting the Year 2038 Disaster

OpenBSD released version 5.5 today, and not only has the OpenBSD team removed the OpenSSL dependency from OpenSSH, they’ve also implemented 64 bit time_t variables on all platforms.

So on Tuesday, January 19th, in the year 2038, when the rest of the world’s Unix systems fail at 3:14:02 Greenwich Standard Time, OpenBSD systems will proceed with business as usual.

I have now fulfilled the promise I made in late 1998 (that I would have an action plan to avert the Y2.038K Disaster by 2018) a good three years early. The plan is: convert to OpenBSD in 2035 if nobody else has caught up.

Total Lunar Eclipse Tonight

“And I will shew wonders in the heavens and in the earth, blood, and fire, and pillars of smoke. The sun shall be turned into darkness, and the moon into blood” — Joel 2:30-1, KJV

NASA has more prosaic information, which should be more useful to most of us.

Here in the Eastern Daylight Time zone, the moon’s going to be completely full at 3:42:18 AM on 2014-04-15. The total eclipse will last from 3:07 to 4:25, peaking at 3:46, so it ought to be quite beautiful if the weather co-operates.

Since I worked all day and was in Boston all weekend, I will most likely be asleep. Enjoy it without me!


The first snow of the season was drifting gently and picturesquely at 8AM, and driving near horizontally by 9. Done by 11 and nothing sticking.

Guess it’s time to plan for the Winter Solstice….

remains of a better woodhenge

It it’s not Scottish, it’s crrrrrrrrap!

“Our excavations revealed a fascinating glimpse into the cultural lives of people some 10,000 years ago – and now this latest discovery further enriches our understanding of their relationship with time and the heavens.”

There’s a paper at the Internet Archaeology online peer-reviewed professional journal (pay site, obviously).

Interesting arxiv physics article to pass the time.

I have long held that time is an emergent phenomena of our meat-based consciousness that has no reality outside our frame of reference. The link’s to an article, based on an extremely difficult to digest paper, about an experiment that attempts to solve the problem of time by testing the theory that time is an emergent phenomenon based on quantum entanglement. If time’s not real outside the observational cone of human experience, then it’s possible to reconcile general relativity with quantum mechanics and the problem of time is no longer a problem for mathematicians.

Honestly, the math’s way over my head. But the popular treatments are interesting, at least.