There I was, lying in bed in the middle of the night.  What time it was, I could not be sure.  But that didn’t stop me from trying to figure it out.

The most recent issue of Outside magazine has an interesting article about navigating using only the clues in one’s surroundings.  No maps, no compasses — certainly no GPS receivers.  Things like the sun, damp hills, and wave interference patterns served in their stead.

I’m pretty decent at dead reckoning for location, and I can almost always return to a spot if I’ve been there once.  That said, I always bring serious navigation equipment when I’m solo hiking in the wilderness: topo maps, a high-end hiking GPS, and a phone that will work in the area.  I like the romance of instinctive way-finding, but I like not getting lost, too.  And I really love maps.  Clocks, too.

I have no traditional clocks in my bedroom (my iPod Touch is my alarm), and I don’t wear my watch when I sleep, so I have no way of checking the time in the middle of the night without getting out of bed and stumbling to my desk.  Unfortunately, I sometimes wake up with an incredible urge to know how much longer I’ll be able to sleep.  With that knowledge acquired, I can fall back into bed and quickly doze off for a few more hours.  However, if I don’t get up and go look at my iPod or phone, I just lie in bed, unable to sleep, wondering what time it is.  Then a blog post results.

Anyhow, the Outside article got me thinking: would it be possible to use the clues from my nighttime environment to divine the time?

There isn’t much to go on.  The neighbors are pretty quiet.  It’s dark outside.  I can’t hear automobile traffic from my room, and the distant trains that I can hear don’t seem to obey any particular patterns of activity.  I can usually feel when my alarm is about to go off, but if that’s more than a few minutes away the usefulness plummets.

What I can hear are two cyclic appliances: the surprisingly noisy refrigerator compressor turning on and off, and the soothing expansion and contraction of the radiator as the system heats and coasts.  Thus, I can judge the relative passage of time, but absolute time remains elusive.

Surely there must be a way to figure out the time to within, say +/- 30 minutes without a clock on an overcast night.  But how?

April 23, 2018 – BOSTON – The Transportation Security Administration (TSA) today introduced the first deployment of through-body X-ray scanners at each of Logan International Airport’s security checkpoints.  The machines, which scan through the clothes and bodies of passengers, supplant the earlier backscatter imagers, which cannot penetrate the skin.

“There have been concerns for some time about the ability of terrorists to bring weapons and explosives through checkpoints by concealing them in body cavities,” said TSA spokesman Tom Parsons. “These scanners will allow us to significantly increase the safety of air travel.”

The machines operate much like medical diagnostic X-ray scanners.  Each passenger passes through an arched gateway, which has an X-ray source on one side and a detector on the other.  The X-rays pass through the passenger’s clothes and body, and any concealed items appear on a screen being watched by a TSA agent.  Much like the X-ray machines used to scan luggage, suspicious items are highlighted in color.

Though the technology has been available for many years, the recent push to deploy the scanners at airport security checkpoints was driven by a rash of suicide bombings in which the bombers concealed the explosives inside themselves.  In a failed attempt on a transcontinental flight last October, a terrorist was found to have an astonishing 5 kg of high explosives packed in her GI tract.

The through-body machines are not without controversy.  Harvard researcher Dr. Nestor Lokenbal notes that the X-rays emitted by the machines are ionizing radiation capable of causing DNA damage and cancer. “A single scan from one of these machines is equivalent to nearly three years of natural background radiation,” says Lokenbal, “which corresponds to an absolute lifetime cancer risk increase of about 0.1% per scan.”  He continued, “That might not sound like much, but the effect is additive, so for frequent fliers and pilots, the added hazard can be quite significant.”

The TSA’s Parsons dismisses the risk, noting that the machines have been tested by the TSA to be safe, even though precise information about their operation remains classified.  “We are confident that the flying public will accept through-body scans as necessary for flight safety, much as they did backscatter scanners in 2010 and the ban on laptop computers in 2015.”  As an alternative, passengers can opt out of the through-body X-ray and instead be subjected to a manual full body cavity search.

The American Civil Liberties Union announced it is suing to stop the use of the machines, citing fourth amendment concerns, among others.