Solar Time

This post is about a classic Jose-ism: Solar Time and the argument for waking up with the sun.

This weekend, New York goes from Eastern Standard Time to Eastern Daylight Time. I really don't like this idea. Not only do I lose a precious hour of sleep for what seems like no good reason, but extending daylight one hour into the evening comes at a direct cost: robbing one hour of perfectly good riding time from the morning!

Due to Prospect Park's car schedule, I am basically forced to ride from 6am to 7am, unless I want to share a not-wide-enough path with slow runner, rollerblader, and bicycle commuter traffic. I tend to hold 22-25 MPH on my park rides, so dodging things takes serious effort. Let's consider how daylight savings time is not helpful here by looking at local sunrise times in New York:

March 6: 6:22
March 7: 6:20
March 8: 6:19
March 9: 7:17
March 10: 7:15

Yes, sunrise gets earlier every day, but the next time sunrise will be at 6:30am or earlier is April 6th. That's a month away. (Remember that the days grow longer from December to June, and shorter again from June to December. This varies roughly as a sinusoid, so the days are getting longer or shorter at their greatest rate - 2 minutes a day! - around the equinoxes.)

Here's where things get complicated. Local sunrise time is a function of latitude, longitude, and day of year. In the northern hemisphere, as you move south or west, the day will grow longer. The simplest example of this is that of the New York to San Francisco flight. Going west, the 6-hour flight only takes "three hours", but going east, it takes "nine hours" due to time zone differences.

On a cross country bicycle trip, sunrise time is further complicated by weird time zone definitions, in addition to the fact that you are traveling east to west (or vice versa). When the sun dictates when you wake up and ride (i.e. early morning), but local time dictates when your hosts will give you breakfast (i.e. 6:30am), this quickly leads to a conflict of interests.

Let's look at local sunrise times on a portion of this summer's Boston to Santa Barbara Bike and Build trip, This is affected by the fact that we're traveling westward (days get shorter), after the Equinox (days get shorter), while still crossing time zones (days shift earlier sometimes).

06/28: Columbus, OH: 6:06am
06/29: Columbus, OH: 6:06am
06/30: Yellow Springs, OH: 6:11am
07/1: Rushville, IN: 6:18am
07/2: Bloomington, IN: 6:24am
07/3: Bloomington, IN: 6:25am EDT
07/4: Lawrenceville, IL: 5:31am CDT
07/5: Salem, IL: 5:37am
07/6: St Louis, MO: 5:43am

Look at this chart. Does it make sense to set a static wake-up time of, say, 6am? Absolutely not! At 6am, we'll be waking up with the sun in Columbus, 30 minutes before sunrise in Bloomington, and 30 minutes after in Lawrenceville. Let's remember that it only takes an hour for that summer sun to make the weather quite unpleasant. That first hour of riding is a huge asset!

I'm an advocate of waking up with a statis offset to sunrise time. For example, I wake up 20 minutes before sunrise every day, when possible. I leave the window shades somewhat open and face east. The sun is my alarm clock, and I feel well rested.

Here's the real kicker: circadian rhythms, the biological clock in humans, is set by the sun, and we don't like change very much! Huge or chronic variations in wake-up time with respect to sunrise time cause us to be thrown off balance, leading (in part) to fatigue and irritability. (Fly to Japan if you don't believe me. Do it now.)

Ponder this if your Saturday night party gets cut short an hour.