One of the most popular complications in horology is the tachymeter, a graduated ring around the edge of a watch that usually reads from something like 500 to 60. Apple has recently added a tachymeter function in its new Chronograph Pro face and, given that these Apple Watch faces are things we love to hate, we decided to check it out.
Apple’s tach is basically a chronometer with a visual “units per hour” readout. The way to read a tach is to start the chronograph and then perform one action – drive, fly, or sail a mile, for example. If you’re moving, for example, to see your speed you’ll press the button, start the chronograph, and stop it when you pass the mile marker. If you’re going an improbable 1,000 miles per hour, you should see 1,000 units/hr on the face. Going at a saner speed, say 75mph, will bring the seconds hand around to 75 as you pass the miles mark.
This was helpful when planes and cars didn’t have speed indicators. It’s not so helpful now. Because of that, the tachymeter used to be far more valuable when doing quick calculations in the air or on land.
One of the most famous tachymeters appears on the Omega Speedmaster, the watch worn by Buzz Aldrin on the Apollo 11 mission and, more importantly, on the face on the moon. He wrote:
“It was optional to wear while we were walking on the surface of the Moon … few things are less necessary when walking around on the Moon than knowing what time it is in Houston, Texas. Nonetheless, being a watch guy, I decided to strap the Speedmaster onto my right wrist around the outside of my bulky spacesuit.”
An apocryphal story talks about NASA’s acquisition of the watches for the mission. When the NASA employee who bought the watches approached the jewelry store in Houston that had enough for the mission members to wear, the salesperson pointed out the tachymeter, noting it could measure speeds of up to 500 miles per hour, speeds he was sure that the buyer would never reach. Little did he know…
Is the tach useful? The answer is “probably not.” Given the Apple Watch has GPS built-in, knowing the speed you’re moving is trivial. However, it’s nice to be able to measure the speed of your Model T roadster as you buzz down a country road using a technology that has been around for centuries. Like many of Apple’s WatchOS decisions, the tach is an accurate but vestigial addition from historical timepieces but it’s nice to know that someone in Cupertino still has a thing for the old tachymeter.