That big grandfather clock in the library might be an impressive piece of mechanical ingenuity, and an even better example of fine cabinetry, but we’d expect that the accuracy of a pendulum timepiece would be limited to a sizable fraction of a minute per day. Unless, of course, you work at CERN and built  “the most accurate pendulum clock on the planet.”

While we’re in no position to judge [Daniel Valuch]’s claim, we’re certainly inclined to believe him, mainly because the 1950s-era Czechoslovakian pendulum clock his project was based on, the Elektročas HH3, was built specifically as a master clock for labs, power plants, and broadcast use. The pendulum of this mid-century beauty is made of the alloy invar, selected for its exceptionally low coefficient of thermal expansion. This ensures the pendulum doesn’t change length with temperature, but it still only brings the clock into the 0.1 second/day range.

Clearly that’s not good enough for a clock at CERN, the European Laboratory for Nuclear Research, where [Daniel] works as an RF engineer. With access to a 10-MHz timebase from a cesium fountain atomic clock — no less a clock than the one that’s used to define the SI second, by the way — [Daniel] looked for ways to sync the clock up to it. Now, we know what you’re thinking — he must have used some kind of PLL to give an electromagnetic “kick” to the bob to trim the pendulum’s period. Good guess on the PLL, but the trimming method is a little cruder — [Daniel] uses a stepper motor attached to the clock’s frame to pay out or retract a length of fine chain into a cardboard dish attached to the pendulum’s rod. The change in mass changes the pendulum’s center of gravity, which changes its effective length, and allows the clock to be tuned a couple of seconds per day.

It seems like [Daniel] is claiming that his chain-corrected clock won’t drift more than a second from the cesium clock for 158 million years. Again, we’ll take his word for it, but it’s a wonderfully ad hoc approach to tuning the clock, and we appreciate its simplicity.

Today on In Case You Missed It: Pairing an Arduino with a skateboard produces the Sick Ollie Machine, capable of measuring angular and X-,Y- or Z-axis accelerations to measure who is hitting their tricks the hardest. Courtesy of Josh Sheldon, the ollie machine uses an Arduino beneath the trucks of the board paired with a relay to measure the stats of each trick. Those who are producing truly sick ollies are rewarded with a chime from the attached cowbell.

Meanwhile, over at CERN a set of robot twins have been enlisted to provide live video feeds and environmental measurements for the massive underground complex. The robots, called TIM twins for Train Inspection Monorail, move along a -- you guessed it -- overhead rail that runs throughout the facility in order to monitor stats like oxygen concentration and radiation emissions.

Also, don't forget to check out what happens when a frog is run through Google's Deep Dream project (which is easily the weirdest sentence I've written yet today). As always, please share any interesting tech or science videos you find by using the #ICYMI hashtag on Twitter for @mskerryd.

Today on In Case You Missed It: Pairing an Arduino with a skateboard produces the Sick Ollie Machine, capable of measuring angular and X-,Y- or Z-axis accelerations to measure who is hitting their tricks the hardest. Courtesy of Josh Sheldon, the ollie machine uses an Arduino beneath the trucks of the board paired with a relay to measure the stats of each trick. Those who are producing truly sick ollies are rewarded with a chime from the attached cowbell.

Meanwhile, over at CERN a set of robot twins have been enlisted to provide live video feeds and environmental measurements for the massive underground complex. The robots, called TIM twins for Train Inspection Monorail, move along a -- you guessed it -- overhead rail that runs throughout the facility in order to monitor stats like oxygen concentration and radiation emissions.

Also, don't forget to check out what happens when a frog is run through Google's Deep Dream project (which is easily the weirdest sentence I've written yet today). As always, please share any interesting tech or science videos you find by using the #ICYMI hashtag on Twitter for @mskerryd.