› added 4 years ago

71

TIL smartwatches measures blood preassure by emitting light to the skin and reading how much light is reflected back; as the heart pumps blood, it causes a variation in blood volume on the skin and can be detected by change in light absorption, a not-so-new technology called photoplethysmogram.

Read more wikipedia.org

via reddit.com

a8DGy TIL about the Euthanasia Coaster, a hypothetical steel rollercoaster designed as a euthanasia device to kill its passengers
1aP6W TIL The man who took the first up close photo of a snowflake, Wilson A. Bentley in 1885, also started the concept "No two snowflakes are alike". In his lifetime, he took over 5k photos of snowflakes.
OoQWR TIL the CEO of HSBC in Taiwan walked his lesbian employee down the aisle in 2017 after her parents refused to go to the wedding
4bgb TIL that earwax plugs from whales can be used to determine their age, much like tree rings. In 2013 a study examined a foot-long earwax plug from a blue whale to also determine when it was exposed to certain chemicals in the environment.
K5vR TIL there’s a Post Office at the bottom of the Grand Canyon. It serves the Havasupai Reservation and the town of Supai, and post arrives via mule on a 2 ½ hour journey each day.