Little notes
Short essays about hearts, light, and slow breathing — written the way I'd explain them to a friend at the kitchen table.
One slow minute: the breathing experiment your pulse can't ignore
Measure, breathe with a circle for sixty seconds, measure again — and meet your own vagus nerve in the difference.
The little red clip: why hospitals glow your finger too
That gadget on your finger at every checkup is doing the same optical trick as your phone camera — with sixty years of refinement behind it.
What your resting heart rate does — and doesn't — tell you
It's a wonderfully honest little number about your weeks, and a terrible oracle about your days. Knowing which is which is the skill.
How a camera can see your heartbeat
Your fingertip is a tiny red lantern, and every heartbeat dims it. The gentle physics of photoplethysmography, no equations required.