Mystery #1Tier 2heart / circulation
Why does your heart beat?
Right now, without you thinking about it, a fist-sized muscle in your chest is squeezing and releasing about once a second, and it has been doing that since before you were born. You can hold your breath, but you cannot tell your heart to stop. What is making it beat, over and over, all day and all night, with no rest at all?
Your guess
What's your hunch about what makes your heart keep beating without you ever telling it to?
There's no single magic word to type, have a go in your own words, then reveal the answer to see how close you got.
Make a guess to unlock the hints and the answer.