Flea Circus

Fact: A jumping flea accelerates faster than a space rocket.

The space rocket is a feat of human engineering. It accelerates so fast that astronauts have to undergo special training to withstand the powerful forces exerted on their bodies during lift-off. And yet, our mightiest machines pale in comparison to the humble flea.

Let’s crunch the numbers. If you jump out of a plane, you’ll accelerate at 9.8m/s2 – otherwise known as ‘g’. This means that after 1 second, you’ll be travelling at 9.8m/s. After 2 seconds, you’ll be travelling at double that, or 19.6m/s, and 29.4m/s after 3 seconds… you get the idea.

The acceleration that astronauts are subject to during liftoff is ~3g, which represents the fastest accelerating machine mankind has. A typical human can survive ~5g before passing out due to a lack of blood to the head. Fighter pilots wear special compression suits to help them survive the massive lateral g forces experienced during a dogfight (up to 9g).

A flea needs no suit nor any training to put our frail human bodies to shame. Immediately after jumping, a flea experiences g forces of up to 100g – or ten times what even the hardiest fighter pilots can survive. It’s not travelling fast – in fact, it only reaches a maximum speed of about 1m/s – but it reaches that speed incredibly fast, in a thousandth of a second, and it is this acceleration that exerts such massive forces.

How does the flea accomplish such a feat? It’s not all about having big muscles. Instead, the flea contracts its muscles over and over again and stores the energy in elastic, spring-like tissues made of a protein called resilin. This allows up to 100x the power of a single muscle contraction to be released all at once, which is what powers this exceptional jump. Think about it like drawing back the string of a bow, which allows you to fire an arrow far further than if you simply threw it.

Fleas aren’t the only animals to have built-in elastic bands. The famous tongue of the chameleon uses the same principle: check it out below for the obligatory slo-mo footage.

‘Another one of Mr Shaunak’s Little Bites of Science’
Image under Creative Commons License


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