After putting the data into Einstein’s model, it turns out that one chocolate biscuit should satisfy the daily energy requirements of 200 million people. So what’s the problem?
Physicists are excellent at juggling energy: they add it, take it away, multiply and divide it; convert it from one form to another. However, if you ask them a simple question, such as how much energy does one biscuit really have, the trouble begins.
A cosmic relay
The packaging says that one biscuit from the pack weighs 13.5 grams and contains 67 kcal, i.e. 280 kJ (joules and calories are simply two different units for measuring energy, in the same way kilometres and miles are two different units for measuring distance). After eating the biscuit, that amount of energy is added to my body’s ‘energy pool’, which allows me, for example, to click away on my keyboard for half an hour in a seated position, or spend five minutes sprinting. And here we have a textbook example of the conversion of energy: from chemical energy, in the fats and sugars of biscuits, to kinetic energy, i.e. movement. If we were to examine the cells of my muscles under a microscope when they receive the order “Contract!”, we would observe that the adjacent molecules of actin and myosin move relative to each other in response to this order. The change in shape of these molecules is precisely that fundamental moment when chemical energy is changed into movement. Each time the actin molecules bend, this