Everyone knows gravity, which ensures that we keep our feet on the ground. As well-known as it may be, physicists have struggled with it for centuries. Science journalist Martijn van Calmthout wrote an excellent book about it.
In the Panthéon in Paris, Foucault's pendulum swings back and forth. A weight hangs from a long rope that does not touch the ground. After a while you see that the ground has changed in relation to the pendulum and so the invention shows that our planet is spinning. Those garlands come in all shapes and sizes, but the one in Paris is the most startling. This is due to the size and because inventor Léon Foucault hung it all himself.
In the book 'Echt Zwaar', the Frenchman plays a key role. In his book in the Panthéon, author Martijn van Calmthout explains to him how physics struggles with gravity. Foucault is of course a fictional character, he died in 1868, but this works wonderfully well. Van Calmthout takes the reader by the hand and explains expertly and passionately which studies have been done into gravity. And in the background, Foucault's pendulum swings back and forth.
The subject was well chosen by the Volkskrant journalist. Everyone knows gravity, but we still don't fully understand it. Van Calmthout discusses the most important insights and theories, in which Aristotle, Isaac Newton, Albert Einstein and Erik Verlinde are discussed.
This book also pays attention to Delft. For example, the author discusses Simon Stevin (1548-1620) drop tests on the tower of the Nieuwe Kerk. And the professor of geophysics Felix Vening Meinesz (1887-1966), who worked at TU Delft, among others, will be reviewed. He took a chest with him on his travels, 'a true treasure chest' according to Van Calmthout. It contained the notes and records of measurements of gravity on the high seas. Vening Meinesz discovered with a self-made measuring device, among other things, that there were large variations in gravity above the seabed.
That's because you can best imagine the earth as a "messy currant with bulges and pits." The earth does not have a perfectly symmetrical internal structure, which means that the gravity in some places is weaker or stronger than elsewhere.
It is these kind of relatively unknown stories about a well-known subject that make this book so interesting. Van Calmthout knows how to tell the right stories about gravity to share his enthusiasm with the readers. Moreover, he explains it all in an accessible way and yet with the necessary depth.