Millions of years ago, hot water was trapped inside this crystal, as it cooled it contracted forming that vapour bubble you see moving around within the liquid
If reheated till the bubble absorbed, you get the temperature in which the crystal formed 1/
https://t.co/3eJGnj9IJl
The Rijksmuseum has just published the largest and most detailed ever photograph of The Night Watch on its website, making it possible to zoom in on individual brushstrokes and even particles of pigment in the painting https://t.co/jxQRaA0ZfM