1. In 1945, the US Army conducted the first nuclear weapons test, as part of the Manhattan Project. Since then, there have been over 2,000 nuclear explosions around the world.
![© Getty © Getty](https://c02.purpledshub.com/uploads/sites/41/2018/08/GettyImages-615305114use-2bea995.jpg?webp=1&w=1200)
2. Each nuclear explosion releases several hundred grams of the radioactive isotope caesium-137. This has a half-life of about 30 years, so it is not normally found in nature.
![© Getty © Getty](https://c02.purpledshub.com/uploads/sites/41/2018/08/3003241488_736ccd9fbbuse-9be52a4.jpg?webp=1&w=1200)
3. Caesium-137 dust gets dispersed in the atmosphere and reacts with rainwater to form soluble salts. From there it is absorbed, in tiny quantities, by plants through their roots.
![© Getty © Getty](https://c02.purpledshub.com/uploads/sites/41/2018/08/GettyImages-166640006use-87114f4.jpg?webp=1&w=1200)
4. Although it is quite safe to drink, any wine bottled after 1945 has detectable amounts of caesium-137 and this can be used to spot fake bottles claiming to be much older.
![© Getty © Getty](https://c02.purpledshub.com/uploads/sites/41/2018/08/GettyImages-520871816use-e9c047d.jpg?webp=1&w=1200)
Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.