Why Are Tomatoes Repelled by Magnets?

A Surprising Experiment

Every time we observe a magnet experiment up close, we should leave room for surprise. I still remember their high-speed collisions (careful if you try this at home) and their curious reaction to a classic material like copper. But today we're going to explore a more “organic” territory, if you will: the relationship between magnets and tomatoes, meats like bacon, and even condiments like Tabasco sauce. The key requires exploring the concepts of paramagnetism and diamagnetism, but at the end of the day, it's not that complicated.

Prepare a bowl of water. Place a support that acts as a raft and doesn't sink. Now, place an object on the raft and bring a strong magnet (one of neodymium, for example) near it. Basically, one of two things can happen: the object and the raft will try to reduce their distance from the magnet, or they will try to flee from it. Some metals (say, iron) will jump off the raft to stick to the magnet's surface, but there are other materials that react to the magnet even when we imagine they won't do anything. One of the most striking cases involves tomatoes:

The YouTube channel Ciencia de Sofá faced a small tomato with a magnet, and as strange as it might seem at first, it began to escape. The same happened with a piece of bacon (which, by the way, looked great) and with a sample of Tabasco sauce. The video does a solid job explaining the difference between paramagnetism (attraction) and diamagnetism (repulsion).

The Science Explained

If the orbitals of an atom contain a single electron instead of two, that enables the “free” electron to interact with an external magnetic field. On the other hand, when pairs of electrons in an atom behave like tiny moving magnetic charges and approach a magnetic field, what they do is generate their own magnetic field with the opposite polarity. Diamagnetism in action.

So what about the tomato? In reality, the interaction doesn't come from the tomato itself, but from the water it contains. The vast majority of substances are diamagnetic, and water tops the list. This is very similar to what we observed during the reaction between a giant neodymium magnet and a bucket full of blood. You can even try it at home. Get a magnet and experiment with different fruits and vegetables.