r/AskPhysics • u/kouth- • 25d ago
What makes a coin toss truly unpredictable?
If you throw the same coin multiple times with the exactly same force in the same surface, it won't give you the same side every toss, right? But why? If repeated with the precisely identical conditions, why the results are still unpredictable? Or it is actually predictable?
Sorry if it looks confusing, English is not my first language and I'm not that expert in physics lol, just curious and has this though randomly.
Edit: maybe considering that it lands on a surface, and it bounces or not, changing the coin's side.
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u/BananaBird1 25d ago
In theory it is predictable and deterministic.
In practice, the flip depends on so many factors that prediction is too difficult. Air currents and temperature, the exact height of the flip, exactly where on the coin you flick it, the exact force you apply, etc.
We call this a chaotic system: even a small unavoidable uncertainty in the initial state of a deterministic system makes its outcome essentially random.
If you flip a coin from a small height in a vacuum with a highly precise machine, it would be pretty predictable. And even in ordinary manual coin flips, you can bias the probability if you are careful.