Brian Josephson is a really clever man who is an expert in how things behave on a really tiny, tiny scale - smaller than things we can even see! This is called quantum physics, and it can be super tricky to understand, even for grown-ups.
When Brian was just a young man, he came up with a really amazing idea. He suggested that if you take a tiny magnet (much smaller than any magnet you've ever seen) and you cool it down to really, really cold temperatures, something really strange could happen. The tiny magnet might start to behave in a way that normal magnets just can't do, by sending out waves of energy all on its own. This was a REALLY big idea, and it earned Brian a big prize called the Nobel Prize.
Now, Brian is still doing really cool work in quantum physics and trying to understand more about how the world works on a tiny, tiny, tiny scale. It's so cool that even though it's really complicated, sometimes grown-ups still need to explain it like we're 5 years old, just to understand it better!