John William Strutt, 3rd Baron Rayleigh was a really smart man from a long time ago who figured out lots of important things about the way the world works.
He studied how things like light and sound move through the air and how different materials can affect them. He even came up with a fancy scientific term called "scatter" that explained why we see the sky as blue during the day and different colors at sunset.
But that's not all! Lord Rayleigh was also really good at mathematics and physics, which are like super-duper hard puzzles that help us understand the natural world. He used his brain power to solve tricky problems about vibrations, waves, and energy.
And even though Baron Rayleigh lived a long time ago, his discoveries are still really important today. Scientists and engineers use his theories to make things like better microphones and speakers, and to understand how earthquakes and ocean waves work.
So, in summary, Baron Rayleigh was a clever man who helped us understand how things move through the air and how we can measure vibrations and waves.