Have you ever learned about where rainbows come from? Even though it looks sort of like a beautiful structure in the sky, a rainbow is actually a really neat band of colorful light! Rainbows form from the bending and splitting of light (which contains a huge spectrum of colors) that happens when droplets of water are hit by light at just the right angle.
So, the main reason why a rainbow can’t be captured is that a beam of light isn’t really something we can hang on to! Unlike a flashlight or a lamp in your house, whose light you may be able to shine onto your hand, a rainbow is so high up in the sky that you’d never be able to reach. (Not even with the tallest ladder!)
Even the “end” of the rainbow (which looks like it touches the ground) wouldn’t be a good place to make your catch because there actually is no such thing! Although we sometimes see a rainbow intersecting with the horizon off in the distance, this is just the point at which our view is cut off. – If you were able to see a full, uninterrupted rainbow from way up high (like a bird), you’d actually see that its complete shape is a circle, suspended up in the sky above us!!