Presto

“Reality is everything that exists. That sounds straightforward, doesn’t it? Actually, it isn’t. There are various problems. What about dinosaurs, which once existed but exist no longer? What about stars, which are so far away that, by the time their light reaches us and we can see them, they may have fizzled out?

We’ll come to dinosaurs and stars in a moment. But in any case, how do we know things exist, even in the present? Well, our five senses — sight, smell, touch, hearing and taste — do a pretty good job of convincing us that many things are real: rocks and camels, newly mown grass and freshly ground coffee, sandpaper and velvet, waterfalls and doorbells, sugar and salt. But are we only going to call something ‘real’ if we can detect it directly with one of our five senses?

What about a distant galaxy, too far away to be seen with the naked eye? What about a bacterium, too small to be seen without a powerful microscope? Must we say that these do not exist because we can’t see them? No. Obviously we can enhance our senses through the use of special instruments: telescopes for the galaxy, microscopes for bacteria. Because we understand telescopes and microscopes, and how they work, we can use them to extend the reach of our senses — in this case, the sense of sight — and what they enable us to see convinces us that galaxies and bacteria exist.

How about radio waves? Do they exist? Our eyes can’t detect them, nor can our ears, but again special instruments — television sets, for example — convert them into signals that we can see and hear. So, although we can’t see or hear radio waves, we know they are a part of reality. As with telescopes and microscopes, we understand how radios and televisions work. So they help our senses to build a picture of what exists: the real world — reality. Radio telescopes (and X-ray telescopes) show us stars and galaxies through what seem like different eyes: another way to expand our view of reality.”
― Richard Dawkins, The Magic of Reality: How We Know What's Really True