You probably have a microwave oven in your kitchen, and how useful it is! You can thank science for that. But even if you don’t have one, you cannot get away from microwaves. You can go into the garden, in a desert, on the ocean or into space, they are everywhere. No hiding place! Fortunately those natural ones have much too low frequency and intensity to cook you or harm you in any way, and microwave ovens will not work with the door open.
Microwaves are oscillating electric and magnetic fields, electromagnetic waves for short, travelling at the speed of light. But ironically you can keep them inside a box – your oven. Radio waves oscillate more slowly, while infrared – or heat rays – oscillate faster. Light is the same thing oscillating faster still.
A red hot poker cooling in a dark room becomes black, but still radiates heat. Then it cools further and radiates microwaves, lower temperatures corresponding to slower oscillations. Even you radiate microwaves, as well as heat, especially on a cold day.
Once upon a time, 13.8 billion years ago, the whole universe was for an instant the size of a baseball and unimaginably hot. It expanded – very fast – and cooled, briefly being full of blue light, then white light, then red light, anticipating the colors of our flag! Today the whole universe is full of microwaves corresponding to a temperature of about -270o Celsius. That’s cool! Nothing can be colder than -273oC!
This “Cosmic Microwave Background”, CMB, was predicted by the Big Bang theory, and discovered by Bell Labs scientists Penzias and Wilson while they were experimenting with satellite communications. Currently, it is being studied by special telescopes in space and, with Fermilab involvement, at the South Pole. The CMB is almost exactly the same in all directions, after correcting for the speeding of the Earth toward the constellation Leo at 369 km per second.
Scientists have discovered that it is blotchy, with patches warmer by only one thousandth of 1 percent. We believe the patches started out as microscopic quantum fluctuations at the Big Bang, which grew, as the universe expanded, to become galaxies and stars. This is the most amazing story, backed up by all the tests done so far.
So microwaves can have a wide range of wavelengths, or temperature, and strength. Cold and weak they fill the universe, hot and strong they warm drinks and cook food.