Light moves only one way: in a straight line. But its path from point A to point B is always in the form of waves, and higher energy light travels at shorter wavelengths. Photons, tiny particles of energy, have been circulating in the universe since their first explosion in the Big Bang. They always travel through the vacuum of space at 286,400 miles per second – the speed of light – which is faster than anything else.

It’s sad that we can only see it up close with the naked eye 0.0035 percent light in the universe. Humans can detect only a small part of the electromagnetic spectrum: wavelengths between about 380 and 750 nanometers. This is what we call the visible part of the electromagnetic spectrum. It would be nice to look at the universe in this range, but our view misses wide ranges of wavelengths that are shorter or longer than this limited range. On both sides of the visible band is evidence for interstellar gas clouds, the hottest stars in the universe, gas clouds between galaxies, gas flowing into black holes, and much more.

Fortunately, telescopes allow us to see things that would normally remain hidden. We use detectors that can capture infrared waves to detect gas clouds between stars and galaxies. Super-hot stars require instruments that see short ultraviolet waves. We need X-ray detectors to see gas clouds between galaxies.

For over 60 years we have been using telescopes designed to detect unseen parts of space. Because Earth’s atmosphere absorbs most wavelengths of light, most of our telescopes must observe space from orbit or from space.

Here’s a quick snapshot of how we use special detectors to study how light moves through the universe.

infrared waves

We cannot see infrared waves, but we can. feel them as warmth. A sensitive detector like the James Webb Space Telescope can detect this heat energy from different parts of the universe. But we also use infrared radiation in more realistic ways. For example, remote control devices send infrared signals with a wavelength of about 940 nanometers to your TV or stereo. These heat waves are also emitted from incubators to help a baby chick hatch or a domestic reptile warm. As a warm being, you also emit infrared waves; A person wearing night vision goggles can see you because the glasses convert infrared energy into false-color optical energy that your eyes detect. Infrared telescopes allow us to see space in a similar way.

astronomers started first studies of the sky using infrared telescopes in the 1960s and 1970s. Launched in 2021, Webb uses the infrared spectrum to explore the deepest regions of the universe. Webb orbits the sun in truly cold space, about a million miles from Earth, and has three infrared detectors that can look further back than any other telescope to date.