Light makes vision possible and provides us with most of our information about the universe.

Light is a form of radiant energy that we can see with our eyes, and record with film and digital cameras. Light's interaction with our visual system causes the sensation of vision in our mind.

Over the immensity of geologic time, our eyes have developed into organs that have the ability to sense light, and give us our primary information about the world. Our consciousness is directly interfaced with the rest of the universe through light. But the nature of light and its perception by our visual system is not completely understood because it involves two of the deepest mysteries in nature - human consciousness and quantum mechanics.

Photons, the elementary particles that make up light, are everywhere at once. This is because from a photon's perspective, time does not exist. Einstein's theory of relativity predicted, and scientists have proven, that as objects are accelerated, time slows down. At the speed of light, which photons travel at, time stops. For a photon created and emitted at a far-away star, and visually observed or recorded with a camera by us here on Earth, the photon exists at both ends of its journey as well as all locations between simultaneously.

From our perspective as observers who are travelling much slower than the speed of light, a photon from the Andromeda galaxy seems to take about 2.5 million years to reach us. But from the viewpoint of the photon, the trip happened instantaneously.

Both viewpoints are valid. This was the great revolution in thinking that was brought about by Albert Einstein's theory of relativity - there is no fixed frame of reference.

Light - The Bottom Line Photons can also be collected by our digital cameras to produce images that reveal more than our eyes can see alone, even with the help of a telescope. This is the magic of long-exposure deep-sky astrophotography, and it is light that makes it possible.