Light is more than what meets the eye.

Yes, the reason you can see the sunset and watch your favorite television show is because of light. However, there is so much more to it than that.

What is Light?

Our universe is swarming with incomprehensibly small waves of electromagnetic radiation that vary in size and property. The sizes of waves range from three meter radio waves to .01 nanometer gamma rays (1 billion nanometers = 1 meter). Visible light, on the other hand, is classified as electromagnetic waves that are between 400 and 700 nanometers. So, how do these tiny, seemingly insignificant waves create light?

The Process

As you can see, light is not as simple as tiny, massless particles, known as photons, moving around, as many people believe. Photons do, however, play a role in what light is. So, how are photons and electromagnetic radiation related? Before we answer that question, let's talk about how photons are created. In a molecule, electrons revolve around the nucleus in what are known as orbitals. There are different levels of orbitals, ranging from ones closer to the nucleus, to ones further away. These different shells hold electrons of varying amounts of energy. The further away from the nucleus an electron is, the more energy it will have. Therefore, when an electron goes from a higher shell to a lower one, it will release energy in the form of a photon. This process is known as emission. In the same way, if an electron in its ground state encounters a photon, it will gain energy and jump to a higher energy shell, which would make it in its excited state.

Light.

Now, you might be a little confused on whether light is made up of tiny waves or photons. The truth is that the two go hand in hand to produce light. This is because the electromagnetic radiation that creates light as we know it is composed of photons, just like the waves of the ocean are made up of water molecules. The varying sizes of waves come from the photons having different amounts of energy. Photons with more energy will have shorter waves, while photons with less energy have longer waves.

So, what makes it so that only this specific range of wave length is visible to us? This is simply because our eyes are only able to see this size of electromagnetic waves. However, some animals are able to see ultraviolet or infrared light, which are near visible light on the electromagnetic spectrum.

Let's See...

Because light isn't some magical beam coming from different directions all around us, it can be manipulated by physical objects, such as glasses and magnifying glasses. The way that these objects work is by altering the path of the light and bringing it together. Sometimes in movies it is portrayed that sunlight passing through a magnifying class can light something on fire. This is indeed possible due to the fact that a magnifying glass concentrates the light into one spot, which can start a fire. The rays of light that hit the magnifying glass are known as the incident rays, and once they are altered by the magnifying properties, are turned into converging rays.

Color

The different colors that humans see are due to the sizes in electromagnetic waves that meet our eyes. The reason that certain objects seem to be different colors than others, is due the arrangement of electrons within an atom, which alter what wavelength of light the atom will absorb, and therefore which it will reflect. The reason that white and black aren't on the electromagnetic spectrum is because black is simply the absence of visible light, while white is formed by all of the colors in the visible light spectrum. When put in a light prism, white light gets separated into its spectrum of colors. This process is known as dispersion.

Where things get crazy

The reason that black holes appear completely void is because no light can escape them. However, why does this happen? Is it because the gravity of a black hole pulls all light into it? No. As mentioned earlier, photons are massless. So, the immense gravity of a black hole would not be able to affect them. Instead, the black hole's gravity warps space-time around the photon, as explained by Einstein's Theory of General Relativity, and alters the path of the light. This warping of space-time is known as space curvature. The new path create by space curvature from the black hole makes it so that the light has no where to go, except into the black hole. This only happens to light particles within the event horizon of a black hole. The distance between the center of a black hole, its singularity, and the event horizon is known as the Schwarzschild Radius. It is within this radius that even light is not fast enough to escape. However, outside of the event horizon, the immense friction between molecules caused by the gravity of the black hole creates very bright light, which is why black holes aren't completely black. This part of the black hole that emits light is known as the accretion disk.

Things take time

Although light is the fastest thing in the universe, travelling at 299,792,458 meters per second, it isn't instantaneous. So while objects close to you will be seen exactly as they are, since their light will reach you instantly, others that are further away won't be the exact same in reality as when their light reaches us. In order to explain this, let's give some background. The distance that light can travel in a year, approximately 9,460,730,472,580.8 kilometers, is known as a light year. This is significant because if an object is one light year away, when its light reaches us, we will see it as it was one year ago. This means that if the sun disappeared, we would not notice it for ~8 minutes, because it's light takes 8 minutes to reach us. So for 8 minutes after it disappears, it's light will still be traveling to Earth, until there is none left and we have realized that it disappeared.

Dedicated to Jaron Hung (www.jaronhung.com)