Light is the main and the most important thing that connects us with the universe. But, what is light? Light is the smallest quantity of energy, having the ability to be transported. It is created by some elementary particles called photons. A photon does not have size or mass; it cannot be separated; it can only be created or destroyed. A major characteristic of photons is that they travel fast, very fast. The speed of light in vacuum reaches almost 300 thousand km/s. According to Einstein, particles that do not have mass (such as photons) travel under a constant speed, but the reason why they travel at this particular speed is something that it is not known yet. On the other hand, there are a lot of known things about light. Two of the most common properties it has are its ability to reflect and refract.
When traveling through an empty space, light’s speed is at its maximum, but when it travels through other media, its speed may slow down. Electrons inside atoms of some particular materials, slow the process of light passing through them, as light passes from one electron to another, causing it to bend or refract. One great example about that are diamonds and their ability to sparkle. Diamonds are one of the strongest known materials. They are so dense that they are able to slow the speed of light at half. Also they can refract light in all of directions- sparkle it into every color of the rainbow.
The main reason why light slows down in such materials is related to electrons. In some way light interacts with the electrons present in every atom. Understanding this would be a bit difficult, but it can be imagined like a change of path for light`s rays, every time they meet an electron. Changing the light`s path in every direction causes it to bend, reflect or distort, therefore slowing down its speed.
Diamonds play the reflecting trick better than any other material. Light enters a faceted gemstone from all sides, and it may bounce back and forth several times inside it before it finds a clean, straight shot out (Hazen,1999). All this changing in lights direction accomplishes something really amazing- showing each color a human eye is able to see. All colors-red, orange, yellow, green, blue, and violet-bend and reflect inside a diamond a bit more different, a bit more beautiful.
Aristotle was one of the first early great minds that thought about images as compositions made of light. Human eye can only see because of the existence of light. The phenomena of reflecting or refracting, sometimes causes the distortion of images.
Until now, light has been the major assistant for us to observe the universe. Images of stars and galaxies seen through telescopes are possible thanks to the light that travels constantly throughout the space. Recently, Hubble Space Telescope has captured the same image of a galaxy different times. All that due to the changing direction of light while traveling through dark matter. For the first time, a cosmic magnifying glass has allowed scientists to see the same star explosion four times, possibly offering a revealing glimpse into these explosive stellar deaths and the nature of the accelerating universe.
The four images of the supernova each appeared separately over the course of a few weeks. This is because light can take various paths around and through a gravitational lens, arriving at Earth at different times.
A hypothesis about photons is related to time. It is believed that for a photon time does not exist. While a photon is traveling through space, at the same moment it experiences the beginning and the end of our universe; the creation and the very end of our history, since the time we first walked this Earth. Certainly light is an amazing phenomena, yet to be explored and understood.