How Does Light Travel

Light is one of the most enigmatic of things in the universe. Imagine a world without light and you will understand how important a role it plays. You are not the first person to carefully reflect upon this question - 'How does light travel?'. From Galileo to Maxwell to Einstein, every one of the great minds has thought about this question and thanks to them we know the answer to this question. Still a lot remains to be known about light.

How fast does light travel? That's another question that needs an answer. Scientists have measured the speed of light travel to be 299,792,458 meters per second! It is the greatest speed that can be achieved. So far no object has been found to travel at a velocity that exceeds the speed of light! Speed of light remains constant in vacuum. In fact, one of the central pillars of modern physics which is the special theory of relativity, will crash if light speed was known to be exceeded by any other object. In short, light is the fastest thing in our universe and no information can travel faster than light. How does light achieve this phenomenal speed? How does light travel at all? Let us look for an answer to this question. Read more on 'What is Einstein's Theory of Relativity'.

How Does Light Travel Through Space?
To answer the question raised which is - 'How Does Light Travel?', one must first ask the question, 'What Is Light Made of ?'. The answer to the former question lies in the answer to the latter one. One can understand how does light travel, once one understands what is the nature of light.

The nature of light was fully explained by the ingenuity of James Clark Maxwell. It came as a brilliant revelation to him as he was constructing a theory that describes the electric force and magnetic force between stationary and moving charged objects! He discovered that electricity and magnetism were two sides of the same coin! His theory combined electricity and magnetism into the unified force of electromagnetism and light was found to be an electromagnetic wave!

Light Travels Through Space as An Electromagnetic Wave
So light is a kind of wave! However every wave, waves something. That is every wave like a sea wave travels through a medium in which it causes disturbances and makes undulations. A sea wave is a ripple or a disturbance that travels through water then what is the medium in which light travels as a wave? The answer is none! This is where light is different from any other kind of a wave. It can travel through vacuum and it does not require a medium to propagate.

How does light manage to do this? The answer lies in the fact that it is an 'Electromagnetic Wave', carrying electromagnetic energy in it. Maxwell discovered how light travels through vacuum. Any charged object has an electric field associated with it, when the electric field associated with an object changes, a changing magnetic field is created. Then a changing magnetic field again creates an electric field! This is how an electromagnetic wave, that is light travels. It travels as a disturbance or ripple in the electromagnetic field.

Visible light, radio waves and even X rays are all electromagnetic waves that constitute the electromagnetic spectrum! They are all electromagnetic waves of different wavelengths and frequency, but they all travel with same speed, which is that of light in vacuum! Wavelength of visible light spectrum is such that our eyes are tuned to it like a radio receiver is tuned to a radio wave! That is why our eyes can see that part of the electromagnetic spectrum. Read more on 'Properties of Electromagnetic Waves'.

Light travels in straight lines in vacuum. However in a material medium, light shows two properties of reflection and refraction. When a light wave cannot penetrate an object, it gets reflected back and when a light wave travels inside a medium which it can penetrate, it bends or gets refracted. When light travels through a medium, it interacts with the electric field of that medium and depending on nature of that electric field, one can tell how much will light bend or get refracted in it.

If you are wondering 'how does light travel through air', your question has already been answered. It travels as a disturbance in the electromagnetic field. If you are wondering how does light travel through the eye, then the answer is the same as that of air. Only in the eye case, light entering inside the white of your eyes bends or gets refracted, to get focused on your retina. The retina converts the incident light into electric signals, from which your brain creates an image, which you see!

This was a rather simplistic explanation of how does light travel through space. There are many more complications associated with light. In fact, it also behaves as a particle! More on that later when I am in a 'lighter' mood again!