Is The Speed Of Light Constant?

I am going to state two widely accepted truths here.

First and foremost, science is an interesting subject. Second, this is one of the most cliche statements imaginable.

Despite it being a cliché, science is indeed mysterious. Every once in a while, it comes up with something that was previously unknown to human civilization, which can completely change the way we look at the world – and our place within it. Although there are endless equations and laws of nature, science is totally unpredictable. Now, let’s talk about a long-standing belief that millions of people have depended on to solve problems in physics, chemistry, and dozens of other fields of study.

The Not-So-Constant Speed of Light


What comes to your mind when I say the ‘speed of light’?

Some might say high, extremely high, super-fast, or other such words that express the idea of swiftness. However, those individuals whose connection with science crosses the ‘worldly’ boundaries would say that the speed of light is ‘constant.’

Many of us have been taught that the speed of light is constant, racing through the universe at almost 300,000,000 meters per second. However, that is not the whole story.

Theories Supporting Variance in the Speed of Light

In a study led by Marcel Urban of the Université du Paris-Sud, it is claimed that the vacuum of the universe is composed of fundamental particles, like quarks, that are called “virtual” particles. Photons of light that move through space collide and are re-emitted by these virtual particles.

Have a nice look at the quark

Have a good look at the quark

Since at the time of collision the energy of these virtual particles can be absolutely random, it cannot therefore be said that the speed of light is constant throughout space.

Why Do We Assume That the Speed of Light is Constant?

A number of laws, theorems and derivations have a direct dependence on the fact that the speed of light is constant at approximately 300,000,000 meters per second. If this value were to change, then all of those laws and theorems would change dramatically.

The value of the speed of light has direct and complex implications in the fields of astronomy and cosmology. For instance, we need to use the value of the speed of light when determining the fine structure constant, which defines the strength of electromagnetic forces. If the value of the speed of light were to change (or not remain constant), then the strengths of molecular bonds and the density of nuclear matter would change. This would mean that everything we know about matter would become questionable and inaccurate.


You can be confident that the speed of light is 299,792,458 m/s in a vacuum when measured by someone situated directly next to the source. In other situations, however, the speed changes. Furthermore, you may not know that the speed of light decreases in certain media, such as air, water and glass. The ratio by which it is slowed is called the refractive index of the medium, and is usually greater than one.

To all the literary minds out there, if you’re worried that you will no longer be able to portray light as the swiftest of all things, don’t worry! The minute changes to our broader belief that we talked about here are not going to challenge the ultimate superiority of light. Even with these small inconsistencies, there is still nothing faster than light in the universe!


  1. Wikipedia
  2. Wikipedia
  3. LiveScience
  4. University of California, Riverside
The short URL of the present article is:
Help us make this article better
About the Author:

Ashish is a Science graduate (Bachelor of Science) from Punjabi University (India). He spends a lot of time watching movies, and an awful lot more time discussing them. He likes Harry Potter and the Avengers, and obsesses over how thoroughly Science dictates every aspect of life… in this universe, at least.

Science ABC YouTube Videos

  1. How Does A Helicopter Work: Everything You Need To Know About Helicopters
  2. Rigor Mortis, Livor Mortis, Pallor Mortis, Algor Mortis: Forensic Science Explains Stages of Death
  3. Why Is Space Cold If There Are So Many Stars?
  4. Tensor Tympani Sound: Why Do You Hear A Rumbling Sound When You Close Your Eyes Too Hard?
  5. Hawking Radiation Explained: What Exactly Was Stephen Hawking Famous For?
  6. Current Vs Voltage: How Much Current Can Kill You?
  7. Coefficient Of Restitution: Why Certain Objects Are More Bouncy Than Others?
  8. Jump From Space: What Happens If You Do A Space Jump?