The speed of light, represented by the constant c, is generally defined as the speed of light in a vacuum, since the speed varies when it travels through materials like water or glass or air. Though mass can change the energy and direction of light-bending its path, for example, as a prism does-it cannot change the value of c, which is approximately 3.00 x 108 m./sec., or around 186,00 mi./sec (Christian). Albert Einstein noted that the speed of light in a vacuum never varies no matter who is observing it (Redd). A space ship observes a ray of light as having the same speed, c, whether the light is traveling toward it or away from it (Mastin).
The speed of light appears to be fundamental to the structure of the universe. Einstein’s equation relating mass and energy, E = mc2 relates the mass of an object to its total energy through the square of the speed of light (Christian). But Einstein’s work in relativity also implies that it is impossible for any physical object to ever achieve a velocity greater than c-or even to achieve that speed. This is because as a mass speeds up, it takes more and more energy to increase its speed. Einstein’s theory takes as an axiom that the speed of light is a constant, and that it would take infinite energy to make any mass particle-even a single atom-go that fast (Mastin). Since it is impossible to add infinite energy to any object, it is impossible to ever actually reach a speed of c.
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More recent research in physics, however, indicates that Einstein’s axiom may not be quite precise. Recent research indicates that the structure of space itself may alter the speed of light (Emspak). This is a result of a “vacuum” not being truly empty, but instead being a lot like a broth of “virtual” particles that can pop into and out of existence almost instantaneously. Since photos travel by being absorbed and reemitted by these particles, the specific makeup of the “broth” determines the speed of light in that locality (Emspak). Unfortunately, Emspak also notes that this does not mean that we can ever go faster than c, just that the specific value of c might vary very subtly in different areas of space.
- Christian, E. “General Physics: Speed of Light.” NASA Cosmicopia. 22 Dec. 2006. Web.
- Emspak, J. “Speed of Light May Not Be Constant.” LiveScience. 27 Apr. 2013. Web.
- Mastin, L. “Speed of Light and the Principle of Relativity.” The Physics of the Universe: Difficult Topics Made Understandable. 2009. Web.
- Redd, N. T. “Einstein’s Theory of General Relativity.” Space.com. 18 Sept. 2012. Web.
