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Watch That Speed Limit

Watch That Speed Limit


One of the few laws strictly adhered to in modern physics is that the speed of light is, was, and ever shall be 300,000 kilometres per second. Light represents the fastest speed attainable by anything in the universe. It is the universe’s speed limit. Nothing can exceed it.

In 1905, the 26-year-old Einstein challenged Newtonian physics by developing the idea that the speed of light is a constant for all observers, and his theory helped lay the foundation of modern physics. The constancy of the speed of light (usually designated mathematically by “c”) was the basis for Einstein’s famous equation E=mc2.

But almost a hundred years later two physicists questioned Einstein’s theory just as Einstein challenged Newton before him. Dr. Joao Magueido, a professor at the Imperial College in London, and Andreas Albrecht of the University of California, suggested that once upon a time, light moved much faster than it does today.

They proposed that immediately after the universe was born, the speed of light traveled at near infinite speeds and as the universe cooled, the speed of light quickly dropped to its present value.

This process might have been sort of like water changing into ice as temperatures fall. When the temperature of the universe dropped below a critical value, light “froze” at the speed we now observe.

What would make these two physicists come up with such a nutty idea? What made them brave enough to challenge the long-held tenet of physics that the speed of light shall be 300,000 km per second? Why would they set out to debunk Einstein’s theory?

Here’s why. Recently astronomers have discovered that no matter what direction anyone looks, the universe appears uniform with the same temperature, density and consistency. It’s as if a cosmic blender had homogenized the entire universe early in its history (assuming that there really was a long history). This observation of uniformity does not fit “big bang” theory.

To solve the thorny question of why opposite extremes of the universe should be so uniform, Magueido and Albrecht proposed the theory of a varying speed of light. If light traveled at its present speed, there is no way to equilibrate conditions, no way that physical forces could equalize temperatures or mix the cosmos so that it is all the same. Traveling at 300,000 km per second is simply too slow. At every stage of the universe’s existence, even when it was just a trillionth of a second old (assuming an expan- sion process), light from one end of space would not have had enough time to reach the other end.

But if in the infant stages of creation, light had moved much faster and could zip across space at near infinite speeds, then equalizing the temperature and homogenizing the early universe would be possible. This would hold even if space were called into existence in a form other than the big bang.

Another thorny question comes to mind: “How can the universe be young if the stars are old?” If a star is, say a million light-years from Earth, wouldn’t it take a million years for its light to reach us? Perhaps, if light never exceeded 300,000 km per second. Indeed, scientists believe that it has taken billions of years for some light to reach Earth. This is the reason most scientists believe that the universe is very old.

A changing speed of light would not only explain some of the great mysteries of cosmology such as why the universe is so uni- form, it would also explain how distant starlight could reach Earth in a short time frame and not have to take billions of years. (Other explanations for a short time interval are possible too.) At any rate here we see secular scientists coming up with an explanation which could drastically reduce the estimated age of the universe. Maybe the universe is not that old after all!

Josh Munan
April 2007

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