I’ve been giving some thought to the various theories regarding the expansion of the universe. While we have known since Edwin Hubble first made his observations using the Doppler effect that the universe is expanding in all directions, it was not until 1998 when scientists where observing a Type La Supernovae that they discovered that the universe is not just expanding but also accelerating in all directions. This came as a big surprise to most in the scientific community since it was long believed that the pull of gravity would eventually slow things down following the Big Bang; causing all matter in the universe to fall back on its self.
While there are many theories that have attempted to explain this phenomenon, perhaps the most popular is a theory that some hypothetical “dark energy” is providing the motivation for this unexplained acceleration of the expansion of the universe. I want to propose instead that it might be a gravitational Doppler Effect that is the culprit.
The Doppler Effect occurs when frequency of light or sound or any other electromagnetic radiation coming from a moving object is compressed on the bow side of the object and expanded on the aft side. This can be most commonly experienced as a train passes by while blowing it horn. As the train approaches, the sound has an increased pitch as the sound waves are compressed at the front of the train. As the train passes, the pitch suddenly drops to a lower pitch as the waves are being stretched out by behind the now receding train. The same thing happens with light. In fact, if your eyes were sensitive enough you would see the train turn slightly red (red shift) as it approaches you then turn slightly blue (blue shift) as it moves away from you.
I want to propose that perhaps the force of gravity, which was predicted by Einstein and confirmed in 1993 by physicist Sergei Kopeikin to be limited by the speed of light and as such is also believed to propagate in waves, is doing the same thing. While gravitational waves have yet to be detected, if gravity does travel in waves then intuitively it would mean that if a large gravitational object like a star is moving, in a given direction, the gravity in front of that star would be slightly greater in the direction of its movement and slightly less in its wake due to the Doppler Effect. Essentially, the star would be propagating in front of it a greater number of gravity waves of a given amplitude which should cause a slightly greater curve in the space/time at its bow.
This “gravitational bow wave” in front of an object like a star in motion, might its self be a sort of self-perpetuating sort of accelerator. Because the gravity well in front of a moving object is deeper than the gravity well behind it, the object would perpetually seem to be falling into its own gravity well. It would be like constantly digging a hole in front of a ball rolling across the ground. Of course, this argument is predicated on the idea that the frequency of a given gravitational force wave influences the overall depth of a given gravity well by compressing waves of a given amplitude into a tighter space.
Additionally, if the strength or Amplitude of gravity waves diminishes over the time the way that other waves passing through a medium lose strength by imparting energy into the medium, we should also be able to predict that the blue shifted gravitation waves propagating to the aft of a star should travel farther then their red shifted counterparts on the bow of the star. This would essentially mean that the gravity left in the wake of a moving star would be stronger at a greater distance or have a greater effect on distance objects.
Essentially, stars and galaxies at a greater distance from the center of the universe would appear heavier and have a stronger gravitational pull on stars near the center. Because the lower frequency waves travel farther, much like the low frequency bass at a concert can be heard at greater distances than the high frequency treble, the objects in the outer universe should be pulling with slightly greater force than those at the center. This should cause a net gain in acceleration, at least near the center of the universe. A measure of the rate of acceleration for objects near the center of the universe versus the rate of acceleration for those objects at the distance reaches of the universe should show whether this theory is at all probable.
For certain, the study of gravitational waves will for some time be at the heart of our attempts to understand what is perhaps, the least understood primal force known to man, Gravity. We are now only beginning to ponder how gravity affects the fabric of space as it propagates around the universe, not as a smooth interconnecting force but as a complex interplay of elemental forces moving in waves.
While I will say again that I am certainly no physicist, we should all remember that great discoveries are regularly found by amateur astronomers. Within the world of Theoretical Physics, while few of us have the mathematical backgrounds necessary, we should all remember the words of Albert Einstein who said,
“Imagination is more important than knowledge.”
…and one more quote,
“A person who never made a mistake never tried anything new…” – Albert Einstein
[Originally published @ Utah Free Press dot com, September 2010]