Wimpy Gravity

One great unsolved question in physics is why gravity is so weak compared to the other three forces of nature? This fact is not intuitive at all to many of my students whose experience gravity is that it is ever present, unforgiving, and at times brutal.

The Earth is huge, and acts unrelentlessly to pull us towards its center. This lack of an ability to jump even 3 feet in the air, or for the best athlete in the world to jump 8 feet in the air (Mr. Javier Sotomayor), makes us respect this downward-pulling force.

What we perhaps take for granted is that we also do not actually sink towards the center of the Earth, as the Earth would have it. Instead, the electrons in our skin, or in the soles of our shoes, repulse the electrons in the ground. We triumphantly stand firmly on the surface of the Earth.

In this same vein, we can also take a magnet and use it to lift up a paper clip. What power we have to combat the gravitational pull of the entire Earth by employing the humble refrigerator magnet! In both examples, we see evidence that the force of electricity and magnetism is significantly stronger than that of gravity. So why is gravity so weak?

One proposed model states that gravity is actually not weak, but is merely mostly drawn out into “extra dimensions.” The model, however “science fictiony,” purports that there are not just the four dimensions we are accustomed to of length, width, height, and time, but also other dimensions. These “extra” dimensions are very small and as yet unseen, yet large enough to “absorb” most of the gravitational force.

If true, then there is the prediction that the gravitational pull between two objects, Newton’s inverse square law for gravity, should break down on small scales. Experiments are underway now to search for such differences in Newton’s supposed “universal” law of gravity, ranging from the mighty Large Hadron Collider at CERN to tabletop experiments in physics labs.

Dr. Brenda Frye

About Dr. Brenda Frye

Brenda L. Frye is an observational cosmologist at the Department of Astronomy/Steward Observatory, University of Arizona. She earned her Ph. D. in Astrophysics from the University of California at Berkeley, assisted by a National Science Foundation Graduate Research Fellowship.

Her thesis work involved measuring the concentration of the total mass of visible plus dark matter in the fields of massive galaxy clusters, a program requiring the use of some of the largest telescopes in the world.

Moving a mile from her Ph. D. institution, she assumed a postdoctoral position with the Supernova Cosmology Project at Lawrence Berkeley National Laboratory under the direction of Professor Saul Permutter.

She then treked across the country to take a National Science Foundation Astronomy and Astrophysics Postdoctoral Fellowship and a Princeton Council on Sciences and Technology Fellowship both at Princeton University.

Moving further east, she became a Lecturer in Physics at Dublin City University in Dublin, Ireland, where a number of European collaborations were formed.

From there she crossed back across the pond to the west coast of the U. S. to become a tenure-track Assistant Professor of Physics at the University of San Francisco.

Her travels have now landed her at her Alma Mater in Tucson, where she teaches and does research. The aims of her research continue to be to use gravitational telescopes in space as 'lenses' to study the properties of dark matter and those of distant galaxies back to when the universe was <900 million years old.

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