Today, March 14th, is the birthday of one of the greatest physicists the planet has ever seen: Albert Einstein. Famous for his Theory of Relativity, he predicted the equivalence of matter and energy, as expressed in probably the most recognised equation ever, E=mc2. His calculations led to the conversion of mass into energy in the nuclear bomb, but a paper in Physical Review Letters has reported a use for this equation in the auto world.
One PekkaPyykko of the University of Helsinki has postulated that the lead-acid batteries used in cars have the ability to get your engine going thanks to special relativity. The lead-acid battery was invented in 1860 and is considered to be one of the technological triumphs of the 19th century. Its chemistry is well understood, but according to Dr Pyykko, digging deep into the battery’s physical chemistry does not solve the real mystery of how it works.
The lead-acid battery is basically a collection of cells, each of which contains an electropositive electrode made of lead and an electronegative electrode made of lead dioxide immersed in sulphuric acid. The lead electrode reacts with the acid and loses electrons, while the lead dioxide electrode absorbs them. If a conductive wire is run between the two, the electrons released by the lead electrode will run along it towards the lead dioxide one, generating an electrical current which powers the battery.
This has been tested and confirmed, but the question left unanswered was why lead and lead dioxide happen to be so electropositive and electronegative. The plot is thickened by the fact that tin, which contains many similar properties of lead, makes ineffectual batteries. So why does lead make a good battery and tin doesn’t, and where does Einstein come in?
Well according to Dr Pyykko, lead, as a heavier element than tin, has more protons in its nucleus, which means it has a stronger positive charge. This in turn means the electrons orbiting the nucleus are more attracted to it and travel faster – about 60% the speed of light compared to 35% in tin. Here comes E-mc2: The equation predicts that the kinetic energy of this extra speed makes lead’s electrons more massive than tin’s, making the electrons circle the nucleus more tightly.
All this means that lead would be less electropositive than the classic theory suggests, but that conversely, the lead dioxide compound would be more electronegative than previously thought. The tightly bound orbitals in lead dioxide act like wells, capturing falling electrons more easily.
With this theory mapped out, Dr Pyykko and his team made two computer models of lead-acid batteries, one which incorporated their theory and the other which did not. The model that included the relativity theory predicted results similar to the actual workings of a lead-acid battery. The model that excluded relativity saw roughly an 80% decrease in voltage.
So next time you start up your BMW in Cumbria, remember that Einstein had a hand in discovering how to get you to work in the morning!
In these inspiring lectures David Bohm explores Albert Einstein’s celebrated Theory of Relativity that transformed forever the …
This book offers a comprehensive, university-level introduction to Einstein’s Special Theory of Relativity. In addition to the p…
Written by two of the field’s true pioneers, Spacetime Physics can extend and enhance coverage of specialty relativity in the cla…
Relativity: The Special and General Theory Albert EINSTEIN (1879 – 1955), Translated by Robert W. Lawson (1890 – 1960) This is an…
Relativity and Quantum Mechanics are the two major pillars of 20th century physics, which together revolutionized our understandin…
THE SPECIAL AND GENERAL THEORY
A CLEAR EXPLANATION OF THE FAMOUS THEIRY
THAT BROUGHT ABOUT THE ATOMIC A…
* In November 1915, Albert Einstein completed his general theory of relativity and transformed the world of physics. This theory took Einstein’s earlier theory of special relativity, which applied only to objects in a constant state of motion, and generalized it to account for acceleration (hence the name general theory of relativity).
Special relativity explained in under three minutes