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August 9, 2009
Why Does E=mc2 ?
(and why should we care?)
A review of a marvelous new book on Einstein's relativity
By Scott C. Anderson
Brian Cox and Jeff Forshaw have summoned up the audacity to write a book on relativity for lay people. Although this has been attempted before, it has rarely been done so well. Stranger still is the inclusion of a few actual equations. In the title, no less! These are brave lads, indeed.
Steve Hawking was told by his publishers that each equation would cut his audience in half. So he decided on just one: E=mc2. What is it about this equation that emboldens authors to risk losing readers? For one, it's miraculous. And it doesn't hurt that everyone knows it anyway.
Hopefully, that publisher was just a misanthropic cynic. Our belief at Science for People is that the world is actually begging for information and can take a few equations in stride. Fortunately for the mathphobes out there, the equations are surprisingly mild. In order to develop the master equation of relativity, the only other formula the authors employ is the Pythagorean theorem: c2 = a2 + b2. So, if you survived High School, you can actually learn about the most famous equation of all time in just a few hours. Nice!
Cox and Forshaw know their stuff. As physics professors at Manchester University, they are used to dealing with beer-chugging undergrads. They both work at CERN, where the Large Hadron Collider has scared the pants off millions of gullible people with its potential to create black holes. Cox is something of a celebrity in Britain, starting in the 80s with his mop-headed rock band roots (keyboards for Dare and D:Ream) and continuing to his contemporary science presentations for the BBC.
Forshaw is a theoretical physicist, and like Cox, is at the forefront of particle physics research. These guys are intense, having reached professorhood at relatively young ages. That youthfulness helps a lot with their writing and makes the science sound fresh and fun. And that, exactly, is what they're after: to show how exciting and beautiful science can be. And mysterious, as well. Why in the world does mathematics work so well to describe nature? We have no right to expect that, but it can be spookily accurate. That relates to the Einstein quote at the top of our site: "The most incomprehensible thing about the universe is that it is comprehensible."
The book quickly and painlessly explains why E=mc2 with a simple appeal to geometry. Mere triangles, in fact – and that's where Pythagoras comes in. By page 43, you'll know why time is actually different when you're moving. Soon you find out why the speed of light is so profound – it paces the heartbeat of physics, defining space and time at a single stroke.
The book then moves on to why we should care. After all, Newton's physics was good enough to get us to the moon; do we really need the fine-tuning that Einstein added? Well, actually, yes. The first obvious manifestation is atomic power. As we have since demonstrated with devastating effect, the mass of a few pounds of uranium can be converted to world-shaking energy. The authors give a great feeling for how odd this equation was for the scientists of the time. Getting energy from mass made no sense to them – in fact, conservation of mass seemed to preclude it. Burning something to obtain heat was considered just a liberation of some mysterious latent energy. All in all, it was pretty ridiculous to imagine that such huge amounts of energy were somehow to be derived from such miniscule bits of mass. But c, the speed of light, is a huge number. Squaring it just makes it a crazy multiplier. Incredulous would be a fair summation of Einstein's first reviewers.
Einstein ultimately created an undeniably big bang, but there were other subtleties of the theory. Time and space were yanked from their static pedestals and morphed into stretchy fabric. Surely this was just metaphorical? No, these concepts also came directly from a basic understanding of the ultimate speed limit. If Einstein was right, time and space were suddenly wobbly. Still, the effects seemed safely out of reach. As long as we stayed humanly slow, it couldn't really matter, could it?
Well, yes. It's hard to believe that GPS systems are only a few years old, because we're already addicted to them. But without Einsteinian tweaking, they wouldn't work. Einstein insisted that time ticks faster on a satellite – and oddly enough he was right. If that time change isn't compensated for, your GPS would lose about 7 miles of accuracy every day. It would be useless on day one and go downhill from there. Bet you didn't know that!
This book is a wonderful introduction into the wild world of stretchy time, warped space and unbelievable energies. To think that the average citizen could grasp all this is marvelous. But in a world dominated by such important, impactful science, perhaps it's time to lose the illusion that we can survive without knowing at least some of these principles. Given how cavalier we've been with the environment, our very survival could depend on it. Give this book a shot, maybe we'll be able to save the planet after all!
Copyright © 2000-2014 by Scott Anderson
For reprint rights, email the author:
Scott_Anderson@ScienceForPeople.com
Don't wait another minute, just go buy this book:
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