E = mc²

It may be the most famous equation: E = mc².

It came to the public with a 1905 publication by Albert Einstein. Even people with no real interest or ties to science tend to know the equation. The vast majority of people who know of and can tell you the equation have no idea what it means.

In 1905, Einstein finally completed his doctoral thesis on “A new determination of molecular dimensions.” But he also published four groundbreaking papers that banner year in the German journal Annalen der Physik (Annals of Physics).

One paper  (“On a heuristic point of view concerning the production and transformation of light”) proved that light could behave as a particle as well as a wave, and gave rise to quantum theory.

In another paper, he used Brownian motion (the irregular movement of small but visible particles suspended in a liquid or gas) to prove empirically that atoms exist.

The third paper, “On the electrodynamics of moving bodies,” presented his theory of Special Relativity, which deals with the way the speed of light affects the measurement of time and space.

And on September 27, 1905, he submitted a paper that asked, “Does an object’s inertia depend on its energy content?” This is where he used the equation E = mc².

It translates to mean that energy (E) equals mass (m) times the speed of light squared (c²) and that this reveals that matter and energy are deeply connected.

The equation came from his work on Special Relativity. While working through his calculations, he had an insight that surprised him. If an object emits energy, the object’s mass must decrease by a proportionate amount. Einstein actually wrote about it to a friend, “This thought is amusing and infectious, but I cannot possibly know whether the good Lord does not laugh at it and has led me up the garden path.”

Brian Greene explains it in this simpler way: “When you drive your car, E = mc² is at work. As the engine burns gasoline to produce energy in the form of motion, it does so by converting some of the gasoline’s mass into energy, in accord with Einstein’s formula.” To get the energy to move the car you have to lose some gasoline.

Einstein’s original thoughts and certainly not his intention was the discovery that a small amount of mass can be converted into a large amount of energy. This was what would eventually lead other scientists to the development of nuclear energy, and the atomic bomb.

The atomic bombs that destroyed Hiroshima and Nagasaki used less than an ounce of matter into explosive energy.

Brief Lessons from the Edge of the Ocean of the Unknown

loop quantum gravity  via commons.wikimedia.org

The gravitational field is not diffused through space; the gravitational field is that space itself. An entity that undulates, flexes, curves, twists. We are immersed in a gigantic flexible snail-shell. A colourful and amazing world where the unbounded extensions of interstellar space ripple and sway like the surface of the sea.

That rather poetic description of the physics of gravity comes from theoretical physicist Carlo Rovelli. He wrote a series of articles that are collected in a brief (78 pages) book about ideas in physics.

Seven Brief Lessons on Physics has no math, no relativity, quantum physics or string theory. Some reviewers compared it in intent to Richard Feynman’s “Six Easy Pieces: Essentials of Physics Explained.” Simple explanations for general readers.

Rovelli is one of the inventors of loop quantum gravity. Not a topic he covers. That theory says that space is not continuous but it is made of grains, significantly smaller than an electron, and they are linked to each other forming a network. He sticks to the classics.

There are excerpts and audio of the author at www.sevenbrieflessons.com

In his seventh lesson, he is both in awe of what is ahead for us and also surprisingly pessimistic about out time on this planet:

I believe that our species will not last long. It does not seem to be made of the stuff that has allowed the turtle, for example to continue to exist more or less unchanged for hundreds of millions of years; for hundreds of times longer, that is, than we have even been in existence. We belong to a short-lived genus of species. All of our cousins are already extinct. What’s more, we do damage. There are frontiers where we are learning, and our desire for knowledge burns. They are in the most minute reaches of the fabric of space, at the origins of the cosmos, in the nature of time, in the phenomenon of black holes, and in the workings of our own thought processes. Here, on the edge of what we know, in contact with the ocean of the unknown, shines the mystery and the beauty of the world. And it’s breathtaking.

Mapping the Universe

From the first lunar atlas -1647

A lot of us think of mapping the universe as starting with people like Galileo and the invention of the telescope, but obviously we have ben looking to the heavens and, perhaps in crude ways, trying to put it down and record what we saw for a much longer time. This cataloging of the the heavens and making visible both what we see and later what we imagined was there or beyond is still going on, and I imagine it will continue well past all our lifetimes..

We know a lot now. This week NASAs' Juno spacecraft went into its orbit around Jupiter and we'll know even more. And yet we still have much to learn and discover.

Several articles on the www.brainpickings.org website ponted me to books about the ways we have imagined the shape and design of the uinverse. One of those is Mapping the Heavens: The Radical Scientific Ideas That Reveal the Cosmos by Yale theoretical astrophysicist Priyamvada Natarajan. Her premise is that the advent of modern cosmology and astrophysics is what has shaped our understanding of the universe and our place in it.

The book gets into the mapping of the invisible, such as black holes and dark matter, the accelerating expansion of the universe, the echo of the big bang, the discovery of exoplanets, and the possibility of other universes.

We are far beyond the earliest maps of the Sun and Moon and the attempt to describe why they - or was it the Earth? - was changing positions in the heavens.

The book and this kind of inquiry also reminds us that science will always be changing and incomplete, and that is a thing wonderful in the old full-of-wonder manner.

Astrophysics, say Natarajan, is using powerful tools to answer the same questions that our ancestors tried to answer through mythology:

Cosmology, perhaps more essentially than any other scientific discipline, has transformed not only our conception of the universe but also our place in it. This need to locate ourselves and explain natural phenomena seems primordial. Ancient creation myths shared striking similarities across cultures and helped humans deal with the uncertainty of violent natural phenomena. These supernatural explanations evoke a belief in an invisible and yet more powerful reality, and besides, they rely deeply on channeling our sense of wonder at the natural world. The complex human imagination enabled ancient civilizations to envision entities that were not immediately present but still felt real. Take for instance Enki, the Sumerian god of water whose wrath unleashed floods, or the Hindu god of rain and thunderstorms, Indra, whose bow was the rainbow stretched across the sky with a lightning bolt as his arrow. The most powerful myths are the ones that force us to take huge leaps of imagination but, at the same time, help us to remain rooted.

The Juno spacecraft entered orbit around Jupiter on the 4th of July this year (NASA/JPL-Caltech)

Ideas That Must Die

It wasn't my idea that some ideas need to die - actually, to be killed off. In This Idea Must Die: Scientific Theories That Are Blocking Progress , John Brockman looks at scientific ideas that have outlived themselves and are now blocking human progress. A controversial title for a controversial topic.

John Brockman is the publisher of Edge.org and he regularly challenges some of the world’s greatest scientists, artists, and philosophers to answer a provocative question crucial to our time. He is the author of many books including This Will Make You Smarter and This Explains Everything.

In 2014 he asked 175 people to ponder: What scientific idea needs to be put aside in order to make room for new ideas to advance? He got some surprising answers - and a book from it.

Steven Pinker dismantles the working theory of human behavior. Richard Dawkins renounces essentialism. Sherry Turkle reevaluates our expectations of artificial intelligence. Geoffrey West challenges the concept of a “Theory of Everything.” Nina Jablonski argues to rid ourselves of the concept of race. Alan Guth rethinks the origins of the universe.

If you're not a book reader, you might want to check out some of the website's questions and answers. One of the annual questions is "What to Think About Machines That Think."

In a similar vein, here's one big idea that is ruining physics - Infinity. Max Tegmark wrote on blogs.discovermagazine.com although it is a beautiful concept, it's not helping. He says that "The assumption that something truly infinite exists in nature underlies every physics course I’ve ever taught at MIT—and, indeed, all of modern physics. But it’s an untested assumption, which begs the question: Is it actually true?"