100 years ago, Albert Einstein formulated the equation E=MCSquared, that expresses Einstein’s theory that as one accelerates an object, it not only gets faster, but gets heavier. I must admit it is not very often that I come across the anniversary of a theory like this. We normally mark dates of births, deaths, battles, elections or great reforms. Theories don’t quite have the same resonance. I don’t imagine that there will be grand parades marking Einstein’s achievement.

I have read a bit about this incredible man and his life, and to this day I’ll frankly admit to finding it pretty hard to get my head around some of the ideas of relativity. (Physics was never one of my stronger subjects, something I intend to fix at nightschool. Never too late to learn). But there can be no doubt at all about the impact this man has had on the subsequent 100 years, in terms of our understanding of the universe and of course in fields such as nuclear power, both in its benign and not-so-benign forms.

And Einstein of course is incredibly famous not least for personifying the “eccentric genius” with his mass of scruffy hair, wild-eyed expressions and casual manner. How often are scientists in the movies, television and theatre portrayed in this way (assuming that scientists are portrayed at all). More recently, the late great Richard Feynman continued the tradition for iconoclastic irreverence, famously deflating science establishment in a marvellous collection of books about science and public policy.

For those interested in Einstein’s contemporaries in the science community in America, I can strongly recommend this book by Ed Regis.

One of my favorite Einstein stories is about the letter to President Roosevelt. Leo Szilard went to meet with Einstein at his vacation home on Long Island to talk about sending the letter to FDR. But Szilard, one of the brightest physicists in the world, didn’t drive. The simple solution was to have Edward Teller serve as his chauffeur!

Johnathan quotes the BBC: “that expresses Einstein’s theory that as one accelerates an object, it not only gets faster, but gets heavier”.

This is not correct. The Newtonian equation F=ma is what the BBC is refering to.

E=mc(squared) basicly states that all matter is highly condensed energy. Hence, transforming a small amount of matter into energy can yield a nuclear blast.

This is not correct.Jonathan and the BBC have got it right, they are referring to this

Actually, speaking as a physicist, so far nobody has quite gotten it right.

Jonathon is wrong on the meaning of E=mc2 – Reid is correct that the implication of the equation is that mass and energy are interchangeable and that mass equates to a lot of energy.

Noel is, sort of, correct to note that the concept that mass increases as speed increases (which is only noticable as v/c approaches 1) is an element of special relativity, but that element is not related to the e=mc2 equation.

So scoring Jonathon got no element correct, Reid was half right (apart from the appallingly incorrect reference to Newton) and Noel has made a fool of himself.

E=mc^2 is more fundamental than relativistic mass, it is, in fact, the expression of the shockingly bizarre idea that mass and energy are equivalent and closely related. At the time this was nothing less than revolutionary.

Also, I should point out that relativistic mass is somewhat of a tricky subject, and the term is not much used nowadays. Typically, real physicists tend to talk about either energy or momentum and reserve the term “mass” to refer only to “rest mass”. This is because energy and momentum are both reference frame dependent measurements, so they don’t want them to be confused with frame invariant values like rest mass.

Russell:

I heard a physicist say that it is possible that no one would have come up with E=mc^2 even after 100 years if it had not been for Einstein. It was that revolutionary of an idea.

What do you think?

G’day Jake,

I have heard the view expressed but I do not find it very convincing – a re-think of physics was required and Einstein was the first to get there. But there were elements of the new physics that never made sense to Einstein (trying looking up the Einstein-Podolsky-Rosen paradox and/or Bell’s inequality).

The world of ideas just doesn’t work like that. Exceedingly odd ideas occur to multiple people in different ways eg. Schrödinger and Dirac both separately came up with equations that express the same thing (though it only ever gets called Schrödinger’s equation). Part of the problem is that you need a very good understanding to see that the equations (that look nothing alike) mean the same thing – I suppose it is because Schrödinger had the cat.

Russel,

Contrary to what you said, my understanding is that the mass gain as v/c tends to 1 is directly related to e=mc^2. That part of the energy of acceleration which is not expressed as delta v is expressed as delta m, in the relationship of m = e/c^2.

“I suppose it is because Schrödinger had the cat.”

Are you certain?

From A. Einstein, “Does the Inertia of a Body Depend Upon Its Energy-Content?”, a lovely 3 page add on to the main paper on special relativity, as translated in __The Principle of Relativity__ (Dover):

“If a body gives off the energy L in the form of radiation, its mass diminishes by L/c^2…The mass of a body is a measure of its energy-content….If the theory corresponds to the facts, radiation conveys inertia between the emitting and absorbing bodies.”

So mass and energy are one and the same. To better understand this, we need the general theory of relativity. Maybe I’ll understand something of that by the time its centennial comes up in 2016.

As Russell says, rethinking was happening all over. It always is. The story of science is only a succession of pellucid individual triumphs in retrospect.

As far as relativistic kinematics are concerned, Poincaré and Minkowski were on much the same track as Einstein, and Minkowski subsequently made Special Relativity much easier to follow for those of us having difficulties.

It is the astonishing fertility of 1905 and the mind-boggling follow-up provided by General Relativity that gets Einstein top billing. Einstein is the most cited scientist counting papers published before 1930–but it is his Brownian Motion paper that wins, not E=mc^2. The Nobel Prize was nominally for the explaining the photoelectric effect by the quantization of light.

My own suspicion is that he might yet have been an important but little-known scientist–like Maxwell, say. He became a popular hero because of two political contingencies. The fervid rejection of relativity as “Jewish science” by the Nazis, made the transparently genial, unthreatening Einstein a representative emigré: a good man as contrast to unmistakeable evil. And E=mc^2 got a universal currency from awe of The Bomb.

“If a body gives off the energy L in the form of radiation, its mass diminishes by L/c^2…The mass of a body is a measure of its energy-content….If the theory corresponds to the facts, radiation conveys inertia between the emitting and absorbing bodies.”

If e truly does equal mc^2 then the above is simply an indesputable statement of fact.

Of course, if Einstein is wrong and e only aproximately equals mc^2 and we simply can’t yet measure the discrepancy yet, then the statement is a load of complete bollocks.

I had always wondered why scientists didn’t come up with E=mc^2 sooner, given the SI units for mass, energy, and velocity… Remarkably elegant equation.

One of those counter-intuitive things, I guess.

That’s a joke TWG? Just checking.

For those interested , I recommend this book:

http://www.fas.harvard.edu/~hsdept/faculty/galison/einsteins_clocks.html

Further to a prior thread on the pre-eminence of physics, there is a delightful if slightly condescending quote from Ernest Rutherford.

“In Science, there is Physics. Everything else is gardening”

I believe the correct quote is “All science is either physics or stamp collecting”.

To which one of my lecturers allegedly added “Much of physics is stamp collecting too”.

Guy-It’s not a joke. Many physical properties are indeed related to one another. Eg. charge, current, energy, and force, for example. It’s interesting how the units for certain properties offer tantalising hints of their origins and how they are related to other properties.

The unit for energy is the joule, but in base SI units it’s kg(m^2)(s^-2). On the other side of the equation, when you look at the product of the units for mass and the square of the speed of light, you get kg(m^2)(s^-2). When I showed it to students, they were all awed.

As if it’s that difficult to figure out!

But this would still be true in a universe where Einstein’s postulates were false, and E=mc^2 therefore meaningless.

The equivalence of the joule and kg m2/s2 follows from the definition of work, and is already apparent in the non-relativistic equation E = 1/2 mv^2.

You need Maxwell’s equations, or some other relativistic phenomenon, before the significance of the speed of light becomes apparent. Without that, then why pick the speed of light for E=mc^2, rather than some other speed?

What saddens me about Einstein was that despite his brilliance as a scientist and mathematician, he was a total boob politically. Essentially, he was a statist, almost a socialist.