There was a young lady named Bright,
Whose speed was much faster than light;
She set out one day in a relative way,
And returned home the previous night!
Limerick, author unknown, in honour of relativity
Back in the early 1950s, together with the author’s parents, the writer once went to Princeton, New Jersey for the day to have supper with a relative who was living in Princeton at the time. She was an artist, a lesser-known devotee of the school of abstract expressionists then thriving in nearby New York City. (In actual fact, while she made her living typing scientific and other academic manuscripts for the authors too busy – or unfamiliar with a keyboard – to produce clean copy for submission to academic journals, she lived the artistic life in that university town).
A necessary part of any trip to Princeton back in those days, of course, was to drive slowly past 112 Mercer Street, Albert Einstein’s modest home where he lived from the time he arrived in the United States to join Princeton’s Institute for Advanced Study (just ahead of the Nazi Holocaust) until his death in 1955. The hope of any such a drive-by was to catch at least a glimpse of the man who had changed the world – whatever it was that he had really discovered. That bit was a little unclear to most people, but the fact he was the 'father' of the atomic bomb, well everyone knew that. On that particular day we did not actually see him, but we did see the house of the man who had changed everything under, around, and inside the Sun. Especially, inside the Sun.
Photo: Albert Einstein's house in 112 Mercer Street (Wikimedia Commons)
By 25 November 1915, Einstein had already become a famous theoretical physicist from his work on the photoelectric effect and what he had called special relativity. He would finally gain a Nobel Prize in 1921 for this earlier work on the Law for Photoelectric Effect, since his work on relativity remained, years later, still too controversial for too many in physics to be blessed with a Nobel award. In the years following this research and his increasing fame from four famous papers published in 1905, he moved from an obscure position as a patent examiner for the Swiss patent office, and on to a much more visible and honoured position in the Kaiser Wilhelm Institute in Berlin, with the illustrious Max Planck as mentor. It was from that perch that he launched his most extraordinary scientific thunderbolt.
While working at the patent office, Einstein had the time and solitude to advance ideas that had first taken hold during his studies at Polytechnic, and then brought together his thoughts on what would become known as the principle of relativity. In that year of 1905 — seen by many as a “miracle year” for the theorist - he published four separate papers in the Annalen der Physik, one of the best-known, most prestigious physics journals of that period. These four papers focused, respectively, on the photoelectric effect, Brownian motion, the special theory of relativity (the most widely circulated of the write-ups), and the matter/energy relationship. The final one took physics in an extraordinary, even revolutionary, new direction. In that fourth paper, Einstein used his famous equation E = mc2, suggesting the astounding idea that tiny particles of matter could be converted into huge amounts of energy, thereby foreshadowing the development of atomic power, and overthrowing a fundamental distinction between matter and energy. (According to some science historians, French physicist Henri Poincaré came up with his E/c2=m equation some three months before Einstein - Ed)
Then, if all this were not sufficient to carve out a place in physics’ pantheon, in 1915 Einstein came along with his work on general relativity as well. Of this, David Kaiser, professor of the history of science, technology and society at the Massachusetts Institute of Technology (MIT), said, “Einstein changed the way we think about the most basic things, which are space and time. And that opened our eyes to the universe, and how the most interesting things in it work, like black holes.” And this new understanding firmly launched the 20th century’s understanding of the space-time continuum – even as it added even more problems for reconciling the then newly evolving world of quantum physics with Einstein’s relativistic one.
In describing the impact of Einstein’s work, The Economist has written, “General relativity was presented to the Prussian Academy of Sciences over the course of four lectures in November 1915; it was published on December 2nd that year. The theory explained, to begin with, remarkably little, and unlike quantum theory, the only comparable revolution in 20th-century physics, it offered no insights into the issues that physicists of the time cared about most. Yet, it was quickly and widely accepted, not least thanks to the sheer beauty of its mathematical expression; a hundred years on, no discussion of the role of aesthetics in scientific theory seems complete without its inclusion.
“Today its appeal goes beyond its elegance. It provides a theoretical underpinning to the wonders of modern cosmology, from black holes to the Big Bang itself. Its equations have recently turned out to be useful in describing the physics of earthly stuff too. And it may still have secrets to give up: enormous experiments are under way to see how the theory holds in the most extreme physical environments that the universe has to offer.
“The theory built on the insights of Einstein’s first theory of relativity, the ‘special theory’, one of a trio of breakthroughs that made his reputation in 1905. That theory dramatically abandoned the time-honoured description of the world in terms of absolute space and time in favour of a four dimensional space-time (three spatial dimensions, one temporal one). In this new space-time observers moving at different speeds got different answers when measuring lengths and durations; for example, a clock moving quickly with respect to a stationary observer would tell the time more slowly than one sitting still. The only thing that remained fixed was the speed of light, c, which all observers had to agree on (and which also got a starring role in the signature equation with which the theory related matter to energy, E=mc2).”
Following his initial presentation of his paper in Berlin, this work then appeared in the March 1916 issue of Annalen der Physik. It was a major departure from the precise, mechanistic, clockwork universe of Isaac Newton’s, the one that had held sway for nearly 250 years and that had let to so many discoveries in astronomy. In general relativity, Einstein had argued that “space and time are not fixed, which was what others had thought, but are flexible, dynamic phenomena like other processes of the universe. So space bends and time warps, and it was a whole new way at looking at gravity,” explained Michael Turner, director of the Kavli Institute for Cosmological Physics.
This new exploration of Einstein’s ideas of general relativity had built upon the physicist’s earlier theory of special relativity in which he had left out gravity as a consideration, but where he had first advanced a consideration of the complex relationship between space and time. Now, in his theory of general relativity, with the addition of gravity as a key factor, Einstein explained that time would move more slowly in proximity to a powerful gravitational field, such as that of a planet in the void of space. This idea was eventually confirmed by comparisons of paired atomic clocks, in which one remained on Earth and the other was carried aloft in a high-altitude airplane where it showed a slight but distinct delay. In a thoroughly practical application of general relativity’s principles, today’s global positioning systems make use of this phenomenon, where satellites have clocks precisely adjusted to account for these small, but vital time differences. General relativity has also made the full panoply of modern science fiction possible as well, what with all those intricate ways around the ultimate limit by virtue of the speed of light, and the presumably inherent contradictions of time travel (and all those ingenious ways around them that have been the basis for so many great films and stories).
Another key element of general relativity was the point that light is also warped by powerful gravitational fields, something that British astronomer Arthur Eddington managed to confirm in 1919, with his observations of the slight, but real deflections of starlight by the Sun through his meticulous measurements from his temporary observing post on the island of Príncipe (of São Tomé and Príncipe). Eddington went there to observe the 29 May 1919 solar eclipse – and this became a crucial proof of general relativity’s predictions.
Watch: Einstein and Eddington, HBO trailer
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Einstein’s general relativity led to the realisation that at the end of their lives, stars would collapse under their own gravity. Their external gaseous envelope would explode as a supernova, while their core would form a very dense object such as a neutron star, or a rapidly spinning pulsar. They could also transform into a black hole, which had such a huge gravitational field that space and time themselves could not escape. Per Einstein’s calculations, such celestial bodies, given their masses, would provoke waves in space-time much like a tossed stone caused ripples in water.
MIT’s Kaiser explains that gravitational waves are what astronomers are now hoping, finally, to observe and measure first-hand. Such observations, Kaiser says, would “confirm one of the last great, but as yet untested predictions from Einstein, equation that space and time are not really dynamical, but they can ripple, like the surface of a pond.” The Laser Interferometer Gravitational-Wave Observatory (LIGO) in the United States and VIRGO, a gravitational wave detector in Italy, are now poised to do this precise heavy lifting.
What Einstein’s general theory of relativity also did, however, was set up a vast challenge for physics – the need to reconcile, somehow, relativity with quantum physics. The latter, in contrast to Einstein’s approach effectively describes phenomena on the atomic and sub-atomic levels and has, as a consequence, led to applications crucial to the contemporary world such as transistors and computers.
As things stand now, one approach for this bringing of things together has been something really abstruse and hard to visualise, called string theory. This approach asserts that fundamental particles are not so fundamental, and aren’t even particles, but rather a kind of elastic “string” that vibrate at different frequencies and different dimensions to generate their physical presence. String theory, in turn, leads to the possibilities of numerous other extra dimensions beyond the usual three plus time.
A further implication is that the describable dimensions of time and space could also be different than even what relativity offers. Einstein, of course, had recognised this problem early on, and he had laboured for years – especially during his years in Princeton – on what he called his general field theory, arguing the case via his famous aphorism about god not playing with the universe as if he had celestial dice. This preoccupation of Einstein’s, to find a way out of the contradictions flowing from the clash of relativity and quantum physics, meant that for many physicists, Einstein was viewed as increasingly out of the mainstream of physics thinking and research.
Watch: Albert Einstein documentary