Einstein’s theory of relativity a glimpse of future discoveries
The 100th anniversary of Albert Einstein’s general theory of relativity is marked by confirmation of a cornerstone prediction of quantum theory, a theory that Einstein described as a cosmic craps game and a prediction he dismissed as a hunt for “spooky action at a distance.”
On Nov. 25, 1915, Einstein wrote a mathematical equation that explained how gravity works. He showed that gravity is a manifestation of distortions in space-time caused by matter and energy. You can visualize what Einstein means if you can get some friends to help you stretch out a blanket while someone drops a bowling ball onto it. Imagine the ball is a planet or a star and the blanket is spacetime. That warp in the blanket caused by the bowling ball is gravity.
The implications of Einstein’s general theory are still reverberating. It explains Edwin Hubble’s discovery in 1929 that the universe is expanding. It explains why Mercury’s orbit changes minutely over time. It explains why light bends. Just this year, an international team of scientists published a paper saying they had observed what is known as an Einstein Cross, a phenomenon, predicted by the general theory, that allowed astronomers to see four different images of the same supernova 9.3 billion lightyears from Earth.
Arizona State University physicist Lawrence M. Krauss wrote for the Nautilus website that general relativity “was so mathematically beautiful that it seemed reasonable to assume that it codified perfectly and completely the behavior of space and time in the presence of mass and energy.”
Except that relativity does not codify behavior perfectly. It cannot explain the behavior of nature on a very small scale. To explain things like the decay of a radioactive atom, you need quantum theory.
“We know of no theory that both makes contact with the empirical world and is absolutely and always true,” Krauss said.
Use the mathematics of quantum theory to describe the behavior of planets and galaxies, and you arrive at a universe that folds over itself. Use relativity to explain subatomic behavior, and you end up with impossible mathematical values.
Einstein was actually a pioneer in quantum theory. His 1905 paper described how light, which had long been described as a continuous wave, could under certain circumstances behave like discontinuous, individual particles. These “light quanta” each carried a specific quantum of energy.
Experiments into quanta in the early 20th century began producing seemingly crazy results. Some experiments showed electrons and light behaving like waves, some like particles. Scientists discovered that the same particle would behave differently when observed at different times. In 1927, Werner Heisenberg showed that you could know with precision the location of a particle or the momentum of that particle, but you could not know both with precision.
Einstein’s good friend, the great Danish physicist Niels Bohr, said electrons have no “independent reality in the ordinary physical sense.” What became known as the Copenhagen Interpretation of quantum theory holds that a quantum particle exists in all possible states at once and that it is only when it is observed that the particle in effect chooses a state of being. For Bohr and Heisenberg, the universe isn’t the deterministic place that Einstein described. It is a place of probabilities and uncertainty.
Just as experiments have confirmed much of what the general theory predicts, experiments have confirmed much of quantum theory, most recently the theory’s prediction of spooky action at a distance.
Quantum theory predicts that particles separated by great distances can instantaneously affect one another’s behavior. Physicists say that particles are entangled. Delft University of Technology researchers reported this year that they were able to entangle particles separated by 1.3 kilometers.
Physicists have struggled for years to find some grand, unifying theory that will work on all forces, from gravity to electromagnetism, at all scales, from galactic to subatomic. Arizona State’s Krauss doesn’t expect that to happen anytime soon and rather hopes it doesn’t. He says he likes “the possibility that there will forever be mysteries to solve.”
What is beautiful about this general theory centennial year is the reminder of how much further there is to go.
The British mathematician Jacob Bronowski put it very well in his BBC program “The Ascent of Man.”
“Science is a very human form of knowledge,” Bronowski said. “We are always at the brink of the known. We always feel forward for what is to be hoped. Every judgment in science stands on the edge of error, and is personal. Science is a tribute to what we can know although we are fallible.”