Canada and the World
Current Events with a Canadian Perspective
Last update
30 December 2010
Science Timeline Part Ten
Albert Einstein proposes the theory of relativity, an idea that promises to unlock a host of mysteries
By early 20th century, physicists were peering into the structure of atoms and finding things that the laws of classical physics couldn’t explain; new laws were needed.
Development of Quantum Theory
One of these new laws was quantum theory. This is a description of the particles that make up matter and how they interact with each other and with energy. Quantum theory explains in principle how to calculate what will happen in any experiment involving physical or biological systems, and how to understand how our world works.
The German physicist Max Planck explained quantum theory in 1890. He said energy was given off by matter not in a continuous stream but in discrete pieces. He called these individual bits of energy quanta (the singular of quantum, a Latin word meaning “how much?”).
The Quantum theory marks a watershed – the dividing line between classical physics and modern physics.
Classical physics accurately describes the behaviour of matter and energy in the everyday Universe. For example, classical physics explains the motion of a car accelerating, or of a ball flying through the air.
Quantum theory, on the other hand, can accurately describe the behaviour of the Universe on a much smaller scale, that of atoms and smaller particles. The rules of classical physics do not explain the behaviour of matter and energy on this small scale.
Quantum theory is more general than classical physics, and in principle, it could be used to predict the behaviour of any physical, chemical, or biological system. However, explaining the behaviour of the everyday world with quantum theory is too complicated to be practical.
Quantum description of particles allowed scientists to understand how particles combine to form atoms. Quantum description of atoms helped scientists understand the chemical and physical properties of molecules, atoms, and subatomic particles.
Quantum theory enabled scientists to understand the conditions of the early Universe, how the Sun shines, and how atoms and molecules determine the characteristics of the material that they make up.
Without quantum theory, scientists could not have developed nuclear energy or the electric circuits that provide the basis for computers. And, quantum theory had to come before the world’s most famous equation – E = mc2.
Einstein’s Theory of Relativity
In 1905, the German-
published his special theory
of relativity. Einstein’s general theory of relativity followed in 1915. These theories
are the basis for our ideas about the Universe.
Einstein worked out these theories from two ideas. One was that the speed of light does not change when either the light source or the observer moves.
The second was that motion is not absolute. We cannot say, for example, that some objects are “really” at rest and other objects are “really” moving.
We can say only that things move relative to each other. If you are standing still, and a bird is flying past, it cannot be said you are standing still. You are actually moving relative to the bird. It can only be said that you are “standing still” relative to the ground.
Einstein’s special theory of relativity explained the changes that are noticeable when objects, such as tiny particles, travel at or near the speed of light, the fastest speed possible. The theory shows that mass (m) and energy (E) are linked by the equation E = mc2, where c is the speed of light.
This means that a small amount of mass can be changed into a huge amount of energy, which is what happens in nuclear reactions.
Albert Einstein’s equation proved to be the solution to many, many puzzles, and the foundation of many, many theories.
Einstein’s Theories in Outer Space
In 1916, the German astronomer Karl Schwarzschild put forward the idea that there were gravitational phenomena in the neighbourhood of stars where mass is concentrated into an infinite point. (Half a century later, this phenomenon was given the name “Black Hole.”)
A year later, the Dutch astronomer Willem de Sitter used Einstein’s equation to propose that the Universe was expanding. In 1929, the American astronomer Edwin Hubble discovered that the farther a galaxy is from Earth, the faster it is receding. He confirmed that the Universe is expanding.
Using E = mc2 in another way in 1919, Ernest Rutherford converted one type of atom into another type of atom by bombarding the first with subatomic particles. In other words, he had brought about the first human engineered nuclear reaction.
More to come
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This giant sculpture was erected in Brussels, Belgium in 1958 for a World’s Fair. Called the Atomium it is 102 metres high and represents an elemental iron crystal enlarged 165 billion times.
Image Credit
Chrystian Cruz
1906
German chemist Walther Nernst proposes the third law of thermodynamics, which states
that absolute zero temperature cannot be reached. The laws of thermodynamics are
supreme physical laws -
1907
The American chemist Bertram Boltwood discovers a way of calculating the age of a rock by measuring the rate of its radioactive decay. He dates the Earth at 2.2 billion years, about half the age now calculated. However, Boltwood’s calculations challenge the widely accepted belief that the Earth was created in 4004 BCE as the Irish priest James Ussher proposed from Bible study in 1640. There are still many fundamentalist Christians who say Ussher is right and science is wrong.
1909
German chemist Fritz Haber develops a process to synthesize ammonia that makes the production of artificial fertilizer possible, increasing crop yields that now sustains one third of the world’s population. Unfortunately, Haber also used his scientific skills to develop chlorine and other poisonous gases that were used during World War I.
1909
Charles Doolittle Walcott discovers one of the important caches of fossils in
the world in the Canadian Rockies. The Burgess Shale provides a glimpse of what life
was like half a million years ago and offers evidence of evolution.
1911
Noticing that the coastlines of South America and Africa “fit” together like
pieces of a jigsaw puzzle, the German scientist Alfred Wegener proposes that all
continents were once part of a single landmass. His theory of continental drift says
that over time parts of this landmass moved away from each other. His theory is at
first ridiculed but eventually accepted as more fossil evidence proves him right.
1911
Making the first of ten ascents in a hot-
1913
Danish physicist Niels Bohr describes atomic structure in which electrons move in orbit around a nucleus.
1918
Rarely have women appeared in these pages (see opposite) and Emmy Noether is a perfect
example of why. Born in Germany in 1882, she is forced into an arts education (considered
the only suitable area of study for females), although she is clearly a mathematical
genius. Women are not allowed to enrol in university so she begins sitting in on
classes in 1903 and eventually the administration relents and she becomes a full-
1923
The wave or particle debate continues, only now it gets confusing. French physicist Louis Victor de Broglie suggests that just as waves can sometimes behave as particles, so can particles, such as electrons, behave as waves. For this discovery about the nature of electrons, de Broglie is awarded the Nobel Prize in Physics in 1929.
An artist’s conception of a growing black hole, called a quasar. Swarms of these have been found in distant galaxies. They cannot be seen because not even light can escape the gravitational pull of a black hole.
NASA image
WHERE
ARE THE WOMEN?
You will have noticed that scarcely any females have appeared in this narrative to this point. Why? The answer is prejudice (not this editor’s but society of the time).
We need look no further than the work of the French anthropologist Pierre-
Around 1860, he found that, on average, the brain of a female is about 200 grams lighter than that of a male. One of Broca’s students, Gustave Le Bon, then said that as womens’ brains were about the same size as those of gorilla’s…well, you can see where he was going with this.
It was scientific claptrap but it did capture some of the commonly held views of the intelligence of women at the time.
Women, of course, have smaller brains than men because they are, on average of smaller build than men. And, science has now shown that brain size has nothing to do with intelligence. But, try to imagine the obstacles a woman would face if she wanted to enter science.