Sunday, September 26, 2010

Relativity's First Test

In General Relativity, Einstein describes gravity as
a deformation of space-time around a massive object.

Einstein was the master of the thought experiment, but when it came to real experimentation, not so much. He preferred to make predictions and let the rest of the scientific community scramble to prove or disprove it. Most of the time he was right. But even Einstein was able to admit that “No amount of experimentation can ever prove me right; a single experiment can prove me wrong.” This is an essential characteristic of a scientific theory or hypothesis and is known as falsifiability. Falsifieability is a good thing because it means that a hypothesis is testable and thus conforms to the standards of the scientific method.
   One such case where Einstein’s ideas were put to the test was his General Theory of Relativity, which predicted that in the presence of a gravitational body such as the sun, spacetime would be warped and that light would follow a curved path as a result. Einstein said that light travels along the curve of space-time taking the shortest path between two points, so therefore light is deflected toward a massive object. The stronger the gravitational pull, the more the light path is bent. This idea was received with much scepticism at the time and was in contradiction with Newton’s theories, so scientists were eager to test it.
One of Eddington's photographs of the total solar eclipse of
May 29, 1919, confirming Einstein's theory that light "bends".
  For the British astrophysicist Sir Arthur Eddington, that opportunity came during a total solar eclipse on May 29, 1919. Eddington set out to measure the positions of stars near the sun before and after this eclipse to see if starlight was actually being deflected. Eddington had measured the true position of the stars months before and was able to calculate, according to Einstein’s theory, that there should be an ever-so-slight bending of starlight—now known as gravitational lensing. 
  Eddington’s experiment ended up confirming Einstein’s theory, and by November the London Times ran the headline “Revolution in Science: New Theory of the Universe: Newton’s Ideas Overthrown”.
  Einstein was an international celebrity overnight. When asked what he would have done had the eclipse experiment not agreed with relativity, Einstein replied “Then I would feel sorry for the good Lord. The theory is correct!”.

Monday, September 20, 2010

Exceptions to the rule

One of the founding principles of science is that the exception tests the rule. So if there is an exception to any rule, and if it can be proven by observation, that rule must be wrong. 
  For example, Aristotle believed that heavier objects fell faster than light object, and this was the conventional wisdom for many centuries. Then Galileo decided to test it in his famous Leaning Tower of Pisa experiments. It’s not known if he actually dropped cannonballs of different weights from the tower, but he did discover that regardless of the weight of the objects, they fell at the same rate. 
  So, based on the experimental evidence, Aristotle was wrong—regardless of how great a philosopher he was.
  Another example: Isaac Newton was convinced that space was filled with a “luminiferous ether” in which light traveled through. This was disproved by Michelson and Morley in 1887. They were trying to measure an ether wind by comparing the speed of light in perpendicular directions. The theory was that the earth’s movement through space creates an ether wind that would effect the speed of light in the same way that a jet travels faster in a tailwind and slower in a headwind. What they discovered was that light moved at the same speed regardless of direction, and, therefore, Newton had to be wrong. It would not be until 1905 that we would get a new theory explaining light and how it travels by a 26 year old Swiss patent clerk.

1) True or false: Galileo proved that heavier object fell faster than light objects.

2) A luminiferous ether was hypothesized to be __________.
a) a light-emitting organic compound  b) the medium through which light travels  c) the vacuum of space  d) an optical illusion

3) True of false: Michelson and Morley devised an experiment to measure the speed of light.

4) Which of the following is not true:
a) light travels fastest when moving through a vacuum  b) light displays wave-like properties  c) light is composed of particles d) light moves at the same speed everywhere.

5) A new theory of light was developed in 1905 by ________.

Sunday, September 12, 2010

Pluto—It’s a Dog’s World

A comparison of sizes of Pluto and Earth.

How did Pluto lose its planetary status? Discovered by Clyde Tombaugh in 1930 while working for the Lowell Observatory in Arizona, Pluto captured the imagination of the country. Pluto was named by Venetia Burney, an eleven year old girl from Oxford, England. She thought naming the new planet after the Roman god of the underworld was appropriate, considering the new world would be so cold and dark. The Lowell Observatory agreed unanimously. Pluto-mania followed: Disney would name its new side-kick for Mickey Mouse after Pluto. In 1941, Glenn Seaborg named the newly-formed element Plutonium after Pluto as well.
   Pluto’s status as a planet was questioned by astronomers over the years due to its small size, but the final blow was administered by Caltech’s Mike Brown. In 2005, Brown discovered a body in the Kuiper Belt—a region on the outskirts of our solar system littered with icy objects—that was larger than Pluto. Brown named the body Eris and initially considered it to be the 10th planet. But because it was so far from the sun—roughly three times farther than Pluto—members of the International Astronomical Union (IAU) began to worry. What if more planets were out there waiting to be discovered? Where would it end? This prompted them to do something that hadn’t been done since the time of the ancient Greeks—to actually define what it means to be a planet. 
   The pivotal criterion in the IAU definition was that a planet must clear the neighborhood around its orbit of matter, which Pluto does not do. So, after 76 years, Pluto was given the boot along with Eris and any other yet-undiscovered body. They were reclassified as “dwarf planets” instead. At least now the school-kids mnemonic for remembering the order of the planets, “Martha Visits Every Monday and Just Stays Until Noon, Period.” can lose the Period.

Pluto Trivia

  • Pluto is smaller than our Moon.
  • Pluto’s moon, Charon, is more than half the size of Pluto.
  • Because Pluto is so far away, the Sun would look like a bright star from Pluto’s surface.
  • Pluto’s has an irregular orbit, and starting in the year 2227, Pluto will be closer to the Sun than Neptune.

Sunday, September 5, 2010


Physicists at Fermilab in Batavia, Illinois are in a race against time. Their Tevatron accelerator has been top dog for nearly 20 years, being used to discover the bottom quark in 1977 and the top quark in 1995. Now, nearing retirement, Fermilab is trying to find the holy grail of particle physics—the theorized Higgs boson. 
But there’s a new player on the field, and it’s a giant—CERN’s Large Hadron Collider. Once fully operational it will be seven times more powerful than the Tevatron. Even running at half strength it has already set the record for the most-energetic particle collision ever created by man. If the Higgs particle exists, this machine will find it. 
Will Fermilab be able to pull off one more great discovery before they retire the Tevatron, or will the Higgs be found by CERN? Place your bets.

1) The Higgs boson is also known as ____________________.
a) a charm quark  b) dark matter  c) a neutrino  d) the God particle

2) True or false: there are four known fundamental forces in the universe—electromagnetic, strong, weak and gravitation.

3) A hydrogen atom that has lost its electron is also known as ____________________________.
a) a proton  b) a neutron  c) a photon  d) a quark

4) True or false: In physics, TOE stands for theory of everything.

5) The idea that elementary particles are made of one-dimensional vibrating lines is called ____________________________.