Tuesday, August 9, 2011

Fun facts

Robert H. Goddard was an american physicist and scientist credited with inventing the world's first liquid-fueled rocket. In 1919 Goddard published an article about the possibility of building a rocket which could leave the atmosphere and even leave Earth's orbit altogether to reach the Moon. In response to this, the well-known editorial New York Times published an article criticizing Goddard's work and claiming that he failed to understand Newton's law of action and reaction and that thrust could not be achieved in vacuum, thus making rockets useless in space. 49 years later, on the day Apollo 11 (the mission which led to the first moon-landing) was launched, they printed a retraction saying: 'Further investigation and experimentation have confirmed the findings of Isaac Newton in the 17th Century and it is now definitely established that a rocket can function in a vacuum as well as in an atmosphere. The Times regrets the error'.

Austrian mathematician Kurt Gödel was a good friend of Albert Einstein. After Einstein had published his general theory of relativity, Gödel had found a solution to Einstein's field equations which allowed time travel into the past. He gave this solution to Einstein, as a gift for his birthday, a way of saying don't feel bad about getting old, you may still be able to see your younger self. 

During the Manhattan Project (the creation of the first atomic bomb) physicist Edward Teller, known as the father of the hydrogen bomb, raised the concern that the detonation of the atomic bomb may start a fusion chain reaction of the nitrogen in the Earth's atmosphere thus incinerating it and destroying all life on the planet. You may have noticed that that hasn't happened. It was proven to be impossible.

During a lecture, physicist Richard Feynman said that he would like to memorize the digits of π up to the 762nd decimal place where a sequence of six consecutive nines appear. He wanted to recite the decimals up until that point and then say 'nine nine nine nine nine nine and so on' suggesting jokingly that π is rational. For this reason, that sequence of nines is called the Feynman point.

Photons (quanta of light) from the Sun's surface take about eight minutes to reach the Earth. Photons produced inside the Sun can take between 10 000 and 170 000 years to reach the surface because of the plasma constantly absorbing and re-emitting photons in random directions (on a side note, writing was invented 5000 years ago and modern humans appeared some 50 000 years ago). The Sun has a radius of about 700 000 km, and the distance from the Sun to the Earth is around 150 000 000 km.

Magnetars are very dense neutron stars with extremely powerful magnetic fields. These magnetic fields are quadrillions (10^15) of times more powerful than Earth's magnetic field, in fact the field is so powerful that even at a distance of 1000 km a human being's tissue would be destroyed because of the response of water molecules (which are diamagnetic) inside the body to the intense magnetic field. If a magnetar were 150 000 km from the Earth it would erase the information stored on all credit cards.

Earth is not the only planet in the solar system to emit radio waves. Gas giants produce radio waves all the time as a result of fluctuations in the magnetosphere and aurora borealis similar to those seen on Earth. Here is a sample of radio waves from the planet Saturn as recorded by the Cassini spacecrafthttp://www.nasa.gov/wav/123163main_cas-skr1-112203.wav

The electron has a negative electrical charge doubted the elementary charge e, which is about 1.602 * 10^(-19) C (Coulombs). To understand how small this number is, consider that a capacitor which charges a camera flash powered at up to 330V and with a capacitance of 80 uF (microFarads) stores about 0.02 Coulombs of charge or about 12.5 * 10^16 electrons. We can thus see that it could be quite problematic to measure the elementary charge experimentally. Physicist Robert Millikan was the first to measure this constant using an experiment now known as Millikan's oil drop experiment in which he suspended a charged drop of oil in an electric field and made it levitate. Levitation is achieved due to the fact that the electrical force balances the oil drop's weight. After many measurements he was able to deduce the constant. A more interesting way in which the constant can be measured is by listening to the electrical noise made by electric current travelling through a cable. What is of interest here is shot noise. Electric current is the disorganized flow of charge carriers in a certain direction. If we take electrons for example, when travelling through a conductor many will tend to bump into each other so that the number of electrons which passes through a certain section of the conductor varies in time, this is shot noise. This variation can be detected as electrical noise, and when the number of electrons is such that the variations are on the order of tens or hundreds of electrons (small currents and small time scales) and knowing that these variations respect a Poisson probability distribution it is possible to measure the elementary charge. 

The Sun has an 'atmosphere' made out of plasma called the corona. The corona extends millions of kilometers into space and can be seen clearly during solar eclipses (see image below). The visible surface of the Sun is called the photosphere. One would expect that the photosphere is much hotter than the corona, but the temperature of the photosphere is around 6000 K (degrees Kelvin) while the temperature of the corona is about 2 000 000 K. This is called the coronal heating problem, and is currently an unsolved problem in physics. An analogy to this would be the air around a light bulb being hotter than the surface of the bulb itself. 

The Antikythera mechanism is an ancient mechanical computer, believed to have been used to calculate astronomical positions. What's interesting about it is that it consists of a system of gears similar to those found in 19th century Swiss clocks, yet the device dates back to somewhere between 150 and 100 BC. It was found on a shipwreck near the Greek island of Crete. It is the oldest known analog computer, and similar devices would not appear in Europe until the 14th century.

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