The accidental scientist

  We all know that to see a good rainbow we need rain in front of us and sunshine in the back. Then this beautiful arch manifests itself, violet on the inside to red on the outside. Is it really a circle? No, it is a 3 dimension object, a cone in fact. It all happens where the rain is. Millions of water drops in the air, each one acting as a tiny spectroscope: the white sunlight beam enters the drop on one side and gets refracted. What does that mean? It gets deflected by an angle that depends on the colour: violet is the most deflected, green is average and red is the least deflected. Then the light gets reflected on the back of the drop and comes back to the front where it gets refracted again. In total, the outgoing bean forms an average angle of 42 degrees with the incoming beam.   So you see the rainbow as a circular arc, but in fact it is a cone. The axis of the cone is the straight line defined by the Sun and your eye, which is where the cone apex is. And the half-a

  Scorpius (the Scorpion) is the mos elegant constellation in the sky. At the moment we are in a very good position to look at it because it raises just after sunset and if you look at the Eastern sky then, you just can’t miss it. The tail on the right hand side forms a beautiful curve in then Milky Way and the triangle on the left represents the head and the claws. Just on the right of that triangle is the eye of the scorpion, the brightest star in it: Antares. Its distinctly red-orange colour is easily visible by naked eye. Antares is a red giant. In the past we talked about Betelgeuse in Orion. There is another one called Aldebaran in Taurus. But Antares is bigger. To give you an idea of its size, just visualise the orbit of Mars around the Sun. Our Earth is at 150 millions kilometres from the Sun, Mars orbits the Sun at about 1.5 times that distance, or 225 millions kilometres. Antares’s radius is 473 million km, more than twice the orbital radius of Mars. In compa

        Last Sunday I had a fabulous lunch at Little Cambridge with a few friends and an interesting conversation. Ron told me that he got up one day at some ungodly hour to watch an asteroid. This surprised me a bit. I asked if it was not a meteorite by any chance? No he said, definitely an asteroid. There are millions of asteroids, literally. Their size ranges from a grain of dust to the 940km diameter of Ceres, the biggest. The vast majority of them belong to the main asteroid belt which is located somewhere between the orbits of Mars and Jupiter. All this is fairly stable, so a collision with the Earth is impossible right? Not really. There are quite a few rogue asteroids all over the place. It is believed that Jupiter gravity ripped them out of the main belt. Most of the NEA’s (Near Earth Asteroids) belong to four groups called the Amors, the Apollos, the Atens and the Atiras.    Near Earth Asteroids   The Apollos group alone comprises some 1600 known objects and the

  Carbon is a fairly social atom. It forms 4 links with other atoms to make up molecules. By comparison, oxygen looks a bit shy with only 2 links. And hydrogen is like introvert bordering on antisocial. Only one link! These three atoms form some of the most useful and common molecules. Water is H 2 O. We can show the 2 links between atoms by writing it like this: H-O-H. Similarly, carbon dioxide or CO 2 is in fact O=C=O. Carbon has 4 links, the oxygens have 2 links each, no worries. Carbon and hydrogen compounds are called alkanes. The simplest is natural gas or methane, CH 4 . Propane has a a chain of 3 carbon atoms. It is C 3 H 8 . Petrol is mostly octane with a chain of 8 carbon atoms, C 8 H 18 . Generally speaking, for a chain of n carbon atoms C, we need twice that number of H, plus one at each end. That is 2 x n + 2. Simple enough? Enter the benzene.  Back in 1865, August Kekule scratched his head on this one. With 6 carbon atoms, it should be C 6 H 14 right? Wrong. T

      Didn’we have a beautiful Red Moon last Wednesday! I got a bit crazy about it and forgot about everything else. Then I thought that such a perfect Sun-Earth-Moon alignment must have made one hell of a tide. The main causes of tides are lunar attraction (by far the biggest one) and solar attraction. The Moon pulls up the oceans so it creates a kind of bulge in its direction. This bulge occurs once every lunar day (24 hours and 50 minutes). On the opposite side of the Moon there is another bulge called the antipodal bulge. This happens because the Moon attracts the Earth solid mass more than it does the ocean. This explains why in most places you get every lunar day a sublunar high tide, then another high tide half a lunar day (12 hours 25 minutes) later. So far so good. Things are not that simple because the Sun does about the same thing but on a smaller scale and on a 24 hours cycle. So we get bigger tides when the Sun and the Moon are aligned (full moon and new m