The accidental scientist

    Discovered in 1862, 109P/Swift-Tuttle is a big comet with a 26 km diameter, a period of 133 years, last seen around 1992. When a comet gets reasonably close the the Sun (like within Mars or the Earth orbit), the solar wind rips out of it all sorts of debris, mainly ice crystals and dust. This is what the comet’s tail, aka its coma, is made of. If and when the Earth gets close to where the comet’s tail has been, some of these bits and pieces get into the upper atmosphere at high speed, get vaporised and voilà, you get a meteor shower. There is one going on right now, courtesy of Swift-Tuttle. If you are a reasonably motivated early bird, you can have a look at it. It is called the Perseids meteor shower. In theory it peaks between August 9 and 13 but in my humble opinion it will be pretty low on the horizon by then. So you may as well have a go, say, from Saturday 31 and the following few days, between 4 and 5:30 am. Pick a spot away from city lights and wit...

      Last week I had a conversation with Mike about the magnetic poles. I explained to him that the poles tend to go walkabout. The North magnetic pole moves from North Canada towards Siberia at about 55 – 60 kilometres per year. Then Mike asked: is there a link between the North and South magnetic poles positions? No but yes. On the “no” side it can be said that over a period of time one pole can be relatively quiet while the other one runs. On the “yes” side the poles are a manifestation of the Earth Magnetic Field, so the cause of their existence and movements is the same. Many years ago scientists – including Einstein – thought that the totality of the Earth formed a permanent magnet. But since then it was observed that the Earth magnetic field force varied and that its polarity has changed many times in the distant path. A permanent magnet can lose strength over time, but it can’t change polarity. You need something like an electromagnet. And sure enou...

   In 2000 I spent a year on Macquarie Island doing science stuff. One of the projects we ran was the collection of plastic bits on Sandell Bay, a 2km beach located on the Island West coast. This was done every month. Not really to clean the beach, but to analyse the stuff, figure out where it came from and get a better understanding of the Southern Ocean sea currents. Anyway, collecting about 3 full garbage bags of plastic bits every month on such a remote location is a bit scary, isn’t it? Scary but not so surprising considering that nowadays at least 8 million tons of the stuff end up in the oceans every year. That’s about a garbage truck per minute. A good proportion of this is wrapping sheets. I mean the stuff around hay bales, for example, and just about anything produced by humans. Food wrap is part of that. It is very bad for sea creatures and for us as well: two major reports last year linked 175 compounds to health problems connected to cancers, fertility and fetal...

  Today, let’s calculate the surface temperature of a star. Physicists like to use the Kelvin temperature because it is convenient. Just imagine a black rock in the middle of nowhere in the universe. It’s very cold because nothing warms it up. So we say it’s at 0 degrees Kelvin. 0°K! In the more familiar Celsius scale, it would be -273°C. That black rock at 0°K does not emit any radiation. But if we warm it up, it will start to emit some weak infrared light. If we heat it hard, it will glow red, then yellow, then white… Now let’s look at the light. It is an electromagnetic wave, and its wavelength defines its colour. The wavelength is expressed in nanometers. FYI 1 nm is 1/1000th of a micron. Visible light ranges from 400nm (deep red) to 700nm (violet). Physicists found out that the light spectrum emitted by a black body has always the same shape. As the black body gets hotter, the peak of the spectrum curve shifts towards the short wavelengths. At 4,000°K, it...

  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. ...

  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 c...

        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 compris...