Hawk-Eye

After watching some Wimbledon and what with the controversy of the World Cup, I asked myself how Hawk Eye actually works. This is the system that tracks the ball as it moves around the court (or football pitch) and determines whether a ball is in or out, and where it might've gone if not it wasn't caught or hit (especially important in leg-before-wicket decisions in cricket. Hawk-Eye was invented by Paul Hawkins and David Sherry at Roke Manor Research in the UK, with the initial main aim of being used in cricket.

Hawk-Eye requires a minimum of 4 cameras around the playing field (cricket uses 6, see illustration below). The cameras are normal video cameras and thus take a series of shots of what they see, called frames. Each frame is sent to a data processing unit (a computer) where the computer has to firstly identify the ball and calculate its position in the frame. Once the computer has done this for all 4 cameras, it calculates a 3D position of the ball in space using all the data gathered from all the cameras. After this, the computer can draw the path that the ball has taken, as well as predict a path that the ball might take, based on the change of position of the ball in successive frames. The computer can then map this path and compare it to the rules of the game to determine whether a ball was in or out, or a player was LBW. The computer can also work as a statistics generator, recording and storing information about ball track, size, and velocity. This is particularly useful if cricket commentators want to discuss ball delivery.


------------------------------------------------------------------------

Yesterday I spent some time at the Royal Society's Summer Exhibition and learned a lot about shape-shifting materials, viruses, how the brain works, and land mine detection technology - things I'll definitely be writing about soon!

How to visit the Old Bailey

As a bonus to my first post, here's a very simple little "how it works", and it's practical in nature.

How to view court cases at the Central Criminal Court in London, England

The Central criminal Court in London is known as the Old Bailey - named after the street it's situated in. It's just around the corner from St. Paul's cathedral, and it seems that very few people know they can just walk in and observe cases free of charge.

The Old Bailey is open from 9:45 each day to the public. You're not allowed to take in mobile phones,cameras, bags or food. If you want to make it easy on yourself, drop your bag off at the Old Bailey Cafe diagonally opposite the Old Bailey for £1. Go into the building via the Public Entrance (to the right of the building if you're standing in front of it; it looks like a tunnel). Go early - there are often school groups taking up all the seats. Don't just barge in, but ask the guards at the doors just off the stairwell if there's a case that you can watch. If possible, find someone who goes a lot and latch onto them - the guards are a lot friendlier with regulars.

A large part of the fun is patching together the story as the arguments unfold. If you're lucky, you'll also witness an ace solicitor cross-examining a witness and playing to the gallery. And you get used to those silly silly wigs pretty quickly, believe me.

Inaugural post - paternity testing.

Welcome to my blog, in which I'll attempt to explain how things work! As someone with a fairly broad field of interest, I intend to cover a large amount of subjects - from genetics and cycling, to ocean waves and selling cars. However, as a trained scientist I predict that I'll post a bit more about science-related stuff. My goal is to try and make complicated things a lot easier to understand.

So, without further ado:

Paternity testing

Every person has DNA in the cells of his or her body. Half of your DNA comes from your father, and the other half comes from your mother. Scientists have developed techniques to compare the DNA of a child with that of their parents.

In particular, small bits of DNA that we know are often different between individuals, are copied thousands of times so we can discriminate these important bits from unimportant DNA. These bits of DNA differ in size between different people, so scientists just need to separate the DNA bits (fragments) to compare their sizes. DNA is separated in a slab of gel which works like a series of sieves where the biggest DNA fragments get stuck towards the top, while smaller fragments move towards the bottom where they get stuck. Each person's DNA is analysed separately.

This is a gel being loaded with DNA. The DNA is suspended in a coloured dye before the fragments are separated. The DNA is separated with an electric current.

After the DNA fragments are separated, you can stain the DNA with a dye that is visible under UV light, and this will show you where the DNA fragments are in the gel. This is how it might look:


In column 1 there is a "ruler" that you can use to compare the size of DNA. Next to column 1 you can see DNA sizes. "bp" stands for "base pair", a unit in which DNA is measured. As you can see the largest fragments (23130 bp) are at the top, while the small fragments (564 bp) are at the bottom. Columns 2, 3, and 4 contain DNA samples from different sources.







Say we get DNA from Jane, her baby, and two men who claim to be the father. Who do you think is the father?

The baby shares one DNA fragment with Jane (second from the top). The baby also shares two DNA fragments with Man 2, but none with Man 1. Therefore Man 2 must be the baby's father!









This sort of technique is also used by scientists to identify contamination in foodstuffs (for example, if canned meat is contaminated with other meats that aren't supposed to be in the can), to identify plant and animal species, and to identify bacteria, viruses, and fungi - especially when they are causing disease.