What causes great balls of fire?

Two scientists have proposed a new theory to explain why balls of light about the size of a child's head sometimes appear in a storm as if by magic, drifting around for several seconds before disappearing.

Two scientists have proposed a new theory to explain why balls of light about the size of a child's head sometimes appear in a storm as if by magic, drifting around for several seconds before disappearing.

John Abrahamson and James Dinniss, chemical engineers from the University of Canterbury in Christchurch, New Zealand, have suggested in the journal Nature that ball lightning is created when silicon and its chemical compounds in soil are liquified by the intense heat of a lightning strike - causing a chemical reaction that results in a ball of burning silicon to rise from the ground.

The spheres of light can be anywhere in size between that of a golf ball to a large beachball. They last for about 10 seconds, or sometimes longer, and float freely in the air, rising and falling with currents of air. Sometimes the ball, which has the intensity of a light bulb, simply fades from view. Other times it ends with a small explosion, singeing any wooden objects it touches.

When ordinary lightning strikes soil it imparts enough energy to silicon substances in the ground to eject them into the air as a network of filaments which form a ball of loose, fluffy material. As the particles slowly burn, the stored energy is released as heat and light, the researchers suggest.

Although the scientists have not as yet been able to recreate ball lightning in the laboratory, they hope that their latest theory may spark further attempts at making it artificially.

Another link between humans and the lowest forms of life has been established with the discovery that bacteria share an oxygen-carrying protein we also use in our muscles. Myoglobin, which is similar to the body's main oxygen-carrying protein, haemoglobin, found in red blood cells, seems to have been an essential feature of life's evolutionary development going back billions of years.

Researchers from the University of Hawaii, led by Maqsudul Alam, associate professor of microbiology, found genes for myoglobin in the ancient microbe Halobacterium salinarum, and the more widely known bacteria, Bacillus subtilis. "These proteins may help to understand how sensory systems evolved in higher organisms," Professor Alam said. A central, iron-containing sub-unit of the myoglobin protein - called haem - appears to be involved in oxygen sensing. Although oxygen is essential for energy production, it is also potentially toxic. "The presence of oxygen was both a blessing and curse," Professor Alam said.

The research, published in Nature, helps scientists to trace the evolutionary divisions between plants, animals, and bacteria. Professor Alam suggests that the work could eventually help to understand when and how life began.