Nature Notes - TM Natural History Association

The Night Hunter

Details: Created: Tuesday, 07 February 2012 00:00; Written by Nadia O’Carroll

Owls are distinctive birds. Their forward facing, staring eyes; dished face: stealth and nocturnal life, which give them an aura of wisdom, power and mystery, are also attributes of an extremely sophisticated night hunter.

Owl eyes are adapted to night vision. Their eyes are large (up to 5% of body weight), and forward facing for binocular vision. Instead of eyeballs, their eyes are like tubes held in place by bony rings, the pupil of an owl can dilate to the very edge of the eye for maximum light exposure. Owls cannot move their eyes; they can only look straight ahead. To overcome this restriction, their neck is extremely flexible. Owls have fuzzy, low colour vision that is effective in low light and is highly sensitive to movement.

Auroras

Details: Created: Tuesday, 24 January 2012 00:00; Written by Nadia O’Carroll

Around the world the arrival of the New Year is celebrated by massive displays of fireworks, which utilise chemical reactions to produce brightly coloured, sparkling incandescent and luminescent light.

Visible light can be described as electromagnetic radiation that can be perceived by the human eye. The colours of the visible spectrum are red, orange, yellow, green, blue, indigo and violet (in order of longer to shorter wavelengths).

Thunderstorms

Details: Created: Tuesday, 29 November 2011 00:00; Written by Nadia O’Carroll

Thunder and lightning are caused by an atmospheric discharge of electricity. In storm clouds, positive and negative particles may become separated (polarised), the positively charged particles rise to the top of the cloud and the negatively charged particles drop to the lower part of the cloud. If a sufficiently strong electric field develops, there will be enough electric potential for lightening to form. 90% of lightning is cloud to cloud where the exchanges of lightning usually expend the electrical charge. 10% of lightning is cloud to ground. The earth below the thundercloud develops an equal but opposite charge to the cloud above. A path of negatively charged ionised air (leader) moves downward from the cloud in jumps. On the ground positive streamers, which may become a positive leader, move upwards, and when the negative and positive leaders connect, the electric field greatly increases. When it becomes strong enough to form a channel, an electric discharge occurs and this is seen as a lightning bolt. The electrical discharge super-heats the air around and creates an audible shock wave, which is heard as thunder. Leader bolts of lightning can travel 60,000 m/s and can heat the surrounding air to 30,000 degrees (C). Although a bolt of lightning produces intense light and sound, its diameter is usually only 2-5cms.

Christmas Weather

Details: Created: Tuesday, 13 December 2011 00:00; Written by Nadia O’Carroll

Christmas in Australia occurs in midsummer, yet many of our Christmas trappings and traditions relate to cold midwinter weather and the classic snowy white Christmas. This is not surprising since most Christmas traditions, and most of us, originate from Britain and Europe.

The winters and summers of each hemisphere are opposite. This is because the Earth is tilted on an axis of 23.5 degrees, and when its lower half tilts towards the Sun, the angle of the Sun’s rays striking the Earth’s surface concentrate heat in the Southern Hemisphere, and spread the heat in the Northern Hemisphere. However other factors can effect local weather, and ironically on Christmas Day in 2006, snow fell on Mt Buller, while according to the UK Met Office and the UK bookmakers, there was no “official” white Christmas in Britain that year.

Fog and Mist

Details: Created: Tuesday, 15 November 2011 00:00; Written by Nadia O’Carroll

From time to time we see fog and mist in Tamborine Mountain and surrounding areas.

Fog and mist are dense clouds of water droplets suspended in air close to the ground. Fog is denser than mist; fog reduces visibility by more than 1 km while mist reduces visibility by less than 1 km.

The formation of fog and mist is a result of the processes of condensation and evaporation.