alive and well - Geological Society of Australia

Feature 2The Square Kilometre Array is on its way“The Sun, with all those planets revolving around it anddependent on it, can still ripen a bunch of grapes as ifit had nothing else in the Universe to do.”In this way Galileo Galilei commented that although the Earthwas no longer to be considered the centre of the Universe, dailylife would go on much as before.Much has changed in the four hundred or so years sinceGalileo turned the newly invented telescope toward the night skyfor the first time. He saw and recorded 20 times more stars thanhad ever been seen with the naked eye. He saw mountains onthe Moon, the bright specks of light revealing the major moonsof Jupiter and the phases of Venus as the planet appeared tochange from a wispy crescent to a filling sphere.From that time onwards, we have built larger and more complextelescopes providing us with an increasingly better ‘eye onthe sky’ to look further out into the Universe.21st Century time machinesThere are two ways for us to look back in time from Earth: wecan either dig through the layers of the Earth’s crust to look atthe geological record of the passing of time, or we can look outinto space. As a consequence of the vastness of space and thefact that light takes time to travel over those vast distances,simply looking far away gives us a glimpse into the past. Build abig enough telescope and you can collect light from the firstgeneration of stars, see the first galaxies to form, and maybe evensee all the way back to just after the Big Bang that began ourUniverse.The SKA telescope aims to do just that — be large enough,and therefore sensitive enough, to see all those things and more.Light comes in many typesBeyond the familiar visible light there are many other types of‘light’ that are invisible to our unaided eyes. This invisible lighttraverses the Universe as a spectrum of waves. At one end of thescale we begin with tightly packed gamma rays and X-raysradiating out from some of the most energetic of objects in theUniverse — objects such as black holes and neutron stars. As wedial in to the next band of frequencies we approach the morefamiliar territory of ultra-violet and visible light.As we slide further along the spectrum the energy andfrequency of waves diminish as the length of the waves, knownas the wavelength, increases. Further tweaking of theelectromagnetic dial takes us beyond the visible and into theinfrared (the basis of night-vision goggles). Next we enter therealm of microwaves and finally the longest waves of all withwavelengths ranging from millimetres to kilometres in length,the domain of radio waves.Radio astronomy is bornThe rather prestigious title of the ‘Father of radio astronomy’ isbestowed on Karl Jansky, a US physicist who in 1932 was workingfor Bell Labs with the seemingly innocuous task of eliminating astatic ‘hiss’ interfering with early overseas telephone communications.Eventually Jansky determined that the hiss wasn’t somethingon Earth within his control, but was in fact a signalemanating from the centre of the Milky Way, and so the scienceof radio astronomy was born. Today most Australians are familiarwith radio astronomy through the CSIRO Parkes radio telescopethat helped bring us the footage of Neil Armstrong’s first stepson the Moon, a story told by that much-loved film ‘The Dish’.Full-size replica of the first radio telescope, built by Karl Jansky and now at the National Radio Astronomical Observatory (NRAO) in Green Bank, West Virginia.Image public domain via Wikimedia Commons.28 |TAG September 2012