Science – Our galaxy, our future

In conversations with friends, I have occasionally been asked the question, “What is the most beautiful thing you have ever seen?” The answer is always immediate and clear for me. The stars of our home galaxy, the Milky Way, are by far the most beautiful and thought provoking of all observations. The Milky Way galaxy on a clear, moonless night in dark zones away from the light pollution of our cities, inspires deep thought and wonder. Hundreds of thousands of years ago ancient members of our species, Homo sapiens, would have gazed at the same unchanging night sky that we see now, free from the modern distractions of our cluttered planet. Polynesian navigators in waka travelling across the Pacific Ocean several centuries ago, en route from Hawaiki to Aotearoa, charted their journeys using the stars of the southern hemisphere.

Contemporary astronomers using modern telescopes, such as the Hubble Space Telescope, continue to discover extraordinary new insights into the Milky Way. The galaxy consists of two disk-like structures, which we on earth view from the side. Our galaxy contains over 200 billion stars and over 100 billion planets. Planet earth, together with our sun and solar system, is on the fringes of the galaxy. What we see in the night sky is a view back to the centre of the galaxy from about 30,000 light years away. The conclusion is very clear: planet earth and its many forms of life are very insignificant in the massive context of our galaxy. Current thinking suggests that the apparently infinite expanse of space may be filled with many other universes (the multiverse hypothesis). With every new observation using improved telescopes looking deeper and deeper into seemingly empty space, it is apparent that the physical universe continues beyond detection.

Therefore, perhaps the greatest unanswered question in science can now be posed: What are the physical dimensions of the universe(s)?

Recent study has provided an updated age for the Milky Way galaxy at about 13 billion years. This compares to the age of our sun and planet earth (about 4.6 billion years). The first forms of life on planet earth appeared about 4.3 billion years ago and the first hominid (our early ancestors) 3.9 to 2.9 million years ago. Our species, Homo sapiens, emerged from our hominid ancestors from 200,000 to several hundred thousand years ago. A final consensus on a more precise age depends on resolving conflicting theories, which have attracted intense debate.

These timelines reinforce the view of modern science regarding the relative insignificance of Homo sapiens in space and time. This contemporary realisation that we humans are not the centre or pinnacle of all existence may help us deal with critical problems now arising on our increasingly overcrowded and changing planet. Our tenure on earth will not be endless.

Professor Ralph Cooney
r.cooney@auckland.ac.nz