chapter 3
Building blocks Our understanding of the universe has moved on considerably since Galileo’s time. Taking a look at the universe through modern eyes we can see a sequence of building blocks that make up our understanding of the universe as a whole. We can zoom out from the most basic detail to provide all the essentials needed to put together a picture of the universe. It starts at the most fundamental level with physics. All matter is made up of atoms. It was once thought that these were the absolute limit of our ability to divide matter up. That’s why they are called atoms. The name comes from the Greek atomos, meaning uncuttable. Imagine cutting up something into smaller and smaller pieces. When you reach the limit and it is possible to cut no further, you have the most basic component, and this was called an atom.
Over time, gravity pulls matter in the accretion disk into planets
A composite of Jupiter’s four largest moons (Jupiter is not to scale)
74 Our neighbourhood
still a liquid (as any metal can be at the right temperature), but like a metal its electrons are relatively free to move around, conducting heat and electricity. However, just because Jupiter is mostly liquids and gasses doesn’t make it a bland, featureless ball. Apart from the great spot, the planet is ringed with different coloured bands and swirls, clouds that are mostly made up of frozen crystals of the nitrogen and hydrogen compound, ammonia. The atmosphere has several more elements present – if there was some way to visit and float on the ‘surface’ of Jupiter, among the vast lightning bolts, hundreds of times more powerful than we experience on Earth, you might see glowing pink neon rain. Another way of appreciating the size of Jupiter is that if you lumped together all the other planets you wouldn’t reach half the mass of this monster. (And bear in mind that with so much hydrogen, Jupiter isn’t particularly dense.) Even though Jupiter is over 750 million kilometres from then Sun, making it around 600 million kilometres away from us at the closest point in the two planets’ orbits, it is often the second brightest object in the night sky after the Moon when Venus is below the horizon. Mars can top it at its closest, but Jupiter appears a clear white colour to the naked eye and is easily distinguished. Jupiter was also the first planet, apart from Earth, that was known to have moons. When Galileo trained his early telescope on Jupiter, as we have seen, he discovered four bodies orbiting it. Now we know that there are many more. Jupiter’s massive gravitational pull is very good at capturing stray rocks. There are 63 moons that have been given names (it’s hard to give an exact number when you get down to small captured asteroids). The big four moons, those spotted by Galileo, are, in decreasing order of size, Ganymede, Callisto, Io and Europa. To put them into scale, all but Europa are bigger than are own Moon, which is unusually large in its own right. The biggest, Ganymede, is over 5,200 kilometres across (compared with the Moon’s 3,400 kilometres), making it bigger than the planet Mercury. You might expect that these natural satellites would be boring
Our neighbourhood 75
The auxiliary telescopes at Cerro Paranal in Chile
l e ft
b e lo w l e ft Mount Palomar’s Hale telescope, for decades the largest in the world b e lo w The giant Arecibo radio telescope in Puerto Rico
How do we know? 137
Exploring
the
UnivErsE
Exploring UnivErsE the
There are few topics more awe-inspiring than cosmology. What is the universe? How does it work? Where did it come from? These fundamental questions intrigue adults and children alike. This approachable guide brings alive humanity’s attempts to explain the existence of everything and explores the latest and best theories on how the universe came into being. From the basic understanding of the nature of a star, or of how a planet like the Earth was formed, the remarkable story of cosmology unfolds through to the truly ultimate question of how the universe will end. Along the way we will meet black holes and dark matter, supernovae and quasars. The universe is populated with a strange cast of characters that this richly illustrated book brings alive. Clearly written, this engaging text assumes no previous knowledge, and uniquely in such an illustrated book, the reader is taken beyond the certainties to explore the strange concepts that fill modern cosmology. This book is for students, amateur astronomers, and anyone who has looked up at the sky and wondered about our place in the universe. The Author: Brian Clegg is the best-selling author of numerous titles on popular science including Armageddon Science, A Brief History of Infinity, and Ecologic to name but a few. He lectures widely and has given sell-out lectures at the Royal Institution in London and venues ranging from Oxford and Cambridge Universities to Cheltenham Festival of Science. He contributes to radio and television programs and is a popular speaker at schools.
Contents Introduction Where did we come from? Music of the spheres Building blocks Our neighbourhood A growing space A bang or a whimper How do we know? Most of our universe is missing Cosmic oddities Just a theory The ultimate question
Specifications 245 x 190 mm (71/ C x 95/ I in) 192 pages with 130 illustrations 35,000 words Hardback Recommended retail price: £ 19.95 | € 24.95 | US$ 35.00 ISBN 978-1-908126-16-0 February 2012
Key features * Clearly and engagingly written for all ages * Stunning photographs from NASA and other sources of up-to-date imagery
Brian Clegg www.vivays-publishing.com