Gravity. Can’t see it. Can’t live without it. It keeps us on the Earth and if you fall from a great height, you’ll fall at the same speed as anything else on this planet.
Brian Clegg’s book ‘Gravity’ explores the history of its discovery from Galileo through to Newton and beyond. It’s also rather interesting how Clegg puts to death certain myths about these early scientists and if might stop you looking at an apple tree and wonder why only Newton spotted the phenomenon of falling. The exploration of quantum mechanics might seem complicated for some of you but please persist with that chapter when you get there because it will give you some insight into where gravity starts from.
For Science Fiction readers and writers, chapter eleven, ‘Cavorite Returns’ should be required reading for you to ponder over. For instance, if you want to maintain an Earth-type gravity, then you really shouldn’t travel faster than 9.81m(32 ft)/second/second which means you’d never get far within a generation.
I’ve never come across the precise definition difference between speed and velocity like this before. Speed is scalar, the number you’re moving at. Velocity combines speed with direction. Remember that when you’re using both words as I’m pretty sure I’ve confused this in the past myself.
Clegg explains a lot of forms of what appears to be anti-gravity that isn’t, ranging from gas balloon buoyancies to strong magnet propulsion and super-conductivity.
One thing I would take issue with him over is the assertion that stopping gravity, objects would travel at nearly the speed of light. Granted some of the lower grade SF writers might have gotten that wrong but he ought to read Isaac Asimov’s short story ‘The Billiard Ball’ (it’s in ‘Asimov’s Mysteries’ for those who haven’t read it). Essentially, the universe is expanding and if you stopped moving relative to it, then the rest of the universe would move away from you. For those watching on the planet, you would have effectively sped away at a high velocity, although it’s not you but them in the expanding universe doing so. Not perhaps at the speed of light but it’s easy to see why it’s described that way. It would be a great way to travel but you would never be able to catch up with the expanding universe.
Things I learnt and occasionally puzzled over.
In space, a plant’s roots don’t know which was to go. That made me think a little. If they’re in zero gee and encased in a plastic bubble, then all it would need is the occasional water and nutrients injected.
The information on page 7 about how the body would change if you were born in zero gee should be required reading for all SF writers and you would be dooming such people to never come down to earth (sic).
If you ever wondered how science started off by being called a philosophy, then you can blame Aristotle because he would debate how things work than prove it by experimenting and it took a long time to shake that off, which we owe to Galileo. In many respects, Aristotle sounds a lot like those people we have around today who let they fears think for them than proof.
The event horizon of a black hole is just under ten miles. That one I would like to see proved. You can probably use angular momentum, that’s being in orbit, to stop falling into a singularity but I’d wonder at the astronaut who would put that to the test.
With the four basic forces of the universe, I’m still puzzling why no one looks at why the weak and strong nuclear forces aren’t considered being closer together.
The most important lesson I learnt relates to the sun. We all know that if it explodes, it would take eight minutes before the event destroyed us. As such, we would still be in orbit around the sun until then indicating that the effects of gravity take the same eight minutes to reach us. If that doesn’t make you ponder, then read this book to find out more.
As you can tell from my responses above, I found this an interesting book. As the uses of gravity is something that comes up a lot in Science Fiction, this should be a book all of us need to read, if for no other reason than to use accurate facts.
(pub: Duckworth Overlook. 322 indexed page hardback. Price: £14.99 (US). ISBN: 978-0-71564-360-0)
check out website: www.ducknet.co.uk