Brace yourselves ? here comes a plug! New Scientist
has just launched a new book ? Why Don't Penguins' Feet Freeze?
? packed with the best questions and answers from New Scientist's endlessly fascinating Last Word
column. It's already top of bestseller lists in the UK.
If you don't know already, Last Word
is where you, the users, ask and answer questions on the weird and wonderful everyday science that is puzzling you. So, "how fat do you have to be to be bulletproof?"
is one that I liked, and "how long can a human live on beer alone?"
To give you a taste of the book, we've posted a space-related question and answer taken from it below. You can add your own answers in the comments below. And if you would like to buy the book, there's a discount for users
As the Sun produces energy, it presumably loses mass and its gravity weakens. Are the planets slowly spiralling outwards? If so, by how much, and by the time the Sun becomes a red giant, how far out would the Earth be?Answer:
The Sun loses about 4 million tonnes per second, which is the mass equivalent of the energy it produces through thermonuclear reactions. Another few million tonnes are lost in solar wind and other particle emissions. However, even after 2 billion years, this loss constitutes only one 10-thousandth of the Sun's mass. So the change in the Earth's distance from the Sun will be of the same fractional order.
The situation will be more drastic when the Sun eventually becomes a red giant, six billion years or so from now. Then, the solar radius will be a hundred times its present value. Some of the latest estimates suggest that in its giant stage the Sun may well engulf Mercury, Venus and Earth, while planets more distant than Mars will survive and continue to orbit the sun when it later becomes a white dwarf.
If we assume the final mass of the sun at the white-dwarf stage to be 0.6 of its present value, the dimensions of the planetary orbits in the very far future will be about 80% greater than they are now for the reasons your questioner suggests.C. Sivaram, Indian Institute of Astrophysics, Koramangala, Bangalore, IndiaAnswer:
Amazingly, although the Sun converts 4 million tonnes of its mass into pure energy every second and will continue to "burn" hydrogen until it becomes a red giant several billion years from now, it will even then have lost only a tiny proportion of its present mass. In order for the Earth to conserve its angular momentum, the radius of its orbit will have to increase at the rate of only about 1 centimetre a year.
However, this will not be sufficient to compensate for the steadily increasing luminosity of the Sun. So Earth is destined to follow in the footsteps of its celestial companion, Venus, and undergo a natural runaway greenhouse effect - unless human activity contrives to accomplish it rather sooner.Mike Follows, Willenhall, West Midlands, UK
If you'd like more, you can get the book here
. And if you missed it last year, you'll find its bestselling predecessor ? Does Anything Eat Wasps?
? here on Amazon