Who, What, Why: Is the Earth getting lighter? 31 January 2012Last updated at 01:21 By Charlotte McDonald BBC News The recent crash landing of Russian spacecraft Phobos-Grunt has focused attention on the increasing amount of space junk orbiting the planet. So does this mean the Earth has been getting lighter? The BBC's Radio 4 programme More or Less turned to a group of Cambridge University academics for the answer. There are factors that are causing Earth to both gain and lose mass over time, according to Dr Chris Smith, a medical microbiologist and broadcaster who tries to improve the public understanding of science. Using some back-of-the-envelope-style calculations, Dr Smith, with help from physicist and Cambridge University colleague Dave Ansell, drew up a balance sheet of what's coming in, and what's going out. All figures are estimated.
By far the biggest contributor to the world's mass is the 40,000 tonnes of dust that is falling from space to Earth, says Dr Smith. Continue reading the main story The answer Finding space dust. EiC November 2008 - Feature - Exhibition chemistry. Dynamic Periodic Table. The cost of petrol and oil: How it breaks down. 7 November 2011Last updated at 19:00 ET By Richard Anderson and Damian Kahya Business reporters, BBC News Only about a third of the cost of petrol at the pumps actually represents the cost of the raw material from which it is made - oil We all know petrol costs a lot, but how many of us actually know why, and who profits from selling the stuff?
The cost of petrol and diesel can actually be broken down fairly precisely, and it's immediately obvious who the primary beneficiary is: the government. Well over half, in fact about 60%, of the £1.34 odd we pay for a litre of unleaded is fuel duty and VAT. Less than 5% goes to the petrol retailer, in some cases more like 1%, which helps in part to explain why so many are struggling despite recent rises in fuel costs. Next to tax, the single biggest component in the price of petrol is... well, the petrol itself, which accounts for about 30% of the overall cost. This is what the retailers actually pay for the petrol that comes out of the pumps.
C5. C6. C7. Single-molecule 'electric car' taken for test drive. 9 November 2011Last updated at 18:00 By Jason Palmer Science and technology reporter, BBC News The molecular "car" bounced along the atoms of a flat copper "road" Scientists have shown off what can be described as the world's smallest electric car - made of a single, carefully designed molecule. The molecule has four branches that act as wheels, rotating when a tiny metal tip applied a small current to them. With 10 electric bursts, the car was made to move six billionths of a metre. The approach, published in Nature, joins recent single-molecule efforts, and seems to overcome the forces that often dominate at such tiny scales.
The "batteries" of the electric car come by way of the tip of what is called a scanning tunnelling microscope - an extraordinarily fine point of metal that ends in just an atom or two. The motor of the approach lies with the four "molecular rotors" that act as the car's wheels; they undergo a change in shape when they absorb the electrons.