LAST year was the warmest the world has experienced since records began more than a century ago, the United States space agency, NASA, revealed last night.
Researchers have calculated that 2005 saw the highest annual average surface temperature worldwide since the late 1800s.
They believe it beats the previous record, set in 1998, when El NiƱo, a natural phenomenon caused by shifts in prevailing winds and ocean currents that occurs every two to ten years and brings unusually warm seas in the eastern Pacific and cooler waters in the west, boosted global temperatures.
James Hansen, director of NASA's Goddard Institute for Space Studies, said that because no direct data was available in the Arctic, analysts had to estimate temperatures from nearby weather stations.
As a result it was not possible to say with certainty that 2005 had been the hottest year yet, but he added: "I'm reasonably confident it was".
The short answer is "no", but it is a qualified "no" because there are odd ways of interpreting the question which could justify the answer "yes". Light is composed of photons so we could ask if the photon has mass. The answer is then definitely "no": The photon is a massless particle. According to theory it has energy and momentum but no mass and this is confirmed by experiment to within strict limits. Even before it was known that light is composed of photons it was known that light carries momentum and will exert a pressure on a surface. This is not evidence that it has mass since momentum can exist without mass. [ For details see the Physics FAQ article What is the mass of the photon? ]. Sometimes people like to say that the photon does have mass because a photon has energy E = hf where h is Planck's constant and f is the frequency of the photon. Energy, they say, is equivalent to mass according to Einstein's famous formula E = m...
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