History on ice
A core some 3.2 kilometres long was pulled from the Antarctic ice, allowing geologists to see at least 750,000 years into the past. Although not the longest ice core ever recovered, it is the oldest, and should contain a record of eight ice ages. Palaeoclimatologists are especially keen to inspect a period some 450,000 years ago when Earth's orbit was very similar to what it is today, giving a good idea of what the present climate might have been like without human influence.
Rats have been a favourite lab animal since the early nineteenth century and, for many studies, provide a better physiological match with humans than mice do. But they missed out on the cloning revolution of the 1990s — the method that gave us cloned mice failed to work. This year researchers came up with a subtly different technique, which involves delaying the activation of the egg, to clone the rodents successfully. Using cloning, it should become easier to produce certain types of genetically engineered rat.
A Russian mathematician claimed to have proved the Poincaré Conjecture, a problem that has gone unsolved since 1904, and which involves properties of objects that do not change when they are stretched or shrunk — such as their number of surfaces. Grigori Perelman of the Steklov Institute of Mathematics in St Petersburg toured American universities describing his solution. Something of an eccentric, he does not plan to submit his work to a peer-reviewed journal.
Particle physicists confirmed the mechanism by which the ghostly particles known as neutrinos flicker between different forms, or 'flavours', with an elegant experiment. Japan's KamLAND detector on the island of Honshu picked up neutrinos belted out by a ring of nuclear reactors that coincidentally surround it. Previous experiments have relied on the Sun as a neutrino source. Although physicists have a good idea of the number and type of neutrinos emitted by the Sun, there remained a tiny uncertainty, which the KamLAND experiment neatly eliminated.
The second of the two basic building blocks of a quantum computer — a 'controlled NOT' logic gate, which flips the state of a target bit of information based on the state of a control bit — was demonstrated by several teams this year. One group managed to make the gate in a solid-state system, using electrons in a silicon chip. The same team also made a solid-state version of the first building block — a 'rotation' gate — in 1999. But no one has yet linked the two gates together to form a functioning computer.
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Highlights. Nature 426, 753 (2003). https://doi.org/10.1038/426753a