Some birds, including sparrows and herring gulls, lay their eggs so that the last one to come out is a shade or two lighter than the others. You might suppose that laying eggs requires some effort and that the colour of the last egg is a sign of an exhausted mother. But this practice might be of evolutionary advantage.
Earlier this year, a group of scientists at Bell Labs announced that they had succeeded in observing the effects of "dark matter" - invisible matter that can be detected only by its gravitational effects.
More than a century ago, an American astronomer named Seth Carlo Chandler discovered that, as the earth spun on its axis, it also wobbled. This wobble, now known as the Chandler wobble in honour of its discoverer, didn't disappear over time, as would have been expected if no further force reactivated it. The source of the continuing activating force has remained a mystery ever since - until now.
The Millennium Bridge across the Thames opened in June 2000 and was subsequently closed two days later because of the now-famous "wobbles". Given that, at any instant, two thousand people were suspended above a very dangerous river, this presented a serious problem.