Three stories today. A clock that keeps time with the nucleus rather than the electrons stood on its own for a day, a piece of skull from a South African quarry pushed the arrival of Homo erectus back by 200,000 years, and a yellow coral that fits into no known family was found on seamounts off Costa Rica.
Physics
A clock timed by the trembling of a thorium nucleus held itself steady for more than a day without leaning on another clock.
The world's second is set by how fast an electron inside an atom shuttles between two states; that is an atomic clock. But electrons are easily jostled by stray electric and magnetic fields. A nucleus is more than ten thousand times smaller than an atom and far less disturbed from outside, so timing by the nucleus could be more exact. The trouble is that the gap between a nucleus's two states is usually far too wide for light to touch. Thorium-229 is a rare case where the gap is narrow.
Researchers at TU Wien in Austria first lifted thorium nuclei with a laser in 2024, then borrowed an atomic clock to read the time. Now they have let it stand alone. A thorium crystal swallows light only at exactly the right frequency. If the laser drifts, less is swallowed, and that signal nudges the laser back. Steadying itself this way, it ran for more than a day. Its accuracy is around one second of error in thirty million years — still short of the best atomic clocks.
Through the eyes of the Atlas"Measuring with the Same Ruler" asks who decides what a second and a kilogram are. Moving the second from the turning of the Earth to the trembling of atoms was the work of the last century. As with yesterday's story about the Earth's centre of mass, when the reference grows firmer, everything measured against it sharpens too.
A word of cautionThis is a first prototype. Its accuracy does not yet reach the best atomic clocks, and stronger lasers and better crystals are needed.
Source · Phys.org (TU Wien)
Earth
A piece of an adult Homo erectus skull from Drimolen in South Africa reads as about 2 million years old, pushing the species' appearance back by some 200,000 years.
Homo erectus is the species in our own genus that stood upright, walked long distances and left Africa. Until now the earliest place confirmed by adult bones was Dmanisi in Georgia, about 1.8 million years ago.
Researchers from La Trobe University in Australia and from South Africa have now properly described eighteen fossils from the Drimolen quarry, found back in 1992. One of them, a fragment of an adult skull, is Homo erectus, and its age is about 2 million years. The Homo erectus found at the same site earlier was a child of two or three. A child's bones say little about what the adults looked like, and that gap has now been filled. In the same layers a sturdier relative with big teeth and powerful chewing muscles, Paranthropus robustus, outnumbered them more than tenfold.
Through the eyes of the AtlasThe atlas page "Odd People" gathers the people who made the discoveries. Today's story is also a reminder that discovery does not only come from digging new ground: as with the museum-drawer fossil in this column on 26 September, properly describing what was dug up long ago is discovery too.
A word of cautionThe adult evidence is a single fragment of skull. The 200,000 years come from comparing the Drimolen dates with Dmanisi, and the idea that more meat grew the brain is still only a suggestion.
Source · ScienceDaily (La Trobe University)
Life
A tree-shaped coral from seamounts off Costa Rica was given a family of its own after hundreds of its genes were compared.
A coral is a house where thousands of tiny animals live together. On seamounts off Costa Rica, between 360 and 530 metres down, a bright yellow coral branching like a tree was found. The larger colonies stand more than a metre high, and the rock around them was covered in brittle stars, relatives of the starfish.
The team began with the three genes usually read to place a coral. The three pointed to three different families. So they compared hundreds of genes at once instead. That showed a lineage belonging to no existing family, and a new family and genus were created to hold it. Its name was taken from the Elvish language J.R.R. Tolkien invented, and means golden tree.
Through the eyes of the AtlasLinnaeus placed living things by how they look. Now genes are used to measure those places again — and here three genes gave three different answers, which is to say one gene cannot draw a family tree. After the little cats on 20 September, the penguins on the 23rd and the Cretaceous rabbit on the 30th, this is the fourth creature re-placed in this column.
A word of cautionHow many specimens were studied, and whether the coral lives in other seas, is not yet known. Splitting it off as a new family is a judgement about how far it differs from its nearest relatives.
Source · ScienceDaily (University of Costa Rica · ZooKeys)