A black hole – one of the most fearsome and powerful objects in the universe – as big as a few atoms, in a lab? Sounds unlikely; but it’s not weird science. Well, perhaps there is a little exaggeration, but researchers at Harvard University (Massachusetts, USA) have created the miniest of black hole like behavior using a carbon nanotube.
“On a scale of nanometers, we create an inexorable and destructive pull similar to what black holes exert on matter at cosmic scales,” says Lene Vestergaard Hau, Mallinckrodt Professor of Physics and of Applied Physics at Harvard. “As importantly for scientists, this is the first merging of cold-atom and nanoscale science, and it opens the door to a new generation of cold atom experiments and nanoscale devices.”
“From the atom’s point of view, the nanotube is infinitely long and thin, creating a singular effect on the atom,” Hau says.
The experiments that produced this effect have a kind of drama to them.
It starts in a tiny cryochamber (super cold) where atoms of rubidium have been chilled by laser manipulation to a fraction of a degree (Kelvin) above absolute zero. Then like a cloud one millimeter in length the atoms are propelled toward a single nanotube, suspended in the chamber, similarly cooled but charged with hundreds of volts. The distance is short, two centimeters; even so something dramatic happens to the atoms. Most of the atoms go zipping by the nanotube, but some that come within less than a micron are pulled toward it. They spiral inward gaining fantastic speed – from 5 meters per second to 1,200 meters per second (2,700 miles per hour). Because they are going so fast, the atoms heat from near absolute zero to thousands of degrees Kelvin in less than a microsecond. Coming closer to the nanotube, the atoms start to go really fast and separate into an electron and an ion rotating in parallel. Each orbit takes only a few trillionths of a second. Suddenly the electron is sucked into the nanotube (via quantum tunneling) and the ion goes rocketing away. It’s so repelled by the strong charge of the nanotube that it is travelling at 26 kilometers per second (59,000 miles per hour). Then it’s over, ions dispersed and atoms disintegrated.
It’s all over in a few microseconds. In this super cold, super controlled environment nearly everything gets monitored and measured. The scientists have a ton of data to sift. Some of that has already been done, but it’s clear that in this case they’re still trying to find appropriate points of reference. Black hole isn’t really such a touchpoint, although the image of atoms sucked into a tube sort of fits. What really is going on – why the nanotube has such ‘powers’ – is an open question, as is the question of what this effect might do or be used for.