Score one for basic science: if you smash atoms together at high energies, you can't make black holes -- yet.

The Large Hadron Collider, a particle accelerator run by the European Organization for Nuclear Research (CERN), has been smashing protons together at about halfway to full power.

The scientists who did the experiment were looking for microscopic black holes. They didn't see them -- but they think that with a little more power, they could.

Most people think of black holes as gigantic objects that swallow everything around them. That's true if you are looking for naturally occurring ones in space.

Black holes form whenever a big enough mass is compressed in to a small enough space. The material becomes so dense that its gravity pulls in everything - even light. There are two ways to compress the mass: pile lots of it up in one place (as happens in stars much more massive than the sun) or smash protons together at high speed.

Because mass and energy are equivalent, with enough energy one could create a black hole. But the experimenters at CERN didn't find any, even when they smashed the protons together at 3.5-4.5 Tera electron volts (TeV).

In and of itself that isn't a lot of energy, but it represents a proton being flung around the accelerator at 99.99 percent the speed of light. At that speed each proton is thousands of times more massive and packs a much bigger punch than they ordinarily would.

These tiny black holes won't swallow everything around them because they don't last long, existing only for tiny fractions of second. Creating anything longer-lived would require a particle accelerator with thousands of times more energy than the LHC.

Not finding them means that there are limits on how these tiny black holes could be made, though the set of assumptions used was rather simplified, said Albert de Roek, a senior research scientist and staff member at CERN, in an email. It also means that it would take more energy to observe evidence for things such as extra spatial dimensions.

Formation of black holes would have been evidence for that, he said, but it is still not clear what the implications are. Also, with more collisions scheduled for the coming year, researchers can get a better idea of how flexible the limits are.

The LHC has only been running at about half of the energy it was designed to work at. By 2014 there will be collisions closer to the 14 TeV range, which is an order of magnitude larger than any particle accelerator has ever produced before. That will show what the minimum mass for a black hole really is, de Roek said.