Black holes seem like science's answer to a sci-fi blockbuster: warping the very fabric of space-time and imprisoning light and matter in a gravitational death grip, they lie in wait, ready to swallow fleets of starships or consume whole worlds.
Scientists have cast black holes in another role recently - as leads in a big-budget extravaganza of a different kind: helping physicists assess the real-world existence of that other science fiction favourite, the hidden extra dimensions of space.
For it now appears that astrophysical titans several times the mass of the Sun or midget black holes smaller than a subatomic particle could provide proof of an extra-dimensional existence.
Astrophysicists are looking into space with new fervour, trying to see if large black holes are shrinking on a time-scale that might be detected by modern telescopes. If so, it might mean the black holes are evaporating into extra dimensions.
In the laboratory, black holes far smaller than anything that could be seen with a microscope might be produced in Europe's Large Hadron Collider (LHC) now that it is back in operation.
The detection of such a black hole, which would evaporate in a hail of subatomic particles in a tiny fraction of a second, would provide evidence that unseen dimensions of space exist.
What makes either of these ideas even plausible is a bold theory, put forth just over 10 years ago, that purports to explain the weakness of gravity by supposing that some of it is leaking out into extra dimensions.
Gravity may feel strong to us because it makes climbing hills hard. But one of the fundamental paradoxes about gravity is that it is actually quite weak: an ordinary refrigerator magnet can pick up a paperclip and, in so doing, counteract the entire gravitational mass of the Earth pulling down on the clip.
Particle physicists call this the 'hierarchy problem', referring to the fact that all the other forces of nature are more than 30 orders of magnitude stronger than gravity.
"It's hard to explain such a huge number from any mathematical postulate or any physical principle," says Greg Landsberg from Brown University in Providence, Rhode Island, USA. "It's a bit of an embarrassment for our field, because what it really means is [that] we don't seem to understand gravity."
Isaac Newtown declared in the 17th century that gravity gets weaker by the square of the distance between two objects. If the Moon were twice as far from Earth, it would feel one quarter the gravity. But in 1998, theoretical physicists Nima Arkani-Hamed, Savas Dimopoulos and Gia Dvali pointed out that gravity had never been measured below a distance of about a millimetre.
