No, you can’t see a black hole. What you might be able to see, though, is the way in which relativity predicts a spinning black hole will bend space, time, and light around it. Scientists say in a new study in Nature Physics that they are closer than ever to being able to see this effect in faraway black holes from our vantage point here on Earth.
Galaxies probably have spinning, supermassive black holes at their center, and spinning black holes possess two types of angular momentum, study coauthor Bo Thide explains. There’s spin angular momentum, which is analogous to what the Earth creates as it spins on its axis, and there’s orbital angular momentum, which is analogous to what the Earth creates as it orbits the sun. Thidé says that the second effect—orbital angular momentum—distorts light in a way that scientists who know what to look for might be able to see it from here.
“Around a spinning black hole, space and time behave in such an odd way; space becomes time, time becomes space, and the whole space-time is actually dragged around the black hole, becomes twisted around the black hole,” Professor Thidé explained. “If you have radiation source… it will then sense this twisting of spacetime itself. The light ray may think that ‘I’m propagating in a straight line’, but if you look at it from the outside, you see it’s propagating along a spiral line. That’s relativity for you.” [BBC News]
That’s the minuscule factor by which time speeds up if you’re elevated just one foot higher from the surface of the Earth, according to new study in Science that cleverly demonstrates Einstein‘s general relativity on a human scale. Don’t rush to move into the basement to extend your life, though: That tiny speck of a difference would account for just about a billionth of a second over the span of the year.
Gravity is the key player in this time variance:
The theory of general relativity: It works. OK, it’s not exactly Earth-shattering news that Albert Einstein’s century-old idea works in real life. That’s been shown over and over. But what had been difficult for researchers to do until now was verify the theory on truly massive scales beyond the solar system, that of whole galaxies and clusters of galaxies. This week in Nature, Reinabelle Reyes and colleagues report that they did it, and that Einstein was proven correct once more.
While the find is a nice coup for Reyes’ team, its importance goes beyond just reaffirming the great scientists of yesteryear with yet another “Einstein was right” story. The existence of dark matter and dark energy is based on the assumption that Einstein’s gravity is affecting galaxies billions of light-years from Earth in the same way that it affects objects in our solar system [National Geographic]. However, if the study had shown that general relativity needed a slight adjustment at vast distances (like the nudge Einstein himself provided to Newton’s physics), that could have altered prevailing ideas about dark matter and energy. This research indicates those pesky ideas may be here to stay [Space.com].