A European Space Agency probe will be launched into space early next month to help test the last major prediction of Einstein's theory of general relativity: the existence of gravitational waves.
Gravitational waves are thought to be hurled across space when stars start throwing their weight around, for example, when they collapse into black holes or when pairs of super-dense neutron stars start to spin closer and closer to each other. These processes put massive strains on the fabric of space-time, pushing and stretching it so that ripples of gravitational energy radiate across the universe. These are gravitational waves.
The Lisa Pathfinder probe won't measure gravitational waves directly, but will test equipment that will be used for the final detector.
LISA Pathfinder will pave the way for future missions by testing in flight the very concept of gravitational wave detection: it will put two test masses in a near-perfect gravitational free-fall and control and measure their motion with unprecedented accuracy. LISA Pathfinder will use the latest technology to minimise the extra forces on the test masses, and to take measurements. The inertial sensors, the laser metrology system, the drag-free control system and an ultra-precise micro-propulsion system make this a highly unusual mission.
[Mild spoilers] During the production of Gravity, Jonas Cuaron (co-writer of the screenplay and Alfonso Cuaron's son) shot a short film that shows the other side of the conversation that Sandra Bullock's character had while in the Soyuz capsule. In the film, an Inuit fisherman struggles to communicate with the distressed voice on the other end of his radio.
The short was filmed "guerrilla style" on location on a budget of about $100,000 -- most of which went toward the 10-person crew's travel costs -- and Cuaron completed it in time to meld the dialogue into Gravity's final sound mix. The result is a seamless conversation between Aningaaq and Ryan, stranded 200 miles above him, the twin stories of isolated human survival providing thematic cohesion. Still, Jonas says he was careful "to make it a piece that could stand on its own." Should both get Oscar noms, an interesting dynamic would emerge: Two films potentially could win for representing different sides of one conversation, to say nothing of having come from father and son.
Also interesting is that Visitors is comprised of only 74 shots, which with a runtime of 87 minutes means the average shot lasts over a minute. According to a recent investigation by Adam Jameson, an ASL (average shot length) of more than a minute is unusual in contemporary film. Inception, for instance, has a ASL of just 3.1 seconds and even a film like Drive, with many long shots, has an ASL of 7 seconds. But as Jameson notes, Alfonso Cuarón's upcoming Gravity contains only 156 shots, including a 17-minute-long shot that opens the film. But the Hollywood master of long-running shots? Hitchcock, I presume:
1. Rope (1948, Alfred Hitchcock), ASL = 433.9 [seconds]
OK, this isn't a recent recent film, but it has to be noted, as it's most likely the highest ASL in Hollywood. Hitchcock used only 10 shots in making it (the film's Wikipedia page lists them). (As you probably know, Hitchcock designed those shots, then edited them such that the finished film appeared to be a single take.)
Newton said the speed of gravity is infinite but according to Einstein (and some nifty interstellar measurements), it most certainly is not.
But in general relativity, things are much more intricate, and incredibly interesting. First off, it isn't mass, per se, that causes gravity. Rather, all forms of energy (including mass) affect the curvature of space. So for the Sun and the Earth, the incredibly large mass of the Sun dominates the curvature of space, and the Earth travels in an orbit along that curved space.
If you simply took the Sun away, space would go back to being flat, but it wouldn't do so right away at every point. In fact, just like the surface of a pond when you drop something into it, it snaps back to being flat, and the disturbances send ripples outward!
Nothing like a little science on the Moon, I always say.
Astronaut David Scott in 1971, from the Apollo 15 Lunar Surface Journal. Scott was part of the Apollo 15 crew, and applied Galileo's findings about gravity and mass by testing a falcon feather and a hammer. The film, shown in countless high school physics classes, is the nerdy, oft-neglected cousin of Neil Armstrong's space paces.
Now you're probably wondering where the rest of the depth data comes from if there are such big gaps from echosounding. We do our best to predict what the sea floor looks like based on what we can measure much more easily: the water surface. Above large underwater mountains (seamounts), the surface of the ocean is actually higher than in surrounding areas. These seamounts actually increase gravity in the area, which attracts more water and causes sea level to be slightly higher. The changes in water height are measurable using radar on satellites.