Wringing out a washcloth in space  Apr 18 2013

What happens when you wring a washcloth out in zero gravity? Something cool.

Commander Hadfield is the best. I love when he casually lets go of the wireless mic and it just floats there right in front of his face. (thx, dusty)

The speed of gravity  Sep 07 2010

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!

Hammer vs. feather on the Moon  Oct 02 2009

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.

That's no moon, it's a seamount  Mar 05 2009

There's a fascinating tidbit in this Google blog post about the non-discovery of Atlantis in Google Earth. It concerns how the depth of the ocean floor is measured.

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.

Wow! (via ben fry)

Satellites measuring the earth's gravity from orbit  Aug 10 2006

Satellites measuring the earth's gravity from orbit detected a change in gravity from the massive earthquake that caused the tsunami in the Indian Ocean. "The gravity at the earth's surface decreased by as much as about 0.0000015 percent, meaning that a 150-pound person would experience a weight loss of about one-25,000th of an ounce."

Physicist Lawrence Krauss sums up his thoughts  Jul 11 2006

Physicist Lawrence Krauss sums up his thoughts from a small conference he organized on the topic of gravity. "There appears to be energy of empty space that isn't zero! This flies in the face of all conventional wisdom in theoretical particle physics. It is the most profound shift in thinking, perhaps the most profound puzzle, in the latter half of the 20th century."

I can't tell if this is a  Jun 13 2006

I can't tell if this is a joke or not, but someone seems to be quite skeptical about the "theory of gravity" on this Christian Forums site. "are you going to tell me that the gravity of the sun is strong enough to keep PLUTo in orbit but not an airplane or a little bird??????"

A moving mass has been shown to  Mar 24 2006

A moving mass has been shown to generate a gravitomagnetic field (just like a moving electrical charge creates a magnetic field) and "the measured field is a surprising one hundred million trillion times larger than Einstein's General Relativity predicts". (via rw)

Lisa Randall and Raman Sundrum have proposed  Nov 03 2005

Lisa Randall and Raman Sundrum have proposed some ideas about gravity, extra dimensionality, and string theory that may be testable when the Large Hadron Collider goes online at CERN in 2007.