Saturday, April 19, 2014

Measuring the Distance from the Earth to the Moon


via NASA

"Explanation: This is not a scene from a sci-fi special effects movie. The green beam of light and red lunar disk are real enough, captured in the early morning hours of April 15. Of course, the reddened lunar disk is easy to explain as the image was taken during this week's total lunar eclipse. Immersed in shadow, the eclipsed Moon reflects the dimmed reddened light of all the sunsets and sunrises filtering around the edges of planet Earth, seen in silhouette from a lunar perspective. But the green beam of light really is a laser. Shot from the 3.5-meter telescope at Apache Point Observatory in southern New Mexico, the beam's path is revealed as Earth's atmosphere scatters some of the intense laser light. The laser's target is the Apollo 15 retroreflector, left on the Moon by the astronauts in 1971. By determining the light travel time delay of the returning laser pulse, the experimental team from UC San Diego is able to measure the Earth-Moon distance to millimeter precision and provide a test of General Relativity, Einstein's theory of gravity. Conducting the lunar laser ranging experiment during a total eclipse uses the Earth like a cosmic light switch. With direct sunlight blocked, the reflector's performance is improved over performance when illuminated by sunlight during a normal Full Moon, an effect known as the real Full Moon Curse."

Friday, April 18, 2014

Cell vs. Virus: A Battle for Health



"All living things are made of cells. In the human body, these highly efficient units are protected by layer upon layer of defense against icky invaders like the cold virus. Shannon Stiles takes a journey into the cell, introducing the microscopic arsenal of weapons and warriors that play a role in the battle for your health.

Lesson by Shannon Stiles, animation by Igor Coric."

Tuesday, April 15, 2014

Saturn Forming New Moon?



via NASA

"The disturbance visible at the outer edge of Saturn's A ring in this image from NASA's Cassini spacecraft results from gravitational effects on ring particles by an object that may be replaying the birth process of icy moons. Cassini's narrow-angle camera recorded this view on April 15, 2013."

Thursday, April 10, 2014

Blackbeard


via Wikipedia

"Edward Teach (also Edward Thatch, c. 1680 – 22 November 1718), better known as Blackbeard, was a notorious English pirate who operated around the West Indies and the eastern coast of the American colonies. Although little is known about his early life, he was probably born in Bristol, England. He may have been a sailor on privateer ships during Queen Anne's War before settling on the Bahamian island of New Providence, a base for Captain Benjamin Hornigold, whose crew Teach joined sometime around 1716. Hornigold placed him in command of a sloop he had captured, and the two engaged in numerous acts of piracy. Their numbers were boosted by the addition to their fleet of two more ships, one of which was commanded by Stede Bonnet, but toward the end of 1717 Hornigold retired from piracy, taking two vessels with him..."