Totality

Totality of a lunar eclipse, as witnessed in Sidney, Australia, by way of fizzenergy.com, a sample of Photography that is Out of This World. "The moon gradually glides into the Earth’s shadow, until the normally pale white colour disappears and is replaced by an orange and red hue," accurately enough, though this fails to mention the intervening stage. Because before the blood-red appears at totality, the curve of Earth casts the darkest evidence of our home planet's curvature, and the relatively enormous distance to the Sun, can be deduced, also, when only a few simple facts are already known. The blood red of totality, "is caused by sunlight being refracted around the edge of the Earth, through the atmosphere. Blue light from the sun tends to be scattered by the atmosphere so the light that reaches the surface of the moon during a lunar eclipse is predominantly red."

New tool to visualize lunar eclipse

"Researchers at Rensselaer Polytechnic Institute have developed a new method for using computer graphics to simulate and render an accurate visualization of a lunar eclipse. The model uses celestial geometry of the sun, Earth, and moon, along with data for the Earth's atmosphere and the moon's peculiar optical properties to create picture-perfect images of lunar eclipses."

"The computer-generated images, which are virtually indistinguishable from actual photos of eclipses, offer a chance to look back into history at famous eclipses, or peek at future eclipses scheduled to occur in the coming years and decades. The model can also be configured to show how the eclipse would appear from any geographical perspective on Earth..."

Read the Post at PhysOrg HERE.

Italian 14-19 year olds measure moon's distance

Last week, four Spanish students revealed how they had taken pictures of the curvature of the Earth by attaching a digital camera to a helium balloon and letting it go. When the British newspaper The Daily Telegraph reported the work, the story snowballed, attracting worldwide coverage.

Now a group of 30 Italian students from classes 1SD and 1SE at the Liceo Scientifico "A. Vallisneri" in Lucca, Italy have gone one better with an ingenious measurement of the distance to the moon.

The students analysed an mp3 recording of the conversation between Neil Armstrong on the surface and ground control in Houston in which he utters his famous "one small step" speech. The recording is available on the NASA website.

They noticed an echo on this recording in which sentences from Earth are retransmitted via Armstrong's helmet speaker through his microphone and back to Earth. They used the open source audio editing program Audacity to measure the echo's delay which turned out to be 2.620 secs and used this to work out the distance to the moon as 3.93 x 10^8 metres.

That's not bad given that the actual distance varies between 3.63 and 4.05 x10^8 metres.

The students then went on to measure the eccentricity of the moon's orbit using conversations recorded during the Apollo 17 mission, which was on the lunar surface for 300 hours.

They even estimated their errors using the Moon's ephemerides. Likely errors include delays caused by electronics and the time it took for the signals to be routed to the various antennae around the world that NASA used for communications.

Not bad for a group of 14-19 year olds.

Ref: arxiv.org/abs/0903.3367: Echoes From The Moon