## Sunday, July 20, 2008

### One Giant Leap...

39 years ago today humans first walked on the Moon. For most of us born since then, it is hard to imagine billions of people watching the event together. Despite the Cold War and protests, for one brief moment the human race was as one. "We Came in Peace For All Mankind," the plaque says. Could it happen again?

The 1-minute video also mentions the Lunar Laser Ranging Experiment. This device, simple as a bicycle reflector, was a giant leap for physics. It allowed accurate measure of the Moon's distance and more checks on General Relativity. LLRE also gave one more indication that the speed of light is slowing down.

In 1969 the human race was even more divided than today. Nations were divided by an Iron Curtain and Third World. Personal computers and phones were science fiction. Colour television was reserved for a few. Today's blogs and internet allow us to gather in small communities. However, technology also allows the whole globe to witness a single event. Within 11 years the world will again see humans walk the Moon. Can the human race again unite behind one moment?

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nige said...

Fantastic video. Thank you!

3:33 AM
robert d said...

In a prior comment on the LLRE experiment, 7/11/08, nige wrote

"This is slightly different from your calculation of 0.935 cm/yr, probably because we took different figures for the Earth-Moon distance. Some sources give the mean distance from the centre of the Moon to the centre of the Earth, others subtract from that the Moon's radius and the Earth's radius. The exact distance depends on where on the Moon the Apollo astronauts left the reflecting mirror in 1969, and where on the Earth the laser pulses are fired from.

It's interesting that there are several pieces of evidence that you have for the velocity of light falling inversely with the cube root of the age of universe."

I was perplexed by why nige assigned a value of 13,700,000,000 Earth years to t. This may be a proxy for the age of the universe, but I would think that a value of t of 4,700,000,000 Earth years would be a more appropriate estimate for a measure of a relationship between the Earth and the Moon. Given that the Moon is actually younger than the Earth the estimate of t would actually be even smaller.

As an aside. How are you measuring the age of the Universe independent of the speed of light?

d

8:38 PM
L. Riofrio said...

Thanks, nige.

For robert: the speed of light changes as a function of t, age of the Universe, estimated as 13.7 Byr. That estimate is given by the WMAP experiment, and is subject to adjustment.

You can also find t if you know the average density \rho, since \rho = (6 \pi G t^2)^{-1}

10:00 PM
LCc 03 said...
3:31 PM