The Moon: Earth's Sneezeguard

Mandi Walls writes "SF Gate is running an article about looking on the moon for pieces of Earth that may have been knocked into space by collisions with asteroids, etc. The article claims the guys responsible for the idea came up with it while stuck in traffic. They were probably digging for change for a toll in the seats."

Comments

Isn't the moon itself a piece of the earth?

[T.Hobbes]

I had heard in SciAm awhile ago that the moon was created when a mars-sized asteroid hit a young (~4bn yrs), molten earth. This sent a v. large mass of rock into orbit which coalesced into what is now the moon.

In fact, after a little searching I found this at NASA:

How did the Moon come to be? The leading theory is that a Mars-sized body once hit Earth and the resulting debris (from both Earth and the impacting body) accumulated to form the Moon. Scientists believe that the Moon was formed approximately 4.5 billion years ago (the age of the oldest collected lunar rocks). When the Moon formed, its outer layers melted under very high temperatures, forming the lunar crust, probably from a global "magma ocean."

A few more links: Perty image and more detailed explanation; a google search on the topic.

Re:Isn't the moon itself a piece of the earth?

[T.Hobbes]

Lab error? This paper, and the site that it's on, give a good rebuttal; specifically,

"As magmas move through the crust towards the surface or as lava flows over the Earth's surface, they may pickup chunks of surrounding rocks. Sometimes, the magmas and lavas are not hot enough to melt the captured rocks. Once the molten rock solidifies, the plucked rocks remain trapped in the igneous matrix. These trapped rocks are called xenoliths. If the trapped materials are individual minerals, they are called xenocrysts.

Xenoliths, zoned phenocrysts, and xenocrysts (like metamorphic and weathering features) are often easily identified under the microscope and sometimes even in the field. In some cases, a geologist may be interested in dating xenoliths, zoned phenocrysts, or the xenocrysts. However, obviously, if the geologist is interested in dating the younger matrix, he/she will look for and avoid any xenoliths, zoned phenocrysts or xenocrysts. While mainstream geologists know how to avoid xenoliths, zoned phenocrysts, and xenocrysts when dating igneous rocks, creationist Steve Austin apparently was not careful to avoid them when he conducted his "research" at Mt. St. Helens or the Grand Canyon, see " A Criticism of the ICR's Grand Canyon Dating Project by Chris Stassen and compare with Excess Argon within Mineral Concentrates from the New Dacite Lava Dome at Mt. St. Helens Volcano, by Steven Austin. In his Mt. St. Helen's study, Austin collected what he thought was a freshly solidified dacite. He removed the gabbro xenoliths, but there's no mention if he found and removed any lighter colored, less obvious xenoliths, such as andesites or quartz diorites. Austin states that xenoliths of gabbro, quartz diorite, basalt, and andesite are common at the Mt. St. Helen site."

The study by Austin the author, a Dr. Henke, is referring to is one which claims impossibly old dates for fresh dacite.

We could go on for a long time, but I would simply say that science is self-correcting: it is a field which encourages criticism and revision, so long as the criticism is valid and demonstrable. No good scientist would ever claim to any perfection in his or her work. A scientific theory is only valid so long as it has been demonstrated in experiment and has not been disproven by other experiments. The reason why I have such a hard time accepting what you're saying is because, so far as I can tell, it has not stood up to peer review.

Archimedes, not Newton

[T.Hobbes]

You're thinking of Archemedies. From school-for-champions.com(link),

Story of Archimedes

The ancient Greek philosopher and scientist, Archimedes was asked by the king to determine if a gold statue he had was 100% gold. Since it was an odd shape, Archimedes could not simply measure the volume to determine the object's density and thus its composition.

Archimedes decided to take a hot bath, to help him think about this problem. When he got in the bath tub, he noticed the water rise. This clue led to the discovery that an object will displace its volume when immersed in a liquid. When Archimedes realized that objects displace their volume in water, he excitedly jumped out of the tub and ran down the streets shouting, "Eureka! Eureka!" which means, "I have found it!" Unfortunately, he didn't notice that he forgot to put his clothes on! When Archimedes put the statue in a container full of water, he measured the volume of the overflow to determine the volume of the statue. Then he measured the weight of the statue and compared its density with the known density of pure gold. He discovered that the statue was not made of pure gold, rather it contained some other metal, like lead.