“A Lesson in How Science Works”?

Full moon

How science is not supposed to work

A new model for the Moon’s formation is claimed to advance our understanding of the past, and to be “a lesson in how science works.” But the actual lesson being taught is quite different.

First, some background. Among secular astronomers, the most widely-accepted model for the Moon’s origin is known as the giant impact hypothesis. Supposedly, about four billion years ago, a Mars-sized object crashed into the newly-formed Earth. The collision created a debris cloud around our planet; some of the debris fell back down, while the rest coalesced together in space and eventually formed into our Moon.

Despite its popularity, this has never been a good model. It requires a credibility-straining series of conditions that are just right. Also, it has always had problems fully explaining the Moon’s composition. There are other issues too.

Nevertheless, it has been the standard lunar origin model for several decades.

This might change soon, thanks to the work of planetary scientist Dr. Sarah Stewart. She was awarded a MacArthur Fellowship award (commonly called a “genius grant”) for a new model of lunar origins—a model which supposedly solves the problems of the giant impact hypothesis.

Her proposal still includes a giant impact, but she describes the post-collision debris cloud in a different way. In her model, the early Earth became a “synestia”: a giant bagel-shaped cloud of hot vaporized rock.

Here’s what she said about the giant impact hypothesis, and why she sought a different explanation for the Moon:

“Simulations showed that the moon should be made primarily out of the object that struck the proto-Earth. But the Apollo mission found that the moon is practically a twin of the Earth, particularly its mantle, in major elements and in isotopic ratios. The different weight elements are like fingerprints, present in the same abundances. Every single small asteroid and planet in the solar system has a different fingerprint, except the Earth and the moon. So the giant impact hypothesis was wrong.” [emphasis added]

The precise match of the isotopic “fingerprints” for the Earth and Moon has been known since the late 1990s. The giant impact model has always had serious problems since it was first proposed in the 1970s, but this was discovery twenty years ago (which has been confirmed and strengthened by further studies since then) was understood by many to be the final nail in the coffin for this hypothesis.

As Dr. Stewart said, scientists have known for many years that the hypothesis is wrong. Nevertheless, it is still being taught as fact today.

Why? Because, as she explained…


image credit: Ganapathy Kumar