Difficulties
This lunar origin hypothesis has some difficulties that have yet to be fully resolved. For example, the giant impact hypothesis implies that a surface magma ocean would have formed following the impact. Yet there is no evidence that the Earth ever had such a magma ocean and it is likely there exists material that has never been processed by a magma ocean.
Read more about this topic: Giant Impact Hypothesis
Famous quotes containing the word difficulties:
“Let us consider that we are all partially insane. It will explain us to each other; it will unriddle many riddles; it will make clear and simple many things which are involved in haunting and harassing difficulties and obscurities now.”
—Mark Twain [Samuel Langhorne Clemens] (1835–1910)
“It appeared that he had once represented his tribe at Augusta, and also once at Washington, where he had met some Western chiefs. He had been consulted at Augusta, and gave advice, which he said was followed, respecting the eastern boundary of Maine, as determined by highlands and streams, at the time of the difficulties on that side. He was employed with the surveyors on the line. Also he called on Daniel Webster in Boston, at the time of his Bunker Hill oration.”
—Henry David Thoreau (1817–1862)
“Our achievements speak for themselves. What we have to keep track of are our failures, discouragements, and doubts. We tend to forget the past difficulties, the many false starts, and the painful groping. We see our past achievements as the end result of a clean forward thrust, and our present difficulties as signs of decline and decay.”
—Eric Hoffer (1902–1983)