Question

Search online or your book for hypothesis' of "how did the Moon form". What is the evidence for each hypothesis?

Did it form at the same time as the Earth and in orbit like it is now?

Was the Moon ever closer to Earth?

In a million years, about how far away will the Moon be from Earth?

Answer 1

Theia or the Giant Impact Theory::

In this scenario, about 4.5 billion years ago during the birth of our solar system the cooling Earth was impacted by a planetesimal, or a planet-developing object, the size of Mars. The impact tore off a section of the Earth and made the surface molten again while the magma chunk that broke off from Earth and the remnants of the planetesimal cooled and formed the Moon as we know it today. Because Earth and the moon are so similar in composition, researchers have concluded that the impact must have occurred about 95 million years after the formation of the solar system, give or take 32 million years. (The solar system is roughly 4.6 billion years old.) Of course, all theories have challenges and this one is no exception.

The Moon is currently moving away from the Earth at about 3.8 centimeters per year, so 3.8 cm for 85 million years equals 323 million centimeters. Sounds like a lot, right? 323 million of just about anything seems like a lot. 323 million centimeters is 3,230,000 meters, or 3,230 kilometers. Or a little over 2,000 miles—which, coincidentally, is about the diameter of the Moon itself. Since the Moon is presently 240,000 miles from Earth, being 2000 miles closer to us in the past (about 0.8%) would not have made it perceptibly larger—let alone appearing as big as a cantaloupe!

• Average distance from Earth: 238,855 miles (384,400 km)
• Perigee (closest approach to Earth): 225,700 miles (363,300 km)
• Apogee (farthest distance from Earth): 252,000 miles away (405,500 km)