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Zidbits – Learn something new everyday! | July 28, 2014

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Everything You Wanted To Know About The Moon

Everything You Wanted To Know About The Moon

Today, we’re going to explore the Moon. Its environment, its creation, our exploration and why it’s one of a kind (at least in our solar system). The Moon is actually quite special. Today we’ll find out why.

Lot’s Of Moons

Over 150 moons populate our solar system. The majority of moons orbit the gas giants. 13 around Neptune, 48 around Saturn and a staggering 62 orbit Jupiter. Earth has only one moon. But what an amazing moon it is. It’s certainly not the largest moon in our solar system (Saturn’s Titan is 2x the size of our Moon), but it is the largest moon in relation to the host planet it orbits – roughly a quarter its size. Because of the size relation, some astronomers refer to the Earth/Moon system as a “double planet system”.

The Facts

moon landingThe distance from the Earth to the Moon is 234,000 miles. This distance is so great, that if you were to drive a car at 65 MPH non-stop, it would take you approximately 4 months, 28 days and 8 hours to reach the moon. For comparison, it would only take a person 1 day, 14 hours to drive from NY to LA at 65 MPH non-stop.

The Moon is 2,160 miles in diameter. It’s roughly 1/4 the size of the Earth. Because the Moon is phase locked with the Earth (one side always faces the Earth), one full day on the moon is 27.3 Earth days. Thanks to smaller size and lower mass, it only has 1/6th the gravity of the Earth.

Because the Moon has no atmosphere, it exists in the vacuum of space. This means that the sky is always black because there are no molecules to scatter the Sun’s light and that the temperature on the Moon can vary wildly. The Moon can reach 270 degrees F in the sunlight and swing to -240 F below at night.

Earth To The Moon – Relative

Earth to Moon

The Moon is also incredibly dusty. Layered with a dust (regolith) so fine and sticky, the Apollo astronauts had trouble with it every time they went to the Moon. This dust was created by micro-meteorite impacts. The Earth doesn’t experiences these impacts because the meteorites burn up in our thick atmosphere before reaching the ground. On the atmosphere-less moon however, it’s like a 4 billion year old continuously grinding gravel pit.

The Man On The Moon

man on the moon
The illusion of ‘The Man On The Moon’ was created from similar impacts orders of magnitude larger. Rogue comets and asteroids smacked into the moon. Some leaving craters 700 miles across. Lava eventually filled the crater’s basins that these impacts created.

When the lava and magma cooled, it was darker than the surrounding material. These basin’s are called ‘maria’ – or ‘seas’ in Latin and created the features we recognize.

The Tides

Thanks to the gravitational pull of the Moon, it has a significant impact on our tides. As the Moon orbits the Earth, it pulls the water towards it. The opposite side experiences an opposite pull – similar to that of an American football.

An extreme example of this tidal change can be seen in Canada’s Bay of Fundy where the water level from high tide to low tide drops an amazing 55 feet.

Bay Of Fundy Tide Extremes

Low – High Tide Extremes

The Moon Is Running Away?

The first person to suggest that the Moon was getting further away from the Earth was Charles Darwin’s son, George Darwin.orbit In 1878, George introduced his “fission” hypothesis of the genesis of the moon. While his fission hypothesis was proven incorrect, his extensive knowledge and analysis of tides led him to the correct conclusion that our Moon was indeed moving away from the Earth. His conclusion was not proved until 95 years later when Apollo astronauts put mirrors on the moon for researchers to bounce lasers off of. They found that the Moon was indeed moving away from the Earth at approximately 3.5 cm a year (1 1/2 inch).

Don’t fret though, after a few billion years, the Moon’s orbit will slow and stabilize – being permanently locked with the Earth’s. Though by that time, our Sun will have already turned into a red giant and baked our planet to a crisp.

Why Is Our Moon Special?

The Moon stabilizes the Earth’s climate by way of keeping the Earth’s tilt stable. If our tilt wasn’t stable, the North Pole would have extreme variations in location.solar eclipse Because our North Pole remains somewhat static in its location, it allows the Earth to continuously experience the 4 seasons we know and love. Without our Moon, or if we had a smaller moon, we would not have our 4 seasons. Life as we know it, would be completely different.

Our Moon is also unique in its size for its location. The Sun is 400 times the Moon’s diameter and it just so happens that it is also 400 times as far away. That amazing coincidence means the Sun and Moon appear to be the same size when viewed from the surface of Earth. A total solar eclipse, when the Moon is between the Earth and Sun, blocks the bright light from the Sun’s photosphere allowing us to see the faint glow from the corona, the Sun’s outer atmosphere. These types of eclipses happen nowhere else in our solar system.

Origins Of The Moon

moon origin

Supercomputer simulations show that our moon was created by a Mars sized object impacting the Earth. The Earth absorbed much of the other celestial object, including its heavier elements (like iron). The lighter debris left over coalesced into the Moon. This theory is known as the ‘Giant Impact Theory’. This impact was so massive, it started the Earth spinning, gave us our 24 hour days and created the Moon.

Comments

  1. larry scott

    I am not sure why this article cites the moon as roughly 1/4 the size of the earth. It is 1/4 the diameter, or radius. But that returns only about 2% the size of the earth by volume. The moon’s composition is less dense making is even smaller (compared to earth) by mass. So, in the interest of science, 1/4 “size” is very misleading. Less than 2% is more like it. A moon at 1/4 the size of the earth our mutual orbit about the barycenter would be very different than we experience today. Even in cross sectional area the earth is 13.5x the cross sectional area of the moon. So, please add an example of the math of volumes of each. So, wouldn’t a moon of 1/4 the volume of the earth be about 6430 miles in diameter?

    (The Myth Busters said that “a 4 inch bore cannon is 2x the size of a 2 inch cannon”. Except that a 4″ cannon ball is 8x more massive than a 2 inch cannon ball.)

    Edit: correction: a moon of 1/4 the size of the earth (by volume) would have diameter of 4990 miles.

  2. If it’s nighttime on the moon, would you consider it an eclipse?

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