Ten things you may not know about the Moon
1. The Moon formed out of the Earth
Scientists now think that the Moon was formed when a Mars-sized object crashed into our planet about 4.5 billion years ago. The collision was so large that a huge spray of material was ejected into space. The orbiting ring of debris gathered itself into a sphere, and formed the Moon. How do we know that this is how the Moon probably formed? The Moon seems to be much less dense than the Earth and lacks a lot of iron in its core. Scientists think that the Moon is made up of the upper crust material, which has mostly lower density, than the composition of the Earth.
2. The Moon only shows one face to the Earth
Although the Moon used to rotate in the sky compared to our point of view, it has been slowing down billions of years. And at some point in the distant past it just stopped turning from our perspective. The Earth’s gravity holds the Moon in orbit, but it pulls differently at various parts of the Moon. Over a long period, gravity slowed down the Moon’s rotation so that it finally stopped, and always displayed one face to the Earth. A similar situation has happened with most of the large moons in the Solar System. In fact, in the case of Pluto and Charon, but objects are tidally locked to each other, so they present only one face to the other.
3. The Moon is slowly drifting away
Although the orbit of the Moon seems nice and stable, our only natural satellite is actually drifting away from us at a rate of 4 centimeters a year. This is happening because of the conservation of momentum in the orbit of the Earth. In about 50 billion years from now, the Moon will stop moving away from us. It will settle into a stable orbit, taking about 47 days to go around the Earth (it takes 27.3 days today). At that point, the Earth and the Moon will be tidally locked to each other. It will look like the Moon is always in the same spot in the sky. Of course, the Sun is expected to consume the Earth in about 5 billion years, so this event may not happen.
4. The Moon looks the same size as the Sun
This is an amazing coincidence. From our perspective here on Earth, but the Moon and the Sun look approximately the same size in the sky. Of course, the Sun is much much bigger than the Moon. The Sun happens to be 400 times larger than the Moon, but it’s also 400 times further away. This wasn’t always the case. Billions of years ago, the Moon was much closer than the Sun, and would have looked larger in the sky. And the Moon is moving away from us, so in the distant future, the Moon will look much smaller than the Sun.
5. The Moon causes most of the tides… but not all
You might know that the tides on Earth are caused by the gravitational pull of the Moon. But it’s not the only thing pulling at the Earth’s water, the Sun is helping out too. This is why we get very high and low tides from time to time. When the gravity of the Moon and the Sun line up, we get the biggest and smallest tides. Did you know that the Moon is also pulling at the crust of the Earth causing it to bulge up? You actually move a few meters every time the Moon is overhead, but you just don’t notice.
6. Gravity on the Moon is only 17% of the Earth
Want an easy way to lose some weight? Take a trip to the Moon and stand on its surface. Since the pull of gravity on the Moon is only 17% the pull of gravity on the Earth, you’ll feel much lighter. Just imagine, if you weighed 100 kg on the Earth, you would feel like you only weighed 17 kg on Earth. You would be able to jump 6 times further and carry objects 6 times as heavy. In fact, you had wings attached to your arms, you could even fly around inside a dome on the Moon under just your own muscle power.
7. The official name for the Moon is… the Moon
I know it’s kind of confusing, but the only real name for the Earth’s Moon is “the Moon”. When the Moon was given its name, astronomers didn’t know that there were moons orbiting other planets. And so they just called it the Moon. Now that we know there are other moons, it all comes down to the capitalization. The Earth’s moon is referred as “the Moon”, with a capital “M”. Other moons are given a lowercase “m” to show the difference.
8. The Moon is the 5th largest natural satellite in the Solar System
You might think that the Moon is the largest satellite in the Solar System. I mean look at it, it’s huge! But there are actually larger moons in the Solar System. The largest moon is Jupiter’s Ganymede (5,262 km), followed by Saturn’s Titan, Jupiter’s Callisto, Jupiter’s Io, and finally, the Earth’s Moon with a mean diameter of 3475 km.
9. Only 12 people have ever stepped onto the surface of the Moon
Only a tiny group of astronauts have ever set foot on the surface of the Moon. These were the astronauts on board the Apollo missions going from 1969 to 1972. The first person to ever walk on the Moon was Neil Armstrong. And the last person on the Moon was Gene Cernan, who followed his partner Jack Schmitt into the lunar lander on December 14, 1972.
10. And we’re going back to the Moon
NASA has been given the mission to return humans to the Moon, and set up a permanent research station. At the time of this writing, astronauts are expected to set foot on the surface of the Moon again in 2019.
GIF by 40 Licks
The Natural Satellite
(Source: Flickr / shoulderops)
Black & White Storytelling Silhouettes by Hengki Lee
Saturn’s moon Mimas peeps out from behind the larger moon Dione in this view from the Cassini spacecraft. Mimas (246 miles, or 396 kilometers across) is near the bottom center of the image. Saturn’s rings are also visible in the top right.
This view looks toward the anti-Saturn side of Dione (698 miles, or 1,123 kilometers across). North on Dione is up and rotated 20 degrees to the right. This view looks toward the northern, sunlit side of the rings from just above the ringplane.
The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Dec. 12, 2011. The view was obtained at a distance of approximately 377,000 miles (606,000 kilometers) from Mimas. The view was obtained at a distance of approximately 56,000 miles (91,000 kilometers) from Dione and at a Sun-Dione-spacecraft, or phase, angle of 42 degrees. Image scale is 1,773 feet (541 meters) per pixel on Dione.
Image: NASA/JPL-Caltech/Space Science Institute [high-resolution]
Waxing Gibbous Moon
New Theory: A “Hit and Run” Accident Created Our Moon
How did Earth get its own Moon? For decades, the most popular origin story has been the “Big Splat” theory, which says an object the size of Mars impacted the Earthmore than three billion years ago, flinging material into space which became the Moon.
Refractions by Maianer
The moon approached within 357,000 km (222,000 mi) of Earth, in what is scientifically known as a perigee-syzygy of the Earth-Moon-Sun system (perigee: closest point of an elliptical orbit; syzygy: straight line made of three bodies in a gravitational system). [24 photos]
What if we had a planet instead of a Moon?
Our moon is a pretty big object. It’s big enough to be a respectable planet in its own right, if it were orbiting the sun instead of the Earth. (Actually, it is orbiting the sun in a nearly perfectly circular orbit, that the Earth only slightly perturbs… but that’s a topic for another day.) The Moon is a quarter the diameter of the Earth. Only Pluto has a satellite that is larger, in proportion to the size of the planet it orbits.
But what if the Moon were size of Mars, instead? It would like the picture above. Check out how some of the other planets of the Solar System would look in our sky, if they took the Moon’s place.
At a distance of about 240,000 miles, the Moon occupies a space in the night sky about half a degree wide. By sheer coincidence, this is almost exactly the same size the sun appears, which is why we occasionally get total solar eclipses. (We don’t get a total eclipse every time the Moon passes in front of the sun because the Moon is sometimes a little closer to the Earth and sometimes a little further away, so it will cover more or less of the sun during any eclipse.)
But it’s interesting to imagine what the night sky might look like if one of the Solar System’s planets were to replace our moon. (We’d have to ignore things like tides and gravitation, but that’s the advantage of doing things in the mind’s eye.) So what would we see if we were to replace the moon with Mars? The red planet is almost exactly twice the size of the Moon, so it would appear twice as big in the Earth’s sky. It would be easy to see with the naked eye details on the surface of the planet that were previously visible only through telescopes. You could watch the ice caps grow and shrink during the changing seasons, see dust storms form and move across the planet and make out features like Vallis Marineris and Olympus Mons.
Space Station Moon Dash
The right place at the right time… that’s all it took (along with some great camera skills!) for a NASA photographer at Johnson Space Center in Houston to capture some fantastic photos of the International Space Station (ISS) passing across the face of the moon!
The image above, made from a series of photos captured on Jan. 4, shows the ISS making its trip across the sky. This time its voyage took it directly across a waxing gibbous moon.
The ISS is currently about 248 nautical miles above the Earth, traveling at a staggering 17,000 mph (28,163 km/hr). At that speed it circles the globe 16 times a day. When it passes overhead it can be the brightest manmade object in the sky, often outshining commercial aircraft and even planets!
You can find out when the ISS will be over your location here.
Airplane transit in front of the Moon
If Jupiter Was the Same Distance as the Moon?
Redditor jb2386 created this mind-blowing image which shows what Jupiter would look like if it was the same distance away from the Earth as the moon. He figured it out by taking a source picture that had the moon in it, used the correct scale of the Moon to Jupiter and then placed the readjusted size of Jupiter in the image. Because of the planet’s enormous size, we are only seeing about a quarter of Jupiter in the frame! Unfortunately, as cool as it looks, it appears we’d be goners if this actually happened in real life.
First Quarter Moon
The Moon appeared half illuminated when the photographer snapped this image. We call this moment in our lone natural satellite’s orbit “First Quarter” because the Moon is one-fourth of the way through its phases, which traditionally start at New Moon. It also marks the point where, from our perspective on Earth, we see precisely one-fourth of the Moon’s total surface. (3.2-inch Stellarvue 80mm apochromatic refractor at f/4.8, Celestron NexImage 5 CMOS camera with Gain set at 4, 1/90-second exposure, taken June 26, 2012, from Guelph, Ontario, Canada)