SOME FACTS ABOUT EARTH

1.

It's not a perfect sphere. As Earth spins, gravity points toward the center of our planet (assuming for explanation's sake that Earth is a perfect sphere), and a centrifugal force pushes outward. But since this gravity-opposing force acts perpendicular to the axis of Earth, and Earth's axis is tilted, centrifugal force at the equator is not exactly opposed to gravity. This imbalance adds up at the equator, where gravity pushes extra masses of water and earth into a bulge, or "spare tire" around our planet.

2. 

Mother Earth has a generous waistline: At the equator, the circumference of the globe is 24,901 miles (40,075 kilometers).

3

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You may feel like you're standing still, but you're actually moving — fast. Depending on where you are on the globe, you could be spinning through space at just over 1,000 miles per hour. People on the equator move the fastest, while someone standing on the North or South pole would be perfectly still. (Imagine a basketball spinning on your finger. A random point on the ball's equator has farther to go in a single spin as a point near your finger. Thus, the point on the equator is moving faster.)

(Photo shown here, a true-color image taken on May 5, 2000, by an instrument aboard NASA's Terra spacecraft, over the North Pole, with sea ice shown in white and open water in black.)

4.

 the Earth isn't just spinning: It's also moving around the sun at 67,000 miles (107,826 km) per hour.

5.

Researchers calculate the age of the Earth by dating both the oldest rocks on the planet and meteorites that have been discovered on Earth (meteorites and Earth formed at the same time, when the solar system was forming). Their findings? Earth is about 4.54 billion years old.

(Photo shown here, what may be the oldest known rocks on Earth, called the Nuvvuagittuq Belt on the coast of the Hudson Bay in Northern Quebec, and dating back to 4.28 billion years ago, scientists estimate.)

6.

The ground you're walking on is recycled. Earth's rock cycle transforms igneous rocks to sedimentary rocks to metamorphic rocks and back again. The cycle isn’t a perfect circle, but the basics work like this: Magma from deep in the Earth emerges and hardens into rock (that's the igneous part). Tectonic processes uplift that rock to the surface, where erosion shaves bits off. These tiny fragments get deposited and buried, and the pressure from above compacts them into sedimentary rocks such as sandstone. If sedimentary rocks get buried even deeper, they "cook" into metamorphic rocks under lots of pressure and heat. Along the way, of course, sedimentary rocks can be re-eroded or metamorphic rocks re-uplifted. But if metamorphic rocks get caught in a subduction zone where one piece of crust is pushing under another, they may find themselves transformed back into magma.

7. Largest Earthquake

As of 2011, the largest earthquake to shake the United States was a magnitude-9.2 temblor that struck Prince William Sound, Alaska, on Good Friday, March 28, 1964. (Photos shows the Four Seasons Apartments in Anchorage, a six-story lift-slab reinforced concrete building, which cracked to the ground during the quake.) And the world's largest earthquake was a magnitude 9.5 in Chile on May 22, 1960, according to the U.S. Geological Survey (USGS).

8. Hot Spot

The fiery award for Earth's hottest spot goes to El Azizia, Libya, where temperature records from weather stations reveal it hit 136 degrees Fahrenheit (57.8 degrees Celsius) on Setp. 13, 1922, according to NASA Earth Observatory. There have likely been hotter locations beyond the network of weather stations. (The image was created from data collected by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Aqua satellite.)

9.Its Skies Dazzle With Dancing Lights

Auroras occur when charged particles from the sun are funneled toward Earth by the planet's magnetic field and collide with the upper atmosphere near the poles. They are more active when the sun's activity peaks during its 11-year solar weather cycle.

The southern lights, also called aurora australis, are seen less often than aurora borealis, the northern lights, because few people brave Antarctica's dark, freezing winters. Shown here, a 2008 image taken from Antarctica of the dazzling sky lights

10.Where Rocks Walk

Rocks can walk on Earth, at least they do at the pancake-flat lakebed called Racetrack Playa in Death Valley. There, a perfect storm can move rocks sometimes weighing tens or hundreds of pounds. Most likely, ice-encrusted rocks get inundated by meltwater from the hills above the playa, according to NASA researchers. When everything's nice and slick, a stiff breeze kicks up, and whoosh, the rock is off.