Sun
Mercury
Venus
Earth
Moon
Mars
Jupiter
Europa
Io
Saturn
Titan
Uranus
Miranda
Neptune
Pluto
Did you know...
...that North America is actually closer to the Sun in Winter than in Summer? This is due to the eccentricity of Earth's orbit.
...that Earth is the only planet not named after a god?
...that the maximum possible duration of an eclipse is 7 minutes and 31 seconds (when the observer is land-based and stationary)?
...that Earth is the densest planet in the solar system?
...that since 1959, more than 6,000 pieces of "space junk" have fallen out of orbit? Many of these have hit Earth's surface.
...that two objects in the twentieth century have hit Earth's surface with enough force to destroy a medium-sized city? Luckily, both landed in sparsely-populated Siberia.
| equatorial radius: | | 6.38×103 km |
| polar radius: | 6.36×103 km | ||
| mass: | 5.98×1024 kg | ||
| density: | 5.52 g/cm3 | ||
| average distance from sun: | 1.495×108 km | ||
| orbital eccentricity: | 0.017 | ||
| tilt of axis to orbit: | 23.45° | ||
| orbital inclination to ecliptic: | 0° | ||
| length of day: | 23:93 (hr:min) | ||
| length of year: | 1 yr | ||
| temperature: | -89.6° C to 58° C | ||
| atmospheric pressure: | 1 atm | ||
| atmospheric composition: | N2 (78%), O2 (21%), Ar (1%) | ||
| satellites: | Moon |
The largest of the inner planets, Earth is a gorgeous sight from space. Its swirling white clouds, green and brown continents, and blue oceans make it a sight to behold. Earth is the only planet we know of that has both solid and liquid on its surface. Our planet isn't the only one to have polar ice caps, but the caps on other planets are often made of other things, like the "dry ice" caps on Mars.
Earth's surface is constantly changing due to the weather and erosion. The visible surface is part of Earth's crust. Oceans cover about 70 percent of the Earth's surface area. Beneath the crust are the upper and lower mantle, and the outer and inner core. The crust is rich in granite, basalt, and aluminum, the mantle is mostly magnesium and iron, and the core is made of molten nickel and iron oxides. Earth's crust is small compared to the layers underneath; the mantle is the largest part of the Earth, and the core makes up most of the rest. The theory of plate tectonics says that the continents are part of huge plates of rock which float on the molten mantle underneath. If two of the plates collide, the smaller of the two is often thrust under the larger. This process is called subduction. Also, when lava from volcanic eruptions spreads out over the ocean floor, it alters the ocean level of the floor in a process called sea-floor spreading.
Earth is the only planet known to have intelligent life, and this is largely thanks to Earth's atmosphere which is just right for supporting life as we know it for several reasons. Nitrogen makes up about 80 percent of the atmosphere's volume, and oxygen makes up most of the rest. Traces of carbon dioxide, water vapor, and ozone are also present. It turns out that those little traces of stuff are very important. They absorb infrared radiation and change atmospheric temperatures. The atmosphere is pretty uniform throughout the planet, except at high altitudes, where varies somewhat. The amount of water vapor is not uniform around the planet, though. Places closer to oceans and locations with certain temperatures have more water vapor.
About 20 km above Earth's surface exists a concentration of the chemical ozone (O3). This "ozone layer" is formed when the sun's ultraviolet radiation breaks apart oxygen. Certain chemicals such as the dreaded chloroflourocarbons (CFCs) prevent this reaction from taking place, causing more UV radiation to shine down on the surface instead of breaking apart oxygen.
The Earth's poles are magnetic, as anyone who's ever used a compass can tell you. But you might not know that the magnetic field, or "magnetosphere," the poles create holds millions of tiny charged particles out in space, spiraling around in a radiation field. Earth also has a layer of electrons called the ionosphere, which are mostly unimportant except that they can interfere with radio signals from satellites or from radiowave astronomers.
Earth is often considered by astronomers to be in a binary planetary system with the Moon. The Moon isn't as big as Earth, of course (about one quarter the size and one eightieth the mass). However, when you consider that most moons are about a thousandth the size of the planets they orbit, it appears gigantic. The Moon is the only place humans have set foot other than Earth.
 | Earth from space |
 | Earth rising above the Moon |
The Planet Earth - Info about Earth
Mission to Planet Earth Fact Sheet - NASA site
Planet Earth - Lots of info
* Photo credit - NSSDC Photo Gallery
