# Come visit earth!

## what is the definition of earth?

noun

1.

(often initial capital letter) the planet third in order from the sun, having an equatorial diameter of 7926 miles (12,755 km) and a polar diameter of 7900 miles (12,714 km), a mean distance from the sun of 92.9 million miles (149.6 million km), and a period of revolution of 365.26 days, and having one satellite.

## some quick facts about earth.

• The planet is 3,959 mi in radius.
• Earth has one moon and it is called moon.
• Earth has some unique features like water and plate tectonics.

## What causes the seasons?

The seasons are caused by the tilt of the Earth's rotational axis away or toward the sun as it travels through its year-long path around the sun. The Earth has a tilt of 23.5 degrees relative to the "ecliptic plane" (the imaginary surface formed by it's almost-circular path around the sun).

## what is rotation and revolution?

Rotation-is a circular movement of an object around a center (or point) of rotation . A three-dimensional object always rotates around an imaginary line called a rotation axis. If the axis passes through the body's center of mass, the body is said to rotate upon itself, or spin. A rotation about an external point, example: the Earth about the Sun, is called a revolution or orbital revolution, typically when it is produced by gravity.

Credit: https://en.wikipedia.org/wiki/Rotation

Revolution-rotation is when a planet or moon turns all the way around or spins on its axis one time. The axis of rotation is an imaginary line going from the north pole to the south pole. When a planet or moon travels once around an object this is considered a revolution.

Credit: http://utahscience.oremjr.alpine.k12.ut.us/sciber06/6th/moon/html/rotate.htm

## how do we get our energy from the sun?

The Sun produces energy by the nuclear fusion of hydrogen into helium in its core. What that means is that, since there is a huge amount of hydrogen in the core, these atoms stick together and fuse into a helium atom. This energy is then radiated out from the core and moves across the solar system. It is not enough to just answer the question, so here is a breakdown of how the energy is transferred from the core to the Earth and the other objects in our solar system.

## why are all planets and moons and stars round or spherical?

The reason planets appear spherical is because gravity compresses the planet into a shape that most evenly distributes the gravitational force among the planet’s mass.

Credit: http://clarkplanetarium.org/why-are-planets-spherical/

## what is a light year?

A light-year is a unit of distance. It is the distance that light can travel in one year. Light moves at a velocity of about 300,000 kilometers (km) each second. So in one year, it can travel about 10 trillion km. More precisely, one light-year is equal to 9,500,000,000,000 kilometers.

Credit: http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html

## what should you bring with you?

Sunglasses if you want to go somewhere sunny and also sunscreen. If you are going cold bring a coat of varying thickness depending on how cold it is where you are going.

## how will you get here?

One of our certified space pilots will fly his ship out to you and pick you up and bring you home.