Earth

Image of Earth from Satellite

Earth is the planet we live on.

It is the third farthest planet from the sun at 149 million kilometers (92 million miles) away.

Gravity

We can compare the gravity on Earth to other planets.

Example: A person weighing 45 kilograms (100 pounds) on Earth, only weighs 17 kilograms (37 pounds) on Mercury.

This is because Mercury is less massive than Earth. Gravity is the force that pulls matter together, and the larger the mass the larger the gravitational pull.

 

Water

Earth is the only planet not named after a god or goddess, but it makes up for that by having water!

Earth is the only planet to have liquid water on its surface, and it has a lot of it. About 70% of the planet is covered in water.

  • But 97% of that water is salt water.
  • And 2% is ice from the North and South Poles. We could drink the water at the Poles, but we can't get to it easily.
  • So of all the water on Earth, only 1% is fresh water that is used for drinking.

Think about this, if Earth's water were a bag of 100 M&M's:

  • 97 pieces would be extremely salty and not fit for you to eat,
  • 2 pieces are edible, but they are stuck in the bag where you can't get them,
  • there is only 1 piece of candy left in the bag that you can eat.

It's amazing how much water there is left to drink on Earth even at 1%.

 

Temperature

The temperatures on Earth vary from a cold -89° C (-128.5° F) to a hot 57° C (134° F). The coldest temperature ever recorded on Earth occurred on July 21, 1983 at a research station in Vostok, Antarctica. The hottest place on Earth is in Death Valley, California, whose 57° C temperature has held the record since 1913.

Structure

The Earth's core is made of iron and sulfur and is a molten mass in constant motion.

The outer core is molten while the inner core is solid iron.

The inner and outer core rotate in the same direction, but the inner core at a slightly slower pace.

The heat from the inner core forces convection to the outer core which creates our magnetic field.

The mantle, or middle section, contains mostly rocks made of magnesium and iron. Because these rocks are so close to the molten area they heat up and rise towards the crust, the top layer.

When the mantle starts pushing upward, volcanoes start erupting.

The crust of the Earth is made of:

  • Oxygen 46%
  • Silicon 27%
  • Aluminum 8.2%
  • Iron 6.3%
  • Calcium 5.0%
  • Magnesium 2.9%
  • Sodium 2.3%
  • Potassium 1.5%
  • Titanium 0.6%
  • Carbon 0.2%
  • plus other elements.

The crust sits on top of the mantle and is divided into enormous, ever moving plates. Earthquakes are caused by the plates moving against each other.

 

Moon

Earth has its own moon.

Because of the lack of iron in its core, scientists believe that the moon was once part of the Earth.

The theory is that a meteor hit Earth very hard over 4 billion years ago, and all the matter that sprayed up into space later formed into a sphere, which is now the Moon.

Movement

When rotating, the Earth spins on its axis, which is an imaginary line that goes through the Earth's center.

It spins at an angle, which is why the amount of sun an area receives changes throughout the year.

 

Example: if you live in Ohio, the sun does not set in June until about 9 PM, but in January, the sun sets around 6 PM.

This is because the axis is pointed towards the sun during the summer and away from the sun in the winter.

The earth rotates once every 24 hours, which gives us our day.

The Earth follows an orbit around the sun, which takes about 365 days, one Earth year, to complete.

The earth rotates at 1,667 kilometers (1,036 miles) per hour,

The Earth orbits around the sun at 30 kilometers per second, which is equal to 107,000 km (67,000 miles) per hour.

Why are we not holding on to our furniture to stand upright at speeds like this?

Because the speeds are almost constant! If you are driving in a car that is going the same speed for a period of time, you normally do not notice you are moving, it is only when the speed changes, or the vehicle turns do you feel the change in velocity. If the earth were to suddenly slow down, or start moving in the opposite direction, you would definitely notice.

 


Different views of our planet.

Atmosphere

The Earth's atmosphere is made up of 78% nitrogen, 21% oxygen, and 1% of other various gases.

Not surprisingly, Earth is the only planet human beings can live on, at least without special suits or sealed living spaces.

Humans breathe in about 8 liters of oxygen per minute, which equals about 11,000 liters of air per day.

Since the air we breathe in is about 21% oxygen, and we exhale about 15% oxygen, human beings use about 550 liters of pure oxygen a day. If it was in soda pop bottles, this is nearly 300 two liter bottles per day of oxygen. Try taking that with you as you walk around!

 


Mercury, Venus, Earth (3rd from the Sun), Mars,
the Gas Giants Jupiter, Saturn, Uranus and Neptune

(Images courtesy NASA.)