Learning through Science

Space and the Earth
By Mary Beth Lott

How far away is space?

Not very far.  Space begins when Earth’s air ends- about 480 km above Earth’s surface.  That’s where the lighter molecules in air escape Earth’s gravity and drift into space.  This region, however, is much higher than we could travel by plane.  It is about forty times higher than a jet can fly.

Where is Earth in space?

People used to think Earth was the center of the universe.  Today we know that Earth is just one of the nine planets that circle our Sun.  Our galaxy, the Milky Way, has billions of stars, and our Sun is just one of those stars.  There are billions of galaxies in our universe.

What’s so special about Earth?

Earth is the only planet where we know there is life.  The Earth is exactly the right distance from the Sun to have the right temperature for water to be kept in its three forms- liquid, ice, and vapor.  The Earth’s atmosphere gives us oxygen to breathe, protects us from the Sun’s harmful rays, and keeps our planet warm.  The placement of the Sun and Moon enable us to tell time on Earth.

“The Sun, Moon, and…planets were made for determining and preserving the numbers of time.”  Plato, Timaeus

Fun Fact:  Some stars get “married.”   Some stars are drawn together by gravity and spend their lives together.  About half of the stars in the sky are part of a pair of stars or group of stars.

            “We had the sky, up there, all speckled with stars, and we used to lay on our backs and look up at them, and discuss about whether they was made, or only just happened- Jim allowed they was made, but I allowed they happened….”  Mark Twain, Huckleberry Finn

Comprehension Questions

1. How far away is space?

2. How many galaxies are in our universe?

3. What are the three forms of water?

4.  The Sun’s atmosphere protects us and keeps us warm.  True or False?

5.  Stars are drawn together by ____________.

Deeper Thought Questions

1. Some scientists describe the earth as just a bit of dust in an obscure galaxy.  Does the earth have special significance?

2. Huckleberry Finn thought that the stars “just happened.”  In other words, he did not believe that anyone or anything had made the stars.  Jim thought that the stars had been made.  Which do you believe?

Something to do:

1. Pretend you are Huckleberry Finn.  Go outside, and look up at the stars.  Think about how they were made.

2. Try to guess the time by the position of the sun.  Think about the dependability of our universe.  The sun rises every morning at a predictable time.   Why is that so?

Answers to Comprehension Questions:  1. 480 km above the Earth’s surface 2. billions 3.  liquid, ice, vapor 4. False.  The Earth’s atmosphere protects us from the Sun and keeps us warm.  5. gravity

molecule- the smallest unit into which a substance can be divided without changing its chemical nature

gravity- the force that pulls objects towards the Earth

drift-a slow movement towards something

region- a large area

universe- all of space and everything in space

galaxy-a collection of millions and millions of stars


liquid- a substance that is not solid or gas and that can flow and be poured

vapor- a mass of very small drops of liquid in the air;  for example, steam

preserve- to keep something safe or in good condition

speckled- having many, many small dots of color, light, etc.

Reference:  Davis, Kenneth C. 2001. Don’t Know Much about Space, HarperCollinsPublishers

Oxford Wordpower Dictionary, 2000, Oxford University Press