AstroLab

Light Year Activity

Verbatim

Boy
There’s something that I don’t understand.

Boy
What is a light year? Does it mean that by looking at the sky we are seeing the past?

Father
You have heard about stars that are far away, haven’t you?

Boy
Yes.

Father
Well, some stars are so far away that the light that we see may be several thousand years old.

Girl
It’s like travelling through time.

Boy
I don’t understand and I still don’t know what a light year is.

Father
First you have to understand that light travels at a certain speed, exactly 299 792 metres per second.

Father
For example, at this speed, light from the sun takes eight minutes to reach earth.

Father
Do you see that star over there? It’s Sirius, the brightest star in the sky.

Father
But even if Sirius is one of the stars closest to the earth, its light takes 8.6 light years to reach us. We are actually looking at Sirius as it looked 8.6 years ago.

Father
A light year is the distance that light travels during one year. This is why we say that looking at the stars is looking at the past.

Boy
I never thought about it that way before. Now I understand!

Instructions

Read the comic strip carefully and try to associate the distances with the different elements (planets, nebula and galaxies) onscreen.

Click, hold and drag the mouse over available light year choices and associate them with a heavenly body. If you choose incorrectly, the association will not occur.

Now that you know what a light year is, can you make the associations that follow?

Elements to the left

31 to 50 light minutes
4 to 20 light minutes
4100 light years
5 to 11 light minutes
3.8 million light years
68 to 84 light minutes
2 to 14 light minutes
63 million light years

Elements to the right

M98
Galaxy
Venus
Mars
Saturn
Ring
Nebula
Jupiter
Mercury
Pluto