 The earth is over 5 billion years old. Life first originated in the oceans 3.4 billion years ago. The dinosaurs died out 65 million years in the past. Human recorded history stretches back 10,000 years in time. These numbers are too large to visualize, and difficult to compare. Here's an easy way to put time in perspective, and actually visualize different eras in the earth's history. You'll need a roll of toilet paper, a long hallway, and some sticky notes. 
Unroll the full roll of toilet paper down the hallway. We found that our roll contained 400 squares, and each square was slightly over 11 cm long. (Do all brands have 11 cm squares? Better check this!) The earth is about 5 billion years old. That makes each toilet paper square equivalent to 12.5 million years; each billion years of earth's history takes up 80 squares of toilet paper. On this scale, one year is represented by 0.00000088 cm ... a width too tiny to see. But we can certainly visualize the past 10,000 years of recorded history on this scale, and compare it to the other events in earth's history. Once the paper is completely unrolled, you can mark these important events in earth's history at the appropriate points: 
A note to teachers: There is a nice lesson here on ratios (grade 8 math). Fortunately I was their math teacher and science teacher!
 The idea for this demonstration is not our own ... we first read about it many years ago, and came across it again recently in a magazine; we just had to try it out ourselves, as it makes a very dramatic statement about the history of the earth. |
