# Introduction

```Investigation 23
How long have “we” existed?
Introduction
Modern-day astronomers can detect and measure the farthest light in the universe to be approximately 13.6
billion light years away. That means that if you were to look through a telescope at that object tonight, the
photons received by your eyes were first emitted 13,600,000,000 years ago. Given the fixed speed of light
(671,000,000 miles per hour), we know that it took exactly 13.6 billion years for that photon to travel to Earth.
That means that our best estimate of the age of Universe is approximately… 13.6 billion years. However, what
does that mean? There is a children’s book called “how much is a million” that places how much a million is to
scale using everyday objects. What does 13.6 billion mean in relation to the Earth? What does it mean to life
on Earth? What does it mean to you?
Objectives
1. To construct a time line using a single scale that show the relative dates of several key events in the earth’s
history.
2. To determine how long Homo sapiens have existed on earth, relative to those key events.
3. To appreciate the vast periods of time available for development of life to take place
Materials
paper rolls
meter sticks
markers
Procedure
1. Mentioned above, current methodology indicates that the Universe is most likely 13.6 billion years old.
How do we know that it cannot be younger? (10 points)
2. Explain how it could be possible that the Universe might be older than 13.6 billion years. (20 points)
3. You will be working in groups of 4. You will be given a strip of paper (receipt paper rolls), but only once
you have selected an appropriate scale. Record your scale below: (20 points)
Amount of Time:
1 Billion Years
1 Million Years
Distance on Paper:
4. Refer to the table at the very end. Complete the box on the far right, labeled “Distance on Paper” for each
event, using your scale from above. (20 points)
5. Once you have figured out the “distance” of each event, label one end of the paper with the first event in
history, and label the other end “Present Day”. Your task is to now complete the rest of the timeline, by filling
in the events inbetween at the appropriate intervals. (100 points)
6. Once you have filled in all of the events, you will need to make color (20 points) drawings, depicting what
was happening at each “event”. (20 points)
Study Questions
1. The Crab Nebula (look it up, it’s pretty neat) is estimated to have exploded (it’s a super nova, a star like our
sun that exploded) in the year 1054. Who comprised the last group to not be able to see the Crab Nebula? (10
points)
2. Complete the following sentence: “The majority (&gt;51%) of the Earth’s history has been dominated by…”
(10 points)
3. Explain: Has the development of life been relatively fast, or relatively slow when compared to the history of
the Universe? (20 points)
4. Explain: Has the development of complex life (us) been relatively fast or relatively slow when compared to
the history of the Earth? (20 points)
5. Think about this: Suppose that a planet, like our own, was created shortly after the initial expansion of the
Universe. Do you think that life would be like ours, more complex, or less complex? (10 points). Explain (20
points)
6. Suppose that the Cretaceous extinction never took place. Would Mammals have ever developed like we did?
(10 points). What would have happened to the Dinosaurs? (10 points) Speculate what the dominant form on
our planet might have looked like by now. (10 points)
7. Look up a “Trilobite”. Describe what they were (10 points), why they went extinct (10 points), and include
a color drawing of one in it’s habitat in the box below (50 points):
8. Is there any single event in the Earth’s history that has been the most important to life as we recognize it
today? Explain what happened, and why it is important. (20 points)
9. Pick one more important event in the Earth’s history. Explain why it is also extremely important to life as
we recognize it today. (20 points)
10. Why are plants important to animals? Explain (20 points)
Event
Origin of the Universe
Origin of Milky Way Galaxy
Origin of the Earth
Origin of Life
Origin of Photosynthesis
Great Oxygen Catastrophe
Origin of Eukaryotes
Origin of Exchange of DNA
Origin of Multicellular Organisms
Origin of Animals
Origin of Bilateral Symmetry
Origin of Fish
Origin of Land Plants
Origin of Insects
Origin of Gymnosperms
Origin of Amphibians
Origin of Reptiles
Permian-Triassic Extinction
Origin of Mammals
Origin of Birds
Origin of Angiosperms
Cretaceous Extinction
Development of Primates
Development of Hominids
Development of the first “Humans”
Development of modern Humans
Building of the Great Pyramid
Bubonic Plague in Europe
American Revolution
Civil War
WWII
JFK Assassination
Carl Sagan’s Cosmos
Time
13.6 Billion Years Ago
12.5bya
4.6bya
3.6bya
3.4bya
2.4bya
2bya
1.2bya
1bya
600 Million Years Ago
550mya
500mya
475mya
400mya
400mya
360mya
300mya
252mya
200mya
150mya
130mya
66mya
60mya
20mya
2.5mya
43,000 years ago
4500ya
600ya
239ya
150ya
74ya
52ya
35ya
Distance on Paper
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