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Very large numbers are commonly used to describe the distances between objects and the sizes of bodies in the Universe. It’s difficult to visualize quantities expressed as millions, billions and trillions because we don’t have much practice in using such large numbers in the course of everyday life. The following activity will give you practice in using large numbers as you convert back and forth between two familiar units of time.

When you compute answers for this activity, the number of hours in a day is exactly 24 and the number of days in a year can be rounded to exactly 365. All computations should be based on one year consisting of 8,760 hours. (24 hours x 365 days = 8,760 hours)

Hint: Use reference tools such as StarChild to find unknown historical dates.


1. What is your age in hours? ____________________

2. If you live to be one hundred years of age, how many hours will you have lived? _________________

3. To the nearest whole year, how many years would you have to live to reach the age of 1 million hours? _________________

4. The oldest person who ever lived was Jeanne Louise Calment. She was born on February 21, 1875 and died at the age of 122 on August 4,1997. How many hours had she lived? __________________ (assume that birth and death took place at the same time of day)

5. "King’s Holly", a plant found in Tasmania, is believed to be 40,000 years old. How many hours of age does this represent?

6. In what year would an event that happened 2 million hours ago have occurred? _____

Assume that each of the following historical events occurred on today's date. Look at the year or historical time in which each occurred, then determine how many hours ago each event took place.

7. Chewing gum was invented in the United States in 1848.

8. William Herschel discovered Uranus in 1781.

9. The pressure cooker was invented in France in 1679.

10. The Great Wall of China, incorrectly said to be the only man-made object visible from the Moon, was completed 2,174 years before man set foot on the Moon.

11. The Minoans invented the flush toilet 3,493 years before Columbus set sail for the "New World".

12. The first Olympian Games (which evolved into the Olympic Games) were held 2,745 years before Jocelyn Bell Burnell discovered pulsars.

Challenge: Name an event that took place one billion or more hours ago. Cite your references and show all of your computations.


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Imagine the Universe is a service of the High Energy Astrophysics Science Archive Research Center (HEASARC), Dr. Alan Smale (Director), within the Astrophysics Science Division (ASD) at NASA's Goddard Space Flight Center.

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All material on this site has been created and updated between 1997-2012.

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