Abstract

Do you like to look up into the night sky? There are so many stars, it can be mind boggling! Some ancient people marked time by the changes in star patterns. We still use changes in constellation patterns to mark astronomical time. Do constellations change more in one hour, one day, one month, or one year?

Objective

In this experiment you will investigate how the constellations change in the night sky over different periods of time.

Introduction

The telling of time is an ancient art, and different ways of marking time have been used by people of different cultures over the ages. Before the introduction of modern standard time, people had to use astronomical features to mark time, mainly the sun, moon and stars. Different calendars were created by different cultures who marked time by using different methods. Here are just a few:

• Gregorian Calendar: This calendar marks time by the rising and setting of the sun, called solar time. It was introduced in 1582 as a reform to the Julian calendar of 45 B.C. that had been initiated by the Romans. Before Gregorian and Julian time, people had been marking solar time with sundials and waterclocks set to the sun for thousands of years. This calendar was made obsolete by the introduction of Standard Time. However, the passage of the sun over the Greenwich meridian is still the standard scientific reference of world-time (UTC) for modern timekeeping.
• Lunar Calendar: In China, India and other eastern cultures people mark time by the cycles of the moon, called lunar time. Because the moon cycles are not exactly a month long, a leap month is added to the calendar now and then so that the lunar calendar changes with the seasons. The Romans saw this as too arbitrary, and so replaced the lunar calendar with the Julian calendar. In Islam, a purely lunar calendar is kept which does not add a leap month and strictly coun as twelve lunar months, and so is about 11 days shorter than the solar year.
• Zodiac Calendar: Instead of tracking time by the sun or moon, the Zodiac Calendar tracks time by the stars, called sidereal time. Sidereal time is mainly used for astronomical observation. The siderical calendar year, or Zodiac Calendar, has days that are shorter by four minutes. Each year is one day longer because a sidereal day is defined as the time it takes to see the stars in the same position in the sky: 23 hr. and 56 minutes.

How do the positions of the stars change over time? In this experiment you will investigate how the constellations change in the night sky over different periods of time. Will the patterns of constellations and stars in the sky change more in one hour, one day, one month or one year?

Terms and Concepts

To do this type of experiment you should know what the following terms mean. Have an adult help you search the internet, or take you to your local library to find out more!

• star
• constellation
• time
• moon
• sun

Questions

• Which constellations are in your night sky?
• How do they change over time?
• Do some stars change more than others?

Materials and Equipment

• computer
• Internet
• printer

Experimental Procedure

Variations

Careers

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Related Links

• Science Fair Project Guide
• Other Ideas Like This
• Astronomy Project Ideas
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