# 65. HOW LONG ‘TIL WE GET THERE?

SUBJECT: Science
GROUP SIZE: Individual
TIME: 60 minutes
TYPE OF ACTIVITY: Student Activity Discussion ~ TEACHING STRATEGY Guided Discovery Discussion
CONCEPTS: Light Year Relative Distance Space Travel
SKILLS: Reading and Interpreting Data Computation

Objectives: To provide the opportunity to calculate distances from Earth to a “nearby” star; to understand one of the difficulties about traveling in space is the time it takes to get somewhere.

how long activity sheet

Materials: Activity sheet provided.
Teacher Background Information:

One of the major problems with space travel is the amount of time it takes to cover the vast distances to even our closest neighbors. This short exercise gives the students some feeling about those distances and the time to cover them. Though this is primarily a math activity, the concept is essential to the understanding of many of the other problems associated with space travel.
Procedure:

Before handing out the activity sheet, talk with the students about some of the more fanciful space programs on TV or at the movies. Travel between planets and stars on some of these programs seems rather easy but, once the vast distances are truly comprehended, the difficulty of getting from one planet to another, using present technology, becomes apparent. Ask the students if they know how far it is to the nearest stars or to the recently discovered solar systems. Get some mileage estimates and write them on the board. Then put up the following chart:

STAR NAME DISTANCE IN LIGHT YEARS
Proxima Centauri 4.3
Barnard’s Star 6.0
Wolf 359 8.1
Lal 21185 8.2
Sirius 8.7
UV Cet 9.0
Ross 154 9.3
Ross 248 10.3
Eri 10.8
Ross 128 11.1
61 Cyg 11.2
Procyon 11.3

Ask your students to select a star for use in the activity and hand out the activity sheets to each of them. Talk about light years with them and make sure each has computed the first question correctly. Do a second question with them using a star they picked. Check again to be sure they understand how to compute correctly. Let them finish the rest of the problems on their own.
Extensions:

Have your students look up the distance to other stars they may have heard of or to the Vega system where a solar system was recently discovered. Have them compute the distance and perhaps the length of time it would take to travel there at some portion of the speed of light. If it were possible to travel at the speed of light, how long would it take? (See lesson 92 on page 229, “It’s All Relative,” of the K-6 “Come Fly with Me” science book for more ideas)
ACTIVITY SHEET

FOR HOW LONG ‘TIL WE GET THERE?

Distance to a star is expressed in units called Light Years. A light year is the distance light can travel in one year. At 186,000 miles per second (light speed) how far would light travel in a year?

Pick a star from the chart your teacher has placed on the board.

Your star is called _________. It is _________light years away.

Converting this into miles, your star is __________miles away. Now let us consider our present level of technology, as well as the possibility of a major breakthrough in our propulsion systems.

Because of the large numbers involved, we will stick to round numbers. It is not an exact number that is important here, it is the concept of time required that is important.

To escape the Earth, you need to exceed the speed of 25,000 miles per hour. We have achieved this speed on numerous probes to the inner and outer planets. At the speed of 25,000 miles per hour, how long would it take you to reach the moon, a distance of about 225,000 miles? _______________.

When we first went to Jupiter, we reached a speed of 32,000 miles per hour. At that speed, how long would it take you to reach the moon? __________.

At that same speed, how long would it take you to cross the United States? Consider the distance about 4000 miles. Your answer will be part of an hour. Convert this to minutes. _________________

Given the speed of 50,000 miles per hour (the Pioneer on passing Jupiter achieved this speed), how long would it take to reach your star? ______________

Now let’s take a step into the future and ride a space craft which can travel about 1,000,000 miles per hour. At that speed you could reach the moon in about 15 minutes and cross the United States in about 16 seconds. How long would it take you to reach your star? Give your answer in hours, days and, finally, in years. _________________

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