Question 76
In this investigation, you will use an analogy for estimating the number of stars in a galaxy.
Work in groups of two or three.
You will need:
• one large cup or other container filled with coarse sand or fine gravel, for the whole class
• hand lens (magnifying glass) for each group
• piece of white paper for each group
• small container for the whole class
• access to laboratory equipment for measuring masses and volumes
• calculator for each group
Scientists cannot count the number of stars in a galaxy because there are too many. However, scientists can estimate the number of stars in a galaxy.
You are going to estimate the number of grains of sand in your container. There are too many to count them all, so this activity is an analogy for how scientists estimate numbers of stars.
Method
1 Put a small quantity of sand from the large container onto the white paper and separate the grains. You should only put out the quantity you can count easily.
2 Count the grains, record the number, and put the grains into the small container.
3 Do the same again: count some grains from the large container and then add them to the small container.
4 Write down the total number of grains your group put in the small container.
5 Decide, as a class, whether you want to work in mass or volume for the last two steps.
6 Measure the total mass or volume of the grains in the small container. A sensitive balance can be used to measure the mass, or a small syringe without a plunger can be used to measure the volume.
7 Put the grains from the small container back into the large container. Measure the total mass or volume of sand in the large container.
Work in groups of two or three.
You will need:
• one large cup or other container filled with coarse sand or fine gravel, for the whole class
• hand lens (magnifying glass) for each group
• piece of white paper for each group
• small container for the whole class
• access to laboratory equipment for measuring masses and volumes
• calculator for each group
Scientists cannot count the number of stars in a galaxy because there are too many. However, scientists can estimate the number of stars in a galaxy.
You are going to estimate the number of grains of sand in your container. There are too many to count them all, so this activity is an analogy for how scientists estimate numbers of stars.
Method
1 Put a small quantity of sand from the large container onto the white paper and separate the grains. You should only put out the quantity you can count easily.
2 Count the grains, record the number, and put the grains into the small container.
3 Do the same again: count some grains from the large container and then add them to the small container.
4 Write down the total number of grains your group put in the small container.
5 Decide, as a class, whether you want to work in mass or volume for the last two steps.
6 Measure the total mass or volume of the grains in the small container. A sensitive balance can be used to measure the mass, or a small syringe without a plunger can be used to measure the volume.
7 Put the grains from the small container back into the large container. Measure the total mass or volume of sand in the large container.
