A Large Number
Theme: God’s family is large and growing.
Bible Verse: I will multiply your [Abraham’s] descendants as the stars of the heaven and as the sand which is on the seashore. (Genesis 22:17)
Materials Needed:
• Small amount of sand
• Magnifying glasses (optional)
• Small rulers
Bible Lesson
In Genesis 22, Abraham’s obedience was tested regarding the sacrifice of his son Isaac. Abraham was willing to obey, and God provided a ram instead. Then God promised Abraham a great family blessing. Abraham’s descendants would number as many as the stars in the sky and the sand grains on the seashore. Today, four thousand years later, all believers can be called the “children of Abraham.” True to Scripture, no one knows the total number of Christians worldwide and throughout the ages, surely numbering in the billions. God’s kingdom is still growing, even in this troubled world, as people acknowledge their Creator and call upon his name.
Science Activity
Sand grains provide a good example of an extremely large number. Participants are challenged to count some individual sand grains, and then to estimate the total grains on all the seashores of the world. There is some math involved, but the exercise is worth the effort.
Give each participant a ruler and a pinch of sand. If sand is not available, salt or sugar can also be used. The particles can be sprinkled on a dark smooth surface that shows them clearly. The goal is to count the number of grains along a 1-inch length of ruler. With the ruler edge, push some of the grains into a line and begin counting. The exact number is not necessary and depends on the particle size. A magnifier may be helpful. My own 1-inch lineup totaled nearly 100 sand grains.
Now we need to estimate the number of sand grains in a cubic inch, or handful of sand. Take the lineup number and multiply it times itself twice, cubing it. If the initial number was 100, then 1003 is 1,000,000 or 106. Going further, a fair estimate for the sand on all the seashores of the world is 1016 cubic inches, or 10 thousand trillion cubic inches. (See the science explanation for the origin of this number.) Multiplying these two numbers gives the worldwide total of sand grains:
106 x 1016 = 1022
The final number obtained by participants should be close to this result. This number estimates all the sand grains on the earth’s shorelines. Amazingly, it is also approximately the total number of known stars in the universe. In words, this number equals 10 billion trillion stars or sand grains. Such a vast number is beyond our comprehension. The meaning of Genesis 22:17 is not that Abraham will have exactly 1022 offspring. Instead, the promise is that God’s family is beyond counting, and it’s still growing!
Science Explanation
Most sand grains consist of quartz fragments made of silicon dioxide, SiO2. This common mineral has a high hardness and is not easily dissolved or chemically altered. As a result it lies on many beaches in abundance as an end product of rock erosion.
Sand grains are lined up along the edge of a ruler and counted.
Let’s estimate the number of cubic inches of sand on all the earth’s seashores (1016), as used in the science activity. As a rough guess, assume there is a total of a million miles of sandy seashores. This number equals 42 trips around the earth and includes the many irregular shorelines. Further, assume the average beach is 100 feet wide and filled to a depth of 10 feet with sand. These would seem to be a conservative estimate. Now convert all three numbers to inches—length, width, and depth—and multiply them to get the total sand volume in cubic inches. There are 63,360 inches in one mile. The final answer is close to 1016 cubic inches. As earlier, multiply this number by 1 million to obtain the total sand grains, 1022.
This is also approximately the total number of photographed stars within all the galaxies of the known universe. This is more than a trillion stars for every person on earth. Whether one considers sand grains or stars, both show God’s great glory.