What You Need:
- Marbles of two different sizes
- Glasses of equal size - 2
- Fill a glass to the brim with small marbles and fill another glass to the brim with larger marbles.
- Which glass has the higher volume of empty space? You would think the obvious answer is the glass with the larger marbles as it has more empty space between the marbles.
- To test your answer, fill one glass to the brim with water and then pour the water into the other glass. Surprisingly, it will fill the other glass exactly to the brim.
Ratio of empty space between randomly packed spheres to the total volume of the spheres is a constant. This is related to an important geological fact-random packing of pebbles, even though their shapes are not spheres, has the same constant ratio of space to solid matter regardless of pebble sizes. As a consequence, if water is moving underground through strata of pebbles, it flows at the same rate regardless of the sizes of the pebbles.