Imagine blowing a soap bubble ... a rather large soap bubble, twenty miles across. In the center of our humongous bubble floats a grapefruit. Flying around the grapefruit – some flying close, some staying far out – are fruit flies ... perhaps just one, perhaps dozens.

Now let’s burst the soap bubble, leaving us with a grapefruit surrounded by fruit flies, flying near and far.

Al Stahler enjoys sharing science and nature with friends and neighbors, in The Union and on KVMR-FM. He teaches classes for both kids and grown-ups, and may be reached at