I asked them to guess how many workers it took to build a 747 jetliner. Their consensus was about 100. I told them that, when those building the components were included, the number was closer to 100,000 and they were amazed.
I showed them a photograph of the fastest crewed jet aircraft ever constructed, the SSR-71 and told them that it could travel coast to coast in just over one hour. So I asked them how long it would take at the steady speed of 4000 km/hr to go from the Solar System to the system of the nearest other stellar system, Alpha Centauri. They estimated 30 years. I told them that the correct answer was about a MILLION years and they were amazed.
And so forth.
27 
Message Thread 