Every Thursday evening, I volunteer at The University of Denver's Historic Chamberlin Observatory. When a young person looks into the eyepiece of the telescope, I've learned to expect the oohs-and-aahs of wonderment and awe.
Getting the kids excited is easy, but the thing I enjoy most is getting that same reaction from an adult. I think that adults are more defensive with their excitement, and it's a fun challenge to try to coax it out of them. Most adults are uncomfortable feeling insignificant, and basking in your smallness can be tough. It's easy to turn this feeling around on someone. Instead of making them feel small, make them feel big:
"All of those stars emitted their light 32,000 years ago. Ever since, they've been on a journey destined to do nothing but land in your eyeball, be absorbed by your retina, and get converted into a electrical signal in your brain that you now call a memory."