Get a star map (they have an app for that) and a telescope or pair of binoculars, and go to a location at least a few miles out of town after dark and look at the stars. Try to identify constellations, galaxies, and any nebulae you can find.
Get a field guide to… anything! Then go to an appropriate location and look up everything you can. They have field guides for all kinds of things: birds, trees, bugs, flowers, animals, edible plants, rocks and minerals—whatever you both might find interesting, go out searching for them, identifying as many as possible. You may want to bring a camera or two to catch your own photos of your findings.
Planetariums can be so much fun when you go with an attitude of curiosity. If they have a lazer/star show, go to it. If they have experiments and gravity suits to try, do it. And don’t forget to check out the gift shop. There’s usually a lot of cool stuff in there, too.
Plant a Garden Together
Plant a garden with both of your favorite items. This is not only fun and educational, but it’s especially good if you’re really hoping for a follow-up date. “Hey, want to go check on our garden?”
Go to an Art Gallery
Sometimes art galleries can seem either boring or overwhelming to most people. Take your date to one, but instead of just passively admiring all the works, go with the idea of finding one piece that especially stands out to each of you. Get a good look around to make sure it’s the one that most catches your interest, and tell each other why that piece is your favorite.
Another fun thing to do at an art gallery is to come up with stories about the paintings. Make up scenarios that “explain” what’s going on. Be as detailed as possible. You may learn a lot about your date from their stories.
Visit the Zoo
Yes, it’s cliché, and yes, it’s still way fun. And believe it or not, most Zoos are open year round.
Go to a Museum
There are dozens of kinds of museums. There are history museums, church museums, science museums, art museums, children’s museums, animal museums (think giant aquarium), and even human museums (I’ve never been to a body museum, and don’t think I’d like to, but just saying). Go to the museum you think your date would most enjoy.
Learn a New Skill Together
You can learn a lot about a person by observing how they learn. Decide on a new skill to learn and use whatever resources you can to learn how to do it. The Internet is the obvious one, but there are also libraries, classes, and experts around that might help you learn a skill. Ask your date if there’s something he/she’s always wanted to learn to do, and learn it together. It could be dancing, karate, origami, microscope study, cooking, auto-mechanics, basketball, graphic design, plumbing, weaving, rock-tumbling, or any number of things. Learn it together. Then follow up with each other on later dates, or practice together.
Go to a Local “Gardens”
Go to a local professional garden park such as the Botanical Gardens, Red Butte Gardens, the Gardens at Thanksgiving point, and many of these gardens have annual events. Visit a local professional garden. You might want to bring a field guide along.
Find out what your date is geek about (maybe they LOVE examining the back of Afghans, or are a rifle nut), and go to a store, show, or festival surrounding that thing. People always love talking about about their own interests, and regardless of what you think of it all, your date will have a great time talking to you about it. Allow them to show you all the cool stuff that you may not yet know.