The Connecticut Science Center is easily reached by road or public transport. It's right next to the Connecticut Convention Center, just a 0.8 mile walk from the Hartford Station on Union Place, or take the free "dash" downtown shuttle which stops at both the Convention Center and Hartford Station. It operates 7 AM to 7 PM on weekdays.
Other bus services use different downtown locations. Megabus stops 0.3 miles north of the Science Center on Columbus Blvd between Morgan & Talcott St.
The nearest major airport is Bradley International, about 25 minutes north of Hartford. CT Transit Route 30 (the Bradley Flyer) goes to/from Bradley approximately every hour. The 30X bus stops at the Convention Center on the way to the station, while the 30N goes to the station.
See the CT Travel Smart website for traffic information, or use one of the Connecticut Department of Transportation-approved mobile apps.