If you are chasing rainbows, you are trying to do or achieve something that is not really possible or realistic.
I know you want to become an actor but I think you should stop chasing rainbows and get an office job. Becoming a successful actor is really hard!
Bob had hundreds of plans and wild ideas about how he could become rich, but none of them ever succeeded. He was always chasing rainbows.
A wild goose chase is a phrase used to describe a situation when you spend a lot of time looking for something but never find it because you were given the wrong information.
We were told there was an excellent Korean restaurant in town and spent two hours looking for it, but we couldn't find it. We later found out it has closed down. What a wild goose chase!
Every second counts in Formula 1 racing and one of the most important things that decides which driver wins a race is pit stop times: the time it takes to change tyres and carry out repairs on a car during a race. The world's fastest Formula 1 pit stop was recorded during the German Grand Prix in July 2012, when it took the McLaren team 2.31 seconds to change driver Jenson Button's tyres.