A NASA spacecraft is expected to collide with an asteroid tonight.
The craft which is the size of a vending machine is part of a test to redirect the rock.
This asteroid isn't heading for earth, and the test isn't expected to send it in our direction.
Professor Alan Fitzsimmons from Queens University in Belfast is part of the team - he outlines what would happen if an asteroid that size did hit land:
"If it landed in Ireland, it would certainly destroy Dublin, and most of the surrounding counties."
"The test has been designed to be perfectly safe."
"There is no danger of it coming anywhere near the earth in future."