Extras

    Video thumbnail: Science Trek Gravity: Weightlessness hurts

    Science Trek

    Gravity: Weightlessness hurts

    What happens to humans in space?

    Gravity: Weightlessness hurts

    Video thumbnail: Science Trek Gravity: Fabric of Space

    Science Trek

    Gravity: Fabric of Space

    A sheet, a basketball, Einstein explained.

    Gravity: Fabric of Space