The Spirit Level

"The Spirit Level" is a concept from physics that describes how a spirit level tool is used to check if a surface is perfectly horizontal or vertical. The tool contains a liquid-filled vial with an air bubble inside. When placed on a surface, the bubble centers itself between marked lines if the surface is level (horizontal) or plumb (vertical). This helps ensure surfaces are properly aligned, which is important in construction and carpentry for accuracy and safety. The principle relies on gravity and the liquid's ability to settle evenly, indicating when a surface is truly aligned.