Glossary term: Tide
Description: On Earth, the gravitational force is almost constant, pointing what we call downwards. But over larger distances, gravity's strength and direction vary, and those differences are called tidal forces. The Earth and the Moon, for instance, orbit a common center of mass due to their mutual gravitational attraction, but objects on the side of Earth nearer the Moon will be accelerated a bit more strongly towards the Moon, objects on the opposite side of Earth somewhat less. Earth's ocean water follows those tidal accelerations, forming "tidal bulges" directly under the Moon and on the opposite side, which produces Earth's tides.
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Term and definition status: This term and its definition have been approved by a research astronomer and a teacher
The OAE Multilingual Glossary is a project of the IAU Office of Astronomy for Education (OAE) in collaboration with the IAU Office of Astronomy Outreach (OAO). The terms and definitions were chosen, written and reviewed by a collective effort from the OAE, the OAE Centers and Nodes, the OAE National Astronomy Education Coordinators (NAECs) and other volunteers. You can find a full list of credits here. All glossary terms and their definitions are released under a Creative Commons CC BY-4.0 license and should be credited to "IAU OAE".
