tidal lock
One face forever
Tidal lock is a gravitational phenomenon where one celestial body always shows the same face to another—its rotation period matching its orbital period exactly.
The Moon is tidally locked to Earth, which is why we only see one side.
The term extends to any situation where two things become permanently synchronized or fixed in orientation relative to each other.
Apparent rocking motion
- perigeeOrbit's closest point
- apogeeHighest orbital point
- eccentricityUnconventional behavior or nature
- inclinationDisposition toward something
retrograde · prograde · apsis · geostationary · circular orbit · elliptical orbit
Messenger god or planet
- CharonMythical underworld ferryman
- IoJupiter's volcanic satellite
- EuropaGalilean moon with subsurface ocean
- GanymedeJupiter's largest natural satellite
Callisto · Titan · Triton · Pluto · exoplanet · habitable zone · natural satellites
Not varying at all
- fixedRestored or immovable
- permanentFixed without end
- eternalLasting without end
- staticWithout motion or change
perpetual · immutable · stabilized · invariable · steady-state · equilibrium
Amplified oscillation at natural frequency
- torqueRotational force measurement
- angular momentumRotational motion quantity
- circularizationMass mailing process
- orbital decayGradual loss of altitude
Half of a ball
- habitabilitySuitability for dwelling
- climate extremesAbnormal atmospheric conditions
libration
Apparent rocking motion
- perigeeOrbit's closest point
- apogeeHighest orbital point
- eccentricityUnconventional behavior or nature
inclination · retrograde · prograde · apsis · geostationary · circular orbit · elliptical orbit
Mercury
Messenger god or planet
- CharonMythical underworld ferryman
- IoJupiter's volcanic satellite
- EuropaGalilean moon with subsurface ocean
Ganymede · Callisto · Titan · Triton · Pluto · exoplanet · habitable zone · natural satellites
unchanging
Not varying at all
static · perpetual · immutable · stabilized · invariable · steady-state · equilibrium
resonance
Amplified oscillation at natural frequency
- torqueRotational force measurement
- angular momentumRotational motion quantity
- circularizationMass mailing process
hemisphere
Half of a ball
- habitabilitySuitability for dwelling
- climate extremesAbnormal atmospheric conditions
- spacespace, sun, moon, stars, star
- canalsGrand Canal, Panama Canal, Suez Canal, Erie Canal, canal boat
- Moon sciencelunar surface, lunar orbit, lunar phases, lunar craters, Apollo program
- tidesebb, slack water, ebb and flow, flow, Bay of Fundy
- moonfull moon, lunar, crescent moon, new moon, half moon
- Harbor Structuresdock, pier, wharf, jetty, moorings