3. Earth, Moon & Sun Flashcards
How did Eratosthenes use observations of the Moon and Sun to determine the diameter of the Earth?
How did Aristarchus use observations of the Moon & Sun to determine:
Diameter of moon
Distance to moon
Diameter of sun
Distance to sun
- Diameter of Umbra = Diameter of Moon
- Made an assumption the rays of sunlight and umbra are the same
- Moon travelling at constant speed
- Measured time where each umbral contact took place - work out the time between UC 1&2 and UC 3&4 - these linked to diameter of moon
- Found time diff between 1&3 - helped with diameter of Earth
- Speed of Moon is constant - ration of Moon diameter to Earth diameter will be same of umbral contacts
How do the Sun and Moon produce high and low tides?
- The sun and moon have a gravitational pull on the Earth, creating a bulge
- Water is a liquid - can be manipulated/moved easily
- Moon has stronger pull as it’s closer
- Water bulges move around as the Earth spins/Moon moves
When/How do Spring tides occur?
- Occur every month, at every full/new moon
- The pull of the Sun and Moon combine to create an extra high tide (they are in conjunction/opposition)
What is precession?
- The gradual rotation of the Earth’s axis
- Causes things that used to be aligned to no longer be
- One complete rotation takes 26,000 years
How is the gradual precession of the Earth’s axis used in archaeoastronomy?
What is a solar eclipse?
- Moon is in front of Sun
- Only occur in full moon phase in daytime
What is a lunar eclipse?
Moon passes into Earth’s shadow
- Moon & Sun in opposition
Why do solar and lunar eclipses occur?
Due to their orbits & perspective from Earth
When/How do Neap tides occur?
- Occur when the moon is at the first/last quarter phase
- When the high tides are lower than usual and low tides are higher than usual
Why does a total lunar eclipse not happen every month?
The moon orbits on different planes so will not always pass into the Umbra therefore will not create a total lunar eclipse
