The Earth, Sun And Moon Flashcards
Revision from chapter 31 (gravity)
If any 2 masses are placed near each other, they will be attracted to each other by a force of gravity.
If the masses are small, the force of attraction is very small, too small to take into account.
If one of the masses is very large, e.g. the moon, a planet or star, the force of gravity is much larger.
The force of gravity is also affected by distance. The smaller the distance from the centres of the masses, the greater the force of attraction. The force of gravity would be strongest if a body had a huge mass and was compressed into a very small volume with a small radius (very dense) e.g. a neutron star.
How long does it take the earth to make one full revolution around the sun. What does the earth also do?
why is this different for each celestial body orbiting the sun?
it takes the earth 365.35 days/a year to make one full revolution or orbit around the sun. The earth also revolves on its own axis every 24 hours.
Different planets take different times to orbit the sun.
How long does it take for the moon to revolve around the Earth?
The moon is a satellite of the earth. it makes one revolution of the earth every 27.3 days.
Explain the idea of ‘days’ on earth
At any one time only half of the earth is facing the sun. The side of the earth facing the sun has ‘day’ and the side turned away has night. The Earth rotates on its own axis every 24 hours. This ensures that the half in the shade will eventually be in the light.
To what degree is the earths axis that it rotates on?
he Earth’s axis is tilted 23.5 degrees. The angle varies a little over time, but the gravitational pull of the moon prevents it from shifting by more than a degree or so. This tilt is what gives us seasons
What does the sun do for us and the earth?
Without the sun, the earth would be a cold, frigid planet. The light from the sun heats the planet.
Explain the spread of rays of light as it hits the earth
If a ray of light hits the ground at 90 degrees the energy will be spread over a smaller area than if it struck the ground at a lesser angle. The first ray is spread over a small surface area. This happens in the hottest area of the planet. The 2nd ray of light is spread over a much larger area. Since the same amount of energy is spread over a larger area, the 2nd region is colder than the first.
What happens due to the rotation of the earth
Due to the rotation of the earth’s around the earth the part tilted towards the sun changes during the year
How are seasons caused?
The seasons are caused by the axis of the earth being tilted at 23.5 degrees. In June, the northern hemisphere is tilted closer to the sun (summer) and the southern hemisphere I’d further from the sun (winter). In December, the opposite happens.
When is the moon visible from the earth?
The moon is visible on the earth when it reflects light from the sun.
What is the changing appearance of the moon referred to as?
The changing appearance of the moon as it orbits the earth is referred to as the phases of the moon
Break down the 27.3 day long lunar (moon) phases beginning on day 1
Day 1: new Moon- We cannot see anything because the sunlit part of the Moon is facing away from the Earth.
Day 2-6: waxing Crescent- the moon appears as a crescent. Since the moon is getting bigger it is called a waxing Crescent
Day 7: first quarter- we see half of one face of the moon.
Day 8-13: waxing gibbous- We see more and more of one side of the moon
Day 14: full moon we see all of the Illuminated part of the moon
Day 15-20: waning gibbous- we see less and less of the Illuminated Side of the Moon until half of one face seems illuminated. Since the amount of moon illuminated is getting less It is called waning gibbous.
Day 21: third quarter- we see half of one face of the moon.
Day 22-26: waning Crescent- the illuminated portion of the moon gets less and less.
Day 27: we have a new Moon Bd the cycle begins again.
What does the word eclipse mean?
The word eclipse means to obscure.
When does an eclipse occur and what are the two main types of eclipse?
An eclipse occurs when a celestial body gets in the way of the sunlight illuminating another celestial body. There are two main types of eclipse a lunar eclipse and a solar eclipse.
Definition of a lunar eclipse
A lunar eclipse happens when the Earth comes between the sun and the moon. It happens only during a full moon and only if the moon passes part of the Earth’s shadow.
