Unit 3- Earth-Moon-Sun System Flashcards
How did Aristarchus find the distance of the Earth to the Moon?
He noticed that when he held his thumb up at arms length he could cover the Moon’s disc.
Therefore, he made an equation that was- tan 1= radius of the moon/ distance to the moon.
Thus, d= radius of the moon/ tan 1
1760/ tan 1= 1.008* 5 to the power of 5 to 3 sig figs
Or, 100800km
What is the mean diameter of the Sun?
1*10 to the power of 6
How was the size of the moon discovered?
U1-U2= time taken for the Moon to move through its own diameter
U1-U3 or U2-U4= time taken for the Moon to move through the Earth’s diameter
SO. U1-U2/U3-U4= diameter of the Moon/ diameter of the Earth
So, the moon was around 0.32-0.4 times smaller than the size of the earth
In modern days, it was discovered to be 0.27
What is the mass of the: Earth, Moon and Sun?
Earth= 5.6* 10 to the power of 24
Moon= 10 to the power of 22
Sun= 10 to the power of 30
What does it mean for the Moon to wax or wane?
When it waxes, it means that it ‘grows’
When it wanes, it means that it ‘shrinks’
What are tides?
They are the periodic rising and falling of large bodies of water. Wind and currents move the surface, which causes waves.
How are tides formed?
Gravitational attraction of the moon causes oceans to bulge up in the direction of the moon, and another one bulges out on the opposite side because the Earth is also being pulled towards the moon (and away from the water on the far side)
Why are there 2 tides per day?
Moon travels around Earth, they both orbit the sun. Combined gravitational force makes the world’s oceans rise and fall. It happens twice because the Earth if rotating while this is happening.
Why are there 2 tides per day?
Moon travels around Earth, they both orbit the sun. Combined gravitational force makes the world’s oceans rise and fall. It happens twice because the Earth if rotating while this is happening.
When do SPRING TIDES happen (what PHASE OF THE MOON)
During a FULL or HALF moon
What are spring tides?
When the high tides are very high and low tides are very low. They are also known as strong tides, and they occur when the Earth, Sun and Moon are in line. Gravitational forces from the Moon and Sun both contribute to the tides.
What are spring tides?
When the high tides are very high and low tides are very low. They are also known as strong tides, and they occur when the Earth, Sun and Moon are in line. Gravitational forces from the Moon and Sun both contribute to the tides.
When do NEAP TIDES occur (what PHASE OF THE MOON)
During the QUARTER PHASES
Describe what happens in neap tides
The Sun and Moon are at right angles so the bulges in the sea cancel each other. This means there is a smaller distance between high tides and low tides, AKA neap tides. They are especially WEAK. They occur when the gravitational forces of the Moon and Sun are perpendicular to one another.
How long is Earth’s precession?
25,772 years (26,000 years)
What is precession?
Gravity induced slow and continuous change in the orientation of an astronomical body’s rotation axis
What are the effects of precession?
1.) Positions of the SCP and the NCP appear to move in circles against the backdrop of the stars, completing one circle every 25,772 years.
What are the effects of precession?
1.) Positions of the SCP and the NCP appear to move in circles against the backdrop of the stars, completing one circle every 25,772 years. This means that Polaris isn’t the permanent ‘north star’, and that over time there will be a different ‘north star’
2.) The Earth’s rotation on its axis has a slight “wobble”, and it takes around 26,000 years to complete a 360 degree “wobble”. This is known as PRECESSION OF THE EQUINOXES or AXIAL PRECESSION
What are the causes of precession?
1.) Earth being an oblate spheroid
2.) Interaction with complex gravitational fields of the Sun and Earth, causing “wobbling” of the Earth’s axis
How often are star positions republished?
Every 50 years
What does Right Ascension (RA) mean?
The method of indicating a Star’s direction from the Earth
What is the effect of precession on a star’s RA?
It will cause a slight shift, meaning the stars will slowly change direction from the Earth
What are solar eclipses?
The MOON COMPLETELY BLOCKS THE SUN in perfect alignment BETWEEN the Earth and the Sun. The SHADOW OF THE MOON passes over certain parts of the Earth so a total solar eclipse can be seen
What phase does the moon have to be for a solar eclipse to happen?
NEW MOON
What is a lunar eclipse?
When the SUN EARTH and MOON ALIGN WITH EARTH IN BETWEEN and the Moon passes into the EARTH’S SHADOW. It’s not black, but reddish copper, making it a BLOOD MOON
Why does the moon turn red during a total lunar eclipse?
The blue light gets scattered outwards, and the red wavelengths are refracted, thus bent inwards.
NOTE: THE SHORTER THE WAVELENGTH, THE HIGHER THE FREQUENCY
shortest wave length to longest wavelength= Violet, Indigo, Blue, Green, Yellow, Orange, Red
When is a partial lunar eclipse occurring?
When the Moon passes into the Earth’s umbra, and into the penumbral shadow
Where does the observer have to be to observe: 1.) A solar eclipse 2.) A partial solar eclipse
1.) In the umbra
2.) In the penumbra
What is a: 1.) Photosphere 2.) Corona 3.) Chromosphere 4.) Prominences
1.) The visible side of the sun
2.) Sun’s outer atmosphere
3.) Portion of the Sun’s atmosphere located between the photosphere and the corona
4.) Eruptions occurring on the solar surface
What happens during an annular eclipse?
The sun’s photosphere is visible as a bright ring around the moon’s edges
Why do annular eclipses occur?
The moon is in the apogee of it’s orbit, meaning it’s further away from the Earth
