Astronomy - Chapter 1 - Earth, Moon and Sun - EARTH
A mind map to show facts about Earth.
- Created by: Georgina
- Created on: 08-04-13 10:35
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- Astronomy - Chapter 1 - Earth, Moon and Sun - EARTH
- Key features
- It's atmosphere - oxygen and nitrogen
- Liquid water - covering 70% of the surface
- Life in all it's diverse forms
- Scattering Light
- Blue light has a small wavelength compared to red light and green light
- Molecules in the air (dust) scatter the blue light in all directions - this does not happen with red and green light
- This is why we see a blue sky
- Light Pollution
- It's called SKY GLOW
- It prevents faint stars, nebulae and the Milky Way from being observed
- wasteful light shines up into the sky - causes an orange background haze
- The countryside is the ideal place to observe
- Eratosthene
- He was the first person to get an accurate measurement of the Earth's circumference
- He was a Greek geographer and mathematician in the 3rd century BC
- He put a stick at Alexandria - the angle was 7*
- He got another stick and put it in Syene which was on the Tropic of Cancer
- This means it casts no shadow
- He worked out that the distance between these two places was 790 km
- He used geometry to find out that the Earth was 50 times the value
- His result was very accurate - 5% error
- Earth's Shape
- Earth is an oblate spheroid
- This means that it is slightly flattened at the poles
- It is squashed by 42 km at the north and south poles
- Earth's diameter is 13,000 km
- Earth is a spheroid because...
- Ships disappear over the horizon
- satellites orbit the Earth
- the curve of the Earth's shadow during a lunar eclispe
- Earth's rotational period
- Earth has a rotational period of 23 hours and 56 minutes
- To get a 24 hour day the Earth has to spin an extra 1 degree - which takes 4 minutes
- Key terms
- Equator: A line dividing the Earth into the Northern and Southern hemisphere
- Tropics: Two parallel lines of latitude representing the points farthest north and south at which the sun can shine directly overhead
- Latitude: Distance of a place either North or South of the Earth's equator usually expressed in degrees and minutes
- Longitude: Angular distance on the earth's surface expressed in degrees (or hours), minutes, and seconds
- pole: two locations North and South pole on the surface of the Earth or a celestial object
- Horizon: The line at which the Earth surface and sky appear to meet
- Meridian: A circle of constant longitude passing through a place on the Earth surface and the poles
- Zenith: highest point reached by a celestial
- Telescopes
- Refractor - A glass convex lens collects the light and brings it into a focus
- Reflector - A curved mirror (or one made from several segments) collects the light
- Some of the largest telescopes are made from reflectors
- Because: They do not suffer from chromatic aberration because all wavelengths will reflect off the mirror in the same way
- The mirrors can be made very big
- They are cheaper and can be made the same size as refractors
- Light is reflecting off the object rather than passing through it
- Only one side of the telescopes objects needs to be perfect
- Van Allen Belts
- Are two doughnut-shaped rings of spiralling high-energy particles held in place by Earth's magnetic field
- The inner belt was discovered in January 1958
- The inner belt consists of high energy protons - formed by collisions between cosmic rays and atoms in the atmosphere
- The inner belt can pose a hazard to astronauts and scientific instruments as it has low altitude of 0.1 and 1.5 Earth-radii
- The outer belt was discovered in December 1958
- The outer belt is more dynamic and consists of electrons and other charged particles emitted by the sun
- The outer belts altitude is between 3 and 10 Earth-radii
- Earth's atmosphere
- Benefits of Earth's atmosphere
- Absorbs UV radiation
- Absorbs X-rays and gamma rays
- regulates the temperature - this allows water to remain in liquid form
- Provides us with oxygen - so we can breathe
- PARTLY stops meteoroids from hitting us
- Drawbacks of Earth's atmosphere
- Refraction of light passes through the turbulent atmosphere causing the stars to twinkle and restricting the resolution of the image
- Selective scattering making the sky appear blue and preventing astronomers from making observations during the day
- Absorption and reflection of radiation preventing most wavelengths from reaching sea-level
- UV, infrared and X-rays are sited on high ground so that they can be detected
- Benefits of Earth's atmosphere
- Key features
- Life in all it's diverse forms
- Scattering Light
- Blue light has a small wavelength compared to red light and green light
- Molecules in the air (dust) scatter the blue light in all directions - this does not happen with red and green light
- This is why we see a blue sky
- Light Pollution
- It's called SKY GLOW
- It prevents faint stars, nebulae and the Milky Way from being observed
- wasteful light shines up into the sky - causes an orange background haze
- The countryside is the ideal place to observe
- Equator: A line dividing the Earth into the Northern and Southern hemisphere
- Benefits of Earth's atmosphere
- Absorbs UV radiation
- Absorbs X-rays and gamma rays
- regulates the temperature - this allows water to remain in liquid form
- Provides us with oxygen - so we can breathe
- PARTLY stops meteoroids from hitting us
- Drawbacks of Earth's atmosphere
- Refraction of light passes through the turbulent atmosphere causing the stars to twinkle and restricting the resolution of the image
- Selective scattering making the sky appear blue and preventing astronomers from making observations during the day
- Absorption and reflection of radiation preventing most wavelengths from reaching sea-level
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