1.1 Earth Flashcards
What is the earths diameter
13,000km
What shape is earth!
Oblate Spheroid
What features distinguish us from other planets
Atmosphere
Liquid water
Life
How do we know the earth is not flat?
Ships disappear below horizon
Satellites orbit Earth which would be impossible if it were flat
Curvature of the earths shadow during a partial lunar eclipse
What’s latitude yo
The angle between a point on the earths surface, how far north or south you are of the equator
How much is the earth tilted by
66.5 to the plane on which it orbits the sun (ecliptic)
What are the tropics
The Tropic of Cancer is 23.5degrees north
Tropic of Capricorn is 23.5degree south
What’s longitude
Angular displacement of how war east or west you are of the prime meridian
What’s the zenith
Point directly above the observer
What’s the horizon
Imaginary plane that meets the observer at a tangent to the earths surface - where sky meets seas/land
What’s the main source of light pollution?
Commercials and sports lights
Street lamps
Domestic and industrial security lamps
Lights in car parks and shopping centre
How did Eratosthenes estimate circumference of earth?
He was in Syene near the Tropic of Cancer and saw at noon a stick had no shadow , he then at the same time next year in Alexandria that was a 7 degree shadow he knew this was 1/50 of a circle and that the distance between the 2 places was 790km and so used simple geometry to sea earth was 50 times this - got 39,500km which was within 5% accuracy
What’s the composition of the earths atmosphere
78% nitrogen 21% oxygen 1% argon 1% water vapour average 0.04% carbon dioxide
What’s the kármán line?
The boundary for the atmosphere and space which is 100km
What are the benefits of the atmosphere
Regulates temperature
Absorbs uv Ray’s that can cause skin cancer
Absorbs X-rays and gamma rays
Allow liquid water
Provides oxygen to breath
What’s is a draw back of earths atmosphere?
The refraction of light as it passes through our turbulent atmosphere causing stars to twinkle and restricting resolution
The selective scattering of shorter blue wavelengths making sky blue so we can’t observe in day
Absorption of most electro magnetic radical ion like uv, gamma and X-rays requiring earth orbiting satellites instead
What’s are the 2 Windows electromagnetic radiation can reach the ground
Optical window
Radio window
What effect does the atmosphere have on long electromagnetic radiation (EMR)
There are reflected back into space by electrons in ionosphere
What does the atmosphere do the shorter EMR waves
(Microwaves) are absorbed by water vapour and oxygen
What does the atmosphere do to infrared radiation
It’s absorbed by water vapour
Carbon dioxide and methane
What does the atmosphere do to uv Ray’s
Absorbed by ozone(O3) and shorter wavelengths by O2
What’s does the atmosphere do to X-rays and gamma rays
Absorb them by oxygen and nitrogen so radiation loses energy and fails to penetrate much of upper atmosphere
What are the 2 types of telescope?
Refractor- convex lens
Reflector- curved mirror
Both collect light and bring it to a focus
What’s the objective of a telescope?
This diameter of the lens
What’s selective scattering?
When The atmosphere is better at scattering certain wavelengths than others
Scattering is a rapid process whereby light is actually absorbed by a particle and then quickly emitted in another direction.
What are the advantages of telescopes with a bigger objective
They collect more light
Higher resolution in proportion to diameter
How do you work out how to compAre how many times higher the resolution is of two telescopes ?
Example
A 10 metre telescope collect 25 times more light Than a 2metre telescope 25=5squared so it has 5 times higher resolution
Square root the amount of times it collects more light= how many times higher the resolution is
What’s the most popular lens for s telescope?
A reflector as mirrors can be made to a higher precision
What things should you consider when choosing an observing site!
Atmosphere
Cloud cover, air turbulence, Sky brightness, water vapour content
Geographical location
Access, utilities, ground stability
What’s are the advantages of space telescopes?
There’s no atmosphere to blur images or reduce resolution
No light pollution
No adverse weather problems
No day or night can observe all the time
Can detect other wavelengths like X-rays or IR waves
What are the problems with space telescopes?
Reduced life time
Difficult or impossible to maintain or repair
Damaged by solar wind or radiation
More expensive to land into orbit and build
What’s the inner van allen belt like
Made of high energy proton between 0.1 and 1.5 earth radii can be hazards to atronauts and satellites
What’s the outer van Allen belt like
Mainly electron altitude of between 3-10 earth radii
What’s the perihelion
When we are closest to the sun in January
What’s aphelion
When we are furthest from the sun in July
