Astronomy Flashcards
Explain why the weight and value of g differ between the surface of earth and other celestial bodies
The bigger the mass of the planet the stronger the gravitational pull
w = mg -> more gravity causes an increase in weight
What is the order of planets in the solar system in terms of distance from the sun
1- Mercury
2- Venus
3- Earth
4- Mars
5- Jupiter
6- Saturn
7- Neptune
What is the geocentric model
that the Earth is the center of the universe, with the sun and planets revolving around it
Why did people believe the geocentric model
Lack of technology: to the naked eye, it appeared that the Sun, Moon, planets, and stars all revolve around the Earth
What is the heliocentric model
theory that places the SUN as the center of the universe, and the planets orbits around it
What evidence is there for the heliocentric model
- Earth orbits the sun faster than mars, so we undertake it, so it appears to reverse its direction in the sky
- Galileo observing moons orbiting Jupiter showed not everything orbited the Earth
Describe the planetary orbits
As the planets orbit the gravitational force causes the planet to change direction constantly so the speed is constant while the velocity is always changing
* The force causes the planet to accelerate without increasing its speed
Explain how, for a stable orbit, the radius must change if
orbital speed changes
- If the planet moves closer to the sun -> its orbital radius decreases
- The gravitational attraction to the sun increases
- (Force increases, and so does acceleration, which causes an increase in velocity)
- So, the orbital speed of the planet increases
What is steady state
says that the Universe has always existed, and that the Universe is expanding and constantly creating matter
What is the big bang theory
- the Universe began from a very small region that was extremely hot and dense
- Then there was a giant explosion, which is known as the Big Bang
- This caused the universe to expand from a single point, cooling as it does so, to form the universe today
What is evidence for the big bang theory
- Red shift
- Cosmic background radiation
What is Cosmic background radiation
leftover radiation from the Big Bang or the time when the universe began
What is red shift and how does it prove the universe is expanding
- Light appears red shifted from galaxies which are moving away from the earth
- The more red shifted the light from a galaxy is, the faster the galaxy is moving away from Earth
What are the differences between Steady state and the Big bang theory
- The big bang theory believes that the universe always changes
- Steady state theory believes it is and always has been exact same
How do all stars begin as
Nebulas
How do stars SIMILAR size to the sun develop
- red giant star
- white dwarf
- black dwarf
How do stars of BIGGER mass to the sun develop
- red super giant star
- supernova
- a neutron star, or a black hole (depending on size)
Describe the evolution of stars though the nebula
A star forms from massive clouds of dust and gas in space, also known as a nebula which is pulled together by gravity
Describe the evolution of stars though the star
The star is at this stable phase in its life
Describe the evolution of stars though the red giant
When all the hydrogen has been used up in the fusion process, larger nuclei begin to form and the star may expand to become a red giant.
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When all the nuclear reactions are over, a small star like the Sun may begin to contract under the pull of gravity. In this instance, the star becomes a white dwarf which fades and changes colour as it cools.
how does the balance between thermal expansion and gravity affect the life cycle of stars
- pressure from hot gases pushed the star outwards,
- gravity pulls it inwards.
- if the pressure from the hot gases is stronger than the gravity, the star will expand.
- if it is weaker than the gravity, the star will contract.
why are some telescopes located outside the Earth’s atmosphere
- telescopes in orbit around the Earth give much clearer images than ground-based telescopes (since clouds and dust in the air do not interfere with the image).
- also, the atmosphere absorbs some of the radiation they are designed to detect.
How have methods of observing the universe changed over time
The invention of the telescope meant that much more detailed observations could be made, and it became possible to see objects much further away.
