What are some similarities between the geocentric model and the heliocentric model?
- Both rotate around one celestial body
• Both used to try to show what orbits what in the universe
• both models of the solar system
What are some differences between the heliocentric model and the geocentric model?
- Geocentric-everything revolves around the earth
• heliocentric - everything revolves around the sun
• the heliocentric model were ellipses not circular orbits
State some of the observations this model could explain.
It explained why the sun and the stars went around the Earth. It also explains why we don’t feel the Earth move.
What was the problem with this model?
Some planets move backwards as they go around the Earth however the model states that they all move in perfect circles.
What does geo mean?
Earth
What does helio mean?
The Sun
What did Galileo see that made him think that the earlier astronomers might be wrong?
He saw Jupiter’s moons orbiting Jupiter and not the Earth.
What are some theories made by scientists?
Copernicus suggested that the Earth and all the planets orbited the sun.
Giordano Bruno took Copernicus’ theory, and added some of his own, such as the idea that life might exist in other places in the universe.
Galileo Galilei improved the design of the spyglass to invent a telescope good enough to to study the planets. He discovered four moons orbiting Jupiter.
Johannes Kepler came up with the theory that orbits are elipses not circles.
What happend in the Big Bang?
All the energy and matter that exists now was there, initially in a soup of tiny particles which formed into protons and neutrons and then these formed the lighter elements - hydrogen, helium, lithium.
When:
- was the Big Bang?
● were the first stars formed?
● was the milky way formed?
● was the sun created?
● was the earth created?
● did the first life on earth appear?
13.8 billion years ago
100 million years after the Big Bang
13.6 billion years ago
4.6 billion years ago
4.6 billion years ago
3.7 billion years ago
What is redshift?
The wavelength of the light is stretched, so the light is seen as ‘shifted’ towards the red part of the spectrum meaning the source is further away. This is used to meausre the distance of items in space.
What is the sequence of a star the same size as our sun?
Protostar
Main sequence star
Red giant
White dwarf
Black dwarf
What is the sequence of a star much bigger than the sun?
Protostar
Main sequence star
Red supergiant
Supernova
Black hole OR neutron star
What happens to dtars with low masses?
Stars with low masses remain in their main sequence for much longer, as their core is cooler than that of more massive stars.
However, eventually, after billions of years, they run low of hydrogen fuel in their core. At this stage, they begin to move off the main sequence into the next phase of their lives.
Describe the life cycle of stars with low masses.
- They are formed from large clouds of gas and dust that collapse under their own gravity until they are dense enough for nucleur fusion to begin.
- The cloud of gas and dust heats as it contracts. When it is hot and dense but nuclear fusion has not yet started it is known as a protostar. This phase can last for 100 000 years.
- When the protostar reaches a critical density, fusion begins and the star starts to shine. When the outward pressure from fusion balances the star’s gravity, it stabilises as a main sequence star.
- When the star runs out of hydrogen, this is the end of its ‘main sequence’ and it begins to swell out. Core contraction continues until it is hot enough for helium to fuse into carbon and oxygen.
- The core of the star heats as it contracts. This causes the material around the core to heat up until helium fusion begins here.
- Stars the same size as our Sun (or smaller) swell out and cool down turning red. A red giant.
- When fusion stops no more radiation is released and the star collapses in on itself, this forms a ‘ White Dwarf’. This is smaller than it was before. Eventually it becomes cold forming a ‘Black Dwarf’.
Describe the life cycle of more massive stars.
- A large cloud of gas and dust contracts under its own gravity, heating as it goes, until it becomes a protostar.
- When the protostar is hot and dense enough, nuclear fussion begins. The star starts to shine and stabilises as a large main sequence star. A massive star might only remain like this for 10 million years
- When core hydrogen runs out, nuclear fusion stops and core collapse begins. As with a small star, this heats up a surrounding shell of hydrogen, and shell hydrogen burning begins.
- When the core heats up further and core helium burning begins, the star expands into a red supergiant.
- When core helium runs out, the core collapse process starts again. This time it heats until a heavier element is ignited in a shell and in the core. This cycle continues until the star is ready to collapse.
- Finally the star collapses extremely rapidly, creating a massive shockwave that blows the core apart in an explosion called a supernova.
- The explosion compresses the core of the star into a neutron star. This is an extremely dense object made up only of neutrons. If the star is massive enough, it become a black hole instead of a neutron star. The gravitational field of a black hole is so strong that nothing can escape from it. Not even light, or any other form of electromagnetic radiation.
What for es are acting on a rocket as it launches?
Force of the Earth on the rocket - gravity
Force of the gases on the rocket - thrust
What are satellites used for?
To look at the earth.
They send signals to earth.
They monitor weather.
What is a satellite?
An object that orbits another object. They could be made by humans or they could be natural.
What are the two types of satellite?
Natural
Artificial
How does a satellite stay in orbit?
A satellite maintains its orbit by balancing two factors: its velocity (the speed it takes to travel in a straight line) and the gravitational pull that Earth has on it.
Geostationary orbit:
Which part of the Earth does the satellite pass over?
How long does the satellite take to complete one orbit?
Does the satellite stay above the same point on the Earth all the time?
The equator
24 hours
Yes
Low polar orbit:
Which part of the Earth does the satellite pass over?
How long does the satellite take to complete one orbit?
Does the satellite stay above the same point on the Earth all the time?
The poles
Less than a day
No
Low Earth orbit:
Which part of the Earth does the satellite pass over?
How long does the satellite take to complete one orbit?
Does the satellite stay above the same point on the Earth all the time?
Anywhere
Less than a day
No
