The Universe Flashcards
Explain what is meant by “red-shifted” galaxies.
Scientists can use absorption spectra to examine which chemicals compose different planets and stars, but they can also be used to determine how quickly a galaxy is moving away from Earth.
Different chemicals absorb different waves of light. Red light waves have the lowest frequency and the longest wavelength. Galaxies that absorb red light waves more are red-shifted galaxies - they appear to be moving away from us. The more distant a galaxy is, the more red-shifted it is, and thus the faster it appears to be moving away from us.
How does the red shift help evidence the Big Bang?
The Big Bang Theory asserts that the universe must constantly be expanding. The red shift helps to support this as it shows how galaxies appear to be moving away from Earth, and the more distant a galaxy is, the faster it appears to be moving away. This supports the idea that the universe is constantly expanding, as it shows how galaxies appear to be moving away when in reality, this occurs due to a constantly expanding universe.
What are two pieces of evidence for the Big Bang?
- The Red Shift.
- Cosmic Microwave Background Radiation
How does Cosmic Microwave Background Radiation?
Scientists discovered that there was microwave radiation coming from all directions. They worked out that this was radiation left over from the Big Bang. The very high energy and frequency radiation has been stretched over time, so it is now in the microwave section of the electromagnetic spectrum.
What did Edwin Hubble discover?
That by measuring the speed of galaxies through absorption spectra, we can tell that galaxies are moving away as the universe constantly expands.
How do scientists believe the universe began?
The universe was a very small, hot and dense region around 13.8 billion years ago. After the Big Bang occurred, this eegion expanded into the universe we exist in today.
Outline how the universe was formed.
- The universe was a small, hot and dense region around 13.8 billion years ago.
- The Big Bang occurs.
- Protons and neutrons form.
- Protons and neutrons come together to form simple elements.
- The radiation of the universe occurs. It is filled with very high frequency electromagnetic radiation.
- Temperature cools and electrons are able to bond with nuclei and form neutral atoms.
- Stars are born.
What kinds of seismic waves are there?
Primary and Secondary.
What are the properties of P waves?
- They are longitudinal
- They are able to travel through both solids and liquids
- They travel faster than S waves, so are detected first.
What are the properties of S waves?
- They are transverse
- They are only able to travel through solids
How are S waves shadow zones formed?
When S waves travel through the Earth, they are unable to travel through the Earth’s liquid outer core. This results in large areas where S waves go undetected called S waves shadow zones.
How are P wave shadow zones formed?
P wave shadow zones are due to the fact that P waves travel faster in solids than they do in liquids, so when they travel through the Earth’s liquid outer core, the waves are refracted (made to change direction.) This results in larger areas where P waves are undetected by seisometers called P wave shadow zones.
What can scientists use to assert that the Earth has a solid inner core?
Sometimes, faint P waves can be detected in P wave shadow zones. This is because although the liquid inner core refracts the majority of P waves, the few that pass through the solid inner go are not refracted and so are able to be detected in shadow zones.
Why do seismic waves travel in curved paths?
They do so due to density changes in the Earth distorting their paths.
What are seismic waves measured by?
A seisometer. Who could’ve guessed.
Which state of matter is the mantle?
It’s a solid, technically.
How do all stars begin?
As a cloud of dust and gas called a nebula. Gravity causes the cloud to collapse, and as the particles move faster, the temperature rises to millions of degrees Celsius, forming a protostar.
If the temperature rises high enough, then hydrogen should join together to form helium nuclei in nuclear fusion. This forms a main sequence star.
Give the names of the stages of a life cycle belonging to star bigger than our sun.
Nebula -> Protostar -> Main sequence star -> Red supergiant -> Supernova -> Either a black hole or a neutron star
Outline how a main sequence star is formed.
All stars begin as clouds of dust and gas called nebula. Gravity eventually causes the cloud to collapse, which results in particles moving much faster and the temperature thus rising to millions of degrees Celsius, forming a protostar.
In the protostar, nuclear fusion occurs as hydrogen atoms fuse together to form helium atoms. This releases huge amounts of energy and forms a main sequence star.
Explain how a main sequence star will reach the stage of a Black Dwarf.
The Main sequence star is about the same size of our Sun, it will go on to form a Black Dwarf, the final stage in its life cycle. Hydrogen needed for nuclear fusion in the star will run out, causing the outward force (energy released by fusion) to be less than the inward force of gravity. This causes the star to collapse inwards.
The collapse of the star causes its temperature to increase. Helium nuclei will fuse together to form heavier elements. The star at this stage will be a Red Giant.
However, the star will eventually stop fusing helium and shrink to form a White Dwarf. As fusionis no longer being performed, the star will no longer release any energy, forming a Black Dwarf.
Give the names of the stages of a life cycle belonging to a star the size of our sun.
Nebula -> Protostar -> Main sequence star -> Red Giant -> White Dwarf -> Black Dwarf
What is a black hole?
An object so dense that not even light can escape from it.
Explain how a star could become a supernova.
Stars larger than our sun form red supergiants after the main sequence star stage, due to nuclear fusion between helium atoms resulting in the formation of heavier elements and thus expanding the star to a massive size. When this star stops carrying out fusion, it will explode, forming a supernova. In a supernova, the temperature is high enough to produce elements heavier than iron in nuclear fusion.
What kind of orbits does the Earth virtually have around the Sun?
A circular orbit.
What is an orbit?
The curved path of one celestial object around another celestial object.
What are the two kinds of orbit used by artifical satellites?
Low Polar Orbit and Geostationary Orbit.
Describe the differences between geostationary Orbit and Low Polar Orbit.
Geostationary Orbit:
- Takes 24 hours to complete one Orbit. This means that it is in a fixed positions above the Earth’s equator.
- About 36000 km above the Earth’s surface.
- Used for communications and TV.
Low Polar Orbit:
- Takes 2 hours to complete one orbit.
- Orbits around the poles.
- Orbits at around 2000 km above the Earth’s surface.
- Used for spying and the weather.
If the speed of an orbit increases, what happens to its radius?
As the speed of an orbit increases, the radius of the orbit must decrease. This is because objects travelling at a greater speed require a greater force of gravity to keep them i their orbit and prevent them from flying off into space.
Which way does the force of gravity act in an orbit?
It acts inwards, towards the centre of the planet.
Calculate the orbital speed of an geostationary satellite at a distance of 42 160 km from Earth.
42 160 ÷ 24 = 1,756.6666666667 km per hour
Explain why geostationary orbits cannot be above the UK.
The UK is not on the equator of the Earth, meaning a geostationary satellite will not orbit above it.
Describe what is meant by a black body radiator.
A black body is the hypothetical perfect absorber and radiator of energy, with no reflecting power.
Give three factors that the temperature of the Earth depends on.
- The rate of absorption of radiation from the Sun.
- The rate of emission of radiation.
- The amount of radiation that is reflected back into space.
Why do very hot objects turn different colours? What must happen for an object to turn white-hot?
Very hot objects turn different colours as the hotter an object gets the more higher-frequency radiation it emits, resulting in portions of the spectrum of visible light to be shown.
A white-hot object is an object with a temperature that has increased so high that it is emitting radiation with an incredibly short wavelength and high frequency, crossing over into emitting ultraviolet waves.
