P1 - The Earth in the Universe Flashcards
What is the Solar System made up of?
- EIGHT Planets (including Earth) that orbit the sun in elliptical orbits.
- Moons - small masses that orbit the planets.
- Asteroids - small, rocky masses that orbit the Sun.
- Comets - small, icy masses that orbit the Sun.
- Dwarf planets - Small spherical objects that have not cleared their orbits of other objects.
How old is the Solar System?
4.6 billion years old.
How was the Solar System formed?
- Started as clouds of DUST and GAS, which were pulled together by the FORCE OF GRAVITY until the whole cloud started to collapse in itself.
- At the centre of the collapse, particles came together to form a protostar. When temperature got high enough, NUCLEAR FUSION started. This made the Sun.
- The remaining dust and gas formed smaller masses, which were attracted to the Sun.
In general, how many galaxies are roughly present? How many stars do they contain?
Thousands of millions of galaxies, each containing thousands of millions of stars of stars (The Sun is one of the stars in the Milky Way). All of these galaxies make up the Universe.
From smallest to largest, recall the relative sizes of objects within the Universe.
- Diameter of the Earth
- Diameter of the Sun
- Diameter of the Earth’s orbit
- Diameter of the Solar System
- Diameter from the Sun to the nearest star.
- Diameter of the Milky Way
- Diameter of the Milky Way to the nearest galaxy.
Where does all the evidence that we have about distant stars come from?
The RADIATION astronomers can detect.
A lot is shown when studying Electromagnetic Radiation it emits, e.g. the colour the star appears shows its surface temperature.
Light travels at very ____ but ____ speeds.
Light travels at very HIGH but FINITE speeds.
What is the speed of light in km/s IN A VACUUM?
300 000 km/s
What is the unit that measures vast distances in space?
LIGHT YEARS (ly)
What is a light year?
The distance light travels in one year ( 9500 billion km)
What does the finite speed of light mean?
That very distant objects are observed as they were in the past, when we the light we see now left them.
What are the two methods that astronomers use to work out the distance to different STARS?
- Relative Brightness
2. Parallax
What is Relative Brightness?
The dimmer a star is, the further away it is.
However stars can vary in brightness so we’re not 100% certain
What is Parallax?
When something appears to move when you look at it from different positions.
How long does it take to measure the two different positions of an object in parallax?
6 Months
What is the issue of Parallax with very distant stars?
The further away the star is, the more difficult and less accurate the measurement is.
What can interfere with the observations of the night sky?
- LIGHT POLLUTION
2. ATMOSPHERE
Why did scientists put the Hubble Space Telescope in space?
To avoid certain problems such as light pollution and other atmospheric conditions.
Where does the Sun’s energy come from?
NUCLEAR FUSION - Hydrogen fuse together to make helium (a heavier nuclei).
All chemical elements with a larger mass than helium were formed by…..?
All chemical elements with a larger mass than helium were formed by NUCLEAR FUSION IN EARLIER STARS.
When a galaxy is moving away from us, what happens to the wavelength? What is this motion called?
The wavelength of the light from it changes. The light becomes REDDER because the light has SHIFTED to the red-end of the Electromagnetic Spectrum.
This is called RED-SHIFT.
By seeing how much light has been red-shifted, what can we work out?
How quickly a galaxy is moving away from us.
The _______ the red-shift, the ______ it’s moving away from us.
The GREATER the redshift, the FASTER a galaxy is moving away from us.
The more ______ the galaxy, the _____ it’s moving away from us.
The more DISTANT the galaxy, the FASTER it moves away from us.
Because galaxies are moving away from us, what evidence does this provide in terms of the Universe?
This provides evidence that the whole Universe is expanding.
From youngest to oldest, rank the ages of the Earth, Sun and the Universe.
- Earth (4500 million yrs)
- Sun (5000 million yrs)
- Universe (14 000 million yrs)
What do scientists believe happened when the Universe was born? Why do they think this?
The Universe started with a huge explosion. This is because the fact that galaxies are moving away, they must’ve moved from a single point.
What does the Universe’s ultimate fate depend on (2) ?
- How fast it’s expanding.
2. The total mass there is in it.
If there is enough mass compared to how fast the galaxies are currently moving, the Universe will eventually….?
The Universe will eventually STOP EXPANDING and then BEGIN CONTRACTING. This is called the BIG CRUNCH!
If there is not enough mass in the Universe to stop the expansion, the Universe will….?
The Universe will keep expanding.
Why is it difficult to predict the fate of the Universe?
- We can only measure the mass of those parts of the Universe which emit RADIATION.
- Precise measurements of the speed and distance of the galaxies is difficult because their radiation travels such a LONG WAY to get to us.
What are the 4 types of evidence that rocks provide for the change of the Earth?
- EROSION
- SEDIMENTATION
- FOSSILS
- FOLDING
What is erosion?
The changing of the surface of the planet over long periods of time. Material erodes slowly from mountains and becomes sediments which make rocks.
What is sedimentation?
When eroded rocks fragments are transported by the wind, water and ice, broken up further, and deposited on riverbeds and in the sea.
How are sedimentary rocks formed?
Over millions of years, the sediments are crushed together to form layers of sedimentary rocks.
What does the build-up of sedimentary rock layers eventually lead to?
Makes seas shallower.
How can the age of the Earth be estimated?
From, and must be greater than, the age of its oldest rocks, which are 4000-4500 million years old.
If no new rocks had been created, what would happen to the erosion?
The erosion for that length of time would have worn all of the continents down to sea level.
What do breaks in the Earth’s crust allow to happen?
Allows molten rock to escape from volcanoes and create new mountains.
What is another way of making new mountains, other than molten rock?
Collisions between different parts of the crust also push rocks up to make new mountains.
Who is Alfred Wegener and what theory did he come up with?
Alfred Wegener was a polar researcher, geophysicist and meteorologist.
In 1915, he came up with the theory of CONTINENTAL DRIFT.
What did the Theory of Continental Drift explain?
That millions of years ago, there was a single landmass on Earth, Since then it has split into several continents which have drifted apart.
What were 2 pieces of evidence that Wegener’s theory was based on?
- The way continents fit together so well
2. Similar fossils and rocks are found on continents now separated by oceans.
What explains the folding of rocks into mountains?
Collisions between moving continents
What were 3 reasons as to why geologists did not accept Wegener’s theory?
- They already had other, simpler theories which explained some of his observations.
- Nobody could explain or measure the movement of the continents.
- Wegener was not a trained geologist and his theory was very different from the others.
- Too big an idea from limited evidence
Why do continents move?
Because they sit on the mantle, whose rocks move slowly by convection as they carry heat away from the Earth’s hot core.
What is seafloor spreading?
When seafloors between continents move apart.
They can increase by a few centimetres each year.
Where do oceanic ridges form?
They form on the expanding seafloor where liquid rock from the mantle fills the gap.
What is the solidifying rock in the oceanic ridges magnetised by?
The Earth’s magnetic field.
What happens to the magnetisation of the oceanic ridges as the Earth’s field reverses?
The magnetation of the oceanic ridges ALSO reverses.
What does the seafloor contain in terms of magnetism?
The seafloor has strips of reversed magnetism PARALLEL to the gap where new rock is created.
What do solid tectonic plates within the Earth’s crust float on?
Semi-solid rocks
Where do tectonic plates meet at?
At a PLATE BOUNDARY.
What generally occurs at the edge of plate boundaries?
Earthquakes, volcanoes and mountains.
How do volcanoes occur?
When liquid MAGMA is forced through cracks where tectonic plates are moving apart.
How do volcanic MOUNTAINS form?
When one tectonic plate is FORCED under another heading towards it.
How do FOLD MOUNTAINS form?
When two tectonic plates meet head-on.
What are earthquakes?
Releases of energy from tectonic plates sliding past from each other.
What is the rock cycle explained by?
The movement of tectonic plates.
What is the core of the Earth mostly made out of?
Liquid iron.
What floats within the mantle ON THE CORE?
Semi-liquid rocks.
What is the outer core a layer of?
How thick is the outer core?
Liquid nickel and iron.
It’s 2200 km thick.
What is the inner core made out of?
How thick is the inner core?
Solid nickel and iron.
It’s 1250 km thick.
What is within the crust that floats on the mantle?
A thin layer of solid rock.
What are the two types of seismic waves?
P-waves
S-waves
What are the 2 features of P-waves?
- P-waves are LONGITUDINAL, meaning that particles vibrate ALONG the direction of motion of the wave.
- They move quickly through solid crust and liquid core.
What are the 2 features of S-waves?
- S-waves are TRANSVERSE, meaning that particles vibrate at RIGHT ANGLES to the direction of motion of the wave.
- They move slowly through the solid crust.
What is the name of the device that we can use to record P-waves and S-waves after an earthquake?
Seismometers
What happens to seismic waves when they enter denser regions of the Earth’s core?
They SPEED UP and CHANGE DIRECTION.
What state (solid/liquid/gas) must the core of the Earth be?
Liquid - because P-waves pass through it.
What is a wave?
A disturbance, caused by a vibrating force, that transfers energy in the direction that a wave travels, without transferring matter.
What is the Frequency (of a wave) ?
The number of waves each second that are made by the source, or that pass through at any particular point.
What is Frequency measured in?
Hertz (Hz)
1 Hz = 1 vibration per second
What is the wavelength of waves?
The distance between the corresponding points on TWO ADJACENT CYCLES.
What is the amplitude of a wave?
The distance from its maximum displacement to the undisturbed definition.
What is an oscilloscope?
A machine that displays waves on a screen.
What does the grid on the screen of an oscilloscope allow you to compare?
The wavelength and the amplitude of waves.
A sound is LOUDER if it has….?
A LARGER amplitude
A sound is HIGHER PITCHED if it has…?
A SHORTER wavelength
What is the scale on an oscilloscope used to measure?
The wavelengths, in metres, or to measure amplitude.
What is the wave equation that waves obey?
wave speed (m/s) = frequency (Hz) x wavelength (m)
The HIGHER the frequency, the ______ the wavelength.
The HIGHER the frequency, the SHORTER the wavelength.
The wavelength is always _______ proportional to the frequency.
The wavelength is always INVERSELY PROPORTIONAL to the frequency.
