P1 Flashcards
When was the universe formed?
5 billion years ago
What is the Earth’s diameter?
13’000 km
What is the sun’s diameter?
1’400’000 km
What is the distance to the nearest star?
4.2 light years
What is the distance to the nearest galaxy?
2’300’000 km
Where does our evidence of distant stars and galaxies come from?
Radiation astronomers collect
How fast does light travel?
300’000 km/s
What is a light year?
The distance light travels in a year
How can you measure the distance of star using the parallax effect?
Look at how far a nearby star moves against fixed stars in a specific time such as 6 months
How can you measure the distance of a star using its relative brightness?
Two stars have the same real brightness.
They can have different relative brightnesses.
If you know the distance of one of the stars.
The difference in their relative brightness can be used to calculate the distance to the other one.
Why are there uncertainties in measuring the distance to stars?
- It is based on the assumption that similar types of stars have the same relative brightness
- It is based on estimating the distance to one of the stars
- Dust, rain, clouds and light pollution can make it difficult to measure stars at night
Where does the sun get its energy from?
Nuclear Fusion
What happens in Nuclear Fusion?
Hydrogen nuclei are jammed together so hard that they combine in pairs to form the element Helium, this process releases loads of energy
What chemicals were made in stars?
All chemical elements with atoms heavier than helium
How are the rest of the chemicals made?
Nuclear fusion can make elements as heavy as hydrogen with right enough densities. At the end of a star when it explodes during a supernova.
Why is the fate of the universe difficult to predict?
We can only measure the mass of those parts in the universe which emit radiation
Precise measurements of the speed and distances of galaxies is difficult their radiation travels such a long way to get to us
How do rocks provide evidence for the changes in Earth?
Erosion, sedimentation, fossils and folding
What stops continents being worn down to sea level?
Mountains being continuously formed
How can we see the past of the Earth?
Through its rocks and and the different layers in them
How can the age of the Earth be estimated?
From its oldest rocks which are 4000 million years old
What was the evidence for Wegners theory of continental drift?
Continents fit well together like a jigsaw
Similar fossils and rocks are found on continents now separated by oceans
Matching rock formations and mountain chains found on different continents
How does Wegener’s theory explain the folding of rock into mountain ranges
Collisions between moving continents
Why was Wegener’s theory rejected?
There was already similar explantations for some of his observations
Nobody could explain or measure the movements of the continents
Wegener was not a geologist
It was too big of an idea from limited evidence
What is sea floor spreading caused by?
It is caused by continents moving because they sit on on the mantle, whose rocks move slowly by connection as they carry heat away from the Earths hot core
How much does the sea floor spread by each year?
A few centimetres
Why is there a pattern of magnetisation of sea floor rocks on other side of the oceanic ridges
Oceanic ridges from the expanding seafloor where liquid rock from the mantle fills the gap
The solidifying rock in the oceanic ridge is magnetised by the Earths field
The Earths magnetic field changes direction over millions of years
Each time the Earths field reverses, so does the magnetisation of the oceanic ridges
So the seafloor has strips of reversed magnetism parallel to where new rock is created
How do volcanoes occur?
When liquid magma of forced through cracks where tectonic plates are moving apart
How do volcanic mountains occur?
When on tectonic plate if forced under another heading towards it
How do fold mountains occur?
When two tectonic plates meet head on
How do Earthquakes occur?
Earthquakes are a release of energy form tectonic plates sliding past each other
What are P waves?
They move quickly through solid crust and liquid core they are longitudinal which mean the particles vibrate along the direction of the motion of the wave.
What are S waves?
They only move through the solid crust an are transverse so the the particles vibrate at right angles to the direction of motion of the wave
What is a wave?
A wave a disturbance caused by a vibrating source that transfers energy in the direction that the wave travels without transferring matter
What is the frequency of waves?
Number of waves that are made by the source each second or how many pass through are particular point
What is the height of the wave called?
Amplitude
What is the distance called between two ripples of a wave?
Wavelength
