P1- The Earth In The Universe

Question 1

Difference between stars an planets?

Answer 1

Stars are huge, very hot and very far away. They give out lots of light- which is why you can see them.

Planets are smaller and reflect sunlight falling on them. Planets are closer to us than any stars are. (Expect the sun)

Question 2

How did the Solar system form?

Answer 2

• The solar system formed over a very long period of time from big clouds of dust and gas.
• One cloud started to get slightly squeezed.
• The particles moved a bit closer to each other and gravity took over. It pulled things closer together until the whole cloud started to collapse in on itself.
• At the centre of the collapse, particles came together to form a protostar. When the temperature got high enough fusion started- hydrogen nuclei joined together to make helium.
• Fusion gives out massive amounts of heat and light. Thus our Sun was born.
• All of the chemical elements in the cloud with heavier atoms than helium and hydrogen were also formed in the stars by the fusion of different nuclei.
• Around the sun, materials form clouds containing hydrogen,helium and heavier elements started to clump together- these clumps formed planets.
• The oldest rock on the Earth are meteorites which tells us an estimate age for our Solar system- it has to be at least 4500 million years old.

Question 3

What are comets and asteroids?

Answer 3

Asteroids and comets are left overs from the formation of the solar system.

Asteroids are small lumps of rubble and rock.

Comets are balls of rock,dust and ice which orbit the Sun in an elongated ellipse.

As a comet approaches the sun, the ice melts leaving a bright tail of gas and debris which can be millions of kilometres long. We can see this from Earth.

Question 4

What is the Milky Way Galaxy?

Answer 4

Our sun is one of the thousand of millions of stars which form the Milky Way Galaxy.

The sun is half way along one of the spiral arms of the Milky Way Galaxy.

The distance between neighbouring stars in the Galaxy is usually millions of times greater than the distance between planets in the solar system.

Question 5

How many Galaxies are there?

Answer 5

Every Galaxy is made up of thousands of millions of stars and the universe is made up of thousands of millions of galaxies.

Galaxies themselves are often millions of times further apart than stars within a Galaxy.

The universe is mostly empty space which is really big.

Question 6

How close is the closest star to Earth?

Answer 6

The closest star to Earth is 40,000,000,000,000 kilometres away.

Question 7

What is a light year?

Answer 7

A light year is the distance that light travels through a vacuum (space) in one year.

Question 8

How fast does light travel?

Answer 8

Light travels at 300,000 km/s.

Question 9

Smallest to largest name the universe?

Answer 9

(Smallest to Largest)

• Diameter of the Earth
• Diameter of the Sun
• Diameter of the Earths orbit
• Diameter of the Solar system
• Diameter from the Sun to nearest star.
• Diameter of the Milky Way
• Distance from the Milky Way to the nearest Galaxy.

Question 10

How old is the Earth,Sun and Universe?

Answer 10

Earth- 5000 million years
Sun- 5000 million years
Universe- 14,000 million years

Question 11

What is the parallax method?

Answer 11

Astronomers take pictures of the sky 6 months apart (when the earth is at opposite ends of orbit)

The apparent movement of a star between the two photos lets you work out how far away it is.

Stars further away appear to move less.

Question 12

What is the brightness method?

Answer 12

To measure the distance of a star you measure its brightness.

However a star that looks bright from earth could be either;

• Close to earth but not actually that bright
• Far away but very bright

However astronomers know how much radiation certain types of stars actually emit. So by examining how bright they look from earth can tell how far away those stars must be.

Question 13

Why does light pollution cause problems?

Answer 13

The earths atmosphere absorbs the light coming from space before it can reach us.

Light pollution makes it hard to see dim objects.

This is why the Hubble space telescope is in space.

Question 14

How fast does electromagnetic radiation travel?

Answer 14

Electromagnetic radiation travels at about 300,000 km per second.

Since the sun is about 150 million km away from earth the radiation that comes from the sun that reaches us must have left about 8 minutes before we actually see it.

This means we see the sun as it was 8 minutes ago.

Light from the nearest star is seen a it was 4.2 years ago.

Question 15

What is the redshift?

Answer 15

When a galaxy is moving away from us the wavelength of the light from it changes- the light becomes redder. This is called red shift.

Question 16

What can we tell from the redshift?

Answer 16

The more distant a galaxy the faster it moves away from us.

The greater the red shift the faster it’s moving away.

Question 17

What is the Big Bang theory?

Answer 17

All the matter and energy in the universe must have been compressed into a very small space. Then it exploded and started expanding. The expansion is still going on now.

The age of the universe can be estimated from the current rate of the explosion. We think the Big Bang theory happened about 14 thousand million years ago.

Question 18

How will the world end?

Answer 18

The universes fate depends on how fast it’s expanding and the total mass there is in it.

You need to accurately observe the motion of objects. This is difficult because it’s far away so you have to assume their motion and pollution gets in the way.

Question 19

What is the Big Crunch?

Answer 19

If there’s enough mass compared to how fast the galaxies are currently moving, the universe will stop expanding.

Then begin contracting. This will end in a Big Crunch.

Question 20

Can the universe keep expanding?

Answer 20

If there’s not enough mass in the universe to stop the expansion it could expand forever.

The universe will spread more and more into eternity.

Question 21

How do rocks provide a record of changes in the Earth?

Answer 21

Erosion happens everywhere. Cliffs are worn away by sea. Fossils also provide evidence that rock is constantly forming.

The age of the earth can be estimated from rocks. The oldest rock is around 4 thousand million years old. So the earth is at least this old.

Question 22

What is the rock cycle?

Answer 22

• Particles eroded from existing rock get washed into the sea and settle as sediment.
• Over time, these sediments get crushed together to form sedimentary rocks.
• These can get pushed to the surface or can descend into the heat and pressure inside the Earth.
• If they descent, then the structure of the rock can change completely as it gets heated and crushed.
• The rock sometimes melts but solidifies into new rock if it cools near the Earths surface.
• When these rocks are pushed up to the surface, the cycle starts again.

Question 23

What were the observations about the Earth?

Answer 23

• Similar plants and animals have been found on opposite sides of the Atlantic Ocean.
• People though the continents had been linked by “land bridges” which ha sunk or been covered by water as the Earth cooled.

• People wondered why the coastlines of Africa and South America matched so well.
And why fossils from sea creatures had been found high in the Alps.

Question 24

What did Alfred Wegener observe?

Answer 24

Alfred Wegener hypothesised that Africa and South America had previously been one continent which had split.

Question 25

What was Wegener’s evidence?

Answer 25

• There were matching layers in the rocks on different continents.
• And similar fossil in both South America and South Africa.
• Wegener’s theory of “the continental drift” supposed that about 300 million years ago there had been just one “supercontinent”- which he called Pangaea.
• According to Wegener Pangaea broke into smaller chunks and these chunks (continents) are slowly drifting apart.

Question 26

Why was Wegener’s theory not accepted at first?

Answer 26

• Wegener’s theory explained the “land bridges” theory- like mountain building.
• However, Wegener’s explanation of how the “drifting” happened wasn’t convincing. As the movement wasn’t detectable.
• Wegener claimed that the continents movement could be caused by tidal forces and the earths rotation. But geologists said this was impossible.
• Wegener himself was not a geologist he was a meteorologist. So his theory wasn’t as respected.

Question 27

Wegener’s theory had solid evidence?

Answer 27

• In 1950s scientists investigated the mid Atlantic ridge which runs through the whole of the Atlantic.
• They found evidence that magma rises up through the sea floor,solidifies and forms underwater mountains that are roughly symmetrical either side of the ridge.
• The evidence suggested the seafloor was spreading a few cm per year.
• Evidence also suggested that the continents are moving apart came from the magnetic orientation of the rocks.
• As the liquid magma erupts from the gap, iron particles in the rock align themselves with the Earths magnetic field. Because as they cool they set in position.
• Every half million years or so the Earths magnetic field swaps direction.
• And the rocks on either side of the ridge has bands of alternate magnetic polarity, symmetrical about the ridges.
• This was evidence that new sea floor was being created. And that continents were moving apart.

Question 28

How is the earth structured?

Answer 28

• The earth is almost spherical and has a layered structure.
• The crust is very thin (20km). There are 2 types of crust;
• Continental crust- forming the land.
• Oceanic crust- under oceans.
• Below the crust is the mantle- which has the properties of a solid but can flow very slowly.
• Heat from the core and heat from radioactive decay in the mantle causes the mantle to flow in convection currents.
• Then it’s the liquid outer core.
• And then at the centre of Earth is the core- which is made of iron and nickel.

Question 29

What are tectonic plates?

Answer 29

The crust and upper part of the mantle are cracked into a number of large pieces called tectonic plates.

convections currents in the mantle caused by heating in the core and mantle cause the plates to drift. The movement in the mantle causes the seafloor to spread a few cm.

Question 30

How do tectonic plates cause earthquakes?

Answer 30

When the plates move suddenly it causes an earthquake. Earthquakes happen more often near the edges of the plates.

Question 31

How do tectonic plates cause volcanoes?

Answer 31

Volcanoes form at the boundaries between two tectonic plates. Where plates meet magma is produced which rises up forming volcanoes.

Question 32

How do tectonic plates cause mountains?

Answer 32

As plates crash into each other mountains form.

These processes contribute to the rock cycle.

Question 33

What are shock waves?

Answer 33

When there’s an earthquake it produces wave motions (shock waves) which travel on the surface and inside the Earth.

We record these seismic waves all over the surface of the planet using seismographs.

Seismologists measure the time it takes for the shock waves to reach each seismographs. They note which part of the Earth don’t have shock waves.

Question 34

What are P waves?

Answer 34

• P waves travel through solids and liquids.
• They travel faster then S waves.
• P waves are longitudinal.

Question 35

What are S waves?

Answer 35

• S waves only travel through solids.
• They are slower then P waves.
• S waves are transverse.

Question 36

Why do shock waves curve?

Answer 36

When seismic waves reach a boundary between different layers of the earth some waves will be reflected.

The waves also change speed as the properties of the mantle and core change. This change in speed causes the waves to change direction- which is a refraction.

The wave change speed gradually resulting in a curved path.

Question 37

What do seismograph results tell us?

Answer 37

Halfway through the Earth P waves change direction abruptly. This indicates that there is a sudden change in properties.

The fact that S waves are not detected in the cores shadow tells us that the outer core is liquid.

P waves travel slightly faster through the middle of the core which suggests there is a solid inner core.

Question 38

Facts about waves?

Answer 38

• All waves are disturbances caused by a vibrating source.
• They carry and transfer energy in the direction the wave travels.
• They do not transfer matter.
• The amplitude is the distance from the rest position to the crest or trough. The bigger amplitude means more energy the wave has.
• The wavelength is the length of the full cycle.
• Frequency is the number of complete waves passing a certain point per second. Or the number of waves produced by the source each second.
• Frequency is measured in Hz. 1 Hz is 1 wave per second.

Question 39

Formula for speed,distance and time?

Answer 39

Distance (m) = speed (m/s) * time(s)

Question 40

What is a transverse wave?

Answer 40

In transverse waves the vibrations are at 90 degrees to the direction of travel of the wave.

Question 41

What is a longitudinal wave?

Answer 41

In longitudinal waves the vibrations are along the same directions as the wave is travelling.

Question 42

How do you work out speed?

Answer 42

Speed (m/s) = frequency (Hz) * wavelength (m)

Question 43

What orbits the Sun?

Answer 43

There are 8 planets orbiting the Sun in an ellipse.

The inner planets are; Mercury, Venus, Earth and Mars.

Then there’s and asteroid belt.

Then there’s the outer planets; Jupiter, Saturn, Uranus and Neptune.