12/04/23Junior Cycle Junior Cycle Physics Physics

The Earth and Beyond

Edited and Reproduced by

Theresa Lowry-LehnenRGN, BSc (Hon’s) Specialist Clinical Practitioner (Nursing), Dip Counselling, Dip Adv Psychotherapy,

BSc (Hon’s) Clinical Science, PGCE (QTS) , H. Dip. Ed, MEd, Emotional Intelligence (Level 9) MHS Accredited

12/04/23There are nine planets in our solar There are nine planets in our solar system:system:

Mercury

MarsJupiter

Saturn

Neptune

Uranus

Pluto

VenusEarth

My Very Easy Method Just Speeds Up Naming

Planets

12/04/23

We see planets and the moon because they reflect sunlight:

The sun is different – it produces its own light.

12/04/23The Earth orbits the sun…The Earth orbits the sun………every year (365 every year (365 11//44

days)days)

Ellipse

12/04/23

The Earth is kept in orbit by 2 things…The Earth is kept in orbit by 2 things…

GravityGravity

…and by the fact that it is moving at a high velocity

12/04/23

The Earth spins on an axis…

Because of this spin the sun and stars appear to

“move” across the sky…

12/04/23

GravityGravityGravity is an attractive force that affects anything with mass:

Note that this force goes both ways – the Earth

is attracted to us.

12/04/23Gravity on different Gravity on different

planets:planets:

Jupiter – gravitational field strength = 25N/Kg

Earth – gravitational field strength = 9.8N/Kg

12/04/23More information on gravityMore information on gravity

F

F/9

F/4

If you double the distance the

gravitational force divides by 4…

If you triple the distance the force

divides by 9…

The amount of gravity attracting an object decreases the further out the object is…

12/04/23How much of the moon we see How much of the moon we see depends on where the moon is in depends on where the moon is in

its orbit:its orbit:

Appearance:

12/04/23

Appearance:

12/04/23

Appearance:

12/04/23CometsCometsComets are balls of dust and frozen gas. They have very elliptical orbits:

As the comet approaches the sun gases evaporate from it, forming a “tail”. This tail always faces AWAY from the sun.

12/04/23

Artificial SatellitesArtificial Satellites

Geostationary orbits:

Low polar orbits:

12/04/23Artificial SatellitesArtificial Satellites

1) Observation (e.g. Hubble Space Telescope) – these are in orbit high above the Earth and can observe the universe without interference by the ____________

2) Communications (e.g. ___, phone, car “SatNav” systems) – these satellites are in “geostationary” orbits. This means that the satellite always stays above ____ ____ point on the Earth and takes a ______ to complete an orbit

3) Monitoring (e.g. weather, spy satellites) – these satellites have a “___ _____” orbit and may scan around the Earth several times a day

Artificial satellites have been around for 50 years and have 3 main uses:

Words – the same, atmosphere, low polar, TV, day

12/04/23Solar systems, galaxies and the Solar systems, galaxies and the UniverseUniverse

OUR SUN is one of millions of stars that orbit the centre of…

THE MILKY WAY, which is one of a billion galaxies that orbit AND move away from the centre of…

THE UNIVERSE

(Basically, everything in the universe orbits around something else)

12/04/23Quiz..Quiz..1) What is the sixth planet in the solar system?

2) What is the biggest planet in the solar system?

3) Name 2 differences between stars and planets

4) How long does the Earth take to orbit the sun?

5) What 2 things keeps the Earth in orbit?

6) Why does Mars take longer to orbit the sun than Earth?

7) How long does the moon take to orbit the Earth?

8) Would the acceleration due to gravity on Mars be bigger or smaller than on the Earth and why?

9) Which hemisphere is Britain in?

12/04/23Quiz..Quiz..

10)What is the name of the line that divides the two hemispheres?

11)How long does the Earth take to rotate?

12)Where does the sun rise and set?

13)If you double the distance between two objects what happens to the force of gravity between them?

14)What shape describes the shape of a comet’s orbit?

15)What is a comet made up of?

16)Where does a comet’s tail point and why?

17)What keeps stars in orbit around the centre of a galaxy?

12/04/23

Searching for ETSearching for ETIn any scientific enquiry you have to OBTAIN some evidence and then ANALYSE it. Consider searching for extra-terrestrial life on Mars:

OBTAINING EVIDENCE

•Fly to Mars yourself (takes ages)

•Use robots to bring back samples (not very reliable)

•Use robots to take pictures and send them back (also not very reliable)

ANALYSING EVIDENCE

•Use microscopes to search for fossilised remains inside the samples

•Place the sample in a container and monitor changes in the environment due to living organisms being present in the sample

12/04/23

Evidence about the Evidence about the origins of the universe…origins of the universe…

12/04/23

Source of light “Spectra

”

12/04/23

If you pass the light through a gas something different is seen…

helium

Some wavelengths of light are absorbed by

the gas – an “absorption spectrum”.

12/04/23

After

helium

If the light source is moving away the absorption spectra look a little different…

helium

Before

12/04/23The absorption lines have all been “shifted” towards the longer wavelength end (red end)…

After

BeforeThis is called red

shift. The faster the light source moves the further its light will be “shifted”

A similar effect happens with sound – this is called “The

Doppler Effect”Hear Doppler Effect

12/04/23Light from different stars and from the edge of the universe also shows this “red-shift”. This suggests that everything in the universe is moving away from a single point.

This is the BIG BANG theory

12/04/23

Red shift summaryRed shift summaryLight from other galaxies has a longer _________ than expected. This shows that these galaxies are moving ____ from us very quickly. This effect is seen to a greater extent in galaxies that are _______ away from us. This indicates that the further away the galaxy is, the ______ it is moving.

This evidence seems to suggest that everything in the universe is moving away from a single point, and that this process started around 15 _____ years ago. This is the ____ ________ Theory.

Words to use – faster, away, big bang, billion, wavelength, further

12/04/23

The Life Cycle of a StarThe Life Cycle of a Star

12/04/23

Stage 1: NebulaeStage 1: Nebulae

A nebulae is a collection of dust, gas and rock.

Some examples of nebulae…

12/04/23

Dark nebula

12/04/23

Emission nebula

12/04/23

Planetary nebula

12/04/23

Reflection nebula

12/04/23

Gravity will slowly pull these particles together…

As they move inwards their gravitational potential energy is converted into heat and a PROTOSTAR is formed

Stage 2: ProtostarStage 2: Protostar

12/04/23Stage 3: Main SequenceStage 3: Main Sequence

Our sun is an example of a main sequence star – it’s in the middle of a 10 billion year life

span

In a main sequence star the forces of attraction pulling the particles inwards are _________ by forces acting outwards due to the huge __________ inside the star.

Stars are basically ________ reactors that use _______ as a fuel. During its main sequence a star will release energy by converting hydrogen and helium (light elements) into _________ elements.

Words – heavier, balanced, hydrogen, nuclear, temperatures

12/04/23

Eventually the hydrogen and helium will run out. When this happens the star will become colder and redder and start to swell…

If the star is relatively small (like our sun) the star

will become a RED GIANT

If the star is big (at least 4 times the size

of our sun) it will become a RED SUPERGIANT

Stage 4: Red GiantStage 4: Red Giant

12/04/23

What happens at this point depends on the size of the star…

1) For SMALL stars the red giant will collapse under its own gravity and form a very dense white dwarf:

Stage 5: The DeathStage 5: The Death

White dwarf

Black dwarf

Red giant

12/04/232) If the star was a RED SUPERGIANT it will shrink and then EXPLODE, releasing massive amounts of energy, dust and gas.

AfterBefore

This explosion is called a

SUPERNOVA

12/04/23The dust and gas on the outside of the supernova are thrown away by the explosion and the remaining core turns into a NEUTRON STAR.

If the star is big enough it could become a BLACK HOLE.

12/04/23

The dust and gas thrown out by a supernova can be used to form a new star…

Stage 6: Second generation Stage 6: Second generation starsstars

Our sun is believed to be a “______ ______ star” – this is because it contains some __________ elements along with hydrogen and ________. These heavier elements would have been the products of a previous star that have been thrown out by a ________. These heavier elements are also found on planets, indicating that they might have been made from remains of previous _______ as well.

Words – helium, heavier, second generation, stars, supernova