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Level 3 Applied Science

UNIT 16:

Astronomy and Space

Science

PHYSICS SECTION

Coursework

Booklet 3

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Astronomy and space science

Learning aim C – Investigate the essential factors involved in space travel.

Learning aim D – Understand the fundamental concepts outlined in astrophysics

and cosmology.

Pass criteria

1. Comprehensive list of what factors need to be considered to achieve space flight.

Materials

Fuels

Escape velocity

Hazards

Costs

Communication

Effects on humans (case study required from Apollo missions)

2. Evolution of the Universe

Outline the aspects of size, temperature, and luminosity of stars using Hertz Sprung Russel diagram.

Dependence of a star life cycle on the initial mass of the star in relation to the Sun. (D)

Notes will accompany each of these stages.

Description of the principles of redshift and cosmic microwave background radiation linked to the

theory of the Big Bang.

Details and measurements in the Universe will enhance descriptions of the Universe’s evolution –

galaxies, nebula, supernovae, and distances will be included here.

Merit criteria

3. Well worded report on the products discovered or developed because of space flight.

At least five products from materials to manufacturing.

4. General outlines of work carried out by astronauts.

Must be researched based and linked to areas of science and industry.

Presented as a list or table.

Includes a description and indication of its relevance to society in general.

Independently worked, includes researched evidence and correctly referenced in a bibliography.

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5. The effects of space flight on the body and the implications of long-term space flight presented as a

large poster with a diagram of the human body with clear labels of the areas affected.

Radiation exposure, micro-gravity environment, astronauts in constant free-fall, psychological and

physics effects.

Description of long-term space flight problems: osteoporosis, change in blood flow, drop in blood

plasms levels.

What can be done to limit these long-term space flight problems?

6. Physics aspects of achieving space flight for a vehicle.

Explanations based on known launch and flight data.

Explanation on how an object achieves escape velocity and maintains orbit.

Calculations of escape velocity of Earth.

Acknowledgements of the dangers involved referring to Salyut 1, Apollo 1, Challenger and Columbia

Space Shuttles.

7. Details of the Hertz Sprung Russel diagram.

Relevant stars named – red giants, white dwarfs.???????????

Description of how stars are formed in terms of pressure balance and imbalance, development of

protostars, to main sequence and the eventual end (D)

8. Theories of evolution

Explanation of the theory of evolution.

Must involve information about galaxy movements, star formation/destruction, age of the Universe

and further detail regarding redshift and CMBR.

Distinction criteria

9. History of space flight and difficulties involved.

Detailed report.

Includes a good selection of planned missions, manned and un-manned which have proposed by

various countries and organisations.

Presented as a journal with clear descriptions of proposals and evaluations of the developments of

each space programme in terms of cost, difficulties that will be faced, benefits, and implications.

Link to the current understanding of the Universe – its origin, dynamic nature, and theoretical future.

10. Is life unique?

Discussion to whether life on Earth is unique.

Demonstrate clear thought on the probability of life being found elsewhere in the Universe.

Problems associated with space travel beyond the confines of the inner solar system.

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1. What is required to achieve space flight?

THIS ASSIGNMENT ON SPACEFLIGHT MUST BE WRITTEN AS A REPORT!

A spacecraft is a vehicle designed to fly into outer space. In order to build a space craft, factors such as choice of

materials, fuels and cost – to name a few, have to be considered.

1.1 Materials

The International Space Station is made from the following materials:

Materials Properties Use

Aluminium Low density metal which is sturdy. Reflects the Sun’s heat and insulates the spacecraft. Used as window shutters.

Titanium Light-weight yet strong.

Protection for spacecraft.

Kevlar “Bullet-proof vest.” Impact resistant.

Protects spacecraft from even dust sized particles it may encounter as it zips through space.

Glass Between 8 and 38 times thicker than a standard window on Earth.

Spacecraft windows - glass is subject to strict quality control because even a micro-meteoroid could cause a fracture.

The aim of using these materials is to make the spacecraft as light weight as possible. The lighter the spacecraft,

the less fuel required to get it into space. As the vehicle reaches the edge of space, it will weigh three times its

original weight and the modules must be able to handle this.

Air pressure inside the spacecraft causes a considerable force on the interior (it is the same on Earth, but the

external pressure balances it out) so the modules tend to be made of aluminium which has a lower density than

a lot of metals but it sturdy.

https://science.nasa.gov/science-news/science-at-nasa/2001/ast14mar_1

1.2 Fuels

Liquid hydrogen is the choice fuel for spacecraft because it is extremely light (has the lowest molecular weight

of any known substance) but is extremely powerful when it burns.

When combined with liquid oxygen (an oxidiser), liquid hydrogen yields the greatest efficiency when compared

with the amount of propellent consumed compared with any other rocket propellent.

However, liquid hydrogen and oxygen are both cryogenic which means they can only be liquified at very low

temperatures (-253 °C for liquid hydrogen). This also means that it must be carefully insulated (or a cooling

system fitted) to keep it from evaporating and encountering the rocket engine exhaust which would become

extremely hot. Once the spacecraft has left Earth’s atmosphere it is hit with the Sun’s radiation – another factor

resulting in the “perfect” insulation of liquid hydrogen. If it is heated up, it will expand rapidly so the spacecraft

must have areas of ventilation. Liquid hydrogen is also capable of leaking through welded seams and can make

the metal surrounding it brittle.

https://www.nasa.gov/topics/technology/hydrogen/hydrogen_fuel_of_choice.html

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1.3 Escape velocity

The escape velocity is the minimum speed needed for an object to escape from the gravitational influence of a

massive body – i.e. the Earth.

The escape velocity of a massive body is found using the equation:

𝑣𝑒𝑠𝑐 = √2𝐺𝑀

𝑅

Where vesc is the escape velocity, G is the universal gravitational constant (6.7 x 10-11 m3/kgs2), M is the mass of

the body, and R is the radius of the body.

The escape velocity increases with mass. A more massive body (the Sun) will have a greater escape velocity than

the Earth.

Task: given that the mass of Earth is 6 x 1024 kg, and the radius of Earth is 6.4 x 106 m, calculate the escape

velocity required for a spacecraft to leave the Earth’s atmosphere.

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1.4 Hazards

The most dangerous part of any space journey is taking off. As mentioned in the “fuels” section, liquid hydrogen

is extremely sensitive to any temperature change and will explode if exposed to a sudden burst of heat. Also, the

immense amount of power which is being generated must be controlled. Any minute fault with the electronics,

or even a trapped air bubble could result in a deadly explosion.

The pointy end of the spacecraft must also be perfectly vertical. If it veers, it will just break apart during the

journey.

As the spacecraft journeys through the Earth’s atmosphere, it must reach the escape velocity to leave it. If this

velocity is not reached, Earth’s gravitational force will pull it back down towards the surface. In addition, the

rocket carrying the spacecraft will be battered with extremely loud sound waves which can lead to pieces of the

rocket shattering – especially if the liquid hydrogen fuel has caused the surrounding metal to become brittle.

The further you travel from the Earth’s surface; the more dangerous the Sun’s radiation becomes. Astronauts on

the International Space Station are exposed to 80 times the radiation we are exposed to on Earth.

Meteor showers can also damage spacecraft. The ISS is zipping through space meaning that the tiniest dust

particles pose a threat. If the spacecraft was to slow down, it would no longer be travelling fast enough to remain

in orbit so would come crashing back down to Earth so this high speed is necessary.

1.5 Cost

The average cost to launch a Space Shuttle is about $450 million per mission.

https://www.nasa.gov/centers/kennedy/about/information/shuttle_faq.html#1

The International Space Station orbits 250 miles above Earth and costs the US about $3 billion per year to

maintain. From an article written in 2014 (https://www.washingtonpost.com/news/wonk/wp/2014/01/09/nasa-

plans-to-keep-the-international-space-station-going-until-2024-is-that-a-good-

idea/?utm_term=.a452c1857106), the writer states that the ISS had already cost $160 billion in the construction,

launch and maintenance – as of April 2015, this was said to be the most expensive object ever built. Multiple

countries have contributed to this large-scale project – US, Europe, Russia, Japan, and Canada.

The cost to launch a rocket is huge. Virgin Galactic offer a ticket to space at $250,000 a person which essentially

gives you 3 days of training to cope in such conditions, views at the very reach of Earth’s atmosphere and several

minutes of free fall. This is very much for a personal experience, never mind a large-scale research project.

1.6 Communication

NASA and the Russian space agency have nearly 100% communication contact with astronauts and cosmonauts

on the ISS. This is visual (video) and verbal contact. This is done via antennae.

This surreal communication system works via seven artificial satellites orbiting the Earth in geosynchronous orbits

(fixed location orbits above the Earth’s surface) which are spaced out such that at least one satellite is available

at any one time. Again, these satellites required careful precision when plotting their routes into space, and one

even ended up exploding!

https://www.universetoday.com/101196/how-do-astronauts-on-the-space-station-stay-in-touch-with-earth/

All space missions (manned and un-manned) communicate in this way, providing a satellite is within the line of

sight.

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2 Well worded report on the products discovered or developed because of space flight.

Material Why was it developed by NASA?

Use in everyday life

Slow spring back foam.

The foam could absorb energy of crashes and increase passengers’ chances of survival. It can also be used to make journeys comfier as it allows for a more even distribution of body weight and bounces back one the person has got up.

Memory foam is used in helmets, mattress pads, wheelchairs seats for those with painful injuries – the foam will support the body part. https://science.howstuffworks.com/innovation/inventions/top-5-nasa-inventions1.htm

Arteriovision. To monitor cardiovascular health of astronauts as they train for flight missions.

Helps doctors diagnose and monitor treatments for hardening of the arteries in its early stages, before it causes heart attacks and strokes. It is non-invasive. https://www.nasa.gov/vision/earth/technologies/artery-20070606.html

Digital hearing aids – cochlear

implants.

A hearing-impaired NASA engineer developed a digital hearing aid as analogue hearing aids just amplified the sound entering the ear.

Restored the hearing of thousands and allowed people born deaf to perceive sound for the first time. The cochlear implant is surgically implanted and provides hearing sensations to those with severe-to-profound hearing loss who receive little or no benefit from hearing aids. https://spinoff.nasa.gov/spinoff2003/hm_3.html

Abrasion-resistant lens

coatings.

Glass lenses were very damaging if they shattered, and plastic lenses were easy to scratch so a NASA scientist developed a thin plastic film which was surprisingly tough and abrasion-resistant.

Sunglasses manufacturer – Foster-Grant commercialised this scratch-resistant coating and today, most eyeglasses sold in the US are outfitted with plastic lenses that last 10 times as long as the old ones. https://science.howstuffworks.com/innovation/inventions/top-5-nasa-inventions5.htm

Lifeshears. Type of cutting equipment with reduced cost, weight and noise used in rescue operations. Uses the same power source as used to separate solid rocket boosters from the shuttle.

Lifeshears have helped search-and-rescue teams save individuals trapped in wrecked cars or collapsed buildings. The invention loosened victims from dangerous debris immediately following the 9/11 attacks on the World Trade Centers in 2001. https://science.howstuffworks.com/innovation/inventions/top-5-nasa-inventions8.htm

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3. Physical aspects of achieving and sustaining space flight

The amount of energy required to launch a spacecraft into orbit depends on the location of the launch site and

the inclination of the orbit. Spacecraft in low Earth orbits require the least amount of energy to reach their

destinations. The ISS orbits at an inclination of 51.6397 degrees to make it easier for the Space Shuttles to reach

it.

To achieve successful space flight, a space craft must be travelling fast enough to escape the Earth’s atmosphere.

As calculated before, the Earth’s escape velocity is

𝑣𝑒𝑠𝑐 = √2𝐺𝑀

𝑅= √

2(6.7 × 10−11)(6 × 1024)

(6.4 × 106)= 11.2 𝑘𝑚/𝑠

This speed is approximately 33 times the speed of sound. If a spacecraft has not reached this velocity then the

spacecraft will be pulled back to Earth by Earth’s gravitational force.

Once the spacecraft has reached its orbit, it takes work to keep it there. This is because the Earth is not perfectly

spherical so the force due to gravity is stronger in some places compared with others. This disturbance along with

the pull from the Sun, Moon and Jupiter means the inclination of satellite orbits must be changed a few times to

keep them in place.

The ISS is in a low Earth orbit which means it is affected by drag from Earth’s atmosphere. Despite there being

very little air resistance, it is still strong enough to pull the spacecraft closer to Earth. The drag force experienced

on the ISS increases when the Sun is active. The Sun adds extra energy to the atmosphere causing it to expand.

The thinnest layer of the atmosphere rises and the thicker layer beneath it takes its place. So, the ISS will

experience the most resistance and can drop up to 100 m per day meaning its orbit might have to be boosted.

The ISS travels at approximately 7.7 km/s which is the speed required for it to stay in this orbit. Because the ISS

is travelling at this speed, it orbits the Earth every 92.7 minutes meaning it orbits Earth 15.5 times a day.

https://www.quora.com/How-does-the-International-Space-Station-maintain-its-orbit-and-what-propellant-

does-it-use

4. Dangers of space flight

You need to include a brief description of general dangers: http://www.bbc.co.uk/guides/zctgq6f

And then briefly discuss these real-life accidents:

Accident Weblink

Salyut 1 https://www.nasa.gov/audience/forstudents/k-4/stories/nasa-knows/what-is-the-iss-k4.html

Apollo 1 https://www.nasa.gov/mission_pages/apollo/missions/apollo1.html

Challenger Space Shuttle https://www.nasa.gov/multimedia/imagegallery/image_gallery_2437.html

Columbia Space Shuttle https://www.space.com/19436-columbia-disaster.html

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5. History of spaceflight

Here is a timeline of different space missions – both manned and unmanned.

Spaceflight Year Proposed by which country or organisation

Details Manned or unmanned

Sputnik 1 1957 The Soviet Union.

First man-made object to leave Earth’s atmosphere. https://history.nasa.gov/sputnik/

Unmanned.

Apollo 11 1969 NASA. First manned lunar (moon) landing mission with a crew of 3 astronauts. https://www.nasa.gov/mission_pages /Apollo/missions/apollo11.html

Manned.

Hubble Space Telescope

1990 NASA Telescope that gathers light from cosmic objects so scientists can better understand the universe around us. https://www.nasa.gov/mission_pages /hubble/story/index.html

Unmanned.

Cassini-Huygens

1997 NASA, European Space Agency (ESA), Italian Space Agency (ASI).

Robotic spacecraft which travelled to Saturn by the sling shot effect using the gravitational forces of each planet it passes. YOU NEED TO RESEARCH THIS MORE. https://www.space.com/17754-cassini-huygens.html

Unmanned.

International space station

1998 NASA Provides an international laboratory for experiments within a space environment. https://www.nasa.gov/audience/forstudents/k-4/stories/nasa-knows/what-is-the-iss-k4.html

Unmanned until year 2000 when humans were sent to live in the ISS.

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6. Planned missions

MUST be presented as a journalistic appraisal with an evaluation of each mission – distinction criteria.

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7. How does the information in section 6 relate to:

• Improving our knowledge and our current understanding of the universe – its origin, dynamic nature,

and theoretical future?

• If our Earth is unique?

• Problems associated with space travel beyond the confines of the inner solar system?

Make some notes here:

Improving our knowledge and our current understanding of the universe – its origin, dynamic nature, and

theoretical future.

(Hint: the JWST in conjunction with the HST)

Is our Earth unique?

(Hint: the deep space gateway mission)

Problems associated with space travel beyond the confines of the inner solar system.

(Hint: the new horizons mission)

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8. Effects of spaceflight on the human body

8.1 Time-invariant effects

1) Gravity fields – a change in a field of gravity affects your spatial orientation, head-eye and hand-eye

coordination, balance, locomotion, and will almost guarantee motion sickness which could make landing

a spacecraft more dangerous than first thought. Without the strength of Earth’s gravity working on your

bones, they can lose minerals at a rate of 1% per month – this is not necessarily corrected when you

return to Earth. If this happens, you have a greater risk of developing osteoporosis-related fractures later

in life. Another factor is losing muscle mass. If you do not eat properly and do not exercise then your

muscle mass will deplete rapidly – this can cause permanent and potentially fatal damage to the heart.

Eye problems are also a common problem due to fluid in your body shifting to your head causing an

increase in pressure on your eyes and eventually vision problems.

2) Isolation/ confinement – astronauts are in the space station for months at a time, and during this time,

they develop behavioural issues meaning that must be selected carefully. Depression is a common

symptom.

3) Hostile/ closed environments – microorganisms that naturally live on skin are transferred from one to

another in closed habitats. Your immune system is altered making you more susceptible to allergies,

illnesses, and disease.

4) Space radiation - the cosmic radiation (shielded by Earth’s magnetic field) can result in an increased risk

of developing cancer in your lifetime if it penetrates the body. It can also damage the central nervous

system which can alter your cognitive function, reduce motor function, and behavioural changes. This is

a possible danger which is not directly related to the amount of time spent in space.

5) Distance from Earth – if anything happens to the space station, the signal will take 20 minutes to reach

Earth which means you (and the team) must deal with it. Any equipment failures also have to be dealt

with.

6) Constant free fall – it requires little muscle involvement to bounce around in space so muscle atrophy is

significant but the astronauts do not necessarily notice it until the return to Earth. Coordination is also

hugely affected. This also causes bones to weaken and the calcium in them is secreted through urine.

7) Physiological effects – significant adverse effects to space flight include muscle atrophy and skeletal

deterioration. Blood flow changes and results in an abundance of blood around the neck and chest area

and a lack of blood in the legs. Astronauts suffer with puffy faces and the brain reads this as the body

having too much blood so the body ends up losing about 20% of its blood plasma leaving the astronauts

temporarily anaemic.

https://www.nasa.gov/hrp/bodyinspace

8.2 Case study about astronaut training during the Apollo mission

https://www.hq.nasa.gov/office/pao/History/SP-350/ch-7-8.html

You need to read this article and write a case study about the issues NASA faced during the Apollo mission

to the Moon.

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8.3 Effects of long-term spaceflight on the human body

We have already considered the effects of space flight in general in section 1.7. We now need to assess the

implications of long-term space flight and what can be done to limit the problems – osteoporosis, change in

blood flow, or drop in blood plasma levels.

Condition Implications What can be done to limit this?

Osteoporosis Bones are no longer subject to the same stresses they are subjected to on Earth. Overtime, calcium in the bones is broken down and released into the bloodstream – this reflects the decrease in bone density. This loss leaves bones weak and less able to support the body’s weight and movement upon returning to Earth which puts the astronaut at a higher risk of fracture. This begins within the first few days in space. The most severe loss is between the second and fifth month. https://www.nasa.gov/mission_pages/station/research/ benefits/bone_loss.html

They can reduce the risk by having a proper intake of appropriate nutrients – calcium and vitamin D, and an effective exercise program. Effective medications can also be taken to reduce the risk of fractures. Exercise is the final key element and the ISS astronauts exercise for on average 2 hours a day.

Change in blood flow

The lack of gravity on the ISS means blood flows to the chest and head which causes astronauts to have puffy faces and bulging blood vessels in their necks. The lack of blood flowing to and from the brain can cause astronauts to feel dizzy and sometimes faint when they return to Earth’s gravity. https://www.nasa.gov/mission_pages/station/research/ cciss_feature.html

Astronauts can wear compression garments and stay hydrated. Exercising can help to promote a more healthy blood flow around the whole body.

Drop in blood plasma levels

High blood pressure in the head tells the brain the body has too much blood. This results in a decrease in blood plasma from the body (as much as 20%) meaning the astronauts suffer from temporary anaemia. Having less blood means your heart does not need to pump as hard – it’s going to atrophy. http://www.esa.int/Our_Activities/Human_Spaceflight/ Astronauts/Living_in_space/(print)

Exercise is not enough to reverse the process but can help to minimise it. The more exercise astronauts do in space, the less time it will take them to recover on their return.

The information gathered about the implications of human health during spaceflight

(sections 1.7, 1.8 and 2) will be presented as either a large poster or booklet with

relevant parts of the human body labelled.

You can use skeletal diagrams and muscular diagrams of the human body to illustrate

these implications.

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9. General outlines of work carried out by astronauts

9.1 Medical experiments

The astronauts in the ISS take part in medical experiments to determine how well their bodies are adjusting to

microgravity for long period of time.

Overview

Long-term manned mission in outer space affects the muscle tissue. This experiment aims to characterise this

effect by assessing the (calf) muscle performance of ISS crew members before and after flight. This will test the

amount of power the calf muscles can produce.

Biopsies of the calf muscles are also taken to analyse the health (size, structure, and performance) of individual

cells within that muscle.

Information gathered from this experiment will be compared with pre-existing data from the Life and

Microgravity Spacelab Mission to create a time-based model of how muscles react to space flight.

Applications

It is well established that muscle mass and strength decrease during space flight. This can lead to severe muscle

injuries upon the return to Earth. If manned explorations of Mars are to happen, astronauts may be susceptible

to muscle injury once they step onto the planet. To understand the exact cellular and biochemical events which

lead to this loss of muscle mass and strength can begin to be answered from the initial biopsies of calf muscle

cells.

This could help to understand the muscle atrophy in the elderly population on Earth due to the decrease in

muscle elasticity.

THIS IS JUST ONE EXAMPLE OF HOW THE ISS CREW MEMBERS ARE BENEFITTING THE MEDICAL INDUSTRY.

Figure 1: ISS crew members exercising to reduce the amount of lost muscle mass during long-term space flight.

They exercise on average 2 hours a day.

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9.2 Research based experiments linked to areas of science and industry

Task: your job is to research other experiments going on onboard the ISS and summarise them in the table

below – the specification states this must be done independently.

https://www.nasa.gov/mission_pages/station/research/news/15_ways_iss_benefits_earth

Experiment Summary Links to science and industry

Analysing muscle tissue before and after space flight to better understand muscle atrophy in elderly people on Earth.

Supporting water purification efforts worldwide.

Growing high-quality protein crystals.

Improving eye surgery with space hardware.

Making inoperable tumours operable with a robotic arm.

Preventing bone loss through diet and exercise.

Understanding the mechanisms of osteoporosis.

Developing improved vaccines.

CORRECT REFERENCING IS ESSENTIAL HERE – YOU NEED TO ADD TO YOUR BIBLIOGRAPHY.

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10. Hertz Sprung Russel diagram

YOU MUST DRAW THE HERTZ SPRUNG RUSSEL DIAGRAM BELOW and outline size, luminosity, and

temperature. I would sketch this one:

https://d2gne97vdumgn3.cloudfront.net/api/file/cVbnATGVTvOK5tmOkrmM

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10.1 Life cycle of a star

You will need to draw another life cycle of a star depending on mass – BE CAREFUL NOT TO SELF-PLAGIARISE

HERE! http://www.schoolsobservatory.org.uk/learn/astro/stars/cycle

You will need detailed notes including the point where the star reaches hydrostatic equilibrium – pressure

balance, to the point where the pressure overcomes the gravitational force and the star swells and, in the

case of a supernova, it explodes. This must be accompanied by a labelled diagram.

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11. Evidence for the Big Bang

We covered this content in learning aim A. Instead of using my notes and risking self-plagiarising from the first

assignment, use this website:

http://www.bbc.co.uk/schools/gcsebitesize/science/aqa_pre_2011/radiation/originsrev2.shtml

For this section, you need to explain how redshift and the cosmic microwave background radiation provide

evidence for the Big Bang and therefore, evolution of the universe.

11.1 Redshift

11.2 CMBR

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12. Evolution of the Universe

The current cosmological theory for the beginning of the universe is the Big Bang theory. The first stage of this

theory is (as discusses in learning aim A) that the Universe must have formed from a single point smaller than a

proton (which redshift gives evidence for) – the initial singularity which is thought to be an infinitely dense one-

dimensional point which contains all the mass and energy of the universe. Temporary changes in energy at that

point (known as quantum fluctuations) caused the point to rapidly expand in the Big Bang. During this

expansion, the edges of the universe travel faster than the speed of light so inflation is rapid (it was analogous

to an ant expanding to the size of the Milky Way almost instantaneously).

This extremely hot universe is cooling down as it expands but is still far too hot for atoms to form. Initially,

elementary particles known as quarks and gluons were formed which are the building blocks of matter. Once

the temperature begins to drop to a couple of trillion Kelvin, quarks and gluons start to form protons and

neutrons, and eventually atoms – with hydrogen nuclei to be formed first. The Universe at this stage is a giant

nuclear reactor as this hydrogen nuclei is fused into a helium nucleus and then a lithium nucleus. All these are

ionized as the Universe is too hot for them to capture electrons. These free electrons collide with the photons

(light) in the universe and scatter it which makes the universe appear opaque. 400,000 years after the Big Bang,

the universe is now cool enough for nuclei to capture electrons which now prevents the free electrons from

colliding with photons (light) and the universe is now transparent. The light which was once scattered by

electrons can still be detected today – the cosmic microwave background radiation. The CMBR is so important

because it is present from every direction and is uniform (evenly distributed). The CMBR is the oldest light we

can observe as it is more than 14 billion years old meaning it began its journey over 14 billion years ago. (The

present-day temperature of the CMBR has been measured to be 2.73 degrees above absolute zero (0 Kelvin) by

radio telescopes).

400 thousand – 450 million years later, the first stars and galaxies begin to form but you cannot see them as the

hydrogen in the universe is absorbing the light. Over the next 450 million years, galaxies, supernovae, pulsars,

black holes begin to form. Stars are now hot enough to form carbon, oxygen, nitrogen, and iron. For stars

ranging from 10 to 100 times the mass of the Sun, they can end their lives in violent explosions known as

supernovas. Their expelled material creates new objects and could even go on to make celestial bodies – the

Earth for example.

https://www.youtube.com/watch?v=5wYw7p5MMNg

The Solar System nebula hypothesis gives light onto how the Earth may have been formed. About 4.6 billion

years ago, a nebula containing mainly hydrogen and helium (with remnants of heavier elements which would

have been produced in a supernova) collapsed under its own gravity and began to rotate. This rotation

accelerated and eventually flattened out into disc, with the largest concentration of matter at the centre – this

formed the Sun. The gravitational field of the Sun caused smaller clumps of matter to form in the disc which

became planets. The proto-sun and proto-planets grew by acceleration of matter that was falling in toward the

centre of mass (centre of the Sun/planet). The temperature of the proto-sun’s core grew until it could

eventually fuse hydrogen together to form helium – and thus the Sun was born. This nuclear reaction released

copious amounts of energy – the solar wind, which swept most of the remaining gas and dust particles (smaller

than about 10 m) from the inner solar system, leaving planets and asteroids. The outer solar system planets wer

formed from iron and rocky silicates which were stable and too heavy to be swept out of the disc – these

formed the cores of the Jovian planets (Jupiter, Saturn, Uranus, Neptune). Also, the outer solar system nebula

temperatures were cool enough for the abundant gases to accumulate forming proto-planets which composed

of mostly hydrogen, helium, hydrogen compounds (methane), and ammonia. These planets could have only

been formed from the destruction of stars large enough to fuse and produce these heavy elements –

supernovas. http://www.columbia.edu/~vjd1/solar_nebula.htm

Name: __________________________________ Class: ________________ Teacher: ____________________

20 | P a g e

The movement of galaxies give evidence for an expanding universe and the incoming light from the galaxies

accelerating away from us appears red because the emission spectrum has been redshifted. The majority of

galaxies are accelerating away from us but some are accelerating towards us and they appear blue because

their emission spectra have been blue shifted.

The fact that galaxies are moving away from us can be shown by plotting on a graph of recessional velocity to

distance. It shows that the further away a galaxy is, the faster it is moving away from us. This is Hubble’s law.

The gradient of this graph gives the Hubble’s constant which can then be used to calculate the age of the

universe:

Figure 2: Graph used to determine the current estimate for the age of the Universe.

𝐴𝑔𝑒 𝑜𝑓 𝑢𝑛𝑖𝑣𝑒𝑟𝑠𝑒 = 1

𝐻𝑢𝑏𝑏𝑙𝑒′𝑠 𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡 =

1

2.2 × 10−18= 4.6 × 1017𝑠 = 14.6 𝑏𝑖𝑙𝑙𝑖𝑜𝑛 𝑦𝑒𝑎𝑟𝑠

Parallax allows us to measure distances to “nearby” objects. We know the distance to any object outside our

solar system will be huge so how can we measure them?

We measure astronomical distances in astronomical distances (Solar system length distances), light years for

“nearby” objects, and parsecs for huge distances:

• Astronomical units – 1 AU is the distance between the Sun and the Earth.

• Light years – DISTANCE light travels in a year (note: this is not a time!)

• Parsecs – distance at which 1 AU subtends an angle of one arc second (draw a diagram to illustrate a

parsec).

This means we cannot see light that is more than 13.7 billion light years away because it has not reached us yet!

The distances measured in figure 2 are measured in Mega Parsecs – million parsecs which are colossal distances

away.