Big Bang Theory

OUTLINE

• First 25 minutes of the video

• Notes on waves, Doppler effect, and red/blue shift

• Mini lab on spectrums and how they are used to

understand red and blue shift

• Mini lab on the expanding universe

• Video

• Understanding the Big Bang and Atom formation

scienceaid.co.uk

Electromagnetic Waves

• https://www.youtube.com/watch?v=oZZ4wKYtVl8 (short)• https://www.youtube.com/watch?v=nt-A1Cr6Aao (1:18, explained)• Transverse wave made up of electrical and magnetic energy• It is produced when the electric and magnetic fields switch back

and forth (vibrating) causing a disturbance that travels through space as a wave.

• This wave carries energy and information from one part of the universe to another, which is called electromagnetic radiation.

• Our instruments pick up these electromagnetic waves and change them into vibrating tunes/static

• They travel at the speed of light: 299,792.458 km/s in a vacuum

Electromagnetic Spectrum• “All electromagnetic waves travel at the same speed in a

vacuum, but they have different wavelengths and different frequencies” (Pasachoff 75).

• An electromagnetic spectrum “…is the complete range of electromagnetic waves placed in order of increasing frequency” (Pasachoff 75).

• Radio waves, Infrared rays, Visible light, ultraviolet rays, X-rays, and gamma rays.

Electromagnetic Spectrum

• Radio Waves

– Longest wavelength and lowest frequencies

– Broadcast waves and microwaves

• Infrared Rays

– Wavelengths shorter than radio waves

– The invisible heat you feel

Visible Light

• You can see these waves

• The longest wavelengths and lower frequencies (and lowest energies) appear in the red and the shortest wavelengths and higher frequencies (and higher energies)appear in the violet/blue.

• Violet Blue Green Yellow Orange Red

• Ultraviolet rays– Shorter wavelengths and higher frequencies

than visible light– They carry more energy than visible light– Pros: killing bacteria and providing vitamin D– Cons: to much exposure causes skin cancer, can

damage your eyes, and burn your skin

• X-Rays:– Shorter wavelengths and higher frequencies

than ultraviolet rays, thus can carry more energy

– Can go through most matter, except dense matter like bones

• Gamma Rays:– Have the shortest wavelength and highest

frequencies, thus has the greatest amount of energy

– Great penetrating ability– Pros: use to kill cancer cells inside the body, use

to help see inside the body– Cons: produced by nuclear reactions and can be

harmful (even deadly if exposed to too much).

“Sound Waves and Stars: The Doppler Effect”

blueblue

redred

Spectral Line Analysis

Activity

Spectrographs• http://www.learner.org/teacherslab/science/light

/color/spectra/• Spectrum Tubes• Instrument to separate white light into the bands

of color

• This is a spectrum from our sun. The dark lines are where different elements have absorbed different frequencies of light. Each element has its own spectrum, kind of like a finger print. Scientists use spectrographs to determine what elements other stars are made of.

Spectrums A, B and C are from identical stars within our galaxy. Spectrum A represents a possible spectrum of a star not moving toward or away from Earth. Spectrums B and C show stars in motion with respect to an observer on Earth. Compare the three spectrums and answer the following questions:

Spectrographs

• Weber Online Spectrograph Practice

HUBBLE’S DISCOVERY

• “Just as the light from a single star can be used to make a stellar spectrum, scientists can also use the light given off by an entire galaxy to create the spectrum for that galaxy” (Holt 793).

• In the 1920s, Hubble found that the spectra of galaxies, except a few near our own, were all shifted towards the red end of the spectrum.

• By measuring the redshift he was able to determine the speed at which the galaxies were moving away from us.

• Galaxies farthest away show the greatest redshift and therefore the greatest speed.

• This evidence pointed to the fact that our universe was expanding.

• Most galaxies are red-shifted (moving away from us) today. Let’s rewind the clock of time. Using the information and data from what you have learned, what can be inferred about the origin of the universe?

Balloon Lab

• Question:

– How is the universe expanding?

• Vocabulary words

– Independent variable: a factor that is changed on purpose; also called manipulated variable

– Dependent variable: a factor that is observed or measured in response to a change in the independent variable; also called responding variable

BIG BANG SUMMARY NOTES

BIG BANG THEORY• The Big Bang Theory claims that the

universe has expanded from a very dense,

very hot state that existed at some time in

the past.

Evidence to support• Studies of red-shifts of distant galaxies show that

the universe is expanding.

• Cosmic Background radiation (left over

energy/heat)

• Abundance of Hydrogen and Helium

Big Bang Model• Running the expansion backward allows us to calculate

the temperature and density of the universe during its

earliest moments.

• The known laws of physics can be used to determine

the behavior of matter and energy at these temperatures

and densities.

• The model is then used to make predictions that can be

compared to observations.– The only elements in the early universe were hydrogen and helium (and a

tiny amount of lithium). The hydrogen-helium mass ratio was about 75-

25%.

– Microwaves with an energy corresponding to a temperature of about 3 K

will be found everywhere in space. From Earth they will be “seen” across

the entire sky.

TEMPERATURE

Time Temperature

One million of a second 1013 K (ten trillion Kelvin) ≡ a lot of energy

Or 179,999,999,999,540.31° F

10-thousand of a second 1012 K (one trillion Kelvin)

Or 17,999,999,999,540.33° F

10th of a second Cooling

A second Cooling

100 seconds 109 K or 1, 799,999,540.33 ° F

10 minutes cooling

380,000 years 3,000 K or 4,940.33 ° F

Now 3 degree above absolute zero or 3 K

or -454.27° F

Summary:

• It was extremely hot and then started to cool slowly until it is

now extremely cold.

• Temperature played a crucial role in the formation of matter.

BIG BANG TIME LINE Formation of matter

Where did matter in the

universe come from?

E = mc2Mass is just “condensed”

energy

Energy →mass

A particle – antiparticle pair can be

created if the available energy equals

the mass of both particles times the

speed of light squared

A very BIG number!

Albert

Einstein

START

Too hot for any matter to form, only pure energy

ABOUT A MILLIONTH OF A SECOND…

• 1013 K (ten trillion Kelvin) or

179,999,999,999,540.31 ° F

• Protons, anti-protons, neutrons and anti-neutrons

begin to form because of cooler temperatures

• As a proton or neutron collides with its anti-particle

they annihilate and are converted to energy in the

form of photons– Photons are light particles

protonanti-proton

anti-neutron

neutron

About one ten-thousandth of a second . . .

• Almost all particles and anti-

particles annihilate and produce

gamma ray photons.

• It is no longer hot enough to produce protons and anti-

protons (or neutrons and anti-neutrons) spontaneously from

pure energy to replace those that annihilate each other.

proton anti-proton

• Photons are constantly scattered by free particles with an

electric charge like electrons or protons

• These photons increase in wavelength as the universe

expands and will eventually become the majority of photons

that make up the cosmic background radiation

ONE TEN-THOUSANDTH OF A SECOND . . . CONTINUED

• maintains equal numbers of protons and neutrons . . .

p+ + e− ↔ n + e n + e+ ↔ p+ +e

• High energy collisions between protons, neutrons

and other particles like electrons can transform one

particle into another.

• a billion photons for every proton or neutron

About a tenth of a second . . .

• As the temperature (and available energy) drops,

transformation to protons is favored over neutrons

About one second…

• Transformation reactions can no longer occur.

Neutrons begin to decay into protons

n → p+ + e− + e

ABOUT 100 SECONDS …• Neutron decay results in a 1:7 ratio of neutrons to

protons.

• Universe is now cool enough for protons and

neutrons to bind together. This is called fusion.

This process creates new, heavier atomic nuclei and

is called nucleosynthesis.

proton

(hydrogen

nucleus)

neutron

deuterium

tritium helium

AT THE BEGINNING OF NUCLEOSYNTHESIS . . .

14 protons 2 neutrons

12 hydrogen nuclei

Atomic mass = 12

At the end of nucleosynthesis . . .

1 helium nucleus

Atomic mass = 4

Mass ratio 75% 25%

• Very little happened in nucleosynthesis for a

long time as temperature and density are too

low for fusion.

About 10 minutes . . .the end of big bang nucleosynthesis

• Temperature drops to 3000 K

• Universe is cool enough for electrons to bind with nuclei and

form stable atoms

• With most electrons now bound in atoms, photons can travel

large distances without being scattered by free electrons.

• Photons now travel in all directions, resulting in what is

called the cosmic background radiation.

ABOUT 380,000 YEARS …

HHe

NOW …

• With continued expansion, temperature drops to

about 3 K (Three degrees above absolute zero)

• Photons that make up the cosmic background

radiation are now microwaves

– most of these photons were produced by the particle anti-

particle annihilation at about one ten-thousandth of a

second