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Light, EM Spectrum, and the Big Bang Theory
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Page 1: Light em&bigbang

Light, EM Spectrum, and the Big Bang Theory

Page 2: Light em&bigbang

Electromagnetism

• It is necessary to understand that electrical charge (positive/negative) and magnetism (north/south) are different aspects of the same force -- electomagnetism.

• Oppositely charged objects, such as a proton and an electron, attract one another, while particles with the same charge repel each other.

Page 3: Light em&bigbang

How do we look at the universe?

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Ch10Ch10

Space-Time • We see everything as it once was.

Young Old

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Ch10Ch10

60s

50s

Baby Boomer Universe

40sFarther away we look, further back in time we see!

90s

80s70s

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Ch10Ch10

What We See

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What do we see when we look?

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We see light!

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Light energy is carried by particles called Photons, which move at –the speed of light!!

All photons move in waves-

The distance between wave “peaks” is called the Wavelength

Different energies of light have longer or shorter wavelengths…

Page 10: Light em&bigbang

***The shorter the wavelength, the more energy the photon has

**Remember, no matter whatthe wavelength, all light travels the same speed

Page 11: Light em&bigbang

Speed of light

• Light travels at 300,000,000 meters/second

• It takes 8 minutes for a light wave (or a photon) to travel from the sun to the earth.

• We see the moon because it reflects the sun’s light

• It takes 1 second for light reflected off the moon to reach the earth.

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The waves can pass through the object

The waves can be absorbed by the object.

The waves can be reflected off the object.

The waves can be scattered off the object.

The waves can be refracted through the object.

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Radio(Low Frequency & Very High

Frequency)• Emitted by

– Astronomical Objects

– Radio Station transmitters

• Detected by– Ground based

radio telescopes

– Radios

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Microwave• Emitted by:

– Gas clouds collapsing into stars

– Microwave Ovens– Radar Stations– Cell Phones

• Detected by– Microwave

Telescopes– Food (heated)– Cell phones– Radar systems)

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Infrared(Near and Thermal)

• Emitted by– Sun and stars – TV Remote

Controls– Food Warming

Lights (Thermal)– Everything at room

temp or above

• Detected by– Infrared Cameras– TVs, VCRs,– Your skin

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An animal, or a human body, for example, emitssome infrared radiation that can be detectedby an infrared camera

Color is related to temperature

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Visible

• Emitted by– The sun and other

astronomical objects– Laser pointers– Light bulbs

• Detected by– Human eyes– Cameras – Plants– Telescopes

Page 20: Light em&bigbang

Color

• White light is not a single colour; it is made up of a mixture of the seven colours of the rainbow.

We can demonstrate this by splitting white light with a prism:

This is how rainbows are formed: sunlight is “split up” by raindrops.

Page 21: Light em&bigbang

The colours of the rainbow:

• Red

• Orange

• Yellow

• Green

• Blue

• Indigo

• Violet

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Adding colours• White light can be split up to make separate colours.

These colours can be added together again.

• The primary colours of light are red, blue and green:

Adding blue and red makes magenta (purple)

Adding blue and green makes cyan

(light blue)

Adding all three makes white again

Adding red and green makes yellow

Page 23: Light em&bigbang

Seeing colour• The colour an object appears depends on the colours

of light it reflects.

For example, a red book only reflects red light:

White

light

Only red light is

reflected

Page 24: Light em&bigbang

A white hat would reflect all seven colours:

A pair of purple trousers would reflect purple light (and red and blue, as purple is made up of red and

blue):

Purple light

White

light

Page 25: Light em&bigbang

Using coloured light

• If we look at a coloured object in coloured light we see something different. For example, consider a football kit:

White

light

Shorts look blue

Shirt looks red

Page 26: Light em&bigbang

• In different colours of light this kit would look different:

Red

lightShirt looks red

Shorts look black

Blue

light

Shirt looks black

Shorts look blue

Page 27: Light em&bigbang

Using filters• Filters can be used to “block” out different colours of light:

Red Filte

r

Magenta

Filter

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Ultraviolet

• Emitted by– Tanning booths (A)– The sun (A)– Black light bulbs (B)– UV lamps

• Detected by– Space based UV

detectors– UV Cameras– Flying insects (flies)

Page 29: Light em&bigbang

X-ray

• Emitted by– Astronomical objects – X-ray machines– CAT scan machines– Radioactive minerals– Airport luggage scanners

• Detected by– Space based X-ray

detectors– X-ray film– CCD detectors

Page 30: Light em&bigbang

Chandra X-ray Observatory

• Chandra is designed to observe X-rays from high energy regions of the universe, such as the remnants of exploded stars.

• The most sophisticated observatory built to date.

• Deployed by the Space Shuttle Columbia on July 23, 1999,

Chandra X-ray Observatory

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Gamma Ray• Emitted by

– Radioactive materials– Exploding nuclear

weapons– Gamma-ray bursts– Solar flares

• Detected by– Gamma detectors and

astronomical satellites– Medical imaging detectors

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Sources of g-ray Emission• Black holes• Active Galaxies• Pulsars• Diffuse emission• Supernovae• Gamma-ray bursts• Unidentified

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The potential energy in this rock is about to be converted to kinetic energy (energy of movement)

Each type of element, due to its unique size, gives off its own unique wavelengths of light- this allows astronomers to determine what elements they are observing

Page 34: Light em&bigbang

Exploring the EMS withNASA Missions

ASTRO-E2

Chandra

CHIPS Con-X

GALEXGLAST

HETE-2

INTEGRAL

MAP

RXTE

SWAS

XMM-Newton

Swift

Energy (eV)

Radio Infrared Visible UV X-ray Gamma ray

Page 35: Light em&bigbang

The sun gives off the full range of wavelengths of light (called the Electromagnetic Spectrum)

Page 36: Light em&bigbang

And the universe for that matter!

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What have we noticed?

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Our Universe is Cooling!

Page 40: Light em&bigbang

Dicke and Gamov calculated that if the Universe is cooling, we should be able to detect microwave radiation throughout the sky …

I’m Gamov

I’m Dicke

Page 41: Light em&bigbang

Longwave-

-length

Lowtemperature

Page 42: Light em&bigbang

In 1964, the radiation predicted by Gamov was detected with this antenna by Penzias and Wilson

antenna

PenziasWilson

Page 43: Light em&bigbang

In fact, the snow that you can see on an untuned TVis also due in part to that radiation emitted by theUniverse!

We’ve a lot of

work today !

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Original temperature of the radiation : 3000 KToday, it is only 3 KThe cooling says how far the light has travelled13,7 billion years : the age of the Universe

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In 2003, the WMAP satelite took a picture of the universe with small fluctuations of temperature

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WMAP measured the same data everywhere.So, the big-bang must have taken place at the same time everywhere

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Our Universe is Expanding!

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f Don Lincoln, Fermilab f

Doppler Effect• The Doppler effect

says that things moving away from you look redder than they would if they weren’t moving.

• Things moving towards you look more blue.

Page 49: Light em&bigbang

f Don Lincoln, Fermilab f

Edwin Hubble

• Using the Doppler effect, Edwin Hubble discovered that when we look at the universe everything is redder.

• The only explanation for everything moving away from us is that the universe is expanding.

Page 50: Light em&bigbang

f Don Lincoln, Fermilab f

If the universe is cooling and

the universe is expanding,

the simple explanation is that it used to be smaller and hotter

Page 51: Light em&bigbang

f Don Lincoln, Fermilab f

So what does heat have to do with anything?

Page 52: Light em&bigbang

f Don Lincoln, Fermilab f

Heat is Energy and according to Einstein…

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f Don Lincoln, Fermilab f

E = m c2

Energy is MatterMatter is Energy

Lots of energy makes lots of matter

and vice versa!!!!!!

Page 54: Light em&bigbang

f Don Lincoln, Fermilab f

Consider an Ice Cube• Heat it and it

– Melts– Boils– Turns to steam– H2O breaks up into hydrogen and oxygen

atoms– The electrons get ripped off the atoms and

electrons and atomic nuclei scurry around– Atomic nuclei get broken up into protons

and neutrons– Protons and neutrons get ripped apart into

particles called quarks.

Page 55: Light em&bigbang

f Don Lincoln, Fermilab f

So what do we think happened

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When the universe was When the universe was young and hot…young and hot…

infinitely dense point not infinitely dense point not governed by our physical governed by our physical laws or timelaws or time

all matter and energy all matter and energy contained in one pointcontained in one point

Page 57: Light em&bigbang

When the universe was When the universe was young and hot…young and hot…

Everywhere—all Everywhere—all at once—space at once—space was filled with all was filled with all mattermatter

No fireNo fire No soundNo sound Just energy turned Just energy turned

into matterinto matter

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Three minutes laterThree minutes later

Atoms are formedAtoms are formed

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1 billion years later1 billion years later

First stars are First stars are formedformed

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5 billion years later5 billion years later

Galaxies are Galaxies are formedformed

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9 billion years later9 billion years later

Earth is formedEarth is formed