Light, EM Spectrum, and the Big Bang Theory
Light, EM Spectrum, and the Big Bang Theory
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.
How do we look at the universe?
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Space-Time • We see everything as it once was.
Young Old
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60s
50s
Baby Boomer Universe
40sFarther away we look, further back in time we see!
90s
80s70s
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What We See
What do we see when we look?
We see light!
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…
***The shorter the wavelength, the more energy the photon has
**Remember, no matter whatthe wavelength, all light travels the same speed
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.
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.
Radio(Low Frequency & Very High
Frequency)• Emitted by
– Astronomical Objects
– Radio Station transmitters
• Detected by– Ground based
radio telescopes
– Radios
Microwave• Emitted by:
– Gas clouds collapsing into stars
– Microwave Ovens– Radar Stations– Cell Phones
• Detected by– Microwave
Telescopes– Food (heated)– Cell phones– Radar systems)
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
An animal, or a human body, for example, emitssome infrared radiation that can be detectedby an infrared camera
Color is related to temperature
Visible
• Emitted by– The sun and other
astronomical objects– Laser pointers– Light bulbs
• Detected by– Human eyes– Cameras – Plants– Telescopes
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.
The colours of the rainbow:
• Red
• Orange
• Yellow
• Green
• Blue
• Indigo
• Violet
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
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
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
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
• 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
Using filters• Filters can be used to “block” out different colours of light:
Red Filte
r
Magenta
Filter
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)
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
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
Gamma Ray• Emitted by
– Radioactive materials– Exploding nuclear
weapons– Gamma-ray bursts– Solar flares
• Detected by– Gamma detectors and
astronomical satellites– Medical imaging detectors
Sources of g-ray Emission• Black holes• Active Galaxies• Pulsars• Diffuse emission• Supernovae• Gamma-ray bursts• Unidentified
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
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
The sun gives off the full range of wavelengths of light (called the Electromagnetic Spectrum)
And the universe for that matter!
What have we noticed?
Our Universe is Cooling!
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
Longwave-
-length
Lowtemperature
In 1964, the radiation predicted by Gamov was detected with this antenna by Penzias and Wilson
antenna
PenziasWilson
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 !
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
In 2003, the WMAP satelite took a picture of the universe with small fluctuations of temperature
WMAP measured the same data everywhere.So, the big-bang must have taken place at the same time everywhere
Our Universe is Expanding!
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.
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.
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
f Don Lincoln, Fermilab f
So what does heat have to do with anything?
f Don Lincoln, Fermilab f
Heat is Energy and according to Einstein…
f Don Lincoln, Fermilab f
E = m c2
Energy is MatterMatter is Energy
Lots of energy makes lots of matter
and vice versa!!!!!!
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.
f Don Lincoln, Fermilab f
So what do we think happened
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
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
Three minutes laterThree minutes later
Atoms are formedAtoms are formed
1 billion years later1 billion years later
First stars are First stars are formedformed
5 billion years later5 billion years later
Galaxies are Galaxies are formedformed
9 billion years later9 billion years later
Earth is formedEarth is formed