Download cosmology[1] - KarenConnerEnglishIV

Cosmology- the study of
the origin, present, and
future of the universe.
http://www.damtp.cam.ac.uk/user/gr/public/bb_cosmo.html
Einstein and Gravity
Rather than thinking of gravity as an attractive
force between two objects (Isaac Newton)
Einstein’s idea was that gravity is a property of
massive objects that “bends” space and time
around itself. Consider this- why doesn’t the
Moon fly off into space, rather than staying in
orbit around Earth? Newton would say gravity
holds it in orbit. Einstein would say that the
massive Earth “bends” space and time around
itself, so that the moon follows the curves
created by the massive Earth.
His theory was confirmed when he predicted
that even starlight would bend when passing
near the sun during a solar eclipse.
But, even Einstein was wrong sometimes. He also came up
with an idea he called the cosmological constant- it says
the universe is static. It never changes and is the same
everywhere.
Free for commercial use from : http://www.easyvectors.com/browse/other/einstein-vector-material
1920: Harlow Shapley Finds Our Place in the Milky Way
Shapley actually measure our universe. He found it to be
About 100,000 light-years across.
http://members.efn.org/~jack_v/Universe.html
Shapley also helped us find out about nebulae. He catalogued
About 2,500 of them. But, he thought they were
all in our own galaxy! Today we call many of these galaxies!
http://cosmology.carnegiescience.edu/timeline/1920
•Then, beginning in 1929, Edwin
Hubble made three very important
discoveries
•There are other galaxies
besides the Milky Way
•Many of these galaxies are
moving away from us, thus the
universe is expanding
•The farther a galaxy is shifted to
the red end of the spectrum, the
faster it is moving away; thus,
the farthest objects are the
oldest objects.
People began to wonder- where
did they come from?????
While looking through the telescope, Hubble discovered
a Cepheid variable. Over the next several months Hubble
determined that the star varied in brightness with a
period of 31.45 days, which meant it was 7,000 times
brighter than the Sun. Comparing its apparent brightness
with its actual brightness Hubble determined that it was
900,000 light years away!
After The ‘Great Debate’
• After resolving the
‘Curtis-Shapley’
debate. Hubble
measured the distance
to Cepheid variable
stars in the
Andromeda Galaxy:
• 2.5 million light
years!
Hmm...Much further
than I suspected! I
also noticed
something else…..
Moving Galaxies
• Hubble’s observations showed that the light from
distant galaxies was ‘red-shifted’. This was due
Light from
to the ‘Doppler Effect’.
Light
from the
Sun
By Golly, just
look at that!
The dark lines
in the
spectrum on
the right hand
side are ‘red
shifted’.
distant
galaxies
Explaining Doppler Shift
Recession Velocity
• Hubble also noticed that the further away the
galaxy, the greater the red-shift. The greater the
red-shift the greater the speed of recession.
My startling conclusion was
that the further away the
galaxy, the faster is was
moving. Amazing! It also led
me to develop what later
became known as Hubble’s
Law. After Me!
Hubble’s Law
• The red-shift of distant objects is easy to measure therefore
the recession velocity can also be easily calculated.
• We can use the recession velocity to calculate the distance to
a galaxy (or the velocity if the distance is known). This is
known as Hubble’s Law.
Speed of recession (m/s) = Hubble Constant (s-1) x distance
(km)
• The value of the Hubble Constant is 2x10-18 s-1 (this value is
still being researched).
• E.g. A galaxy is 1.5 x 1020 km away. How fast is it moving?
•
Recession Velocity = Hubble Constant x 1.5 x 1020
•
= 2x10-18 x 1.5 x 1020 = 300 km/s
In the early 1900s a
Belgian Priest by the
name of Georges
LeMaitre began
studying Einstein’s
laws of gravitation. He
thought if they were
true then the universe
must be expanding.
http://www.charleroi.be/anglais/ehisto_1.htm
In 1927, two years before Hubble’s
discoveries, LeMaitre graduated from MIT
with his PhD. He also wrote a paper
stating that the universe is the same in
every direction, but it is not static.
He was ignored.
http://www.mhhe.com/physsci/astronomy/arny/student/webtutor/cosmological_red_shift/
LeMaitre used Hubble’s red shift discoveries as evidence
for his own theory. He imagined the universe as a movieonly he played it backwards.
If indeed we played the
movie backwards, then
everything would come
together into one single ,
small point- a primordial
atom which held all matter.
The Big Bang Theory was born!
Georges LeMaitre believed the universe
must have begun in that primordial atom.
Something then caused it to explode into
the ever expanding universe we have
today.
If that explosion did occur, wouldn’t there
be some radiation left today?
People began to pay attention although not
all believed LeMaitre’s theory to be true.
Some information obtained from :
www.pbs.org/wgbh/aso/databank/entries/dp275i.html
In 1948, Hermann Bondi, Thomas Gold,
and Sir Fred Hoyle proposed a different
idea. They got the basis of their idea
from a horror movie!
Hoyle believed that as the universe
expanded, the density of matter stayed
the same because new matter was
continuously being created. So, even
though it was expanding, it was staying
the same.
www.schoolobservatory.org.uk/study/sci/cosmo/internal/steady.htm
http://www.space.com/scienceastronomy/astronomy/hoyle_obit_
010822.html
Sir Fred Hoyle
Mathematically this can work IF the universe
is the same in the past, the present, and the
future.
The Steady State Theory
www.schoolobservatory.org.uk/study/sci/cosmo/internal/steady.htm
http://www.space.com/scienceastronomy/astronomy/hoyle_obit_
010822.html
Sir Fred Hoyle
Although Fred’s theory is probably not
correct, he did help us figure out something
else extremely important- how elements
heavier than helium were created.
He also came up with the name- Big Bang.
He didn’t mean it nicely.
Then Quasars were discovered- 1963!
Quasi-stellar radio source. They look like stars, but they
can’t be stars because they are too bright and too far away.
These were some of the most distant and brightest
objects ever detected.
Maarten Schmidt discovered one that was 1 billion LY away!
The universe just keeps getting bigger.
In the 1930s Grote Reber actually found the first quasar. He
didn’t know it, but he had discovered even more evidence
for the Big Bang and proof the Steady State Theory was not correct.
http://cosmology.carnegiescience.edu/timeline/1966/quasar
Quasars
1.Very small
2.Very bright
3.Very far
4.Very old
Universe can’t be the same
in the past, now, and
future!
A few lucky mistakes lend even more evidence to
the Big Bang Theory
1. In 1932, Carl Jansky, a Bell employee,
accidentally discovered radio astronomy
while looking for interference in radio
telephone lines.
A few lucky mistakes lend even more evidence to
the Big Bang Theory
2. In 1965, two more Bell employees tried to find
the source of interference. This time it was
microwave interference. ( They thought it was
caused by pigeon poop, so they got rid of all
of the pigeon nests.)
They found the source- it was coming from
everywhere in space.
In 1964, Arno Penzias and Robert Wilson had
discovered :
COSMIC MICROWAVE BACKGROUND RADIATION!
This is the radiation leftover from the Big Bang
explosion that scientists had been looking for! They
won a Nobel Prize in 1978 for their discovery.
Poor pigeons!
Another Strike against the
In 1965, the year that the CMB was discovered, a front-page story
in the New York Times quoted Arno Penzias suggesting an activity
that you can do today:
“If you get a very good FM receiver and if you get between stations
you will hear that sh-sh-sh sound. You’ve probably heard this kind
of rushing sound. It’s just sort of soothing. Sometimes it’s not
much different form the sound of the surf. Of the sound that
you’re listening to, about one half of one percent of that noise is
coming from billions of years ago.”
Now What?
http://starchild.gsfc.nasa.gov/docs/StarChild/universe_level2/cosmology.html
Since the discovery of background
radiation we have made
tremendous strides in cosmology.
We have since mapped the
radiation throughout the universe
with the Cosmic Background
Explorer- COBE.
The Big Bang theory is now
accepted as standard cosmology.
The COBE
has mapped
subtle
temperature
differences
in the
radiation
leftover from
the Big
Bang. These
can be
attributed to
our sun, our
galaxy, and
some other
influences.
Blue- absolute zero (0K)
Red- 4 degrees Kelvin (4K)
Background radiation- 2.725
degrees Kelvin ( 2.725K)
http://map.gsfc.nasa.gov/m_uni/uni_101Flucts.html
http://www.umich.edu/~gs265/bigbang.htm
There’s still much to learn!
In 1978, Vera Rubin and a colleague set out to measure the
mass of a galaxy. Little did they Know they were about to make
the next BIG discovery.
They fund the masses of some galaxies to be way
too big- sometimes 10x too big. There had to be something else
there- dark matter!
http://www.nasa.gov/mission_pages/hubble/news/dark_matter_ring_feature.html
There’s still much to learn!
In 1989, we began mapping the universe.
Margaret Geller and John Huchra began the quest to map the
Universe. Let’s see how far we’ve come.
http://www.sdss.org/includes/sideimages/orangespider.html
http://en.wikipedia.org/wiki/Cosmic_Background_Explorer
Imagine that you have the opportunity to point the
Hubble Space Telescope anywhere you want. What
would you choose to look at with the most amazing
instrument ever built for astronomy?
Robert Williams, Director of the Hubble Space
Telescope Science Institute, chose a most surprising
target—nothing at all. That is, a place in space that had
no planets or stars or visible galaxies. The quietest,
darkest place he could find.
He was rewarded with an image of thousands of
galaxies! The Hubble Deep Field image has become one
of the most remarkable findings of the space age, and
has again vastly expanded our vision of the cosmos.
1998: Saul Perlmutter and Brian Schmidt
Discover Runaway Universe
It’s really getting complicated now!
Type 1A's supernovas are not all the same luminosity,
but like Cepheids, the faster ones are dimmer, so we can figure out
how absolute magniitude seeing how fast they vary
That enabled two different teams to measure the distance to
each supernova. Distance is also an indicator of time since we
observe a supernova 5 billion light years away as it appeared
5 billion years ago. They also measured the Supernova’s
red shift to determine how fast the universe was
expanding at that time. The amazing result is that the
expansion of the universe is not slowing due to gravity.
It is now expanding faster than in the past.
Some unseen force must be causing the acceleration.
This is unknown force is called “dark energy.”
1998: Saul Perlmutter and Brian Schmidt
Discover Runaway Universe
The result of these findings is that we know less about the universe
than we thought we did. Thanks to these findings and the WMAP
satellite data, we now know that:
Only 4% of the mass in the universe is visible as stars and galaxies.
About 23% of the universe is “dark matter.”
About 72% of the universe is dark energy, accelerating
the expanding universe.
For more info go to : http://cosmology.carnegiescience.edu/timeline/1610
Now that we
think we know
how it all may
have begun, the
big question is…
How will it all end?
For years the two
main theories were
the Big Chill and the
Big Crunch.
In the Big Chill
The universe would
continue expanding
Until galaxies, stars, planets, and dust
drifted so far apart
That it seemed the universe contained
nothing
In the Big Crunch the
universe would continue
to expand until gravity
forced it to
collapse back in on itself.
Today, a new
theory is coming
to light. This
theory is based on
some new ideasdark matter and
dark energy.
Material that is believed to make up more
than 90% of the mass of the universe, but is
not readily visible because it neither emits
nor reflects electromagnetic radiation,
such as light or radio signals. Its
composition is unknown.
www.genesismission.org/glossary.html
When we gaze up at the night time sky, we see the
shining stars in the blackness of space. But is the
space empty?
In the 1950s a young American scientist discovered
that stars in rotating spiral galaxies seem to be held
together by an unseen force. Vera Rubin proposed the
idea that the space between the stars was filled with
invisible stuff she called dark matter.
Scientists now believe that dark matter could make up
an unbelievable 99% of the universe. The density of the
universe determines whether it will expand forever or
eventually shrink back in a reverse of the Big Bang,
otherwise known as the Big Crunch.
Since we began talking about and looking for dark matter,
scientists began theorizing about another force- dark energy
The residual energy in empty space which is
causing the expansion of the Universe to
accelerate. Einstein's Cosmological Constant
was a special form of dark energy.
Maybe Einstein was right afterall!
Universe.gsfc.nasa.gov/resources/glossary.html
What’s the difference?
Dark matter acts like particles- it may be
found in the spaces between all the dust
and gas in space.
Dark energy is a force that repels- almost
like the ends of a magnet repel each
other. This force may be causing the
expansion of the universe to accelerate.
There is recent evidence to suggest both
of these are possible!
Blue-70% the amount of dark energy contained in our universe
Red- 25% the amount of dark matter contained in our universe
Yellow- 5% the rest of the material in the universe including atoms,
molecules, dust, gas, stars, and planets!
http://pancake.uchicago.edu/~carroll/preposterous.html
Who knows what the future holds- it all
remains to be seen!
From “Fire and Ice” by Robert Frost
“Some say the world will end in fire;
Some say in ice.
From what I've tasted of desire
I hold with those who favor fire.”
From “The Hollow Man” by T.S. Eliot
"This is the way the world ends
Not with a bang but a whimper,"