cosmology- the study of the origin, present, and future of the universe

Cosmology- the study of the origin, present, and future of the universe.

http://www.damtp.cam.ac.uk/user/gr/public/bb_cosmo.html

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.

Einstein and Gravity

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

http://cosmology.carnegiescience.edu/timeline/1920

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!

Shapley actually measure our universe. He found it to be About 100,000 light-years across.

• 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! 

Red Shift

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 to the ‘Doppler Effect’.

By Golly, just look at that!

The dark lines in the

spectrum on the right hand side are ‘red

shifted’.

Light from the Sun

Light from 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.

• 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

Speed of recession (m/s) = Hubble Constant (s-1) x distance (km)

http://www.charleroi.be/anglais/ehisto_1.htm

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.

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 movie- only 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

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.

http://www.space.com/scienceastronomy/astronomy/hoyle_obit_010822.html

Sir Fred Hoyle

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

Dark MatterThere’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 elsethere- dark matter!

http://www.nasa.gov/mission_pages/hubble/news/dark_matter_ring_feature.html

Mapping the UniverseThere’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

1992 , Smoot and Mather show that slight differences in temperature found with

COBE could create the galaxies and stars

we see today.

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.

1995 Robert Williams and the Hubble Deep Field Image

1995 Robert Williams and the Hubble Deep Field Image

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 ideas- dark 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!

http://pancake.uchicago.edu/~carroll/preposterous.html

Blue-70% the amount of dark energy contained in our universeRed- 25% the amount of dark matter contained in our universeYellow- 5% the rest of the material in the universe including atoms, molecules, dust, gas, stars, and planets!

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,"