Expanding+Universe



Intro
Is our universe expanding? How can we be sure? Is it finite or infinite? For thousands of years scientists and astronomers alike have battled with these and other questions of our universe. There are so many questions circling around the topic of our expanding universe. Hopefully our Wiki page will answer your questions and clarify what exactly is going on with the expansion of our universe. This Wiki page was brought to you by Georgia Vatcher and Bridget Walsh.

**Is the Universe expanding?**
Scientist believe that the universe is expanding, and these three scientist work lead to this conclusion

** Vesto Slipher: **  
 * Albert Einstein**
 *  [[image:AlbertEinstein.jpg width="125" height="125" align="right" caption="Albert Einstein"]]In 1915 Albert Einstein wrote the general theory of relativity
 * His theory explained how gravity works
 *  When he applied his new theory to the whole universe, it predicated that space should not be stable, it should be expanding or contracting 
 *  He refused to believe his own equation he believed that the size of the earth has not changed.
 * During this time, a astronomer at Lowell observatory in Flagstaff Arizona , named Vesta Slipher was ending a study of the night sky
 * One night while looking though his telescope he saw several fain fizzy objects called nebulae. [[image:http://2.bp.blogspot.com/_1CASmuUog1s/SRkJxLT-teI/AAAAAAAAccI/KedwJQdCIW0/s320/Vesto+Slipher.jpg width="123" height="145" align="right" caption="Vesto Slipher"]]
 * The light given off from the nebulae was redder than it should have been, he knew that this meant the nebulae was moving away from the earth.
 * He calculated the nebulae speed from the redness of their light and was shocked to find that the nebulae was moving 2.5 million miles per hour away from the earth.
 * Edwin Hubble **
 * In 1923 Edwin Hubble used the new 100- inch telescope, the largest in the world at the time to prove that some on the nebulae are actually other galaxies similar to out Milky Way.
 * He spent the rest of the decade using the telescope, trying to find creative ways to measure the distances to hundreds of[[image:http://quest.nasa.gov/hst/images/EdwinHubble2.gif width="124" height="172" align="right" caption="Edwin Hubble using the 100-inch telescope"]] galaxies.
 * <span style="font-size: 10pt; font-family: Arial,Helvetica,sans-serif;">In 1929 he compared his distances to Sliphers measurements of light and made a plot, which is now known a Hubble diagram.
 * <span style="font-size: 10pt; font-family: Arial,Helvetica,sans-serif;">His diagrams showed the redness of galaxies light and the speed in which the galaxy moved away from the earth, increased as it moved away from earth, and that increase created a straight line on the graph.
 * <span style="font-size: 10pt; font-family: Arial,Helvetica,sans-serif;">He realized that we were not the center of the universe, and it was impossible that we were, he saw this same pattern on his graph every way he looked in the sky, the best explanation is that the entire universe is expanding, which is what Einstein said.

The Discovery of The Expanding Universe
--Proffessor Edwin Hubble made the discovery of the expanding universe

--This discovery was made in 1929 while working at the Carnegie Observatories in Pasadena, California
 * --He did this by mesuring the **redshifts** of a number of different galaxies, this became known as Hubble's law which lead directly to establish that the universe is expanding.


 * Hubble's law** is an equation that descibes this expansion:
 * The equation is often expressed as v = H0D
 * H0 the constant of proportionality between the distance D to a galaxy and its velocity v.
 * H0 is often spoke of as **Hubble's constant**

**Evidence of an Expanding Universe-Red shift**

 * Before we can talk about redshifts we must review the properties of light:
 * Light is a form of energy that travels as a **wavelength** [[image:http://science-edu.larc.nasa.gov/EDDOCS/images/Erb/Red_Spectrum.jpg align="right" caption="Red Spectrum."]]
 * Each color has a wavelength
 * Longest wavelengthes are red to the shortest wavelengthes, violet
 * Edwin Hubble looked at distant sources of light in our galaxy and noticed the pattern of the spectrum but observed the colours of the lines are not the same as he expected.
 * Lines move toward the red end of the spectrum meaning they have a longer wavelength
 * Astronomers conclude that the light has a longer wavelength because the galaxy is moving away from us or **expanding**
 * This movement into the red end of the spectrum is called **red shift**

**Example**

 * Imagine a duck floating stationary in a pond:
 * the duck represents a source of energy
 * the ripples that spread out from the duck represent the waves of energy (wavelengthes)
 * Imagine the duck moves toward you
 * If the duck swims toward you the wavelngthes will be squished together and become shorter
 * The waves behind the duck however, spread further apart
 * Longer wavelengthes= duck is moving away from you
 * Shorter wavelengthes= duck is moving towards you
 * The expansion of our universe is much the same, astronomers observe longer wavelengthes through red shift. Therefore we can concur that the universe is expanding; it is moving //**away**// from us

The Big Bang Theory

 * Because the galaxies are moving apart scientist believe that at one point the galaxies w[[image:http://images-cdn01.associatedcontent.com/image/A2983/298321/300_298321.gif width="172" height="162" align="right" caption="Model of the big bang theory"]]ere closer together
 * They believe that there was even a “time zero” this is thought to have been 10-15 billion years ago.
 * In this “time zero” they believed that all the matter of the universe was compact into a little dense, hot mass under enormous pressure.
 * The big bang is when the universe came out of this state of high density and temperature

**The Doppler Effect**
<span style="font-family: Arial,Helvetica,sans-serif;"> **<span style="font-family: Arial,Helvetica,sans-serif;">Example: An Ambulance **
 * <span style="font-family: Arial,Helvetica,sans-serif;">An Australian physicist Christian Doppler discovered that tones pitch changes depending if it is approaching or going.
 * when it approaches the sound waves from the siren are compressed towards you, and because it is closer the intervals between those waves are smaller there is an increase in pitch and frequency
 * when it drives away the sirens sound waves are stretched, thus the sirens pitch is decreased
 * One can tell if the ambulance is coming closer or farther away depending by the pitch of the siren.

If we can measure the change of pitch, we are able to estimate the speed.
 * The electromagnetic radiation given off by an object while its moving also displays the Doppler effect
 * The radiation given off by an object moving towards something is squeezed, there is an increase of frequency and is said to be blue shifted.
 * When an object moves away the radiation given off is stretched and there is a decrease of frequency it is said to be red shifted. Blue shifts and red shifts are shown by stars galaxies and gas clouds, indicating their motions compared to the observer.


 * Electromagnetic Spectrum**
 * Was originally studied in the visible part of the electromagnetic spectrum, but now it applies to all electromagnetic waves of the spectrum.
 * Not only does red light have its own different frequency and wave length all colours do.
 * The waves vary in size, from long waves, as tall as the size of a building to short gamma-waves smaller than the size of the nucleus of an atom.


 * What is it used for?**
 * Astronomers use the Doppler shifts to calculate how fast stars and other objects in space move away and towards the earth.

Conclusion
In conclusion, you have to remember that SPACE is expanding, **not matter**. The galaxies retain their sizes. The positions of the galaxies shift as the __positions in space they occupy__ expand. A simple way to think of this is to imagine baking a loaf of raisin bread. As the bread rises it also expands. All of the raisins move farther apart from one another. So, just because we see all the galaxies moving away from us, it doesn't mean that we are at the center of the universe. Every single raisin would see all of the others moving awy from it. So to complete the analogy, all of the galaxies in the universe are like the raisins in the bread. The raisins themselves are not expanding but the bread, which represents space, is.

There are still many questions about our universe that have still gone unanswered but with the help of modern science hopefully we are getting closer to understand the fabric of our universe.

**Citations:**
[|Galaxy redshifts reconsidered - The Astronomy Cafe, Dr. Sten Odenwald]

Hirsdh, Alan J.,Evidence of an Exapanding Universe, Geraldine Kukuta, Science 9, Susan Green,Nelson Thompson Learning, 1999, pg 476-477

__The Expanding Universe__. Sloan Digital Sky Survey. Mar.-Apr. 2009 <http://skyserver.sdss.org/dr1/en/astro/universe/universe.asp>

NASA. "Electromagnetic Waves have different wavelengths." __Electromagnetic Waves have different wavelengths__. Mar.-Apr. 2007. NASA. May-June 2209 <http://science.hq.nasa.gov/kids/imagers/ems/waves3.html>.l

__Expanding Universe__. The board of trustees at the University of Illinious. Jan.-Feb. 2002 <http://archive.ncsa.uiuc.edu/Cyberia/Cosmos/ExpandUni.html

__Big Bang__. Wikipedia. 3 June 2009 <http://en.wikipedia.org/wiki/Big_Bang>.