Learning about Dark Matter

Today Dr. Bellis posted my simulations on a website so other people can view it~~ :)
Link: http://www.sos.siena.edu/~mbellis/ew_processing/spring_2013.html

It was really fascinating to watch him make the webpage... I couldn't play with it because the program was on his computer. With HTML codes. While he was making the webpage, I searched about HTML codes, maybe next time I can try to get it on my computer (the codes are not that complex), and added mouse tracker for the projectile motion simulation. Our goal is to place a button that will start and stop the ball on the simulation and be able to place the mouse on the ball to see it's location at different times (which I have already done, but not the buttons... still discovering how to do that).


The next thing that I did was to do the worksheet on GoogleDoc about Dark Matter, because we are going to start making the Dark Matter simulations soon. My mentor has a meeting from 3:30 to the end of my internship, so I did the worksheet while he was away.
Here is the work that I've done:

For this assignment, I’ve given you some questions to answer that will hopefully teach you a bit about Dark Matter. You need only answer in a few sentences...or a paragraph at most. Feel free to use Wikipedia or other website, but put the link in this document from where you got the material. Let me know if you have any questions!

Who was Vera Rubin? (picture from Wikipedia)

Vera Rubin is a woman who discovered the galaxy rotation problem (the discrepancy between the predicted angular motion of galaxies and the observed motion) by studying galaxy rotation curves which led to the theory of Dark Matter.
A: Predicted value
B: Observed value.

The link to galaxy rotation problem: http://www.popscicoll.org/dark-matter/galaxy-rotation-problem.html
Theory for the rotational speed claimed that as the stars are farther out from the center the speed will be less but in reality the speed did not change. → Raises the question that there might be some kind of matter that exerts an extra pull on the stars to cause it to have a higher speed.

Who was Fritz Zwicky?
Published extreme concepts of the 1930s—neutron stars, galactic gravitational lensing, supernovas.

Discovered and named the concept of “Dark Matter”.

While observing the rotation of galaxies (which do not orbit around a central heavy object like the sun) and wanting to determine the velocity of the galaxies, he applied the virial theorem. “A straightforward application of classical mechanics, the virial theorem relates the velocity of orbiting objects to the amount of gravitational force acting on them. Isaac Newton's theory tells us that gravitational force is proportional to the masses of the objects involved, so Zwicky was able to calculate the total mass of the Coma Cluster from his measured galactic velocities. Zwicky also measured the total light output of all the cluster's galaxies, which contain about a trillion stars altogether. When he compared the ratio of the total light output to the mass of the Coma Cluster with a similar ratio for the nearby Kapteyn stellar system, he found the light output per unit mass for the cluster fell short of that from a single Kapteyn star by a factor of over 100. He reasoned that the Coma Cluster must contain a large amount of matter not accounted for by the light of the stars. He called it "dark matter." -http://www.learner.org/courses/physics/unit/text.html?unit=10&secNum=2

What is a WIMP, as it pertains to dark matter?
WIMPs are the subatomic particles which are not made up of ordinary matter. They are "weakly interacting" because they can pass through ordinary matter without any effects. They are "massive" in the sense of having mass (whether they are light or heavy depends on the particle).
Source: http://imagine.gsfc.nasa.gov/docs/teachers/galaxies/imagine/dark_matter.html

It is a candidate of the Dark Matter because Dark Matter also does not interact with other matters which is similar to the characteristics of WIMPs.

How big is the Milky Way galaxy?
The Milky Way is a barred spiral galaxy 100,000–120,000 light-years in diameter containing 200–400 billion stars. (Wikipedia).

How far is our sun from the center of our galaxy?
26,000 light years away from the center of Milky Way galaxy.
http://www.enchantedlearning.com/subjects/astronomy/solarsystem/where.shtml

How fast does the sun rotate around the center of the galaxy? (velocity in m/s)
The orbital speed of the Solar System about the center of the Galaxy is approximately 251 km/s. (Wikipedia)

How fast does the Earth rotate around the sun? (velocity in m/s)
The orbital speed of the Earth around the Sun averages about 30 km/s (108,000 km/h).
(Wikipedia)



:)