Dark Matter :: physics science space

absent Diagrams You, the computer youre sitting at, the air you breathe, even the distant stars argon all made up of protons electrons and neutrons. For a broad time this everyday matter, or what physicists like to call baryonic matter, was thought to be the main correct of the universe. provided, in the past twenty years evidence has been accumulating to the contrary, that in incident the universe is much stranger than ever thought of before and is approximately entirely made up of something that we cant see.For a long time astronomers werent concerned about the mass of objects that they couldnt see. For ensample the earth is too small and dim to see from any prominent distance and all the planets in out solar system experience up less than star percent of the total mass of the sun. However it soon became a concern when astronomers began to measure the mass of galactic thuds and it became patent that there was a significant amount of matter unaccounted for.In the thirtie s, astronomers named Zwicky and metalworker both examined closely two relatively nearby crews, the Coma thud and the Virgo cluster. They looked at the individual galaxies making up the clusters individually, and the velocities of the clusters. What they found was that the velocities of the galaxies were about a factor of ten to one hundred larger than they expected. In a cluster the main force is the gravitational pull of the galaxies on one another which gives rise to their velocities. By knowing the velocities of the galaxies the total mass of the cluster can be determined. If your web browser is Java-aware -- e.g., Netscape 2.0b or higher, try this experiment. It allows you to modify the mass inside a galaxy cluster, and watch the individual galaxies. experiment I ( Courtesy of Johns Homepage http//www.astro.queensu.ca/dursi/dm-tutorial/dm1.html) Now like all observations there is a certain amount of error involved. In this case, watching the galaxies in a cluster takes years of observation and the velocities are hard to determine callable to the expanse of the cluster. Its not like the experiment were the dots are whizzing around. in like manner some of the galaxies measured may not be in the cluster but are just in the line of site of the telescope.