Dark Side

An article by Phil Plait for Seed Magazine tells the story of how scientists have learned how to "see" dark matter.

After decades of attempts, astronomers have unveiled the dark side of the Universe.

I have to wonder if they finally resorted to alcohol in their "unveiling" attempts.

Dark matter was first thought of in the 1930's.

As time went on, more and more data suggested that the bulk of the Universe is invisible. Astronomers weren't thrilled with this (who wants to be told you can't see the majority of what you're trying to study?), but the evidence kept mounting. Galaxies rotated too quickly, implying that they had extra matter surrounding them in halos that were totally invisible. X-ray images revealed galaxies that were submerged in vast pools of million-degree gas, which should quickly dissipate unless the gravity from some unseen matter held it in place.

To simulate, get on a crowded bus of people who are leaving a bean and chili festival.

To see the dark matter, scientists decided to measure its only known effect: gravity. By measuring the distortion due to gravity of objects in space and comparing them with the expected distortion, astronomers were able to map out a 3-D view of dark matter. Since the far away dark matter is also being seen as it used to be, the map gives a view into the universe's past.

In the past, dark matter formed huge structures spanning hundreds of millions of light years across. But in more recent history, these enormous blobs have broken into smaller, scattered clumps.

Which indicates that the universe needs to eat more fiber.

For more details about this story, click on the link above.