Based upon what we can see in space, galaxies should not exist.
All the stars in the Milky Way should not produce enough gravity to hold themselves together.
To explain this extra gravity, physicists have theorized there is dark matter in the universe — invisible to even our most specialized scientific instruments.
In fact, physicists have a great deal of evidence suggesting there’s more dark matter than visible matter — up to 80 percent of our universe’s mass may be dark matter.
Even though scientists estimate how much dark matter exists, they know next to nothing about what it is.
The leading hypothesis is dark matter is composed of weakly interacting massive particles, or WIMPs. The name fits surprisingly well.
They have a mass and therefore produce the gravity, but otherwise they hardly interact with normal matter.
WIMPs occasionally bump into normal matter. Physicists have been trying to use this fact to detect them, and throughout more than a decade, one lab has been successful.
This lab, the Gran Sasso, is a massive facility built under a mountain east of Rome.
The facility houses a dark matter detector protected from background noise by 1400 meters of earth.
The dark matter detector consists of ultra-pure crystals of sodium iodide, which emits flashes of light when struck by WIMPs.
The facility not only sees the flashes of light, but also the seasonal variations.
This variation is what physicists take as a sign they’re due to collisions with WIMPs and not noise, such as cosmic radiation.
Cosmic radiation constantly rains down upon the earth, but dark matter floats around us with an unsettling stillness, like an invisible cosmic haze.
This means the flashes in the detector should be more frequent when the Earth passes closer to the sun and moves slightly faster through the surrounding dark matter cloud.
This is exactly what the team at the Gran Sasso observed.
Unfortunately, this is not enough to convince everyone the team has successfully detected dark matter because Gran Sasso is the only facility using the sodium iodide method.
Other teams around the globe are now trying to replicate their results.
Growing sodium iodide pure enough to use in a detector is not a trivial task.
It is highly prone to contamination by radioactive potassium, which renders the crystals useless.
Two teams, one based at Yale University in Connecticut and another at University of Zaragoza in Spain, have enough sodium iodide to put additional detectors beneath mountains in Spain, South Korea and Australia.
Having detectors in both the northern and southern hemispheres is crucial to the project, as it will allow scientists to determine if the patterns in their data are caused by environmental factors or indeed by the position of the earth around the sun.
Should these new detectors see the same pattern as Gran Sasso, it may confirm the existence of dark matter, but there will still be skeptics.
Some think the scientists will simply find a previously unknown source of background noise, but others hope the team will fly straight to Stockholm to collect a Nobel Prize.
jaykgold@indiana.edu
@JayKeche
