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March 27, 2011

Shuttle Endeavour's Mission and the Matter of Anti-Matter

Scientists hope to learn more about the origins of the universe once a sophisticated particle detector arrives at the earth-orbiting International Space Station and starts searching for anti-matter and dark matter. Researchers explained their goals for the Alpha Magnetic Spectrometer and the upcoming shuttle Endeavour mission at a NASA mission preview briefing in late March.  

The primary objective of this 14-day mission is to deliver the Alpha Magnetic Spectrometer to the space station. Endeavour's commander, Mark Kelly, told journalists at a mission preview briefing at Johnson Space Center that this sophisticated instrument has been in development for 16 years.  

"It's going to look for anti-matter, dark matter, dark energy," said Kelly. "It's a collaboration from 16 different countries with 600 scientists, so we're pretty excited about what this means for science aboard the ISS and for, you know, real science on the origin of the universe."

Anti-matter. Dark matter. Origin of the universe. It all sounds pretty intimidating.

Not so, said the Alpha Magnetic Spectrometer's principal investigator, Samuel Ting of the Massachusetts Institute of Technology. "In physics, everything appears to be complicated, but the basic idea is always very simple."

He said our understanding of the universe comes from our understanding of light rays. But the visible matter in the universe makes up only a fraction of the total mass that is known to exist.

"We know 90 percent of the matter in the universe cannot be seen," said Ting. "Because you cannot see it, that's why you call it dark matter. Nobody knows what dark matter is because you cannot see it."

But, Ting explained, just because you cannot see it does not mean you cannot detect it. He said the collision of dark matter with dark matter can produce particles, and if you calculate the number of particles produced in those collisions, you would see that the total is higher than what you would expect if you were measuring only ordinary cosmic ray collisions.

That sum, he said, gives you a hint of the non-visible part of the universe. So, that's dark matter. Then there is the matter of anti-matter.

"If the universe came from the Big Bang, before the Big Bang, it is a vacuum," said Ting. "Nothing exists in a vacuum. So, at the beginning, you have an electron, you must have a positron, so the charge is balanced. So you have matter, you must have anti-matter. Otherwise you would not have come from a vacuum."

The Alpha Magnetic Spectrometer is a sophisticated detector that will look for elusive evidence of anti-matter, searching for anti-carbon and anti-helium among all the discernible particles. Ting used a down-to-earth example to explain this spectrometer's extraordinary precision.

"In the city of Houston, during a rainy season, you have about 10 billion raindrops per second. If you want to find one that's of a different color, it's somewhat difficult," said Ting.

The spectrometer that will be mounted to the space station's truss will search for the equivalent of that raindrop of a different color. It will give a glimpse of what can be detected, but cannot be seen. That, Ting explained, is what makes the space station such an amazing orbiting laboratory.