Physicists have puzzled for decades over a form of matter that makes up 90 per cent of galaxies, including our own Milky Way, but which they've never seen.
Now they may finally have solved the mystery of ''dark matter''.
The answer may come from Sam Ting, a Nobel laureate in physics who recently said his forthcoming paper on the nature of dark matter, likely to be published this month, ''will not be a minor paper''.
Physicists who met this past weekend for a dark matter workshop at Texas A&M University certainly hope so.
Scientists know dark matter exists because without it they cannot explain why galaxies, which rotate in space at enormous speeds, do not fly apart and instead remain a cohesive unit. Of the matter astronomers can observe, there simply isn't enough gravity to hold galaxies together.
Without dark matter, physicists say, there might not have been enough matter to clump together to form galaxies and stars.
And yet an eminent physicist like Bhaskar Dutta, at Texas A&M, admits: ''We still don't know what the nature of dark matter is, nor what the origin of dark matter is.''
So, does Professor Ting, a physicist at the Massachusetts Institute of Technology, have the answer?
In May 2011, a NASA space shuttle installed the Alpha Magnetic Spectrometer to the exterior of the International Space Station.
Inside the $US1.5 billion instrument - for which Professor Ting led the development over a 15-year period - are extremely sensitive magnets and detectors that can collect and sort through millions of cosmic ray impacts a day.
Physicists believe some of these cosmic rays might be the result of collisions by dark matter particles, and it's likely that Professor Ting has found what he believes are the signatures of these collisions. His forthcoming paper represents the first findings from the instrument.
Once Professor Ting publishes his research paper, Dr Dutta said, scientists will seek to rule out other explanations for what he has observed. If all other phenomena can be ruled out, then dark matter will be explained by what's left.
And while it is frustrating to scientists that they don't yet understand such a fundamental component of the universe, Dr Dutta offered some perspective.
In ancient times, he said, people believed there were four elements: earth, air, fire and water. During the Enlightenment scientists began to discern and describe various elements and developed the Periodic Table.
Then, during the 20th century, scientists discovered that individual atoms were not finite, and instead made up of smaller components.
''It took us many thousands of years to understand the nature of ordinary matter,'' Dr Dutta said. ''I'm hopeful we can understand dark matter in a shorter number of years.''