Shedding light on dark matter


April 8, 2013

[Dave Heller] Astronomers move a step closer to shedding light on dark matter, the stuff surmised to be leftover particles from the Big Bang. Let’s get out our flashlights with Derrick Pitts, chief astronomer at the Franklin Institute. Derrick, is it the dark matter particles are uniquely left over from the Big Bang, or are you and I and everything here derivative of that singular moment?

[Derrick Pitts] Well, we’re all derivative of that singular moment but what we’re actually looking for is to see how much of what is derivative is taken up in the universe. One of the things we have learned in the last decade or so is that only 4% of all of the stuff that’s here is what we call the real matter, the hard stuff — the stars, planets, galaxies, nebulae, and things like that — and the other 96% is divided between dark matter and dark energy. And so, in our effort to try to really sus out the existence of these things, we see the effect that they had on the expansion of the universe and we try to determine does this really exist? Because as such, it doesn’t release any energy that we can detect in the way that we can directly detect energy coming from any other source.

  • Dark Matter

    This composite image shows the distribution of dark matter, galaxies, and hot gas in the core of the merging galaxy cluster Abell 520, formed from a violent collision of massive galaxy clusters. Superimposed on the image are “false-colored” maps showing the concentration of starlight, hot gas, and dark matter in the cluster. Image credit: NASA

So was it initially surmised as just a number to solve a mathematical equation, or is there even indirect evidence of it?

No, the big problem is that the universe is expanding; we can’t figure out why, and originally we thought it shouldn’t be expanding. So now we’ve discovered this energy that’s driving the universe ever larger. Yet we cannot identify the force itself or the mass that’s causing this to do that. So, how do we identify what’s going on? We’ve coined these terms now, dark matter and dark energy, to sort of hold, if you will, a place for the activity of what’s going on, that’s causing the expansion. But we really do know that there is something happening. We know there’s something happening, because we can detect its effect on everything else. The trick is, it’s almost like talking about a black hole in that you cannot “see” a black hole because visible light cannot escape from it. Dark matter and dark energy do not generate any visible radiation that we can detect that tells us that the stuff is there, although, our clear understanding now is that 96% of the universe is this dark matter and dark energy.

So what was behind that news story last week?

So what was behind the news story was there is a really marvelous device, a detector, that’s on board the International Space Station that is detecting somewhere around 25,000 cosmic ray hits per second. It’s been doing so over the last two years, and out of all of those incredible number of hits, it has been able to identify a significant number of particles that are derivative from dark matter, dark energy activity. And this is close to the predicted range of what should be found. So this now leads one to believe that either there is a process connected to dark matter and dark energy that are generating these positrons, as they’re called, or there’s another explanation that has to be found. So it’s very, very important that we not just make this observation or take this data seriously. First of all, the announcement comes from 10% of the data that’s collected. So the trend is looking as if this is what we’re hoping to find to tell us more about dark matter and dark energy. But we do have to be able to either reproduce this somewhere else, or find another way to confirm this observation. So when we look at the large hedron collider, it too was looking for the same kinds of answers, but in a different direction. So if we can pool all of these observations together, we might be able to put all of the pieces of the puzzle together and end up with the whole picture.

And should that whole picture be forthcoming, that “eureka moment” analogous to say, solving the human genome?

I would say so. Because if we can understand what the story is behind dark matter and dark energy it tells us so much more about what the real driving forces of the development and dynamics of the universe actually are.

  • International Space Station

    The newly-installed Alpha Magnetic Spectrometer-2 is visible at center of the International Space Station’s starboard truss. The Alpha Magnetic Spectrometer, or AMS, is the largest scientific collaboration to use the orbital laboratory. This investigation is sponsored by the U.S. Department of Energy and made possible by funding from 16 nations. Led by Nobel Laureate Samuel Ting, more than 600 physicists from around the globe will be able to participate in the data generated from this particle physics detector. The mission of the AMS is, in part, to seek answers to the mysteries of antimatter, dark matter and cosmic ray propagation in the universe. Image credit: NASA

The Mars Rover is taking a siesta this month

Well the truth of the matter is, that if we look at the position of Mars relative to Earth and relative to the sun, what we find is that we’re on opposite sides of the sun. So here on Earth where the Rover controllers are, we can’t really see or easily transmit radio signals or messages to the Rover when it’s on the opposite side of the sun. So to compensate for this lack of contact, what has been done is taht commands have been uploaded prior to the blockage of the sun to both the Curiosity Rover and the other rovers operating on the surface of Mars, which of course would just be Opportunity still. But providing those instructions for what these explorers can do allows them to operate on their own for about a month.

Now let’s harken all the way back to the anniversary of the very first man-space flight.

This Friday, April the 12, marks the 52nd anniversary of Yuri Gagarin’s flight in space. Yuri Gagarin was a Russian astronaut who made the first trip in space for humans and became, of course, a world hero for doing so. He unfortunately died in a crash of a MiG-15UTI test flight back in 1968. But, had he lived, he’d be 79 years old today and what an incredible story he’d have to tell.

Was that very first man flight a mere up and down, or around and around?

No, in fact for Yuri Gagarin it was an orbital flight. So as the first astronaut, he made the first orbital trip around the planet. Unlike the Americans, who followed on less than a month later, will Alan Shepard’s flight in early May in which it was just an up and down flight. The first American to orbit the Earth was John Glenn, and John orbited the Earth three times, but that was the very next year in 1962, in February of 1962.

  • Yuri Gagarin

    On April 12, 1961, the era of human spaceflight began when the Cosmonaut Yuri Gagarin became the first human to orbit the Earth in his Vostock I spacecraft. The flight lasted 108 minutes. Image credit: NASA

WHYY is your source for fact-based, in-depth journalism and information. As a nonprofit organization, we rely on financial support from readers like you. Please give today.

Want a digest of WHYY’s programs, events & stories? Sign up for our weekly newsletter.

Together we can reach 100% of WHYY’s fiscal year goal