Hank Green: It's really not all that often that you hear the words 'breaking' and 'physics' and 'news' all in the same sentence.  I mean, news about the laws of the physical universe that's so important that we drop everything and interrupt our regular programming to bring it to you, but that's exactly what we did around this time last year on SciShow, and this week, on SciShow Space, we're doing it again.

This week, after several months of research and analysis, it turns out that physics can be really complicated.

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Let's start with the breaking physics news I gave you last year.  It came from the South Pole, where a telescope called Bicep2 had been analyzing the cosmic microwave background radiation or CMB.  That's the almost 14 billion year old glow left over from the Big Bang that permeates the whole universe.  Last March, astronomers working with BICEP2 announced something that sounded incredible.  They'd found what we can best describe as a swirling pattern in the cosmic background radiation, and it promised to revolutionize our understanding of the formation of the universe.  Because these swirls of energy were the signature of gravitational waves, waves in the fabric of space/time that Einstein himself predicted should exist, although we've never been able to prove that they really do.

But if we could, it would verify one of the leading theories about how the universe formed, a model called 'cosmic inflation'.  This theory proposes that the universe expanded extremely quickly right after the Big Bang.  And when I say extremely quickly, I'm talking, like, 10^-35 seconds after it, and then quickly it slowed down.  But there's even more to it than that.  Not only would proof of cosmic inflation basically tell us how the universe was born, which, y'know, would be pretty interesting to find out, it could also help us reconcile the two major models of modern physics: general relativity, which describes how gravity affects objects in space and time, and quantum mechanics, which explains the weird behavior of the tiniest known particles in the universe.  

So if these waves had turned out to be real, that team woulda had their Nobel Prize in the bag.  And lots of people, including me, were understandably excited about it.  But by the time the results were published in June, the researcher were starting to have some doubts.  And now, after months of analysis of a whole new set of data by more than 200 scientists, it's looking like most of the signals that BICEP2 discovered weren't actually caused by gravitational waves.  

It turns out what they found was just a bit of dust, but how could they tell?  Well, normally, electromagnetic waves don't care which direction they oscillate in, but waves that are polarized have picked a direction and they're stickin' to it.  And the swirls of energy that BICEP2 observed were polarized in a very particular pattern, in a way that apparently only gravitational waves could account for.  But a lot of scientists weren't convinced.  Their main concern was that the signal could have been caused by interstellar dust, which also polarizes radiation in the same way and could have created the same patterns.  

As it happens, soon after the findings from the South Pole were announced, new maps were released that showed where the biggest clusters of interstellar dust were.  And sure enough, they showed that there was more dust in the area where the signal came from than the team had known about.  Then came the Planck Observatory.  A space telescope launched in 2009 by the European Space Agency, Planck was also studying the cosmic microwave background.  But while BICEP2 could only analyze it at one range of frequencies, Planck could study nine, and it found that dust was polarizing radiation in the same pattern all over the place including the section of the sky BICEP2 was looking at.  

So after combining the Planck data with the BICEP2 data, those 200 scientists concluded that the patterns that everyone was so excited about last year were mostly caused by dust.  But the search is not over, because those patterns may partly have been the effects of gravitational waves.  It just turns out that if you take out all the noise that we know is being created by dust, the signals caused by gravitational waves are a lot weaker than we thought.  

So like I said, physics can be complicated and for these folks, probably pretty frustrating.  But still, a negative result can be just as important as a positive one.  Now we know that if there are gravitational waves out there, we're gonna need technology that's much more sensitive if we're gonna find 'em.  And fortunately, the next generation of BICEP telescopes, called BICEP3, just went online last month, so we still may track down some evidence of the gravitational waves and prove Einstein right.  And if that happens, there will be yet more breaking physics news coming your way.  

For now, thanks for joining me on SciShow Space News.  If you wanna help make SciShow happen, you can check out Subbable.com/SciShow where you can get perks like a SciShow tie or a set of buttons, I'm wearing one right here.  And also, don't forget to go to YouTube.com/SciShow Space and subscribe.

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