Yeah desh, its beautiful alright....
Recently, two high
TKF: Last year an experiment called BICEP2, which you work on Clem, announced evidence of gravitational waves — ripples in the fabric of space that would be evidence of inflation. Since then, and after new analysis, the conclusions have been reframed. Can you explain not only where we're at now, but also more broadly in what ways this might change how future experiments are designed.
C.P.: About a year ago, we announced that we had detected this so called swirliness, this B-mode in the microwave background polarization pattern. Now, a potential source of such swirliness is gravitational waves. These are ripples in the fabric of space-time that originated at the very, very first instant of the universe, an imaginably small fraction of a second after the beginning. Inflation, if it occurred, perhaps injected these ripples into the fabric of space-time. What we can potentially see is the signature that they imprint into the pattern of the microwave background at about 400,000 years after the beginning. That's what we were looking for. [Time Travel and Wormholes: Physicist Kip Thorne's Wildest Theories ]
Now, we found such a swirly pattern and we announced that and it generated a huge amount of excitement. But it turns out that emissions from galactic dust can also produce potentially such a swirly pattern. The new analysis that's just come out in conjunction with Planck seems to indicate that a substantial fraction — and perhaps all — of the signal that we've detected is in fact from galactic dust and not from these exotic gravitational waves from the beginning of the universe.
Planck space telescope conception
The European Space Agency (ESA) Planck space telescope was launched in 2009. During its four-year mission, it observed variations in the cosmic microwave background across the entire sky. The first all-sky map was released in March 2013 and the second, more detailed, map was released in February 2015. The mission's successes include determining that the universe is slightly older than thought; mapping the early universe's subtle fluctuations in temperature and polarization, which eventually gave rise to the structure we see today; and confirming that 26 percent of the universe is composed of dark matter.
Credit: ESA
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TKF: Will future experiments be designed differently as a result?
C.P.: The basic experimental technique remains the same, but it becomes necessary to make observations at more than one frequency. Up until now, BICEP2 and the Keck Array, its sister experiment, have been concentrating all their sensitivity at a frequency of 150 gigahertz, 150 billion cycles per second. That's a good frequency to hit if you're looking for the microwave background. If you want to disentangle the dust component, you also want to have observations at other frequencies — potentially higher frequencies where the dust is stronger so you can get a better measurement of it and then remove it from the lower frequency measurements. That's where everybody always knew that it needed to go, but now it looks like we need to go there perhaps a little sooner than we anticipated. Frequency diversity is the future.
