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13.7: Cosmos And Culture
Thu March 21, 2013
Planck Data: Universe Older And Slower
Originally published on Thu March 21, 2013 9:01 pm
Scientists from the European Space Agency announced results Thursday from 15.5 months of operation of their Planck satellite mission. Results were eagerly awaited by the astronomical community, as they achieved higher precision than the earlier American mission WMAP. Both satellites measured the tiny temperature fluctuations on the microwave radiation left over from when the first atoms were made, some 400,000 years after the Big Bang. This radiation bathes the whole cosmos and is an imprint of its infancy.
In short, Planck's high precision data reveals a Universe very much as we have grown used to, albeit with some new twists. It's older, its age being revised to 13.796 billion years, or about 13.8. We may need to update the name of this blog to reflect the advances of science!
The material composition remains as before, with ordinary matter, dark matter and dark energy the three main constituents. The relative abundances have changed a bit, with dark energy being now just below 70 percent of the total and dark matter going up a bit. Given that dark energy is responsible for pushing space apart (read: accelerate cosmic expansion), the cosmos seems a bit slower than we thought, although still going strong.
Planck also poses constraints on models from the Universe's distant infancy, known as inflationary scenarios. Those propose that early on the Universe went through a period of exceedingly fast expansion (the inflationary epoch). During the spatial stretching, small quantum fluctuations in the primordial matter fields got amplified to astronomical values and became the seeds for the growth of galaxies later on. Inflation predicts that the largest objects we see today came from the smallest fluctuations we can conceive of. Data from Planck has constrained the possible models, pushing some of them out of the plausibility range; theorists will have to get busy to figure out what still works. In essence, primordial quantum fluctuations seem to be truly random, not showing any signs of unusual clustering. This finding is, perhaps, a bit more boring that we had hoped for.
More of a surprise is with the anomalies found at large cosmic distances. There seems to be a bias in the Universe, where one side displays larger temperature fluctuations than the other. We are not sure why this is; it may be still a statistical fluke (although unlikely at this point). But any sort of asymmetry is the signature of some unusual process that may reveal some new physics. Stay tuned for more.
Finally, the data also didn't find any evidence of an unusual topology for the Universe. At least within what is visible to us, the cosmos seems very flat indeed.
All in all, the Planck data so far gives confidence that cosmology is on the right track to explain the Universe in which we live. If only we could figure out the nature of dark matter and dark energy.