Cosmology is quintessential popular science, but I always regarded it as the most dismal field of physics because there is no avenue for experiments to keep run-away speculations at bay. It’s like trying to catch a perpetrator by staring at a multi-billion year old crime scene with the evidence all scattered. And of course, since it deals with the beginning of time, scientists may have a hard time divorcing themselves from philosophical or religious beliefs (e.g. for a long time, Einstein presumably regarded the big bang theory as an invention by the clergy).
Given the ad-hoc nature of the cosmic inflation theory to fix problems with the big bang explanation, I always felt rather lukewarm about it. It just appeared too much like a convenient quick fix. But I am certainly warming up to it, given that the new detailed observations of the cosmic microwave radiation do fit the picture quite nicely. This radiation is essentially a convenient thermometer for the entire universe, as it can be regarded as thermal black body radiation. This is as close as we can get to the aforementioned primordial crime scene, taking advantage of the fact that the further we look into space, the earlier the events we observe. If the mainstream big bang theory is correct, then the evidence for it must be splattered all over space encoded in this background radiation.
Brian Dodson (one of the finest pop science writers on the web) nicely explains why this data is such a treasure trove. I have little to add to his article other than the caveat that one should keep an open mind, that the evidence may yet still fit a completely different sequence of events (e.g. this one made some recent headlines, and it will be interesting to observe how such alternative models may be adapted to fit the newly released data).
And then there is, of course, the other raison d’etre of this blog, pointing out when popular science writing gets the details wrong. The better outlets, such as the NYT, got it right when they wrote that this data offers the first direct evidence for gravitational waves as predicted by general relativity. And a layman certainly can relate to this, simply by appreciating the released pictures, that almost look like ripples left in the sand by some ocean waves.
But there are a lot of press releases and news blurbs that leave out that crucial word “direct” when mentioning gravitational waves, ignoring the excellent indirect evidence that earned a Nobel prize in 1993. The latter is based on one of the neatest astronomical observations I can think of, which used the precise signal of a pulsar in a binary system to measure the declining orbit of the two stars. The observed orbital decay precisely matches the theoretical predictions of how much energy the system should disseminate via gravitational waves.
Of course, gravitational waves have the huge advantage of being the kind of physics accessible to immediate measurement, and this new cosmological evidence gives credence to the persistence in pushing for better gravitational wave detectors to eventually measure these waves directly.
It didn’t take long before some prominent push back, pointing to discrepancies between the BICEP2 data and previous data from the Planck and WMAP telescopes.
(h/t Sol Warda for prompting me to write this post)