As many of you know already, we’re expecting some very significant news Monday, presumably from the BICEP2 experiment. The rumors seem to concern a possible observation of “B-mode polarization in the cosmic microwave background radiation”, which, to the person on the street, could mean:
- strong evidence that inflation occurred in the early universe,
- strong evidence against certain alternatives to inflation,
- a rough measurement of how much dark energy was present during inflation and
- consequently a rough measurement of how hot the universe became when inflation ended.
It would also be cool for at least one other reason: it would be yet another indirect detection of gravitational waves, which are predicted in Einstein’s theory of gravity (but not Newton’s), just as electromagnetic waves were predicted by Maxwell’s theory of electricity and magnetism. Note, however, it would not be the first such indirect detection; that honor belongs to this Nobel-Prize-winning measurement of the behavior of a pair of neutron stars which orbit each other, one of which is a pulsar. (Attempts at direct detection are underway at LIGO.)
Of course, it’s possible the rumors aren’t correct, and that the implications will be completely different from what people currently expect. But the press release announcing the Monday press conference specifically said “significant discovery”, so at least it will be interesting, one way or the other.
If you have no idea, or a limited idea, of what I just said, or if you’re not sure you have all the issues straight about the universe’s history and what “Big Bang” means, fear not: I have written the History of the Universe, designed for the non-expert. Well, not all of the history, or all of the universe either, but the parts you’re going to want to know about for Monday’s announcement. Those of you who are still awake are invited to read what I’ve put together and send comments about the parts that are unclear or any aspects that look incorrect. I’ll have another post in the morning hours, and then the big announcement takes place just after noon, East Coast time.
16 Responses
It would be very cool if the discovery is not just significant but of particular significance.
The alpha decay was well known experimentally at the time, but there was no clear explanation of the mechanism that it followed (in fact, classical mechanics wrongfully predicted that alpha decay was energetically impossible).
Gamow offered the first plausible explanation, even though it was a “first approximation” explanation.
Gamow was rather remarkable in how many valid predictions he postulated over the years, including one of the first major predictive successes of the early quantum mechanics (wave mechanics) formulation, the use of the tunneling effect to deduce the behaviour of radioactive decay of atoms.
He also was instrumental in the formation of the RNA tie club with James D. Watson in the mid-1950s, and based on the well known fact at the time that all proteins were based on just 20 amino acids, Gamow postulated that it would take only 3 basic elements (nucleotides) to encode the entire set of 20 components: eventually, it turned out that he was right, as he postulated the concept of codons.
In more ways than one, Gamow followed the path opened and pointed by Schrodinger, when Schrodinger used quantum mechanics to predict many aspects of DNA and genetics starting in the late 1930s with his paper “What is life?”
Gamow always did practical jokes related to physics, one way or another.
It is well documented that for a while, he sent to his son monthly allowance checks of exactly 137.03 dollars: that number is just about the value of the inverse of the fine structure constant.
BTW, in a sense, George Gamow was a practical joker in many ways, and it is well known that Bethe was included as co-author of the paper as a joke (with his approval), so as to play with the “alpha-beta-gamma” theme.
Regarding his prediction of the CMB radiation, he sent a letter to Arno Penzias describing his prediction, and Gamow playfully dated the letter on a date before the date of the actual discovery of the CMB radiation done by Penzias and Wilson.
It is believed that it was not a mistake but on purpose, as a joke.
As I always mention, I’m not an expert in this field, but as far as I remember, among the first to predict the existence of the CMB radiation were the ABG guys, including the fact that they predicted a temperature of about 5 K for that radiation, which is not bad for an actual measurement of 2.7 K.
They based that prediction on the z (red-shift) factor value measured at the time.
The average ionization temperature for atoms (around 3,000 K) was well known at the time.
So, based on the red shift factor, the CMB radiation temperature could be predicted.
hmm… I’m too sleepy to think this through right now.
This prediction, around 2.7 K is validated by the measurements.
Your reasoning is circular. The current temperature is not predicted; it is something we measure, and is an input to the model of the universe.
When we talk about anisotropies at the time of first recombination, we really mean very tiny variations within a largely uniform early universe.
If we consider the expansion of our universe since the time of the first recombination until nowadays, the (red-shift) factor is about 1,100, which means that we can predict the current temperature of the CMB radiation to be about 2.7 K, if the predicted temperature for the first recombination is 3,000 K.
Detailed experimental information on polarization of CMB radiation is very important regarding more than one aspect, including the detailed distribution of anisotropies in the early universe that could explain the formation of the current structures in the universe (clusters, galaxies, star systems).
What is (are?) the main area(s) of info regarding the recombination period that this experiment is expected to bring?
Via Sean Carroll (http://www.preposterousuniverse.com/blog/2014/03/16/bicep2-updates/) a link to the webcast: http://www.cfa.harvard.edu/news/news_conferences.html
This thing is so hyped that I’m sure the webcast will crash.