"A major discovery", BICEP2 and B-modes

[Added note (on Monday): Well, wow, the rumours were, if anything, understated. I'm happy to go on record that, unless a mistake has been made, this is the greatest scientific discovery of the 21st century, and may remain so even once the century is over. I (and others) will write many more detailed summaries of what was observed over time, but BICEP2 have announced a discovery of primordial B-modes, which is extremely strong evidence of cosmological inflation (if it turns out to be scale invariant, inflation is as true as most accepted science). Matt Strassler has a good hastily written summary here. As does Liam McAllister at Lubos Motl's blog, here. Of course, this is just one experiment and maybe they've made a mistake, but the results look very robust at the moment.

Congratulations on being alive today readers! We just learned about how particles work at energies \(10^{13}\) times greater than even the LHC can probe, and about what was happening at a time much, much less than a nanosecond after the beginning of the Big Bang.]

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[Added note (on Sunday): It seems highly probable that these rumours are essentially true. Although the precise details of the results aren't yet public, the BICEP2 PI, John Kovac, has sent a widely distributed email with the following information: Data and scientific papers with results from the BICEP2 experiment will go public and be viewable here at 2:45pm GMT on Monday. At the same time a technical webcast will begin at this address.

It's going to be an exciting day!]

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The cosmology rumour mill exploded today. Harvard Astrophysics have issued a press release stating that, on Monday, they will announce a "major discovery".

This is the only hard-evidence of anything interesting on the way and it could be an announcement of anything that fits under the label of "astrophysics". This is important to keep in mind. However, for one reason or another (that is hard to nail down), cosmologists are suggesting that it is going to be about cosmology. The speculation is that it will be about the BICEP2 experiment, which has been measuring the polarisation in the CMB. The speculation is that BICEP2 have seen primordial "B-mode" polarisation.

If this speculation is true, this would be a result immense in its significance.

Primordial B-modes would be a smoking gun signal of primordial gravitational waves. This, alone, makes such a discovery important. Gravitational waves have not yet been observed, but are a prediction from general relativity. Therefore, such a discovery would be on the same level of significance as the discovery of the Higgs particle. We were almost certain it would be there, but it is good to finally see it.

However, the potential significance of such a result goes further because these primordial gravitational waves would need a source. The theory of cosmological inflation would/could be such a source. Inflation is a compelling theory, not without some problems, for how the universe evolved in its very earliest stages. If it occurred when the universe had a large enough temperature, it would generate primordial gravitational waves large enough to tickle the CMB enough to make these B-modes visible in the polarisation. As of yet, inflation has passed quite a few observational tests, but nothing has been seen that could be described as smoking gun evidence. A spectrum of primordial gravitational waves would very nearly be such a smoking gun. If the spectrum was scale invariant (i.e. if the gravitational waves have the same amplitude on all distance scales) that would be a smoking gun for inflation and accolades, Nobel Prizes, etc, etc, would flow accordingly.

All of this is just speculation, but some of it does seem to be coming from reputable sources. And some of my colleagues have been talking about tip-offs from people who wish to remain anonymous, so I figured I'd collect all the speculation I know of here in a post (let me know if I've missed anything):

• Richard Easther, on the rumour and its implications
• Bruce Bassett, on the probability that the rumours are true
• The Guardian (the first major news source to pick up on this) with comments from various prominent cosmologists
• Jester/Resonaances on the context (i.e. earlier constraints on primordial B modes)
• Lubos Motl, amongst other things, explains what B mode polarisation actually is
• Philip Gibbs, at viXra log
• Peter Coles, amongst other things, on why gravitational waves mean there should be B-modes in the CMB polarisation
• Sesh Nadathur on why, amongst other things, the rumoured measurement would appear to be in tension with results from Planck and WMAP

• Sean Carroll has written a very thorough overview of the implications for cosmology (if the rumours are true).

The PI of BICEP2, John Kovac, gave a talk at the annual COSMO conference last year that had some pretty ambitious claims for how sensitive BICEP2 and similar experiments were going to be, so... well... we'll know on Monday. It should also be noted that, although the existence of these gravitational waves is a prediction of inflation, their amplitude is a free parameter and an amplitude this big is potentially a little surprising (for me, lower temperature inflation models just seem more compelling, others might disagree).

Twitter: @just_shaun

[Edit: The video of John Kovac's talk can be found here]

Highlights from Beijing: COSMO 2012

The obligatory conference photo. The photographer spoke to us in Mandarin. I think what he was trying to say was "more intensity".

Just over a week ago I was at the annual COSMO conference. This year's host was Beijing. I had originally intended to live blog this event, but the Great Wall of China (alternative link) managed to prevent that entirely.

What follows are some reflections on the scientific bits and pieces people presented at the conference that I happened to find interesting. It might be a bit technical, but please ask questions if I use jargon you don't understand. Also, if you're an expert and I write something you want to comment on, please do (especially if something I write is misleading or just plain wrong).

The topics I've chosen below just happen to be what I found memorable. I made no attempt to choose these topics by any sort of theme. I apologise if I've missed anything particularly interesting. Perhaps if you were there and think I missed out something interesting you can either mention it in the comments or write a guest post for us.

Neutrinos and precision cosmology

One of the first images captured by the Dark Energy Survey. The more interesting images it will take will be of very distant galaxies and won't look anywhere near as nice. This one is just for people to put in their blogs.

Jan Hamann gave a talk on the future constraints that cosmology will provide for neutrino physics. I was pleasantly surprised by the power of large scale structure probes, such as Euclid.

We know from particle physics experiments that the difference between the masses of two of the neutrinos is more than 0.06 electron volts. This means that the heaviest neutrino must be heavier than 0.06 electron volts.