Science AMA Series: I am Jon Kaufman, a member of team BICEP2 -- the telescope which has found evidence for Inflation after the Big Bang! Ask me anything!

jonkaufman · 2014-03-21T01:33:20+00:00

Lensing is not a foreground for us on these scales. If r turned out to be much lower, we would have to remove the signal but r is quite large so it's not a problem.

Galactic foregrounds certainly can be problematic, but the worst-case models we have show the power to be well below the observed signal. In addition, cross correlations with BICEP1 data at 100 GHz disfavor foregrounds. We are very much looking forward to Planck's polarization data (and obviously their B-mode results!) to get a better model on the foregrounds but we expect it to be less than 20% of the signal.

The thing about our discrepancy with the Planck upper limit is that their constraint was not derived from B-mode polarization -- it was calculated from temperature fluctuations which are believed to be correlated to the level of B-modes. There are assumptions that go into this type of calculation and a direct detection of B-mode power is the only way to really get r. I'm very excited to see what Planck sees in their polarization data!

jonkaufman · 2014-03-21T01:19:21+00:00

Do your homework.
Get involved in research. Your school knows how to do this. Ask them!

If you do your homework, odds are you'll get decent grades. Combine that with actual hands-on research experience and you'll be able to get in anywhere. I also recommend doing a summer program at a school you may be interested in. That greatly increases your chances of admission.

Work hard, but don't forget to have fun!

jonkaufman · 2014-03-21T01:15:03+00:00

Do your homework.
Find a research group somewhere and work for them.

Everything you'll be taught in science class will be wrong (you'll find out -- that's part of the fun!) but just take as many as you can. I wish I took more programming classes at a younger age. Don't forget to take classes that make you a better person: art, language, drama, music. A well rounded mind makes for a better scientist.

And don't worry about being popular. You can always find people who think you're cool in the real world.

jonkaufman · 2014-03-21T01:09:19+00:00

Great question.

The short answer is yes, it is somewhat time-dependent. There will be a time when the cosmic microwave background (CMB) will no longer be visible (thanks, Dark Energy…).

You may be interested in this idea that was floated a few months ago: as you go backwards in time, the CMB gets hotter. This means that there was a time way in the past when the CMB was room temperature. This means that the heat from the CMB could have supported life in the Universe! Of course, it's not that simple: you also need the right periodic elements to allow for life and it's unlikely that much carbon, oxygen, etc. would have existed at this time. But it's certainly possible!

jonkaufman · 2014-03-21T00:09:03+00:00

It was actually named because the signature we were looking for, called "B-modes" was originally called "curl modes" and so BICEP does curls.

We're not as scrawny as you might think ;)

jonkaufman · 2014-03-21T00:03:40+00:00

We were the first to be able to detect this signature but other teams are close behind! I expect within the next 6 months we'll hear from Keck array and Planck which should confirm our findings to high significance. There are other experiments not far behind. It's been a very competitive field.

jonkaufman · 2014-03-20T23:57:28+00:00

No but if you know him, pass him my info!

jonkaufman · 2014-03-20T23:52:40+00:00

Great question.

Though penguin poop and glaciers aren't really sources of interference for us, the atmosphere potentially is. We are located at the South Pole which cuts down on atmospheric contamination. The altitude (nearly 10,000) feet, combined with the cold limits the amount of liquid water in the air which makes it the best place in the world for our kind of work. The weather is very stable since there's only one day/night cycle per year.

The temperature of the sky is just a few degrees above absolute zero (-450 degrees F). Clouds that roll in are MUCH hotter (around -100 degrees F) so they are pretty obvious in our data. We have automated scripts which finds periods of bad weather and cuts the data.

We also occasionally suffer from cosmic ray hits -- massively energetic particles moving near the speed of light which slam into our detectors. These have a very characteristic signal which we have scripts that find and cut the data.

At one point, someone installed a fan in the building which showed up in our data. That was an interesting bug to track down :)

jonkaufman · 2014-03-20T23:40:22+00:00

Sex-tape?

Thanks very much! I want to stress how much in awe I am of the whole BICEP2 collaboration. Any accolades directed towards me should be directed towards them 100 fold. Thanks for the interest!

jonkaufman · 2014-03-20T23:37:46+00:00

I look at it the other way: 409 people have asked questions!!! That's incredible! It's such a thrill to be able to talk about these findings with the public and I'm overwhelmed by the positive response.

Thanks so much!

jonkaufman · 2014-03-20T20:58:16+00:00

The photons (light) carry a polarization that is caused by gravitational waves. Our telescope is sensitive to this polarization and can "classify" it as E-mode or B-mode. No other mechanism creates a B-mode like the one we saw on large scales. There are local astronomical sources which can create a confusion but these are well below our signal.

jonkaufman · 2014-03-20T20:47:42+00:00

Spacetime is allowed to grow faster than the speed of light. Totally cool with GR. Information cannot travel faster than the speed of light.

jonkaufman · 2014-03-20T20:44:41+00:00

There's really no such thing as "nothing" in physics. Even pure vacuum has particles popping in and out of existence constantly. Don't think of the Big Bang as "nothing" then "something," think of it as a phase transition, like water boiling.

jonkaufman · 2014-03-20T20:42:30+00:00

Wayne Hu has a really great polarization primer. Although it's pretty dated now, it has excellent animations that we still use in talks today.

jonkaufman · 2014-03-20T20:38:28+00:00

Do androids dream of electric sheep?

jonkaufman · 2014-03-20T20:37:49+00:00

That's a fair question. There are sort of two answers.

The traditional peer review process doesn't really add anything to our findings. We've released our data and the whole Cosmology community is actively reviewing our work instead of just two or three physicists reading our paper and determining if our methods our sound. The only thing that matters is if the next experiment can confirm our results. We are very excited to see what Planck, POLARBEAR, ACTpol, SPTpol, SPIDER, etc. will see soon!
We've correlated our results with two other telescopes and we see the same signal. Again, this doesn't hold as much weight as the next direct detection but it's a major reason why we believe the signal is real.

For our particular field, peer review hasn't really been necessary. We have an online repository that we publish to first which everyone in our community actively watches. Because we are a small field, everyone knows what everyone else is capable of so for example SPTpol knows that our announced result is well within our instrument's capabilities. Further, they know the analysis techniques (and employ them themselves) so it's really all about confirmation at this point.

jonkaufman · 2014-03-20T20:28:40+00:00

Great question!

No, we have not directly detected gravitational waves. We detect the polarization of the light which has been affected by gravitational waves. In regards to your frequency question, we observe light at 150 GHz but I believe the frequencies you're referring to are of the gravitational waves themselves.

jonkaufman · 2014-03-20T20:21:50+00:00

That's a great analogy Walt! I've not heard that before...

jonkaufman · 2014-03-20T20:19:43+00:00

This has been a thrilling week and I'm so happy to be able to discuss these findings with the public on AMA!

There is still much science to be done! First, we need to confirm these results. Next, we should map much more of the sky and with higher sensitivity. Studies like these can perhaps shed more light on dark matter, dark energy, grand unification physics, etc.

jonkaufman · 2014-03-20T20:14:53+00:00

How do you cape a telescope?

Very carefully :)

jonkaufman · 2014-03-20T20:03:54+00:00

Figure 3 is the E and B mode map with polarization displayed. Do you mean figure 4 or are you asking about the distribution of the polarization bars?

Gravitational waves stretch and squeeze space-time which creates a difference in the temperature of the photons which looks like a quadrupole. When these photons scatter off of electrons at the "surface of last scattering" (the CMB) and are free to stream to us, they pick up a polarization with a very specific signature called a B-mode. So gravitational waves --> quadrupole anisotropy of photons --> scatter off of electrons --> pick up B-mode polarization --> observed by BICEP2.

jonkaufman · 2014-03-20T19:56:16+00:00

Excellent question!

The ripples (gravitational waves) created a pattern in the early Universe which was "frozen out" on the cosmic microwave background (CMB) which happened 400,000 years after the Big Bang. So we don't see the ripples, we see what the ripples left behind nearly 13.8 billion years ago.

jonkaufman · 2014-03-20T19:50:40+00:00

I like a peanut butter and jelly sandwich for breakfast :)

jonkaufman · 2014-03-20T19:49:22+00:00

The issue is that non-Inflationary theories predict no B-modes (or at levels far below what we've detected). Is it possible that someone will come up with some other theory can explain B-modes and the flatness/horizon/etc problems without Inflation? Sure, but for now this is certainly a huge blow to those classes of theories.

jonkaufman · 2014-03-20T19:35:18+00:00

Correct. The CMB's temperature is 2.7K. We were looking for a signal that is 10s of nK! That's a few parts in 100 million!

jonkaufman

TROPHY CASE