The effects of high altitude

Writing from Christchurch on my way back north, I've come to realize that I'm a complete wuss about high altitude.  At 9,300 ft, but an effective 11,000 ft when you correct for the lower pressure at the poles, it's higher than I've ever been before, and I felt the effects most of the time there.

They tell you to take it easy when you first arrive, but there were measurements that people up north were particularly anxious about, so I got involved in my first 24 hours anyway- that was probably a mistake.  A couple days in, I passed out at the telescope with only vague memory of trying to move myself closer to the floor as the dizziness set in.  This is when I think I jammed my knee, which spent the next couple weeks swelling up.  The station doctor diagnosed this as bursitis, when the lubricative bursa sac becomes inflamed, and in my case, probably infected.  The thing finally burst open while I was outside working on the telescope about a week before I left.  At high altitudes, the body takes a lot longer to heal, and I suspect this is why this whole thing took so long to work itself out.  On the plus side, with a quarter-sized hole in my knee and the possibility of infection, the doctors didn't even hesitate to let me take daily showers!

Over the course of the month I was there, I lost perspective of how inhospitable the interior of Antarctica is...  that is, until I got back to McMurdo.  For the first time in weeks, I could breathe easily and that low 30s F temperature felt tropical by comparison.  I spent that evening walking around in T-shirt and sandals.

Finally, the high desert is very dry and is responsible for the constant nose-bleeds, "blood boogers," and split skin on the hands (aka, "the splits").  I think this also may be why we can't smell anything up there   That lets us get away with showing so seldom, but it also makes for quite the olfactory overload when you come back down.  I spent my morning in Christchurch before my flight home walking through their botanical gardens in Hangley Park- the smells of the grass, trees, and especially the roses were overwhelming.

Brook through the park

Rose Garden

Trellised pairs in the fruit and vegetable garden

There's one plus about all of this for a coffee geek like me.  Water boils at 193F there (I measured 195), which is the perfect temperature to brew coffee.  If it's any warmer, it will burn the coffee, so at sea level you must wait to let it cool t bit before pouring; at pole, you bring it to a boil and just pour.  After over a month since the beans were roasted, my coffee still tasted great.  Here's a video of it blooming, a full month after roasting:

Normally, that's CO2 being released, although in this case it may just be water vapor.  And it smelled great.

Polarized Microwaves from the begining of the Universe

I work in the Martin A. Pomerantz Observatory, aka MAPO.  Here's a short video tour I shot of the place:

I neglect to mention that the giant wooden cones around the telescopes are ground shields which prevent our cameras from seeing stray light bouncing off the snow.  When I'm up in the mount, I also mistakenly point at a tray holding pulse-tube lines while describing it as an elevation gear.  At that time, I was paying more attention to not getting my hand caught in the drive than what I was filming.

This observatory has housed two very successful CMB polarization experiments over the past decade, and several of our senior group members have worked on both.  This rest of this post describes what they saw and I'll try to make another post about how our experiment will advance that further (things get nerdy from here on out!).

I previously described how the Big Bang "echoed" in the early hot universe, and how the hot and cold regions of those sound waves left behind hot and cold spots in the microwave sky.  Those spots are also polarized.

You can think of light as similar to shaking waves on a rope- shaking the rope up-down is distinct from shaking left-right- and the same is true for light waves.  We call this property polarization.  But even though our eyes can see different colors or brightness, we cannot see polarization on our own.  Often, both polarizations of light are present, but more of one type than the other.  We can build filters that screen away one of the two polarizations, and this video uses such a filter to show that the afternoon sky is polarized:

That polarizing filter looks dark in a specific position because it is filtering the brighter of the polarizations, passing only the dimmer one.  The sky itself looks polarized because the afternoon sun illuminates air in our atmosphere from only one side, like this:

Light scatters off atoms in the sky, adapted from Wayne Hu

In this cartoon, the light from the sun has both polarizations shown in the light blue crossed lines; that light grabs and shakes electrons in the gas in our atmosphere.  We cannot "see" electron motion towards and away from us, only transverse.  So we see mostly vertical polarization scattered at us.

Those sound waves in the early universe created a similar situation: electrons in the cold low pressure planes (red stripes) will be hit by weaker light from above and below and brighter light from the warmer high pressure planes (blue stripes) coming in from the left and right.  So the scattered light is brighter in the vertical polarization.  The opposite argument holds for electrons in the hotter blue strips, scattering brighter light in the horizontal polarization.

Early universe sound wave scattering polarized radiation, adapted from Wayne Hu

Many different sound-waves will produce a series of polarized spots on the sky.  Here's a map of polarization difference from our sister experiment BICEP-2:

Polarized CMB spots

All of our cameras contain hardware that is similar to the polarizing grid shown in the youtube video above so we can measure the power in both polarizations.

In 2002, the DASI experiment (in MAPO) demonstrated that the CMB is indeed polarized as everyone expected.  In 2006-8, the next experiment in MAPO- QUAD- took a detailed enough map to show that this polarization has similar structure as the temperature maps I showed in this previous post.

from the QUAD experiment

Similar to before, this plot shows how much brighter one polarization is than the other for spots of specific sizes, and it plots difference against spot size.  You can see  a similar peaked structure as before, which is not a surprise since these come the same early-universe sound-waves that produce the temperature spots.  For technical reasons, this sort of measurement can measure many of the features of our universe better (i.e. smaller uncertainty) than the temperature maps.  But no one is good enough at these measurements yet to beat the temperature measurements.

Marooned in "Mac-town"

Smoke form Mt Erebus (photo from USGS)

Two people from our team left on Friday, to be replaced with two new arrivals.  It's a miracle they were able to leave at all since the landing strip at McMurdo is apparently a pile of slush right now. 

The temperature there yesterday hit 40F (for comparison, the temperature at pole is a balmy -13F).  This is a problem because, as I previously described, the runway is on the Ross Ice shelf in the middle of the sea.  The ice is still plenty thick (several hundred of meters), so planes can still land on their skis.  But it's big a problem for taking off because the slushy snow provides too much friction to get up to speed.  This warm weather has been exacerbated by ash from Mt Erebus, a nearby active volcano, that has blown over the ice.  That ash absorbs sunlight more efficiently than the bare reflective snow, heating the ice even more rapidly.

Map showing the problem: the airfield is right next to a Volcano

The polar-program typically flies one flight per day each way between Christchurch and McMurdo, and each flight holds 10-15 people beyond the crew.  There are apparently 135 scientists waiting in McMurdo right now to fly north.  I miss Abby and Liam a lot, and if I could, I would take the next flight out of here I would (despite my work and others' work here being really cool).  But I would simply get stuck in the mess in McMurdo anyway.  So here's hoping the weather and ash situation improves quickly before I leave in two weeks.

To add insult to injury, one of the freight ships is docked there now and their policy is to stop selling alcohol during that time because the sailors are too rowdy!  (This is why we can't have nice things!)  So those 135 scientists who are done with their work are sitting around in one of the world's smallest towns with nothing to do and nothing to drink.

As for that flight that came in yesterday, the only reason they flew at all was to bring Senatorial aides in for a 3-hour day trip (the actual Senators had to stay in DC as penance for not playing nice with each other).  But all these problems delayed their flight such that they arrived during dinner.  So the aids only had time to eat and take hero pictures at the south-pole, leaving no time to visit our experiments and hear what cool things we're doing with their tax-dollars.  What a mess…

Viewing exploding stars through the polar ice cap

As we waited for cameras to cool in the lab on a slow day, I took an excursion to IceCube and the Askarian Radio Array (ARA), where they are using water jets to drill deep holes into the ice.  Here's a video they made while checking if one is wide enough:

The scientists on these two projects drop sensors into holes like that to search for astrophysical neutrinos, using the Antarctic Ice shelf as a giant target.

Neutrinos are basic particles that are nearly massless and only interact with other particles by a "weak" nuclear force.  As a consequence, they can sail through dusty regions of our galaxy and universe and, in principle, let us see things that we never could with light that would get scattered away.  This is particularly true with Supernovae- stars that exhaust their fuel, collapse under their own weight, and then explode.  The electrons, protons, and photons in collapsing stars get so hot that they effectively bind together and cannot escape; only the neutrinos can get out, and as a result carry away 99% of the star's radiant energy.  This makes neutrinos an alluring way to study stellar collapse.

Picture of the 1987A supernova (with photons, not neutrinos), from Hubble Space Telescope

But just as neutrinos can sneak through hot and dusty regions outside Earth, they also sneak through most matter on Earth, which makes them very difficult to see.  They occasionally collide with atomic nuclei in something dense like water or ice.  These collisions produce a shower of charged particles that can emit light, and light is something that we're actually good at measuring.  If only we had a large chunk of ice…

Oh wait!  I've spent the past two weeks living on one that holds 60% of the Earth's fresh-water!  The idea behind the Ice-Cube Observatory is to drop strings of the sensors (photo-multiplier tubes) in the picture below into holes that are 2km deep and look for evidence of neutrinos scattering off a cubic kilometer section of ice.  In principle, one can even use the multiple detectors to infer where the neutrino came from.  They haven't seen anything yet, although the project only finished construction a year ago.

Detector for Ice-Cube (on display in the station)

Since then, the team has moved onto constructing the next project- the Askaryan Radio Array (ARA).  When even hotter neutrinos ("ultra-high-energy neutrinos") scatter off atomic nuclei in the ice and produce charged particles, those particles should also produce faint radio pulses (known as the Askaryan Effect).  So the team is also dropping an array of antennas down similar holes to listen for these events.

An antenna for the Askaryan Radio Array, being dropped into a hole.

Ultra-high energy neutrinos are interesting for different reasons than the slower ones for Ice Cube.  Black holes and supernovae blasts can accelerate protons to super-high speeds- far faster than we can in the lab- and fling them off into extragalactic space.  We say that these are high energy because their speed is so high and for historical reasons call them "cosmic rays."  The catch is that we can only detect them up to a threshold energy level because hotter cosmic rays scatter off the CMB (remember, the radio waves my telescope looks at) and get destroyed.  But as they are destroyed, they can produce ultra-high energy neutrinos and the ARA is attempting to use those neutrinos to understand particle collisions at energies far higher than we can make at accelerators. It's an attempt to discover new physics that we can't produce in a lab.

There's reason for optimism for the ARA folks- a balloon borne version called ANITA-2, which flew from McMurdo a few years back, saw evidence for one ultra-high-energy neutrino event.  With time on their side, ARA may have the chance to see more than one.

Hazing the "boss"

Since my arrival, I've been the most senior person on my project in the field, which has introduced me to the "wonders" of middle management; it's been a character building experience.  My most significant yet tiring actions have been responding to detailed and demanding emails from people up north on behalf of other team members down here so they can actually get stuff done.

I've mostly lead by anarchy, letting all the junior people just tell me what needs to happen.  It's worked out pretty well since we have some pretty talented and hard-working graduate students. 

But any success we've had hasn't stopped them from teasing me at times.  This included making me attach the most difficult screws in one of our cameras- one has to blindly reach two feet into a space with about two inches of vertical clearance and screw together two parts.  Oh, and if you drop the screws, it can take several hours to fish them back out (which you must do).  What would have taken a more experienced grad student 5 minutes took me a better part of an hour.

They also insisted I do "sweet jumps"- body surfing down the snow drifts.  There's a significant drop just outside the observatory where they video taped me.  This drop exists because the observatory is sinking into the ice-cap and over the past 20 years has fallen the height of the drop (15 feet or so).  Apparently I look like a nervous seal in this video; judge yourself:

The sauna is broken right now, which is probably a good thing since they've been talking about making me run out of there and out to the pole...

Happy New Years

Fashionably late to the New Years Eve party

Happy New years from the South Pole.  We use New Zealand time here, which makes us among the first in the world to bring in the new years, although I suppose you could always just change where you're standing relative to the Pole and celebrate at any hour you choose!  On New Years Eve, we put in a 10 hour work day at the observatory, closing up a camera until 11:00PM, which means we felt we really earned our drinks of the evening.  Above is a shot of some of us on the return trip, sipping some "roadies."

The ice cap is constantly shifting and carries the base away from the South Pole.  Every few decades they build a new station (environmental wear and tear is pretty tough down here), which coincidentally helps them keep the base roughly near the pole.  Here's a couple pictures of the previous base in use from 1975-2005 (there was another base even before that built in the 1950s, currently buried in the ice):

Old dome base

Inside the old dome base

Every New Years Day, at noon, they have a ceremony where they move the official marker.  In this video, they have all of us present passing the US flag in an arc from the old location to the new (about 10 yards).

The winter-staff includes a station machinist, whose responsibilities include machining a new Pole marker.  This is a photo as it was unveiled: