Notes from John Carlstrom

Corresponding with John Carlstrom

Special to this year's edition of the the travelogue! John Carlstrom is the director of CARA and a famous astronomer. He is in the middle of building a new telescope, DASI, which just went down to the Pole in Dec 1999. John spent a lot of time at the Pole this austral summer, and while he was there in January, he answered these questions from Irene Keyes' classes at Nassau/Spackenkill Elementary School in John's hometown, Poughkeepsie, NY.

Greetings from the South Pole! It was a pleasure to receive your email and information about your school and city. I know the area well as I grew up in LaGrange and attended Overlook Elementary School, Lagrange Junior High School, and Arlington High School. I even graduated from Vassar College.

Now I am a professor at the University of Chicago and run the Center for Astrophysical Research in Antarctica (CARA). We have three telescopes that we operate at the South Pole. I am at the South Pole right now. It is currently -30 F degrees outside (a warm day!), but it will get to -100 F in the winter. Winter here is summertime for you. It is so cold here in the winter that planes can not land. Since there is no other way in or out, everyone who stays here after the last flight must remain here until the end of October when it warms up again. Now there are 220 people here and about 50 will stay through the winter.

There is only one day a year here. It is light for six months and dark for the other six. Summer is light and winter dark.

I am looking forward to heading home in about a week's time. It takes 5 long flights to get home to Chicago.

The newest project is DASI (the degree angular scale interferometer). It is almost ready to go and will be before most of us leave on the last flight out Feb 15 -- we leave behind 5 winter-overs who will stay through the Austral night until at least the end of October. There is no direct access between Feb 15 and the end of October. It is too cold for the planes.

How much does DASI weigh?
DASI weighs about 38,000 lbs.

How big is DASI?
The base of DASI is 9' x 9' and it is about 12' high.

DASI sits on top of a 30' tower which is supported on large platforms buried in the ice.

The weight and size of DASI was to big to fly it to the South Pole in one piece. We first assembled it in Chicago and then took it apart in three main mechancial assemblies on big steel pallets. The electronics and receivers were shipped separately. All in all we shipped down about 75,000 lbs.

Interestingly, there are no overland routes to the South Pole, all cargo must go by ski equiped planes. The biggest such plane is a LC130. It can take up to 25,000 lbs and all containers must fit into a 8'x8'x16' max cargo area.

When the LC130 is not full of people they put in cot like seats for passengers. It is how we get here as well. It takes about 4 hours from the McMurdo station on the Antarctic coast.

How long is DASI going to stay at the South Pole?
It will observe from the South Pole for about 5 years, maybe longer.

How much did DASI cost?
We have been working on DASI for 4 years. The total cost so far has been about 4 million dollars.

How does DASI work?
DASI works a little bit like your eyes. You can think of each of the horns sticking out from DASI as eyes. DASI has thirteen eyes. And just like you have two eyes, but only see one picture in your mind, DASI also only sees one picture in its mind (which is a special computer). Can you imagine having 13 eyes like DASI?

DASI's eyes don't see the same light as your eyes do. DASI sees light that is invisible to me and you. And, the light our eyes sees is invisible to DASI. If your eyes could see the same light as DASI, then the whole sky would look very bright to you, even at night.

How come we count 16 holes when we look at a picture of DASI and you say there are 13 eyes?
We put 3 extra holes in case we want to move the horns (eyes) to different positions. You might notice one position has a black tube sticking out of it - it is different than all the others. This is a fancy camera so we can look at the sky and take pictures. This camera looks at the same light that our eyes see.

When looking at the "petals" around the eyes of DASI, the students want to know if they close up to protect the eyes when there is a snow storm?
Actually the "petals" are covered with aluminum and are used to shield the main part of the telescope -- the horns in the middle of the "eye"-- from local radiation, such as man-made radiation, phones, radios, etcs. We call the petals "ground shields" because even the ground and the building emits unwanted radiation. You can think of them as mirrors. Even if the eye looks toward the horizon it will see only the sky reflected off the metal petals.

The petals do not fold up. Interestingly, there is very little snow fall at the south pole. Maybe a few inches a year. It is extremely dry here, probably the dryest desert on Earth. However, it is also always very cold! The snow never melts and therefore the ice slowly gets thicker and thicker. It is now about 2 miles thick! Today the temperature outside is -33F. The record cold here is -118F!

How old is the universe and how old do you think your research could or might prove it to be?
We know the universe is between 10 and 15 billion years old. Our sun is about 5 billion years old. The first human (homo sapien) was about a 100 million years ago. We humans are late comers!

The light DASI will detect has been travelling to us for almost the entire age of the universe. It was emitted when the universe was only 1/50,000 of its present age. With this data DASI will be able to get a better determination for the age of the universe, but more importantly (at least to me), DASI will be able to test theories for the origin of the universe, tell us the future of the universe (will it keep expanding, will it collapse back on itself), and really fascinating, what makes up the universe.

This last point is amazing. We are learning that the stuff we are made out of, the stuff that the stars are made out of, what we like to call normal matter such as atoms, molecules and stuff, is only a small fraction of the matter in the universe. Say about 10 - 15%. Scientists do not know what the other 85% is, but we can detect its presence through its gravitational effects. For example, if you measure how fast something is rotating, then you know it must have enough gravitational force to hold it from flying apart -- from this force you can calculate the mass. Astronomers use rotating galaxies to do these measurements. DASI will tell us more about this. What we are also learning is that there is another component of energy in the universe which is even more important. Einstein showed us Energy = Mass times the speed of light squared. DASI will measure the total energy in the universe. So far, it appears that even after accounting for the 85% of the mass which is in some kind of unknown form, there is another component of energy which is about twice as important. DASI will give us definitive answers.

There is a lot of new physics to be discovered!

What I am most interested is in using DASI to test models for the origin of the universe. The theory that DASI will test is called the inflationary theory. It is an explanation of the start of the big bang. If it is the correct theory, then it makes sense to think of our universe as only one of an infinite number of universes!

It boggles my mind.

How does the radiation get into space?
When we say radiation we mean light - light that is invisible to us but not to DASI. Light travels through space without any problems. You probably are comfortable thinking of light coming from stars through space and detected in your eyes. That is, you see stars. Well light from very very far away that came from very hot gas is what DASI detects. You can see similar light too, for example when you look at flames from a fire. The light DASI sees is coming from such a long distance away that it has taken about 15,000,000,000 years to reach DASI! It has been travelling almost since the beginning of the universe. That means that DASI is like a time machine, it allows us to "see" the very early universe. This is hard to imagine, I know, but it is also what makes DASI so interesting to me.

Why did you choose Antarctica for DASI? Why not the North Pole or the Sahara Desert?
We choose the South Pole because the atmosphere above the South Pole contains very very little water vapor, much less than the Sahara Desert. Also the Sun emits a lot of light even at microwave wavelengths that contaminates the cosmic microwave background radiation that DASI will measure. By contaminate, I mean it add confusing signals. At the South Pole the sun never gets higher than 23 degress off the horizon in the summer and it is dark six months of the year (only one day and one night a year at the south pole). Radiation from warm objects can also lead to contamination of the cosmic microwave radiation, so the extra cold temperatures here help too. Finally, the less atmosphere DASI has to look throught the better as the atmosphere adds noise. The South Pole is quite high at ~10,000 feet above sea level.

The North Pole is an interesting suggestion, but it has some problems. First there is no land there. The ice is not that thick and it is always moving -- DASI would likely end up in the sea if placed at the North Pole. Also it is not very high - it is at sea level.

Are there any penguins, whales, or walruses at the South Pole?
No, there are no living animals besides us people at the South Pole. It is too cold and there is no food for them. The South Pole is near the center of the Antarctic continent. However, at the edge of the continent where the land meets the sea, there are a lot of living things. And, yes, there are lots of penquins and seals that go in the water. There are also lots of sea birds too. We see them when we stop near the shore while traveling to and from the South Pole.

What are the warmest day temperatures in the summmer at the South Pole?
The warmest day temperature ever is +7.5F. The warmest this year has been -20F. It is now getting much colder and has already been -40F this summer. The coldest day on record -118F.

hat happens if there is an emergency (fire, power failure,etc.) in the dome, especially while wintering over?
This is a big concern! All of the winterovers are trained in fire fighting and they have lots of practice drills. So, hopefully they will put the fire out before it gets too bad. Just in case, they have another backup base (warm tents that we use in the summer -- in fact, I sleep in one of these tents -- called Jamesways. They are fine, although anything left on the floor freezes solid.) complete with emergency rations of food and other supplies.

There is a surgeon winterover for medical emergencies.

For power, there are three generators. At all times, one is running and supplying the entire site, one is running as instant emergency backup, and one being serviced. Every few weeks they change them around so they are all serviced regularly. There is enough extra fuel on site to last an extra year.

Are there any TV's in the dome?
There seem to be TV's everywhere - well at least a dozen on the site. We don't get any channels, however, but there are lots of videos and VCRs. A video of the super bowl was flown down here for example.

In the South Pole do people speak different languages?
The station at the South Pole is run by the United States and so English is the official langauge. There are people from all over the world, but most people are from the United States and almost everyone speaks English very well. There are about 200 people here in the Antarctic summer (your wintertime) and about 50 people who stay here through the long cold, dark winter (your summertime).

Are you having fun?
YES! Doing science experiments is really fun. And it is very nice to be able to answer questions about the universe. It is also very exciting to be at the South Pole. Everyone down here is very excited and loves their work. It is really fun. I miss my family, though, and am anxious to get back home. The South Pole is a long way from anyone's home.

How thick are your red coats?
The red coats are about 1 1/2 inches thick. The coats by themselves are not enough to keep us warm when we go outside. We wear very thick long underwear, thick insulated pants, thick wool socks, special super-warm boots (we call them bunny boots because they are so big and white. I can stand outside for hours and my feet never get cold. They remind me of astronaut space suit boots), a heavy sweater, a hat with face mask, big goggles, and then finally the red jackets with the big hoods.

The goggles help keep our faces warm and also protect our eyes from the very bright sunlight. The sun reflects off the snow too. If you don't protect your eyes, the brightness will hurt them. Even with the goggles on outside, I sometimes have a hard time seeing for a few minutes when I come inside and take them off. It is just like the temporary difficulties you can have seeing after someone takes your picture with a bright flash. You know how you keep seeing the bright spot?

How deep is the snow?
The snow has been accumulating for millions of years. It is now 2 miles deep! It is packed very hard, so we only sink in a couple inches when we walk on it. People have drilled deep holes into the snow and find that it is very pure clear ice when you get about 100 to 200 feet deep. It turns to solid ice because all the weight from the snow above it squeezes the air out.

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