Ravens, like some great apes, plan ahead.
Paleontologists dig for fossils in order to study the past. Astronomers do the same thing—except the fossils they work with are made of light. With powerful telescopes that can see deep into space, astronomers can actually catch glimpses of radiation left over from cosmic events—like, say, the explosion that created the universe. In this Science Update, you’ll hear about one research team’s effort to measure remnants of light from the Big Bang.
A telescope that's high and dry. I'm Bob Hirshon and this is Science Update.
While we're in the throes of winter, it's summer at the South Pole—meaning temperatures hit the balmy high of 22 degrees below zero. Nevertheless, it's warm enough for scientists from the Center for Astrophysical Research in Antarctica to tend to one of their newest telescopes. It's called DASI. And researchers like Erik Leitch of the University of Chicago are using it to measure the Cosmic Microwave Background.
And this is actually light that's left over from the creation of the universe, and this was radiation that was released when the universe was only about 300,000 years old. And it's been traveling throughout the universe for the last roughly 14 billion years, um pretty much unchanged from that early time when it was first released.
DASI actually consists of 13 individual telescopes that work together to construct an image of the sky. Leitch says the South Pole's an ideal place for DASI because there's not much water vapor to interfere with measurements.
It's actually one of the driest deserts on the planet. It's also quite high, because you're on top of 2 kilometers of ice, the base level of the South Pole is above 9,000 feet.
So, DASI is perfectly situated to give researchers a snapshot of a baby universe—when it was just 300,000 years old. For the American Association for the Advancement of Science, I'm Bob Hirshon.
Making Sense of the Research
You've probably heard that the light from stars takes years to reach the Earth, because the stars are so far away. So when you look up at the sky, you're really seeing the stars that were there several years ago—stars that might actually be burned out today.
If you can see that far back in time with your naked eye, imagine what you can do with a powerful and sensitive telescope like DASI. The light that DASI measures, known as the Cosmic Microwave Background (CMB), is an invisible, low-frequency light that's been traveling through the universe for almost as long as the universe has existed: about 14 billion years. And it hasn't changed much in the journey. So looking at the CMB is like looking at the universe just 300,000 years after it was born. (To put that in perspective, that's like finding a photo of your 70-year-old grandmother that was taken when she was just twelve hours old.) That's why the CMB is sometimes called "fossil light."
Because this kind of light is very faint, astronomers need to minimize anything that might interfere with it. As it turns out, water vapor in the Earth's atmosphere is one of the biggest problems. That's because water vapor actually emits traces of low-frequency light that's very similar to the CMB. As a result, if your telescope is in a humid place, you can't tell if the light you're seeing is from the ancient universe or from right here on Earth.
At the South Pole, the humidity is as low as it gets, since cold air can't hold very much moisture. And as Leitch explains, it's also high above sea level, which means you're looking through as little of the atmosphere as possible. That's why the South Pole is home to several powerful telescopes, including the 13 that make up DASI. By studying patterns in the Cosmic Microwave Background, the scientists who use it hope to learn more about how old the universe is, how fast it's expanding, how much energy and matter is in it, and even how it's shaped.
Now try and answer these questions:
- What is the Cosmic Microwave Background?
- Why can it tell us about the beginnings of the universe?
- What are the advantages of building telescopes at the South Pole?
- How does the incredible size of the universe make it difficult to study? Can astronomers ever really see the universe as it is today? How?
- Even when the Cosmic Microwave Background was released, the universe was 300,000 years old. Why do you think it's difficult to see back any further? Do you think scientists could ever see back to the very first moments in the life of the universe?
- Whenever humans use light waves to transmit information here on Earth—in television and radio broadcasts, for example—some of it leaks into space and travels across the universe. Recently, the earliest television signals from the 1950's passed the nearest star. What do you think would happen if other civilizations on other planets picked these up?
Visit the Center for Astrophysical Research in Antarctica's (CARA) website. Be sure to check out the South Pole Adventure Web Page where you will find an Antarctic webcam and other interesting resources. You can even submit your own idea for an experiment to be performed at the South Pole. If your experiment is chosen, a member of CARA will mentor you as you prepare your experimental design. You also can learn more about DASI and view pictures of it as it was being built.
In addition, you can read a brief introduction to cosmic background radiation or a more detailed explanation called A Beginner's Guide to the Cosmic Microwave Background. If that makes you want to learn more about the Big Bang and the history of the universe, check out the Mysteries of Deep Space Interactive Timeline.
To further explore the continent of Antarctica, visit Origins: Antarctica or The Arctic and Antarctic Circles at National Geographic's Xpeditions.