Third time was a charm when 2013 Karl G. Jansky Lectureship winner Dr. Charles Bennett gave his lecture Friday at the National Radio Astronomy Observatory in Green Bank.
The lecture was originally scheduled for October 2013, but the government shutdown sent the NRAO into a furlough. It was rescheduled for January and again canceled, that time due to weather.
Green Bank Telescope principle scientist Dr. Jay Lockman said he was pleased Bennett was able to finally deliver his lecture.
“Every year the Associated Universities Inc. and the National Radio Astronomy Observatory gives out the Karl Jansky Award for Excellence in astronomical science,” Lockman said. “This award has gone to quite a number of prestigious people, some of whom have gone on to win the Nobel Prize in recognition for their science.”
Bennett, an Alumni Centennial Professor of Physics and Astronomy and a Johns Hopkins University Gilman Scholar, said his interest with astronomy began as a hobby when he was a teen.
“I was a ham radio operator,” he said. “I used to tinker with electronics all the time. It was my hobby. Then my grandmother gave me a telescope. I went in the backyard and looked at the stars. I had these two hobbies and around that time, I was reading a book [“The Universe: From Flat Earth to Quasar,” by Isaac Asimov], and I read this paragraph [that rang true to me].”
The paragraph stuck with Bennett and from that point on, he decided he was going to be a radio astronomer.
Growing up in Maryland, Bennett was close enough to West Virginia that his parents knew of the NRAO in Green Bank, leading to a family vacation to the area where he was first introduced to radio telescopes.
“We got on the bus that took us down to where the telescopes were, and I remember the first time you see the telescopes, you think ‘wow, this is just amazing,’ and I remember thinking to myself, ‘what kind of lucky people get to use these telescopes? That’s just so great,’” Bennett said. “I took the tour and then I went on to school. I was in graduate school at MIT and I believe that during those years, I was the single largest user of the NRAO telescope time, using the 300-foot telescope doing a survey of the universe.”
Fortunately, Bennett completed his research for his senior thesis before the 300-foot telescope collapsed. Although it was sad to see the telescope reduced to a pile of rubble, there was a positive side to things. The loss of the 300-foot telescope resulted in the gain of the Green Bank Telescope, the world’s largest fully steerable radio telescope.
In the study of the universe, Bennett said it is important to understand the vastness of the area studied.
“Our sun is only one of one hundred billion stars that make up the Milky Way Galaxy,” he said. “The Milky Way Galaxy is a swirling collection of one hundred billion stars with gas and dust between the stars. Our Milky Way is just one of one hundred billion galaxies in the universe that we see. It begins to give you a sense of how grand the universe is that we are only this tiny part of something that’s sort of unimaginably vast.”
The universe is so vast that although light travels at 671 million miles per hour, or one foot in a nanosecond, it still takes eight minutes for light from the sun to reach Earth. It takes light five and a half hours to travel from the sun to Pluto, the former ninth planet in the solar system.
“Another way to say this is when we look at the sun, we are not seeing the sun as it is the moment we are looking at it,” Bennett said. “We’re seeing the sun as it was eight minutes ago. So, the finite speed of light is giving us, whether we want it or not, a time machine. A way of looking back into the past. This is very valuable to us.”
In order to understand what we are seeing when we look into the sky, it is important to understand the physics of light. The part of physics that helps is gravity.
Bennett said three of the worlds greatest minds – Galileo Galilei, Sir Isaac Newton and Albert Einstein – examined the properties of gravity and how it affects all objects.
Newton’s first law of motion “an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force,” was used by Einstein to prove the Earth was gaining gravity from the sun.
“This was Einsteins breakthrough about how gravity works,” Bennett said. “The reason the Earth knows that the sun is there giving it gravity is because the mass of the sun is literally curving the space around it. In a sense, the Earth is traveling in the straightest line something can go in on a curved surface.”
Knowing that the universe was curving around objects, it verified that the universe is not uniform or smooth. It has fluctuations. In order to understand the fluctuations and to map them, physicists and astronomers looked for a way to map the temperatures across the sky.
“So, people started going out looking to find the little fluctuations of temperature across the sky and that turned out to be much harder than people thought when they started doing it,” Bennett said. “It took twenty-seven years for it to happen. The satellite I worked on called the Cosmic Background Explorer, COBE satellite, was proposed in 1974. It was launched in 1989.
“In 1990 we recorded the temperature of radiation as 2.725 degrees above absolute zero and I keep saying to myself this is our study of the universe where we know that number in four digits,” he continued. “It’s amazing. We’re not just guessing about the universe. We’re measuring things with precision.”
Using the tiny fluctuations in temperatures, Bennett and fellow scientists mapped the Milky Way Galaxy, but knew it was important to have a follow-up mission to learn more about the fluctuations.
“I proposed this Microwave Anisotropy Probe, MAP mission, submitted in 1995,” he said. “Eight investigators, including Dave Wilkinson, who passed away during the course of the work. We named the mission for him. It is now known as WMAP.”
The project used amplifiers built at the NRAO to amplify the microwaves the team was mapping.
“We took those amplifiers and built them into radio receivers,” Bennett said. “We had five different observing bands. The purpose of this was to separate out the Milky Way microwaves from the universe microwaves. It was a key part of the experiment.”
The rocket carrying WMAP was launched in 2001 and was successful in collecting information.
“The most obvious thing that you see in these maps is that red band across the center,” Bennett said, showing maps of the data. “That is the Milky Way Galaxy, again, it’s flat as a pancake. The thing that I’m hoping to point out, the five different bands we’re looking at, you’ll notice the Milky Way signal changes dramatically, but if you squint a little bit and look at the background behind it, all this other stuff, you’ll notice that it’s not changing. The part that isn’t changing is from the universe. The part that is changing is from the Milky Way. That shows you why we wanted the five frequency bands.”
The data shows that the Milky Way is constantly expanding and changing, while the universe around it seems to be stagnant. It also shows what makes up the universe.
“We found that atoms – that’s what you’re made of, that’s what everything in this room is made of – make up only 4.5 percent of the universe,” Bennett said. “Most of the universe is something we call dark energy. We don’t really understand that either, but we know what property it has. Dark energy has the property of acting like an anti-gravity. Most of the universe acts like that.”
While there have been many discoveries about the universe, there are still a lot of unanswered questions for physicists and astronomers.
“Since I mentioned that the Big Bang Theory is not a theory of the beginning of the universe, then the obvious question is what did happen in the beginning of the universe and the answer to that is really easy – we don’t know,” Bennett said. “We have some ideas, and we have the path for finding out using measurements of our universe and learning by observing it.”
The next Jansky lecture featuring 2014 Karl Jansky Lectureship winner Dr. Jill Tarter will be Thursday, October 30, at 7:30 p.m. at the NRAO Science Center.
Suzanne Stewart may be contacted at firstname.lastname@example.org