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PRI's Environmental News Magazine

Gravity: What's Up Is Down

Air Date: Week of April 4, 1997

GRAVITY: WHAT'S UP IS DOWN - The mysteries of gravity are taking scientists to the frontiers of the universe. Scientists are building huge devices on earth to measure gravity from the deepest reaches of the outer space. They say these gravity observatories will be as revolutionary as the first telescope; and will completely change our image of the universe. Living on Earth contributor Bob Carty prepared this report on the ups and downs of the Big "G".

Transcript

CURWOOD: It's NPR's Living on Earth. I'm Steve Curwood. Living on Earth, the process if not the program, wouldn't be possible without gravity. One of the 4 fundamental forces of nature, gravity is the least studied. We don't really know why things have gravity; we just take it for granted. But now, the mysteries of gravity are taking scientists to the frontiers of the universe. Scientists are building huge devices here on Earth to measure gravity from the deepest reaches of outer space. They say these gravity observatories will be as revolutionary as the first telescope and will completely change our image of the universe. Living on Earth contributor Bob Carty prepared this report on the ups and downs of the Big "G."

(Music up and under -- James Brown: "Gravity! Yeah!")

VOGT: You have no idea. We have never seen the universe through the gravitational wave window. It is going to open up a new window in the universe and it's going to open up a new discipline of science: gravitational wave astronomy.

(James Brown continues: "Gravity! The Big G! G-R-A-V-I-T-Y!)

CARTY: James Brown, the godfather of soul, the -- uunh! -- I feel good man of rhythm & blues, is not, whatever else he may be, a theoretical physicist. James Brown has, however, captured some of the excitement that scientists are now feeling about gravity. In Pasadena, California, physicists are spending 350 million US dollars on something they call the ...

VOGT: Laser interferometer gravitational wave observatory.

CARTY: Fortunately, the laser interferometer gravitational wave observatory has an acronym, something that sounds like little toy building blocks.

VOGT: Named it a LIGO.

CARTY: That's right. LIGO. And Robbie Vogt is its principal scientists.

VOGT: The universe which was known before World War II optically was a serene universe. It was, everything was so harmonic and quiet and peaceful and elegant. And then in World War II we developed radio science and applied it after World War II to radio astronomy. And when we started listening in the radio astronomy band, our whole perspective of the universe changed from this serene universe became the violent universe. Quasars and exploding supernovae and all that kind of stuff. I mean, violence. Now, we are moving to a totally new force. There is every right to believe that there will be fantastic new discoveries to be made, and our eyes will open with completely new insights about the universe.

CARTY: New insights about the universe, all from gravity. Albeit from a more complex understanding of gravity than most of us studied at high school. Back when we were young, gravity was just the good old fashioned what goes up must come down. The kind of gravity you find at an amusement park.

(Amusement park music, rides, shooting galleries)

MAN: This ride is called the Colossus.

(Shouting children; clanking gears)

MAN: They're an old wooden roller coaster. It's my first time on.

CARTY: You know what gravity is?

MAN: Yes.

CARTY: What is gravity?

MAN: It's the natural pull against the earth. We have a tendency to want to go down but we're taking it up.

CARTY: What my roller coaster colleague and I are about to experience are the basics of gravity. Everything that has mass exerts a force, and as Isaac Newton figured out under an apple tree 3 centuries ago, that gravitational force is proportional to the product of the masses of the 2 objects and inversely proportional to the square of the distance between them. You might recall memorizing that in high school. And even if you don't, it still
works.

(Clanking continues)

MAN: Here we go! Sit...

(Children scream as the roller coaster drops)

CARTY: But it doesn't always work. Newton's concept of gravity works just fine in our daily lives, but it tends to break down inside the atom, in the realm of quantum physics. And Newtonian gravity also doesn't work on the really big scale.

(DRAMATIZATION FROM A FILM: Knocking. Man: "Yes? Oh. You're Albert Einstein." Einstein: "Thank you." Man: "Wow. That thing you wrote about light being bent by gravitation and the whole relatively thing? Man, I'm still trying to figure it out." Einstein (laughing): "Me, too.")

CARTY: Mention the name Albert Einstein and you usually think of E=MC2, the relationship between energy and matter. In fact, most of Einstein's noodling was on the subject of gravity.

(Einstein: "We have a little gravity problem.")

CARTY: For Einstein, the problem was to figure out how gravity works on the level of galaxies and neutron stars and black holes: the Big G. Einstein predicted that really massive objects would bend a ray of light, even space and time itself. The project director of LIGO is physicist Gary Sanders.

SANDERS: One way to think about it is, if the whole universe was on a rubber membrane like a drum head, and I put a stone on the drum head, it would curve the drum head down near the stone. And if I were an object, a little ball bearing on the drum head near the stone, I would fall down into that curvature. A property of mass is that it distorts, it curves the space and time about it. The beam of light leaving the vicinity of a black hole actually travels through space and time that is so highly curved that it curves back in on itself.

CARTY: We're talking here about gravity so strong it could be unpleasant.

SANDERS: If I were an astronaut and I were falling slowly into a neutron star, like a little neutron star with one and a half times the mass of our sun, the force on my feet, if I were falling feet first, would be so much stronger than the force on my head that I'd be torn in half.

(Xylophone descending. Einstein Character: "That gravity, it's a killer.")
Fade to James Brown: "G-R-A-V-I-T-Y. Gravity! Who! The Big G!
G-R-A-V-I-T-Y! Gra-vi-teeeee!...")

CARTY: Now as James Brown would say --

(Brown: "Wait a minute...")

CARTY: Wait a minute. All this space time stuff is fine and good, but why spend $350 million dollars on it? How is LIGO going to work as an observatory to explore the universe? To figure this part out, we have to go from the roller coaster to the beach.

(Surf's up)

SANDERS: We're standing on the beach at Santa Monica near the Santa Monica pier, and we can hear the sound of waves rolling in. Some are out there; something made those waves. A wind, some disturbance. This is very much like what we hope to do with LIGO. We hope to be sitting on our shores here on Earth listening to the sounds of the universe as the gravitational waves roll in.

CARTY: Waves. That's the key to understanding the universe with LIGO. It was another of Einstein's great insights: big masses not only have gravity. When they move very quickly they make waves. Gravitational waves. Wrinkles in space and time.

SANDERS: When a gravitational wave reaches the Earth from 2 neutron stars colliding, it will pass through me and it will make me taller for an instant and narrower, and an instant later, shorter and wider.

CARTY: Why can't we feel it?

SANDERS: We can't feel it because the distortion -- I said the gravitational wave would make me taller for an instant. But it would make me taller by about a 10,000th the size of an atomic nucleus, and I can't feel that.

CARTY: And that's why scientists are now building the LIGO.

(Fans and motors)

SANDERS: We're standing in the clean room in which the LIGO 40-meter prototype is located. And we're looking down the 2 arms.

CARTY: In an old building at the California Institute of Technology in Pasadena, the LIGO prototype is 2 long steel tubes arranged in the shape of an el. The tubes are exactly the same length, a fact that is measured by a green laser light bouncing back and forth on mirrors inside the tubes. The real LIGOs, 2 of them, are much bigger. They're being built in the countryside of Louisiana and Washington State.

SANDERS: In the full LIGO instrument the tube you're looking at will be 4 foot in diameter. You can crouch down and walk through it and it will be 2 and a half miles long, and there will be a mirror suspended at each end of them. And in between these 2
mirrors will be traveling the laser light. If a gravitational wave passes through the Earth and passes through our apparatus it will make one of these arms a little bit longer and the other one a little bit shorter.

CARTY: And when that happens, the 2 LIGO instruments will tell scientists where in the universe the gravitational waves came from, and what made them. That's because gravitational waves are a Christmas pudding of information. Robbie Vogt, the principal scientist at LIGO.

VOGT: The exciting thing about gravitational waves is, they're like, very much like radio waves. They carry information, like in a radio wave you have a symphony or a newscast or something like that. And if you for example play back gravitational wave through a conventional medium like a microphone or something like that, the frequencies are in the audio range, in the range which we hear music.

CARTY: You're saying we can hear gravitation?

VOGHT: It's fun. You can actually simulate how a gravitation wave would sound.

(A sound like crickets humming)

CARTY: And it sounds like this. This is the song of 2 neutron stars, each weighing about one and a half times more than our sun. The note is made by the 2 stars spinning around each other at the incredible speed of 57 orbits a second.

(Sound continues)

CARTY: Then the spinning increases to 4,000 times a second just before the 2 stars collide into each other and become one.

(Sound continues, with another rising from the bass range to match frequency; quick fade out)

VOGT: It's basically, space is compressed and elongated and compressed and it's squeezed and pulled apart. And the frequency with which this deformation take place is the audio frequencies. And that's kind of fun, you know; you can hear the symphony which comes out of space.

(Music up and under: synthesized sounds)

CARTY: And the symphony could be revolutionary. LIGO's potential for discovery is akin to Galileo looking through the first telescope and Columbus arriving in the Americas, combined. Robbie Vogt says it's worth the multi-million dollar investment.

VOGT: You have no idea. We have never seen the universe through the gravitational wave window. And when you remember that 90 percent of the universe is admittedly invisible to us right now,I don't know what fractional gravitational waves will fill in, but it will be a significant fraction. So they will give us new information. It is going to open up a new window in the universe and it's going to open up a new discipline of science:
gravitational wave astronomy.

(Cellos)

CARTY: Scientists hope that in the year 2001, LIGO will be ready to detect the first gravitational wave ever observed by humans. The project expect to find at least 3 neutron star collisions a year. And then, by improving its technology, LIGO could gain the capacity to draw a new map of the universe using gravitational waves. Our knowledge of the skies and of gravity will never be the same. For Living on Earth, I'm Bob Carty.

(Amusement park ride clatters. CARTY: "Hey! You know what gravity is?" Children scream as roller coaster descends. Fade to James Brown: "G-R-A-V-I-T-Y. Gra-vi-teee, yeah!")

CURWOOD: Ooh! Good God! It's NPR's Living on Earth. I'm Steve Curwood.

(James Brown up and under: "Ain't it funky...Ain't it funky...God...God...")

 

 

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