NASA Home Page Beyond Einstein Site Map Beyond Einstein Home Bypass navigation links and go to page content
NASA
SEU Banner
Beyond Einstein Banner
Spacer
The Science
Spacer
The Program
Spacer
Great Observatories
Spacer
Probes
Spacer
Vision Missions
Spacer
What/s New
Spacer
Press Room

2003 Roadmap
Spacer
The Technology
Spacer
Education
Spacer
Life Cycles of Matter and Energy
Spacer
Resources
Spacer
People
Spacer
Contact Us
Spacer
Beyond Einstein Home
Spacer
Spacer
The Science

Scientific Goals and Missions

Cosmic Cacophony: Gravitational Waves

Black holes can also be studied by listening for the "sounds" they create, a novel form of energy called gravitational waves.

Supermassive Black Hole Merger
Supercomputer calculation of the gravitational waves produced in the merger of two supermassive black holes (Courtesy E. Seidel and W. Benger)

Since ancient times, astronomers have used one form of energy to study the Universe. Called simply "light," it includes X rays and radio waves and all the colors of the rainbow in between. Light is made of vibrating waves of electric and magnetic fields traveling through space.

In Einstein's theory of gravity, energy can also be carried by vibrating waves of space and time, which travel at the speed of light. In the same way that black holes are made just of space and time, gravitational waves are also "pure" space and time. They interact very weakly with matter and penetrate anything without losing strength. While this makes them powerful probes of extreme conditions, it also makes them hard to detect. They interact so weakly with measuring apparatus that only in the past few years has technology advanced to the point that we are confident we can build equipment to detect them.

The most powerful outflows of energy in the Universe are not carried by light but by gravitational waves emitted when two black holes orbit, collide, and merge. In the final minutes or hours before the merging of a single pair of supermassive black holes, a gravitational power of about 1052 watts is radiated. This is a million times more power than all the light from all the stars in all the galaxies in the visible Universe put together, and millions of times more powerful than the most powerful single sources of light: gamma-ray bursts. It is possible that the Universe contains more of this gravitational radiation than it does light.

Detecting gravitational waves will give Einstein's theory a workout it has never had before. We know that it works pretty well in normal circumstances---without "spacetime curvature technology" in their software, airplanes using GPS navigation would miss their runways by miles---but gravitational waves offer much more profound potential. They will let us listen carefully to the most violent events in the Universe, the collision and mergers of black holes. What goes on there is a swirling knot of spacetime interacting mostly with itself. A black hole merger can also briefly expose to observation the singularity at the heart of the black hole, where Einstein's theory must fail. The sounds of the Universe will tell us how well Einstein's ideas still work in these extreme conditions. They will also allow us to penetrate times and places impossible to see with ordinary light, such as the birth of our Universe. They might reveal startlingly violent events, such as the formation of our three-dimensional space from an original space with more dimensions.

Gravitational waves produce tiny jiggles between masses that are floating freely in space, isolated from all forces other than gravity. The distances between the masses can be monitored using laser interferometry. An early generation of such systems has now been deployed on the ground---the NSF-funded Laser Interferometer Gravity-wave Observatory (LIGO) in the US and similar systems worldwide. It is hoped that these systems will make the first detection of gravitational waves from some sources of high-frequency waves. The Beyond Einstein Great Observatory LISA will operate in a broad band at much lower frequency. It will detect entirely different sources in great numbers and with exquisite precision.

The most powerful gravitational waves come from quickly-changing systems with very strong gravity, so LISA's strongest signals will probably be tones from black holes spiraling into other supermassive black holes. LISA will also detect for the first time gravitational waves from calibrator sources (such as orbiting pairs of white dwarf stars) that have been studied by optical telescopes.

LISA will break ground for the new science of gravitational wave astronomy. The vision mission Big Bang Observer will extend the reach of gravitational wave astronomy towards its ultimate limit---detecting the quantum noise from the inflationary Universe.



| The Science | The Program | Great Observatories | Probes | Vision Missions | What's New | Press Room |
| What powered the Big Bang? | What happens at the edge of a black hole? | What is dark energy? |
| 2003 Roadmap | The Technology | Education | Life Cycles of Matter and Energy | Resources | People | Contact Us | Site Map | Home |

A service of the Exploration of the Universe Division at NASA Goddard Space Flight Center
Web site design and maintenance by Pat Tyler, tyler@milkyway.gsfc.nasa.gov

Responsible NASA Official: Phil Newman
| |