Ask Dr. SETI ®
by Dan Duda
from the March, 2016 issue of Penn Central,
the monthly newsletter of Central PA Mensa,
used by permission
Einstein took a real beating in his debates with Niels Bohr and the quantum reality establishment of the early 1900s. But when it comes to cosmology, his theories of relativity, both special and general, continue to make him the Nostradamus of universal predictions. There’s been a lot of news recently about the discovery of “gravitational waves,” and there’s a lot to be excited about. It looks like Einstein’s picture of time and space being a unified continuum or “fabric” is being confirmed.
What makes this exciting? Think about it! First it means that time is flexible—it’s not the constant thing we imagine it to be. Time will flow differently for people under differing conditions. Even issues like the sequence of events can be different for people traveling in separate directions at significant speeds. And what about space? It turns out it’s warped by the gravitational effects of nearby masses, like planets, stars and galaxies. But taken together—Wow! Can you conceive of time and space actually being just one thing, bending and flowing in response to other forces?
It’s important to distinguish “gravitational waves” from “gravity waves.” Gravity waves are a global phenomenon used most often in weather forecasting. Many of the news reports you’re seeing mistakenly used this term to announce the current scientific breakthrough. Gravitational waves, on the other hand, are a cosmological phenomenon. They were predicted by Uncle Albert’s in-credible theory of general relativity developed in the early part of the last century.
How did we detect these gravitational waves? How do we know anything about the universe? Well, it started with light waves. Humans first learned about the universe by looking at the stars (visible light). Later, ‘looking’ was enhanced by the telescope. More recently the Hubble space telescope penetrated incredible distances by observing infrared and ultraviolet light. And observing microwaves and radio waves that are emitted by the cores of galaxies allowed us to penetrate beyond the barriers that block our view of objects when we are limited to the human light spectrum. But now the technology that enhances our ability to “see” has made another major leap forward.
Let’s start with the fact that Einstein predicted that the acceleration of massive objects would churn the fabric of the space-time continuum which would cause waves to form—much like the waves that emerge in water when you throw a pebble into a pond. Two of the most massive objects we know of, black holes, have been courting each other in deep space. Finally, the irresistible gravitational attraction would not be denied, and their dance ended in a conjoining of the two massive objects (sounds like a marriage, right?). The resulting roil, according to Einstein’s theory, should generate “gravitational waves” that spread through space-time at the speed of light.
So, how did we detect these waves? LIGO. That’s the Laser Interferometer Gravitational-wave Observatory. The collision of two black holes is a super-massive event. Yet, by the time the waves cross an enormous stretch of the universe to reach Earth, the waves are extremely subtle. So the apparatus de-signed to receive the signal had to be extremely sensitive. LIGO bounces laser light back and forth through 4-kilometer-long pipes. This process measures the very slight changes in space-time that indicate a gravitational wave passing through Earth.
This is what occurred on September 14th, 2015. Since then researchers have been analyzing the results to ensure the significance of the signal as proof of the elusive gravitational wave. And this was confirmed with a 5.1 sigma significance. In English that means that there is only a one in 6 million chance that the result is erroneous.
This discovery is important on many levels. First, it confirms an incredible pre-diction of Einstein on the nature of the universe. Next, it provides a powerful new tool for exploring the universe. And, it paves the way for another advance in technology—that is using the LIGO concept with satellites placed at a Lagrange point between the Earth and the Sun. It will be the biggest “machine” ever made. In the immortal words of Albert Einstein:
“To raise new questions, new possibilities, to regard old problems from a new angle, requires creative imagination and marks the real advance in science.”
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this page last updated 5 March 2016
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