Black Holes by Latta Sara;

Author:Latta, Sara; [Latta, Sara]
Language: eng
Format: epub
Tags: Nonfiction, Young Adult Nonfiction, Young Adults, Technology, Aeronautics, Astronautics, Space Science, Space, Science, Astronomy, Astronomer, Stars and Galaxies, Albert Einstein, astrophysics, Big Bang Theory, Black Holes, Black Holes: The Weird Science of the Most Mysterious Objects in the Universe, Earth and Space Science, Einstein, Galaxy, Gravity, Invention and Technology, Isaac Newton, Mass, Matter, Milky Way, Newton's Laws, Newton's Laws of Motion, Outer Space, Physics, Planets, Relativity, Sara Latta, Science and Technology, Science Exploration, Science, Nature & How It Works, Science, Nature, and How It Works, Scientist, Scientists, Solar System, Space Exploration, Star, Stars, Stem, Telescope, Telescopes, Telescopes in Space, Tools and Technology, Twenty-First Century Books, Universe
ISBN: 5444412
Publisher: Lerner Publishing Group
Published: 2017-07-31T16:00:00+00:00

This diagram reveals changes in the rate of expansion since the universe’s birth fifteen billion years ago. Astronomers theorize that the faster expansion rate is due to a mysterious, dark force that is pushing galaxies apart.

How Did LIGO Detect Gravitational Waves?

It’s very likely that gravitational waves pass through our bodies all the time. But since gravity is a weak force in the universe, we don’t feel a thing. A passing gravitational wave might change the distance between you and the person sitting next to you by about a millionth of the diameter of a proton. It would take an awfully sensitive instrument to detect a gravitational wave. In fact, Einstein doubted scientists would ever be able to detect them.

The LIGO scientists decided to give it a go. They spent decades planning and constructing two observatories, each one functioning like an exquisitely sensitive pair of rulers. One is in Hanford, Washington, and the other is in Livingston, Louisiana, 1,865 miles (3,002 km) away. The LIGO team put the two detectors far apart on purpose. This way, they could tell whether a little jiggle was due to local vibrations only or to a gravitational wave from outer space. It would also allow them to get a general sense of the direction from which the wave came. Each observatory has an L-shaped vacuum tube, from which a vacuum pump has removed all air and other gases. Each arm of the tube is of equal length, a little more than 3.2 feet (1 m) wide and 2.5 miles (4 km) long. The arms are so long that project engineers had to raise them by 3.2 feet at each end so that they lay flat above Earth’s curvature below.

A computer-controlled laser beam at the crook of the two arms is split into two. Each beam shoots down and hits a mirror at the end of the arm. The mirror sends the light bouncing back to the source at the crook of the arms. The speed of light in a vacuum is constant, so the beams should return to the source at the same time. Unless, that is, a gravitational wave ripples through LIGO’s arms. Then one arm of the L would be stretched out while the other would be squeezed short. Since the beam in the stretched arm would have to travel a longer distance than the one in the squeezed arm, the two beams would arrive back at the source at different times. The strength of the gravitational wave would dictate this difference in time. So a mild gravitational wave would lead to only a slight difference in the time it took both beams of light to return. A stronger wave would create a greater difference in the timing.

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