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posted: 11/15/2016 10:19 AM

# Scientists agree there's a fourth dimension of space-time

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• This composite image provided by NASA, taken by NASA's Chandra X-ray Observatory and other telescopes, shows a galaxy where a supernova probably resulted in a black hole in the bright white dot near the bottom center.
AP Photo/NASA

"What is the fourth dimension?" asked a camper who attended this summer's Wauconda Area Library STEM program.

The fourth dimension is a concept that connects to astronomy and astrophysics.

One dimension is a line, point A to point B. The second dimension is a plane, like a piece of paper. The third dimension has height, width and depth, like a pencil, a cube or even a person.

Geometry invites mathematicians to study three-dimensional figures to determine height, area and relationships between three-dimensional objects. In computer graphics, items that show height, width and depth are defined as virtual reality.

Shane L. Larson, gravitational wave astrophysicist, associate professor at Northwestern University's Center for Interdisciplinary Exploration and Research in Astrophysics and Adler Planetarium astronomer, describes the three dimensions in relationship to movement: "I can move forward or backward, first dimension; I can move left or right, second dimension; or I can move up or down, third dimension."

The idea that time could have a greater value was pondered by Galileo in the 1500s and Newton in the 1600s. In the 1900s, Einstein connected gravity, time and space to create the theory of special and general relativity, observing that a wristwatch ticks differently in strong gravity areas, such as the area surrounding a black hole.

Today, scientists agree a fourth dimension of space-time exists, and recently found proof. For example, have you ever seen a large circle of cackling starlings flapping at the treetops? The strange sound breaks the normal silence of a late fall day and draws attention to the sky. Why would a flock of birds fly erratically, diving and swerving and squawking? Could an unseen predator be waiting nearby? The fourth dimension is one of those things best seen by observing the reactions of objects surrounding it.

A recent recording of gravitational waves proved the birth of a black hole, the densest object in the universe. Two interferometer detectors belonging to LIGO (the Laser Interferometer Gravitational Observatory), one in Louisiana and one in Washington State, measured gravitational wave motion 1,000 times smaller than an atomic nucleus. Captured a year ago, that detection was the first recorded observation of gravitational waves, confirming the concept of space-time. Larson works with both LIGO and LISA, NASA's space-based gravitational detector now under construction.

Larson discussed what Einstein predicted more than 100 years ago, a fourth dimension of space-time.

"The reason it took so long to realize that time was a dimension is that it is a bit different. We definitely move through time -- you and I are definitely moving forward to next Tuesday. There are two differences compared to other dimensions: you cannot stop yourself from moving forward in time. It happens to you regardless of whether you want it to or not; and you cannot move backward in time. You and I can easily get to next Tuesday. It seems to be impossible to go back to last Wednesday."

Being curious and asking a lot of questions is the hallmark of scientists like Larson, the author of the public science blog "Write Science" at writescience.wordpress.com, where he discuss modern ideas about astronomy, physics and space-time. He also can be found on Twitter under the handle @sciencejedi. In addition to his contributions to gravitational astrophysics, Larson enjoys astronomy, rocketry and high altitude balloons.

Get a feel for what it's like to be a gravitational wave researcher by becoming a Gravity Spy. LIGO calls on Citizen Scientists to help search through data and detect gravitational wave traces. See the LIGO website for more information, www.ligo.caltech.edu/news/ligo20161018.