What is LIGO? Well, it begins with Albert Einstein. He brought forth the idea of gravitational waves. Einstein described space-time as like a fabric. The presence of large amounts of mass or energy cause the "fabric" to warp, thus distorting space-time, creating curves. When large masses move suddenly, these curvatures ripple outward, spreading, similar to the ripples caused by a pebble being thrown into a pond. As the fabric of space stretches in one direction (say, left to right), it compresses inversely (top to bottom). Like pulling on a piece of mesh fabric.
LIGO detects the ripples in space-time by using a device called a laser interferometer. Basically, two 4 km tubes (arms) are laid perpendicular to one another. From where they intersect, a beam of light is emitted and splits into halves; one half entering into the X tube and one into the Y tube. At the end of each arm (a metal tube covered in concrete so as not to attract lightning), the laser light bounces off a mirror and heads back to the splitter. Since both arms are the same length and the beam of light is one single beam split, the lights should return to the splitter simultaneously, and when they hit the laser, cancel each other out. If there is any difference between the lengths of the arms, one beam may return from the mirror before the other beam, and thus some light will travel to where it can be recorded by a photodetector. This would be evidence of some sort of gravitational wave, according to LIGO.
Why would one arm be longer than the other? Well, it goes back to the mesh fabric. When those ripples occur in outer space, they disrupt the fabric that is space-time, distorting it as if we pulled on mesh. This would, in theory, "lengthen" one arm, thus altering the time the light takes to return.
This is worth watching: LIGO
I say in theory because, since opening in 2000 to the tune of $300M tax-payer dollars, no gravitational waves have been detected.
But, I am no physicist. So, let's talk about what you can do when you visit.
Tien, our guide, was wonderful. Like a hands-on science museum, there are plenty of exhibits, models, and displays to play with and learn from. We saw a 7-minute video (I think the youtube one I inserted here was better), had lots of time with the exhibits, and got a guided tour of part of the facility.
|Tien explains how our eyes can trick us.|
|Iron filings and strong magnets are very cool.|
|Creating waves and nodes.|
A node is a point along a standing wave where the wave has minimal amplitude.
So, what that means is, everywhere but the red dots is moving. This contraption the kids are looking at has white sand vibrating around, except for where the nodes are, and a design is created. You can create different designs by changing the frequency of the wave.
|Heat sensors. Our noses and fingers were black from low to no heat. Except Steve. He had no cold areas!|
|Wearing prism glasses and trying to shoot a basketball. You had to keep learning how to re-see and make adjustments.|
|Tien explains air pressure using a soda bottle (with the top placed at the bottom) and a balloon. This was cool.|
|Doug "walks" us through the arms and the "clean" rooms where the laser begins. The graphs above his head measure the vibrations caused by the ocean, earthquakes, and people.|
|Playing with the earth and a blower.|
|LIGO and a part of one of the arms.|
|Slinky showing us waves and nodes.|
|Playing around with light and mirrors.|
|Having fun with bubbles.|
As you travel, talk to the librarians and check out some of these local, hidden gems. We had a very educational and fun day.