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[startswithabang]

Ask Ethan: If Light Contracts And Expands With Space, How Do We Detect Gravitational Waves?

“If the wavelength of light stretches and contracts with space-time, then how can LIGO detect gravitational waves. [Those waves] stretch and contract the two arms of the LIGO detector and so the the light waves within the the two arms [must] stretch and contract too. Wouldn’t the number of wavelengths of light in each arm remain the same hence cause no change in the interference pattern, rendering [gravitational waves] undetectable?”

Three years ago, we detected the very first gravitational wave ever seen, as the signal from two massive, merging black holes rippled through the Universe, carrying with it the energy of three solar masses turned into pure energy via Einstein’s E = mc^2. Since that time, we’ve discovered more gravitational waves, mostly from black hole-black hole mergers but also from a neutron star-neutron star merger.

But how did we do it? The LIGO detectors function by having two perpendicular laser beams bounce back-and-forth in a long vacuum chamber, only to recombine them at the end. As the gravitational waves pass through, the arm lengths extend and compress, changing the path length. But the wavelength of the light inside changes, too! Doesn’t this mean the effects should cancel out, and we shouldn’t see an interference pattern?

It’s what you might intuit, but it’s not right. The scientific truth is fascinating, and allows us to detect these waves anyway. Here’s how it all works!

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[archatlas]

Abandoned Places

Kieron Connolly’s new book of photographs of more than 100 once-busy and often elegant buildings gives an idea of how the world might look if humankind disappeared. You can get the book here.

Images and text via

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[the-real-numbers]

I’m a little tipsy and I had homework to type up

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[itscolossal]

The Art Institute of Chicago Now Offers Unrestricted Access to over 52,000 High-Resolution Images from Their Collection

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[shonk]

Double Projection

Take your choice: frames one at a time or all at once.

(source code)

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[startswithabang]

What Was It Like When The Universe Made The Very First Galaxies?

“The first galaxies required a large number of steps to happen first: they needed stars and star clusters to form, and they needed for gravity to bring these star clusters together into larger clumps. But once you make them, they are now the largest structures, and can continue to grow, attracting not only star clusters and gas, but additional small galaxies. The cosmic web has taken its first major step up, and will continue to grow further, and more complex, over the hundreds of millions and billions of years to follow.”

For millions upon millions of years, there were no stars in the Universe. As the first one finally formed, the star clusters that birthed them became the largest structures in the Universe. Yet these were too small and limited to be considered galaxies. For that, we need more than one massive star cluster in the same place. We need for them to merge, triggering a starburst and creating a larger, more luminous object. It takes much longer for that to happen than to merely form stars, and the Universe was a very different place by then. The Big Bang may have started everything off uniformly and without anything more than the seeds of structure, but gravity, and time, are awfully powerful tools.

Come learn what the Universe was like when we made the very first galaxies. It’s a story you won’t soon forget!

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[mathani]

R_blue = (R_green + R_red) / 2

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[itscolossal]

Vietnam’s Newly Opened Pedestrian Bridge Lifts Visitors with a Pair of Giant Weathered Hands

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[geometrymatters]

Fibonacci Sculptures - Part II

These are 3-D printed sculptures designed to animate when spun under a strobe light. The placement of the appendages is determined by the same method nature uses in pinecones and sunflowers. The rotation speed is synchronized to the strobe so that one flash occurs every time the sculpture turns 137.5º—the golden angle. If you count the number of spirals on any of these sculptures you will find that they are always Fibonacci numbers.

© John Edmark

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[itscolossal]

Temporary Installations Create Winding Paths Through a Forest in the South of England