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Casting a $20 Million Mirror for the World’s Largest Telescope

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Building a mirror for any giant telescope is no simple feat. The sheer size of the glass, the nanometer precision of its curves, its carefully calculated optics, and the adaptive software required to run it make this a task of herculean proportions. But the recent castings of the 15-metric ton, off-axis mirrors for the Giant Magellan Telescope (GMT) forced engineers to push the design and manufacturing process beyond all previous limits.

Building the GMT is not a task of years, but of decades. The Giant Magellan Telescope Organization (GMTO) and a team at the University of Arizona's Richard F. Caris Mirror Laboratory cast the first of seven mirrors back in 2005; they expect to complete construction of the telescope in 2025. Once complete, it’s expected to be the largest telescope in the world. The seven 8.4-meter-wide mirrors will combine to serve as a 24.5-meter mirror telescope with 10 times the resolution of the Hubble Space Telescope. This will allow astronomers to gaze back in time to, they hope, the materialization of galaxies.

Each mirror costs US $20 million dollars and takes more than two years to build. Every stage of the manufacturing process calls for careful thought and meticulous planning. To begin, more than 17,000 kilograms of special glass are ordered and inspected for flaws. Next, a crew must build a 15-metric ton ceramic structure to serve as a mold for the glass, which they carefully place one chunk at a time. The glass is slowly melted and continuously spun in a furnace to create a parabolic shape, then cooled by fractions of degrees over the course of three months. And that’s only the beginning.

Once cooled, massive machinery lifts the mirror and tilts it to a vertical position. Engineers purge the ceramic mold from the mirror, wait for it to dry, and then rotate it again. They grind and refine the back of the mirror with exacting precision. Then they reposition the mirror in order to shape and polish the front face to within 20 nanometers of perfection—a process that takes about 18 months. Along the way, it undergoes four optical tests, some of which were engineered specifically for this project.
Any mammoth mirror requires much of the same engineering, but six of the seven GMT mirrors have an off-axis, parabolic shape. Producing an off-axis mirror at this scale is a new achievement for the Caris Mirror Laboratory and for the field in general.
Once four of the mirrors are complete, they must be transported to the Chilean Andes, where the giant telescope will be constructed on the peak of a mountain range. Even the transport to Chile will be a challenge—so much so that the teams have yet to decide exactly how they’ll pull it off. Still, GMTO says it is on course for the four-mirror installation and “First Light” in 2023, when the telescope will be turned to the night skies for the first time.

And then we’ll all get a chance to peer into the maternity ward of the cosmos and see galaxies being born.

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silentpark
2 days ago
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video ;)
Hamburg, Germany
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New Year's Resolutions

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Happy New Year! I drew this comic for Evernote.

For more great comics (including a few on New Year's resolutions), you can order my Shape of Ideas book and calendar. They are available internationally wherever books are sold!
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silentpark
13 days ago
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Hamburg, Germany
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Photoediting before Photoshop

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Intricate squiggles and numbers are scrawled all over the prints, showing Inirio’s complex formulas for printing them. A few seconds of dodging here, some burning-in there. Will six seconds be enough to bring out some definition in the building behind Dean? Perhaps, depending on the temperature of the chemicals.
As a youngster I developed some of my own film and studied (but never implemented) advanced darkroom techniques.  I began to wonder if I would ever see the phrase "dodge and burn" used again.

More information at The Literate Lens.  Image cropped for size from the one at Gizmodo, via Neatorama.
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silentpark
25 days ago
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Hamburg, Germany
jepler
36 days ago
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Earth, Sol system, Western spiral arm
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100 Fiberglass and Resin Skulls Fill a Room at the National Gallery of Victoria in Melbourne

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Ron Mueck, an Australian artist known for his hyperrealistic figural sculptures, has created his largest work to date. His installation Mass contains 100 human skulls which are scattered and stacked throughout a gallery at the National Gallery of Victoria in Melbourne, Australia.

The individual forms are created from fiberglass and resin, and when stood upright, rise to approximately three feet tall. In some areas of the installation piles reach five skulls in height, while in others visitors can approach individual works resting on the gallery’s floor. Placed amongst gilded paintings the works offer a somber reality, a morose peek into what physically relates each of us.

Mass opens December 15, 2017 as a part of the inaugural National Gallery of Victoria Triennial. Mueck is one of 100 international creatives that has contributed work to the exhibition which will run through April 18, 2018. (via Designboom)

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silentpark
25 days ago
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Hamburg, Germany
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Drone shots of NYC

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Among Humza Deas’ hundreds of shots of NYC on his Instagram are a collection of drone shots of the city taken in the fall.

Humza Deas Drone

Humza Deas Drone

Humza Deas Drone

I know that last one has been filtered to within an inch of its life and I normally don’t cotton to those sorts of shenanigans, but this one makes me feel so fricking autumnal that I’ll allow it.

Tags: Humza Deas   NYC   photography
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silentpark
27 days ago
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Hamburg, Germany
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The rates of traffic flow on different kinds of 4-way intersections

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This is an animation of traffic flows simulated on 30 different kinds of four-way junctions, from two roads intersecting with no traffic lights or signs to complex stacked interchanges that feature very few interactions between individual cars. It was recorded in a game called Cities: Skylines, a more realistic take on SimCity.

The developer’s goal was to create a game engine capable of simulating the daily routines of nearly a million unique citizens, while presenting this to the player in a simple way, allowing the player to easily understand various problems in their city’s design. This includes realistic traffic congestion, and the effects of congestion on city services and districts.

I don’t know how accurate the observed rates of flow are — where my transportation engineers at? — but it’s super interesting to watch the various patterns get increasingly complex and efficient, and how the addition of dedicated turn lanes, roundabouts, overpasses, and slip lanes affect the flow. Be on the lookout for the turbo roundabout, the diverging windmill (which, coincidentally, is the name of my signature dance move), and the incredibly complex pinavia,1 which can handle almost five times the traffic flow compared to a simple intersection with no lights.

  1. The pinavia interchange is apparently patented, which is a fascinating thing in its own right.

Tags: traffic   video
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silentpark
27 days ago
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Hamburg, Germany
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1 public comment
HarlandCorbin
27 days ago
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Anyone notice the vehicles moving through each other?
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