Thread by @astrotweeps

I'm late to tweet today so please accept this bonus story: The Telescope That Fell Down

For this we head to Green Bank Observatory, in the US National Radio Quiet Zone in West Virginia.

In 1988 it was home to the 300 Foot radio telescope.

Isn’t it gorgeous? and TALL?...

The Radio Quiet Zone is a fascinating place, with strict restrictions on tech use to minimize radio noise.

In a 20mi radius around the observatory, Wi-Fi, cell phones, and microwaves are banned. Vehicles even run on diesel to prefer interference from gas-engine ignition sparks.

(there’s a great mini-story from this observatory about one particular astronomer who drove a clunky old car that always showed up as interference in the telescope data, to the point where they could tell when he was arriving at the site)

(one day someone supposedly saw the telltale interference pattern and said “oh, X must be on his way!” They looked out the window and sure enough, he was coming down the road…on a bicycle.)

Anyway, all of this was GREAT for radio astronomy. By 1988 the 300 Foot had been instrumental in some incredible research: it had studied studied the birth of new stars, helped discover dark matter, and done a huge radio survey of the sky.

It was HUGE: 23 stories tall & 600 tons with the eponymous 300-foot-diameter parabolic dish made of white metal mesh

(one colleague handed me a piece of that mesh while I was interviewing her. if you’re holding a piece of a telescope's dish it's safe to say something went wrong)

Around mid-November of 1988, folks at the observatory started noticing that the 300-Foot dish would make the odd snapping or pinging sound here and there. A little weird, but enh, big metal structures creak and make noises sometimes, right?

On the rainy evening of Nov 15th, 1988, the 300 Foot was trucking along, working on its radio-wavelength sky survey.

(the next day the observatory crew was planning to perform a routine receiver swap, a process that involved people physically climbing high on the dish itself...)

There was just one operator at the 300 Foot that night, sitting in the control room directly beneath the telescope.

He was heading down the hall during a standard sky-scan exposure when he heard a loud crack, rumble, and crash, followed by something smashing through the ceiling.

He whirled back to the control panel, smacked the emergency stop button, and sprinted out the door and into his truck to get help.

He found a couple other staff members. One noticed the truck’s back window was smashed, with a bolt “painted like the 300 Foot” on the backseat.

The three observatory employees didn’t get the full scope of what had happened until they were driving back together in the rain and turned up the road toward the control building and telescope.

Imagine being in that truck and seeing THIS materialize in the headlights...

Gigantic telescope beams had punched straight through parts of the building.

INCREDIBLY, nobody had been hurt.

That night the crew mainly focused on saving the electronics in the building from the rain (since the falling telescope had taken out the roof).

The next morning word spread.

Everyone who heard the news started with sheer skepticism (because really, telescopes don’t simply FALL DOWN), then drove to the site and joined a growing group of nonplussed astronomers and staff members standing there gaping at the wreckage.

There was, unsurprisingly, a HUGE investigation: auditing design plans and construction reports, reviewing safety inspections, interviewing crew members...

Even the poor crumpled telescope tried to help solve the mystery of its own demise. It had actually kept taking data even up through the start of the collapse, which illustrated the early moments when the enormous dish began to lose its shape.

The final result? One single - but VERY critical - gusset plate in the main support truss of the telescope had been overstressed. Maintenance had been done appropriately. Inspections couldn’t have found it. There was no reason to think other radio telescopes were at similar risk.

The telescope had, in short, simply fallen down.

I tell more of this story in #TheLastStargazers (get it at the link! thelaststargazers.com)

Green Bank Observatory has also compiled a great collection of science papers & personal stories, including a full account of the collapse, gloriously titled "But It Was Fun"...

...and happily, the observatory was able to build a new enormous telescope, the Green Bank Telescope - with a 100-meter dish! - that's still operating at the site and continuing to do spectacular radio astronomy 📡🤗