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Comment by metalman | Hacker News Reader

not good, not good at all, as this is how ALL bridges and towers are supported, the basic engineering bieng that any cable end will be stronger than the cable itself and will last longer than the cable itself, except now, when it isn't, not good, not easy to inspect, not easy to service.

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> Long-term low-current electroplasticity, induced by the electromagnetic waves from the Arecibo telescope itself, may have sped up the zinc creep, it says.

I presume we aren't using most bridges as interstellar antennas.

That’s what the government (… and most rational people) wants you to think.

how could the government control the birds without using bridges as antennas?!

No, but there is a lot of potential for large structures to act like an accidental antenna and/or receive low level voltages from the environment or other equipment.

Likely won't matter in most cases, but there could be a few disasters waiting around.

> I presume we aren't using most bridges as interstellar antennas.

any like area of metal will receive as much interstellar emissions but I guess they did run a MW transmitter sometimes.

MW as in Mega Watts? (I read it as Medium Wave the first time)

Yeah it was a radar that could collect the echo on the next rotation of Earth.

No. The radar could observe objects as far as the orbit of Saturn, but typically near-earth asteroids, comets, Soviet ground installations, etc.

It could track celestial positions for about 2.6 hours.

https://en.wikipedia.org/wiki/Arecibo_Telescope#Research_and...

Think about a radar round-trip of 2×12 light-hours; that is 86.57 AU, twice the distance from us to Pluto. Also, the Earth orbits the Sun aside from merely rotating. That radar round-trip would be one cosmic boomerang, looking at nearly nothing.

yes Mega Watts, wattage increased and wave length decreased (to around 10GHz) over time.

No, the receivers were capable of 10GHz.

  3 cm (10.0 GHz)–1 m (300 MHz)

See my other comment (Wikipedia article) for the transmitters' ranges.

https://en.wikipedia.org/wiki/Arecibo_Telescope

Thanks, I assumed transmit matched receive.

While we are being helpful clarifying details perhaps to you could mention something about the difference between the wattage of the power supply used and the Terra watt figure arrived at when switching to EIRP.

As a newish ham I have at least seen the jargon but I fear many of out dear readers may be envisioning nuclear powered death rays with those numbers.

  The telescope had three radar transmitters, with effective isotropic radiated powers (EIRPs) of 22 TW (continuous) at 2380 MHz,[12] 3.2 TW (pulse peak) at 430 MHz, and 200 MW at 47 MHz,[13] as well as an ionospheric modification facility operating at 5.1 and 8.175 MHz.[14]

https://en.wikipedia.org/wiki/Arecibo_message

Arecibo didn’t know it was a telescope. Every wire in the world is an antenna.

The main paper goes into the detail on page 2. The cables were on beam path.

“The only hypothesis the committee could develop that provides a plausible but unprovable answer to all these questions and the observed socket failure pattern is that the socket zinc creep was unexpectedly accelerated in the Arecibo Telescope’s uniquely powerful electromagnetic radiation environment. The Arecibo Telescope cables were suspended across the beam of “the most powerful radio transmitter on Earth. National Academies of Sciences, Engineering, and Medicine. 2024. Failure Analysis of the Arecibo Observatory 305-Meter Telescope Collapse. Washington, DC: The National Academies Press. https://doi.org/10.17226/26982.”

They also mentioned that this is the first example of the unknown phenomena that caused the creep. This technology has been in use quite successfully for more than 100 years.

My guess is the safety factor here was lower than typical, causing the failure mode to occur.

I expect future bridges will design these joints even more conservatively because they were skating closer to the edge than they realized.

Bridges probably shouldn't be subject to the same electromagnetic radiation that gets focused by the telescope though so ideally not a problem there.

Where the cables were there’s nothing focused, just wires, it was outside of the dish.

They were across the dish. From the report: “The Arecibo Telescope cables were suspended across the beam of “the most powerful radio transmitter on Earth””

The role of the cables was for supporting the equipment. The cables that failed, and are examined in the report, were designed to hold the equipment up, while it moved around. These cables weren't involved in carrying signals, data, or power.

There is no denying that energy was induced because of their placement at the focal length of the dish, but that was incidental to their purpose. The bundles of wires were spirally bound around a core. There were certainly ground connections and lightning arrestors involved. The EM effects and properties are discussed on pp 40–47 of the report.

This would predict that we should be seeing far more mystery collapses than we do though

anything, forgive the AI-sounding phrase, "load bearing" in terms of "the load is human lives" is very, very strictly regulated, with inspections mandated and consequences such as load limits and even closures being required when inspections flag issues.

However, even that is not foolproof. Here in Germany, we have had close calls (Rahmede bridge) as well as actual catastrophic failures (Carola bridge in Dresden).

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