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  • I'm at the Arecibo Observatory in Puerto Rico.

  • It is one of the world's largest radio telescopes, with a dish 300 metres across.

  • And I had seen pictures and video of this before I came here,

  • but, honestly, the sheer scale is impossible to get across on camera.

  • It is massive.

  • For 50 years, it's been listening to the sky, and one day,

  • it might just save the world.

  • Arecibo's been part of discovering the large-scale structure of the universe.

  • We've discovered pre-biotic molecules in distant galaxies,

  • the first millisecond pulsar, the first exoplanets.

  • The big one, which everyone knows about,

  • is the Nobel Prize for the discovery of the binary pulsar

  • and the way that its orbit decayed exactly as predicted by general relativity.

  • There's 50 years of discoveries here,

  • I could talk for 50 years on discoveries of Arecibo.

  • One of the most incredible things about the observatory is this,

  • the suspended platform that I'm standing on right now.

  • This entire colossal structure is suspended in the air on cables,

  • like a suspension bridge, there are no pillars underneath

  • holding this up and getting in the way.

  • All this weight is being carried by the three concrete towers around the dish.

  • And this platform isn't static: big parts of it move.

  • The telescope, by going a short way north and south,

  • can actually see about a third of the total sky from here.

  • The main bowl of this dish is spherical.

  • The complication, though, is:

  • a spherical mirror doesn't have a point of focus, like a hyperbolic mirror,

  • which we're used to with big optical telescopes and most big radio telescopes.

  • And so, in order to get the signal to a focus,

  • the Gregorian dome contains two smaller reflectors.

  • These smaller reflectors actually bring everything to a point focus.

  • That means, in the Gregorian dome, we can have much wider band receivers

  • and cover from 0.3GHz to 10GHz in frequency.

  • Arecibo can do something that most radio telescopes can't: it can transmit.

  • Famously, in 1974, it beamed the Arecibo message out to the stars,

  • but there are also some more practical uses

  • for sending big pulses of energy into space: radar.

  • Arecibo can bounce radar signals off planets, asteroids and, well,

  • anything nearby in the solar system.

  • And it can build up clear pictures of what's out there in the dark.

  • The advantage of using the radar imaging is

  • you can actually see the shape much better compared to optical imaging.

  • We can actually see boulders on the surface if they are close enough,

  • if it looks like a bone or if it looks like a... sweet potato!

  • The S-band transmitter is a high-powered transmitter

  • that works at 2380MHz of frequency, that's the S-band.

  • The whole transmitter's a megawatt of power.

  • This transmitter produces a beam of power,

  • and if you put your hand right through it you could get burned.

  • We mostly observe near-Earth asteroids.

  • When new asteroids are found their orbit is not very well defined yet,

  • the main thing that we can do is really enhance the orbit information.

  • You transmit a signal and when it hits a moving object

  • the wavelength of the signal changes depending on

  • if the asteroid is moving towards the observer or away from the observer.

  • In that way we can actually get an estimate, to millimetres per second,

  • of the velocity of the asteroid.

  • When new asteroids are found the distance can be determined

  • to hundreds of metres, even tens of metres.

  • We can get very accurate information of where the asteroid will be

  • from now to a decade forward, or even a century forward.

  • Asteroid Apophis, the preliminary orbiting information showed

  • that it actually might hit the Earth.

  • After it was observed with radar they could determine it will come super-close,

  • it will probably disturb some of the satellites that are orbiting Earth,

  • but it doesn't hit the Earth.

  • That's very important to know, because now

  • we know we don't have to send Bruce Willis to deflect the asteroid(!)

  • Of all natural catastrophes,

  • impacts are the one thing that we can actually avoid.

  • Earthquakes, volcanoes, they just happen and we can't actually help that.

  • But if we can observe an asteroid early enough

  • we have an opportunity to deflect it.

  • Thank you so much to everyone at the Arecibo Observatory.

  • If you'd like to know more about them and their discoveries

  • pull down the description for lots of links,

  • and if you want to see behind the scenes on this video

  • then Matt, who's on camera, has been taking a load of footage

  • and has put it together for the second channel.

I'm at the Arecibo Observatory in Puerto Rico.


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アレシボ望遠鏡が世界を救う方法 (How The Arecibo Telescope Could Help Save The World)

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    林宜悉 に公開 2021 年 01 月 14 日