But on the final day of the Munich symposium, in a session entitled 'Extremely Large Telescopes', a capacity audience was stunned to learn just how far this line of reasoning had progressed. The logic went like this: if segmented-mirror technology would allow a 25 metre telescope to be built, why not a 50 metre one? Or even a 100 metre one? Surely the remaining engineering challenges were just . . . engineering? Wasn't it merely a question of adding more segments to the mirror and building a bigger structure to support it and point it in the right direction? So, with the kind of pizzazz normally reserved for the launch of next year's BMW sedan, a project called OWL was ceremoniously launched into the astronomical world.
OWL was to be a telescope of no less than 100 metres aperture with a mirror made up of hexagonal segments measuring 2.3 metres acrossa staggering 1600 of them. They would be carried and pointed by a structure weighing 14 000 tonnes, and the entire assembly would be in the open air, with a sliding hangar to protect it when not in use. OWL's sharp-eyed vision would, of course, require the elimination of the blurring caused by atmospheric turbulence. It would use a bizarre new technique called multi-conjugate adaptive optics, which involved firing multiple lasers into the upper atmosphere to create a constellation of artificial stars for sensors to lock on to. In that way, the exquisite resolution of the mirror could be fully recovered. The telescope would be able to see detail in the sky on a scale of 0.001 arcsecondsa milli-arcsecond. Such unprecedented resolution would give OWL astonishing capabilities in terms of the celestial objects it would be able to detect. Most of the visible Universeliterallywould fall within its grasp.
The promoters of OWL anticipated that it could be built within twelve years, and be delivering front-rank science five years later. All for a cost of US$1 billion. And the meaning of the acronym? Overwhelmingly Large. What else?
Overwhelming was exactly the effect the presentation had on the audience. The prospect of a telescope with more than a hundred times the light-collecting area of an 8-metre for only ten times the cost sounded like the bargain of the millennium, and it was greeted with rapture. And the prospect of milli-arcsecond resolution simply blew the participants away. Even though OWL was as yet totally unfunded, aperture fever spread through the symposium like wildfire. Within half an hour, it had reached plague proportions.
Curiously, OWL's principal advocates appeared ambivalent about the project. One of them wryly made the point that perhaps the instrument should really be called EGOthe Extra-Giant Optical telescope. And maybe it would eventually turn out to be the ULTthe Unnecessarily Large Telescope. Could the fact that these people were also responsible for the VLT have prompted their caution? One day, even their own Very Large Telescope might fall victim to aperture fever.
The epidemic that followed OWL's spectacular entry into the symposium only served to widen the chasm between the opposing factions of moderation and megalomania. Scepticism about the practicalities of building OWL became palpable among those who remained uninfected by the fever. The multi-conjugate adaptive optics system was seized upon as a potential show-stopper, since high resolution was vital to the scientific viability of the project. Everyone agreed that if adaptive optics didn't work and you were going to be limited by atmospheric seeing, the telescope really wasn't worth building.
And some participants simply remained obstinately unimpressed. One insisted on talking only of the NBTthe Next Big Thingwhatever it might be. Another was even more forthright. Coming late into a glitzy presentation on OWL, this eminent scientist stood at the back of the hall and listened for a few moments. Then, with finality, he rudely broke wind and walked out again.
From Stargazer by Fred Watson, pages viii - x of the Prologue, and pages 1-17 of Chapter 1. Copyright Fred Watson. All rights reserved. Excerpt reproduced by permission of Da Capo Press.
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