Great Big Thing
Ponder Stibbons has learned all about academic politics so as to get larger grants from the Faculty for the High Energy Magic Building. Unseen cannot be seen to lose face nor be out-trumped by the upstart rival. So Ponder's hints that Unseen's VBT (Very Big Thing, specifically Hex) might be superseded by Brazeneck's, although it's only a QBT (Quite Big Thing) now. The senior faculty are concerned that an EBT (Even Bigger Thing) might be in the works. Having discovered a way of getting research money out of the senior wizards - "we can't have those buggers at Brazeneck going one better than us!" (M. Ridcully)- Ponder moved towards his ultimate goal, a GBT (Great Big Thing.) By the time of The Science of Discworld IV: Judgement Day, Ponder has succeeded in getting his GBT up and running.
This is barely described, except that it is switched on by pulling a big red lever. The machine is also described as coruscating gently in the air. On its first usage, it drags a librarian out of Roundworld and into the Discworld.
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The EBT has now, almost literally, been built. A joint European initiative has seen the world's largest astronomical telescope complex being built, to take advantage of unspoilt South American skies, in Chile. its given name: the European Extremely Large Telescope.
A Danish cartoonist's viewpoint: