The race to build the largest telescope in the world has galvanised astronomers on both sides of the Atlantic, writes Steve Farrar.
Rival European teams have joined forces in a unified bid to create a giant eye - with European Union funding - that could search the heavens for extraterrestrial life and locate the universe's first star.
The project will draw on a decade of work, including a proposal to build a giant instrument called Owl - the overwhelmingly large telescope - with a primary mirror 100m in diameter.
This would involve more glass than all the telescopes in the history of astronomy put together, according to Adrian Russell, director of the UK astronomy technology centre.
The more advanced of the two US projects is called Celt - the Californian extremely large telescope - and has a more modest target of 30m, almost three times the size of the 11m Hobby-Eberly.
Astronomers were to discuss their plans at a scientific conference in London today while the European project's steering committee will have its first meeting in Munich on Monday.
Gerry Gilmore, professor of astronomy at Cambridge University and chairman of the committee, described the existing European telescope designs as "straw men" and said a wholly new one was likely.
This would have to be at least 60m to 70m to enable the telescope to look for the chemical signature of life on earth-like planets in distant solar systems and scour remote galaxies for pure hydrogen stars, the first objects to have formed in the cosmos.
The technical challenge was to keep costs down, which could involve innovations such as mass-producing elements of a mosaic spherical mirror.
Professor Gilmore said the project would go ahead - "the astronomical community would riot if it didn't" - and that the level of funding would determine when.
Richard Ellis, a leading member of the Celt team who will address today's meeting, described Owl as "astonishingly ambitious and outrageously expensive".
He added that the Californian project's conceptual design was finished and there had been progress in raising private and public funds towards the $700 million (£445 million) cost.
But despite the rivalry, both projects hold out the possibility of a global project.
Dr Ellis asked: "Can the world afford two of these?"