Forty million hours, thousands of scientists, 30 years of planning, $10bn, one fiery rocket launchThe launch was originally planned for 2007, but has been continuously delayed. and the hopes and dreams of an entire generation.

It all comes down to a single moment.

The James Webb Space Telescope, the world's most powerful telescope ever made, set off attached to an Ariane rocket from the Kourou spaceport in French Guiana at 12.20pm on Christmas Day.

For astronomers, it is a nerve wracking time. This is no ordinary telescopeA device which makes things look nearer than they are. . It is so big its mirrors can only open fully once the rocket has left the ground, unfolding slowly over a month in a complex feat of giant origami.

There are an astonishing 344 "single point failures". Each decisive moment must happen at the right time, in the right order, to avoid disaster. If something goes wrong, nobody can travel one million miles past the moon to fix it.

"I will almost certainly be terrified the entire time," says one physicist. "You work for years and it all goes up in a puff of smoke," adds another. 

Yet if everything goes according to plan, the James Webb Space Telescope will be one of the most remarkable triumphs of human ingenuity the universe has ever seen.

Its predecessor, the Hubble Space Telescope, taught us the age of the universe, the rate of its expansion and how black holes anchor nearly every major galaxy.

But the JWST is bigger, more complex, more powerful and more audaciousBold. than the Hubble. Its infraredA type of electromagnetic radiation (a wave with electricity). The wave is longer than light which humans can see and shorter than microwaves. cameras can look deeper into space, further back in time and uncover, for the first time, the invisibleSomething that cannot be seen. .

"Remarkable enduring achievements of human hand and mind, be it the temples of Mahabalipuram, the pyramids of Giza, the Great Wall or the Sistine Chapel have all taken time and expense," says astrophysicist Dr Priyamvada Natarajan. "I truly see JWST as one such monument of our times."

When the images arrive in 2022, they could revolutionise our understanding of the universe. It is one of science's fundamental questions: where do we come from? Astronomers hope JWST will detect signals from 13 billion years ago and tell us how the cosmic dark ages ended. 

But JWST could reveal more than just the secrets of the early universe. The potential for discovery is enormous. Researchers around the world are preparing to peer into the atmospheres of exoplanetsThe name given to any planets that exist outside the solar system.. Each group has a different target, from Hot JupiterHot Jupiters are gas giant exoplanets that are very close to their host stars. WASP-18b to TRAPPIST-1e, one of seven exoplanets orbiting an ultracool dwarf star.

The world is waiting for a eureka moment. There are thousands of exoplanets in the universe. To indicate for the first time that we are not alone, only one needs to show signs of life.

"We all want to find another Earth," declares astronomer Kevin Stevenson. "The prospect of answering the question 'are we alone?' has been something that we've been asking ourselves for centuries. And I think with James Webb, this will provide us the first opportunity to really answer that question."

Definitely, say some. The JWST is one of the most daring acts of exploration in the whole of history. This is our best chance yet to find the answers we have been looking for. The idea of aliens is no more preposterous than the idea of humanity. Do not dismiss the possibility we may find them. 

Of course not, say others. There is no doubt, the telescope is a thrilling achievement. If it works, its discoveries will be extraordinary - but it will not find aliens. There is no need for sensationalism. We do not need to find aliens to fundamentally rethink our understanding of the universe.