By Jonathan Amos.
The science correspondent of the British Broadcasting Corporation.
P.Horlek is an astronomer.
There is darkness. Total and complete. Few of us get to see it.
At the bottom of a cave, or in a basement when the power goes off. There is usually a faint glow coming from somewhere. The night sky never seems black because there are usually stars in the distance.
It's hard to imagine a time when you could travel in any direction for millions of years and still not see anything.
The story that scientists tell us is that of the "dark ages" that gripped the Universe before the first stars. They intend to show us how the universe ended, or rather how it began.
The biggest telescope ever placed beyond the Earth will be used to do it.
Launching in the next few days, the JWST is on a mission to look deeper into the Universe than the Hubble Space Telescope can.
NASA.
The mirror is made from gold and beryllium.
A mirror and four super-sensitive instruments will allow him to look for light that has been travelling through space for more than 13 billion years.
"They will be little red specks," says John Mather, a senior project scientist at the JWST.
We think there should be stars or black holes after the Big bang. The researcher from the US space agency says that there won't be many of them to find at that time, but the telescope can see them if they are there.
You might still be able to see it. Light has a finite speed in a large and expanding universe. You should eventually get to retrieve the light from the pioneer stars as they group together into the first galaxies if you keep probing deeper.
For what purpose? 10 years of conception and another 20 years of building a $10 billion machine to detect faint red blobs on the sky is not worth it.
The most fundamental questions are: Where do we come from?
The Universe was formed in the Big bang with only hydrogen, helium and a small amount of lithium. Nothing else.
The chemical elements in the Periodic Table were forged in stars. All the carbon that makes up living things; all the nitrogen in Earth's atmosphere; and all the Silicon in rocks had to be "manufactured" in the nuclear reactions that make stars shine.
The Universe is only here because the first stars and their descendants created it.
"Webb's mission is about the formation of all likeness; it's the 'we're all made of stardust' argument," says Rebecca Bowler, a University of Manchester astronomer.
The first carbon atom was formed. It's amazing that we could observe that process in progress.
We don't know a lot about the first stars. The laws of physics can be put into computer models to see what might happen. It sounds like fiction.
"Estimates range from 100 to 1000 times the mass of our Sun," says Rieke. All stars follow the rule that the length of time they can exist as a star is proportional to their mass, meaning that the more massive a star, the faster it uses up its fuel. The early stars might have only lasted a million years.
Live fast and die young. Our own Sun is timid in comparison. It has burned for nearly five billion years and will probably burn for another five.
Hubble took us on an amazing journey.
The search for the first starlight makes the sound of a flute. It's not anything but.
It will observe everything that can be seen out there beyond Earth, from the icy moons and comets in our own Solar System to the huge black holes that seem to reside at the core of all galaxies. It should be able to study planets around other suns.
In order to look at all of its targets in a specific way, it has been tuning.
Hubble was designed to be sensitive to light in the visible wavelength. That's the same type of light we see.
Although invisible to our eyes, the longer wavelength of the telescope is where the glow from the most distant objects in the Universe will show up.
The starlight is stretched by the expansion of the Universe. Richard Ellis, an astronomer at the University College London, calls it redshift.
Hubble doesn't reach far enough into theIR to detect the starlight signal we want. It is not a large telescope. It's been a pioneer. The pictures are amazing. The power of a telescope scales with the square of the mirror's diameter. That's where the JWST comes in.
William Herschel was the astronomer who discovered the IR. The production of telescope mirrors was changed by him.
The polishing machines he used could achieve a smooth reflecting surface on a disc made from tin and copper.
The innovation that went into producing the mirrors would have been appreciated by Herschel.
They're made from a metal that's light-weight and has a nice shape. There's a gold coating. It's extremely thin, just a few hundred atoms thick, but this addition turns the mirrors into near- perfect reflectors.
The emission from distant stars experiences minimal loses when the incident light is bounced back.
Anyone who has seen the telescope's primary mirror will attest to its quality. Those who have worked on it for two decades never tire of its beauty.
Lee Feinberg, who's led the Webb mirror team, recalls a time when the mirror was pointed downwards and he had to climb under it to inspect the optics.
I was in my bunny suit, looking up at all the gold surfaces, and seeing myself reflected back. It was amazing, all the surfaces were focused on me. I had a feeling of being at the center of it all.
The primary mirror of Hubble had a problem.
The telescope arrived in 1990 and scientists realized the reflector wasn't polished correctly. The pictures of the stars were blurry.
It wasn't until astronauts were able to fix Hubble that he started to see the universe in a better light. It's because of that experience that people ask if the mirror can be perfect.
Your device might not support this visualization.
In August of last year, Hurricane Harvey dumped 127 billion tonnes of rain on Texas.
In the midst of that deluge, the space shuttle was undergoing critical testing at the Johnson Space Center in Houston, which would prove it was fit to fly.
The rule over Apollo hardware and even space-suited astronauts was put in the space simulator that was used in the 1960s.
The telescope was able to be swallowed whole by Chamber A, which is gargantuan in volume. The purpose of the three-month test was to see if all the mirrors would focus on the same area.
It would allow the teams working on the instruments to see how their systems performed in off-world conditions. Hurricane Harvey would oblige.
Chris Gunn is from NASA.
The Apollo chamber was used for a taste of what it will be like to operate in space.
The computer consoles were covered in plastic to protect them from the risk of water dripping from the ceiling. Behind the thick walls of the vacuum vessel was where it was hidden, and it showed it didn't have a "Hubble problem".
Lee Feinberg says that the segments on the primary mirror have a mechanism that allows them to be moved around. When they are first deployed in space, they will be different. All those actuators will take us from a misalignment measured in millimetres to just a few hundredths of a millimeter. A million improvement.
The 18 segments will behave as if they're a single mirror.
Begoa Vila says that they demonstrated this in the test chamber. When we first look at a star in space, we'll see 18 different spots of light because the mirror segments won't be aligned. We'll adjust the mirrors to make a single star that's not aberrated and good for normal operations. We know that he works.
The technologies on James Webb took a long time to develop.
A woman is carrying something.
This isn't some old Tupperware; it's space-qualified Tupperware. The director of the UK Astronomy Technology Centre says that it meets all the international standards for keeping things clean.
If you want to understand why it took so long to build, you need to look in the plastic box of Gillian.
She and her colleagues have built a spare mirror from the Mid-Infrared Instrument (MIRI) for the telescope.
It looks like a mini musical accordion made for a doll and is about the size of a 50-pence piece. The little mirror is covered in gold again.
The arrangement allows the mirror to acquire both an image of the sky and a light source, such as a black hole, and then send that light into a telescope. The chemistry, temperature, density and velocity of the targets will be revealed by this device.
At every point in the image, at the same time. She tells me that a data cube is what she calls a 2D to 3D conversion.
NASA.
The Apollo Moon-landings project was implemented by James E. Webb.
This was a novel one for the man. The level of engineering precision required was very challenging. The steps had to be carefully made so that the light from different parts of the world wouldn't ruin the data.
It took a year for the space agencies to convince them that the slicing mirrors would meet the specifications. This is a small part of a giant telescope.
Every element had to be tested and then tested again when joined to another element. The edifice was made up of dolls.
"Because it's such a big and complex observatory, and also because it has to work at cryogenic temperatures, you can't just put everything together at once, and then test it," says Mark Clampin, a former Nasa project scientist. You put everything into sealed, isolated packages, starting with the smallest pieces and testing at every stage. It becomes almost impossible to go back because you found a problem with the detector, as things get bigger and bigger.
They realized one of the slicing mirrors was malfunctioning at the end of the telescope's construction.
It would be a nightmare to disassemble the observatory to get to the sub-standard part.
Chris Gunn is from NASA.
The nosecone of the launch rocket has to be folded to fit James Webb.
Mark McCaughrean has worked on the project for 23 years in an advisory capacity for the European Space Agency. He's seen bits and pieces of the observatory before, but just weeks before the expected launch, he's getting the chance to examine the completed observatory for the first time.
I don't know what to say. It's amazing. There is emotion in his voice.
The insulation blankets are made of gold and silver. The purple tint to the latter colour is slight. The size of a single decker bus is what we're seeing in the folded configuration of Webb.
This bus has been put in the nosecone of the Ariane launch rocket.
Mark says that it has an amazing scale. Wouldn't it be great to see a bird in space?
The naysayers have had to fight through the development of the project. They would say it was too complex. It's kind of scary that the telescope must complete a sequence of deployment in order to begin its observations.
If the actions don't occur on cue and in the right order, they are likely to ruin the whole undertaking. The decisive hurdles must be overcome by Webb.
The deployment of a solar panel and radio antenna should be very straightforward.
The opening of the primary mirror's wings should be considered a standard operation. The unfurling of the tennis court-sized shield that will protect it from the glare of the Sun was the focus of the actions.
The key hardware includes 140 release mechanisms, 70 hinge assembly, eight deployment motors, bearings, springs, gears, and 400 pulleys.
We did multiple deployment testing on both small and full-size models to perfect the sequence. We practiced both the deployment and the process of hiding. This gives us the confidence that we are going to deploy successfully.
The telescope is important because it is exciting, says an astronomer on the team.
The whole process looks frightening for those of us who haven't been involved. If one of the cords pulls on the super-thin membranes, what would happen?
The calming voice is John Mather. He has been on the project for many years.
"I'm confident, but I'm also aware that bad things can still happen even if we have a good plan," he says. My opinion does not affect the hardware. My worry has no effect on the hardware. I mostly don't worry.
NASA/ESA.
The old telescope looks like a very solid investment given all that Hubble has shown us.
I left the topic until the last moment, but it can't pass without a comment. The price.
Everyone quotes a figure of $10 billion. It covers the 20-year build period, the launch and five years of operations in space.
It's eye-watering as a cold number. Hubble was also very expensive. The observatory cost more than $7 billion by the time it was repaired. It must be close to that now.
The old telescope seems to be a good value since Hubble has shown us about the Universe.
Chris Gunn is from NASA.
The price of a cup of coffee in Europe has been equal to the cost of a cup of Webb.
Who will quibble about cost if we see our atomic origins?
Peter Jensen, a former European Space Agency project manager, says that Europe has spent 700m on James Webb.
It comes down to a cheap cup of coffee in a cheap café, drunk over a period of 20 years, as a cost per inhabitant in Europe.
