Layperson's description of the James Webb Space Telescope

[Kiwi]

Manawatu Standard,  Wednesday 5 June 2024. page 11
Opinion – Pondering the mysteries of the universe
Joe Bennett

   On Boxing Day 2021 Nasa launched the James Webb Space Telescope into space. I read about it at the time, boggled at the technology and wrote about it. But having read, boggled and written, I forgot it.
   Unsurprisingly, however, Nasa didn't forget their baby, and now 30 months later it's back in the news and I'm boggling at it all over again. A few of the facts are worth repeating.
   After launch the telescope travelled 1.6 million kilometres or so away from Earth at a speed of 4800kph until it reached a place in space known as Lagrange Point 2. This is one of only five points in the solar system where the gravitational pull of the sun and the gravitational pull of the earth cancel each other out. Thus a telescope parked at a Lagrange Point will remain orbiting in the same position relative to both objects and will barely need to expend fuel. How the good people at NASA calculated the Lagrange Point, and how they managed to steer a telescope to it and park it, I cannot begin to guess.
   Equally boggling is the device itself. As it travelled towards its destination, it unfurled a parasol the size of a tennis court, consisting of five separate layers of a substance called kapton. The combined thickness of the five layers of kapton is less than a quarter of a millimetre.
   The telescope is so oriented that the parasol always comes between the sun and the complex electronics that need to be kept seriously cool. The result is that the sunny side of the parasol is hot enough to fry an egg, while the temperature on the shaded side never exceeds -230 degrees Celsius.
   The heart of the telescope is a mirror 6.5 metres across made up of 18 hexagons of gold-plated beryllium. Its mission is to look further back into space and time than its famous predecessor, the Hubble. To this end it has now formed images of a galaxy called JADES-GS-z14-0, which is so far away that the light from it has been travelling (at the speed of light, obviously) for 13.5 billion years. In other words the telescope is viewing light that was emitted only 300m years after the universe came into being in the Big Bang.
   And all that light is infra-red because, throughout those 13.5 billion years, the universe has been expanding, and this has caused the wavelength of the light to stretch.
   At which point it is time to confess that my recitation of these scientific facts is no better than Polly the Parrot telling us she's pretty. Neither Polly nor I understand what we're saying. I don't understand what it means to stretch the wavelength of light. I don't understand the Big Bang. And though I've several times tried to read simplified versions of the Theory of Relativity, I still don't understand the relationship between time and space.
   My more honest voice is simply one of bogglement, and it has questions for the James Webb Space Telescope. They may be idiot questions but they are genuine.
   If space is effectively nothing, how can it be expanding? And if it is expanding, what is it expanding into? And if the answer is nothing, how does that nothing differ from the nothing that is space? In short, I suppose I'm asking where the universe is. And I'm also asking, with no less a sense of gawping wonder, how it is possible for a nation that is capable of the scientific, technological and intellectual sophistication that is the James Webb Telescope, to be considering re-electing Donald Trump.
   Joe Bennett is an award-winning Lyttelton-based writer, columnist and playwright.

[smartcooky]

...and all that light is infra-red because, throughout those 13.5 billion years, the universe has been expanding, and this has caused the wavelength of the light to stretch.
   At which point it is time to confess that my recitation of these scientific facts is no better than Polly the Parrot telling us she's pretty. Neither Polly nor I understand what we're saying. I don't understand what it means to stretch the wavelength of light.

Its not that hard a concept to grasp. You can think of it like sound.

You are probably familiar with the Doppler effect. An example is, you see an aircraft fly past you, and as it passes you, the pitch of the engine note seems to fall. This is caused by the fact that the sound wavefronts arrive to you more closely spaced (compressed), i.e. more frequently, meaning it sounds like a higher frequency,  and as the aircraft flies away, the sound wavefronts arrive to further apart (stretched out) i.e. less frequently so the pitch sounds lower.

Now if the aircraft is moving away from you, and you know the actual pitch (frequency) of the engine when it was at its closest point to you, and you could measure the frequency you are hearing, you could calculate the speed of the aircraft. This is what traffic cops' radar guns do at radio frequencies.

Further,  if the aircraft is accelerating away from you, and you measure and calculate the rate of the falling pitch, you could calculate the rate the aircraft is accelerating.

Now apply this to light - when an object is approaching, the light wavefronts arrive more closely spaced (compressed), their frequency is higher, and the blue end of the spectrum is the higher frequency end so the light is said to be "Blue Shifted". If the object is receding, the light wavefronts arrive less closely spaced, (stretched out), their frequency is lower and the red end of the spectrum is the lower frequency end so the light is said to be "Red Shifted"

The faster an object is traveling, the lower the frequency of the light we see from it. If the object has accelerate to a high enough velocity, the frequency could fall so low (the wavefronts are stretched out so far) that the object is red shifted beyond the range of human vision, into the infra red - and so we need an infra red telescope to see them.