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From what I understand, no - it’s not optical in that sense. The sensors just creep into the red and orange parts of the spectrum but it’s mostly all about the infra-red observations.
** The Official Space Flight Thread - The Space Station and Beyond **
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From what I understand, no - it’s not optical in that sense. The sensors just creep into the red and orange parts of the spectrum but it’s mostly all about the infra-red observations.
Man of Honour
Fully understand the light thing, but why wouldn't we feel the gravitational effects?
Associate
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Gravity travels at the speed of light - it’s how gravitational waves work. If the Sun disappeared, it’s effect on space time would disappear in a sphere radiating outward at the speed of light, and earth would continue on its orbit quite happily till the point the wave hit, at which point it would slingshot off in a straight line at a tangent like a hammer throw…
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Soldato
As we’re talking of the subject of seeing the edge, or very close to the edge, of the universe. Maybe someone can answer or point me in the right direction to something I’ve never managed to wrap my head around.
Which is how can we see the beginning of the universe? 10 years ago we could see back to 1 second after the big bang, now we can see 0.0000001 second after it. The figures aren’t correct but they make the point, the light from the big bang can only “pass” us once so how can we see earlier light?
Or put another way, when the first stars were born the light from them passed us, for examples sake, 20 years ago. If we were looking 20 years ago we’d see the star light up but today we can only see that star as it was when it was 20 years old. Yet with the ‘edge’ of the universe, as we’ve built better telescopes, we’ve been able to see further back in time.
Which is how can we see the beginning of the universe? 10 years ago we could see back to 1 second after the big bang, now we can see 0.0000001 second after it. The figures aren’t correct but they make the point, the light from the big bang can only “pass” us once so how can we see earlier light?
Or put another way, when the first stars were born the light from them passed us, for examples sake, 20 years ago. If we were looking 20 years ago we’d see the star light up but today we can only see that star as it was when it was 20 years old. Yet with the ‘edge’ of the universe, as we’ve built better telescopes, we’ve been able to see further back in time.
Soldato
As I understand the current theories of the big bang, what we see isn't one singular point of a big explosion. By the time things cooled and matter as we know it became possible, what see is a product of expansion and time.
If I understand correctly, what we learned since sending up hubble has given the scientists a better idea of what they are looking for, so they have been able to design JWST to provide a better more sensitive instruments, tuned to pick up different frequencies, allowing them to see a little further in time/distance.
Isn't it the case that the light from the furthest point hasn't reached us yet so we need to meet it first
Soldato
Well it's time for the sun shield to start unfurling. I know there are more failure points coming up but surely this step is the most complex?
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Yeah, space is difficult. I have no science qualifications beyond high school, so take what I say as a nerd with a pinch of salt and feel free to fact check it, but my understanding is this:
The Big Bang happened everywhere - it is still happening. The light from all parts of it is travelling in all directions at all times, it’s just the wavelength and intensity of it that changes the further it travels. The fainter an object you want to see, the longer you need to collect the light, hence the Hubble Deep Field taking about 10 days. The further away you want to look, the longer the light has been travelling and the longer wavelength it has due to expansion, so you have to look into the infra-red, hence JWST.
Otherwise, try Scott Manly…
Soldato
So next step is sun shield tensioning. Fingers crossed none of them tear!
Soldato
I love footage like this. Amazing how far and quickly the exhaust plume expands in the near vacuum of the top of the atmosphere when there is virtually nothing to slow it down compared to the atmosphere proper.
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All in one shot.
It is hard to get your head around, but it's mainly to do with inflation of the early universe which created the vast (infinite?) size of the universe already in a blink of an eye, before matter even came into existence and the subsequent expanansion that has gone on ever since.
Think of say the Sun and Alpha Centauria, our nearest star. When you see the light from the Sun it's from 8 minutes ago but when you see the light from A.C. its from 4.3 years ago since it's much further away and as such is dimmer than our star. So in a way we are looking back in time, as those stars were 8 mins and 4.3 years ago. It doesn't mean we could use a powerful telescope and look at the Sun as it was yesterday or A.C as it was 20 years ago, you are right in saying we are just seeing the current stream of photons as they reach the earth, right now. The ones from yesterday or 20 years ago have passed us by.
It's just with the size of the universe after inflation, and the expansion of space/time since, there is light from the early galaxies that were so far away already that their light really has just taken that long to reach us. The problem is, it is so faint (a few photons) and so stretched out in it's wavelength (due to expansion) that we haven't had a telescope sensitive enough to pick it up before, now hopefully we can.
So this is what's called the observable universe, the sphere around us of stuff whose light so far has taken the 13.8 billion years worth of time the universe has been around to get here. There will be objects even further away where the light still hasn't reach us yet. So that 'edge' of the observable universe does move outwards - by respect of the objects being further away and thus further back in time when the light was first emitted. So when we say looking back in time that's just a function of seeing objects that are further away.
In this example, no, if we were looking at the point of space where the star formed 20 years ago there would be nothing there (well, apart from the gas cloud of course!) we wouldn't see it light up until 20 years later, so we are looking back in time to how it was 20 years ago, even though it only lit up for us today.
This was supposed to be a quick post to try and help, it makes you realise there's no easy way to explain it
An article here probably does a better job than me! http://curious.astro.cornell.edu/ab...3-billion-years-ago-not-passed-us-by-beginner
the end summary
Soldato
More sunshield stuff happening just now
Soldato
Well that seems to be the most complex part done and hopefully the mirror will go smoothly. Fingers crossed.
Soldato
They Live! Can't wait to see if this actually works.
Soldato
It'll be a very expensive mistake if it doesn't work, I'm sure the boffins at engineering have been simulating it for months and double/triple checking the stresses it would endure during take off and landing.
Caporegime
Elon discussed it in a recent podcast with Lex Fridman, worth a listen.
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The way Starship has been landing on it's few actual flights so far they'll be lucky if it doesn't annihilate the entire tower on it's first trip. It's such a massive white elephant...
Soldato
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Really? They seem to know what they are doing, I mean they have built working test vessels in pronto quick time, developed some of the most efficient and powerful engines in the World have over 100 recoveries of first stage boosters after orbital flights. They are practically setting the bar for rapid spece technology development. I'm more inclined to bet on them than against them I find it hard to believe given the testing they've done it will blow up before it has adequately cleared the tower. I'm not under any expectations that the thing won't disintergrate later in the flight as they have no baseline testing for the reentry portions with this design. But the engines and pressure vessels are likely to be relaible enough to take off ok.
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Amazing what you can do with infinite money and zero accountability to government and taxpayers... Falcon 9 is an amazing bit of kit, and has made commercial space travel a reality - all credit to the engineers and brains behind SpaceX (not Musk, he's just a salesman with a load of money)
Starship, however, is just a massive white elephant in my opinion. It's managed to just about get to 10km a few times, yet everyone is still going on about it going to Mars and beyond which I just don't get. I will quite happily believe it'll clear the tower, but the idea of those massive arms grabbing hold of the thing on landing is comical, and I shall eat my hat if it happens in the next 2 years. Maybe I'll be proved wrong, and I'm happy to be, but right now I just don't see Starship as anything more than an endless chunk of money being burned.