When Hubble stared at nothing for 100 hours (2015)

https://www.nationalgeographic.com/science/phenomena/2015/04/24/when-hubble-stared-at-nothing-for-100-hours/

by hwayne • 6 years ago

611 224 6 years ago

This and the later XDF (eXtreme Deep Field) surveys still raise the hairs on the back of my neck every time I look at them. It really puts our human scale and importance in perspective.

coldcode• 6 years ago

It's hard to imagine that the tiniest pixel spec of a galaxy hold hundreds of millions or more of stars like our own which might have planets with people on them. Of course they might also be 12B years gone.

dghughes2• 6 years ago

It really puts our human scale and importance in perspective.

Speaking of scale a new large structure was discovered a supercluster which has been named "South Pole Wall" it;s 1.5 billion light years in length.

https://www.youtube.com/watch?v=lnUUKJMAmFo

machello13• 6 years ago

https://en.wikipedia.org/wiki/South_Pole_Wall for anyone else who prefers reading to watching videos.

caiobegotti• 6 years ago

This almost makes me dizzy: https://en.wikipedia.org/wiki/Hubble_Ultra-Deep_Field#/media... (it's a picture of the night sky showing what exactly Hubble was imaging with the Moon for scale)

I never really understood how XDF is only that tiny patch of the sky and yet it has a godzillion of galaxies inside it!

ctdonath• 6 years ago

TIL: Moon covers 0.5°.

mkl2• 6 years ago

The full resolution versions of the public domain images from the article are on that page: https://en.wikipedia.org/wiki/Hubble_Ultra-Deep_Field

Unlike the lower resolution versions National Graphic scoldingly claims are under copyright when you right click to try and view the full image.

MengerSponge• 6 years ago

If you haven't yet, you should read Vonnegut's short story "The Euphio Question", which was written well in advance of deep field, but is eerily complementary.

Ma8ee7• 6 years ago

Just imagining the interstellar space does it for me. Our planet is a marble in a cathedral compared to the solar system, and between stars not even a speck of sand.

guerrilla• 6 years ago

I don't know of anything more awesome (in the literal sense of the word) than these photos. It makes my wonder just how densely packed (ignoring variation in distance) the area is. What will we see when we start looking between those dark spots? What if there's literally something in every direction...

gizmo6863• 6 years ago

Before our modern understanding of cosmology, a serious question astromers asked is "why is the night sky dark". If there truly were stars/galaxies in every direction you would expect the entire night sky to be bright, as no matter which way you looked you would see a star; and the combined light of all of those stars should illuminate the sky.

As it turns out, empty space isn't dark, but rather illuminated by the cosmic microwave background. This suggests that the space between us and this boundary in space from when photons started to be able to move mostly freely is mostly empty. Otherwise this backround would either be over-shadowed by stars, or obscured by whatever stuff was obscuring said stars.

Of course, it is important to keep in mind the speed of light implications.

philiplu• 6 years ago

For more on this, see Olbers’ paradox - https://en.wikipedia.org/wiki/Olbers%27_paradox

teh_klev• 6 years ago

See also Olber's Paradox:

https://en.wikipedia.org/wiki/Olbers%27_paradox

nabilhat• 6 years ago

In 1995, astronomer Bob Williams wanted to point the Hubble Space Telescope at a patch of sky filled with absolutely nothing remarkable. For 100 hours.

It was a terrible idea, his colleagues told him, and a waste of valuable telescope time. People would kill for that amount of time with the sharpest tool in the shed

And by 'Bob Williams', we mean the director of the Space Telescope Science Institute, which operates Hubble. Williams chose to use some of the predefined Director's Discretionary Time to explore the limits of the telescope and our understanding of the universe.

https://en.wikipedia.org/wiki/Robert_Williams_(astronomer)

JamesLeonis2• 6 years ago

I adore these images, and deeply respect the reputation risk in getting them.

I also believe that even if we found nothing at all, it would still advance our understanding of the universe as we could confidently say what limits there might be.

stingraycharles2• 6 years ago

Unfortunately people would not have gotten nearly as excited when seeing nothing, and the nay-sayers would have made this very clear.

These things are always as much science as they are politics, so the reputation damage would have been real.

soneil• 6 years ago

I think it's not so much that it was a huge gamble. It was more that it was a sensitive time politically, to make that gamble.

I mean, if they found nothing? Sure, that's still a question Hubble should be trying to answer. But right after such a rocky start, the politically obvious choice would have been to go for easy wins.

The timing was as ballsy as anything else, if not more so.

hawski• 6 years ago

From the article:

And, to be honest, it didn’t really matter how much his colleagues protested. As director of the Space Telescope Science Institute, he had a certain amount of Hubble’s time at his personal disposal. “The telescope allocation committee would never have approved such a long, risky project,” he explains. “But as director, I had 10 percent of the telescope time, and I could do what I wanted.”

Also:

“Scientific discovery requires risk,” Williams says. “And I was at a point in my career where I said, “If it’s that bad, I’ll resign. I‘ll fall on my sword.’”

supernova87a• 6 years ago

Well, my opinion (now) is that it wasn't so huge a gamble and completely unknown. The galaxy luminosity function (# galaxies per brightness, basically for those unfamiliar) is a curve they knew the beginnings of through images to date, and it wasn't unreasonable to suppose it would keep going beyond what had been done.

It's not like you would expect galaxies to suddenly stop being found if you took exposures a little deeper. It was a good (and not outrageous) bet. I would liken it to -- if we built a better microscope and looked deeper into a cell, is it likely we'd find nothing new? Probably not.

qwertox• 6 years ago

10% is a remarkable amount of time. I was astonished when I read that number. I would have expected it to be around 1% at max.

jostmey• 6 years ago

Wow! The culture sounds very risk averse. I mean 100 hours is not much given how long the telescope remained opertional

dheera• 6 years ago

Exactly, this is exactly why I decided not to pursue academia.

Too many times I heard things along the lines of getting "low hanging fruit" to get "published" and that "don't try that you won't ever graduate". Why is graduating and publishing papers and tenure and theses the goal of academia, instead of trying the highest possible risk things that even companies wouldn't want to risk? Why isn't academia about doing the most utterly crazy things possible in the name of advancing science for civilization?

klyrs2• 6 years ago

Imagine the world had a single supercomputer, and somebody wanted 100% utilization for those hundred hours to, say, train a neural net to play donkey kong. It's not a huge cost, given the expected lifetime of the resource, but to everybody else waiting in the queue, it would be quite the opportunity cost.

dredmorbius• 6 years ago

This is increasingly common across numerous fields. Certainly in academia, but also in corporate R&D, investing, venture capital, military procurement, etc.

Novel trials are big risks, are institutional (or worse, multi-institutional), and searcch spaces are large, well-picked-over, and huge gains improbabble. Though aversion to novelty is a long-standing behaviour, see "Resistances to the Adoption of Technological Innovations", by Bernhard J. Stern (1937):

https://archive.org/details/technologicaltre1937unitrich/pag...

Markdown https://pastebin.com/raw/Bapu75is

RedOrGreen2• 6 years ago

HST is in a 96-minute orbit, up to half of which is blocked by the Earth, depending on where in the sky you point it. Getting time on it is an extremely competitive process - the recent cycle had over a thousand proposals, requesting over 24,000 orbits worth of observing time, and they had only 2700 orbits to allocate [1].

This sort of proposal pressure (over 9:1 oversubscription) leads to very conservative proposals, where we request absolute minimums and emphasize that even a non-detection will lead to publishable science in such and such a way.

Getting over 60 orbits to point at a blank field would have been frankly impossible through the regular time allocation process, not because the science wasn't excellent, not because it wouldn't be recognized as excellent, but because it would crowd out other science that could be done with far fewer orbits per project.

The telescope administrators explicitly recognized this problem when they set up the Director's Discretionary Time process (and this is common to all telescopes now) - sometimes you need someone with the authority to just roll the dice on a long shot.

[1] https://www.stsci.edu/contents/newsletters/2019-volume-36-is...

joncp• 6 years ago

For me, those images are a sliver of the Total Perspective Vortex. The more I try to comprehend them the more blown away I am by them.

brutt• 6 years ago

doctoboggan• 6 years ago

I remember the first time I saw the deep field image. It blew my mind then and still does today. I had no idea it was a controversial experiment at the time.

iamkroot• 6 years ago

I don't think anything else that I've seen or read has properly conveyed the scale of the universe the way these images do. They did and still do stagger my imagination.

frandroid• 6 years ago

If they knew what they'd capture, it wouldn't have been controversial, but they didn't. :P

hn_throwaway_99• 6 years ago

I have a sense that the article is presenting things in a more dramatic way than how it really occurred:

So, with his job perhaps on the line, Williams went off, put together a small team of post-docs, and did exactly as he’d planned. For 100 hours, between Dec. 18 and 28, Hubble stared at a patch of sky near the Big Dipper’s handle that was only about 1/30th as wide as the full moon. In total, the telescope took 342 pictures of the region, each of which was exposed for between 25 and 45 minutes. The images were processed and combined, then colored, and 17 days later, released to the public.

I mean, each image was only exposed for 25-45 minutes. If the full hundred hours was such a huge risk, why not take, like, 5-10 photos first to see if you get much of anything? Seems like they would have been able to know pretty early on whether it was going to be worth it.

ISL5• 6 years ago

I'm sure they did start stacking as soon as they got the images. From a statistical perspective, 100 hr is roughly 3x better than 10 hr.

spenczar5• 6 years ago

If they found nothing in the first 5-10 images, what do you imagine they would do? Telescope scheduling is a very tricky business, not one that lets you change courses too quickly.

MiroF• 6 years ago

Schedule the 5-10 mins, then schedule again for later.

pbhjpbhj• 6 years ago

This is a decent and sensible question IMO, barkingcat (downthread) provides a reasoned answer that seems to fit, but the question is good .. so why did the person feel the need to use a throwaway, and why is it downvoted. Unlike other questions it doesn't appear to be the sort of thing one ignorant of the answer could readily google for.

I know, we're not supposed to complain about downvotes but it just makes me sad that we - as a community - don't value honest questions.

RedOrGreen2• 6 years ago

If the full hundred hours was such a huge risk, why not take, like, 5-10 photos first to see if you get much of anything? Seems like they would have been able to know pretty early on whether it was going to be worth it.

This has been answered already but just to pull some threads together - the suggestion to take a few exposures first and see what comes out is precisely backwards. They already knew, going into it, that what they were looking for was at the limits of sensitivity, so nothing would show up until they accumulated enough observing time.

In the absence of systematic effects, our signal to noise ratio improves as the square root of integration time. Think of a bucket accumulating photons - the signal accumulates in linear proportion to the integration time, while the RMS fluctuations increase as the square root of the integration time, so the signal to noise ratio improves as T/sqrt(T) = sqrt(T).

So the idea was to accumulate enough exposure that the faint galaxies would become visible at the telescope performance limits - can't get to something scientifically useful by imaging only the first few exposures. It might have made a pretty enough picture, sure, but not an informative one, compared to what we could already do from huge ground-based facilities.

gen3• 6 years ago

The sheer scale on these photos is amazing. Seeing galaxies strewn around like marbles is very humbling.

I hope there are more plans for deep space photos. I wonder what a telescope on the other side of the moon could capture.

ISL5• 6 years ago

I'm sure it is on the list for JWST. I suspect Spitzer must have already attempted the same thing.

Being on the other side of the Moon, alone, isn't likely to make a huge difference in image depth.

gwern2• 6 years ago

And frightening. Such photos really bring home the Great Silence. All of those specks which are entire galaxies, and not the single slightest sign of intelligent life anywhere, ever. The marbles roll on just as they have for billions and billions of years and will go on rolling for billions to come, dead pieces of inert matter tracing out their gravitational trajectories and burning as predicted.

myself248• 6 years ago

Could I say that it's also hopeful in a way, that nobody more violent than us seems to have emerged?

krapp• 6 years ago

All of those specks which are entire galaxies, and not the single slightest sign of intelligent life anywhere, ever.

You say that as if we could tell with any certainty, at that scale. There could be interstellar civilizations spanning several of those galaxies and uncountable intelligent civilizations that simply never pursued space travel or the constant accelerated curve of energy consumption and colonization we assume they would, only because we ourselves would.

We wouldn't know, we don't even really know what we're looking for, and the universe is so vast that even if we did, we'd be all but certain to blink and miss it.

gregmac• 6 years ago

This is like being in a plane at cruising altitude, looking down at the ocean, and declaring there's zero signs of life, so the ocean must be dead.

graycat• 6 years ago

Assume we are starting with, IIRC, ballpark 14 billion years since the big bang.

Well, to get to life, we have to have chemical elements more than just the hydrogen, helium, and a little lithium that came directly from the big bang. So for carbon, oxygen, ..., iron, have to have some big stars form, burn, and explode.

So those galaxies from 12 billion years ago didn't have much time -- ballpark only 2 billion years -- to form the elements of the periodic table.

Coming at it from our end, IIRC our planet and solar system are about 5 billion years old.

Give it, after the big bang, 4 billion years to the periodic table and another 5 billion years for life. So, that's 9 billion years, 5 billion years ago.

So don't expect much in Little Green Men ET from more than 5 billion years ago.

Since we started 5 billion years ago, we are ballpark only second generation life in this universe.

Net, mostly what's in the Hubble deep field images is too old to have much in life (anything like ours). To have a shot at seeing life, don't look back more than ballpark 5 billion years.

Since stars are burning out and the universe is expanding, are we also about the last generation of life?

Yup, it's amazing to look back 12 billion years, to see galaxies already there, with quasars and, thus, likely supermassive black holes. Amazing to guess how such big black holes formed so soon. Lots more that's amazing. Still for life, only look back about 5 billion years.

Disclosure: I'm not an astronomer!

mensetmanusman4• 6 years ago

Even if we wanted to tell the universe we existed, it would take too much energy to shoot out a strong enough signal. We would have to eat the sun to do that :)

imhoguy3• 6 years ago

Other side of the Moon would impose unnecessary communication complexities without much optical benefit. Earth-Sun L2 point is much better because Earth's shadow blocks most of heat from the Sun, plus the probe needs heat shield only on one side to block remains of heat from Sun, Earth and Moon. See: https://en.wikipedia.org/wiki/James_Webb_Space_Telescope#Sun...

MAGZine• 6 years ago

building on the surface of the moon is not without benefit. as a static location, it would be much easier to build larger sensors with larger mirrors, rather than having to build one giant thing and hope it deploys safely. You could build an arbitrarily large-sized mirror. Or, you could build large radio telescopes that do not need to contest with the noise of the earth's atmosphere.

all spectra are important for astrological observations—there is a serious lack of radio observations made with large telescopes outside of the earth's atmosphere in particular.

NASA has funded an early study into the feasibility of building such a telescope. https://www.nasa.gov/directorates/spacetech/niac/2020_Phase_...

nickgrosvenor• 6 years ago

Best article I've read in a long long time.

thaumasiotes• 6 years ago

For 100 hours, between Dec. 18 and 28, Hubble stared at a patch of sky near the Big Dipper’s handle that was only about 1/30th as wide as the full moon. In total, the telescope took 342 pictures of the region, each of which was exposed for between 25 and 45 minutes.

How did this work? 342 pictures at 25 minutes each is already well over 100 hours. At 45 minutes, it'd be 256 hours.

ISL5• 6 years ago

Indeed, the math doesn't pencil out.

I don't know, but I'd hazard a guess that the image is 100 hr deep on multiple tiles.

The dataset spans 10 days, which is 240 hr.

MiguelHudnandez• 6 years ago

The telescope's orbital period and the relative positions of the earth and the sun will affect how the exposures are scheduled.

I went looking for more detailed information -- It appears they are open enough with the data that you can see exactly how the exposures were taken. Assuming what I found is right and that someone could make sense of the data. There are postscript files listing activity for each of the 10 days, but I am not exactly sure what we're looking at.

https://www.stsci.edu/ftp/science/hdf/project/project.html

azernik• 6 years ago

Possibly counting images using different sensors as separate exposures, even if they're taken during overlapping time intervals

tipsysquid• 6 years ago

Could it be 100hrs of night sky?

akarpenko2• 6 years ago

That makes no sense for a satellite in orbit around the earth outside of the atmosphere. It would never point at the sun. The only issue is that the earth would periodically occlude the area of observation.

hbosch• 6 years ago

The Hubble Telescope has multiple cameras and sensors.

annoyingnoob• 6 years ago

Ha! I just ordered a custom skate deck with these images on the bottom.

iliaznk3• 6 years ago

I'm sorry, I haven't read the article, maybe it's explained there, but as far as I understand by 100 hours they mean that the telescope was sitting there for 100 hours exposed open like a camera, right? How come the image is so sharp then? Wouldn't all those galaxies be constantly moving and end up blurred in a photo?

pryelluw• 6 years ago

From the article:

...In total, the telescope took 342 pictures of the region, each of which was exposed for between 25 and 45 minutes. The images were processed and combined, then colored, and 17 days later, released to the public.

iliaznk3• 6 years ago

Oh, that explains it, thanks a lot!

ben_w4• 6 years ago

Hubble is in space. They just pointed it somewhere and said “don’t move” (well, multiple times and stacked, but the effect is the same). The galaxies themselves are so far away their own motion is way less than a single pixel.

iliaznk3• 6 years ago

Good point. But still, I think, if it really was exposed for 100 hours the photo wouldn't be as sharp.

atonse2• 6 years ago

Yes but isn't Hubble moving? Or is it in a fixed position in space?

munificent2• 6 years ago

So there are two things you do to take very long "exposures" like this for astrophotography:

1. You put the telescope on a motorized mount that rotates the telescope exactly counter to the rotation of the Earth (or I guess its orbit in the case of Hubble). This cancels out most of the blurry star trails you get from the Earth's rotation causing the stars to move across your frame.

2. For particularly long exposures, you take a series of separate photos (each of which is probably done using step 1). Then you "stack" those in software by aligning all of the images to maximize their sharpsness. There is software that will do this for you automatically. Stacking helps correct for thermal noise and other imperfections and non-linearities that photon sensors have when collecting for a really long time.

It's a good question.

short_sells_poo• 6 years ago

"Bob was right, I was wrong. The use of that discretionary time was a courageous thing,"

This is such a powerful statement from Rob Kirschner. It is science at it's best. Someone (rightfully) opposing an experiment, being incorrect and admitting, without reluctance, shame or regrets that they were wrong.

At the time, Bob's idea was by all available information questionable. But it was right for him to persevere, it was right that he had to face and overcome opposition and it is right that the opposition gracefully admits that Bob was right :)

ape4• 6 years ago

"Bob was right" would be a good framed reminder

cmroanirgo• 6 years ago

As an Aussie, this hilariously augments a phrase used commonly here: "Bob's your uncle"

(meaning roughly: "and there it is" / "and there you have it")

Even more hilariously, I have an uncle Bob.

photonemitter• 6 years ago

Is "Praise Bob" still a thing?

cflyingdutchman• 6 years ago

This interview with Kirshner is a good read as well: https://www.aip.org/history-programs/niels-bohr-library/oral... And a reminder that science is not generally moved forward by strokes of brilliance, but by a whole bunch of people grinding at the fuzzy edge until the picture becomes a little more clear.

bashinator• 6 years ago

Spectacularly appropriate metaphor - thanks for that.

fnordprefect• 6 years ago

Great quote. Also unintentionally (I think) humorous, given the manufacturing problem with Hubble referred to in the article was slightly inaccurate grinding of the lens' edges.

draw_down• 6 years ago

I suppose; it's certainly better than stubbornly holding one's ground after one is proven wrong.

But I think the courage Bob showed in the first place is much more praiseworthy. He actually had to put his butt on the line for this, admitting someone was right after the fact does not usually require that.

jdxcode• 6 years ago

Reminds me of Malcolm Gladwell's "pull the goalie" podcast. https://medium.com/the-post-grad-survival-guide/lessons-for-...

ImaCake• 6 years ago

I think it's a good lesson to learn, in general, that intuition and popular choices are often wrong or at least sub optimal. But I suspect that the popular sub-optimal path is taken for pragmatic reasons. More specifically to teaching, I have recently being putting together lesson plans for coding/robotics workshops and I suspect part of the reason for a less experimental experience is that it is easier to plan than a less on-rails teaching experience. This makes me think that at least part of popular wisdom is simply that the sub-optimal popular choice might be good enough given insufficient resources to implement the truly optimal choice.

elboru• 6 years ago

Probably it’s a perspective issue, but galaxies look relatively close to each other, is that the case?

I mean they look relatively close compared to their size, in contrast our solar system’s bodies are really far away from each other (of course relatively).

tempestn• 6 years ago

Remember it's 3d; they're not arranged on a single plane.

nabla9• 6 years ago

Average distance between galaxies is 10-100 times the diameter of the average galaxies.

Andromeda for naked eye is a smudge six time bigger than the moon (3.0 degrees across).

depressedpanda• 6 years ago

I found it hard to believe that Andromeda would be six times larger in the night sky than the moon, so I searched online and discovered this article showing what the galaxy would look like if it were brighter: https://petapixel.com/2014/12/08/photos-night-sky-look-like-...

Wow. TIL.

Ma8ee7• 6 years ago

They are. Stars are of the order of thousands of star-diameters apart from each other, while galaxies are of the order tens of galaxy-diameters apart.

sigstoat• 6 years ago

Stars are of the order of thousands of star-diameters apart from each other

no. they're millions of star-diameters apart.

https://en.wikipedia.org/wiki/Solar_radius compare it to a light year. note that the nearest star is 4 something light years away. the average is about 5 ly.

while galaxies are of the order tens of galaxy-diameters apart.

i think that's low, but harder to define.

mkl2• 6 years ago

They are far apart because they are different distances away from us. E.g. two galaxies that look right next to each other in the image could be 5 billion and 6 billion light years away from us, which means 1 billion light years away from each other. Hover over the galaxies in the image here to see the distances (warning: makes sound): https://apod.nasa.gov/apod/ap180305.html

baxtr• 6 years ago

“With this achievement, the estimated number of galaxies in the universe had multiplied enormously — to 50 billion, five times more than previously expected,”

This numbers is sheer incredible. Each of them contains 50 billion stars. How come some think we’re alone in this universe?

EDIT: yeah, I know speed of light and all... it’s just a stupid fantasy that is fueled by these numbers

pixl972• 6 years ago

Well they are so far away we are for all practical reasons, alone. Suns will be born, die, reform from the ashes many times before a message at the speed of light could make a round trip. And that is to the ones at only a few billion light years away.

zhengyi13• 6 years ago

I just had this thought that, say, in prison, or a bad relationship, there could be a person in the room right next to yours, and there could be such a gulf between you that you are in fact completely and utterly alone.

... If there's no communication between you, what else would you call that but "alone"?

Edit: I should say that I think I hear what you're saying, and I further think that there's always hope that you could bridge that gap.

Ma8ee7• 6 years ago

I have this nagging thought that maybe intelligent life really is a coincidence of a grand cosmic scale. Maybe we really really are all alone in this galaxy and among many others. What an incredible opportunity we are given, and how we squander it with our bickering.

mensetmanusman4• 6 years ago

Lol, would love to know the thought process of someone that bothered to downvote you.

if you don’t believe aliens exist, you are wronggggg!!!

stordoff• 6 years ago

For some reason, something that's always stuck with me is my grandfather asking the priest at my school (it was a church school) "Do you think aliens exist?" and him replying "I'd be naïve to think they don't".

The sheer number of stars seems to make it likely we aren't alone. Whether we're practically alone, and will remain forever separated from our nearest intelligent neighbours, is a more interesting question IMO (though somehow discovering we are completely alone would be fascinating in its own right and raise further questions).

vlasev5• 6 years ago

Some galaxies have stars in the trillions. Even the Milky way is at something like quarter of a trillion. It's mind-boggling.

whoisjuan• 6 years ago

http://archive.is/5cgaD

archon810• 6 years ago

Thank you. It's incredibly obnoxious when a website says I have 3 free articles left to read this month and 10s later pops up a non-dismissable pop-up that forces registration.

dmalvarado2• 6 years ago

Since we seem to have a good discussion here, there's something I've always wanted to know.

If I understand correctly, the universe is approximately 13.8 billion years old. As is mentioned frequently when staring at deep space, we are looking at the universe not as it is, but as it was, since it takes so long for the light to travel to us. Some objects in the Hubble Deep Field are over 9 billion years old, and some within 1 billion years of the beginning of the universe.

My question, as best I am able to ask it, is assuming the big bang theory is true, how can it be that we on Earth can be looking at something simultaneously so old and so far away? If everything originated from the same point, how can it be that we pick an object in the sky and say "that is what the object looked like 12 billion years ago"? Doesn't it beg the question, "well then where were we 12 billion years ago?" As in, how can we be here, observing something close to the beginning of time? Didn't both objects start at the same place?

I hope that makes sense.. Articles and videos much appreciated

grumple• 6 years ago

https://medium.com/starts-with-a-bang/if-the-universe-is-13-...

4gotunameagain• 6 years ago

Imagine that it is the 17th century. We are both in London, and you tell me that you will be in Mumbai in six months. The same night, I write a letter to you, addressed to Mumbai. Six months later, both you and the letter arrive, and by opening it you are exposed to my mindset as it was six months ago.

Hope that helped a little bit..

wdbbdw• 6 years ago

I won't pretend to understand the answer well enough to give a clear answer. Instead I'll highly recommend an illustrated version of Stephen Hawking's Brief History of Time to dig deeper into this question. I personally find that big questions like this really do require more than an article or video.

gizmo6863• 6 years ago

If you run the big bang model far enough into the past, you arrive at a singularity. Near that point, relativity starts to break down, and we don't really know what physics looks like.

For unrelated reasons, we cannot see back past further than about 10^-6 seconds after the big-bang, because the universe prior to that point was so hot and dense that photons would be reabsorbed almost immedietly.

Once you avoid everything being in literally the same place, the problem just becomes having the photon move towards us faster than the expansion of the universe.

AaronFriel• 6 years ago

Not a physicist or even anything more than a bachelor's in anything - though this is my understanding.

Many depictions of the big bang show the entire universe - something which may not have a finite volume - collapsing to an entire point.

It might be more illustrative if you imagine when you look at one of those drawings that it is in fact "merely" depicting all of the space within a finite volume today collapsing to a particular point in the past corresponds to the big bang. Conversely, things arbitrarily close together in the big bang can be arbitrarily far away now. There is no "center" of the universe, it's more like the shriveled up balloon analogy. Draw a bunch of dots on a blown up balloon and let it deflate, everything gets closer together but no one point is the center. So it doesn't make sense to ask "where were we 12 billion years ago?" The answer is: closer to everything we can see.

This explanation corresponds to a universe whose shape has zero curvature or negative curvature. WMAP and other experiments have suggested the curvature of the universe is very close to zero, but even a slight deviation above or below has dramatically different implications.

jules• 6 years ago

Our galaxy and that galaxy were already far away from each other 12 billion years ago, even if they started at the same place 13.8 billion years ago.

crispyporkbites• 6 years ago

The photons have spent 12bn years travelling through the universe, and they’re just hitting the Hubble telescope now.

Both objects started moving at the same time but at different speeds and in different directions- on top of this the universe itself is also expanding, so the gaps between galaxies is actually growing, meaning it takes longer for the photons to get here

btilly• 6 years ago

Well, let's try to explain general relativity, shall we?

First of all, the universe is expanding. A good visual is to paint stuff on the surface of a balloon. Everything on the balloon started off close together. But as the balloon expands, things on the surface of that ballon get farther apart. So it is with the universe.

Where did this happen? Everywhere, and nowhere. The balloon is an analogy for the structure of the universe. The balloon exists in a 3-D world at a time and place. But all notions of time and place are defined within the structure of the universe. So I'm describing what happened everywhere. All places used to be close. And now they are not.

Now the Big Bang theory is this. If you play that tape backwards, everything that we can see was once really close together. But still had all the same stuff. So the universe was a hot, dense place. Then it began expanding, and got large and cool and fairly empty.

So if everything used to be close, why does light only now reach us from somewhere that wasn't that far away originally? Well look at light as being like an ant crawling on the surface of the balloon. At first your journey doesn't look far, but the balloon starts expanding and the trip gets longer. You keep traveling and it gets longer still. That's exactly the plight of light from the early universe.

Did that help?

dmalvarado2• 6 years ago

The ant analogy helped a lot.

fosk• 6 years ago

I have a very naive question: if everything expands, why aren’t planets also expanding and why isn’t any molecular structure expanding as well? In other words, what does expand the universe yet prevents the planets (and us) from also expanding with it?

linuxftw• 6 years ago

Apparently, the universe expanded much quicker than the speed of light during the big bang. So, for us to see something from 12 billions years ago, it would have to be 12 billion light years away from where we are presently.

Since light travels all directions, if something was older than presumed aged of the universe, statistically speaking, we'd be able to see some of it from here.

aardshark• 6 years ago

I think your question is simply explained by the fact that the universe initially expanded much faster than the speed of light. Then it slowed down. The light has had time (12 billion years) to catch up.

ThomasBHickey• 6 years ago

There's an article in Wikipedia about a galaxy and its relative distance that touches on this: https://en.wikipedia.org/wiki/UDF_423

cheez• 6 years ago

Universe expansion was huge, immediately. That's all.

ianhorn3• 6 years ago

What blows my mind even more than that is the fact that the universe is apparently 93 billion light years in diameter despite being only 14 billion years old. Intuitively, I'd think that the radius of the universe would be smaller than the age of the universe. Stuff in the universe would go outward more slowly than light in the universe would go outward, because stuff moves slower than light. Apparently that's not the case. Space and time are weird.

takk309• 6 years ago

My understanding is that the expansion of space/time can exceed the speed of light because space time is what light travels through. Nothing says that two points can't move apart faster than the speed of light, just that information between them can't be shared faster than the speed of light.

mrich• 6 years ago

When the universe has a size, what is outside of it?

szymonsidor• 6 years ago

I stared at nothing. I stared at absolutely nothing and it was everything that I thought it could be.

Waterluvian• 6 years ago

It seems counter to the fundamentals of science culture that the director just kind of gets 10% of the time without need for approval.

Can anyone cast some light on this?

learnstats2• 6 years ago

I thought this was an interesting part of the article that wasn't fully explained - how this was negotiated.

There is some explanation for Director's Discretionary's purpose here in the Call for Proposals (although given that this Deep Field project seems now unlikely to qualify, this might have been retconned):

https://wayback.archive-it.org/all/20080527200338/http://www...

munificent2• 6 years ago

You can look at it as the process of becoming director is itself approval for those kind of discetionary choices. When an organization works well, it entrusts power to those who have the judgement to use it well.

If someone needs to get ten different kinds of approvals, are they really a "director" for most meaningful senses of the word?

walrus01• 6 years ago

I can't imagine you become director of the hubble telescope without having a significant, long-running track record of astronomical science behind you. The odds of such a person picking something interesting to observe are high.

aaroninsf• 6 years ago

Curious how strongly apparent size correlates to youth.

I am guessing that especially in the extreme deep field,

the distant couple-pixel dots correspond to the back of the room i.e. the oldest/most distant galaxies,

so this is in some real if crude sense looking through a core sample of cosmological time?

jaquers• 6 years ago

Get around "sign up if you wanna read" modal w/ window.bc.jQuery.fancybox.close(); jQuery('.fancybox-lock,body,html').css({overflow:'scroll'})

beastman82• 6 years ago

how do I use this

samcal• 6 years ago

  We learned new words for things. The decade changed.
  
  The first few pictures came back blurred, and I felt ashamed
  For all the cheerful engineers, my father and his tribe.
  The second time,
  The optics jibed. We saw to the edge of all there is—
  
  So brutal and alive it seemed to comprehend us back.

- excerpt from Tracy K. Smith's "My God, It's Full of Stars" [1]

Smith's father worked on the Hubble telescope, and she would be named US Poet Laureate in 2017. I highly recommend reading her poetic account of this photograph :)

[1] https://www.poetryfoundation.org/poems/55519/my-god-its-full...

aaron695• 6 years ago

So Bob was right, because Bob was right.

Good learning opportunity here.

We shouldn't think to hard whether he was right or why though.

tigen• 6 years ago

“With this achievement, the estimated number of galaxies in the universe had multiplied enormously — to 50 billion, five times more than previously expected,”

It seems that current estimates for this are higher, such as 100 billion in a 2020 article I saw. Anyone have an authoritative scientific source for the best current estimates?

50 billion galaxies (or 100) somehow doesn't actually seem so many. Considering that's on the same scale as the number of people on our tiny space rock. Yes each one has billions of stars inside, but still, we're talking about the entire universe.

Somehow, intuition suggests there must be more "stuff" beyond our observable universe.

keithnz• 6 years ago

I agree....

here's https://phys.org/news/2017-01-universe-trillion-galaxies.htm... where it's 2 trillion. Which is 1 galaxy for every dollar in the US Coronovirus stimulus package or 256 galaxies per person. Which makes it also feel like an approachable number for the amount of galaxies in the universe.

kiloreven• 6 years ago

I find it really sweet that the author of the article illustrates the perspective of our place in the universe as her father is known for just the same rhing :D

suzzer99• 6 years ago

I've had a framed poster of the Hubble Deep Field on my wall since the late 90s. I see it every day when I wake up. It's the only wall-art I own that I know I'll never swap out for something else.

johnnymonster• 6 years ago

Paywall links need to be downvoted

noisy_boy• 6 years ago

I was looking at the Hubble eXtreme Deep Field photo and in there locked on a galaxy that was just a dot and imagined that out of the billions of stars and trillions of planets in that dot, there could be life on a planet with a variety and richness and vast history that is unfathomable to us. Us and them, two dots unbelievably far away yet parallelly flowing through time. I think the only reason Space doesn't generate a lot more interest than it draws now is because it is truly mind boggling.

MichaelMoser123• 6 years ago

Will you reach a limit if you come up with a telescope ten times as big - where is the real limit? Is that an exciting question? I think there is a bit of rhetorics involved at interpeting the result of this experiment.

vlasev5• 6 years ago

You can pretty much make a telescope as large as you'd like, depending on your technological level. Hypothetically, you can use gravitational lensing to make a telescope via the sun! It's rather unfeasible at our current level of rocketry, but in time, maybe! Article: https://blogs.scientificamerican.com/observations/using-the-...

You can also use Earth's atmosphere as a lens too! It's an amazing video: https://www.youtube.com/watch?v=jgOTZe07eHA

Going even crazier, I can imagine we could some day use a massive black hole as a giant telescope.

nojvek2• 6 years ago

Isn’t it great the the starlink junk doesn’t photobomb Hubble?

It’s amazing we have a giant telescope outside the planet. We know so much about the universe because of Hubble and friends.

When I was young I truly believed in heaven and hell as some distant planets. Then learning about Hubble, cosmic radiation and the fact that we can see millions of lightyears away which is an incomprehensible distance and the fact that our vision is limited by speed of light that seems super slow relative to those distances.

I really had a paradigm shift. Heaven and hell are probably good ideas but don’t actually physically exist. Took me a while to digest that. If they were actually there, we’d have seen them by now.

I have a lot of respect for Astronomy.

vlasev5• 6 years ago

Just a nitpick: Hubble is at a much higher altitude than Starlink and as such would never be interfered with.

ngcc_hk• 6 years ago

Such a brave soul.

When Hubble stared at nothing for 100 hours (2015)

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