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Comment by duxup | Hacker News Reader

Growing up I absorbed all the space stuff I could find.

But it wasn't until recently that I realized that the solar system didn't just form into some static natural state where it largely didn't change until say the sun was finished with it's lifespan.

Rather it evolves, changes, planets are habitable, then not, moons are formed and break up, even frozen planets are geologically active and are changing, Saturn's rings are relatively recent and etc.

Not sure how I didn't pick up on that.

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I'm not sure how old you are, but a lot has changed, recently, in our knowledge of Earth, its evolution, the solar system, and astronomy.

One of the books I had growing up was a Patrick Moore juvenile book on astronomy, probably Seeing Stars (1970). That had a ... pretty good ... description of the state of knowledge at the time, but it was published only about five years after the 4.5 billion year figure for the age of the Earth, and plate tectonics as a geological mechanism, were formally adopted.

The Viking missions, Voyager, Mars rovers, New Horizons, the Hubble Space Telescope, Keck observatory, LIGO ... were all in the future.

The degree of development in the field of geology in the 20th century alone has been staggering. Credible scientific estimates of the age of the Earth in 1900 were as little as 30 million years (Lord Kelvin's gravitational collapse/cooling calculation). Interestingly, parallel developments in physics (notably radioactivity) helped give us the clocks we finally needed to measure geological time. We could trace landmass movements, make some determination of interior structures using seismic (and I suspect nuclear blast) waves, and more.

Much of the more interesting physics (and some chemistry) Nobel Prize awards of the past 50 years have been in sensing and detecting, at large and small scales, again, giving tools to measure, detect, and distinguish patterns, structures, and phenomena.

Within my own lifetime notions such as the asteroid hypothesis for the mass extinction of the dinosaurs have passed from wild theory to accepted fact, we've got evidence of 300 million-year snowball Earths, strong evidence concerning early Earth evolution, atmospheric composition, and life. We have detected thousands of extrasolar planets (a value still strongly limited by what sizes, types, orbits, and distances at which such detection is possible). Pluto's been un-planeted, and imaged. We've kissed the face of comets and returned their dust to Earth.

And we're starting to get some idea as what the long-term stability of planetary orbits might be --- the notion that planets may wander not only in the skies but in their orbital characteristics ... would change things markedly.

So it's quite possible that what you didn't pick up wasn't there to pick up when you were learning it.

Very good point. I'm in my 30s and it's even come a long way since I was a kid.

We didn't know until recently that there were planets orbiting other stars. We suspected that there might be, but we didn't know. The idea that there could be other "earth-like planets" was a hopeful guess.

When the headlines started coming in from Kepler, that was huge. Very exciting and huge.

The big news we're looking for from James Webb is the possibility of grabbing evidence of chlorophyll fringes in the IR spectra of other planets.

That is going to be huge news if we find it (I suspect we'll get a lot of other results first though and a ton of new interesting work looking for alternative photosynthetic chemistries).

Wow, chlorophyll-equivalent detection? I though JWST was just going to be able to prove diatomic oxygen or other gas chemistries in atmospheres.

https://www.jwst.nasa.gov/content/forScientists/faqScientist...

> asteroid hypothesis for the mass extinction of the dinosaurs have passed from wild theory to accepted fact

We should NEVER accept a hypothesis as fact because that makes people stop thinking or searching for answers. And there’s no way we can even definitively say something that happened tens of millions of years ago actually happened.

I personally think it was an asteroid too, but I never want to be arrogant enough to think it’s a closed case now. For example, it could have been the switching of the poles causing cosmic radiation to cause mass extinction, similar to why the Neanderthals disappeared and there would be no way for us to know.

There have been recent advancements in the hypothesis you may find interesting:

https://phys.org/news/2021-02-asteroid-crater-case-dinosaur-...

We can of course continue to look for disconfirming evidence, alternate explanations, or Incontrovertible Signs That God Is A Prankster, but come a certain point and the focus becomes one of refining rather than overturning theories and models.

It’s rather arrogant as a species for us to believe that enough evidence remains tens of millions of years after something like that happened that we can come to a conclusion. For all we know, a pandemic could have swept across the globe and killed all the dinosaurs and there would be no way for us to detect it.

Occam's razor suggests:

1. Such a pandemic (or other calamity) occurring simultaneously with overwhelming evidence a catastrophic asteroid impact is exceedingly unlikely.

2. Cross-species pandemic resulting in mass extinctions are similarly unlikely. Boom-bust population cycles perhaps. Mass cross-species extinction not so much.

3. Patterns of extinction (and survival) far more closely match the presently-accepted conclusion.

4. Precisely because an infectious agent leaves few multimillion-year traces, any defence of such a hypothesis can advance no further than "it might have happened". This is not evidence-based argument. (Traces of pathology might be preserved in fossil or amber substrates.)

Point remains that multiple highly consistent widely-distributed lines of evidence point to the asteroid hypothesis.

One unsubstantiated Hacker News comment points to the epidemic scenario.

Absolutely, very well said. Our understanding of the cosmos has changed dramatically in the past 100 years. People forget that we were still debating whether galaxies beyond our own existed (!!!!!!!) just 100 years ago.

https://en.wikipedia.org/wiki/Timeline_of_knowledge_about_ga....

With such knowledge ready at hand for such a thorough comment on HackerNews, I am curious what your learning lifestyle is (books mostly? What kind? How many hrs a week? How much other media do you consume? Youtube? Netflix docos?). As I get older I'm realizing that life is too damn short to learn all the stuff I want to learn and so am constantly thinking about how best to spend my time.

There was a very interesting thinker in the 18th who wrote that eventually the Earth would gain a planetary ring. He talked about how everything changes, even though our lifespan is so short we don't see it. And he was particularly speaking about society: afterall, he was a very progressive member of the generation that indeed abolished slavery, even though a lot of people said before: "Slavery's been going on for 80k years, it will never end". I learned a lot from his writings, and I believe our society could learn a lot from them to this day.

The wikipedia article is very poor compared to the depth of his work/thought but here it goes anyway for reference: https://en.wikipedia.org/wiki/Charles_Fourier

Any books or writings of his you would reccomend in paticular?

I love almost all his work tbh - actually I've been translating a compilation of some of his writings from spanish to portuguese and I also contributed to his page on portuguese wikipedia :)

You can dive in from wherever, and you will be able to know his cohese and wonderful universe of thought - it really doesn't matter, because it's a single entity, so you can start from his thoughts about family, work, slavery, astronomy, architecture, higiene, urbanism, politics, religion, sex, tolerance, women, commerce, law, philosophy, love, etc

I should warn you to beware of the translation because there are bad ones - he's a guy coming up with words and concepts and always playing with language and meaning, so you gotta be able to read between lines. I wish you a good reading, if you can find them because they seem to be kinda rare, and mind = blown! If you'd like to exchange some ideas about it later, feel free to get in touch!

My limited understanding says that his prediction is spot on as we seem to be building a planetary ring of space junk.

Not sure how I didn't pick up on that.

The sheer scale of it makes it hard to perceive, so probably you aren't the only one and probably a lot of the literature has similar blind spots which implicitly signals "this isn't happening" and we pick up on that and it gets implicitly repeated until it's hard to give any kind of push back in our own minds.

For sure. You'll find that our notions of our own world and societies are also very outdated on average due to how rapidly they're changing (and by and large improving).

A wonderful, easy to read book on this that I recommend is Factfulness.

https://www.ted.com/playlists/474/the_best_hans_rosling_talk...

https://www.amazon.com/Factfulness-Reasons-World-Things-Bett...

Until we started sending probes out there, we didn't know much about those bodies. Tectonic plates on Earth were not confirmed till the '60s or so, so... it's not surprising.

I sort of got the impression it was static as a kid as that's how all the books were written. I think its changing nature is a relatively recent discovery. I remember a lot of debate as to whether a meteor could have done for the dinosaurs because people were skeptical that sort of stuff happened but it turns out chunks of rock smashing into planets is quite common and basically how they got here. I also got the impression Earth was more unchanging than it is. It was a surprise to find you could walk from England to France 10,000 years ago or so.

I think it's the way it's presented. We still have a sort of Newtonian "clockwork" view in primary education of astronomy.

The "clockwork" view is objectively incorrect due to being the wrong scale. (Some) Accurate scale models of the solar system get played out across city blocks.

If it's a tinkertoy style model or a drawing within a book, it's made up BS. There are no books large enough to actually show it to scale.

Edit: For the pedants of the world, I have added "(Some)" to my sentence. "Not all accurate scale models" of course. Some are even larger than that.

2nd edit: Folding another comment in here as well that I deleted :

https://en.wikipedia.org/wiki/Solar_System_model

The Sweden solar system scale is listed as 1:20,000,000. Others have used a different scale and been fit into less than an entire country. There are several around the world.

In York, it is spread across 6.4 miles:

https://astrocampus.york.ac.uk/cycle-the-solar-system/

There's another in Greater Boston:

https://foursquare.com/eric_odea/list/museum-of-science-bost...

City blocks? Sweden has a scale model of the solar system that stretches across the entire country - north to south. And even then it isn’t actually big/long enough for the entire solar system.

Depends how small you’re willing to make the bodies. In Sweden the Sun is a huge spherical building.

and if it was smaller the planets would be invisible.

It could be made smaller without risking invisibility of any of the planets. The smallest planet is Mercury at 25cm.

The best view of the solar system I've experienced that could be incorporated into classroom learning is a VR tour. It not only shows you the relative distance really well, it also shows you the size of the planets relative to each other and you really get an intuitive sense of the massiveness of the sun (and other stars), for example.

I read Doreen's comment as at least city blocks.

Sweden was, last I checked, larger than a city block.

Here's a Cody's Lab video showing a "to-scale" solar system. https://www.youtube.com/watch?v=dCSIXLIzhzk

It's astounding that astronomers have mapped out the skies just by looking up. It's like as if I mapped out my entire city just by looking out the windows of my house.

If your city was 99% empty by volume and your house rotated every day it wouldn't be THAT difficult :)

"We can only speculate as to what is on the far side of the house on 123 Anytown Road. Human exploration is needed."

What's mindblowing is the search for planet 9...once you start to realize that we are surrounded by thousands of dead solar systems (brown dwarfs that very likely were red dwarfs before) in our immediate neighborhood.

Imagine what we could accomplish by mining their resources!

What does this mean? Surrounded by thousands of dead solar systems? Like nearby (dark) stars?

They are called brown dwarfs... but it's better to link the NASA backyard worlds project directly for the curious:

https://www.zooniverse.org/projects/marckuchner/backyard-wor...

I suspected so. But all those objects are in this solar system.Brown dwarfs are sub-stellar bodies.

Touche, you are technically correct.

Though some might argue that in the changing nature of fusion reactions and body mass, this sorting of sub-stellar bodies is only true for as long as our star is a red dwarf.

Once that's over (thinking in the larger timescale of things) and it becomes a brown dwarf, what then? Wasn't it a solar system at one point in time?

(I'm not an astronomer, my understanding is not absolute, please correct if I'm wrong) I believe our Sun is a type G, yellow dwarf. A red dwarf is usually much smaller, if considering "red dwarf" being a type M, then usually no more than 0.6 solar masses, usually much smaller, and a tiiiiny fraction of the luminosity of Sol. Brown dwarfs are not massive enough to fuse hydrogen, where red dwarfs generally are. According to https://en.wikipedia.org/wiki/Red_dwarf, above 0.25 solar masses, they should evolve into red giants, otherwise will shrink into a white dwarf once hydrogen fusion is ceased. The universe isn't old enough to have any red dwarf of 0.25 solar masses to do so, however as their lifespans are so long.

> Once that's over (thinking in the larger timescale of things) and it becomes a brown dwarf,

Our sun will never become a brown dwarf. Stars have their life-cycle and nomenclature. You cannot made your own willy-nilly.

I find it kind of weird to have a different word for the same object depending on where it is. As I understand it, Jupiter would be a brown dwarf except that the presence of the Sun disqualifies it.

Jupiter is orders of magnitude too small to be a brown dwarf. The "brown" implies IR radiation generated by gravitic collapse. If Jupiter was massive enough to generate its own radiance it's unlikely Earth would be around to observe it.

The simplistic solar systems and textbooks in grade school are not just misleading when it comes to scale, but they're really really misleading. Few people really comprehend the scale of things in the universe.

Scale isn't the right thing to complain about here. Compare https://en.wikipedia.org/wiki/Brown_dwarf :

> most brown dwarfs are slightly smaller than Jupiter (15–20%)

> Brown dwarfs are all roughly the same radius as Jupiter.

The suggestion that Jupiter is "orders of magnitude too small" to be a brown dwarf is obviously wrong in terms of size, but it's also wrong in terms of mass:

> at the low end of the range (10 [Jupiter masses]), their volume is governed primarily by Coulomb pressure

It means OP does not have the slightest clue of what he is talking about. I hope he is talking about trans-neptunian objects in THIS solar system.

Maybe a tangentially related question, what happens if you form a system very much like our solar system, but the central body never actually ignites and it just remains a dark ball of hydrogen. Would the system still be called a solar system?

That'd be more of a rogue planet with moons.

That's what i was thinking but if it's the size of our solar system and the 'moons' had moons it gets weird.

(But i guess our moon could have moons so it's moons all the way down)

Sometimes called moonmoons.

A system the size of our solar system centred on a jupiter-sized object wouldn't be very stable - it'd be quickly disrupted by an encounter with a star.

Brown dwarfs are failed starts, something between a large gas planet and a red dwarf. Red dwarfs don't turn into brown dwarfs when they die. In fact a red dwarf's lifetime is so long (up to trillions of years) that its unlikely that we ever see one dying. It is believed that they turn into white dwarfs when that eventually happens.

Beltalowda! The expense series has an entire faction based on asteroid miners.

>(brown dwarfs that very likely were red dwarfs before)

This is incorrect. Red dwarfs will end their lives as black dwarfs. However, no black dwarfs are currently expected to exist because the universe is not old enough yet. Red dwarfs, in particular, are expected to have lifespan of trillions of years.

A lot of things we think are static do actually change quite a bit. Tiny changes add up to a lot over time. I once buried a little canister with some money inside (in a shallow hole next to a distinctive tree) in the woods while hiking, just to see if anyone would find it. I came back a couple months later, took me a very long time to find, I did eventually, and it was much, much deeper than I had buried it. The soil must have shifted way more than I thought it would in that short period of time but it's not something you would ever notice from day to day.

In a geology class we learned what very few people realize, that Earth's landscape is constantly changing. Only on a scale humans generally can't perceive.

Highly recommend anyone to look into Oceanography! The ocean floors reveal a lot of ancient geological history and the Earth is much more dynamic than what meets the eye. Sea floor spreading, plate tectonics, and much more can be studied simply by observing the ocean floor!

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