This was a good one: https://www.reddit.com/r/WritingPrompts/comments/35mgnn/wp_a...

https://www.amazon.com/Shadows-Rediscovered-Classics-Roger-Z...

They'd likely have radically different definitions of poles. One hot enough to melt lead, one cold enough to freeze C02.

https://www.amazon.com/Proxima-Stephen-Baxter/dp/045146771X

It's a Sci-fi book about life on Proxima Centauri and includes the idea you mentioned.

(Also a really good read!)

I have this annoying habit of impulsively buying books recommended on HN. Never been disappointed by one though. So thanks! :).

Well, in a certain sense the West Pole and East Pole would exist in the manner you describe, but the behavior is not similar to that of the north and south poles. The stars will still rotate around the north-south axis, and east-west still won't affect that. It's not obvious that both phenomena should be called "poles".

Note that "north - south" poles already refers to two distinct phenomena, the axis of rotation and the axis of the magnetic field (these happen to be closely-enough aligned on Earth that the latter has historically been used as a proxy for the former, though this is by no means a universal feature of all planets.) The axis of orientation to the sun, for a tidelocked planet, seems no less plausibly described as "poles".

People always make use of local geographic features when describing directions; river communities use "upstream" and "downstream" and island communities use "inland" (away from the sea). Those aren't termed poles (even though "inland" is defined by reference to a line perpendicular to the ground!), and while I agree that the axis of orientation to the sun is more pole-like than they are, it's still different enough that I don't see that it would necessarily be referred to in the same terms.

Sure, and that's why the axis-to-the-star probably wouldn't define "north" and "south" poles, but not a reason it doesn't make sense to call that the points where the surface intersects that axis through the planet "poles".

Having thought a bit more, I tend to think it's unlikely that both axes would be significant to the same people (and therefore that they are particularly unlikely to share terminology):

- One important aspect of east-west historically is that east is sunrise and west is sunset. This wouldn't matter to anyone on Tidelocked World, but it corresponds pretty well to the idea of having a Day Pole and a Night Pole. The Day Pole would be apparent to anyone who lived in an area where the sun was visible, and the Night Pole would be totally unapparent to everyone else; it is significant only in that the Day Pole is on the opposite side of the world.

- Historically, north is cold and south is hot. This would apply, I believe, only to the day side of Tidelocked World. It reinforces the idea of a Day Pole while doing nothing for the Night Pole (everything beyond the terminator should (?) be equally cold).

- North and south are also defined by reference to the stars, which rotate around the polar axis (this is the origin of the word "pole", and would definitively rule out a Sun Pole if "poles" had to be defined that way, which they don't). This would be apparent to everyone living in the night, but probably not to anyone in the day.

If you believe all that, then we have the sun as a navigational aid that guides us toward the hottest part of the world, and the stars as a navigational aid to indicate the North and South Poles, but no concept of a Night Pole, because that concept is useless on the night side and there are no local indicators for where it is. Day people would be likely to refer to "sunward" and "darkward" in the manner of islanders, and night people would likely refer to "north" and "south", but day people would be unlikely to recognize "north" and "south", and night people would be unlikely to recognize "lightward".

I don't think so. Winds, diffusion, conduction, refraction probably come into play.

It does occur to me that the Night Pole might be revealed by the shadow of the planet, if it has a moon.

Think of the industrial applications! You'd have early metalworks near the hot pole, and when they'd finally figure out thermodynamics, I could imagine a planetary thermal engine created by bridging the hot and cold areas...

So that'd be more advanced than us I think.

http://arxiv.org/abs/1304.0445

https://www.goodreads.com/book/show/20518872-the-three-body-...

So there might be a season change every so often

That said "I can imagine" isn't terribly good science. Articles like https://en.wikipedia.org/wiki/Dynamo_theory don't make mention any role of the Moon, and googling around drowned out the actual question by talking about how the Moon might have once had a magnetosphere, along with articles about how smaller planets might be able to.

It doesn't. The planet was spinning when it coalesced from a planetary nebula and conservation of angular momentum means it sped up as it coalesced. As the moon moves further away it _slows down_ the rotation of the planet.

I tried to find some discussion on this subject. I found this [1] quite recent paper (2016-03-31) that states that influence of Moon is necessary to maintain Earth's magnetosphere. Just food for thought. There are articles that quote this paper on the Web, but they have this suspicious date of 1st April (but paper was published day before) :)

[1] http://www.sciencedirect.com/science/article/pii/S0012821X16...

We can't calculate those odds. We can't even start. It's like trying to calculate the likelihood that future AI will destroy humanity. We just can't know because it's so deeply theoretical.

For that reason, it seems absolutely absurd to me that someone would say with certainty that life exists elsewhere in the universe. We just can't know. The unlikelihood of its existence could be infinitely high and we might just be lottery winners. Who knows?

And frankly, I hope we're alone. I really don't want to share the universe. It would be so much nicer just to have it to ourselves. Let us do what we want, wherever we want, without interference until the heat death of everything.

As for not sharing the universe: what a depressing thought.

I'm not sure you have a conception of how truly BIG the universe is. In fact, according to current cosmological evidence, it is infinitely big.

But even if we confine our discussion to our Hubble Sphere, there is almost certainly life elsewhere in the universe. It's just that that life might be very, very far away.

I think the law of large numbers applies here. The likelihood of life existing being high enough that we are the only ones, but low enough that our existence isn't winning some 1 in a googolplex chance just strikes me as an anthropocentric conceit.

We don't know how difficult it is to create life. The universe is big, but the difficulty of creating life might be much bigger.

Thus. It is not certain that there is life elsewhere.

The closest star. But, we struggle to observe it in any capacity. Indeed, only today we did. And that's nothing to say of the next closest star, or the next, or the next, ad (nearly) infinitum.

If planets in this zone aren't as rare as we think, life in the universe might also not be as rare as we think.

To me, the question is more "where," rather than "if."

Something that's probably a lot more rare is favorable conditions over a long time period. It took a long time for life on planet earth to evolve into more complex forms.

I'm pretty sure we're not the only ones out there. But will mankind and our space neighbours exist long enough to facilitate communication?

Is every species that is competitive enough to subdue all other life on its planet doomed to disintegrate due to internal conflict?

e.g. imagine a universe containing a million intelligent civilisations, but each of those intelligent civilisations is in a separate galaxy at least 100 million light years apart. If that is our universe, we might not encounter any of those other civilisations in the next million years. The odds of human extinction could easily be higher than the odds of having any contact with them.

The alternative is the anthropocentric view that the entire universe was created merely for our viewing pleasure on Earth.

What you are talking about is "anthroexclusive", or something like that.

See my response to whom you agree with: https://news.ycombinator.com/item?id=12359111

We know how stars form, how galaxies form, how solar systems form. We know the general consistency of the galaxies around us, and some systems in our same galaxy. It's not a big leap to assume that some percentage of them will be hospitable (for a time) for life, at least life as we know it.

I'd say the arrogant views are that the whole universe was created for us, or that life must be thoroughly plentiful throughout the universe. The least arrogant view is that it's somewhere in-between, but more importantly, to always adapt to the latest evidence.

So to try to extrapolate that to the "inevitability" of complex life in the universe is like saying that your name will be spelled out in ASCII in the repeating digits of Pi somewhere. Maybe? Can you prove it? No?

I'm not a philosopher of science, or statistician. But the assumption that somewhere there are things "like us" seems to be both arrogant and very teleological -- an implication that the universe proceeds towards an order very similar to us. (Popular science fiction is infested with this kind of telelogical narrative.)

And contrary to arrogantly thinking earth-life is special and unique my argument is that we are just one of a rather infinite variety of "things" in the universe. Life is amazing and complex -- but so are the clouds of Jupiter.

Well, "like us", inasmuch as an entity that is self-regulating, and capable of response to external stimuli. The most basic assumptions for life.

So yes, at some level it is arrogant to assume there's anything else like us. Your view is very nihilistic. But, until we know of other sentient species, it is all about us. We are, as far as we know, very lonely, ex-nihilio orphans in the vast universe. It's only arrogance to nothingness to posit there might be more life in the universe. It is not arrogant to humanity.

So, yes, we are in many ways better than clouds of Jupiter. But of course it is us making that claim. So what? Allow humanity some slack. If we have offended some unknown creator with our supposed insolence, perhaps it should make itself more easily known.

But we make no use at all of 99.999999999999999999999% of the universe, so how does it hurt us if some other species do?

Liu Cixin's The Dark Forest has an interesting take on this. Basically it's conceivable that the game-theoretically optimal policy is to kill any other sentient species you come across, even if it means you lose access to whatever resources they currently have. This argument falls apart at some point, because it's (presumably) not optimal for all humans to try to kill each other all the time, but it's an interesting idea nonetheless.

Basically we can't say a much about what the fraction of planets that develop life to planets that have conditions for developing life is based on just one example, but there's no apriori reason for particular pessimism about that number just yet.

Now how likely the conditions are to begin with is a different matter. They've certainly improved in the last decade, since planets at least seem to readily form and earth-sized things too, and apparently easily end up in orbits that could allow for water to exist etc. There's clearly a bunch of other potential conditions that may be necessary for abiogenesis -- untill we know more about how exactly it happens, we can't tell (and actually finding separate origins of life would greatly help in undestanding what that is)

I for one think it very likely this particular planet isn't habitable, because Proxima is such a lousy star, but it's certainly not ruled out. But also that microbes are likely reasonably common in the universe. Around a small fraction of the total number of stars, only some small percentage of what we'd consider candidates today based on their sizes and orbits -- but still that leaves immense numbers.

If further climate outcomes continue to track Hansen's thus-far correct 35-year-old predictions [1], then we've already passed some kind of tipping point and "the heat death of everything" could potentially mean Venusian-style anthropogenic cooking of Earth in some worst-case scenarios, and mass population dislocations and mega-scale environmental disruptions in milder scenarios.

If it turns out that life as we know it is exceedingly rare (and I must admit that the more we find out about exoplanets, the more disconcerted I am while realizing that the hazy possible solution space to the Fermi Paradox is becoming rather uncomfortable as the resolution grows with each passing decade), then that would be truly a tragic outcome.

[1] https://tamino.wordpress.com/2016/08/16/crystal-serenity/

[0] http://www.physlink.com/education/AskExperts/ae181.cfm

Somehow we always feel that aliens would be always bad to humans, there might be good aliens also somewhere who might help us in solving our current diseases/share advance knowledge or even give us new resources!

For all practical purposes we have it all for ourselves and we are doing nothing with it.

There is no serious investment in seeking a different home outside of earth.

The universe is huge, really huge, so huge that even the distances to other planets in our solar system are so vast, that when you would consider the earth 1mm big, these distances would still cover thousands of kilometers. It's not possible to draw a liniarly scaled map of our solar system, so big is it.

Good news: life has plenty of space and probably also plenty of planets to find its way multiple times in the universe :)

Bad news: we probably won't find this life ):

Ever since I saw it done in the new Universe series, a pet peeve of mine has been treating the giant impact hypothesis as some kind of established fact. Even the name on the wikipedia page includes the term "hypothesis": https://en.wikipedia.org/wiki/Giant-impact_hypothesis

The hubris surrounding the presentation of that particular hypothesis to the public is really, really awful. I actually stopped watching that new Universe series mid-episode after hearing it presented as fact (this was sometime in the first few episodes, maybe the first episode) and stopped reading this wikipedia page just now.

It is actually the most active flare star we know. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1063292/

Should I admit on HN to having watched a Vin Diesel film? Pitch Black, anyone?

Astronomy nerdship aside, I loved Pitch Black. Such a good movie. I haven't watched any of the sequels, though.

The first game that they released, surprisingly for a movie to game adaptation, was also quite good.

Fabulously geeky dude, I like his style.

[0] - https://www.goodreads.com/book/show/99245.Nightfall

[1] http://edition.cnn.com/2016/08/24/health/proxima-b-centauri-...

Fun to think about, anyway.

The distance between the planet and the star is ˜7,000,000 km. The diameter of the star is roughly 1.5 * the diameter of Jupiter: 207525 km. The angular size of the star from the surface of the planet will be the arcsin of (207525 / 7*10ˆ6) or about 1.7 degrees.

This is a little bigger than three times the apparent size of the full moon or the sun from Earth.