Space Is Full of Planets, and Most of Them Don't Even Have Stars
forbes.com
forbes.com
It seems like there is an obvious further inference to make - people have debated whether life originated on earth or not. Given that the vast majority of planets do not have a star, and given that we know there are chemotrophs even on Earth that prove it is possible to live without a sun, it seems overwhelmingly likely that life came from one of these rogue planets that was large enough to retain enough heat underground for the evolution of life over the first few billion years of the universe. That would also neatly explain why evidence of life appeared so soon after the Earth became solid.
How life began is obviously still an unanswered question, but if the conditions for self replicating molecules were sufficient early on for Earth, I'm not sure why billions of years would be needed for life to form versus several hundred million years.
Planets that exist without a solar system, but do retain sufficient heat, might have been out of solar winds harm ?
Further questioning I have though is, does solar radiation penetrate through ocean water?
What radiation is between solar systems or what rogue planets would likely encounter, and how that effects single cell life, amino acids, organic compounds, and any other building blocks to life?
Barely. 10km of water will shield you from almost any amount of radiation, and we know of life forms which live at those depths, so they could have developed even when Earth was completely bathed in radiation.
https://en.wikipedia.org/wiki/Abiogenesis#Earliest_biologica...
From looking at the graph, and the 300 milion year doubling, they seem to put life complexity at about 256 base-pairs at the origin of the earth.
There should be a link to the actual paper in the article.
...today. Life was simpler back in the day. For example, RNA world. This more primitive life might not survive more sophisticated life. (thougn it's also possible it's still around, but we haven't noticed it; or haven't recognized it as life).
IDK if small enough, but viruses are simpler.
If it can reproduce - e.g. a short strand of DNA or RNA or even something simpler - it could form the beginnings of "life" as a precursor, even though it wouldn't meet our current definitions of "alive".
There's theories of fatty spheres being the first "cells" (really, "kinda sorta cells").
Of those, I find plausible the observation that as we tame the world to suit us, we shrink. Cities, civilization, supermarkets, products, TV, internet. By this trend, we'll live in dream terranes before long. (BTW as people get richer, reproduction gets less).
But we'll need power, and eventually a dyson sphere to capture all the sun's light - perfect for an inward-looking, closed-off people! Then what, I'm not sure. Perhaps long before that, we won't need other suns; we'll have artificial suns (controlled fusion).
That's what happens to everyone else: as they grow in technological sophistication, they get better and better at directly meeting their own (previously evolved) needs.
In the context of this thread, lets say you are a species which stepped out of your planet, there are plenty of asteroids, and even planets lying around you can mine for resources. You settle billions of your kind in space. You are not running out resources and have no motivation beyond research and science to venture out a little far.
Would you, such a race, want to travel interstellar distances? You would travel far distances by organic growth.
Also its likely how old the universe is anybody who didn't kill themselves to extinction, is likely at our phase of development. And is likely asking the same questions as us. Those beyond our phase of development are hiding for a good reason.
It's not a given that alien civilizations "should" have developed this or that technology that we ourselves don't have.
As a result, intelligent life around the universe only exists as short 'blips', being around for too short a time to ever meet other species.
I don't get this. What use are ethics when everyones dead and gone?
Seeing the wide spectrum of intelligence and education that humans manage it's hard for me to believe we'll ever reach a point of uniformity as a species were something like self-imposed extinction would be plausible.
There's always a risk of that, unless you can 100% guarantee this won't happen you're basically gambling with another person's life. I don't think you have the right to do that.
The history of man suggests otherwise. The more our civilization progresses, and the more the population swells, the broader the array of philosophical positions those within the civilization tend to hold. We have no evidence for everyone eventually coalescing around one 'right' belief set.
History is also littered with non-reproductive sects, like the Essenes, aesthetics, or, today's answer to these, anti-natalists and child-free individuals. These groups don't tend to be very good at passing their belief systems on to new generations however, as one might expect, and they don't tend to last particularly long once they've emerged on the civilization scene.
Why are there no other detectable signs of human life, like smoke signals, territory markers, or emissaries from any more but a handful of other tribes? Surely if advanced humans existed, they would have contacted these tribes by now, to share technology, discoveries, and medicine. Yet they haven't.
How can the whole planet be so... silent?
And, won't uncontacted tribes in the amazon have seen airplanes and such?
So, we don't see or hear artificial signs in other galaxies because light is from the times when there was not complex life in the universe.
Now, we only have to solve why we don't see or hear artificial signs in our galaxy. But the problem is not so perplexing because we are talking about one or two million years.
If, for instance, a big part of the galaxy is bad for complex life (after all, we are far away from the center and that could be relevant), Fermi's paradox is solved.
To be clear, I'm not saying that's what it is ... the fermi paradox is a great thought experiment. But let's just keep things in perspective. Low odds don't mean something won't happen, just like "true random" doesn't mean the same song can't/won't play 10 times in a row ;)
As in, the universe may be littered with the ruins of single-planet civilizations slightly ahead of our technology level. We may have observed and cataloged many such planets, failing to notice the ruins.
If all the civilizations started more or less at the same time that us, it's not so weird that we have not found anybody else. If you add some other factor (maybe civilizations are only possible far from the center, so there is a big spread between them) the probabilities improve.
It also would mean interesting times ahead for humanity.
Of course, all this is only idle speculation.
http://www.jodrellbank.manchester.ac.uk/media/eps/jodrell-ba...
And just the existence of life doesn't mean there's complex life. We don't have a firm lower bound on how long life took to arise on Earth after we got liquid water on the surface but it can't have been more than 120 million years. Photosynthesis, mitochondria, and other innovations allowing for complex life like you and me took way, way longer. I made a diagram for a blog post here:
http://hopefullyintersting.blogspot.com/2018/03/the-drake-eq...
1)
Ordinary Matter ~10^53 kg (4.9%)
Dark Matter ~5*10^53 kg 26.8%
Dark Energy ~1.3*10^54 kg 68.3%
Undiscovered ? ?
Also, people talk a lot about not meeting aliens, but just talking to them. Based on the fact that we have little/no idea how Dark Matter and Energy works, and we only really use radio signals (when funding permits), it may be like trying to whisper at the Queen of England while standing in Norway; a telephone would be much better.
2) Tom Scott on immortality and risk : https://www.youtube.com/watch?v=B5a6wrJpxP4
3) Life may be so abundant in the universe that it's not worth talking or meeting up with. What would you say to a single mayfly if you could talk to one on it's level? No scientist or other person has bothered to try, and I think there's a good reason for that.
An interesting question to me is - if the Earth was seeded with life, does this mean we will find life elsewhere in the solar system, because they were too, or does it mean we will not find life elsewhere, because a rogue planet collided with proto earth in a very unlikely event, and the rest of the solar system (or at least the potential life supporting objects) came out of a sterile nebula around the sun?
It took hundreds of millions of years, possibly up to a billion years, for basic life to form on Earth. I would say that is not "soon"; it's a really long time.
The obvious response to that is, yes it seems like a long time, but it's not much on geological time scales. But it feels to me that there's an implicit circular argument here: the whole reason that geological time is measured in terms of such huge spans is because it took life such a vast amount of time to get to the point where humans exist to discuss it (understandably).
If current knowledge is remotely correct, heat death will happen, no matter how immortal Homo deus will become. The quarks are against us.
And if complex systems theory teaches us anything then it would be preposterous to assume any ultimate superiority in understanding the universe on our part.
Who knows who wrote crazy alien versions of Hacker News posts 2 billion years ago in one of the other couple of thousands of galaxies seen in Hubble Deep Field alone...
In fact, dolphins. Octopi. Yeah, pretty much a given I'd imagine, in the right complex ecosystem, that intelligence is a thing.
The first billions years on earth mostly involved the planet getting hit by large things and the surface melting. Repeat every millennium.
Ocean floor is continuously destroyed as it's subducted, and continents won't have fossils if they are under frequent bombardment.
Right, but if giant bombardments completely boil away the oceans and atmosphere to rain liquid rocks back down on the surface, there very very likely won't be life, either. So the claim is not just that "fossils only go back to X" but that X is so close to the end of the giant bombardments that there's almost no time left (geologically speaking - maybe 10-20MY) for "life but no fossils yet".
This is a common popular misconception. See something like Simon Conway Morris's book Life's Solution. There is evidence that life existed on earth almost as soon (geologically speaking) as the early bombardment stopped repeatedly boiling away the entire oceans and atmosphere, within something like 10-20 million years. Thus, all the interpretation about the implications of that.
If this happened it did so at the microbe level. Physical evidence would be extraordinarily difficult. If we did find evidence of another tree it would be so 'alien' to our tree that might mistakenly call it extraterrestrial.
The Milky Way has 4E^11 stars.
It has an upper estimate of 4E^16 planets.
It has a lowest estimate diameter of 100kly.
It has an estimated thickness of 2kly.
It's lower estimate volume is 63,000 kly^2.
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If planets are uniformly disrupted (they surely aren't), there are ~17 planets in every cubic light year. Sure, that's a hazard.
The change of hitting one while traveling one light year is in the order of 10e-16.
[1] at least in Newtownian physics. The argument is geometry, so I suspect but am not qualified to say it isn’t exactly inverse square in GR.
1. My numbers are on uniform distribution of planets. The milky way is not uniformly distributed, and I suspect this isn't either. I hypothesis most of the planets will be on the spokes, just like most of the stars are. In addition, while it is 2kly tall, there is not a uniform distribution across the height.
2. Interstellar travel doesn't involves traveling a minimum of 4 lys, and a maximum distance without being intergalactic would be about 100,000lys.
3. Your assuming instantaneous travel across the light year. In reality we would consume at least 1 year in travel time, and likely much more.
4. The amount of resources it takes to build an intersellar ship is very large. The cost of a collision is high. This doesn't change the risk of a collision, but it does change what we consider acceptable risk.
The earth itself is only 0.02 light seconds in diameter, yielding a cube of 8000 cubic lightmilliseconds. Compared to the 2.910^31 cubic light milliseconds in a cubic lightyear... It's a rounding error inside a rounding error.
For light seconds, you're looking at 2.910^22 (if my math isn't wrong). That's the amount of cubes fitting between earth and moon to fill a cubic light years.
Even superplanets with 15 times the size of the earth are simply dwarfed by the sheer volume of a cubic light year.
The largest stars we found measure 73 light minutes, a cubic size of 389017 cubic light minutes. How much of them fit in a cubic light year? 346 billion.
I guess the point people are trying to make here. If you can't see light coming off an object, then while traveling at interstellar speeds means it will be harder to spot objects until they get too close.
I think if you were to encounter a black hole, esp an inactive one, in interstellar space, you'd probably just get sucked in if you didn't notice the black disk...
If a black hole has been travelling without eating for long enough the accretion disk can disappear. If a black hole is large enough it won't form an accretion disk either as it swallows stars whole.
So while I agree it's still probably very small numbers I think you may be overcooking it.
If most planetary systems are anything like this one, planetary orbits are quasi-stable, and a visitor could easily destroy that stability.
It would take a while for that to play out - anything from months for a very unlikely very near miss, to many millennia for a distant visit.
Collision with planet sized object in space would be extremely rare. Even if you would travel blind it would be very unlikely that you would hit star or plant while traveling trough galaxy.
I'd imagine you could detect it blocking a circular patch of sky more easily and from farther off than you could detect the gravitational pull on your spacecraft.
Just don't steer twords the black disc and you'll be fine.
What’s one wavelength per minute if the formation is 1000km?
Or changes in density or relative velocity of the interstellar medium, etc.; gravity isn't the only feature that can alter the formation.
Why travel in a spaceship? If there's 100,000 starless planets for every star in the galaxy, then travel between stars on one of them instead. Build the habitations 10 km below water to avoid radiation. Travel at 0.1% light speed instead and get to the nearest star in 5000 yrs. Enjoy the journey, and slip into an orbit around the target star.
Speaking of pea-sized rocks, periodically fire one laden with electronics/optics/quantumics at the target star at near light speed and receive its transmissions for recon.
These would act as space weather beacons, forming some kind of illuminated space (high)way. An interesting idea!
As for the rogue planets, although I envision humans having some use for them, I doubt it will be for interstellar travel the way you describe.
Back in reality there were popular magazines like Discover that would have flashy covers about things like ROUGE PLANETS! Mostly just sensationalism.
Some semi-unemployed Hollywood writer would be paging through these while smoking out and get inspiration for a script. That is Star Trek's scientific insight.
And I'm a trek fan. OP probably just doesn't know a lot of this stuff was "ripped from the headlines" (of popular science magazines).
With so many asteroids and planets lying around. There is no real motivation to travel very far distances for resources. Once you start mining the first set of asteroids and settling your race in space. You could grow organically, and at some point mine a terrestrial planet. At that point you have so many resources at your disposal it doesn't really make much sense to move out to very large distances unless for science or your population is just multiplying beyond control.
I mean, yeah it'd be bad if a rogue planet smashed into us, or even came close enough to mess with our gravitational pool (or the moons). but I imagine if an earth sized or bigger slammed into the sun, that we'd feel the effects of this.
massive solar flare roasting our planet alive? a shower of ejecta from the collision that we pass through? it changes the mass of the sun in a significant way that changes the pull it has on the planets around it?
Considering the size difference I'm not sure we'd see much of an event as far as ON earth effects.
The voyage the planet takes through the solar system might drag some asteroids with it however, which could lead to some fun
The Earth is roughly 333,000 times less massive than the Sun. Think of it this way, If an asteroid hit the Earth that was, in relative terms, the size of the earth relative to the sun, it would be about 1/3 the size of Ceres. Everything on Earth would die but the other planets would probably not notice.
Given that the surface of the Sun can be treated, to a first approximation, as a fluid, an impact that was perpendicular to the surface would likely have the same characteristics of a milk drop. Which is to say a large wave would race away from the impact point and the collapsing of that wave in would eject a bit of coronal mass roughly equal to 1% of the mass of the impactor (note this makes a big, and unsupported, assumption about the viscosity of the solar corona.)
The only scary bit comes if the rogue planet enters the solar system slightly off the plane of the ecliptic and hits the Sun in a glancing blow. In such a scenario it could transfer a huge amount of momentum into the coronal mass which would then immediately begin to head away from the Sun. If the Earth were in the path of that mass it would probably wipe everything out after blowing off our atmosphere.
This wouldn't be good for the rogue planet either, which would probably enter a hyperbolic orbit and shoot away from the solar system on a new trajectory. In the unfortunate circumstance that this "coronal braking maneuver" was sufficient to slow the planet enough to be captured by the Sun, the remaining planets would get to witness periodic brushes with the Sun by the rogue planet until it had lost enough energy to fall into the Sun.
That would be mitigated if the orbit it fell into pulled it by Jupiter or another large planet which, by virtue of its gravity circularize the orbit sufficiently that it would not come near the corona on future orbits.
So yeah, you can't really add cold stuff to starts to extinguish them - stars are made from absolute ice to being with.
If it hits the Sun, it really doesn't matter how cold or how massive it is (up until it becomes a brown dwarf at which point we're talking binary star interaction levels of mass).
The thing is that the Sun is really spectacularly huge. You could fit over a million earth size planets inside of it. And it is a run away fusion reactor so it is kind of like throwing frozen beer cans into a 500 acre California wildfire. Very little effect on the fire (although any embedded Hot Shot firefighters will appreciate your effort).
But things are even easier than actually hitting the Sun in this case. If you're trying to just screw up the Earth, any rogue planet that flew through the Solar system and pulled earth more than about 6 - 8% off its existing orbit should completely wreck the climate. If you were a fiction writer you'd want it to be bad enough that people could survive long enough to write a story about it or course.
Generally though any astronomical mass that would nominally qualify as a planet flying within a million miles of the Earth is going to likely trigger an extinction level event. Especially if it is off the ecliptic by some amount.
For our planet's distance from the sun, I have a hard time imagining how anything without self propulsion could maintain a stable orbital position to cast a shade over us for a long enough period (e.g. a month).
Too bad it isn't regularly updated anymore.
> A "planet" is a celestial body that: (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.
> A "dwarf planet" is a celestial body that: (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.
> All other objects, except satellites, orbiting the Sun shall be referred to collectively as "Small Solar System Bodies".
Or search with the title, the author republishes his articles later.
It would be great if HN had an auto-archive feature now that more people are becoming privacy conscious.