Space Is Full of Planets, and Most of Them Don't Even Have Stars • Hacker News Board

Re: Space Is Full of Planets, and Most of Them Don't Even Have Stars

#141

Post by doikor » Wed, May 30, 2018, 2:15 PM UTC

lmm wrote: post #105

Has the IAU come around to a sensible definition of "planet", or are these officially non-planets?

Current definition requires the object to be orbiting the Sun (and only the Sun not other stars) so by IAU definition these are not planets.

> 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".

Re: Space Is Full of Planets, and Most of Them Don't Even Have Stars

#142

Post by gnarbarian » Wed, May 30, 2018, 2:23 PM UTC

varjag wrote: post #89

nabla9 wrote: post #41

Earlier quoted context omitted.

> ~17 planets in every cubic light year. The change of hitting one while traveling one light year is in the order of 10e-16.

About the same as getting shot while drowning in bathtub stricken by lightning?

That's how my uncle died.

Re: Space Is Full of Planets, and Most of Them Don't Even Have Stars

#143

Post by ddevault » Wed, May 30, 2018, 2:25 PM UTC

m_mueller wrote: post #91

hyperpallium wrote: post #75

Earlier quoted context omitted.

If you're a fan of Moore's Law and the Singularity, you'll love the reasoning of backtrapolating the exponentially increasing complexity of life over time... to get 0 well before the formation of the earth https://www.technologyreview.com/s/513781/moores-law-and-the...

What about Fermi's paradox though? I mean, where is everyone?

Never forget to include the Bs term when considering the Drake equation: https://www.xkcd.com/384/

Re: Space Is Full of Planets, and Most of Them Don't Even Have Stars

#144

Post by whatshisface » Wed, May 30, 2018, 2:26 PM UTC

Aaargh20318 wrote: post #132

pavlov wrote: post #113

Earlier quoted context omitted.

The default for unintelligent life is to survive at all cost and fill every niche. You're suggesting that intelligence flips that purpose so that every sentient species eventually becomes depressed suicidal existentialists?

Not depressed or suicidal, just realising they have no right to gamble with another human being's life.

An honestly held belief that their child would have a miserable, depressed, ill life I could understand - especially because those traits can be heritable. I can also understand sour grapes. However the other arguments seem very ill-motivated.

Re: Space Is Full of Planets, and Most of Them Don't Even Have Stars

#145

Post by GuB-42 » Wed, May 30, 2018, 2:28 PM UTC

senectus1 wrote: post #2

I wonder what happens to the planets in the solar system when a rogue planets gets sucked into the star (sun) ? 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…

It sounds like a perfect question for XKCD's what-if? (https://what-if.xkcd.com/)

Too bad it isn't regularly updated anymore.

Re: Space Is Full of Planets, and Most of Them Don't Even Have Stars

#146

Post by tiemand » Wed, May 30, 2018, 2:28 PM UTC

rpedela wrote: post #130

perl4ever wrote: post #19

Based on the inverse correlation between star size and frequency, this doesn't surprise me at all. 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…

I generally don't like the assumption that life had to come from space because we don't know how life is created and it appeared so soon in the history of Earth. That is certainly a possibility, but it also possible that creating life from chemistry is easy. Just because we haven't figured it out yet doesn't mean it is hard. Obviously figuring out how it works is hard, but the mysterious mechanism may be simple.

One problem I have with pan-spermia is: Why is there only one tree of life? Not several independent trees. If life evolved in one of the exo-planets, is not possible that several independent forms of life evolved in several planets and some ended up on Earth.

Re: Space Is Full of Planets, and Most of Them Don't Even Have Stars

#147

Post by antisthenes » Wed, May 30, 2018, 2:32 PM UTC

vorg wrote: post #124

brazzy wrote: post #56

Earlier quoted context omitted.

Quite the opposite, actually. At near lightspeed, a pea-sized rock will kill your spaceship just as dead as a planet. So you actually want your interstellar masses to be as concentrated as possible.

> At near lightspeed, a pea-sized rock will kill your spaceship 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…

Powered by what?

Re: Space Is Full of Planets, and Most of Them Don't Even Have Stars

#148

Post by whatshisface » Wed, May 30, 2018, 2:32 PM UTC

hyperpallium wrote: post #97

DoctorOetker wrote: post #90

Earlier quoted context omitted.

you mean well before the big bang: e^(a*t) = 0 for t=-infinity

well yes; technically they use one base-pair as the origin of life (which is probably still a little too small). 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.

That goes below a discontinuity, 256 base pairs is well below the smallest organism ever observed. A single gene is on average around 10^4 bases, and the simplest organisms have around 10^3 necessary genes. Life below 10^3 base pairs may not evolve at the same speed. It's certainly not safe to talk about it in terms of base pairs, in that era there might not have even been any.

Re: Space Is Full of Planets, and Most of Them Don't Even Have Stars

#149

Post by maxerickson » Wed, May 30, 2018, 2:32 PM UTC

hyperpallium wrote: post #75

perl4ever wrote: post #19

Based on the inverse correlation between star size and frequency, this doesn't surprise me at all. 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…

If you're a fan of Moore's Law and the Singularity, you'll love the reasoning of backtrapolating the exponentially increasing complexity of life over time... to get 0 well before the formation of the earth https://www.technologyreview.com/s/513781/moores-law-and-the...

I wonder if scientists in the future will ponder how microchips were invented before the steam engine.

Re: Space Is Full of Planets, and Most of Them Don't Even Have Stars

#150

Post by nickwalton00 » Wed, May 30, 2018, 2:36 PM UTC

throwaway7312 wrote: post #112

m_mueller wrote: post #91

Earlier quoted context omitted.

What about Fermi's paradox though? I mean, where is everyone?

Uncontacted tribes in the Amazon likely wonder the same thing. It's such a big Earth, yet only a few hundred humans are known to exist. 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. Y…

A lot of these "uncontacted" tribes have actually had contact in the form of smugglers, loggers, drug cartels etc...many of those experiences ended with them getting killed so it's not surprising they would avoid us.