Do you think we are alone in the Milky Way?

[caballerodiez]

So.. recent estimations for the Drake Equation (Maccone, 2012) suggest that there could be around 4,600 civilizations in our galaxy that are able to release detectable signals.

I find this number a little bit excessive, so I plugged some of the values of our Solar System into the equation and I obtained a smaller yet more realistic result, in my opinion: 50 civilizations.

Just in case someone is interested, I made a video showing the values I used: youtu.be/j2AIWIcn7Ig

Do you think 50 is a more realistic number?

[magnemoe]

Yes 4600 is an decent amount at least if expansionists. 

Note that detectable signals is a bit questionable. We are reducing the numbers of high power radio sources for lots of low power ones as it give more bandwidth. 
High power ones tend to be stuff like search radars who is short term and don't carry data. 
Imagine the WOW signal was an targeting radar either toward some villain or search and rescue or just mapping an asteroid. it would never repeat in that exact direction. 

[Green Baron]

Unfortunately the Drake equation has no empirical basis and cannot be used for conclusions, wikipedia has it as a "probabilistic argument", which imo hits the point quite well. It can be used in the media, or to talk money out of potential sponsors.

 

A heated discussion on the topic took place here some time ago:

 

Edited March 1, 2019 by Green Baron

[sevenperforce]

The math is tricky. In theory, if the chance of a civilization have the urge and the capacity to expand is nonzero, then that bleeding edge of the bell curve will breed new expanding civilizations like wildfire. But that breaks down if the child civilizations decide not to expand.

[Green Baron]

... or if civs just do not emerge like mushrooms, and if they do they soon reach a carrying capacity and go headlong, or if the whole concept of interstellar space travel is just a concept that is too hard or impossible to realize, which still is a pretty good bet, imo, as sorry as i am about it ...

Missing data ...

Edited March 1, 2019 by Green Baron

[MinimumSky5]

I seriously, sincerely think that we are  alone in our supercluster, let alone galaxy. 

It makes no evolutionary sense for a species to just stop expanding its numbers, as nature is simply not kind to those who stop trying to (yes, that is fairly irrelevant to an advanced civilisation, but by the time they are spacefaring, they'd have spent billions of years having this baked into their instincts and psyche.)

Even if they do stop, would all civilisations stop, enerringly, every time? Would everyone in that civilisation stop having more children than nessasary to maintain themselves? With no exceptions? 

 

IMHO, Rare Intelligence means that there likely is no extraterrestrial civilisation for us to reasonable meet. 

[kerbiloid]

I believe, there are just several small bubbles in the Milky Way

Spoiler

appropriate for the life self-development:

• enough far from the radiation hell of the bulge;
• enough far from the rim to still have the heavy elements;
• between the galactic arms and their radiation, co-rotating at the same angular speed as the arms to stay in this gap at least for a billion years;

Looking at the galaxy map, about 1000 ly in size.

Lonely yellow dwarves, outside of star clusters.
An Earth-mass planet +/- 50%, in a habitation zone.
With a massive moon and tilted for ~20°.
With water and oxy+nitro air.

Unlikely there can be more than one such planet near such star in such place of the galaxy.

So, we are probably the only such thing in this galaxy, unlikely the closest dwarf galaxies have better chances.

Spoiler

But as I can't see the ancient people making and transporting 1000 t heavy monoliths of Baalbek, polishing huge stone blocks of Great Pyramids across several rows at once (while the real local pyramids are puny heaps of clay bricks), and cutting these stone blocks making a stone lego, I guess somebody else has done this.

And as Sphinx is definitely a human design, not a sapient insect's, I can't currently see another option except another hi-tech civ using captured adopted humans like pets.

So, I believe there are at least two of us, until we become a single hivemind.

 

[linuxgurugamer]

25 minutes ago, kerbiloid said:

I believe, there are just several small bubbles in the Milky Way

  Reveal hidden contents

appropriate for the life self-development:

• enough far from the radiation hell of the bulge;
• enough far from the rim to still have the heavy elements;
• between the galactic arms and their radiation, co-rotating at the same angular speed as the arms to stay in this gap at least for a billion years;

Looking at the galaxy map, about 1000 ly in size.

Lonely yellow dwarves, outside of star clusters.
An Earth-mass planet +/- 50%, in a habitation zone.
With a massive moon and tilted for ~20°.
With water and oxy+nitro air.

Unlikely there can be more than one such planet near such star in such place of the galaxy.

So, we are probably the only such thing in this galaxy, unlikely the closest dwarf galaxies have better chances.

  Reveal hidden contents

But as I can't see the ancient people making and transporting 1000 t heavy monoliths of Baalbek, polishing huge stone blocks of Great Pyramids across several rows at once (while the real local pyramids are puny heaps of clay bricks), and cutting these stone blocks making a stone lego, I guess somebody else has done this.

And as Sphinx is definitely a human design, not a sapient insect's, I can't currently see another option except another hi-tech civ using captured adopted humans like pets.

So, I believe there are at least two of us, until we become a single hivemind.

 

Unlikely?  Do have any idea how many stars are in the Milky Way alone?

Between 100 Billion and 400 Billion (https://asd.gsfc.nasa.gov/blueshift/index.php/2015/07/22/how-many-stars-in-the-milky-way/)

 

Edited March 1, 2019 by linuxgurugamer

[kerbiloid]

10 minutes ago, linuxgurugamer said:

Unlikely?  Do have any idea how many stars are in the Milky Way alone?

Between 100 Bullion and 400 Billion

In the small regions of the Milky Way like the described above, with Earth-like planets and Moon-like moons?

The question is not in the total number of planets, but in the number of the planets enough stable for a billion years, but with properly tilted equator and a proper Moon to force the evolution.

Edited March 1, 2019 by kerbiloid

[linuxgurugamer]

1 minute ago, kerbiloid said:

In the small regions of the Milky Way like the described above, with Earth-like planets and Moon-like moons?

I have no idea, but the word "unlikely", when applied to the sheer number of stars, is rather meaningless.

Of course, now we can get into a (cordial) debate about life, etc.  :-)

[Bill Phil]

Even if we aren’t alone contact is virtually impossible, as it stands now. Not only is there a lot of space but also a lot of time. There may be millions of civilizations in the lifetime of the Milky Way( or even Milkomeda) but over billions of years of time. The likelihood of contact is tremendously low, and made lower by the possibilities of different technologies in use for communication, though we may detect other civilizations based on waste heat and other things. But there’s a good chance that they’re already dead... or will be by the time we show up if we can manage a visit.

Spacetime is just too big...

1 minute ago, kerbiloid said:

In the small regions of the Milky Way like the described above, with Earth-like planets and Moon-like moons?

Well we have found G-type stars that have Jupiter size gas giants at  a similar distance from its star, so it isn’t impossible. But other star types may play host to potentially habitable worlds as well.

[kerbiloid]

4 minutes ago, linuxgurugamer said:

Of course, now we can get into a (cordial) debate about life, etc.  :-)

It's night here, so not now.

2 minutes ago, Bill Phil said:

Well we have found G-type stars that have Jupiter size gas giants at  a similar distance from its star, so it isn’t impossible. But other star types may play host to potentially habitable worlds as well.

How many of them contain Earth-like planets at proper place, properly tilted and mooned?

P.S.
Though your optimism inspires, gentlemen. The more hi-tech neighbors, the less work for the poor Ancient Egyptians.

Edited March 1, 2019 by kerbiloid

[sevenperforce]

You don't need an Earth-like planet or a Moon-like moon. 

There are a lot of things that are unique to Earth that impacted how life evolved but would not necessarily be necessary for life to evolve.

I like the way Bill Nye presents it. We can look at our own history and see that we crossed several critical thresholds. We jumped from non-life to life. We jumped from single-celled to multicellular. We evolved social existence. We evolved intelligence. We looked to the stars. 

The trouble, Bill Nye explains, is that we don't know how hard it was to cross each of those thresholds. Perhaps it is very easy to evolve social existence but it is vanishingly unlikely to make the far earlier jump from single-celled life to multicellular life. On a million other Earthlike worlds there could be entire oceans filled with emergent-social colonial microbial life but not a single multicellular organism. Or perhaps the challenging threshold is in the future...it could be that our attempts to move beyond where we are now simply will never bear fruition because space is too big and lifetimes are too finite. We don't know.

So any sort of mathematical estimate is poor because all those leaps are too uncertain.

[mikegarrison]

One of the major problems with this sort of thing is that we assume we are the pinnacle of evolution and that we're looking for other people just like us.

Humans have been around for maybe a few hundred thousand years. Crocodiles have been around for millions of years. So which is the more successful species? Maybe other planets out there are filled with species that reached their own evolutionary stability without developing any signals that would reach us

[Green Baron]

Yep. Or in simple words: microbes may not be a big deal, a billions of years lasting constant evolution surely is.

We do not know if there are other mechanisms that provide a long term stability than the ones we observe for our case. A moon may not be necessary, but it helped maintaining stability. Gas giants may not be necessary, but it helped keeping the lawn clean(er). Tectonics may not be necessary, but without we'd need other mechanisms to provide and renew the elements on the surface.

But this is all speculation.

Edited March 1, 2019 by Green Baron

[tater]

A useful read on the subject (Drake equation in the context of the Fermi Paradox):

https://arxiv.org/pdf/1806.02404.pdf

 

The Fermi Paradox is only a paradox if there are a decent number of technological civilizations in the galaxy, since the crossing time at even low velocities should indeed result in paradox. The number could be quite low, making observation much less likely.

Another reason that I think is outside the scope of the current Drake Equation is AGI. I think that artificial general intelligence is possible. I would not presume to predict when, but it need only be possible to matter here. This results in a near certainty of von Neumann machines at the very least expanding across the galaxy for any sufficiently advanced civilization at the very least as probes (not paper clip maximizers). If we could build them now, to report back to us on the universe, we'd certainly want to do this, just as we look for exoplanets humanity will likely never visit.Send a couple such probes out, and let them make more, and report back. Anyway, this makes the "paradox" seem more like an observation, IMO.

There's always the chance the galaxy might be full later, and the first civilizations are only starting to appear around the same time we did.

Who knows.

[cubinator]

I wouldn't be surprised finding critters deep under Europan or Enceladian ice, in their oceans. But something similar enough to us that we can begin to hold a conversation? I wonder if one per galaxy is accurate.

[sevenperforce]

1 hour ago, cubinator said:

I wouldn't be surprised finding critters deep under Europan or Enceladian ice, in their oceans. But something similar enough to us that we can begin to hold a conversation? I wonder if one per galaxy is accurate.

Microbial life on the moons of our solar system is almost a better shot than not. We might not encounter it, but the odds are pretty good.

One per galaxy or one million per galaxy; all we know is that we've only met one yet.

2 hours ago, Green Baron said:

We do not know if there are other mechanisms that provide a long term stability than the ones we observe for our case. A moon may not be necessary, but it helped maintaining stability. Gas giants may not be necessary, but it helped keeping the lawn clean(er). Tectonics may not be necessary, but without we'd need other mechanisms to provide and renew the elements on the surface.

Indeed. We make a mistake if we suppose that all our particulars are necessary, but we cannot discount the peculiarities.

There may be many many other equally-rare peculiarities which could lead to intelligent life, but we don't know how many.

[YNM]

Drake Equation is an equation with no limits on the number of quotients that it can have, no known data on each quotient, and no known bounds of its result.

You may as well pee in the wind.

Edited March 2, 2019 by YNM

[Jacke]

I really think we may be the only intelligent life form that exists.

What I think it comes down to is intelligence requires the complexity of Eukaryotes and that seems to be a far rarer occurrence than the formation of simpler life like bacteria.  The critical step seems to be that the primitive ancestor of the Eukaryotes took in a protobacteria that became the mitochondria, the cell powerhouse.  At some other time some of them took in a protocyanobacteria that became the plastid, the photosynthetic powerhouse.  And at a later time, the ancestors of Heterokonts (including brown algae) took in another algae and that's the source of their different four-walled plastids that do photosynthesis for them.

Simple bacteria-like life appeared under a billion years after the Earth had a livable environment.  But Eukaryotes took billions of years more.  And the successful events that formed them only appears to have happened 3 times.  2 of which were vital to forming a successful set of Eukaryotes.  And within a billion years of that, a massive increase in the complexity of life.

[GDJ]

10 hours ago, caballerodiez said:

So.. recent estimations for the Drake Equation (Maccone, 2012) suggest that there could be around 4,600 civilizations in our galaxy that are able to release detectable signals.

I find this number a little bit excessive, so I plugged some of the values of our Solar System into the equation and I obtained a smaller yet more realistic result, in my opinion: 50 civilizations.

Just in case someone is interested, I made a video showing the values I used: youtu.be/j2AIWIcn7Ig

Do you think 50 is a more realistic number?

 

9 hours ago, magnemoe said:

Yes 4600 is an decent amount at least if expansionists. 

Note that detectable signals is a bit questionable. We are reducing the numbers of high power radio sources for lots of low power ones as it give more bandwidth. 
High power ones tend to be stuff like search radars who is short term and don't carry data. 
Imagine the WOW signal was an targeting radar either toward some villain or search and rescue or just mapping an asteroid. it would never repeat in that exact direction. 

I consider both answers plausible, from my point of view.

Even with 4600 civilizations, with all of them spread evenly across the known galaxy, that's a lot of space to cover.

[cubinator]

2 hours ago, Jacke said:

Simple bacteria-like life appeared under a billion years after the Earth had a livable environment.  But Eukaryotes took billions of years more.  And the successful events that formed them only appears to have happened 3 times.  2 of which were vital to forming a successful set of Eukaryotes.  

Then it happened three times on one planet alone. This really could swing either way.

[kerbiloid]

9 hours ago, sevenperforce said:

You don't need an Earth-like planet or a Moon-like moon. 

You probably do.
Planets a little smaller than Earth have poor chances to keep atmosphere and ocean, and to have a long geological history.
Planets a little bigger most probably become supervenuses.

Non-tilted planets don't have seasons (which force the evolution).

Planets without a big moon don't have tides (which force the evolution) and probably active geology and continents (look at Venus), as their core differentiates much slower.

9 hours ago, sevenperforce said:

I like the way Bill Nye presents it. We can look at our own history and see that we crossed several critical thresholds. We jumped from non-life to life. We jumped from single-celled to multicellular. We evolved social existence. We evolved intelligence. We looked to the stars. 

The critical trouble of his logical sequence is "jumps". Nothing jumps, it evolves. We call "jump" that what we don't clearly see how it evolved.

9 hours ago, sevenperforce said:

Perhaps it is very easy to evolve social existence but it is vanishingly unlikely to make the far earlier jump from single-celled life to multicellular life.

Invasion of one prokaryotes into another became a symbiosis and created eukaryotes.
Stromatolith caused the sticky mess of eukaryotes to differentiate their functions but to keep together.
Later, when the rocky non-organic coastline got crapped with humus and strengthened with plants, and the rivers made bogs, the life walked from the water had to survive between the water pools.
Then a revolver made them equal.

9 hours ago, sevenperforce said:

So any sort of mathematical estimate is poor because all those leaps are too uncertain.

Mathematical estimate and astronomy can limit the conditions where a life (a real life, like in the Hollywood films, not in the films of microbes on the stones) has chances to evolve, and estimate a number of such planets.

Btw compare ratio of the mass of the Earth and the mass of the Earth biomass. Why should the Galaxy be more life-friendly?

7 hours ago, mikegarrison said:

One of the major problems with this sort of thing is that we assume we are the pinnacle of evolution and that we're looking for other people just like us.

Any sapient species is appropriate, not necessary an omnivorous tree insectophagus.

7 hours ago, mikegarrison said:

Humans have been around for maybe a few hundred thousand years. Crocodiles have been around for millions of years. So which is the more successful species?

Spoiler

That one who limits the extinction of another one because finds it useful.

A sapient species changes the medium, non-sapient are changing themselves. The latter has its limits. The former has them much wider.

7 hours ago, mikegarrison said:

Maybe other planets out there are filled with species that reached their own evolutionary stability without developing any signals that would reach us

The question is not in signals. The question is just in their crocodile shoes and bags. Can they become at least savages.

6 hours ago, Green Baron said:

Yep. Or in simple words: microbes may not be a big deal, a billions of years lasting constant evolution surely is.

Exactly.

6 hours ago, Green Baron said:

We do not know if there are other mechanisms that provide a long term stability than the ones we observe for our case. A moon may not be necessary, but it helped maintaining stability.

Moon doesn't just maintain the stability, that's the thing.

1) It provides a stable instability with clear periods (the tides, which force the coastal creatures twice per day struggle against drying and against drawning).

2) Originally a planet doesn't rotate fast and tilted, originally it's lazy and non-tilted like Venus. The Moon, not just moonlets, is a trace of an ancient interaction causing the equator tilt and the fast rotation.
The fast rotation is required to force the evolution with short-term stable periodical instability (day-night change).
The equatorial tilt provides the long-term stable periodical instability (seasons change).

All these stable periodical instabilities force the happy and lazy monocellulars keep struggling against the light/darkness, hot/cold, drying/flooded, and so on.
And make this under clear and predictable rules, not chaotically. So, cause the rhythmic biological processes.

3) The Moon presence means the ancient cataclysm forcing the geology, the core differentiation. Otherwise look at Venus.

As we can see, even under this pressure it took billions years for the Earth life to evolve from the prokaryotes to the KSP players.
So, yes, these conditions are not "absolutely required", and probably a life could evolve after a trillion years, no problem.

The problem is that the planet and the star have limited lifetime: the planet geology, and the star luminosity.
So, either you do this in 1-2 billions, or still stay a microbe when the planet dies.
Remember that the Earth life started, say, 4 bln years ago, and has just 0.5 bln till the greenhouse death, and 1.5 bln till the geological death.
So, the nice and wise we have appeared when the progress bar was already 90%.

Of course, there should be a lot of planets with microlife. But it's interesting only for the biologists. While we are probably talking about the life which you can either pet, or consume in other way, not just as a nutrition microflora.

5 hours ago, cubinator said:

I wouldn't be surprised finding critters deep under Europan or Enceladian ice, in their oceans.

I would expect more life in a glass jar of brine forgotten in a dark dungeon.

3 hours ago, sevenperforce said:

Microbial life on the moons of our solar system is almost a better shot than not. We might not encounter it, but the odds are pretty good.

The hopes are pretty good, not the odds.
A dark pool without any income of organics from top (where the food for the terrestrial bottomlings gets created), very salty.
And many times smaller than Earth, so on Earth you have, say, 1000 oceanic oases where the life can appear, while on that moons, for hundreds times less, just because their total bottom surface is tiny compared to the Earth ocean.

P.S.
And yes, I'm a water-oxygen-carbon chauvinist pig.

Edited March 2, 2019 by kerbiloid

[Green Baron]

3 hours ago, kerbiloid said:

And yes, I'm a water-oxygen-carbon chauvinist pig.

Most of us are, i'd say. The elements aren't rare and they are well-, maybe best-suited for the "job".

The paper @tater linked is really a good read. Filling uncertainties with speculations (that's what these equations do) and assuming the existence before looking at the detail is not helpful.

We understand the processes on earth quite well and have a reasonable overview from ~3.7Gy to now, though many things are in discussion and flow. Besides the availability of the necessary elements physics are the same everywhere. So assuming similar processes isn't totally unreasonable, though speculative. Only, there is no new insight in going that path, before we actually find or detect something real that then would need explanation. It only leads to nonsense like megastructures that blur the view on reality.

imo

Edited March 2, 2019 by Green Baron

[Cassel]

16 hours ago, caballerodiez said:

So.. recent estimations for the Drake Equation (Maccone, 2012) suggest that there could be around 4,600 civilizations in our galaxy that are able to release detectable signals.

I find this number a little bit excessive, so I plugged some of the values of our Solar System into the equation and I obtained a smaller yet more realistic result, in my opinion: 50 civilizations.

Just in case someone is interested, I made a video showing the values I used: youtu.be/j2AIWIcn7Ig

Do you think 50 is a more realistic number?

Only 50? On Earth you have few civilizations, so on entire galaxy should be a lot more ;-)

https://en.wikipedia.org/wiki/File:Clash_of_Civilizations_mapn2.png