Billions and Billions of "Earths" in the Milky Way

[WestAir]

According to some scientists involved with the $550,000,000 USD Kepler Spacecraft, there may be a drastic prevalence of Earth-like planets in our Galaxy.

Like any knee-jerk reporter would do, CNN's Brad Lendon posted the findings to the main webpage of CNN.com, found here: http://www.cnn.com/2013/11/05/tech/innovation/billions-of-planets/index.html?hpt=hp_t2.

So what do you guys think? If we take the dubiousness of the findings as concrete fact, and if we take the estimation of 170billion+ Galaxies in our observable Universe to be fact, that potentially means 1.7 trillion "Earths" within our observable Universe. On the flip side, there are many intelligent scientists who can argue that we may be the only current life-bearing planet in the Milky Way due to the risks involved. Thoughts?

Edit: Changed title as a nod to Carl Sagan upon request.

Edited November 11, 2013 by WestAir

[czokletmuss]

I would just like to add these two videos:

Visual representation of what's been discovered

And some PR talk from Administrator Bolden about it

BTW is this a southern accent?

[brdavis]

According to some scientists involved with… Kepler… there may be a drastic prevalence of Earth-like planets in our Galaxy.

Well, yeah. It makes sense. Do a detailed search of a small area with a known number of stars, and a known observation bias (you only see transiting planets, and some stars are poor targets due to stellar phenomenon), and generalize from their. Not too different than estimating the number of blades of grass in my yard by counting the blades of grass in a single square meter and generalizing.

...If we take the dubiousness of the findings as concrete fact…

I don't think it's really that dubious. Peer-review sort of takes care of a lot of that.

On the flip side, there are many intelligent scientists who can argue that we may be the only current life-bearing planet in the Milky Way due to the risks involved. Thoughts?

I think (still) that the "Rare Earth Hypothesis" was poor when it was proposed… and the more we learn, the poorer it seems to be.

Upshot - there's a very very large number of terrestrial worlds located in the habitable zone of their stars (with a preponderance of them being tide-locked in all likelihood). That's… potentially a lot of real-estate.

--

Brian Davis

[Pds314]

Your math is very off. 170 Billion Times 8.8 Billlion is not 1.7 Trillion, but 1.5 Sextillion Earths.

[Sylandro]

There could also be trojan earths, too.

Anything can and will happen with planets in our universe, too.

[Simon Ross]

According to some scientists involved with the $550,000,000 USD Kepler Spacecraft, there may be a drastic prevalence of Earth-like planets in our Galaxy.

Like any knee-jerk reporter would do, CNN's Brad Lendon posted the findings to the main webpage of CNN.com, found here: http://www.cnn.com/2013/11/05/tech/innovation/billions-of-planets/index.html?hpt=hp_t2.

So what do you guys think? If we take the dubiousness of the findings as concrete fact, and if we take the estimation of 170billion+ Galaxies in our observable Universe to be fact, that potentially means 1.7 trillion "Earths" within our observable Universe. On the flip side, there are many intelligent scientists who can argue that we may be the only current life-bearing planet in the Milky Way due to the risks involved. Thoughts?

In truth, I cannot see what is remotely dubious about the conclusion of the article. We know from scientific observations that planetary systems exist around many stars, and through the process that those systems are formed by, it is inevitable that a percentage of 'earth like' planets are going to form within an orbit that will allow liquid water to exist on the planet's surface.

However !!! An earth like planet, is not the same as a life bearing planet. An easy example is Venus, very much an earth like planet in terms of size and composition and according to certain models, actually sits on the edge of our 'Goldilocks' zone, yet no one is expecting to find life there.

[Moon Goddess]

I think we may sadly be discovering that the answer to the Fermi Paradox isn't they aren't out there. The answer may be simply FTL travel and communication are impossible and STL communication and travel are simply so difficult to be impractical.

Imagine if we discover that there are tons of other intelligent species out there, but it's just to hard to ever communicate with them and too hard for them to communicate with us, so we'll know that they are there, but that's it.

[magnemoe]

I think we may sadly be discovering that the answer to the Fermi Paradox isn't they aren't out there. The answer may be simply FTL travel and communication are impossible and STL communication and travel are simply so difficult to be impractical.

Imagine if we discover that there are tons of other intelligent species out there, but it's just to hard to ever communicate with them and too hard for them to communicate with us, so we'll know that they are there, but that's it.

Radio communication has the problem that somebody has to transmit and listen at the same time.

As we move away from the huge TV transmitters and more over to Internet and cell based communication it will be harder to detect us.

yes you still have directional signals but you has to be lucky to catch them, more lucky to get an long enough message to know its artificial and target it.

it would be easier to find planets with an oxygen atmosphere first and then focus on them.

Interstellar travel should be possible but very expensive, high chance that most civilizations don't do it.

Or they send out some probes, perhaps even colonized some other star systems however as planets you can live on is average 20 light year away they run out of targets. Or they found themselves blocked as the distance to the next one was to far.

[Ralathon]

I think we may sadly be discovering that the answer to the Fermi Paradox isn't they aren't out there. The answer may be simply FTL travel and communication are impossible and STL communication and travel are simply so difficult to be impractical.

Imagine if we discover that there are tons of other intelligent species out there, but it's just to hard to ever communicate with them and too hard for them to communicate with us, so we'll know that they are there, but that's it.

Even if FTL travel and communication isn't possible this wouldn't explain the fermi paradox. If we started to migrate outward at an average speed of just 0.1% of c today we would've filled half the milky way in just 50 million years. That's the blink of an eye in cosmological terms. So we only have the following options:

1 - There are a lot of alien civilizations out there, but not one of the millions of civilizations has ever managed to migrate outward.

2 - We are alone, or at least one of the very first sapient species.

3 - They are out there and have spread among the stars. But they're either actively or accidentally avoiding or ignoring us.

But all of them have problems:

1 - It's sensible to avoid colonies and migrations from an economics perspective. We all love space travel on this forum, but lets be honest: it is very resource intensive to send living things anywhere, let alone in large numbers. However, it seems unlikely that not one of the thousands of species that should've existed was ever faced with extinction. If your choice is "Migrate or die!" because your sun is going nova the choice seems rather easy. And if your entire species is spaceborne anyway it seems like a shame to settle down permanently. You've got resources galore from asteroids and you've solved any problems you might have with long term 0G. Why make yourself vulnerable again by all settling down on a single planet?

2 - Well someone has to be the first right? And we seem to have either a second generation or 3th generation star, so on a universal scale we're about as early as can be. But on earth it took 3 billion years before we even got multicellular life, let alone intelligence. If there is intelligent life on thousands of other planets they have a lot of leeway in terms of time. And as said before, if someone decides to migrate outward they'll be everywhere in the blink of an eye.

3 - This seems the likely scenario to me. Our radio signals are indistinguishable from background radiation within a few lightyears. Also, it seems that birthrates tend to go down as technology progresses. If the same applies to aliens then they wouldn't spread across the galaxy, just settle on a few planets around long lived stars and enjoy life without population pressure forcing you outward. If there are a thousand species all with 20 or so planets then the milky way will still seem completely void of intelligent life. It'd be 100s of lightyears to the nearest civilization. Since pumping out extremely strong radiosignals isn't exactly an efficient usage of resources they'd be just as invisible to us as we are to them. However, it is dangerous to assume that observations made on humans apply to aliens. It seems kinda unlikely that thousands of civilizations behave the same as ours...

[KerikBalm]

Suppose that Fusion power is achievable and practical (I'm very optimistic about Dense Plasma focus designs).

A spacecraft with a Propellant: total mass ratio similar to the Saturn V, propelled by a fusion powered design, would be able to achieve speeds of a significant fraction of the speed of light (like 20% !!!).

The galaxy is only 100,000 light years across... if you can get a spacecraft going 20% of the speed of light... suppose they save some delta V, and average 10%.... thats across the galaxy in a Million years.... life has been here on Earth for roughly 4,000 million years.

Suppose during that time that they get bussard ramjets (at least for braking after accelerating using fusion propellant, allowing them to use more to accelerate and less to decelerate)... they'd likely get even faster speeds.

Of course, speed to traverse the galaxy is not the speed it takes to colonize it.... lets assume that they spend roughly 10x as much time developing a colonies, as they do traveling to establish new ones (not unreasonable when traveling even at 10% the speed of light means voyages of hundreds of years)... 10 million years for a space faring civilization with fusion power to colonize the galaxy.

Considering how easy it would be to move about a solar system with fusion, they may prefer asteroid belts and small moons to planets with large gravity wells - a completely space faring civilization - They could be everywhere, and they wouldn't need to hide their presence... like a single planet species might want to ensure its not discovered (as another single planet species may decide to kill it with a KE impactor to eliminate the threat, before the same thing happens to them).

There's plenty of time for aliens to visit, and there's little reason to hide.

Also consider:

* The first generation stars, and their planetary systems would be deficient in the heavier elements needed for life.

* The conditions at which life can exist, are not necessarily the same as those which allow for abiogenesis to occur (indeed, if the "radioactive beach" hypothesis is correct, and the major contributor, life could be very rare)

* The conditions that allow for life are not the same as the conditions that allow for complex life possessing high metabolisms (Ie, even if Europa is habitable, no space faring life will evolve there

* Life may not necessarily evolve in the direction of intelligence. There wasn't really any major evolutionary innovation between the end of the Permian, and now, as far as I can tell (ie, high metabolism, limbs that could be easily adapted to manipulate objects, brain structures), yet 300 million years passed before we have a species that has a chance at achieving fusion powered (or better, ie, antimatter) space flight.

* The "habitable zone" around red dwarfs (by far the most common star type) means any planet there would be tidally locked... meaning no thermal cycling from day and night cycles (may have been important in abiogenesis). It also means that the atmosphere will need to be pretty thick, or almost entirely absent .... the night side will be extremely cold, and the atmosphere will freeze on the night side, and be locked away in icy deposits... or the atmosphere will need to be thick enough for sufficient heat transfer/insulation to prevent this

* The emission spectrum of red dwarfs is primarily in the infra red, combined with the requisite thick atmospheres, and absorption spectra of gasses, there will be little opportunity for direct photosynthesis, which will limit the complexity of life there, and its not unreasonable to think that these conditions preclude space faring life.

*larger stars burn out faster... for 3.5 out of nearly 4 billion years of life on earth, we didn't even have macroscopic multicellular life. This is an exceedingly long time frame, and given the replication time and expected diversity of life at that scale (its not like we're sampling only mammals, and looking for something very specific like verbal communication with grammatical structure), so I'd say on other earth like planets, its probably going to take a similar time - although this time is likely highly altered by the prevalence of extinction events - you want enough to break out of evolutionary local maxima, but no so many that ecosystems and diversity are constantly collapsing.

* Our star only has about another billion years or so before its output increases to the point that Earth will be hostile to complex life. Life on Earth has gone 80% of the way through the usable life time of our star, without producing a space faring species. We have a chance to be that species... but it also seems likely we may wipe each other out, and set earth's ecosystem and life back so much it may be another 300 million years.... given our use of fossil fuels, I'd say we're Earth's only shot, and we're perpetually 1 major war away for annihilation.

* Any civilization that decides not to expand, will be at a severe disadvantage to one that does expand. There will be strong selection pressure towards expansion (just like there was towards self replication during abiogenesis)

Given the lack of heavier elements, we can conclude life likely didn't arise until billions of years after the big bang - when enough stars had gone super nova.

We can also assume that it would be another 2-6 billion years for life to evolve to become space faring (assuming we are on the threshold, and applying a +/- 50% time scale to our own) - which may be too long.

I'd say generally only G and K type stars would have a chance of producing spacefaring life.

Given the time frames, its not unreasonable to think that we're one of the first (in the cosmic time scale) in our galaxy. Even if we take the metallically requirements and evolution rates into account.... I still see no reason we couldn't have had space faring life in our galaxy a billion years ago.... so If that life takes 10 million years to spread throughout the galaxy. That still leaves it as a 1% chance that we are here during the "expansion" phase of another civilization. So lets say thats unlikely.

That means - there are no other space faring civilizations that possess fusion drives in our galaxy, or they're leaving us alone and we can't detect them.

I think its highly likely that a species that gets to our technology level either a) destroys itself, or develops fusion power very rapidly (cosmologically speaking, even if its 10,000 years from now).

Thus, a variant of "the rare Earth hypothesis" is what I conclude to be the most likely to be correct.

[Monkeh]

The chances of an interesting alien species evolving in the time frame we could observe them and still being around now makes the chances of us finding them very remote if they are out there.

The rare Earth theory has gained a lot of foothold in the portion of my brain that still works. All the little things that happened to bring our Earth to safely evolve life are many and compound. The large gas giant, the biggest moon in the solar system in relation to planet size, all those tides and seasons are vital to life, the dinosaur killer, the iron core, the goldilocks zone, the stable sun, the single sun system giving stable orbits, the cue ball earth getting melted due to volcanism...the list goes on and on and it makes very interesting reading. I feel life such as ours is special, probably not unique in our time frame but very, very special.

I doubt there are many intelligent species out there right now, if any and the chances of us blundering into each other are miniscule.

[frizzank]

I'm in the boat that it is a bad idea to broadcast our primitive, resource rich existence for all to hear. At least until we can be technologically advanced enough to not be worth the trouble of enslaving.

All hail our alien overlords!

[WestAir]

I believe there are a lot of alien worlds out there with semi-intelligent to intelligent to hyper-intelligent life. I also believe the distances involved here (on the order of thousands of years just to exchange photons) makes any communication, or even mutual understanding, an impossibility. Humanity exists now (in our relative view of the Universe). To the alien sentience on the opposite end of the spiral arm, the radio boom of the 20th Century won't happen for another twenty-seven thousand years.

So imagine they pick up our garbled transmissions, learn everything there is to know about us, and shoot back a reply. 27x2=54. So in the year 56,013A.D we'll get a reply back from these people.

How can anyone even begin to suggest humanity (in any form) will be here in 56,013? The only alien societies that communicate are ones in the same star system from different planets in the Goldilock zone, IMHO. Cross-System communication is done through observation only.

[KerikBalm]

You're assuming that species never leave their home system.

Any species that has mastered nuclear fusion will have the capability to colonize the entire galaxy in ~10 million years.

If there was some alien species, spread throughout the galaxy... munching/mining on rocks in orbit around Alpha/beta/proxima Centauri, communication with them would be quite easy.

So that means either: Earth like planets are very rare, or its very unlikely that we'll achieve controlled fusion before we destroy our planet, or are wiped out by some other event.

One a species has fusion powered spacecraft, I'd say they are very very likely to persist, I can't imagine any extinction event that would wipe out a species/civilization that spans multiple stars - short of a concerted extermination effort by another sentient species.

Either planets like ours are rare, or we're very very very likely doomed to self annihilation, or some combination thereof.

[Nibb31]

Even with fusion powered spacecraft, there is still the possibility that the light speed barrier is impossible to break. Unless their perception of time is vastly different from ours, it is likely that any alien species will find interstellar travel just as impractical as we do.

Of course, if they are beings that have a life span of 1000 years, then an interstellar hop would be just like a month's journey for us, but the fact that we don't see fusion-powered alien ships flying around our solar system suggests that interstellar travel might not so widespread.

Edited November 8, 2013 by Nibb31

[magnemoe]

You're assuming that species never leave their home system.

Any species that has mastered nuclear fusion will have the capability to colonize the entire galaxy in ~10 million years.

If there was some alien species, spread throughout the galaxy... munching/mining on rocks in orbit around Alpha/beta/proxima Centauri, communication with them would be quite easy.

So that means either: Earth like planets are very rare, or its very unlikely that we'll achieve controlled fusion before we destroy our planet, or are wiped out by some other event.

One a species has fusion powered spacecraft, I'd say they are very very likely to persist, I can't imagine any extinction event that would wipe out a species/civilization that spans multiple stars - short of a concerted extermination effort by another sentient species.

Either planets like ours are rare, or we're very very very likely doomed to self annihilation, or some combination thereof.

Interstellar travel with fusion engines will be hard / slow, most species will not bother, same is true with most other slower than light travel.

Even more unlikely that they will continue outward with constant speed after reaching the closest stars the next wave has to come from the colonies after they have grown large enough to continue.

Self replicating probes has the option to move outward with constant speed but they are probes.

Yes you have the possibility of an machine intelligence who colonize the galaxy but we would notice that

Find it very unlikely that an system who reproduced uncontrollably either biological or machines would be able to get star travel.

This might be one of the stumbling blocks of any alien civilization, they might even have problem becoming an civilization, an species with no plants or animals suitable for domestication will never leave the hunter gather stage but would be the dominant species, an pure predator would have an far harder time here.

Intelligent life has only happen once on earth so we don't know how common it is at all, it took an decent time from we got advanced animals to humans evolved.

Now I think its unlikely we will destroy ourself unless its some future unknown dangers, this might not be true for an alien species.

Two scenarios could also happened on earth if we was unlucky, once you have nuclear weapons and long range fast communication you either end up in an low level constant nuclear war or a world state who clamps down on most research, both scenarios will be bad.

However even if you managed to get an advanced technical civilization it will be lots of other stuff to spend money on and entering the matrix is more fun.

The scary thought is that the ones who will do lots of interstellar exploring and colonization is the ones who do it for the emperor, the race and to spread the word of Om. Not the type of people you want to run into.

[KerikBalm]

"the fact that we don't see fusion-powered alien ships flying around our solar system suggests that interstellar travel might not so widespread."

Yes, it certainly suggests that... but the question is why is it not?

Is it:

1) Few planets actually suitable for life to arise/start? (habitable != conducive to abiogenesis)

2) Few planets actually suitable for complex life?

3) Evolution from simple (like single cells) life to complex (multicellular or syncytical for example) is infrequent or too slow given the life time of many stars?

4) Complex life rarely evolves into a species that establishes a technological civilization?

5) Technological civilizations rarely last long enough to achieve controlled fusion?

6) Civilizations that achieve controlled fusion rarely use it for interstellar travel?

If its not one of 1-5, then there should be multitudes of technological civilizations with controlled fusion, whom can at least colonize their local solar system, and thus are likely to be extremely long lasting. It seems incredulous to me that of these multitudes, not one has embarked on an expansionist phase. Therefore I conclude the problem lies somewhere in 1-5.

I'd say we're only a century or two away from controlled fusion.... and at that point we can begin sending drones carrying biological packages, etc, even if the voyage is too long for us. It would ensure our legacy, and it would also be conducive to defense... we'd start to establish a buffer zone between us an other potential alien civilizations... the best defense is a good offense and all that. If we start an expansion program, we're less likely to be swallowed by an alien's (for that matter, if we encountered aliens more primitive than us, I'd hope we'd study them, rather than exterminate them).

When you think of other possible technologies, like bussard ramjets, the travel time (especially due to time dialation), shrinks a lot. Then if you consider a civilization that has some sort of collective consciousness (borg like?), then its even more likely that they would find it worthwhile to expand.

Generally, the overall picture of life, is that it expands where it can. Why should technological civilizations be any different?

[Moon Goddess]

I'm in the boat that it is a bad idea to broadcast our primitive, resource rich existence for all to hear. At least until we can be technologically advanced enough to not be worth the trouble of enslaving.

All hail our alien overlords!

I don't understand this...

If someone has the tech to travel interstellar distances what could they possibly want from our gravity well.

I can see if we were higher advanced and could be seen as a threat simply knocking our planet into the sun, but theres just nothing on the planet that would be valuable.

[Nibb31]

If someone has the tech to travel interstellar distances what could they possibly want from our gravity well.

I can see if we were higher advanced and could be seen as a threat simply knocking our planet into the sun, but theres just nothing on the planet that would be valuable.

Maybe they preemptively destroy anything that might become a threat later. A bit like eradicating a small tumor before it turns into a generalized cancer. Because maybe it takes them hundreds of years to reach another solar system, and it that time, what appeared as a low level civilization has time to evolve into an interstellar threat.

This would explain why, although science and statistics suggest that there is a large number of planets that could support intelligent life, we have found no evidence of life or intelligent activity anywhere in the universe.

[WestAir]

Maybe they preemptively destroy anything that might become a threat later. A bit like eradicating a small tumor before it turns into a generalized cancer. Because maybe it takes them hundreds of years to reach another solar system, and it that time, what appeared as a low level civilization has time to evolve into an interstellar threat.

This would explain why, although science and statistics suggest that there is a large number of planets that could support intelligent life, we have found no evidence of life or intelligent activity anywhere in the universe.

In that case, there could be a missile heading our way right now to end our threat to interstellar civilization. A preemptive strike to ensure we never have a chance to become a threat.

A small rock launched at .8c would pretty much ensure our destruction; they never have to set foot on Earth or leave their home planet to do it.

[Mr Shifty]

I just think that technological intelligence is in no way an inevitable result of evolution. Complex life existed for 500 million years on Earth with no intelligence. Even in our own history, it's only in the last 100 years out of our 200,000 years as a species that we could conceive of technology that would make us visible from off-planet. Humans are also all very genetically similar; we experienced a dramatic population bottleneck around 70,000 years ago. We could easily be extinct now (all other hominin species are.) Our intelligence didn't protect us from that; it's not obvious that it's an evolutionary slam-dunk. My suspicion is that there are myriad worlds with life, but very very few with intelligence.

[Moon Goddess]

In that case, there could be a missile heading our way right now to end our threat to interstellar civilization. A preemptive strike to ensure we never have a chance to become a threat.

A small rock launched at .8c would pretty much ensure our destruction; they never have to set foot on Earth or leave their home planet to do it.

This ^

There's 2 things that could happen with aliens, peaceful encounter or destroyed from a distance without ever seeing what is coming.

Aliens come to take our minerals/water/women/whatever is so laughable.

[KerikBalm]

"Aliens come to take our minerals/water/women/whatever is so laughable."

Yes, it is laughable... wouldn't they rather go to Ceres, or some other body with a low gravity well where it is easy to extract and you don't have to deal with potential biohazards?

Imagine if Aliens came and just said "We claim everything in this system outside Earth's orbit" maybe they'd follow with an offer of technology to earth in exchange for Earth making some stuff for them to help kick start their colonization of our system (assuming a single colony ship arrives, and that the startup phase is a colony ships' hardest part)

"In that case, there could be a missile heading our way right now to end our threat to interstellar civilization. A preemptive strike to ensure we never have a chance to become a threat."

Also something reasonable at first, there's been some sci fi written on that premise, both where Earth does the killing, or gets killed.

But again.... as soon as you expand beyond your home world, such a threat no longer makes sense. If 1-planet species A sends a KEW to wipe out the home planet of multi-system species B.... then Species A has ensured its own destruction.

Before you send a KEW, you better be damn sure that they won't be able to strike back.

If they have self sustaining industry on various moons and asteroids - then all you accomplish is stirring a hornet's nest.

So a multi-star system species, or even a species that is confined to its home star but has self sustaining off-world colonies, are not so vulnerable, and thus likely wouldn't feel so threatened as to resort to genocide. They could in that case beam a simple warning: *insert stuff to allow them to decipher the language of the message* "Warning, we exist acorss multiple star systems, with colonies on multiple planets, and industrial capabilities on smaller cellestial bodies, we cannot be wiped out in a first strike, but you can. Do not attempt to leave your home system, or the planets in your home system will be destroyed by reletavistic KEWs"

That threat of anihilation by KEWs, is precisely a reason to begin sending fusion/Ramjet/antimatter powered vessels to other stars (not to mention, those vessels can also function as KEWs themselves, and form part of your retaliatory capabilities).

Expansion ensures the survival of the species.

Survival of the fittest will surely operate galaxy wide (not that survival of the fittest = always war, there are many symbiotic relationships where each entity increases its fitness through cooperation).

Species that expand will persist and become more prevalent, species that don't will disappear.

I don't see fusion power as an insurmountable hurdle, and across the millennia, Epochs and Eons, of the last billions of years such a mentality surely would have won out eventually, long enough for a massive diaspora to start....

So.... we're back to the Fermi Paradox..... where.... are.... they????

Variants of the Rare Earth hypothesis + evolution being unlikely to lead to technological civilizations like ourselves, seem to be the only answers that make sense to me, and aren't incredibly pessimistic about our own future (technological civilizations destroy their ecosystem/themselves through industry and war, before leaving their home planet)

Ultimately, every clade on Earth is doomed if we don't get off this rock. If we do, we'll surely take many of them with us.

We are simultaneously the greatest threat to the survival of other species on Earth, and their only chance of long term survival (well, the extremophile archea and bacteria probably have ~4 billion years left... but the multicellular life may only have 1 billion)

[SuperWeegee4000]

10's of Billions

My inner grammar Nazi is displeased.

[WestAir]

My inner grammar Nazi is displeased.

Not really relevant to the discussion though.