The Fermi Paradox - Rare Earth Hypothesis Part 1

www.theguardian.com...

"Astronomers have added 219 candidates to the growing list of planets beyond our solar system, 10 of which may be about the same size and temperature as Earth, boosting their chances of hosting life.

Scientists found the candidates in a final batch of Nasa’s Kepler Space Telescope observations of 200,000 sample stars in the constellation Cygnus.

They include 10 newly discovered rocky worlds that are the right distance from their parent stars for water, if it exists there, to pool on the surface. Scientists believe liquid water is a key ingredient for life.

An important question for us is, ‘Are we alone?’” Kepler program scientist Mario Perez said in a conference call with reporters. “Maybe Kepler today is telling us indirectly ... that we are not alone.”

Aaaand another interesting link:

www.nature.com...

"Our observations reveal that at least seven planets with sizes and masses similar to those of Earth revolve around TRAPPIST-1. The six inner planets form a near-resonant chain, such that their orbital periods (1.51, 2.42, 4.04, 6.06, 9.1 and 12.35 days) are near-ratios of small integers. This architecture suggests that the planets formed farther from the star and migrated inwards4, 5. Moreover, the seven planets have equilibrium temperatures low enough to make possible the presence of liquid water on their surfaces"

Yes, they are rare but we wont give up. Soon the james webb telescope will start and (letz hope it wont share hubbles troubles) let us measure the atmosphere of these earth like planets. If we measure methan we can call it a mini jackpot

a reply to: eriktheawful

There is another factor in the Rare Earth hypothesis - the protection afforded by the gas giants, sweeping up potentially deadly asteroids which lowers the chance of impact with the earth.

A planet without this sort of protection, even if ideal in every other way, may receive too many extinction level impacts to develop intelligent life.

Y bashing each other? We are all searching for answers..

There is also criticism about the rare earth hypothesis..

en.m.wikipedia.org...

Exoplanets around main sequence stars are being discovered in large numbers

An increasing number of extrasolar planet discoveries are being made with 3,621 planets in 2,712 planetary systems known as of 1 July 2017. Rare Earth proponents argue life cannot arise outside Sun-like systems. However, some exobiologists have suggested that stars outside this range may give rise to life under the right circumstances; this possibility is a central point of contention to the theory because these late-K and M category stars make up about 82% of all hydrogen-burning stars.

Current technology limits the testing of important Rare Earth Criteria: surface water, tectonic plates, a large moon and biosignatures are currently undetectable. Though planets the size of Earth are difficult to detect and classify, scientists now think that rocky planets are common around Sun-like stars. The Earth Similarity Index (ESI) of mass, radius and temperature provides a means of measurement, but falls short of the full Rare Earth criteria.

Rocky planets orbiting within habitable zones may not be rare
Some argue that Rare Earth's estimates of rocky planets in habitable zones are too restrictive. James Kasting cites the Titius-Bode law to contend that it is a misnomer to describe habitable zones as narrow when there is a 50% chance of at least one planet orbiting within one. In 2013 a study that was published in the journal Proceedings of the National Academy of Sciences calculated that about "one in five" of all sun-like stars are expected to have earthlike planets "within the habitable zones of their stars"; 8.8 billion of them therefore exist in the Milky Way galaxy alone. On 4 November 2013, astronomers reported, based on Kepler space mission data, that there could be as many as 40 billion Earth-sized planets orbiting in the habitable zones of sun-like stars and red dwarf stars within the Milky Way Galaxy. 11 billion of these estimated planets may be orbiting sun-like stars.

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a reply to: Vratyas

I think the main thing with oxygen isn't so much for life to get started. Indeed, we know that life started here in Earth with hardly any free oxygen in the atmosphere.

However, what we do know is after the great oxygenation of the Earth, life here virtually exploded with diversity and in complexity.

Not surprising given the energy that oxygen gives many life forms. Prior to that event, life was rather simple and microbial for billions of years. The GOE didn't happen over night, it took several hundred millions of years, but once there was enough oxygen in the atmosphere, life really began to take off (around 500 million years ago).

So is it absolutely needed for life? No, we know it isn't. However, it did speed up what evolved here.

How is that important?

Time and the life span of the sun.

In about another 500 million to 1 billion years from now, our sun will have increased it's heat output to where the Earth will be too hot for life. If the GOE had not happened, it looks like life here would have stayed simple, due to the lack of high energy processes that help evolution.....until the sun gets too hot for even it to survive.

Does it have to be oxygen? Well, for here on Earth with the life we have, we know it worked great.

I guess the question would be: what other gases would work? How easily do they combine with other things? How energetic is it?

a reply to: eriktheawful

Hot candidate is titan.. need to sleep now

Again, I stand by Time as being the greatest variable.

No doubt you have planets that would be an absolute match for earth and life, But when did they meet this point.
Was it 1Billion years ago, 10 Billion Years ago, 1 Million from now?

There are things that are Rare, yet still abundant. Diamonds are "rare" yet everyone has some kind of diamond jewelry.

One could spend their whole life wandering in a desert looking for a diamond and not find one though even if they check every grain of sand, But If you knew where to look and when, you could walk along a plowed muddy field after a rain and find a diamond in a short period of time.

It seems that if we acknowledge that rarity in such a massive quantity equates to higher opportunity and focus on looking in the right places at the right time, we indeed would find life and evolved life as well.

We are learning where to look and what to look for. But the greatest problem will still be time.

Where can two cvilizations meet on the huge timeline. Did a meteor strike set one civilization back 100,000 years? Did Ice ages last too long on Earth? Will war prevent advances?

In the past, astronomers have found that the cosmos is hierarchically assembled, with galaxies being arranged in clusters, superclusters, sheets, walls and filaments. These are separated by immense cosmic voids, which together create the vast “Cosmic Web” structure of the Universe.

Futurism, July 21, 2017 - This Is One of the Largest Structures We Know of in the Universe.

- and -

The cosmic void that contains the Milky Way's is dubbed the Keenan, Barger and Cowie (KBC) void, after the three astronomers who identified it in the 2013 study. It is the largest cosmic void ever observed — about seven times larger than the average void, with a radius of about 1 billion light-years, according to the study.

Space.com, June 14, 2017 - We Live in a Cosmic Void, Another Study Confirms.

The Milky Way is part of the larger local cluster which is part of the Virgo Supercluster. But our little galaxy itself resides in a cosmic void.

These are massive distances to think about. Maybe the rare earth is not so much that Earth is rare but that we live a small town in the middle of the desert.

Just wanted to point out how vast space is and why our galaxy and Earth seems to be alone.

IMHO, we are not alone. But we need to get out of our bubble which may be harder than when you live in the center of a megalopolis!

As long as we cant control spacetime we are forced to look into the past :-/

a reply to: eriktheawful

I guess we here on Earth "won the lottery" of advanced life in HOW many different ways? To the point our planet is the right SIZE for chemical rocket fuel to achieve escape velocity? And it has all the ingredients and elements neeeded to create it.

I guess it was a coincidence.... a coincidence to the 12th power. An exponential increase in coincidences on Sol3.

Top notch thread, Erik. Real top shelf quality here. I detect a true passion for learning and spreading what has been learned to other eager minds. Or i could just say teaching. Learning and teaching. There's a,lot more than just teaching going on here though.


How bout winning those 5,000 or so lotteries right in a row? I'm thinking I might celebrate just a little. I'm intelligent... What? Yes, I am! By the scientific definition, I am an example of "intelligent life". So there... I'm intelligent, advanced, tool using, all thanks to my planet and star, the Dream Team. It takes teamwork to make the dream work.

If we lost just one of those lotteries, we could be stuck in 1800s tech, or worse, or life never went beyond aemeobas (i knew it needed a few extra vowels in there somewhere, but, this doesn't look right either. Spell check didn't even TRY to help me... Wth? I'm fed up with this planet/star collabo, it's let me down one too many times!) or no life at all...

Just a charred, dying cinder, lonely and unwanted...just floating around on auto pilot, no real direction or goals... facing uncertainty around every turn, never knowing if this next time around might be his last.... Hey, kinda like me.... Just kidding XD Hahaha that was a gooood joke hahaha yes, that's what it was! Haha...ha...ha...


:^)

In my opinion there is another factor bounded to size and composition of Earth like planet: Plate tectonics.

Live in relatively stable environments tends to create stable ecosystems. Stable ecosystems means lower rate of evolutionary changes. Too fast and vast changes of environment are on other hand also bad. Other factor is depletion of nutrients from environment by biological and sedimentary processes.

Steady pace of environmental changes is on Earth guaranteed by plate tectonics and subsequent volcanizm. Not only is surface environment replenished with material from Earth's mantle but new sedimentary material is constantly forged on tectonic boundaries, spitted out by volcanoes or slowly squeezed out to surface hundreds of millions of years later. This (with life itself) creates vast diversity of constantly changing ecosystems. It is constant pressure needed for evolution to really kick in.

Plate tectonics is probably detrimental for rise of technological civilization: accessible deposits of almost all raw materials are created by this process.

originally posted by: Vratyas
www.theguardian.com...

"Astronomers have added 219 candidates to the growing list of planets beyond our solar system, 10 of which may be about the same size and temperature as Earth, boosting their chances of hosting life.

Scientists found the candidates in a final batch of Nasa’s Kepler Space Telescope observations of 200,000 sample stars in the constellation Cygnus.

They include 10 newly discovered rocky worlds that are the right distance from their parent stars for water, if it exists there, to pool on the surface. Scientists believe liquid water is a key ingredient for life.

An important question for us is, ‘Are we alone?’” Kepler program scientist Mario Perez said in a conference call with reporters. “Maybe Kepler today is telling us indirectly ... that we are not alone.”

If you look in Wiki, they determined based on how many stars the telescope had examined vs. how many planets it found, that the number of planets througout the milky way that meet the criteria is likely more than 10 billion. (Possibly as many as 40 billion)

As of January 2015, Kepler and its follow-up observations had found 1,013 confirmed exoplanets in about 440 star systems, along with a further 3,199 unconfirmed planet candidates.[B][26][27] Four planets have been confirmed through Kepler's K2 mission.[28] In November 2013, astronomers estimated, based on Kepler space mission data, that there could be as many as 40 billion rocky, Earth-size exoplanets orbiting in the habitable zones of Sun-like stars and red dwarfs within the Milky Way.[29][30][31] It is estimated that 11 billion of these planets may be orbiting Sun-like stars.[32] The nearest such planet may be 3.7 parsecs (12 ly) away, according to the scientists.[29][30]

But

originally posted by: EasyPleaseMe
a reply to: eriktheawful

There is another factor in the Rare Earth hypothesis - the protection afforded by the gas giants, sweeping up potentially deadly asteroids which lowers the chance of impact with the earth.

A planet without this sort of protection, even if ideal in every other way, may receive too many extinction level impacts to develop intelligent life.

There are other factors to consider also.

1)- Earth's magnetic field.

This prevents the atmosphere being blown away by the solar wind. It's theorized that Mars once had a pretty good atmosphere, but due to it lacking a strong magnetic field, most of it got blown away into space.


2) - Earth's very large moon.

Most of the other planets in the solar system have proportionally smaller moons than Earth does. Because of this, their axis of rotation changes over time.

If that happened on Earth, there would be serious climate issues. Part of the equator might end up as a pole.

This happens to a smaller degree already, due to plate tectonics causing continents to move around. But the effect is very gradual and the ecosystem has a long time to adjust to it.

The Moon also helps to divert asteroids.

originally posted by: JanAmosComenius
In my opinion there is another factor bounded to size and composition of Earth like planet: Plate tectonics.

Live in relatively stable environments tends to create stable ecosystems. Stable ecosystems means lower rate of evolutionary changes. Too fast and vast changes of environment are on other hand also bad. Other factor is depletion of nutrients from environment by biological and sedimentary processes.

Steady pace of environmental changes is on Earth guaranteed by plate tectonics and subsequent volcanizm. Not only is surface environment replenished with material from Earth's mantle but new sedimentary material is constantly forged on tectonic boundaries, spitted out by volcanoes or slowly squeezed out to surface hundreds of millions of years later. This (with life itself) creates vast diversity of constantly changing ecosystems. It is constant pressure needed for evolution to really kick in.

Plate tectonics is probably detrimental for rise of technological civilization: accessible deposits of almost all raw materials are created by this process.

Seems we have just enough change, but not too much.

Perhaps it could be said there is a "goldilocks zone" for change, just like there is for sunlight.

Wanted to point out a couple of things:

1) I'm going to be finally posting part 2 of this thread in a day or 2, which will be the Rare Earth Hypothesis - Intelligent Life.

2) We tend to think of our planet and sun as being "perfect" and why life arose here, and later having intelligent species. Truth is, no, neither the Earth nor our sun is perfect for this, here's why:

- Being a G type star, our sun has a life span of about 10 billion years, of which it only has 6 billion before it gets too hot for life to survive on worlds within it's green zone. K type stars (they look orange) can have life spans of up to 50 billion years, and be a bit more stable, meaning life has much longer to start and grow.

- A Earth like planet that is slightly larger than our world would be better. It would more than likely have a stronger magnetic field around it, helping protect against solar and cosmic radiation, and a slightly thicker atmosphere, helping deflect or burn up more meteors which might get through to either detonate just above the ground or impact.

Those 2 things do not make that system "perfect" either. But it does make things better.

Okay, hope to see you all in the part 2 thread.