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Estimating The Number Of Alien Worlds / Species (Drake Equation, Etc.)

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Anonymous

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Looks like the scientific opinion of intelligent life outside Earth has grown somewhat.

Linkee at BBC Science pages



Number of alien worlds quantified

Intelligent civilisations are out there and there could be thousands of them, according to an Edinburgh scientist.

The discovery of more than 330 planets outside our solar system in recent years has helped refine the number of life forms that are likely to exist.

The current research estimates that there are at least 361 intelligent civilisations in our Galaxy and possibly as many as 38,000.

The work is reported in the International Journal of Astrobiology.

Even with the higher of the two estimates, however, it is not very likely that contact could be established with alien worlds.

While researchers often come up with overall estimates of the likelihood of intelligent life in the universe, it is a process fraught with guesswork; recent guesses put the number anywhere between a million and less than one.

"It's a process of quantifying our ignorance," said Duncan Forgan, the University of Edinburgh researcher who carried out the work.

In his new approach, Mr Forgan simulated a galaxy much like our own, allowing it to develop solar systems based on what is now known from the existence of so-called exoplanets in our galactic neighbourhood.

These simulated alien worlds were then subjected to a number of different scenarios.

The first assumed that it is difficult for life to be formed but easy for it to evolve, and suggested there were 361 intelligent civilisations in the galaxy.

A second scenario assumed life was easily formed but struggled to develop intelligence. Under these conditions, 31,513 other forms of life were estimated to exist.

The final scenario examined the possibility that life could be passed from one planet to another during asteroid collisions - a popular theory for how life arose here on Earth.

That approach gave a result of some 37,964 intelligent civilisations in existence.

Form and function

While far-flung planets may reduce uncertainty in how many Earth-like planets there are, some variables in the estimate will remain guesses.

For example, the time from a planet's formation to the first sparks of life, or from there to the first intelligent civilisations, are large variables in the overall estimate.

For those, Mr Forgan says, we will have to continue to assume Earth is an average case.

"It is important to realise that the picture we've built up is still incomplete," said Mr Forgan.

"Even if alien life forms do exist, we may not necessarily be able to make contact with them, and we have no idea what form they would take.

"Life on other planets may be as varied as life on Earth and we cannot predict what intelligent life on other planets would look like or how they might behave."
Click to expand...
 
It remains almost pure speculation, until they discover more than the one inhabited World that they already know about, though.
 
There is a well known equation for estimating the probability of intelligent life in the Universe. If you take it at face value then we are most definitely "not alone". Until we get incontrovertible evidence it all remains as speculation though doesn't it? I think that the recent discoveries of extra-solar planets are fascinating and represent our best means of identifying planets which have or could have life on them.
 
Other that having an idea of how many planets will be out there, I´m not sure it really expands much on Drake´s equation.

Is there any particular reason they didn´t run a scenario where life has difficulty to arise AND evolve?
 
Astronomers: Maybe We’re Alone in the Universe After All
Ryan Whitwam on June 27, 2018 at 7:30 am
  • 65 Comments


    Ever since humans began observing the wider universe, we’ve been struck by how empty space can be. With all the uncountable stars out there, it seems like there should be someone looking back at us. Still, we haven’t found anyone yet—this is known as the Fermi Paradox. The Drake Equation has been used to estimate how many intelligent civilizations exist among the stars, but a new study mutates the equation in an unexpected manner. The authors conclude we’re probably alone. Although, their arguments are a bit suspect.

    Frank Drake proposed the Drake Equation (see below) in 1961 at the first meeting of the search for extraterrestrial intelligence (SETI). It wasn’t intended as a tool to actually calculate the number of alien civilizations but to help us understand what we still don’t know. The Drake Equation takes into account things like the rate of star formation in our galaxy, the fraction of stars with planets, the fraction of stars that support life, and so on. At the end, you get the number of detectable alien civilizations in the Milky Way.

    Even with advances in astronomy, we don’t actually know many of the values for the Drake Equation. We can, however, make better guesses at things like the number of stars and planets in the galaxy. The new study from Oxford University researchers incorporates probabilistic distributions and genome models into the calculation to suggest that we may be completely alone in the universe.

    More at https://www.extremetech.com/extreme/272357-researchers-maybe-were-alone-in-the-universe-after-all
 
A fantastic concept.
 
A million Earths, each with many billions of inhabitants, each connected to whatever future-Internet they have... just imagine the nightmare of trying to find a non-taken online username.
 
It appears to be the case that we are getting closer to filling in some of the numbers in the Drake Equation.

Alien life ‘could be widespread’ across the universe

"The Milky Way has around 400 billion stars – and each has at least one planet. Millions are in the ‘Goldilocks zone’ where water will be liquid."
"Many ‘exoplanets’ – worlds beyond the Solar System – could soon be within the grasp of our technology.
More than 4,000 have been discovered so far – and NASA satellite Tess will is expected to multiply the number dramatically in the next decade.
There are an estimated billion trillion stars in the universe."

https://metro.co.uk/2021/09/20/alien-life-could-be-widespread-across-the-universe-15285292/
 

Why alien hunters have spent 60 years finding new solutions for the Drake Equation​


“Dad, did you ever imagine that your formula would become so famous?” I ask the kind-eyed, 91-year-old person next to me on the patio.

My dad, Frank Drake, is quiet for a moment. Perhaps he’s thinking back to the November day 60 years ago when he unceremoniously drafted a formula that went on to shape humankind’s hunt for extraterrestrial civilizations.

5b32a75a1ae66237008b4999


“No,” Dad says after the pause. “I never imagined that it would become of such widespread interest. I also expected that there might be alterations made to it, and that has not happened.”

Now known as the Drake Equation, Dad’s formula provides a framework for scientists looking for intelligent life beyond Earth. By considering a series of variables, the equation allows scientists to estimate the number of detectable alien civilizations that might be scattered across the Milky Way.

The formula has since become one of the most recognizable equations in science.


5b3a6c014447272a008b46a1


Dad has often said that the last variable in the Drake Equation, L, is the most vexing. L is the average length of time that civilizations are detectable—a definition that’s often conflated with survival or extinction, but which isn’t necessarily linked to either.


“It’s unfortunate that people refer to the longevity term as the longevity of a technological civilization. That’s not what it is. It’s the longevity of the emission mechanism,” Tarter says. “We could in fact build something, some sort of technosignature, that has a longevity well beyond that of our civilization.”

Because L is an average, even one incredibly long-lived alien transmission could dramatically change its value—for example, if a civilization found a way to beam its presence into the galaxy for billions of years, perhaps for no other purpose than to help others in the search for cosmic companions.

“Since everything in the equation has equal weight, I knew the answer was going to be only as good as the thing we knew the least about,” Dad once told me. “L is definitely the thing we know the least about.”

Unlike the other variables, the value of L also depends on the detection capabilities of the civilization doing the searching.

Advanced human civilization may be just a blip in the age of the universe, but Dad thinks it’s only a matter of time and sufficient will before we find evidence that the galaxy is populated with more brainy beings, in whatever form they might take.

“[The Drake Equation’s] durability, longevity, persistence, the reason it sticks around, the reason we keep using it, the reason it keeps popping up is because it’s such a great guide to the whole problem of life in the universe,”

Jason Wright, Pennsylvania State University.

https://www.nationalgeographic.com/...-finding-new-solutions-for-the-drake-equation

maximus otter
 
I recall some years ago reading an article that said depending on what numbers(variables) one plugs into the equation you can get as few as 1 sentient species or as many as 10,000. I suppose even more generous variables would give an even larger number.
 
So far about 4,000 exoplanets have been found, and no one is waving back at us.

We are the “ Garden of Eden “ of the universe and Drake is wrong.

I don think there is anyone else out there.

Now if you talk about different dimensions, that is another story.
 
We know of at least 1 planet that has life.
 
The main problem with the Drake equation is that it's configured to estimate the occurrence of beings just like us who've evolved and developed in the direction of augmenting our basic biological capabilities using technological artifice.

It was intended to serve as a sort of instrument (e.g., a magnifying glass) to aid us in focusing on possible others. In some ways, it's really more of a mirror that only reflects what we think we know about ourselves.

There's no particular reason to believe we're a paradigmatic example of 'civilization'. Neither is there any reasonable basis for assuming the technological capabilities we've developed to date are ones that any - much less many - similar species would necessarily exploit.

In the cosmic scheme of things we may well represent an aberration, and a dangerous / self-destructive one at that.
 
maximus otter said:

Why alien hunters have spent 60 years finding new solutions for the Drake Equation​


“Dad, did you ever imagine that your formula would become so famous?” I ask the kind-eyed, 91-year-old person next to me on the patio.

My dad, Frank Drake, is quiet for a moment. Perhaps he’s thinking back to the November day 60 years ago when he unceremoniously drafted a formula that went on to shape humankind’s hunt for extraterrestrial civilizations.

5b32a75a1ae66237008b4999


“No,” Dad says after the pause. “I never imagined that it would become of such widespread interest. I also expected that there might be alterations made to it, and that has not happened.”

Now known as the Drake Equation, Dad’s formula provides a framework for scientists looking for intelligent life beyond Earth. By considering a series of variables, the equation allows scientists to estimate the number of detectable alien civilizations that might be scattered across the Milky Way.

The formula has since become one of the most recognizable equations in science.


5b3a6c014447272a008b46a1


Dad has often said that the last variable in the Drake Equation, L, is the most vexing. L is the average length of time that civilizations are detectable—a definition that’s often conflated with survival or extinction, but which isn’t necessarily linked to either.


“It’s unfortunate that people refer to the longevity term as the longevity of a technological civilization. That’s not what it is. It’s the longevity of the emission mechanism,” Tarter says. “We could in fact build something, some sort of technosignature, that has a longevity well beyond that of our civilization.”

Because L is an average, even one incredibly long-lived alien transmission could dramatically change its value—for example, if a civilization found a way to beam its presence into the galaxy for billions of years, perhaps for no other purpose than to help others in the search for cosmic companions.

“Since everything in the equation has equal weight, I knew the answer was going to be only as good as the thing we knew the least about,” Dad once told me. “L is definitely the thing we know the least about.”

Unlike the other variables, the value of L also depends on the detection capabilities of the civilization doing the searching.

Advanced human civilization may be just a blip in the age of the universe, but Dad thinks it’s only a matter of time and sufficient will before we find evidence that the galaxy is populated with more brainy beings, in whatever form they might take.

“[The Drake Equation’s] durability, longevity, persistence, the reason it sticks around, the reason we keep using it, the reason it keeps popping up is because it’s such a great guide to the whole problem of life in the universe,”

Jason Wright, Pennsylvania State University.

https://www.nationalgeographic.com/...-finding-new-solutions-for-the-drake-equation

maximus otter
Click to expand...

Nice post to help us visualise the complexity of the Drake equation.
His comment that L - the length of time that a civilisation is detectable is the most vexing, got me thinking about the Pioneer and Voyager probes. These will eventually leave our solar system for good (in another 20,000 years or so) and drift off into interstellar space. They are not aimed at any particular object and so are unlikely to go into orbit around anything or be sucked into a black hole. Apart from erosion by interstellar particles over an insanely long timescale, they could drift for billions of years and could, conceivably, still be drifting after our sun expands into a Red Giant. The probes carry drawings of humans, a route map of where to find us, mathematical constants and even recordings of terrestrial languages and other sounds. So, they could just possibly satisfy Drake's criteria for L long after humankind has either become extinct or moved to another home system.
 
The Drake equation just gained a new bit of data.

NASA's TESS discovers planetary system's second Earth-size world.
Using data from NASA's Transiting Exoplanet Survey Satellite, scientists have identified an Earth-size world, called TOI 700 e, orbiting within the habitable zone of its star—the range of distances where liquid water could occur on a planet's surface. The world is 95% Earth's size and likely rocky.
"This is one of only a few systems with multiple, small, habitable-zone planets that we know of," said Emily Gilbert, a postdoctoral fellow at NASA's Jet Propulsion Laboratory in Southern California who led the work.

https://phys.org/news/2023-01-nasa-tess-planetary-earth-size-world.html
 
TOI 700 e and TOI 700 d are two Earth-sized planets in this system, and both planets are within the habitable zone. All good, you might think. But these planets probably receive a lot of ultraviolet from the star, assuming it is as active as a typical red dwarf star; and both planets are probably tidally locked, so they would have one hemisphere permanently facing the local sun. This means that these planets would be very different to Earth in details. There could be concentric rings of climate around the starward hemisphere, getting hotter towards the centre.
 
It does point out in the article that the planets are indeed tidally locked, but also that only one is in the most advantageous part of the 'habitable zone' with the other two (of 3 in the H.Z.) being in less favourable parts.
 
There is a small chance that being tidally-locked could help to create a limited habitable region on an otherwise uninhabitable planet.

Here's a tidally locked world with a huge desert in the zone directly under the star, but it has a narrow habitable zone along the terminator where sunlight is less direct. (Image by me).
twilight1248476134.jpg
 
Trevp666 said:
How would the weather systems function on such a planet?
Click to expand...
I just found a nice article on eos.org:

Tidally locked and loaded with questions

Tidally locked planets always present the same face to their host stars. What does this mean for their potential to support life?

In the past 20 years, astronomical observations have revealed thousands of planets outside our solar system. Some of these exoplanets are, at least by our standards on Earth, bizarre: Astronomers have found diamond planets; worlds whose surfaces are pelted by sapphires, rubies, and glass; and planets hotter than some stars. Outer space also harbors planets that are relatively similar to Earth, and excitement rises whenever a new “Earth-like” planet is discovered. Could there be life there? we wonder.
 
Trevp666 said:
How would the weather systems function on such a planet?
Click to expand...
It's complicated.
If the planet orbits a very small red dwarf it will have a very short year, which could be as short as a single Earth day (or less). So the planet would revolve once per year. If the year is only 24 hours long, the atmosphere on such a planet would circulate something like the atmosphere on Earth, which would allow considerable mixing from the cold side to the warm side.

If the planet orbits a slightly larger star, the year would be longer, the rotation would be slower, and the circulation would be less dramatic. On a planet that revolves slowly, the main driver of circulation would be the hot, high-pressure area directly under the sub-stellar point. This could cause dramatic, permanent or semi-permanent storms or hurricanes in the hot zone that remain in place persistently. On a slowly rotating world the dark side would be covered in ice.
 
More detailed assessments of TOI-700 d and TOI-700 e can be found here by Andrew LePage.
https://www.drewexmachina.com/2020/...ck-toi-700d-discovered-by-nasas-tess-mission/
https://www.drewexmachina.com/2023/...ck-toi-700e-discovered-by-nasas-tess-mission/

Both planets are likely to be tidally-locked, TOI-700 d is a bit larger than Earth and TOI-700 e is probably a bit too hot, so they aren't very Earthlike. But both are quite good candidates for life that is not quite like that found on our planet. The quest for a truly Earth-like planet goes on.
 
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