Researchers conclude the universe contains fewer Earth-like planets than previously thought

February 24, 2016 by Bob Yirka report
This is the "South Pillar" region of the star-forming region called the Carina Nebula. Like cracking open a watermelon and finding its seeds, the infrared telescope "busted open" this murky cloud to reveal star embryos tucked inside finger-like pillars of thick dust. Credit: NASA

(Phys.org)—A small team of researchers, three with Swedish Institutions and one from the U.S. has created a computer model of the known universe and in using it to estimate the number of likely other exoplanets able to hold life, has found that there might be fewer Earth-like planets than has been thought. In their paper they have uploaded to the preprint server, arXiv (soon to be published in The Astrophysical Journal), the team describes how they went about creating their model and what it showed.

The team took a in creating their model, first inputting data that described as much as is known about the early universe—then next adding data about known exoplanets and also information describing the laws of physics and the way they would work on the elements that made up the universe, and how they would grow or change over approximately 13.8 billion years. They then took a virtual census and found the model had "created" approximately 700 million trillion exoplanets—but, to the surprise of the researchers, the vast majority of them were far older than planet Earth.

If correct, the models suggest that Earth is much more unique than other models have been showing in the past few years. This is because it is assumed that if life began on other planets far earlier than on Earth, because it would be much older, it should have matured beyond what we have here on Earth to the point that it would be not only noticeable to us, but likely dominant. But because we have not seen any sign of other life, it appears likely that none is there, or is close enough to spot, which suggests that Earth actually is much more unique than other recent models have been suggesting. The model also suggested that most exoplanets likely exist in galaxies that are a lot bigger than the Milky Way, and orbit stars that are quite different from our sun. To date, space scientists have identified approximately 2,000 exoplanets, clearly a very small proportion of the total amount if the new model is to be viewed as accurate.

The researchers acknowledge that their model is based on data that is still only partly understood, and that much of what we have observed to date is still somewhat hazy, thus, it is not clear just how accurate their really is.

Explore further: Earth-like planets have Earth-like interiors

More information: Terrestrial planets across space and time, arXiv:1602.00690 [astro-ph.GA] arxiv.org/abs/1602.00690v1

Abstract
The study of cosmology, galaxy formation and exoplanetary systems has now advanced to a stage where a cosmic inventory of terrestrial planets may be attempted. By coupling semi-analytic models of galaxy formation to a recipe that relates the occurrence of planets to the mass and metallicity of their host stars, we trace the population of terrestrial planets around both solar-mass (FGK type) and lower-mass (M dwarf) stars throughout all of cosmic history. We find that the mean age of terrestrial planets in the local Universe is 8±1 Gyr and that the typical planet of this type is located in a spheroid-dominated galaxy with total stellar mass about twice that of the Milky Way. We estimate that hot Jupiters have depleted the population of terrestrial planets around FGK stars at redshift z=0 by no more than ≈10%, and predict that ≈1/3 of the terrestrial planets in the local Universe are orbiting stars in a metallicity range for which such planets have yet to be been detected. When looking at the inventory of planets throughout the whole observable Universe (i.e. in all galaxies on our past light cone) we argue for a total of ≈2×1019 and ≈7×1020 terrestrial planets around FGK and M stars, respectively. Due to the hierarchical formation of galaxies and lookback-time effects, the average terrestrial planet on our past light cone has an age of just 1.7±0.2 Gyr and is sitting in a galaxy with a stellar mass a factor of ≈2 lower than that of the Milky Way. These results are discussed in the context of cosmic habitability, the Copernican principle and the prospects of searches for extraterrestrial intelligence at cosmological distances.

via ScientificAmerican

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orti
2.1 / 5 (11) Feb 24, 2016
"The researchers acknowledge that their model is based on data that is still only partly understood, and that much of what we have observed to date is still somewhat hazy, thus, it is not clear just how accurate their model really is."
Such uncertainties don't bother Carl Sagan, NASA, various other atheists, and the SETI people from proclaiming "billions and billions".
Bigbangcon
1.9 / 5 (13) Feb 24, 2016
"The team took a logical approach in creating their model, first inputting data that described as much as is known about the early universe -"

This is no logical approach at all and there is absolutely no reason (logic) why there should be a beginning and an early universe. It is an arbitrary and a pure assumption based on prejudice! So all the computer modelling based on this faulty assumption means nothing at all. The physicists' modelling of the universe with Lego (or is it LIGO) is mere child's play.

There is no reason why the universe should not be infinite in space, eternal in time and ever-changing!: http://www.amazon...0414445.
katesisco
1.4 / 5 (9) Feb 24, 2016
The theory of our Moon being created by an impactor is based largely on the claim most solar bodies have twins in orbit. Which would disturb the orbiting planets which would create possible impacts. Not so. Our Moon is the creation of Mother Earth. Which then makes the search for a new theory necessary and the recognition that our large lush life is indeed unique.
gkam
3.3 / 5 (7) Feb 24, 2016
Perhaps it is time we started taking care of the only Earth we have.
OdinsAcolyte
1.9 / 5 (9) Feb 24, 2016
We are unique and. like it or not, divine.
It is a shame our divinity is not directed toward good stewardship of our world and the life upon it.

We are wind on the grass and we too shall soon pass.
bschott
1 / 5 (4) Feb 24, 2016
We are unique and. like it or not, divine.


Not all of us.

It is a shame our divinity is not directed toward good stewardship of our world and the life upon it.


The "divine" are not in control right now.....

We are wind on the grass and we too shall soon pass.


Again, not all of us.
sstritt
3 / 5 (5) Feb 24, 2016
Worst title ever. Why are today's science writers so deficient in language skills?
Zzzzzzzz
3.5 / 5 (13) Feb 24, 2016
Quite the list! Three new ignore button candidates.... this kind of thing sure is a magnet for delusionals desperately and vigorously defending their delusions.....
bschott
2.4 / 5 (7) Feb 24, 2016
this kind of thing sure is a magnet for delusionals desperately and vigorously defending their delusions.....


Mainstream theoretical physics....what can ya say?
antigoracle
2.7 / 5 (7) Feb 24, 2016
We are unique and. like it or not, divine.
It is a shame our divinity is not directed toward good stewardship of our world and the life upon it.

We are wind on the grass and we too shall soon pass.

I did pass some wind on reading this and it was far from divine.
TheGhostofOtto1923
3.7 / 5 (9) Feb 24, 2016
What a coincidence. I was just passing wind as I read your post.
Not all of us
Perhaps he was referring to this divine
https://youtu.be/pFiqO0Qpa_g

-which I am sure is also very rare in the universe.
Shabs42
5 / 5 (5) Feb 24, 2016
I still think there are two great filters on life. One, it took ~3 billion years and multiple mass extinctions to go from life to intelligent life here on Earth. Two, we haven't figured out interstellar travel and there's little evidence we will in the near future. Sure, we could send a couple probes to the nearest star systems and have it there in a couple hundred years, but actually colonizing outside of our own solar system seems beyond our reach for a very long time.
gkam
2.3 / 5 (11) Feb 24, 2016
can we clean up this site, please? No teacher would send his/her kids here with the kind of intelligent discussion such as :

"I did pass some wind on reading this and it was far from divine."
and
"What a coincidence. I was just passing wind as I read your post. "

In other posts the same two scream "liar" (and worse), at others with whom they disagree, especially if they are proven wrong.

This site can be better. We need everyone to police the rude behavior.
julianpenrod
1.8 / 5 (10) Feb 24, 2016
One can ask, among other things, if the model took into account the generation of new systems from material from exploded stars. It is never indicated that the amount of material expelled during supernovas and such is so small an amount, maybe this is admitting that the generating of new systems is at a level much smaller than the first generation of systems, so new planets would be smaller in number.
But, if other claims are accepted, most of the substance in the earliest universe would be in the form only of elements no heavier than lithium, and it's not certain intelligent type life, or life itself, as generally defined, could be based on only three elements. And planets harboring life, likely, will have to be from second generation early stars, and so be no more than 8 billion years old.
julianpenrod
1.8 / 5 (10) Feb 24, 2016
But, if civilizations are so much older, and beings there of mental processes that, compared to ours, are like ours compared to ants, we may be "aware" of them, conventionally speaking, only as ants are "aware" of us. They think of us as blocks that get in the way, then, when we are gone, they forget about us. The aliens may be talking to us and many cannot hear them because they won't accept them, they may be studying us and many cannot even be aware of that. How easy would it be for God haters, who insist there is no evidence of the presence of God, to even consider the possibility of superior aliens if the aliens avoid providing any evidence that the dull witted and superficial couldn't see and interpret? But, then, maybe the aliens, when they reach mental superiority, go on to subjects closer to the nature of God and leave others to find their own way, if they are willing to.
blazmotronic
3 / 5 (4) Feb 24, 2016
The uniqueness of the earth..i suggest you watch
the privileged planet...our home is not random!
junkieturtle
2.6 / 5 (5) Feb 25, 2016
I love the assumption that we should be aware of other alien civilizations...just because it gives the result the researchers were looking for.

Assumptions about alien civilizations are completely baseless and bad science. There is literally no data on alien civilizations, certainly none that allows you to say that we should have heard from them by now and since we haven't it means Earth is rare.

This is science done purely to justify the existence of the researchers jobs.
Psilly_T
2.3 / 5 (3) Feb 25, 2016
@otto LOL LUV it
@julian LUV IT

save the earth or save the consciousness hmmm decisions decisions
KeithMcC
2.3 / 5 (3) Feb 25, 2016
Worst title ever. Why are today's science writers so deficient in language skills?

At least it didn't say "Scientists find ... "
TheGhostofOtto1923
3.7 / 5 (6) Feb 25, 2016
can we clean up this site, please? No teacher would send his/her kids here with the kind of intelligent discussion
No teacher would want their students to think that

Fallout is the principal cause of lung cancer

Swimming pools are commonly used for residential cooling

High energy alpha cannot penetrate the skin

Manure dust (george thinks this is called volatile solids and his phony MS tells him he is right) is the main constituent of the high air of the central valley

There was an H2-initiated criticality in a dirty molten Pu puddle which threw debris 130km although a conventional hydrogen bomb can't throw it more than a few km... but since there was no crater it must've been an airburst

-No, kids would learn far more from chucky cheese than they would from reading george kamburoff poop.

But they COULD learn a lot about mental illness and psychopathy, so maybe it would be worthwhile.
Whydening Gyre
5 / 5 (3) Feb 25, 2016
FTA -
The researchers acknowledge that their model is based on data that is still only partly understood, and that much of what we have observed to date is still somewhat hazy, thus, it is not clear just how accurate their model really is.

This would explain why neither the researchers, nor the institutions were named...l:-)

Vietvet
4.4 / 5 (7) Feb 25, 2016
ScientificAmerican has a better article and it names researchers and institutions

.http://www.scient...ter-all/
Phys1
4.3 / 5 (6) Feb 25, 2016
Such uncertainties don't bother Carl Sagan, NASA, various other atheists,

Various ? More likely all of them.
and the SETI people from proclaiming "billions and billions".

That is a very conservative estimate, indeed.
torbjorn_b_g_larsson
4.3 / 5 (6) Feb 25, 2016
This article, and most the thread, go overboard in discussing a paper they superficially or obviously haven't read. (All of the ridiculous magic peddlers obviously didn't bother, for example.)

The paper discuss making a claim that Earth analogs is rare based on the frequency of elliptic vs spiral galaxies. Can they make such an extraordinary claim based on extraordinary evidence, here > 5 sigma? No, they can not, they find only ~ 75 % of Earth analogs would be in an elliptic. The near universe proportion of elliptic galaxies is ~ 25 %, while as expected some sort of spiral structure is present in ~ 85 %! [ http://arxiv.org/...96v2.pdf ; fig. 4 and 16.]

We expect to see Earth were it is found, in 0.85*0.25 = 21 % of cases Earth would lie in a 'spiral' galaxy, in 0.25*0.75 = 19 % of cases it would lie in an elliptic. The rest of their claims is similarly as expected, the most they can arrive it is a 1 sigma (factor of 2) deviance which isn't significant.
antialias_physorg
5 / 5 (5) Feb 29, 2016
estimate the number of likely other exoplanets able to hold life

...as we know it. That small (but I feel important) rider is always missing.

it should have matured beyond what we have here on Earth to the point that it would be not only noticeable to us

I don't get this. Why? Even our stone-age tech is getting increasingly unobtrusive. It makes sense that tech is optimized to ONLY do what it is supposed to do. Anything that it might be noticed by would be 'stray radiation' (i.e. waste). An adavanced species would have no waste (if for nothing else but aesthetic reasons)

but likely dominant

Again: Why? What's the point of 'becoming dominant' exactly?

There's a lot of extrapolations from Earth behavior that aren't merited in a galaxy/universe setting. On Earth CO-evolved(!) species compete within an environment where they access limited/shared resources. In space none of this holds true.
Captain Stumpy
3 / 5 (4) Feb 29, 2016
In space none of this holds true
@AA_P
i disagree... it actually becomes more important. just because there is a lot of space doesn't mean there is a lot of resources ... or the ability to harvest said resources
which brings me to the "What's the point of 'becoming dominant' " part... it is about control of resources and survival

Now, it may well be anthropocentric to consider that any intelligent life must also be a predatory life... but if you consider the circumstances:
any intelligent life would have to be- curious, in control of their resources and capable of making fire in multiple forms (ruling out ocean dwellers as cosmonauts unless they have "help")
the simple fact of that added into the whole survival instinct of nature screams predatory, IMHO, thus they will, by default, attempt to be dominant enough to control resources required. one of the primary fundamental facts of all living creatures (and a driving force) is the fight to survive
antialias_physorg
4.3 / 5 (6) Feb 29, 2016
just because there is a lot of space doesn't mean there is a lot of resources ... or the ability to harvest said resources

Well the reasoning goes thus:
Advance means efficient (i.e. no waste). Which in turn means:
- a species will reduce its reliance on having to acquire complicated resources elsewhere through (near) perfect reuse of resources. At that point all you really need as a resource is energy.
- longevity (or virtual immortality) will come along at some point. Then the idea of procreation becomes moot. Procreation only makes sense if you are mortal. In an immortality situation you're just creating more competition.
- (species) survival instincts become obsolete once you've spread a tiny bit (or are able to live in space) and are individually immortal. Survival instincts only make sense in a situation where you are threatened.

We're extrapolating from human/animal drives. But these don't really make sense to me beyond a certain level of advancement.
Captain Stumpy
3.4 / 5 (5) Feb 29, 2016
Advance means efficient (i.e. no waste)
@AA_P
i am not sure i agree with this...even on earth advanced doesn't always mean more efficient. maybe overall...
longevity (or virtual immortality) will come along at some point
not sure about this either... i mean, if an advanced civilisation is intent on space travel and exploration while constrained to what we know now... maybe!
but if they found the ability to manufacture stable worm-holes or similar FTL travel early on? you could potentially argue longevity but... i am not so sure as we still haven't actually figured out WHY cellular senescence is so prevalent in life
maybe death is the one thing we just can't get around?

i can understand your argument but... this is where things are difficult because i'm trying to think of life as we don't know it...
http://www.bigear...9p05.htm

i just don't really know.... prediction is HARD, and rarely accurate with so many unknowns

Captain Stumpy
3 / 5 (4) Feb 29, 2016
- (species) survival instincts become obsolete once you've spread a tiny bit (or are able to live in space) and are individually immortal. Survival instincts only make sense in a situation where you are threatened.

We're extrapolating from human/animal drives. But these don't really make sense to me beyond a certain level of advancement.
@AA_P
just a thought but.... this could be the reason we don't see intelligent life out there all over the place?
IF we advance enough to lose the survival instinct
and then we run into a lesser advanced species (but say, still capable of doing damage to us)
then it is far more likely we will be on the short end of the stick there...

if we took a man and put them in the wild without the survival instinct (like putting a city slicker into the deep woods - LOL) and they face off with the wild animals... they might do well for a short time but unless that person develops a fight/flight instinct real quick, they'll be dead
antialias_physorg
4.5 / 5 (6) Feb 29, 2016
i am not sure i agree with this...even on earth advanced doesn't always mean more efficient. maybe overall...

Well, if we look at some examples by which we may be detected:
Radio: In the beginning we were blasting radio omnidirectionally (wasteful). Now we're pinpointing it at satellites and bouncing it back to where we need it. Our radio footprint is decreasing.
Environment: We're shifting towards renewables. The pollution aspects (waste) will decrease. Already rivers in some countries are recovering from the pollution levels of the 1980's and 90's.
Tech generally: The trend is towards miniaturization/using less energy for the same service in all areas.

maybe death is the one thing we just can't get around?

Not biologically. But what is to stop an advanced species from changing substrate to something durable?

In the end there's always this counterargument to 'domination': If you're comfortable in space - why would you ever go back down a gravity well?
Captain Stumpy
3 / 5 (4) Feb 29, 2016
Our radio footprint is decreasing.
@AA_P
is it? I see what you mean but... ??
i am gonna look that one up and see if i can't get some feedback on it... if you can find something on that , please let me know... i would really appreciate it. THANKS
In the end there's always this counterargument to 'domination': If you're comfortable in space - why would you ever go back down a gravity well?
Good point ... but it may well boil back down to resources
you may be able to mine every asteroid in your area, but eventually you will end up (as a species) having to mine the larger stuff, like moons etc... gravity wells...

Plus, if you needed a specific resource that may be plentiful but only in a gravity well...it would be very limiting to exclude them as a source because of the limitations of the physical body
... that is one reason i considered hybridisation and AI as the eventual dominant life form in our existence
Captain Stumpy
3 / 5 (4) Feb 29, 2016
Radio: In the beginning we were blasting radio omnidirectionally (wasteful). Now we're pinpointing it at satellites and bouncing it back to where we need it. Our radio footprint is decreasing
@AA_P
i put the question to the NASA site (and will likely seek out a few other sources)
I searched for radio emissions but found only results from our observations of other planets... nothing for earth at all

the bulk of the search leads to "how radio waves work" or "planetary emissions"... not one of which i saw were Earth and our footprint

If you have better luck, i would appreciate some feedback and links i can read

THANKS in advance - again
antialias_physorg
5 / 5 (2) Mar 01, 2016
is it? I see what you mean but... ??

Well, sort of. Of course we are increasing the number of radio transmissions. But that, too will get saturated. From there on efficiency will decrease the total footprint (currently it's more the individual footprint that is decreasing). It's a bit like cars. Do we blast more exhaust into the atmosphere? Sure, because we have ever more cars. But at the same time the average car gets more efficient - and at some point the amount of vehicles tops out.
Inefficiency is equivalent to waste. And mature tech seems to always move in direction of efficiency over waste eventually.

Good point ... but it may well boil back down to resources

Resources is something you get much more easily from asteroid belts. If you consider that these are basically plantes that failed to form then the amount of resources these contain is enormous - whereas on planets like Earth 99% of resources are bound up in molten slag.
antialias_physorg
5 / 5 (1) Mar 01, 2016
I searched for radio emissions but found only results from our observations of other planets... nothing for earth at all

I take this from articles like these:
https://www.thegu...tronomer

[sic]"The trouble is that we are making ourselves more and more difficult to be heard," said Dr Drake. "We are broadcasting in much more efficient ways today and are making our signals fainter and fainter."

In the past, TV and radio programmes were broadcast from huge ground stations that transmitted signals at thousands of watts. These could be picked up relatively easily across the depths of space, astronomers calculated.

Now, most TV and radio programmes are transmitted from satellites that typically use only 75 watts and have aerials pointing toward Earth, rather than into space.

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