13 light years away: Earth-like planets are right next door

Feb 06, 2013
This artist's conception shows a hypothetical habitable planet with two moons orbiting a red dwarf star. Astronomers have found that 6 percent of all red dwarf stars have an Earth-sized planet in the habitable zone, which is warm enough for liquid water on the planet's surface. Since red dwarf stars are so common, then statistically the closest Earth-like planet should be only 13 light-years away. Credit: David A. Aguilar (CfA)

Using publicly available data from NASA's Kepler space telescope, astronomers at the Harvard-Smithsonian Center for Astrophysics (CfA) have found that six percent of red dwarf stars have habitable, Earth-sized planets. Since red dwarfs are the most common stars in our galaxy, the closest Earth-like planet could be just 13 light-years away.

"We thought we would have to search vast distances to find an Earth-like planet. Now we realize another Earth is probably in our own backyard, waiting to be spotted," said Harvard astronomer and lead author Courtney Dressing (CfA).

Dressing presented her findings today in a press conference at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.

are smaller, cooler, and fainter than our Sun. An average red dwarf is only one-third as large and one-thousandth as bright as the Sun. From Earth, no red dwarf is visible to the .

Despite their dimness, these stars are good places to look for Earth-like planets. Red dwarfs make up three out of every four stars in our galaxy for a total of at least 75 billion. The signal of a is larger since the star itself is smaller, so an Earth-sized world blocks more of the star's disk. And since a planet has to orbit a cool star closer in order to be in the , it's more likely to transit from our point of view.

Dressing culled the Kepler catalog of 158,000 target stars to identify all the red dwarfs. She then reanalyzed those stars to calculate more accurate sizes and temperatures. She found that almost all of those stars were smaller and cooler than previously thought.

When it's young, a red dwarf star frequently erupts with strong ultraviolet flares as shown in this artist's conception. Some have argued that life would be impossible on any planet orbiting in the star's habitable zone as a result. However, the planet's atmosphere could protect the surface, and in fact such stresses could help life to evolve. And when the star ages and settles down, its planet would enjoy billions of years of quiet, steady radiance. Credit: David A. Aguilar (CfA)

Since the size of a transiting planet is determined relative to the star size, based on how much of the star's disk the planet covers, shrinking the star shrinks the planet. And a cooler star will have a tighter habitable zone.

Dressing identified 95 planetary candidates orbiting red dwarf stars. This implied that at least 60 percent of such stars have planets smaller than Neptune. However, most weren't quite the right size or temperature to be considered truly Earth-like. Three planetary candidates were both warm and approximately Earth-sized. Statistically, this means that six percent of all red dwarf stars should have an Earth-like planet.

"We now know the rate of occurrence of habitable planets around the most common stars in our galaxy," said co-author David Charbonneau (CfA). "That rate implies that it will be significantly easier to search for life beyond the solar system than we previously thought."

Our Sun is surrounded by a swarm of red dwarf stars. About 75 percent of the closest stars are red dwarfs. Since 6 percent of those should host habitable planets, the closest Earth-like world is likely to be just 13 light-years away.

Locating nearby, Earth-like worlds may require a dedicated small space telescope, or a large network of ground-based telescopes. Follow-up studies with instruments like the Giant Magellan Telescope and James Webb could tell us whether any warm, transiting have an atmosphere and further probe its chemistry.

Such a world would be different from our own. Orbiting so close to its star, the planet would probably be tidally locked. However, that doesn't prohibit life since a reasonably thick atmosphere or deep ocean could transport heat around the planet. And while young red emit strong flares of ultraviolet light, an atmosphere could protect life on the planet's surface. In fact, such stresses could help life to evolve.

"You don't need an Earth clone to have life," said Dressing.

Since stars live much longer than Sun-like stars, this discovery raises the interesting possibility that life on such a planet would be much older and more evolved than life on Earth.

"We might find an Earth that's 10 billion years old," speculated Charbonneau.

The three habitable-zone planetary candidates identified in this study are Object of Interest (KOI) 1422.02, which is 90 percent the size of Earth in a 20-day orbit; KOI 2626.01, 1.4 times the size of Earth in a 38-day orbit; and KOI 854.01, 1.7 times the size of Earth in a 56-day orbit. All three are located about 300 to 600 light-years away and orbit stars with temperatures between 5,700 and 5,900 degrees Fahrenheit. (For comparison, our Sun's surface is 10,000 degrees F.)

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Modernmystic
1.6 / 5 (18) Feb 06, 2013
???

So if they have a tighter habitable zone this actually makes tidal lock a near certainty which actually REDUCES the chances a planet will be Earth-like (whatever that means this week).

How do they check the temperature of those planets? I wasn't aware we could at this point. I thought we were guessing.

It's not a surprise that 75 percent of the nearest stars are Red Dwarfs because that's about the galactic average....so the "nearness" hook of the article is pretty flat.

I guess I'll never understand the way in which these articles are written.
Maggnus
4.2 / 5 (10) Feb 06, 2013
this actually makes tidal lock a near certainty


Actually, no it doesn't. Until very recently it was thought Mercury was tidally locked because of its nearness to the Sun. While such a planet is more likely to be tidally locked, that is nothing close to "a certainty"

I guess I'll never understand the way in which these articles are written.


Same as most news articles; appeal to the largest number of people in hopes of attracting their interest, thus generating revenue. It's the reason one should look past the article to the actual paper if your interested enough to want to learn what the researcher is saying. News writers are not usually scientists, and their motives are therefore quite different.
dogbert
2.3 / 5 (12) Feb 06, 2013
I wish the term 'earth like' or 'habitable' would stop being used.

It is neither earth like nor habitable just because the temperature range is adequate.

A methane/ammonia atmosphere is not earth like.

Only if there its life will the planet develop a nitrogen/oxygen/carbon dioxide atmosphere.
Parsec
5 / 5 (11) Feb 06, 2013
I wish the term 'earth like' or 'habitable' would stop being used.

It is neither earth like nor habitable just because the temperature range is adequate.

A methane/ammonia atmosphere is not earth like.

Only if there its life will the planet develop a nitrogen/oxygen/carbon dioxide atmosphere.

Actually, while life is almost certainly a requirement for oxygen in the atmosphere, nitrogen and carbon dioxide are not biotic and occur quite frequently.
Aliensarethere
4.6 / 5 (10) Feb 06, 2013
???

So if they have a tighter habitable zone this actually makes tidal lock a near certainty which actually REDUCES the chances a planet will be Earth-like (whatever that means this week).

How do they check the temperature of those planets? I wasn't aware we could at this point. I thought we were guessing.

It's not a surprise that 75 percent of the nearest stars are Red Dwarfs because that's about the galactic average....so the "nearness" hook of the article is pretty flat.

I guess I'll never understand the way in which these articles are written.


Yes the planets are tidally locked, but the temperature can still be alright for life. Earth-like would mean that the size of the planet is close to Earth, and liquid water can exist on the surface.
They haven't found planets close to Earth yet, but they are saying that they should be there. they can't check temperatures directly, but they can estimate the temperature from the distance to the star.
Modernmystic
1.4 / 5 (11) Feb 06, 2013
Yes the planets are tidally locked, but the temperature can still be alright for life.


Not really, most models show any terrestrial atmosphere freezing out eventually on the dark side. Beyond this most red dwarfs are pretty active for the first 1.2 gy and will probably blow off any atmosphere there anyway.

Earth-like would mean that the size of the planet is close to Earth, and liquid water can exist on the surface.


So in other words like Earth in two variables and not the thousand others?

They haven't found planets close to Earth yet, but they are saying that they should be there.


Here's where I'm baffled. Based on what are they making that assumption. I suppose it depends on your definition of Earth like.
Is an Elephant "Mouse Like"? They are both quadrupeds and both mammals.

they can't check temperatures directly, but they can estimate the temperature from the distance to the star.


Depending entirely on atmosphere, which they can't sample...
Modernmystic
1.4 / 5 (10) Feb 06, 2013
Actually, while life is almost certainly a requirement for oxygen in the atmosphere, nitrogen and carbon dioxide are not biotic and occur quite frequently.


I've heard this before and am familiar with the great oxygenation event, but I'm still unclear why it can't simply be elemental oxygen already present in the system via neucleo-synthesis from the super nova remnant the solar system in question is forming from.
Torbjorn_Larsson_OM
3.9 / 5 (8) Feb 06, 2013
Very good article! It hits all the main points that are usually seen as negative, my pet peeves:

- M star early activity can be mooted by atmosphere, and even beneficial (more energy into the habitable system).
- M star habitable planet tidal lock can be mooted by atmosphere, and even beneficial (more energy into the habitable system).
- M star habitable planets with biosphere will outlive larger stars, such as the middle age Sun.

The observed eta (Earth analogs) of ~ 5 % is consistent with early estimates, and not surprisingly ~ 3 times the current Habitable Exoplanet Catalog observation* of ~ 1.6 %.

* Under the current Habitable Zone definition. The HZ definition is undergoing a major revision, and simplification, with the improved GW climate observations. HEC eta will change Feb 18.
JRi
4.7 / 5 (6) Feb 06, 2013
Maybe it is due to reactivity of oxygen. There is much more hydrogen in the universe, so any free oxygen would eventually react with it and form water. I guess.
Modernmystic
1.7 / 5 (9) Feb 06, 2013
- M star early activity can be mooted by atmosphere, and even beneficial (more energy into the habitable system).


Untrue, it's likely the atmosphere would be severely damaged or even blown off by early variability.

- M star habitable planet tidal lock can be mooted by atmosphere, and even beneficial (more energy into the habitable system).


Untrue, tidal lock will probably cause any terrestrial like atmosphere to freeze off of the night side.

- M star habitable planets with biosphere will outlive larger stars, such as the middle age Sun.


Well that would be true if not for all the things that make this unlikely.

http://en.wikiped..._systems
Torbjorn_Larsson_OM
5 / 5 (4) Feb 06, 2013
@MM: - Earth like here is Earth analog - roughly Earth sized, roughly Earth atmosphere (which gives the surface temperatures). Perturbative analysis 101, here of HZ.

- Your "freezing out" backside depends on atmosphere. It is not even clear if it is more constraining (as always, pour in more atmosphere to buffer external effects), it is definitely not excluding.

- The redefinition of HZ will be based on irradiance only, see that paper. (Um, Kasting et al latest. Or wait 2 weeks and check the HEC for details and refs!)

- As JRi suspects, oxygen goes to oxidize minerals (during planet differentiation), then hydrogen to reform water (as they both are released during differentiation et cetera). The only known planets with observed free oxygen, besides inhabited Earth, are hot Jupiters ( > 1000 K, when minerals et cetera starts to decompose).
Torbjorn_Larsson_OM
4.8 / 5 (6) Feb 06, 2013
@dogbert: These terms are defined analysis tools helpful to elucidate facts, not play things for your opinion.

See Perturbative analysis 101 above. Bioproductivity is mainly constrained by liquid water and temperature. Primordial vs modern atmosphere depends on when you observe the biosphere, and if it can develop oxygenating photosynthesis et cetera - secondary concerns.

@MM: No, facts. Just start with more atmosphere, that is the point as I already noted.

Your ref is just repeating all the points that the article made such a good job to hit, my pet peeves because they are largely unsubstantiated concerns as you increase the initial atmosphere mass.
jselin
5 / 5 (5) Feb 06, 2013
Untrue, tidal lock will probably cause any terrestrial like atmosphere to freeze off of the night side.

Wouldn't convection be pretty aggressive in this situation? Depending on the specifics, an equilibrium condition that allows for a residual atmosphere isn't too hard to imagine.
Modernmystic
1.5 / 5 (11) Feb 06, 2013
largely unsubstantiated concerns as you increase the initial atmosphere mass.


From the Wikipedia article....

However, a 2012 study at University of Washington revealed that planets in the habitable zone of red dwarfs would experience such a strong geological tidal heating that the hydrogen necessary for water and all known life would be 'baked out' of the planets before a stable orbit could be achieved, creating so-called 'Tidal Venuses'. This holds for red dwarfs with masses less than 30% of the Sun's mass. Tidal heating shifts the habitable zone outward. Orbit instability complicates the issue. [1] Combined with the other problems of tidal locking, variable radiation, axial tilts,[3] etc., this would make the probability of many red dwarf stars hosting life as we know it very low compared to other star types.[2]


And more atmosphere would likely only exacerbate that situation....

Blithe ignorance of hard facts about these systems baffles me. Worse than creationists.
Modernmystic
1.5 / 5 (8) Feb 06, 2013
Untrue, tidal lock will probably cause any terrestrial like atmosphere to freeze off of the night side.

Wouldn't convection be pretty aggressive in this situation? Depending on the specifics, an equilibrium condition that allows for a residual atmosphere isn't too hard to imagine.


Let's say for the sake of argument I concede the point. Can you imaging the constant gale force winds and torrential rains (assuming there's any water at all after the tidal heating) in order to balance the system? Simple life in a lake on the terminator? MAYBE. Complex life of any sort? Highly unlikely...
Modernmystic
1.5 / 5 (8) Feb 06, 2013
In any case all of this should be academic. It's interesting to speculate, but if you want to find an "Earth like" planet here's what you need to do.

Look around an SOL type STAR first of all....
This means metalicity
This means mass
This means variability
This means age
This means galactic neighborhood
This means those and about twenty other things they're not talking about in this article....
typicalguy
5 / 5 (3) Feb 06, 2013
All planets will eventually become tidally locked with their host star. The Earth hasn't always had a 24 hour day - it was a shorter day because the Earth's rotation was faster. If the Earth/Sun system lasted long enough, the Earth would become tidally locked but the projected age that this tidal lock occurs is after the Sun expands and destroys the Earth so it won't happen on Earth.

Point being, if the planet has ample rotation then it would take a very long time for tidal lock to occur. A sufficiently advanced civilization could (in theory) increase the speed of their planet as well. It would be incredibly expensive but if you've only got one planet and you have the capability then you probably do it.
bagelverse
not rated yet Feb 06, 2013
These would be exoplanets sound alot like Frederick Pohl's JEM
marble89
4.7 / 5 (3) Feb 06, 2013
A thought experiment: If earth were tidally locked to the sun the atmosphere would NOT freeze out on the anti-sun hemisphere. The redistribution of heat by the hundreds of times more massive hydrosphere would prevent this. Only a small fraction of earth's hydrosphere would be able to freeze out on dark continents because of limits on the thickness of ice sheets before they begin to flow

VendicarE
3.8 / 5 (5) Feb 06, 2013
They are university press releases for the most part. Written by the journalism staff who are ignorant of science, and are looking to practice their language, and promote the university, rather than provide a synopses of a published paper or research.

"I guess I'll never understand the way in which these articles are written." - Mystic
Sinister1811
1.9 / 5 (12) Feb 07, 2013
I tend to agree with Modernmystic on some points. I think that the term "Earth-sized" would be more accurate than "Earth-like", which, at this point is unable to be determined. Only better telescopes/technology will be able to tell us if these planets are remotely similar to Earth, or whether they're like Mercury, Venus or Mars, or even the moons of some of the gas giants. Who knows? They could even be entirely different to anything we've seen in our own solar system.
vlaaing peerd
4.3 / 5 (3) Feb 07, 2013
so with current and a little near future technology we should be able to get there in some 300~400 years of travel.

Doesn't sound too bad.
Whydening Gyre
1.7 / 5 (11) Feb 07, 2013
It sounds like you all believe carbon-based bags of mostly water are the only game in town.
Sheesh - get a life...
Anda
4 / 5 (3) Feb 07, 2013
Very "interesting" comments as always.

Anyway, the fact is that we are closing the gap but only very few CONFIRMED earth-sized exoplanets have been found yet.
And the ones in the article are only candidates, so the main statistic in this article cannot be confirmed...
Andragogue
3 / 5 (3) Feb 07, 2013
I want to go on record here: I believe the name, "Red Dwarf", is derogatory. We should use the term "Ruddy Little Star" instead.
philw1776
3 / 5 (4) Feb 07, 2013
Tidal locked planets around a M red dwarf. One side faces an immobile sun, depending on your location the sun is overhead or at an angle, forever. The subsolar circle at the equator gets max heat and may be a source of super hurricanes while a ring around the circumference is the coldest with the sun low near the horizon and eternal winds as the atmosphere and oceans transfer heat to the eternal darkness of the cold side. Temperate climate rings lie between the two extremes and are probably also buffeted by winds as the atmosphere does its unceasing job of heat transfer.

There could be planets who escape tidal lock and have a resonance rotation like Mercury but were there any oceans the hundreds of meter high tides would sweep any land masses. Volcanoes would abound as the internals would be heated by the star's tidal energy transfer.
cyberCMDR
not rated yet Feb 07, 2013
I say we officially name the most apparently viable planet found around a red dwarf Krypton (as in the Superman mythos). Might get more kids interested in astronomy.
rockwolf1000
2.3 / 5 (3) Feb 07, 2013
I would think if the planet was in tidal lock, any liquid water would be transferred to the dark side in the form of snow or ice and be sequestered there for eternity thus completely depleting all available water on the light side rendering it in a permanent state of desertification.
Tcobb
5 / 5 (1) Feb 07, 2013
Just because a body is in a tidal lock doesn't mean it can't have a night and day cycle. Consider the earth's moon. Its in a tidal lock to the earth but it does have a day-night cycle, and this would persist regardless of whether earth itself was tidally locked to the sun.

We have evidence for large gas giant type planets orbiting stars at fairly close distances to their stars. They could easily have moons of earth size that are capable of maintaining an earth-like atmosphere. And they can have a day-night cycle.
Trenchant
1 / 5 (1) Feb 09, 2013
Is there a theoretical (or proven) level of gravity that prevents life as we know it?
Fleetfoot
5 / 5 (4) Feb 09, 2013
Is there a theoretical (or proven) level of gravity that prevents life as we know it?


Too low and a body would struggle to retain an atmosphere (e.g. Mars) but I don't see a simple argument for an upper limit. We don't know enough about the constrains on life to be sure about that.
marble89
5 / 5 (3) Feb 09, 2013
life forms in oceans evolve almost entirely independent of gravity
Tausch
1 / 5 (2) Feb 09, 2013
lol
...til the less intelligence cells of life 'asked' their adaptive features to come up with a working model labeled buoyancy by low life forms such as us.

Our adaptive features are too smart for their own good.
Good thing too.
Mike_Massen
4.2 / 5 (5) Feb 09, 2013
dogbert mumbled again, with
It is neither earth like nor habitable just because the temperature range is adequate.
A methane/ammonia atmosphere is not earth like.
You do realise the early Earth had a sizable amount of Ammonia, H2, CH4, O2.
All our proteins are made from Amino Acids & all of those have an NH2 (ie Ammonia less an H for bonding) - gee "I wonder where that came from" ?

Several enzymes (proteins all made from amino acids) which are involved with methylation ie Adding CH3 radical where needed & others the opposite. Quite a lot of ammonia/methane interactions, we came from the early Earth. ie Straightforward chemistry...

If you look at the vast permutations & atmosphere of the early earth & the amount of oxygen plus in the various rocks, its inevitable complex chemical interactions occur, inspired by lightning & environments & perturbations.

Life is just complex chemistry but we haven't yet worked out the wide area of details re hugely massive permutation space !
dogbert
1 / 5 (7) Feb 10, 2013
Mike_Massen,

Yes, the earth did have a methane/ammonia atmosphere at first.

Life changed our atmosphere to a nitrogen/carbon dioxide/oxygen mix.

You make my point. Unless a planet contains life, that planet cannot be like our current earth.

We have not found life anywhere except in this solar system. Therefore, there is no logical reason to suspect any of these planets of being earth like.
Fleetfoot
5 / 5 (6) Feb 10, 2013
You make my point. Unless a planet contains life, that planet cannot be like our current earth.

We have not found life anywhere except in this solar system. Therefore, there is no logical reason to suspect any of these planets of being earth like.


So by your logic, when the Earth first formed, it wasn't Earth-like.

The term in astronomical usage refers only to temperature, basic composition and mass. Every field has its own jargon.
dogbert
1 / 5 (7) Feb 10, 2013
Fleetfoot,
The term in astronomical usage refers only to temperature, basic composition and mass. Every field has its own jargon.


If you want to call uninhabitable planets earth like, you may, but the term is used to indicate worlds like the earth.

The title "Earth-like planets are right next door" is only exciting if the planets are actually like earth.

Fantasy and delusion is fun but it does not belong in a scientific publication.
Fleetfoot
5 / 5 (4) Feb 10, 2013
Fantasy and delusion is fun but it does not belong in a scientific publication.


That is the point, in a scientific publication one should use the scientific definition of "Earth-like". You may not agree with the common scientific usage but it is what it is and is used correctly in the article. The early Earth clearly was habitable despite having a methane atmosphere because it was early forms of life that converted it to oxygen based.
dogbert
1 / 5 (6) Feb 10, 2013
Fleetfoot,
That is the point, in a scientific publication one should use the scientific definition of "Earth-like".


There is no such scientific definition. Earth like means like the earth, habitable by man.

The free online dictionary:
earthlike - resembling or characteristic of earth; "earthlike atmosphere"
Mike_Massen
3 / 5 (8) Feb 10, 2013
dogbert got part way
Life changed our atmosphere to a nitrogen/carbon dioxide/oxygen mix.
Surely you mean simple chemistry growing RNA/DNA base pair,
http://en.wikiped...creation

dogbert lumbered with
You make my point. Unless a planet contains life, that planet cannot be like our current earth.
No, don't tell fibs now, read my comment.

dogbert's ignorance shows
We have not found life anywhere except in this solar system.
No, amino acids, of which we are made located by spectroscopic analysis of gas clouds outside our solar system.

dogbert's attempt at very bad logic, shows he doesn't understand process of logical enquiry, inference or deduction
Therefore, there is no logical reason to suspect any of these planets of being earth like.
Clarifying for dogbert & those like him/her, if a planet is in the habitable zone & has the necessary compounds, even early on it is Earth like & is likely to produce DNA/RNA base pairs easily !
dogbert
1.4 / 5 (9) Feb 10, 2013
Mike_Massen,
Clarifying for dogbert & those like him/her, if a planet is in the habitable zone & has the necessary compounds, even early on it is Earth like & is likely to produce DNA/RNA base pairs easily !


Wrong and wrong.

1) Being in the so called 'habitable zone' does not mean it is habitable because it must have an oxygen atmosphere to be habitable. To have an oxygen atmosphere, it must have life to create that atmosphere.

2) There is no indication that life exists anywhere but in this solar system, so your assertion that life will arise is based on nothing at all.

It would be nice if life were abundant and everywhere we looked we found life. But we have failed to find life anywhere at all except here. So wishing that life were abundant is just that -- wishful thinking.
Humpty
1 / 5 (6) Feb 11, 2013
All hocus pocus and bullshit - unless we have a time space drive that can pull a few hundred light years an hour... we ain't going NO WHERE.
antialias_physorg
4.1 / 5 (7) Feb 11, 2013
unless we have a time space drive that can pull a few hundred light years an hour... we ain't going NO WHERE.

Not in our present form at any rate.

However, one could imagine that there are ways of sending seed-ships, or ourselves coded in some form. In that case you could go as slow as you want (with the proviso that the vessel has some way of ensuring that defects can be repaired or it otherwise impervious to radiation/microdebris damage for the duration...like using a hollowed out asteroid or somesuch).

So wishing that life were abundant is just that -- wishful thinking.

So is the opposite. We have barely looked anywhere. At the moment stating that life is unique is as much wishuful thinking as that life is ubiquitous. We currently just don't know.
dogbert
1.6 / 5 (7) Feb 11, 2013
No. Arguments based on the evidence are superior to arguments based on desire.
Fleetfoot
5 / 5 (4) Feb 11, 2013
Earth like means like the earth, habitable by man.


In astronomy, it means having a similar mass and surface temperature as Earth.

The other common term, "habitable", means capable of supporting life, but again it is any form of life, not just human. I don't think we have a term for what you are considering.
dogbert
1 / 5 (5) Feb 11, 2013
We do have such a term: 'earth like' is one term. 'habitable' its another term.
Modernmystic
1.7 / 5 (6) Feb 11, 2013
So is the opposite. We have barely looked anywhere.


True at one point not so long ago. This line is starting to wear thin with recent observations...

At the moment stating that life is unique is as much wishuful thinking as that life is ubiquitous. We currently just don't know.


What we do know is that only one out of eight planets (not counting moons) has life. That is our OBSERVATION. Everything else might be termed speculation and/or wishful thinking.

I see no reason why simple life shouldn't be abundant in the universe. Complex life is another matter, and intelligent life is another matter ENTIRELY. However that's just my opinion based on what we're seeing. It might be that the Earth is "it" in the universe.

These debates are about world view almost entirely. Which is why you get very intelligent people arguing that red dwarf systems are a good place to look for life....
Fleetfoot
5 / 5 (4) Feb 11, 2013
We do have such a term: 'earth like' is one term. 'habitable' its another term.


See my previous post, neither of those restricts the classification to being suitable for humans.
Fleetfoot
5 / 5 (3) Feb 11, 2013
At the moment stating that life is unique is as much wishuful thinking as that life is ubiquitous. We currently just don't know.


What we do know is that only one out of eight planets (not counting moons) has life. That is our OBSERVATION. Everything else might be termed speculation and/or wishful thinking.


The trouble is that that is a single observation and it is almost impossible to draw any meaningful conclusions from it.

I see no reason why simple life shouldn't be abundant in the universe. Complex life is another matter ..


No reason at all, there could be millions of life-bearing planets in our galaxy, simple or complex.

.. and intelligent life is another matter ENTIRELY.


Even the definition of "intelligent" is tricky in this context.

However that's just my opinion based on what we're seeing. It might be that the Earth is "it" in the universe.


In the galaxy perhaps, but if the universe is flat, it is also spatially infinite ...
Modernmystic
1.7 / 5 (6) Feb 11, 2013
The trouble is that that is a single observation and it is almost impossible to draw any meaningful conclusions from it.


Of course we can. We know of one place that life exists. If we knew of even two places it would change the theoretical landscape significantly.

No reason at all, there could be millions of life-bearing planets in our galaxy, simple or complex.


Complex life didn't make an appearance on Earth until quite recently. It could be that it's quite difficult for it to come about. Simple life seems to have popped up as soon as it could.

Even the definition of "intelligent" is tricky in this context.


No so IMO. But I could be wrong.

In the galaxy perhaps, but if the universe is flat, it is also spatially infinite .


Not so. Finite but unbounded...
Fleetfoot
5 / 5 (2) Feb 11, 2013
The trouble is that that is a single observation and it is almost impossible to draw any meaningful conclusions from it.


Of course we can. We know of one place that life exists. If we knew of even two places ...


Ah but we don't, that's the problem.

No reason at all, there could be millions of life-bearing planets in our galaxy, simple or complex.


Complex life didn't make an appearance on Earth until quite recently. It could be that it's quite difficult for it to come about.


Or it could be that it takes a large number of reasonably probable steps in which case most planets would make the transition around the same age, again we have insufficient data to say which applies.

In the galaxy perhaps, but if the universe is flat, it is also spatially infinite.


Not so. Finite but unbounded...


Nope, flat or negative curvature implies it is spatially infinite, it is finite/unbounded only if it has positive curvature.
Modernmystic
1 / 5 (5) Feb 11, 2013
Ah but we don't, that's the problem.


Indeed, thanks for re-iterating my point...

Or it could be that it takes a large number of reasonably probable steps in which case most planets would make the transition around the same age, again we have insufficient data to say which applies.


I agree we have insufficient data, but the data points to it being more difficult than easy as opposed to simple life. The bias isn't in its favor at the moment. To suggest otherwise is to blatantly ignore the data.

Nope, flat or negative curvature implies it is spatially infinite, it is finite/unbounded only if it has positive curvature.


Something that's expanding at a finite speed for a finite time reaches spatial infinity?

Infinity exists in ivory towers of philosophers, it's doubtful it actually exists anywhere else. This is why when physicists encounter it in their equations they know they don't have the full picture and they've always been right about that thus far.
Fleetfoot
4.3 / 5 (6) Feb 11, 2013
The bias isn't in its favor at the moment. To suggest otherwise is to blatantly ignore the data.
No, we have only a single data point, so it is not possible to infer anything other than that the probability is non-zero. It's counter-intuitive but sadly true.

Nope, flat or negative curvature implies it is spatially infinite, it is finite/unbounded only if it has positive curvature.


Something that's expanding at a finite speed for a finite time reaches spatial infinity?


There is no limitation to finite speed.

If the curvature is positive, the geometry is that of a 4-sphere which has a finite volume at any time. If it is negative, it is a hyperboloid (like a saddle shape) which is and always has been infinite. We know that the density is within 0.4% of flat which is also infinite. See the shapes here and the comments at the bottom:

http://map.gsfc.n...ape.html

Again, the correct scientific answer is "we don't know yet".
Modernmystic
1 / 5 (6) Feb 11, 2013
No, we have only a single data point, so it is not possible to infer anything other than that the probability is non-zero.


Indeed not, we can say that of eight planets and 19 odd moons where lift might be plausible only ONE has developed life. It's rare and the conditions necessary for it are obviously not trivial.

As to complexity the single data point we have clearly suggests that complex life requires at least simple life and a set of stable conditions for billions of years...so it IS going to be more rare still. This isn't complicated, but it's amazing how obviously intelligent people need things to fit their world view to feel comfortable. One of these appears to be a viceral need for the principle of mediocrity to be true for life. It may not be.
As to the infinite universe, sorry I don't believe in infinity for the same reasons I don't believe in god. They are both human invented fictions and by their own definitions non concepts and can't exist in any real sense
Whydening Gyre
1 / 5 (7) Feb 12, 2013
Not so. Finite but unbounded...

So... a REALLY BIG proton (or group of photons) travelling through some NEW infinite space not yet defined..
Hmmm... sounds like a new bigger picture thing to me...
Modernmystic
1 / 5 (4) Feb 12, 2013
Not so. Finite but unbounded...

So... a REALLY BIG proton (or group of photons) travelling [sic]through some NEW infinite space not yet defined..
Hmmm... sounds like a new bigger picture thing to me...


No a really big three dimensional sphere, if you travel far enough you end up back where you started. There is no boundary just curvature.
Whydening Gyre
1 / 5 (6) Feb 12, 2013
Not so. Finite but unbounded...

So... a REALLY BIG proton (or group of photons) travelling [sic]through some NEW infinite space not yet defined..
Hmmm... sounds like a new bigger picture thing to me...


No a really big three dimensional sphere, if you travel far enough you end up back where you started. There is no boundary just curvature.

Well, there IS that pesky .04 percent per so many light years...
Fleetfoot
5 / 5 (1) Feb 12, 2013
No, we have only a single data point, so it is not possible to infer anything other than that the probability is non-zero.


Indeed not, we can say that of eight planets and 19 odd moons where lift might be plausible only ONE has developed life.


On the contrary, only one body in the Solar System has copious liquid water, the score is 1 out of 1 which says little.

This isn't complicated, but it's amazing how obviously intelligent people need things to fit their world view to feel comfortable. ... As to the infinite universe, sorry I don't believe in infinity for the same reasons I don't believe in god.

Don't worry, I won't threaten your world view.
Modernmystic
1 / 5 (4) Feb 12, 2013
On the contrary, only one body in the Solar System has copious liquid water, the score is 1 out of 1 which says little.


It actually says a lot if you really think about it. Only 1/27 has the right conditions for life.

Don't worry, I won't threaten your world view.


I'm sorry I did yours...
Fleetfoot
5 / 5 (1) Feb 13, 2013
On the contrary, only one body in the Solar System has copious liquid water, the score is 1 out of 1 which says little.


It actually says a lot if you really think about it. Only 1/27 has the right conditions for life.


From exoplanet data, the number is probably much smaller than that. That is a factor for which we do have reasonable data though it is still heavily biased against small planets and long orbits.

Don't worry, I won't threaten your world view.


I'm sorry I did yours...


Not in the slightest, I don't think you have any idea what my views are. All I have pointed out is that you have extrapolated beyond what is valid for the statistics.
Modernmystic
1 / 5 (4) Feb 13, 2013
From exoplanet data, the number is probably much smaller than that. That is a factor for which we do have reasonable data though it is still heavily biased against small planets and long orbits.


I agree, and further still without the benefit of spetrographic information on said planets atmospheres it shows extreme hubris to call any of them Earth-llike.

All I have pointed out is that you have extrapolated beyond what is valid for the statistics.


I think the vastness of the universe can be the intellectual version of an optical illusion. The universe looks big to us because we're small compared to it...that's all really. Sheer size is not a sufficient argument from mediocrity. IMO quite the contrary there's a good criticism of it here...

http://en.wikiped...ial_life
Fleetfoot
5 / 5 (1) Feb 13, 2013
From exoplanet data, the number is probably much smaller than that. That is a factor for which we do have reasonable data though it is still heavily biased against small planets and long orbits.


I agree, and further still without the benefit of spetrographic information on said planets atmospheres it shows extreme hubris to call any of them Earth-llike.


That only means similarity of mass and temperature, people read too much into the term.

All I have pointed out is that you have extrapolated beyond what is valid for the statistics.


I think the vastness of the universe can be the intellectual version of an optical illusion. The universe looks big to us because we're small compared to it...that's all really. Sheer size is not a sufficient argument from mediocrity.


But I have not argued either for or against mediocrity, I only pointed out you were over-extrapolating from insufficient data.
Modernmystic
1 / 5 (5) Feb 14, 2013
That only means similarity of mass and temperature, people read too much into the term.


Then people should quit using the term. Unless of course it's their intention to mislead.

I can say that cats are very dog-like based on two variables out of a thousand. They're both quadrupeds and they're both mammals. I might do this if I were trying to convince cat lovers that dogs were nice animals too...I wouldn't do it to convey any since of accuracy or truth.

But I have not argued either for or against mediocrity, I only pointed out you were over-extrapolating from insufficient data.


I guess there we might have to agree to disagree. I think that the data does have a bias and while it appears it might be in favor of simple life being "common" in those areas where it's possible to exist. Not so for more complex life, given data and our knowledge of the variables. Maybe I'm just trying to balance the rose colored view of the situation, because it's not rosy at all.
Fleetfoot
5 / 5 (1) Feb 14, 2013
But I have not argued either for or against mediocrity, I only pointed out you were over-extrapolating from insufficient data.


I guess there we might have to agree to disagree. I think that the data does have a bias and while it appears it might be in favor of simple life being "common" in those areas where it's possible to exist. Not so for more complex life, given data and our knowledge of the variables.


Let's say it took 3Ga for complex life to develop on Earth. Consider these two statements:

a) Most life needed 30Ga to switch from unicellular to complex, Earth was on the early tail of the distribution.

a) Most life needed 300Ma to switch from unicellular to complex, Earth was on the late tail of the distribution.

We might know which is true after we send out probes to survey every star in the galaxy, but with only one data point the two possibilities cannot be distinguished. Complex life might be rare or ubiquitous, all I am saying is that we can't tell.
antialias_physorg
3 / 5 (2) Feb 14, 2013
We should also be aware that intelligence does not seem to be a path that is likely in evolution. Consider that there have been long periods in history where nothing much happened in that direction (more than 100 million years of dinosaurs never getting brains bigger than absolutely necessary to hunt prey. A billion years where everything was more or less unicellular, etc.).

And that it was just a 'lucky' accident that wiped the dinosaurs out that made a niche where intelligence could develop.

So one might posit that without (extraneous) lucky accidents intelligence might not develop at all - which would drop the ratio of intelligent species to lifebearing planets right down into the 'pretty darn small' category.
Fleetfoot
5 / 5 (1) Feb 15, 2013
We should also be aware that intelligence does not seem to be a path that is likely in evolution. Consider that there have been long periods in history where nothing much happened in that direction (more than 100 million years of dinosaurs never getting brains bigger than absolutely necessary to hunt prey. A billion years where everything was more or less unicellular, etc.).

...

So one might posit that without (extraneous) lucky accidents intelligence might not develop at all - which would drop the ratio of intelligent species to lifebearing planets right down into the 'pretty darn small' category.


Good point, I couldn't agree more. That's definitely the factor that we understand least, why did no dinosaur ever build a radio-telescope?

That and the possibility that any species that achieves our level of intelligence can probably find a way to survive the demise of their home star mean that those terms in the Drake Equation are useless.