The continuously habitable zone: Earth's life sustainability

[unbreakable2008]

Its ok man, just pulling you leg.... I actually like your videos, i just wanted to see how you would react to different opinions. Lets call it a social experiment. I have been in your shoes many times, saying things in a calm and validated way within parameters that I define, then comes a nutcase saying stuff out of the blue. You have get used to this my friend... there are a lot of people out there who do not think or have different backgrounds... you cannot persuade them all. Be well...-K

[unbreakable2008]

"If you continue to ignore my points (even while quoting them, ironically enough), then I would prefer that you leave." Oh the words of someone who is somewhat intelligent but thinks he knows everything..... lol, you are not mentally equipt to handle people who push you mentally around and this will be your downfall! You have a superiority complex, better drop it. Signs of a loser. Dont worry, you bore me... I just responded to have fun. Have fun talking to yourself! :-)

[SecularAstronomer]

@unbreakable2008

“Oh the words of someone who is somewhat intelligent but thinks he knows everything..... lol.”

Of course I don’t know even nearly everything. This is an emotional response.

“You are not mentally [equipped] to handle people who push you mentally around and this will be your downfall! You have a superiority complex, better drop it.”

This is grandiose rhetoric. I gave a detailed response to your points. Please address them.

[SecularAstronomer]

“Signs of a loser.”

You are being petty. Don’t let anger get the better of you.

“Don’t worry, you bore me... I just responded to have fun. Have fun talking to yourself! :-)”

You just accused me of having a superiority complex and now you are condescending to me? Again, please just address my points.

[SecularAstronomer]

I shall summarize my points, for ease of response:

I agree that life can be far more diverse and commonplace than the one example of Earth and its inhabitants. I agree with much of what you say about life and its possible ranges, and I only use the liquid water criterion to dispel the argument life can only be here on earth (one you also disagree with) by establishing a conservative estimate based on the observed example of earth.

[unbreakable2008]

There have been found life forms in the deep crust inside earth, there have been found lifeforms that need no water, or sun or oxygen, some can live in space for long periods of time, they have found them even in nuclear reactors THRIVING!!!.... lol Aminoacids that are the building blocks of life have been found on meteorites.... Your hypothesis is too limited, thus you are removing all possibility of life that is NOT how we know it... Since the number of planets are virtually unlimited...

[unbreakable2008]

You take into account only the inner solar system planets, not all of them, just because life as we know it can only exist on a solid planet it does not mean that it cannot exist on a gaseous planet, therefore your estimate is incorrect, and it is correct that the band of which is "habitable" is extremely thin, and we are right smack in the middle of it, not on the edges... being on the edges would make it "possible" to support some sorts of life but not have the plethora of animals as earth.

[unbreakable2008]

@unbreakable2008 I just hate it when people slur scientific information in order to prove a point....

Be brave and say things like they are. Compare the habitable zone area with the total radius of the solar system. Then you will see that its faaarrrr smaller than 10%.

I am wondering WHY ON EARTH you want to dispute this by twisting information? Perhaps you have some agenda, if so please make it clear what the agenda is.

[SecularAstronomer]

@unbreakable2008

I don’t know how I managed to miss your comment for nearly 3 months, but I will gladly respond now that I have noticed it:

[SecularAstronomer]

“You take into account only the inner solar system planets, not all of them, just because life as we know it can only exist on a solid planet…”

Of course I did; because I was calculating a lower boundary by generating a conservative estimate. Not only was this contextually obvious, given this is a refutation of an argument that the CHZ is only a few meters, but I also explicitly stated this in the video:

[SecularAstronomer]

“And although is it probably considerable larger, a very conservative estimate puts it extending from about 0.95 AU at its inner edge, to about 1.15 AU at its outer edge (Kasting, Whitmire, & Reynolds, 1993).”

--Me (in this very video)

[SecularAstronomer]

“…it does not mean that it cannot exist on a gaseous planet, therefore your estimate is incorrect…”

This is quite obvious. And no, that doesn’t mean it is wrong; because (again) it’s an inferred lower bound from a conservative estimate. I take it you didn’t read the research publication I cited by Dr. Kasting and his colleagues.

[SecularAstronomer]

“...and it is correct that the band of which is "habitable" is extremely thin, and we are right smack in the middle of it, not on the edges... being on the edges would make it ‘possible’ to support some sorts of life but not have the plethora of animals as earth.”

On what data is that hypothesis based? Remember; I’m not discussing the broader term ‘circumstellar habitable zone.’ Rather, I’m discussing the ‘continuously habitable zone,’ in which (by definition) habitability isn't time-dependent.

[SecularAstronomer]

“I just hate it when people slur scientific information in order to prove a point....”

There is nothing unscientific or inaccurate about the concepts of upper/lower bounds and conservative estimates. Quite the contrary; they are invaluable in science.

“Be brave and say things like they are.”

I have; the lower bound is the “very conservative estimate [putting the CHZ] extending from about 0.95 AU at its inner edge, to about 1.15 AU at its outer edge.”

[SecularAstronomer]

“Compare the habitable zone area with the total radius of the solar system. Then you will see that its faaarrrr smaller than 10%.”

That would be a mistake. Since I was generating a lower bound via conservative estimate, I had to use the key condition which has been observed to have produced life; liquid water. Thus the calculation only included the phase-range of water. To compare water’s liquid-range to an area including that which it is irrelevant (jovian planets) would be meaningless.

[SecularAstronomer]

Also, any CHZ is only relevant in a sun-proximity dependent model. Possibilities such as liquid water via tidal forces are independent of sun-proximity, thus the CHZ is irrelevant to them. Expanding the scope to include such possibilities would make the sun-proximity ratio meaningless.

[SecularAstronomer]

What I compared was water’s liquid-range to the area with a high likelihood of producing planets where water’s liquid-range is relevant (terrestrial planets). Again, I was conservative in using the liquid water criterion, and did so for the purpose of generating a lower bound.

[SecularAstronomer]

“I am wondering WHY ON EARTH you want to dispute this by twisting information? Perhaps you have some agenda, if so please make it clear what the agenda is.”

I have twisted nothing, and I resent such false accusations, unbreakable2008.

[unbreakable2008]

@SecularAstronomer since the number of planets are virtually unlimited you probably have many ways of forming life, that will be different from our own. You have only ONE example to go by, and that is earth. Extrapolating from one example to ALL the frikin universe is non sequitar. You must stop motormouthing and start thinking differently for a while. I say the planets are unlimited, because although we estimate the size of the universe this estimate is probably incorrect, because that only....

[unbreakable2008]

That only means that light has traveled to us from that point on, from there on there is darkness because light has not traveled long enough for us to see it! There is no proof that there is a boundary to our universe or a specific number of stars, or planets, in fact in the case of infinity, there is nothing to say that the actual laws of physics continue to be constant in the universe, they may change. I have no proof of this... but you are like a text book of the 1900s. reminds me small minds

[unbreakable2008]

@SecularAstronomer "Again, I was conservative in using the liquid water criterion, and did so for the purpose of generating a lower bound." Your assumptions are the problem. Think out of the box. I can tell you this that is a certainty. The universe is not stranger than you imagine, its stranger than you CAN imagine. --Arthur C. Clarke. While I understand your need to explain this information, it can be found on many documentaries and books. I ALREADY KNOW what you are saying but its not enough

[SecularAstronomer]

@unbreakable2008

“Since the number of planets are virtually unlimited you probably have many ways of forming life, that will be different from our own…”

I already agreed with this. Please pay attention.

“You have only ONE example to go by, and that is earth. Extrapolating from one example to ALL the frikin universe is non [sequitur].”

Did you even read what I typed? Extrapolating from a baseline establishes a lower bound. Do you not understand such basic scientific terminology?

[SecularAstronomer]

“You must stop motormouthing and start thinking differently for a while.”

Again, I agreed with your statements about the plausibility of diversity and range. Please pay attention.

“…you are like a text book of the 1900s. Reminds me small minds.”

I established a vital baseline from which further inquiry can be made. Your failure to grasp this reminds me of my many discussions with the scientifically illiterate.

[SecularAstronomer]

“Your assumptions are the problem. Think out of the box.”

One always works tentatively from an observable starting point, so as to establish a baseline. This is basic science. I obviously don’t cling to the parameters of the analysis. “Thinking outside the box” is what one does after departing from the baseline. This video only establishes the baseline so as to refute an invalid argument that you also disagree with. You would see this if only you would cease being so pigheaded about the mater.

[SecularAstronomer]

It is clear that you either don’t know what a conservative estimate and lower bound is, or you didn’t put any thought whatsoever into what I said. If you continue to ignore my points (even while quoting them, ironically enough), then I would prefer that you leave.

[Finnlander132]

"C.H.C." wtf , I've never heard of it being called that before. Don't make up words.

[SecularAstronomer]

@Finnlander132

I said "continuously habitable zone, or CHZ." The letters CHZ were even on the screen. That you actually managed to get this wrong show how little you were paying attention.

The fact that you don't know what CHZs are shows your ignorance of astrophysics. The fact that you think if you don't know the term, it must not exist shows a revolting level of arrogance of this topic you are so ignorant of.

[SecularAstronomer]

And finally, the fact that you could have seen the term used in astrophysical literature by simply clicking a link to one of my references in the video description area shows your laziness.

I would prefer not to be falsely accused of fabrication/deception by anyone; but especially not someone so oblivious, ignorant, arrogant, and lazy.

[FailingTube]

I think the more important issue in terms of the sustainability of Earth is the exponentially increasing population and pollution of our planet. We are currently behaving like a virus with shoes. In order to maintain sustainability, a major de-populization needs to take place in order to create a balance, a perpetual harmony with nature and the resources available. Once this is established, there will be no pressure on science & technology to look for new settlements on other planets.

[MicrosoftsourceCode]

Hey guy you talk too fast to make any fucking sense. I was going to suggest a way of measuring the gravity produced by planet but you got to slow down a bit. I got the idea from watching you video on gravity and how an object might lose it gravitationalpull. Message me and I might still have that idea.

[jellybeansinc]

Could you elaborate, because it is "known" that anything that has mass has a gravitational field.

[MicrosoftsourceCode]

I am sorry but I lost the plot to this one

[longhairedartist]

What is the likelihood of a renegade dwarf star system entering the early solar system and being captured in a cometary motion, hiding out mostly in the Oort cloud? And what if one of said dark star's renegade planets collided with the former earth, yielding the moon and asteroid belt? And is there a likelihood that Venus was originally a large comet that sucked the moist atmosphere of Mars and donated it to Earth on passing? If such unlikely events happened, would life be a miracle?

[clo234]

so you are pretty much a smart guy. thats what i gather from this

[Cypherus21]

Good argument. What I cannot get an answer from is the obviousness of the moon being in the habitable zone like Earth but the moon is devoid of any earth like features. Both celestial bodies evolved under the same conditions: early volcanism; a hydrogen atmosphere before burned away from Sun, etc.

It's like the twin analogy - one offspring took all the good genes and left the twin with nothing. What is your theory regarding this issue?

[jsyomama]

The pull of gravity on the moon's surface is only about 17% as that of Earth. My understanding is that this is simply not enough force to maintain an atmosphere.

[Grysham]

As mentioned above, the moons size and density are relatively small. While it has a gravitational pull, that force is relatively low. Because of that the moon can't maintain an atmosphere of any kind, or any atmosphere that is has is weak. The moon is more like an asteroid than a planet.

[Cypherus21]

That makes sense, but Europa has a tenuous atmosphere composed primarily of oxygen despite its small mass like the moon. It is more likely that the moon did not evolve with Earth, but was captured. But then Earth is so small that it would be difficult to capture a celestial body the size of the moon. It definitely is a mystery.

[Grysham]

Thats well noticed, the two are similar in size. However there are some large differences between the two. Europa's surface is covered with a layer of ice, beneath which is believed to be a liquid ocean. Europa's atmosphere is made primarily of oxygen, which is most likely emited from the ice due to solar radiation. Its atmosphere is caused more by that than its gravity, and its still a very slight atmosphere at that. The moon has no gas emitions and so no way for an atmosphere to form.

[Cypherus21]

Europa's oxygenated atmosphere is not caused by solar radiation, but by tidal locking with Jupiter that generates enough sub-surface heat energy to cause the rippling of ice. While Europa is different from our Moon today, our Moon in the past shows evidence of volcanic activity that would produce atmospheric conditions, notably water vapor. I suppose that because our moon is closer to the Sun than Europa, its atmosphere burned off given its tenyous gravitational hold.

[Grysham]

Ahh, yes your right it is tidal locking not solar radiation. Interesting to think Europa could possibly contain life given its liquid oceans.

[0PsycoDad0]

Can you plz tell the source of the graph yopu used on ~2:31?

Besides does it include notes on captured rotation (f.ex. rates of slowdown, point of capture)?

[Warthaug]

Excellent video (one of many of yours I've enjoyed this morning).

Quick question you may (or may not) know the answer to - is their a source which has CHZ's calculated for the different stellar classes? I understand that for the really small stars there isn't really a CHZ (due to captured rotation), but I've never seen quantification of this.

Thanx, both for an excellent video and hopefully for an answer...

[82abhilash]

I got wondering when I saw this video. The moon falls within our CHC yet it has no life in it. Comments please.

[82abhilash]

Never mind. Falling within the CHC can be only a necessary not a sufficient condition for life. Having said that I am sure I may have inadvertently created a niche for the 'God of the Gaps' argument.

[SecularAstronomer]

Our moon doesn't have enough mass to retain an atmosphere. With no atmosphere, any water evaporates immediately when light hits it, and is lost to space. When in shadow, the lack of heat retention due to the lack of atmosphere causes it to immediately freeze.

Also, the Moon has no churning liquid iron core, so it has no magnetosphere, and thus, has no protection from the sun's solar wind.

p.s. I think that should adequately crush any such argument.

[FailingTube]

@SecularAstronomer Did you major in astro physics?

[reesnixon]

Please address the fact that many of the exoplanet systems recently discovered consist of larger, more "Jupiter-like" planets revolving at very close distances to their stars. This seems to contradict the precondition to your argument that the 4 inner planets in our system is a common occurance.

[SecularAstronomer]

Thank you for reminding me of that. You are referring to 'hot Jupiters.' They are thought to have "formed farther out and migrated inward via gravitational torques with a massive gas disk (Lin et al., 1996)" (Lin, Bodenheimer, & Richardson, 1996, p. 256).

[SecularAstronomer]

Since "roughly one-third of the giant planets discovered to date outside the Solar System have orbits within 0.5 astronomical units (AU) of their central stars (exoplanets(dot)org)" (Lin, Bodenheimer, & Richardson, 1996, p. 256), then I should note that whatever the likelihood is of terrestrial planets forming is, there may be roughly a 1 in 3 chance that their formation will be disrupted by a hot Jupiter moving in.

[SecularAstronomer]

However, I should also note that "if a giant planet forms and migrates quickly, the planetesimal population has time to re-generate in the lifetime of the disk and terrestrial planets may form (Armitage (2003)" (Lin, Bodenheimer, & Richardson, 1996, p. 256).

[SecularAstronomer]

And in some cases, it seems that "potentially habitable planets with orbits in the habitable zone and substantial water contents can form in such conditions," and that their obliquity "would likely be stable over long timescales (Atobe et al., 2004)" (Lin, Bodenheimer, & Richardson, 1996, p. 262).

[SecularAstronomer]

All in all, my argument is not significantly affected, since, even with the adjustment, we are still dealing with hundreds of billions of stars in our galaxy and tens of sextillions of stars in the observable universe.

[SecularAstronomer]

Raymond, S.N., Quinn, T. & Lunine, J.I. (2005). The formation and habitability of terrestrial planets in the presence of close-in giant planets.  Icarus, 177(1):256-263.

Lin, D.N.C., Bodenheimer, P., Richardson, D.C., 1996. Orbital migration of the planetary companion of 51 Pegasi to its present location. Nature 380, 606--607.

[SecularAstronomer]

Armitage, P.J., 2003. A reduced efficiency of terrestrial planet formation following giant planet migration. Astrophys. J. 582, L47--L50.

Atobe, K., Ida, S., Ito, T., 2004. Obliquity variations of terrestrial planets in habitable zones. Icarus 168, 223--236.

[farvision]

frithwks, generally I agree with you about only attacking the foolishness - I presume you were referring to my use of 'IDiot', but then you used 'cremationists', which is an odd one I haven't heard of...

[hairyreasoner]

It's always been funny to me to hear someone talking about the improbability of an observed event as though pointing out that improbability could somehow make the event un-occur.

[timhansmusic]

Just brilliant, thanks!

[farvision]

Thanks for putting citations into the original literature. This woudl be good to do on most videos, as it completely smashes the creationist ideas

since those IDiots can't manage to publish anything in the peer reviewed literature (unless they cheat).

[Toml420]

Excellently put together and clearly explained - it gave me that warm fuzzy feeling that good science always does.

Subscribed.

[A4AgnstcFndmntlst]

Oh come on what the difference between 18 million miles and a couple feet?

:)

[TheAtheistPaladin]

I like to have agrument please....

[thatgaybloke]

Excellent video. Clearly explained and very easy to understand.

10% probability actually means that within our galaxy (given the hundreds of billions of stars) it would be miraculous if there were NOT planets in the CHZ of at least one G type star.

Experience on Earth shows that if life can exist somewhere, we tend to find it. (We've even found it in places where we've really not expected anything to be able to live at all.)

[Jacnas]

The HZ moves outwards as the sun's energy output steadily increases over time (about 4 bln years ago the sun was about 25% dimmer than it is now). Our planet had pretty much the same surface temperature as it has now because of much greater CO2 and other GHGs density in it's atmosphere. Gradually most of CO2 from atmosphere disappeared due to photosynthesis (interestingly this CO2 is now being released back by us by burning fossil fuels). The earth will become uninhabitable in about 1 bln yrs.

[Hatchyack]

I never got how creationists could take the fine tuning argument seriously. Being surprised that you exist somewhere that is life sustaining is about as dumb as it gets.

[KasparHauser4]

But don't you know?.....people of god or allah know it all.

[corridorofpower]

Nice work.

[BayerLexan]

I just think its absurd that because we only know of the specific needs for us to survive, we only consider comparable environments suitable for life. Bacteria have been found in environments on earth that are instantly fatal to humans, but they are still alive. Oh, some still have such a narrow view, I sometimes wonder if we've ever changed since our divergence with apes.

[SecularAstronomer]

Indeed. And more and more extremophiles are continually being discovered. The idea of a CHZ is likely only one of multiple places where life can form. (life as we know it, anyway) I'm definitely looking forward to the exploration of Europa.