The Goldilocks zone???

Bohrio

maninasia wrote: »

Well according to this picture neither Mars nor Venus is even in the habitable zone. It seems that there is no consensus whatsoever on this issue. If they simply said we are looking for an identical twin of Earth and called it the 'Identical Zone' they might be on to something . But they'd probably miss all the aliens laughing at them on the moon next door.:)

16 Cygni Bb (discovered in 1996) is a large gas giant with an eccentric orbit, found to spend some of its time inside the habitable zone. However the orbit means it would experience extreme seasonal effects. Despite this, simulations suggest an Earth-like moon would be able to support liquid water at its surface over the course of a year.[42]

Gliese 876 b (discovered in 1998) and Gliese 876 c (discovered in 2001) are both gas giants discovered in the habitable zone around Gliese 876. Although thought not to be watery, both may have habitable moons.[43]

This is an excerpt from the Habitable Zone page on wiki... So it does mention moons...

Oh and you do realise that nobody here has disputed the fact that we all believe that there could be life outside the habitable zone (as the theory clearly states) and that we should be putting more effort into searching for life in other planets and moons... we know that, we have known that for many years now

It just looks like the following happened to you,

Sometime ago (probably over 2 years ago) you came across an article where it was written that there could be a subsurface ocean underneath a thick crust of ice in one of the moons of jupiter, and if so, there is a possibility that this ocean could support life (as we know life can survive under really harsh circumstances), probably microbial life, next thing you did is say, but the habitable zone says that life cannot exist ouside this zone! (which is doesnt actually!!!!! ) So the habitable zone theory is wrong as it is very clear that life exists outside this zone (although we havent found any life yet, hopefully we will soon). and then started posting your comments.

and thats it! we are going over and over this ever since!

maninasia

Bohrio wrote: »

maninasia wrote: »

Well according to this picture neither Mars nor Venus is even in the habitable zone. It seems that there is no consensus whatsoever on this issue. If they simply said we are looking for an identical twin of Earth and called it the 'Identical Zone' they might be on to something . But they'd probably miss all the aliens laughing at them on the moon next door.:)

16 Cygni Bb (discovered in 1996) is a large gas giant with an eccentric orbit, found to spend some of its time inside the habitable zone. However the orbit means it would experience extreme seasonal effects. Despite this, simulations suggest an Earth-like moon would be able to support liquid water at its surface over the course of a year.[42]

Gliese 876 b (discovered in 1998) and Gliese 876 c (discovered in 2001) are both gas giants discovered in the habitable zone around Gliese 876. Although thought not to be watery, both may have habitable moons.[43]

This is an excerpt from the Habitable Zone page on wiki... So it does mention moons...

Oh and you do realise that nobody here has disputed the fact that we all believe that there could be life outside the habitable zone (as the theory clearly states) and that we should be putting more effort into searching for life in other planets and moons... we know that, we have known that for many years now

It just looks like the following happened to you,

Sometime ago (probably over 2 years ago) you came across an article where it was written that there could be a subsurface ocean underneath a thick crust of ice in one of the moons of jupiter, and if so, there is a possibility that this ocean could support life (as we know life can survive under really harsh circumstances), probably microbial life, next thing you did is say, but the habitable zone says that life cannot exist ouside this zone! (which is doesnt actually!!!!! ) So the habitable zone theory is wrong as it is very clear that life exists outside this zone (although we havent found any life yet, hopefully we will soon). and then started posting your comments.

and thats it! we are going over and over this ever since!

And you keep relating your accusations and change your tune (plenty of posters said moons were not included in this concept) next you will be saying there is no need for liquid surface water to be considered a 'habitable zone', where will we all be then .

Since this thread was started the Wiki page definition for habitable zone has been updated to finally include moons, which vindicates my assertion that the concept is constantly shifting and not a solid theory and depends more on peoples own prejudices than scientific reasoning.

Also? How come Mars isn't in the habitable zone in that picture? I can tell you why, because someday made some arbitrary decisions not to include it. The fact is nobody knows exactly why Venus has a runaway greenhouse effect, Earth didn't, and Mars has no currently existing ocean.
The requirement for liquid surface water is a joke.

BOF666

I give up...

Bohrio

maninasia wrote: »

And you keep relating your accusations and change your tune (plenty of posters said moons where not included in this concept) next you will be saying there is no need for liquid surface water to be considered a 'habitable zone', where will we all be then .

Thats because you are confusing planet habitability with circumstellar habitable zone. When moons were brought into this conversation a year ago, people were saying that there under certain circumstances, there could be liquid water on the surface of a moon (and life) outside the habitable zone (which still doesnt matter as the habitable zone theory doesnt exclude life outside this zone)

The location of planets and natural satellites (moons) within its parent star's habitable zone (and a near circular orbit) is but one of many criteria for planetary habitability and it is theoretically possible for habitable planets to exist outside the habitable zone

Earth did go through a similar process to Venus while it was forming. You see, you are still going back to if a planet is inside the habitable zone it MUST have liquid water on the surface blah blah blah...

Nevertheless, I read this sometime ago

Owing to its extremely hostile conditions, a surface colony on Venus is out of the question with current technology. However, the atmospheric pressure and temperature approximately fifty kilometres above the surface are similar to those at the Earth's surface and Earth air (nitrogen and oxygen) would be a lifting gas in the Venusian atmosphere of mostly carbon dioxide. This has led to proposals for extensive "floating cities" in the Venusian atmosphere. Aerostats (lighter-than-air balloons) could be used for initial exploration and ultimately for permanent settlements. Among the many engineering challenges are the dangerous amounts of sulfuric acid at these heights.

But this will mean going of topic.

Anyway I am gonna stop now as I know are gonna reply saying exactly the same thing about life outside the habitable zone etc..

maninasia

Bohrio wrote: »

Thats because you are confusing planet habitability with circumstellar habitable zone. When moons were brought into this conversation a year ago, people were saying that there under certain circumstances, there could be liquid water on the surface of a moon (and life) outside the habitable zone (which still doesnt matter as the habitable zone theory doesnt exclude life outside this zone)

The location of planets and natural satellites (moons) within its parent star's habitable zone (and a near circular orbit) is but one of many criteria for planetary habitability and it is theoretically possible for habitable planets to exist outside the habitable zone

Earth did go through a similar process to Venus while it was forming. You see, you are still going back to if a planet is inside the habitable zone it MUST have liquid water on the surface blah blah blah...

Nevertheless, I read this sometime ago

Owing to its extremely hostile conditions, a surface colony on Venus is out of the question with current technology. However, the atmospheric pressure and temperature approximately fifty kilometres above the surface are similar to those at the Earth's surface and Earth air (nitrogen and oxygen) would be a lifting gas in the Venusian atmosphere of mostly carbon dioxide. This has led to proposals for extensive "floating cities" in the Venusian atmosphere. Aerostats (lighter-than-air balloons) could be used for initial exploration and ultimately for permanent settlements. Among the many engineering challenges are the dangerous amounts of sulfuric acid at these heights.

But this will mean going of topic.

Anyway I am gonna stop now as I know are gonna reply saying exactly the same thing about life outside the habitable zone etc..

I know we are all getting tired of this debate now, but I never stated the below.

Earth did go through a similar process to Venus while it was forming. You see, you are still going back to if a planet is inside the habitable zone it MUST have liquid water on the surface blah blah blah

What I was pointing out was both that the picture appended above does not include Mars or Venus in the habitable zone (which goes to show there seems to be a massive amount of divergence in what exactly this concept means) and the fact that Mars and Venus are in the habitable zone but do not have liquid water as compared to some of the moons in our solar system. Which makes a joke of the whole habitable zone concept if the key point is that large bodies of liquid water are sustained! Only one of the 3 rocky planets supposedly within the 'habitable zone' or 'Goldilocks zone' has sustained bodies of liquid water, therefore other important processes are likely to come into play as I have stated already (gravity/plate tectonics/chemistry/greenhouse feedback effects and biological feedback effects)

From the example of our own solar system the 'habitable zone' is not some type of simplistic idea of limited radial band from the Sun, rather the habitable zone is likely to be distributed widely throughout the solar system (our solar system has 168 moons, 20X the number of planets, at least three of which have proven to have liquid water, 3 moons and only 1 planet) according to local conditions. There are only 3 confirmed other locations in our solar system that have large bodies of liquid water, so surely the concept of habitable/goldilocks zone should be weighted to them and their location around the gas giants.

Personally I believe that microbial life and other types of life exist far beyond these narrow parameters above.

Bohrio

maninasia wrote: »

From the example of our own solar system the 'habitable zone' is not some type of simplistic idea of limited radial band from the Sun, rather the habitable zone is likely to be distributed widely throughout the solar system (our solar system has 168 moons, 20X the number of planets, at least three of which have proven to have liquid water, 3 moons and only 1 planet) according to local conditions. There are only 3 confirmed other locations in our solar system that have large bodies of liquid water, so surely the concept of habitable/goldilocks zone should be weighted to them and their location around the gas giants.

Personally I believe that microbial life and other types of life exist far beyond these narrow parameters above.

So what you want is for the concept of habitable zone to include moons and every single object around a planet and of course planets, and also the oort cloud etc... so basically everything should be called habitable zone? wow

And you are still confusing liquid water on the surface with under the surface... sesame street failed me here...

Please so us where the habitable zone theory says life cannot exist beyond this zone, and even liquid water ON the surface.

You are confusing things and quite frankly I know you are doing it on purpose so, so long man!

maninasia

What I'm trying to do is to tease apart the logic behind the definition of the 'habitable zone'. When I look at it I don't see anything beyond some arbitrarily chosen parameters, which can shift according to an individual's perception and the current 'acceptance level' in the field.

The requirement for liquid water at the surface is one of those poorly chosen and unnecessarily restrictive parameters.

Now we can see moons coming very much into play in terms of the ability to sustain Earth like life, whereas before the focus would have been much more on nearby rocky planets.

It's been interesting to have this debate to look at the theories from different angles. The usage of terms such as 'habitable zone' and 'goldilocks zone' actually confuse the general public.

BOF666

maninasia wrote: »

What I'm trying to do is to tease apart the logic behind the definition of the 'habitable zone'. When I look at it I don't see anything beyond some arbitrarily chosen parameters, which can shift according to an individual's perception and the current 'acceptance level' in the field.

The requirement for liquid water at the surface is one of those poorly chosen and unnecessarily restrictive parameters.

Now we can see moons coming very much into play in terms of the ability to sustain Earth like life, whereas before the focus would have been much more on nearby rocky planets.

It's been interesting to have this debate to look at the theories from different angles. The usage of terms such as 'habitable zone' and 'goldilocks zone' actually confuse the general public.

It's a zone that the planet Earth could live in. That's as simple as it can be put. If the Earth moved to a different star, it's the area around that star that the Earth would do best in.

There's no requirements (like water on the surface or sustaining life) and moons, planets, aliens, etc. don't come into it. It's literally just an area of space around a star. That's all a habitable zone is. A big area around a star.

The only person that seems to be getting confused by the terms "habitable zone" is you, I really hope this has helped you.

maninasia

I'd suggest you read the thread BOF, the habitable zone has many different meanings and it's meaning has been changing aswell, seems moons are fine right now .

I was trying to be nice to you earlier even if you were going on about 'carbon based life forms' (you watch star trek too?) and reposting pictures from the first page (good research that) that didn't even support your case and completely contradicted your new found mate Bohrio...arrgghh!

Capt'n Midnight

what about Gaia ?

The principle that if life is anywhere on a planet it probably has evolved to be nearly everywhere.

Yes here on earth life is associated with liquid water

Bohrio

maninasia wrote: »

The requirement for liquid water at the surface is one of those poorly chosen and unnecessarily restrictive parameters.

Restrictve for what? There is no restriction! Please clarify this

and also, I am still waiting for you to point out where the habitable zone theory says it is not possible for liquid water to exist either under the surface or on the surface of a planet/moon outside this "area", and also, where it says that life cannot exists (either microbial or any type) outside this area.

How come you never answer any questons?

This is your definition of Habitable Zone

manimasia wrote:

...habitable zone means the zone that life could inhabit and then that means they mean areas that need liquid water on a planet but not only that it means the distance from the sun within a rather narrow range, when much of Earth life(i.e. bacteria/archaea) could survive off Earth outside the supposed habitable zone..basically the idea behind it is incorrect if you understand anything about microbes or evolution or the history of the Earth

Definition of Habitable Zone

In astronomy and astrobiology, habitable zone (more accurately, circumstellar habitable zone or CHZ) is the scientific term for the region around a star within which it is theoretically possible for a planet with sufficient atmospheric pressure to maintain liquid water on its surface.

No mention about microbies, bacterias, etc...

Do you see the difference?

You keep thinking that the habitable zone is the only place where life and liquid water can exists... when, as you have been told SEVERAL times it isnt, it is just an area in space, thats all... but you just wont listen, I seriously dont get it

Lets use an analogy

So lets pretend I am a scientist and I start taking measures on the southern hemisphere, I soon realize that the further south I go the colder it gets. This makes sense to me because I few years ago I did the same study on the north pole and discover that the further north I go the colder it gets (lets just pretend this is 100% true). So I am safe to assume that it is very likely it will be the same in the southern hemisphere. But I dont want to go all the way to the south pole so what I do is keep measuring until I reach certain temperature. But instead of going further south I draw a circumference and call the area inside that circumference Antartica Zone (which is aka Antartica), this Antartica Zone is nothing more than an Area within our globe, same as Europe, Greenland, etc...

So, lets us use the Antartica Zone as an analogy to the Habitable Zone and lets use sub cero temperatures as an analogy to the liquid water on the surface.

So lets say I postulate a theory where I say that in the Antartica Zone it is theoretically possible for temperatures to go below 0 degress.

Then, in adition to this I could start thinking, well, I know that water freezes under sub cero temperatures forming ice, I have also notice that this happened in the north pole, so, therefore, there is a posibility that there is also ice in this Antartica zone (this could be the analogy of life and liquid water).

In conclusion all I am saying is that, based on what I have seen in the north pole, I have the feeling that The Antartica Zone is cold.

What I am not saying:

- Sub cero temperatures will only happen in the Antartica zone nor
- Ice can only exist inside the Antartica Zone

So this is the Habitable Zone in this example




Your view: that is incorrect, temperatures can also drop below 0 in other places such as europe, Africa, America, Asia among others, and also that ice can be found on many other places such as your fridge and ice cold beer... and then you say that we should change the definition of Antartica to include Also the north pole, alps, himalayas, andes and any other part in the world that contain ice and temperatures below 0.

So for you, this is how antartica should look like



If you dont get it you have to be trolling...

DubOnHoliday

http://news.discovery.com/space/habitable-exoplanet-gliese-163c-life-120920.html

maninasia

I'm not trolling, I I appreciate you took the time to lay out the case above. I just really REALLY don't like the terminology. Habitable zone is very misleading, and I think you can see that too. In fact it could be the most misleading name for something that I have yet to come across. We can see how so so many journalists get it wrong when they state glib facts as per the below, quoted from the article above. Most of the general public reading the quote below will make an assumption that outside of this distance liquid water will not exist and that areas outside of the zone are not habitable. In fact the mistake is repeated again in the linked article to the term 'habitable zone' and it is an unforgivable mistake to make for a writer who is writing in a so-called scientific publication.

The newfound world, a "super Earth" called Gliese 163c, lies at the edge of its star's habitable zone -- that just-right range of distances where liquid water could exist.

Yes the circumstellar habitable zone is something that is clearer than the usual lazy habitable zone terminology, but even then this is not very clear..'circumstellar habitable zone for life that absolutely requires large bodies of liquid water'. Of course it may not habitable at all due to the influence of a whole host of other factors, not least the influence of plate tectonics (Mars had active plate tectonics, then it shut down).


So what they should say is it is the 'circumstellar zone of possible maintenance of large liquid water bodies'. Let's just leave out the habitable completely!


The REAL habitable zone of course in a solar system, following the latest scientific theory and data, would be distributed widely through the solar system, with SOME concentration in the circumstellar liquid water zone and SOME concentration on moons around gas giants along with unknowns. The problem is the unknowns are pretty damn big still.

Let's have a look at this great map I found that shows the distribution of water in the Solar System.



Therefore, to use a similar analogy to the one you have just used, if I was to take your map of the globe and had come to Earth to look for life, as an example I would mark out in red the areas to concentrate on, including the equator (perhaps similar to the CHZ above), the oceans, and of course areas that are emitting large amounts of heat and light like cities.

Bohrio

maninasia wrote: »

circumstellar habitable zone for life that absolutely requires large bodies of liquid water'.

I am not sure if that is a citation but if those are your own words please tell me where you read that, oh wait, dont bother, if you havent replied to any questions other people has asked you why would you reply to mine so....I am sorry but I have to stop replying to your posts. I can't believe you are still talking about life and water.

You would expect people not familiar with astronomiy or the theory itself to get confused with the term habitable zone (as it includes the word habitable people might incorrectly think it means is the place where people can live in, when, in reality, this is not what it means, although, as a side note, so far is the only place "habitable" to us in our solar system but that's not the point)

Let's just call the habitable zone the universe from now on and leave it like this. I dont know anymore whether you are getting what it is or if it is just that you dont like tha name, if the name is the problem just call it Bob, the Bob zone... Not sure why you are still talking about the habitable zone as if it is some sort of barrier where outside it, life and water (of any state) cannot exist.

lets just agree to... well I dont even know to what!

I just find it hard to believe that after all this time (couple of years I believe) you still dont get what the habitable zone theory is all about... and you still go on about water in other planets, etc... sorry

Slán!

maninasia

Slan leat.

maninasia

He's back! And with another tidbit of very interesting news.

http://www.bbc.co.uk/news/science-environment-20501574

The discovery of microbes thriving in the salty, sub-zero conditions of an Antarctic lake could raise the prospects for life on the Solar System's icy moons. Researchers found a diverse community of bugs living in the lake's dark environment, at temperatures of -13C.
Furthermore, they say the lake's life forms have been sealed off from the outside world for some 2,800 years.
Details of the work have been outlined in the journal PNAS.
Lake Vida, the largest of several unique lakes found in the McMurdo Dry Valleys, contains no oxygen, is acidic, mostly frozen and possesses the highest nitrous oxide levels of any natural water body on Earth.
A briny liquid that is approximately six times saltier than seawater percolates throughout the icy environment.

The abundance of different chemical compounds present in the lake led the researchers to conclude that chemical reactions were taking place between the brine and the underlying iron-rich sediments, producing the nitrous oxide and molecular hydrogen.

The hydrogen, in part, may provide the energy needed to support the brine's diverse microbial life. In addition, the slow rate of metabolism of these microbes prevents the energy reserves from being quickly depleted.

"It's plausible that a life-supporting energy source exists solely from the chemical reaction between anoxic salt water and the rock," said co-author Dr Christian Fritsen, also from the DRI.

If this is indeed the case, said Dr Murray, it provides "an entirely new framework for thinking of how life can be supported in cryo-ecosystems on Earth and in other icy worlds of the Universe".

Jupiter's icy moon Europa represents one such target.

Dr Ellis-Evans commented: "If you go to somewhere like Europa, this sort of finding is really of interest. You can apply this more or less directly.

maninasia

Another moon, Dione, pops up with possible subsurface ocean.

http://www.nasa.gov/mission_pages/cassini/whycassini/cassini20130529.html

Scientists are still trying to figure out why Enceladus became so active while Dione just seems to have sputtered along. Perhaps the tidal forces were stronger on Enceladus, or maybe the larger fraction of rock in the core of Enceladus provided more radioactive heating from heavy elements. In any case, liquid subsurface oceans seem to be common on these once-boring icy satellites, fueling the hope that other icy worlds soon to be explored – like the dwarf planets Ceres and Pluto – could have oceans underneath their crusts. NASA's Dawn and New Horizons missions reach those dwarf planets in 2015.

maninasia

http://www.newscientist.com/article/dn25379-squirting-moons-face-off-in-race-to-find-alien-life.html#.U0VH6fmSzg8

Although the article is interesting, it again jumps to conclusions by just mentioning two candidates in the solar system for life beyond Earth. There are many other candidate moons and planets as well..although these are current front runners for life that would be SIMILAR to Earth.

For instance Titan has vast hydrocarbon lakes and complex organic molecules. Why would microbes not like to chew up some of that hydrocarbon?
http://www.bbc.com/news/science-environment-25360516

maninasia

NASA have been listening, the 'New Goldilocks Zone'.

As I said earlier in the thread about the 'Old Goldilocks Zone'

It's a dodgy theory lads

:pac:

More detailed seminar....

http://www.jpl.nasa.gov/events/lectures_archive.php?month=6

Capt'n Midnight

The Goldilocks zone is for water

for ammonia , hycrocarbons , Ammonium hydrosulfide

or Iron Carbonyl

it could be different

Bohrio

Manimasia, could you please write down your definition of the goldilocks zone (or habitable zone) please... I am just curious

obriendj

I was just thinking about the Goldilocks zone today. but putting a different spin* on it.

As discussed in the new goldilocks zone video, there could be life out there. but I believe that for mammals / primate / intelligent life to exist the planet must be in the original Goldilocks zone. The mean temperature of the planet must be similar to ours.

However I was thinking, if there was a planet like that out there but with a small difference.

Is our planet spinning at the perfect speed to allow a day to be 24 hours. Do you think a shorter or longer day would have an effect on the life of a planet.

Is the axis tilt of 23 degrees just right to get the perfect seasons? Would life on a planet suffer if the angle of tilt was greater / less? Greater would imply harsher winters and hotter summers. while less tilt would imply no seasons with constant temperature.

I would guess that life forms such as bacteria and insects would still exist and still evolve but i am not sure if mammals or reptiles would would have developed as well as we have here.

Or do you think regardless of these factors, once the planet is in the goldilocks zone, it probably will have large land dwelling mammals.

*excuse the pun

Capt'n Midnight

obriendj wrote: »

Is our planet spinning at the perfect speed to allow a day to be 24 hours. Do you think a shorter or longer day would have an effect on the life of a planet.

Heat can be transferred via a planets atmosphere. Even if a planet is in a locked orbit with one side facing the sun and the other in total darkness atmospheric convection cells will average out the temperature somewhat.

Long ago our planet rotated every 6 hours. Insane tides. Also the moon was a lot closer so more solar eclipses and no lunar ones.

One way we know this is from "growth rings" on stramatolites

Bohrio

Capt'n Midnight wrote: »

Heat can be transferred via a planets atmosphere. Even if a planet is in a locked orbit with one side facing the sun and the other in total darkness atmospheric convection cells will average out the temperature somewhat.

Long ago our planet rotated every 6 hours. Insane tides. Also the moon was a lot closer so more solar eclipses and no lunar ones.

One way we know this is from "growth rings" on stramatolites

I think that the main problem is that, for complex life to evolve conditions have to be just right.

I am confident we will find life outside our planet soon enough, jupiter and saturn moons being perfect candidates, however, finding complex organisms in our solar will be very unlikely.

Earth have just the right conditions for life "as we know it". Meaning that the reason why our planet is titled 23 degrees is because we have the moon (among other things), without it, life on earth would be much more difficult.

However, this makes reference to, as I said, life "as we know it", there could be other types of complex life out there that could thrive under different conditions and we just cannot comprehend.

But most of these scientist are not hoping to find any type of complex life underneath an ice crust, they will settle for microbes or unicellular creatures.

Look at the blood waterfalls in antartica, microbes trapped for millions of years without oxygen, light, etc. They just live under a 400 meters tick ice crust, so, if they survived under this conditions why wouldnt they survive under a several km ice crust in Europa?

I think life is much more abundant in space than we think, however, humanlike complex lifeforms will be very very rare, and IMO probably non existent in our solar system.

But this has nothing to do with the goldilocks zone theory though

obriendj

Bohrio wrote: »

I think that the main problem is that, for complex life to evolve conditions have to be just right.

I am confident we will find life outside our planet soon enough, jupiter and saturn moons being perfect candidates, however, finding complex organisms in our solar will be very unlikely.

Earth have just the right conditions for life "as we know it". Meaning that the reason why our planet is titled 23 degrees is because we have the moon (among other things), without it, life on earth would be much more difficult.

However, this makes reference to, as I said, life "as we know it", there could be other types of complex life out there that could thrive under different conditions and we just cannot comprehend.

But most of these scientist are not hoping to find any type of complex life underneath an ice crust, they will settle for microbes or unicellular creatures.

Look at the blood waterfalls in antartica, microbes trapped for millions of years without oxygen, light, etc. They just live under a 400 meters tick ice crust, so, if they survived under this conditions why wouldnt they survive under a several km ice crust in Europa?

I think life is much more abundant in space than we think, however, humanlike complex lifeforms will be very very rare, and IMO probably non existent in our solar system.

But this has nothing to do with the goldilocks zone theory though

I would agree with that and while it would be great to discover life in the ice of Europa, its highly unlikely that any complex life will ever be found.

maninasia

Jeezus lads, pick up Darwin's origin of species and have a read.

There's a few things in the ocean swimming around, ye can get started on fish for a start.

And yes, our ancestors were fish.

I mean we've only known this for a 150 years or so.

http://en.wikipedia.org/wiki/Timeline_of_human_evolution#mediaviewer/File:Age-of-Man-wiki.jpg

Zubeneschamali

Simple cells appeared on Earth within a billion years of its formation, but it was another two billion years before they evolved nuclei. Another billion years, and there were bacteria.

So after 3-4 billion years of life on Earth, the most complex lifeforms were bacteria. Everything more complex evolved in the 1 billion years since. Why?

We don't know. But it is clear that multicellular life is a big leap, or it could have appeared billions of years earlier.

Maybe that leap is really fantastically unlikely and single cell life is relatively common, but more complex forms are vanishingly rare.

maninasia

Or maybe it's not, our sample of one so far isn't a whole lot to go on. BTW, microbial life could have evolved from multi-cellular life. Get your head around that one (evolution isn't a uni-directional arrow, it doesn't have a purpose). Also the definition of complex life might be a bit hard to pin down.

Also, comets are now proven to hold organic molecules, no reason why life wasn't seeded around the galaxy or transported from place to place.

mickmackey1

There's a huge difference between organic molecules and life, and no evidence whatsoever that comets played any role.

Zubeneschamali

maninasia wrote: »

no reason why life wasn't seeded around the galaxy or transported from place to place.

I wouldn't be a bit surprised. For life to evolve from nothing to single cells inside a billion years, and then, in the next billion years, do nothing, and then another billion years later evolve the nucleus, and another billion before they evolve into anything multicelllular.

That first step looks suspiciously fast.