[ukmicky (OP)]

originally posted ultima
 The main thing that got me going is that Michael said we share 60% of our genes with a bananna. My questions is this. How many genes does a bananna have in it's genome compared with a human? It's like saying someone who has AIDS shares 100% of their genetics with HIV!!! It's ok to make the comparison with a chimpanzee because we are clearly related to them directly. We can see the history of common ancestors. You get all sorts of statistics saying how much we share with a fly or a cabbage etc. These are worthless; because we share the same codons for a protein that is vital for the survival of all eukaryotic cells doesn't mean we are related in anyway!
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Yes it does


Michael                                      

[Ultima]

http://en.wikipedia.org/wiki/Nanoarchaeum
http://en.wikipedia.org/wiki/Mimivirus

Use the same organic chemistry but they just don't fit. They aren't even related genetically to anything. They share some genes with other organisms but nothing on the scale that directly relates them with anything!
So how do explain things like this keep being discovered?

[ukmicky (OP)]

Their still studying the Mimi virus and yes they do believe it qualifies as life.
However it’s not quite that simple as they also believe the Mimi virus could be a cross between a form of bacteria and a virus rather than being a new branch of life.
The virus mimics bacteria hence its name Mimi and they believe it may be able to do so because it injected its genetic material into the nucleus of a bacteria allowing it to use the bacteria's ribosome RNA. Which is why it is able to create proteins and then replicate.
So rather than creating its own life force. It may have stolen it.
They need to study it further before they can be sure though, so at the moment they still don’t know what it is for sure..



Michael                                      

[Ultima]

A cross between a virus and a bacteria would seriously be a new form of life in my book. It's not like they are remotely similar or related in the first place! I agree that it's still early days...

Define what you mean by Life! damn it! []

[another_someone]

quote:Originally posted by Ultima


Define what you mean by Life! damn it! []

This was the question I asked a while ago.

The first distinction you have to make is between that which is living, and that which is a living organism.  My thumb is living, but few would regard it as an organism in its own right, because it cannot live except while attached to the rest of me.  On the other hand, one could argue that a virus (not including Mimi) cannot live except while attached to another organism.

Ofcourse, you could take this to its logical conclusion, and say that no animal is actually a fully self-sustaining living organism, since all animals depend upon obtaining nutrients from other living entities (e.g. humans need to eat vegetables in order to obtain vitamins that they themselves are not able to synthesise).

But, having made the point that we might regard a small part of a living organism as still being alive, and thus constituting 'life', the question arises as to how small a part of a organism may still be regarded as living?

It is commonly often considered that any part of the body that contains replicating cells may be regarded as living, but until recently it was regarded (and it is still open to debate how true this may or may not be) that mature nerve cells do not replicate - does this mean that the brain is not living tissue?

So, the question still remains, what criteria would you use to define life?

[another_someone]

quote:Originally posted by Ultima

I have a question that might clear things up. I consider Viruses, Prions and Viroids in some form to be "alive" although they can't do everything themselves they are a persistent replicating form, they act on a different scale to cells persisting more through chemical reaction than active involvement with the environment around them.

Do you consider them a form of life?

If so thats instantly one form of life that is very different from a cell. A Prion isn't even genetic! It certainly wouldn't have evolved from a cell or vice-versa. I know any biologist wouldn't agree with me, but hey I can be as deluded as I like []

OK, so going back to the original question, whether there might be life on other planets?  If you were to travel to another planet, and find nothing but viruses (leaving mimi aside), and bearing in mind that viruses on their own are totally inert (i.e. they are not only incapable of reproduction, they are even incapable of any chemical synthesis), would you still say that you have found life on another planet?

[ukmicky (OP)]

WHAT IS LIFE?

I suppose for something to be classed as life has to be able to feed to take in energy,and also has to be able to reproduce

Michael                                      

[another_someone]

quote:Originally posted by ukmicky

WHAT IS LIFE?

I suppose for something to be classed as life has to be able to feed to take in energy,and also has to be able to reproduce

Michael                                      

It is a partial answer.

The concept of feeding and taking in energy is very vague, and would be satisfied by most machines (a motor car would certainly satisfy that requirement - bearing in mind that the concept of feeding is not the same as finding your own food, because many things we consider to be alive do not find there own food, but are opportunistic feeders, waiting for food to come to them).  It must also be bourn in mind that many things we regard as living will only feed in the juvenile phase of their life, and live off their reserves when they are sexually mature.

If one were to consider viruses as living entities, since they are able to reproduce, but only with the assistance of another organism; then one could also regard the motor car as alive, insofar as it is capable of reproducing with the assistance of human beings, but not without that assistance.  This, I think, may be used as another argument for excluding viruses from the category of living things.  If we could create cars that would self-assemble, then the motor car would meet all of your requirements.

What is more interesting is the position of prions, since they do reproduce (given the right environment) without requiring the existence of any other living entity.  It may reasonably be argued that the environment that prions exist in must be created by a living entity, but there are many living organisms that can only live inside other living organisms.

As least as interesting is whether one would consider computer viruses or worms as living.  They have no chemical processes, but your definition of life said nothing about chemistry.  They do consume energy (albeit, not a great deal, but in the days before the Computer Misuse Act, one of the ways of convicting computer hackers was to charge them with theft of electricity), and they do reproduce themselves.

Another candidate for life is the stars themselves.  They are born by the collapse of the interstellar medium, which provides the food upon which they will live.  They then consume vast amounts of energy from the nuclear fusion that this food provides.  When they die, many of them will explode into a super-nova.  The shock waves from the super-nova will create the seeds for new stars to be born, and hence satisfy your requirement for reproduction.  If one accepts that stars themselves are alive, it may well be the simplest answer one could get to whether there is life elsewhere in the universe, albeit, it does not answer your narrower question, whether there is life on other planets.

[ukmicky (OP)]

another_someone


yeah it was partial,i was in a rush had to go to pc world before it closed[]  

ok life as we know it can independently respond to its surroundings,grow and develop, reproduce,  take in energy. and is made up of one or more cells.
which basically rules out all of the above[]

Michael                                      

[another_someone]

quote:Originally posted by ukmicky

another_someone


yeah it was partial,i was in a rush had to go to pc world before it closed[]  

ok life as we know it can independently respond to its surroundings,grow and develop, reproduce,  take in energy. and is made up of one or more cells.
which basically rules out all of the above[]

Michael                                      

I think they key phrase here is 'life as we know it'.

I don't disagree with your other criteria, but I think I could easily apply those, as well as probably most other rational criteria you choose to use to define life, to a myriad of or entities that you would dismiss and not being living.

I think the problem with trying to define life (just as is the problem in trying to define 'intelligence' when one debates issues of 'artificial intelligence'), that the definitions people use are more about trying to prove our uniqueness than about creating a truly rational definition of these terms.

What you are asking is not really 'is there life on other planets', but 'are there things that look and behave like ourselves on other planets' - i.e. something that we can emotionally relate to as life.

http://mars.jpl.nasa.gov/life/index.html

quote:
Finding life isn't exactly easy--scientists aren't even satisfied yet that they have a definition for life that would work for any planet. It's a little easier to define what it means on Earth, but have we fully considered what alien life might be like? What if we were only looking for Earth-like life, and missed the other kinds of life that might be possible?

Personally, I'm not sure we even have an adequate definition of life on this planet.  As I said above, I suspect that our definitions are often more bound up in prejudice than in rational distinctions.  We are often too bound up in proving how special we are, rather than merely accepting that we are just a manifestation of ordinariness.

[neilep]

While you debate about the definition of life, I still maintain that out there, amongst the cosmos is someone  probably unlike myself..and unlike yourself (or even very much like ourselves) who is also debating about life elsewhere in the cosmos.

Men are the same as women.... just inside out !!

[ukmicky (OP)]

I did say in my first post "If you go by earths example"and yes i agree it may be wrong to consider life on earth as the only template but unfortuanatly thats the only evidence of life we have so far.

 


Michael                                      

[another_someone]

quote:Originally posted by neilep

While you debate about the definition of life, I still maintain that out there, amongst the cosmos is someone  probably unlike myself..and unlike yourself (or even very much like ourselves) who is also debating about life elsewhere in the cosmos.

Men are the same as women.... just inside out !!

You are working on the premise that there are many possible opportunities for life to arise.  The question is, even if these opportunities exist, how many different ways are there to fulfil those opportunities?

If there are to be many solutions that are very similar to the solution we have on this planet, it implies that there are very few dissimilar solutions.

Ofcourse, depending upon how you define 'life', one may also ask whether every scenario that will satisfy the opportunity for 'life' would itself be something we would recognise as 'life'.

In order for life to be very similar to our own, it would have to develop on a planet on a planet very similar to Earth.

In the first instance, a planet rich in carbon, hydrogen, nitrogen, oxygen, and iron, is not at all unlikely, since many medium to large super-nova will create these elements.  Having significant supplies of uranium is slightly more unusual, and will only be created by larger super-nova.

The question about the significance of the moon, and the nature of its creation, has been raised.  What is the probability that a moon, created by the same mechanism as our moon, would have happened on one of these relatively rare planets (at about the right distance from the sun, and created from a large super-nova, and with the right sized sun).

Then, if you are looking for life that is sufficiently similar to us to actually be 'also debating about life elsewhere in the cosmos', then one has to ask, how many species on this planet are capable of such a debate?  If you come to the conclusion that only humans can, or could ever have, had such a debate (although one may consider whether dolphins, chimpanzees, or a like, may have such a discussion; but I think the answer is probably 'no'), then you must be looking to the creation of a species that is very rare indeed.  Even on this planet, one has to ask whether, if the death of the dinosaurs came a million years earlier, or a million years later, would humans even have developed on this planet?

[ukmicky (OP)]

So I’m resurrecting a thread that I started 16 years ago ,how time flies.. So apart from this now being the longest running thread in naked scientists history  and maybe the world ,I have a question .


So we have just placed a new lander on Mars with with lots of new equipment in the search for the signs of life from when it had a thick atmosphere and surface water.

A NASA scientist on the telly said if the new rover discovers  that many moons ago (should be Phobos ago:)there was life on Mars that would then mean as both Mars and Earth  either has or had life it must mean that the universe must be teeming with it .

Isn’t that an absurd statement to make . Why would the discovery that there was once life on Mars mean the universe is teeming with life .

[evan_au]

Isn’t that an absurd statement to make

I would say that it is poor statistics - a wild extrapolation from 2 examples.

Knowledge of life on Earth means we know about N=1 example.
- Statistics will tell you that if you have only 1 example, the standard deviation is undefined, so it gives you no clues about the chance of finding life on another planet.

Knowledge about life on Earth and Mars more than doubles the amount of information.
- But you shouldn't assume that 2/2 planets with life means that 100% of Earth-like planets will have life
- For example, statistics assumes that observations are independent. But we know meteorites have traveled between Earth and Mars, so they are not entirely independent.

N=2 is much more information than N=1.
- But N=10 (in different planetary systems) is a far better sample than N=2 in the same planetary system.
- Hopefully, some of the new generation of giant telescopes might give us some clues about atmospheres on distant planets.

[charles1948]

- But we know meteorites have traveled between Earth and Mars, so they are not entirely independent.

That's a good point.  Even if Martian rock-samples showed evidence of life, it might be argued that the life originated on Earth.  And was merely transferred to Mars by ancient meteorites which collided with Earth, and blasted bits of life-bearing Earth rocks to Mars.

[ukmicky (OP)]

Which is the reason why the statement was so absurd especially when it was a NASA scientist who should know better.

[charles1948]

Which is the reason why the statement was so absurd especially when it was a NASA scientist who should know better.

NASA scientists probably do know better.  But they need to enthuse the public.  To get funding for future missions.

[Zer0]

Perhaps this OP was resurrected for the Good...

1) How old is planet Earth?

2) When did Life begin on this planet?

...Anyone?
🤔

[Kryptid]

1) How old is planet Earth?

About 4.54 billion years according to current evidence.

2) When did Life begin on this planet?

The oldest known traces of life are about 3.7 billion years old, but life could have started even earlier.