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Could be over 30 intelligent civilizations in our galaxy.

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#101 russell23

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Posted 19 July 2020 - 05:48 AM

At 5 billion years ago, the timescale which your astrophysicist reference is apparently referring to, the universe was over 8 billion years old.  Considerably more than 3 generations of stars would have gone through their life cycles in that period, since the type of stars that disperse heavy elements through the universe are very short lived.  The production of neutron stars, and opportunities for their mergers, would have been more frequent in the early universe than they are today, so I'm not sure about arguments that it required 8 billion years for certain elements to become abundant enough to support life.  Even in a more pessimistic scenario, there would still be pockets where those elements were more concentrated.

Also, the stars producing the heavy elements and dispersing them have lifetimes measured in millions of years.  



#102 robbieg147

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Posted 19 July 2020 - 06:21 AM

Not all the elements needed for life are created in stars, to make lithium, beryllium and boron you need a black hole.

 

Boron is essential for life.



#103 russell23

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Posted 19 July 2020 - 07:34 AM

Not all the elements needed for life are created in stars, to make lithium, beryllium and boron you need a black hole.

 

Boron is essential for life.

A neutron star or black hole is what is left behind after a star with a lifespan of a few million years goes supernova. 

 

According to the periodic table on this wikipedia page Boron is produced by cosmic rays:

 

https://en.wikipedia...nucleosynthesis

 

Cosmic rays have numerous sources:

 

https://en.wikipedia...wiki/Cosmic_ray



#104 russell23

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Posted 19 July 2020 - 07:45 AM

You're missing the point, you need three generations of stars to burn out. Given that we know how old approx. the universe is and how long it takes each of these generation of stars to burn out we can estimate when conditions existed the earliest for life to begin to form. If I remember correctly from a lecture from an astrophysicist the variable is only ~500mil years before life on earth started. That puts things into perspective. Also don't neglect how special our planet is, not only do you need the right size in the right distance from the right sun, with water on it, an atmosphere and a magnetic field generated by a liquid core, but also having a moon like ours and a tilted planet is believed to have played a major role in the development of life on earth. That's not to say that we are unique but saying there must be life because we discovered already so many exoplanets is only believe, not fact. Just from factoring in all we know that was necesary for our life to kickstart and develop, the assumed large number of possible planets dwindles already, add to that all factors which are not yet discovered and the number gets even smaller.

I think the important thing you are pointing out here is that there are a lot of factors that seem to be very important to the habitability of Earth that may not be abundantly repeated elsewhere. 

 

It would be really helpful if we could answer the most difficult scientific question related to this topic: how did life originate on Earth? 

 

One of the interesting things I've learned reading planetary science research is that giant impacts are common.  The Moon forming impact is thought to have occurred between a Mars sized impactor with the proto-Earth.   What is interesting is that Pluto's satellite Charon is also thought to have formed from giant impact.  Uranus, Mars, Jupiter, Saturn, Neptune, Mercury are all thought to have characteristics that may have been shaped by giant impacts. 

 

The importance of that is the "Rare Earth" concept includes note that the giant impact that formed the Moon may be a rare event that limits the fraction of planets that are habitable if the Moon is in fact a requirement to sustain life on Earth.   However, just in our Solar System there appear to be two satellites formed from giant impacts, so perhaps impact formed moons are not as rare. 

 

Sometimes our new discoveries increase the likelyhood that habitable planets are rare.  Other times the new discoveries increase the likelyhood of habitable planets.


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#105 SupernovaDust

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Posted 19 July 2020 - 08:33 AM

At 5 billion years ago, the timescale which your astrophysicist reference is apparently referring to, the universe was over 8 billion years old.  Considerably more than 3 generations of stars would have gone through their life cycles in that period, since the type of stars that disperse heavy elements through the universe are very short lived.  The production of neutron stars, and opportunities for their mergers, would have been more frequent in the early universe than they are today, so I'm not sure about arguments that it required 8 billion years for certain elements to become abundant enough to support life.  Even in a more pessimistic scenario, there would still be pockets where those elements were more concentrated.

He referenced that because it was then assumed that only suns about the same age as ours can have rocky planets. Thanks to Kepler we know since 2012 that this is not necessarly true because it found rocky planets 11 bill. years old, way outside the galactic habital zone, orbiting an orange dwarf. But just because it is rocky does not mean that it harbors life. The sun also has to be the right sun for life to emerge and be at the right place. It must be isolated enough to not be stripped of it's planets by other passing bodies and close enough to other dead/dying suns to pick up the elements needed for life (which are a lot more than just rocks). A sun which is bombarding it's planets with constant outbursts or varyies in luminance too much will make it very hard for complex life to develop. A sun too low in luminance has it's habital zone too close for a stable climate and weather. Which is why it is most likely that if we find life on a planet in our galaxy it will be on a rocky planet orbiting a sun like ours located in the galactic habital zone. And this means that the sun will most likely have about the same age as ours.

 

Now, does this mean that it is out of the question that life can be orbiting a completely different sun than ours? No. Should we shift the focus of our search for life away from rocky planets orbiting suns like ours within the galactic habital zone? Yes, once we have analyzed all those planets. But if we don't have found life by then it will be even more likely that we are the only ones in our galaxy for now. Time for James Webb to finally get into orbit and answer some questions ;)



#106 SupernovaDust

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Posted 19 July 2020 - 09:07 AM

I think the important thing you are pointing out here is that there are a lot of factors that seem to be very important to the habitability of Earth that may not be abundantly repeated elsewhere. 

....

 

Sometimes our new discoveries increase the likelyhood that habitable planets are rare.  Other times the new discoveries increase the likelyhood of habitable planets.

exactly that. Just reading through the wiki page about the origins of our life is mind bending:

https://en.wikipedia...ry_habitability

 

I think our understanding now is deep enough to say with confidence, that if we discover another Earth with the same attributes as ours there will be complex life, otherwise we most likely have to factor in some outside-influence in the form of a creator of some sorts. For now we have 55 planets found which are "habitable" technically but are not for various reasons. That's not a whole lot given the number of possible suns out there. So yes we need more data to understand if a planet has to be exactly like ours or just similar or nothing like Earth at all. Sadly goverments around the world prefer to invest primarily in military, we could have had much more questions answered if a fraction of the military budged went into science.
 



#107 kel123

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Posted 19 July 2020 - 10:21 AM

Not all the elements needed for life are created in stars, to make lithium, beryllium and boron you need a black hole.


Boron is essential for life.


There is a question I have asked you twice and you have dodged or probably didn't see but reacted to other replies.
You have been dancing around amino acids without saying what you are driving at. So, I will ask the question again.

What is your theory please? At least we are all learning here.

#108 robbieg147

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Posted 19 July 2020 - 11:50 AM

Hi I am not dodging the question at all, I have enjoyed this topic as this is something I have been interested for a long time.

 

I think I said in a previous post that I believe that if life started purely by chance then we could be totally alone in the universe, there may be quite a few places with primitive life bacteria etc. but not intelligent like us.

 

As for religion, anybody believing in God should not see a problem with a completely naturalistic start to life.

 

However I feel we are like ants sitting on a car roof, when serious scientists say we may be living in a computer simulation because life forming by chance is so difficult.

 

My belief is that life cannot start by pure chance, there is something out their beyond our comprehension.



#109 kel123

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Posted 19 July 2020 - 04:56 PM

Hi I am not dodging the question at all, I have enjoyed this topic as this is something I have been interested for a long time.

I think I said in a previous post that I believe that if life started purely by chance then we could be totally alone in the universe, there may be quite a few places with primitive life bacteria etc. but not intelligent like us.

As for religion, anybody believing in God should not see a problem with a completely naturalistic start to life.

However I feel we are like ants sitting on a car roof, when serious scientists say we may be living in a computer simulation because life forming by chance is so difficult.

My belief is that life cannot start by pure chance, there is something out their beyond our comprehension.


I think that's why there is a TOS here because something like this can easily take the thread off topic.

When you start bringing up something beyond our comprehension, you have entered into a realm of what this thread, forum or CN is not about.
We are discussing science and scientific formulas and equations here, not religion or superstition.

We as members all have our religions and private beliefs but we try to keep them from coloring our dicussions here. I implore you to do the same and leave out your beliefs .

Just to be clear, your argument doesn't hold any water from the beginning and it is definitely not standing on any solid ground. Disputing whether life started by chance or not has nothing to add to the discussion because it was all about an equation.

Even if life started by chance here, what stops it from starting by chance somewhere else in a vast universe. Again, even if there is "something beyond our comprehension " , how did that thing originate? If we are living in a computer simulation? How did the computer and simulator originate?

You see why science works empirically?

But unfortunately, science can be hard to understand. That's why there are experts and people spend a lot of time and money for education.
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#110 cuzimthedad

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Posted 19 July 2020 - 06:40 PM

Okay folks, let's get back on track. Even talking religion in a round about way is still talking religion.


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#111 Andrew_L

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Posted 25 July 2020 - 05:02 AM

Isn’t the great attribute of science how it deals with uncertainty? First off it accepts it, unlike a lot of other areas of human activity - the proponents of which claim certainty, often where there is none.  Secondly it embraces it, relishes it even, because areas of uncertainty are where new generations of scientists can make a contribution. 
 

The first steps in seeking new knowledge are to define what is known and what is unknown, what we need to find out, and how we might go about achieving it. That is what the Drake equation seeks to do. It’s a sort of aid to thinking about the problem.  
 

I think the general public misunderstand the subtleties of science in this respect. They think it’s about certain knowledge and absolutes.  Scientists themselves are perhaps guilty in some respects of contributing to that misunderstanding. They often appear to be stating things as fact when they are really only speculating or hypothesising. I also suspect part of the problem is the translation of scientific research by the popular media. 



#112 Gschnettler

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Posted 01 August 2020 - 06:28 AM

The time element really gets me thinking. If aliens had visited Earth a billion years ago they would have only found plants and animals. If they came a billion years in the future they might find the successors to Homo sapiens. Even plus or minus 10 million years from now would be a huge range (for us, but not in the grand scheme of things) during which any visitors to Earth probably wouldn’t find Homo sapiens (I’m not convinced that we’re going to make it that long).

The distance is a huge factor too. Even if there were a perfect counterpart civilization somewhere in the Andromeda galaxy right now, we couldn’t even talk to them much less visit them given the 2.5 million light year distance.


So what intrigues me is that it’s not enough to have another solar system that has just the right conditions for life to develop and flourish. Even if that is overwhelming successful in many places there are still massive time and distance factors to overcome.

Gary

#113 lee14

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Posted 01 August 2020 - 07:02 AM

If aliens had visited Earth a billion years ago they would have only found plants and animals. If they came a billion years in the future they might find the successors to Homo sapiens. Even plus or minus 10 million years from now would be a huge range (for us, but not in the grand scheme of things) during which any visitors to Earth probably wouldn’t find Homo sapiens (I’m not convinced that we’re going to make it that long).
 

 

 

If they came a billion years ago, the only life to be found were single cell organisms.

 

You're right, time is very important. That's why the Drake equation includes a factor denoting the length of time a technological civilization exists.

 

Lee
 



#114 russell23

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Posted 01 August 2020 - 08:22 AM

The time element really gets me thinking. If aliens had visited Earth a billion years ago they would have only found plants and animals. If they came a billion years in the future they might find the successors to Homo sapiens. Even plus or minus 10 million years from now would be a huge range (for us, but not in the grand scheme of things) during which any visitors to Earth probably wouldn’t find Homo sapiens (I’m not convinced that we’re going to make it that long).

The distance is a huge factor too. Even if there were a perfect counterpart civilization somewhere in the Andromeda galaxy right now, we couldn’t even talk to them much less visit them given the 2.5 million light year distance.


So what intrigues me is that it’s not enough to have another solar system that has just the right conditions for life to develop and flourish. Even if that is overwhelming successful in many places there are still massive time and distance factors to overcome.

Gary

Just to clarify, a billion years ago they would not have found plants and animals.  They would have found single celled organisms and some symbiotic colonies.  Nothing on land.  

 

But your point is taken.  For most of the Earth's history, as far as we know, there were no species capable of communicating with other species in different star systems.   Even now our ability to communicate is very limited.  We just have the knowledge that there are methods of possibly identifying signals from other systems and that, if present, other species could pick up on our signals.



#115 russell23

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Posted 01 August 2020 - 08:26 AM

I forget who it was that argued that "we are alone" on the basis that even if other civilizations have arisen in the history of our galaxy, the odds that they are still around and nearby at this time is extremely remote.   So even if they are "out there" we are effectively still alone. 

 

But or course what a world altering discovery it would be if the existence of another civilization was proven even if communication or visitation is impossible. 



#116 Andrew_L

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Posted 02 August 2020 - 01:31 PM

It’s debatable whether contact would be a good thing though. 



#117 Matt L

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Posted Yesterday, 05:40 PM

Lots of food for thought in this thread. I like the original article's 'solid estimate' of thirty civilizations in our galaxy. 

But if we are alone and it is just us,at one civilization per galaxy, we could be far from alone in the universe.

At one civilization per galaxy the disk of the moon would cover 480,000 civilizations.

100b galaxies/ 41,000 sq. degrees =2.4m galaxies per sq. degree

Moon =.2 sq. degrees = 480,000 civilizations behind the moon

Seems outlandish.

Please feel free to check the math.... 

 

41,000 sq.degrees on the surface of a sphere

100 billion galaxies

 I like viewing the moon...

 Some really big ears should pick up something you'd think....




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