Is there a galactic 'Goldilocks zone'?

[Stonius]

I'm thinking it wouldn't be much fun to be orbiting a star in close proximity to Sagittarius A, the black hole(s) at the center of our galaxy. Apart from dodging superluminal jets and gamma ray outbursts, the density of matter probably means that all those oort cloud objects would get disturbed from their nice stable orbits and pummel the inner solar system (great news for comet watchers! ;-) ).


Which got me thinking - there must be a goldilocks zone within a galaxy where a planet orbiting a star has a better chance at harboring life simply because it has sufficient distance from things that would cause extinction level events.


Has anyone else thought about this? I wonder how close you have to get to the center before the planet becomes 'uninsurable', as it were.


Markus

[xelasnave]

Like so many things there has been some thought about the prospect you raise and I am sure that I know something about it.

I cant recall but I think the main factor was to have a region of older stars which presumably would give greater opportunity to the prospect of metal being available which I expect really means more elements likely to be present in general as well as what would be no doubt the basic metals considered necessary for a intelligent species with technical abilities commensurate with our expectations of how other life should be...ie like us.

The problem is I expect is that we dont know what we should expect...maybe close in is best as more older stars... I do hope we find others out there...the prospect has my mind racing...will they have the same DNA..will they have wars, will they eat young? Etc.
Alex

[ChrisD]

This is a great question.

The question of galactic goldilocks zones is covered in the book Rare Earth:
Rare Earth: Why Complex Life is Uncommon in the Universe (https://www.amazon.com.au/Rare-Earth-Complex-Uncommon-Universe-ebook/dp/B00L60PP0I)
Highly recommended reading.

For complex life its necessary to have (but not limited to) stability and the right chemical elements. The elements are Carbon, Hydrogen, Nitrogen, Oxygen, Sulphur and Phosphorus. All but Hydrogen are produced in stars (phosphorus being the least abundant) So to get the "metallicity" of a planet up, it needs to include the ashes of a few generation of older stars. As you move further out towards the outer edges of a galaxy star formation rate decreases and at some point is too low for these elements to be available.

As you move further in towards the core of the galaxy star density increases and this reduces the environmental stability around the planetary systems formed in these regions. More chances of nasty things happening that can sterilize a planet or eject it from its orbit.

So too far out and you don't get the chemical elements and too far in and you don't get a stable environment. There is your goldilocks zone.

Another thing to think about is the type of star your planet formed around. The goldilocks zone around a star, the orbits where a planet has liquid water on the surface, moves as the star ages. Stars get brighter as they age so the goldilocks zone moves slowly out over the life of a star. We humans took about 4 billion years to evolve so lets accept that to have intelligent life on other planets you need that planet to be in the goldilocks zone for at least 4 billion years continuously. When the earth formed the sun was 30% dimmer than today but fortunately the earth formed on the outer edge of the goldilocks zone around the young sun. As the sun aged the goldilocks zone moved out and we are currently nearing the inner edge of the zone. We'll be outside the goldilocks zone in about 1 billion years. More than enough time for an intelligent species to evolve.

However, if the sun was 10% larger it would increase in brightness as it aged faster and there would be no orbit that stays inside the zone for 4 billion years, so no time for intelligent life to evolve. If the sun was 10% smaller the zone is also smaller and there is still no orbit that stays inside for 4 billion years, so again no time for intelligent life to evolve.

So a planet needs to form in the right zone in the galaxy and in the right orbit around the right sized star for just a chance of intelligent life to exist.

Lucky us.

Chris

[rustigsmed]

https://www.youtube.com/watch?v=v4ogRCjhFDM

[Stonius]

Thanks Chris, that is a great answer!

[xelasnave]

It is difficult to imagine life elsewhere. .. the sheer complexity of life in general and how it has evolved does my head in...just think of DNA and ask is it in effect a mere chemical that will given time turn out that way and therefore has the opportunity of being somewhat common in the Universe or do we have a special version or indeed the only version and other life uses a different mechanism...and mitacondria ..it seems very special and without it we would not be here nor any other animals or vegetation...is it a normal consequence of early life or is it special to us?
Would someone please answer those questions.
Alex

[LonelySpoon]

Not just the goldilocks zone.

Why has only one 'effective' intelligent species evolved on Earth?

I was a big believer in life elsewhere, until a speaker at one NACAA conference made the point the Madagascar and NZ had been isolated long enough, with all the right conditions, for either lemurs or parrots to develop as 'intelligent beings'- much longer than it took us to come about...

I can't come up with reasonable/reasoned arguments against that, which has emptied out my universe considerably.

Sure, intelligent life most likely exists elsewhere, but no fun at all if it's 3 galaxies away and off to the right!

Neville

LSO

[Stonius]

I think it requires intelligence plus the dexterity to make and use tools.

Early humans used fire and hunting to increase the calories in their diets that allowed their brains to grow bigger, making even better tools.

Dolphins, corvids, dogs, etc are not dextrous enough. Octopus don't live long enough and are not social creatures so they can't hand down knowledge.

Markus

[ChrisD]

The right planet orbiting at the right distance around the right star in the right part of the galaxy just buys you a ticket in the "Intelligent Life Lottery". We don't understand why we won, or how many winners there are, or even how the numbers are drawn.

We'll need to get out there and explore to find the answers.

Chris

[ChrisD]

I hope I'm not boring everyone by posting so many times on this subject, but I find this very interesting, so please forgive me. Also thanks Neville, I didn't know the NACAA existed, I did some searching and it sounds like the conferences are fun.

Back to the subject.

Evolution doesn't have a bias towards intelligence. It only selects for variations that allow more success at living long enough to breed.

Humans wondering why more animals don't have large brains is like an elephant wondering why other animals don't have longer noses.

Long noses provide a real survival advantage to elephants as does intelligence for us, but that doesn't necessarily mean they'll work for any other animals.

Chris

[mura_gadi]

*********************************** *****

Two things pop to mind, the first one says a lot imo.

1) We invented beer before we invented the wheel...

2) With fire and tools the mandible jaw muscle could be weaker, allowing the cranium to grow... which was a major step for us in increasing our brain capacity.

Kinda interesting to think that evolution can be affected by the use of tools over time within a species.

[xelasnave]

I am curious to know your authority as my impression is neither have been particularly well established...so..who, where and who says so if you have the time please.

Alex

[mura_gadi]

Ah, now you have me, I was quoting a line from a cooking show recently on tele. I will have to go interwebbing...


Ok, Smithsonian has the following, quick look at times lines, potters wheel 3000/3500bc, fermented grains are 12,000+. About 300 years after the potters wheel we added an axle and got the chariot.

"We tend to think that inventing the wheel was item number two on our to-do list after learning to walk upright. But several significant inventions predated the wheel by thousands of years: sewing needles, woven cloth, rope, basket weaving, boats and even the flute."

Interesting to think it took so long to see the potter's wheel as a horizontal platform and not vertical.

Shows how much technology is speeding up technology, 300 years for potters wheel to chariot and less than 70 years from first powered flight to man on the moon.

[LonelySpoon]

On the subject of 'I read somewhere...'

I read somewhere that there is no evidence that greater intelligence is a survival advantage. The jury is still out.

Given that we are right up against three of the potential survival 'filters'- global war, rampant overpopulation and environmental destruction- the verdict might just be 'nah...'

Lots of species out there, all falling at some hurdle?
Hopefully JWST will find some evidence of life and/or intelligence in the atmospheres of exoplanets- excess O2, CO2, etc.

Hopefully not U238 & friends.

Neville
LSO (currently full of water from leaks)

[LonelySpoon]

:mad2:

On the other hand, 40 years from portable colour TV broadcasting to reality TV shows...

Sorry, I'm feeling negative today because my CRG rocketry flying day has been cancelled due to flooding around Yass.:mad2:

Neville

[mura_gadi]

I was reading yesterday that Burrinjuck was at record release levels.

[xelasnave]

I have taken to refraining from repeating stuff without seeking a solid basis for the claim whatever it may be..like that notion that the daddy long legs is very poisonous..that turns out to be entirely unestablished and yet I blurted it out ...AND I find there are many thing we repeat that are simply incorrect but we heard it liked it and tell it at the pub and parties.

From what I have read both beer and the wheel are credited to the Sumarians ( as are many things).
It is well worth reading the list of what they gave us..

It is terrible the way they are somewhat ignored or played down which I suspect may be due to influence from religion as it was they who invented the flood story, the garden and indeed the God of the bible..and I point out to our good moderators I am not discussing religion but stating history established by clay tablets from the time held in the British Museum.

However it is always prudent to seek new and further information which is why I made my post.

Alex

[xelasnave]

You could think that a very intelligent species would not show any trace of their presence.
Alex

[Peter Ward]

Greg Bear's SF novel Forge of God explores interesting concepts about what aliens
may do if they detect a sentient species elsewhere in the galaxy.

Detection is easy...just look for a series of gamma ray flashes emitted by nuclear testing. Humanity has made hundreds of these.

The end result for the earth and humanity in Bear's book was not good.

That said...humans are currently doing an exceptional job of species extinction and environmental destruction and will bugger up the joint without the need of an alien induced trashing of the planet.

But, getting back to the original post, the evidence of goldilocks zones in nature abounds. From tree lined river banks in deserts to life taking a foothold near hydrothermal vents in the deep ocean. Galactic and solar-system sized variants of this should hardly be a surprise.

[mura_gadi]

[QUOTE=LonelySpoon;1565553]On the subject of 'I read somewhere...'

"I read somewhere that there is no evidence that greater intelligence is a survival advantage. The jury is still out."

I find that a little surprising, with horse crabs surviving 5 extinction periods and birds surviving the last one due a unique ability over intelligence. Not much in the way of intelligent life survives extinction events generally and the species that have are not thought of has having much intelligence.

Crocs have survived one which is amazing for such a large beast... I say you only need the intelligence required to get a feed in your environment.

"Crocodiles and alligators were observed conducting highly organized game drives. For example, crocodiles would swim in a circle around a shoal of fish, gradually making the circle tighter until the fish were forced into a tight "bait ball." Then the crocodiles would take turns cutting across the center of the circle, snatching the fish.

Sometimes animals of different size would take up different roles. Larger alligators would drive a fish from the deeper part of a lake into the shallows, where smaller, more agile alligators would block its escape. In one case, a huge saltwater crocodile scared a pig into running off a trail and into a lagoon where two smaller crocodiles were waiting in ambush -- the circumstances suggested that the three crocodiles had anticipated each other's positions and actions without being able to see each other."

[ChrisD]

Maybe the first message we get from aliens is "Keep quite or THEY will hear you"

[LonelySpoon]

[QUOTE=mura_gadi;1565582]

Surprising that I can read? I've even got books without pictures!

Your comment reinforces the point- our increased 'intelligence' is not necessarily a guarantee of survival, and may in fact be counter-survival.

Neville
LSO

[mura_gadi]

[QUOTE=LonelySpoon;1565673]

My apologies if I offended, just it seemed a silly supposition to entertain when the most basic of creatures have the highest chance of adapting to environmental changes. To acquire intelligence would mean to be a complicated species and have lower survival chances.

Acquiring intelligence would come well after the complexity required for a species for it survival rate not to already be compromised. But since regressive evolution is not a preferred option, maybe intelligence could only be considered essential for survival. It would depend on where you were on the evolutionary ladder.

[LonelySpoon]

Not offended, Steve. Just amused at the way the text read.

[sharkbite]

The notion that humans are more intelligent than other species is a little bit laughable in my view.....

We measure 'intelligence against our own yardstick, and any creature that does not meet our standards we deem dumber than us...

The arrogant hubris of it all!

We are so smart that we have designed myriad ways of removing ourselves from earths future, without any process or way of stopping it.
All this within the last 200 years....

Name one other creature which can do that.....

Yep - real clever.

Even the dinosaurs lasted 250M years and they (allegedly) did not have a brain between them...

<end of rant>

(Prepares for incoming)

[AdamJL]

There's a great book called Blindsight that delves into this topic. And it's street cred is that it's the only Sci-Fi book that quotes academic sources at the back.. and there is a LOT of peer reviewed science quoted.. pages and pages of it. This is hard sci-fi at it's best.

And the basic premise of it, backed up by neuroscience (turn away now if you don't want it spoiled), is that intelligence is held back by consciousness. The potential for super intelligence would require removing this abstract layer that sits on top (our personality). And almost all of the time, your subconscious has already solved a problem, or is in the middle of solving it, or has already sent a message to your body to "perform function X"... but the conscious layer on top interprets this as "I made this choice" when really, it's more like a CEO receiving a report of what's already happened and then assuming they did the work.

[xelasnave]

[QUOTE=AdamJL;1565720]

Before this matter can be discussed one must first define..."intelligence" and indeed "consciousness".......and "abstract layer" needs clarification as does "personality" and care must be taken to exaxtly set out the limitations of "perform function X" and more importantly who was Goldie Locks?

Alex

[Atmos]

Getting back to the original question, yes, there is theoretically a Goldilocks Zone in the Milky Way. A good part of it has to do with supernova which are considered life destroyers for quite a considerable distance. Being in an outer spiral arm has made it a much quieter neighbourhood for the past few billion years. Along with an increased metallicity making a cooler longer burning star.

[Peter Ward]

Rather like living in The Shire..... ;)