QuoteThanks to the hardworking Gaia spacecraft, astronomers think they’ve located a star that formed from the same solar nebula as the Sun. In fact, this star is a virtual twin of the Sun and it’s actually pretty close. Well, astronomical speaking.
https://www.youtube.com/watch?v=XqzDdy26Oqw
https://en.wikipedia.org/wiki/HD_186302
And a mere 184 light years away.
Yeah, it's right next door - let's go!
Quote from: Hydra009 on December 04, 2018, 08:06:29 PM
And a mere 184 light years away.
If it proves to be an actual solar sibling and not just a star with similar chemistry, I should think the fact that we find it that nearby would suggest our sun was born of a large nebula. Alternately, maybe we shouldn't be surprised to find one nearby even 4.5 billion years later, simply because as a simple matter of all starting from the same place with broadly similar vectors, the sun and its siblings shouldn't have strayed all that far from each other.
Is there an astrophysicist in the audience?
Quote from: trdsf on December 04, 2018, 08:31:48 PM
If it proves to be an actual solar sibling and not just a star with similar chemistry, I should think the fact that we find it that nearby would suggest our sun was born of a large nebula. Alternately, maybe we shouldn't be surprised to find one nearby even 4.5 billion years later, simply because as a simple matter of all starting from the same place with broadly similar vectors, the sun and its siblings shouldn't have strayed all that far from each other.
Is there an astrophysicist in the audience?
Just a layman here. But this article (http://astrobob.areavoices.com/2018/11/24/did-astronomers-just-find-the-suns-sister/) says that both suns (stars?) might have been born from the same star cluster. Also, stars can disperse a little bit, so 184 light years isn't an implausible distance. And finally, out of all the candidate stars out there, this one is more similar to our sun than them. It's not definitive proof that they were formed together, but there's a hell of a resemblance.
I've read enough serious science articles and seen enough science TV to have gotten the idea that common birth stars travel off in different paths around the galaxy to be far away from each other in a short (by galactic terms) time. The idea that stellar birth suns stay near is unlikely unless there is a specific long term gravitational relationship. Which is unlikely given the random gravitational influences of other stars, galactic revolutions, and the natural wobble of stars above and below the galactic plane. And not to mention dark matter.
Quote from: Cavebear on December 05, 2018, 04:22:21 AM
I've read enough serious science articles and seen enough science TV to have gotten the idea that common birth stars travel off in different paths around the galaxy to be far away from each other in a short (by galactic terms) time. The idea that stellar birth suns stay near is unlikely unless there is a specific long term gravitational relationship. Which is unlikely given the random gravitational influences of other stars, galactic revolutions, and the natural wobble of stars above and below the galactic plane. And not to mention dark matter.
Correct ... 230 million years for the Sun to go around the Galaxy once. So we have been around 18 times now. Think of coffee creamer stirred into coffee.
The key thing, of course, is that our own existence demonstrates that stars coming out of that same nebula would have formed with enough heavy elements ("heavy" meaning anything not hydrogen or helium) to permit the development of complex life. It doesn't mean there is life, but it does mean these are places we can be fairly confident of having all the necessary ingredients. That's terrifically important, especially if we find a solar sibling that's also long-lived stable star like ours -- that's a known potential habitat, not just a possible or theoretical one.
It would be interesting to find that the star has planets, especially if there are any in the habitable zone. I doubt there's a second "Earth" there, though.
Quote from: Unbeliever on December 05, 2018, 01:17:29 PM
It would be interesting to find that the star has planets, especially if there are any in the habitable zone. I doubt there's a second "Earth" there, though.
True and true. All we can say about a solar sibling is that it has all the necessary parts, not that they've actually developed into anything. However, if there's good reason to think it came from the same nebula our sun did, that alone is a good reason to examine it for planets, because we know it came out of a nebula with the material to produce them.
And if we find one, as long as it's not a Jupiter-class world on a highly elliptical orbit, start listening. There might not be a terrestrial planet in the sweet spot, but there might be.
Yeah, we'll never know unless we look. I bet they're already looking closely at it. I sure would be, if I had the instruments.
I consider that there are 2 possibilities of life in the universe. There might be just one (us). Or there might be 3 or more.
But there can't be just 2.
One is a fluke, not likely to be repeated. 3 or more suggests it is common. And if 3, multitudes...
But you just can't have 2 "flukes"...
So we are either alone or of multitudes...
Quote from: Cavebear on December 09, 2018, 10:36:05 AM
I consider that there are 2 possibilities of life in the universe. There might be just one (us). Or there might be 3 or more.
But there can't be just 2.
One is a fluke, not likely to be repeated. 3 or more suggests it is common. And if 3, multitudes...
But you just can't have 2 "flukes"...
So we are either alone or of multitudes...
There is no life. Just dead atoms moving randomly.
Quote from: Baruch on December 09, 2018, 10:49:04 AM
There is no life. Just dead atoms moving randomly.
Atoms are neither alive nor dead. Try again... And, BTW, consider reading the Sept 2018 Scientific American mag. You will love it.
Quote from: Cavebear on December 09, 2018, 10:53:01 AM
Atoms are neither alive nor dead. Try again... And, BTW, consider reading the Sept 2018 Scientific American mag. You will love it.
Blog posts are both meaningful and meaningless.
Quote from: Baruch on December 09, 2018, 11:13:36 AM
Blog posts are both meaningful and meaningless.
No, seriously, I think you would really enjoy reading the SA Sept 2018 issue. It's a lot of "why are we what we are"...
And yeah, I'm behind in my reading...
Quote from: Cavebear on December 09, 2018, 10:36:05 AM
I consider that there are 2 possibilities of life in the universe. There might be just one (us). Or there might be 3 or more.
But there can't be just 2.
One is a fluke, not likely to be repeated. 3 or more suggests it is common. And if 3, multitudes...
But you just can't have 2 "flukes"...
So we are either alone or of multitudes...
I think it more likely that we are alone. But at the same time, there's a "
law of mediocrity (https://en.wikipedia.org/wiki/Mediocrity_principle)' that means we should be approximately typical. I don't know what to believe. But I just feel that we're very much atypical. We've only been looking for ET for a short time, though, so there's no reason to assume too much. We should definitely keep looking, because if we don't we might miss something really interesting out there.
Quote from: Unbeliever on December 09, 2018, 05:38:39 PM
I think it more likely that we are alone. But at the same time, there's a "law of mediocrity (https://en.wikipedia.org/wiki/Mediocrity_principle)' that means we should be approximately typical. I don't know what to believe. But I just feel that we're very much atypical. We've only been looking for ET for a short time, though, so there's no reason to assume too much. We should definitely keep looking, because if we don't we might miss something really interesting out there.
Giant space bypass advertising ... "Eat At Zaphod's Or Zaphod Will Eat You"
Quote from: Unbeliever on December 09, 2018, 05:38:39 PM
I think it more likely that we are alone. But at the same time, there's a "law of mediocrity (https://en.wikipedia.org/wiki/Mediocrity_principle)' that means we should be approximately typical. I don't know what to believe. But I just feel that we're very much atypical. We've only been looking for ET for a short time, though, so there's no reason to assume too much. We should definitely keep looking, because if we don't we might miss something really interesting out there.
There's also the problem of the narrow windows of time in which a technological civilization might be detectable at a distance. We've been emitting significant EM radiation for barely a century and even though the information throughput today is vastly greater than when the first big broadcasters like KDKA and the BBC went on the air, the leakage is growing less and less. Communications are more and more either a tight beam up to a satellite that broadcasts downward -- no use to a listener even as near as Proxima Centauri -- or fiber optic, never even leaving the planet's surface -- no use to a listener even in low Earth orbit. So it may well be that there's only a brief opportunity to hear even a nearby civilization: our radio leakage shouldn't be thought of as a sphere, but as a bubble. Eventually there will be just a shell, and no further way to detect intelligent life here until and unless we terraform another planet in this system (detectable in principle by spectrographic analysis) or do something on the Kardashev scale.
OK, here's my best argument that we are alone as a sentient self-aware technological species in our galaxy...
1. We are a rocky world - Big whoop, right? Well what does it take to make a rocky world? Minerals. Where did they come from? Novae. But when did they happen? After stars died. Those first stars were all hydrogen, etc and little metals when they exploded. The next generation of stars had more (because of the first generation) It wasn't until the 3rd or 4th generation of stars coalecing from gas clouds of metal- enriched elements that a world like Earth was even possible. That's only 4 billion years ago.
2. Our Sun is in the right spot - Yes, just as there is a "goldilock" zone in our solar system, there is one in the galaxy. Too close in and cosmic rays, etc fry you. Too far out and there isn't enough to stimulate life Plus there are less metals out there, so no planets.
3. The Moon - Yeah, that big beauty in the sky. If it weren't for that, we probably wouldn't be here. Venus is like Earth, but no moon. The planetoid that grazed the Earth took off a lot of the crust and added a lot to our core. So Earth has an unusually thin crust and large core.
3A. The thin crust allows for plate tectonics. That allows heavy metals to be drawn from the mantle to the crust (where a species could get at it).
3B. The larger than average core creates our magnetoshphere, which deflects most cosmis and sun rays and protects us from some gamma ray bursts. Those things will fry you.
3C. The large moon tilts our axis, but also restricts over-tipping. We wobble like a fast top "just right" for orbital seasons but not chaos.
4. Simple Cells - Once the Earth had a moon and cooled from the impact, we had simple cells very quickly. But simple cells went about their business, creating nothing complex for 2 billion more years. The galaxy might be filled with bacteria on planets like Earth.
5. Complex Cells - Simple cells lived by engulfing over simple cells. But after 2 billion years, one failed. The engulfed cell survived. And it evolved in the cell to become useful. And when the large cell divided, the smaller cell also divided. The successful ones stayed in the new divided cells. They learned to do that to survive. The ones that didn't died.
6. Bacteria and Archea - The successful cell duo evolved. Some became bacteria, the others archea. The archea became complex (2 cells in one) and then nothing happened for a billion years. Consider that. Just getting 2 cells together took about 2 billion years!
7. And Then The Cambrian explosion - After another 500 million years, a few complex cells got together and basically formed a small sheet to share dead stuff floating down from above. Some complex cells were slightly better at engulfing dead crap and some were slightly better at storing it.
8. Division Of Labor. The cells that engulfed foods benefited from the ones that stored it and vice versa. They looked for what they were best at getting. They formed a mat. Some of the cells lived well in water and some did not. So the ones that did not moved toward the inside of the mat.
9. Specialization - Some mats rolled around, I suppose, and made shapes that improved the abilities of the food-collecting to be on the outside and the cells that used the food ended up on the inside. So you had things like sponges etc. Well one location encourages some traits and another location encourges differebt one.
So after 13 billion years, there were dumb sponges. Hurray!
10. Competition - As soon as there were 2 versions of rolled up mats, there was a competition for making more. Eventually, one type could eat the other.
11. The Arms And Food Race - The first thing that could find and eat another was a winner. And if you were on the food end, you tried to not be eaten. Voila! Armor and Protection.
12. Animals - After the first competition, surviving meant having some smarts. Like maybe an organ that could BARELY detect a shadow of something trying to eat it. Or detecting daylight (when food was "up") and night (when safety was "down").
13. Not US Yet - The rest of the story is how to make a sentient being from a mat of spongey stuff. Senses is the word. Not just a dim light or a surface touch thing. The eye became cuplike to capture kight better, the cup had a membrane behind, and the eye made some nerves to grow together.
14. US - You can guess the rest. It was all about senses. They connected at one general place, around that place became a brain.
15. can guess about sentience from there all you want. But is an unlikely thing. No cat ever drew a diagram, no dog ever made a spear.
16. So how likely is it that any planet anywhere has any thing more complex that simple cells in just 500 million years?
Damn near zero...
Good post! I recommend the book Rare Earth, by Ward and Brownlee. An excellent overview of why we're probably the only sentient life anywhere in the galaxy. They discuss all the points you raised.
This is why I don't worry about alien invasion - there are no aliens.
Quote from: Unbeliever on December 21, 2018, 01:20:11 PM
Good post! I recommend the book Rare Earth, by Ward and Brownlee. An excellent overview of why we're probably the only sentient life anywhere in the galaxy. They discuss all the points you raised.
This is why I don't worry about alien invasion - there are no aliens.
Fears of aliens can get really weird. I used to worry about the Voyager disks saying where we are. Then I realized they are barely out of the solar system. So if anything found them, they would already be here. And by the time they get any where, we would be so much more advanced it would be ridiculous.
Quote from: Unbeliever on December 21, 2018, 01:20:11 PM
Good post! I recommend the book Rare Earth, by Ward and Brownlee. An excellent overview of why we're probably the only sentient life anywhere in the galaxy. They discuss all the points you raised.
This is why I don't worry about alien invasion - there are no aliens.
My argument is similarly egotistical ... why I am the only sentient on Earth ;-)