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I think it's interesting to speculate on how an alien civilization might develop technology, and in what order, if they were to originate on a planet with diffe

I think it's interesting to speculate on how an alien civilization might develop technology, and in what order, if they were to originate on a planet with different ratios of elements than Earth, including access to these super heavy elements.

ajross 3y ago
There is no reason to suspect any of these elements are stable. The paper seems to be alleging that they existed in quantity at the end of the r-process such that they produced otherwise hard to explain ratios of other stable nucleii (i.e. their fission products). If there were stable transuranic nucleii, we'd need to work very hard to explain why we can't find any in the universe.
- thsksbd 3y ago
  Well we know how stable many of them are - we've synthesized them and out them in our fire alarms
Cockbrand 3y ago
Andy Weir‘s novel Project Hail Mary explores this to some extent. Well, not super heavy elements, but heavier ones than the stuff we’re made of.
philipkglass 3y ago
All of these super heavy elements are radioactive with short half lives, so they wouldn't be accessible as ores even on planets that formed close to these stars. The article refers to elements with atomic weights higher than 260, which would mean elements like lawrencium and rutherfordium; they all have half lives of less than a day. I have had a related thought about uranium, though. The fissile isotope that's useful for power generation and bombs, uranium 235, is only about 0.7% of uranium that's found on Earth. When uranium is formed in a supernova, there's actually more uranium 235 produced than uranium 238; this freshly produced uranium is about 62% U-235 [1]. The reason that U-235 is so rare on Earth is that U-235 decays faster than U-238 and our uranium is billions of years old. But if it's possible for a technological civilization to develop on a planet with much fresher uranium content, natural uranium there could contain a double-digit percentage of U-235. Under those conditions it would be easy to accidentally discover nuclear fission and naturally occurring reactors like Oklo [2] would be common. [1] https://world-nuclear.org/information-library/nuclear-fuel-cycle/uranium-resources/the-cosmic-origins-of-uranium.aspx https://world-nuclear.org/information-library/nuclear-fuel-c... [2] https://www.iaea.org/newscenter/news/meet-oklo-the-earths-two-billion-year-old-only-known-natural-nuclear-reactor https://www.iaea.org/newscenter/news/meet-oklo-the-earths-tw...
- chasil 3y ago
  If the Cambrian explosion had happened sooner, then this would have been possible.
  - cstross 3y ago
    The Cambrian explosion was, however, constrained by the partial pressure of oxygen in the hydrosphere (and, indirectly, the atmosphere). And free O2 couldn't begin to build up in seawater until after the Great Oxygen Catastrophe when the crust and upper mantle was finally fully oxidized, mopping up all the unoxidized iron and other elements. (Which in turn killed off almost all previous life forms, which were methanogenic and to which oxygen was a deadly poison/metabolic waste product.) The speed with which this happened was in turn constrained by tectonic subduction ... it all turns out to be a knotty ball of string that took at least a couple of billion years to unwind.
- consp 3y ago
  > they all have half lives less than a day. Isn't it the case it is currently not possible to create any neutron heavy isotopes and that causes the half-lives to be on the low end?
  - philipkglass 3y ago
    Isn't it the case it is currently not possible to create any neutron heavy isotopes and that causes the half-lives to be on the low end? All of these isotopes are neutron-heavy. Lawrencium 261 has 103 protons and 158 neutrons, for example. In fact, the only stable isotopes with fewer neutrons than protons are helium 3 and ordinary hydrogen (protium).
    - saalweachter 3y ago
      I think he's referring to the way that eg lawrencium has a half-life that ~increases with the neutrons in the isotopes we've produced, from seconds for Lr-256 to hours for Lr-266. It isn't crazy to postulate, as a layman, that if we synthesized Lr-276, say, it might have a longer half-life. (Not that we expect that pattern to continue indefinitely, but still, have we discovered the most stable isotope of lawrencium yet?)
thsksbd 3y ago
A more interesting question is if an alien race can exist with ratios that differ considerably from the ones on earth. Outside of carbon chemistry your ability to create replicable life plummets. Biologists may speculate if non carbon life is possible, but there's no doubt it would be limited. Arsenic or silicon just don't have the chemical complexity carbon does. As for super heavy elements - the elements alien races would have access to wouldn't be that different from ours. Heavy nuclei are terribly radioactive and thus short lived. The article points our elements heavier than 260 are too short lived, but on astronomical (and biological) scales anything past 238 (ie Uranium) is short lived. Past Uranium (which we have on Earth naturally), only Pu-244 is relatively long lived. Its half life is 81 million years vs. U-238 at 2 billion years. 81 million sounds like a long time, but the alien race has to evolve intelligence. We've been evolving for about 4 billion years, or 40 halvings of Pu-244 initial (anyway low) concentration. 2^-40 is a small number. By comparison U-238 has halved only twice on Earth since evolution started. To illustrate, if the entire Sun were made of Pu-244 and the entirety of the remaining Pu-244 were put on Earth after 4 billion years, the concentration would be less than 1 part per million per mass.
- blacksmith_tb 3y ago
  There's been recent talk of finding a new island of stability[1] though I don't think we imagine those super-heavy elements would have half-lives of more than thousands of years (so probably not very handy for alien engineers). 1: https://en.wikipedia.org/wiki/Island_of_stability#Possible_natural_occurrence https://en.wikipedia.org/wiki/Island_of_stability#Possible_n...
  - thsksbd 3y ago
    Yea, and it is super cool to think that, but either 1. the kinetic barrier is impossibly large that even novas cant cross it, or 2. the "stable" elements are not very long lived in astronomical time scales. Probably both are true, either way, it's a wash - no super heavy elements for alien races to play with.
- scotty79 3y ago
  > Outside of carbon chemistry your ability to create replicable life plummets. Biologists may speculate if non carbon life is possible, but there's no doubt it would be limited. Arsenic or silicon just don't have the chemical complexity carbon does. Best argument for carbon I've seen so far is that despite carbon being just 0.02% of all elements on earth it became preferred engine of life. Although I can't rule out that under different temperature, pressures and radiation some other element might be preferred if it's reasonably abundant somewhere. In my opinion if there's mostly stable, reasonable energy gradient somewhere life will find a way if possible.
deleted 3y ago
[deleted]
jylam 3y ago
Isn't there a probable island of stability, with very heavy, stable elements ?
- Sharlin 3y ago
  Possible, not probable. It’s a cool idea but even if the island is theoretically possible and there’s some real astrophysical process that could actually synthetize such nuclei, they’d likely still be only "stable" relative to other superheavy elements. That is, half-lifes from seconds to years or something like that rather than microseconds.
  - jylam 3y ago
    Ok, looked back at some stuff I read, and yes we are talking about half-lives of a couple of years at most. Disappointing, but thank you :)
- NoMoreNicksLeft 3y ago
  In later years, I thought it had changed to "relatively stable"... as in elements that have half-lives in minutes rather than in milliseconds.
Nevermark 3y ago
Water worlds intrigue me. All the elements and heat vents you might need for life. But how do you develop the technology for an escape velocity civilization in a medium so corrosive and viscous? Super Earths are a likely source of water worlds, since the same percentage of water volume (~ to radius^3) results in much deeper oceans at the surface (~ to radius^2). The greater gravity would create even more hurdles. How do you hit escape velocity if your fuel to orbit is to heavy to lift itself? First orbital vehicle might have to be nuclear. Problem 1: Develop a civilization with a sustained technology runway in a medium that corrodes, relentlessly saps temperature gradients, creates immense pressure at its solid floor, etc. Problem 2: Create floating platforms and colonize their ocean surface. Problem 3: Develop atmospheric flight, from their bobbing surface colonies, with heavy water filled planes. Problem 4: Develop orbital flight with water filled space craft. Problem 5: Develop sustainable water filled living environments off planet, as first step to going beyond. And do this before their star or other cause finishes them off!

ajross 3y ago

There is no reason to suspect any of these elements are stable. The paper seems to be alleging that they existed in quantity at the end of the r-process such that they produced otherwise hard to explain ratios of other stable nucleii (i.e. their fission products). If there were stable transuranic nucleii, we'd need to work very hard to explain why we can't find any in the universe.

thsksbd 3y ago
Well we know how stable many of them are - we've synthesized them and out them in our fire alarms

Cockbrand 3y ago

Andy Weir‘s novel Project Hail Mary explores this to some extent. Well, not super heavy elements, but heavier ones than the stuff we’re made of.

philipkglass 3y ago

All of these super heavy elements are radioactive with short half lives, so they wouldn't be accessible as ores even on planets that formed close to these stars. The article refers to elements with atomic weights higher than 260, which would mean elements like lawrencium and rutherfordium; they all have half lives of less than a day. I have had a related thought about uranium, though. The fissile isotope that's useful for power generation and bombs, uranium 235, is only about 0.7% of uranium that's found on Earth. When uranium is formed in a supernova, there's actually more uranium 235 produced than uranium 238; this freshly produced uranium is about 62% U-235 [1]. The reason that U-235 is so rare on Earth is that U-235 decays faster than U-238 and our uranium is billions of years old. But if it's possible for a technological civilization to develop on a planet with much fresher uranium content, natural uranium there could contain a double-digit percentage of U-235. Under those conditions it would be easy to accidentally discover nuclear fission and naturally occurring reactors like Oklo [2] would be common. [1] https://world-nuclear.org/information-library/nuclear-fuel-cycle/uranium-resources/the-cosmic-origins-of-uranium.aspx https://world-nuclear.org/information-library/nuclear-fuel-c... [2] https://www.iaea.org/newscenter/news/meet-oklo-the-earths-two-billion-year-old-only-known-natural-nuclear-reactor https://www.iaea.org/newscenter/news/meet-oklo-the-earths-tw...

chasil 3y ago
If the Cambrian explosion had happened sooner, then this would have been possible.
- cstross 3y ago
  The Cambrian explosion was, however, constrained by the partial pressure of oxygen in the hydrosphere (and, indirectly, the atmosphere). And free O2 couldn't begin to build up in seawater until after the Great Oxygen Catastrophe when the crust and upper mantle was finally fully oxidized, mopping up all the unoxidized iron and other elements. (Which in turn killed off almost all previous life forms, which were methanogenic and to which oxygen was a deadly poison/metabolic waste product.) The speed with which this happened was in turn constrained by tectonic subduction ... it all turns out to be a knotty ball of string that took at least a couple of billion years to unwind.
consp 3y ago
> they all have half lives less than a day. Isn't it the case it is currently not possible to create any neutron heavy isotopes and that causes the half-lives to be on the low end?
- philipkglass 3y ago
  Isn't it the case it is currently not possible to create any neutron heavy isotopes and that causes the half-lives to be on the low end? All of these isotopes are neutron-heavy. Lawrencium 261 has 103 protons and 158 neutrons, for example. In fact, the only stable isotopes with fewer neutrons than protons are helium 3 and ordinary hydrogen (protium).
  - saalweachter 3y ago
    I think he's referring to the way that eg lawrencium has a half-life that ~increases with the neutrons in the isotopes we've produced, from seconds for Lr-256 to hours for Lr-266. It isn't crazy to postulate, as a layman, that if we synthesized Lr-276, say, it might have a longer half-life. (Not that we expect that pattern to continue indefinitely, but still, have we discovered the most stable isotope of lawrencium yet?)

thsksbd 3y ago

A more interesting question is if an alien race can exist with ratios that differ considerably from the ones on earth. Outside of carbon chemistry your ability to create replicable life plummets. Biologists may speculate if non carbon life is possible, but there's no doubt it would be limited. Arsenic or silicon just don't have the chemical complexity carbon does. As for super heavy elements - the elements alien races would have access to wouldn't be that different from ours. Heavy nuclei are terribly radioactive and thus short lived. The article points our elements heavier than 260 are too short lived, but on astronomical (and biological) scales anything past 238 (ie Uranium) is short lived. Past Uranium (which we have on Earth naturally), only Pu-244 is relatively long lived. Its half life is 81 million years vs. U-238 at 2 billion years. 81 million sounds like a long time, but the alien race has to evolve intelligence. We've been evolving for about 4 billion years, or 40 halvings of Pu-244 initial (anyway low) concentration. 2^-40 is a small number. By comparison U-238 has halved only twice on Earth since evolution started. To illustrate, if the entire Sun were made of Pu-244 and the entirety of the remaining Pu-244 were put on Earth after 4 billion years, the concentration would be less than 1 part per million per mass.

blacksmith_tb 3y ago
There's been recent talk of finding a new island of stability[1] though I don't think we imagine those super-heavy elements would have half-lives of more than thousands of years (so probably not very handy for alien engineers). 1: https://en.wikipedia.org/wiki/Island_of_stability#Possible_natural_occurrence https://en.wikipedia.org/wiki/Island_of_stability#Possible_n...
- thsksbd 3y ago
  Yea, and it is super cool to think that, but either 1. the kinetic barrier is impossibly large that even novas cant cross it, or 2. the "stable" elements are not very long lived in astronomical time scales. Probably both are true, either way, it's a wash - no super heavy elements for alien races to play with.
scotty79 3y ago
> Outside of carbon chemistry your ability to create replicable life plummets. Biologists may speculate if non carbon life is possible, but there's no doubt it would be limited. Arsenic or silicon just don't have the chemical complexity carbon does. Best argument for carbon I've seen so far is that despite carbon being just 0.02% of all elements on earth it became preferred engine of life. Although I can't rule out that under different temperature, pressures and radiation some other element might be preferred if it's reasonably abundant somewhere. In my opinion if there's mostly stable, reasonable energy gradient somewhere life will find a way if possible.

deleted 3y ago

[deleted]

jylam 3y ago

Isn't there a probable island of stability, with very heavy, stable elements ?

Sharlin 3y ago
Possible, not probable. It’s a cool idea but even if the island is theoretically possible and there’s some real astrophysical process that could actually synthetize such nuclei, they’d likely still be only "stable" relative to other superheavy elements. That is, half-lifes from seconds to years or something like that rather than microseconds.
- jylam 3y ago
  Ok, looked back at some stuff I read, and yes we are talking about half-lives of a couple of years at most. Disappointing, but thank you :)
NoMoreNicksLeft 3y ago
In later years, I thought it had changed to "relatively stable"... as in elements that have half-lives in minutes rather than in milliseconds.

Nevermark 3y ago

Water worlds intrigue me. All the elements and heat vents you might need for life. But how do you develop the technology for an escape velocity civilization in a medium so corrosive and viscous? Super Earths are a likely source of water worlds, since the same percentage of water volume (~ to radius^3) results in much deeper oceans at the surface (~ to radius^2). The greater gravity would create even more hurdles. How do you hit escape velocity if your fuel to orbit is to heavy to lift itself? First orbital vehicle might have to be nuclear. Problem 1: Develop a civilization with a sustained technology runway in a medium that corrodes, relentlessly saps temperature gradients, creates immense pressure at its solid floor, etc. Problem 2: Create floating platforms and colonize their ocean surface. Problem 3: Develop atmospheric flight, from their bobbing surface colonies, with heavy water filled planes. Problem 4: Develop orbital flight with water filled space craft. Problem 5: Develop sustainable water filled living environments off planet, as first step to going beyond. And do this before their star or other cause finishes them off!