LtStorm posted:

Yeah, the specific thing we know is that the objects in the Kuiper belt move with complexities we don't understand. As far as we are sure of they're all smaller than planets, yet they move as a group like something with a much greater mass is out there. We don't know why yet.

Libluini posted:

I think this thread is convincing me more and more that FTL is possible.

Libluini posted:

It's a bit more complicated then this, there are already predictions for possible orbits for the mystery object, but since they're so far out, the ongoing search for them is slow and tedious. And of course if it turns out there isn't another ice giant out there, utterly pointless. But since we won't know until we try, well.

drilldo squirt posted:

So what about a racecar going 99% the speed of light on a train going 99% the speed of light like in the webcomic?

Raenir Salazar posted:

Hey guys, the Expanse apparently has aired season 4 on Amazon Prime video and everyone should check it out!

I haven't paid much close attention to any of the science or anything but one thing DID stand out in episode 2 in light of the thread.



The Exo/Xenobiologist lady said something along the lines of "Life doesn't have to form as carbon based life, nothing says it couldn't also happen with any other element like iron."


I remember the thread discussing the chemistry of life many pages ago. Minor nitpick, continue on.

LtStorm posted:

I was one of the ones discussing that! She's right, there could be iron-based life though we might have trouble recognizing it because it would be so alien. That line is almost assuredly in the show because desert varnish could be the pre-biotic version of such life, such as a primordial ooze (be it in tidal pools, undersea cliffs, undersea volcanic vent, or wherever) was our pre-biotic predecessor.

drilldo squirt posted:

So what about a racecar going 99% the speed of light on a train going 99% the speed of light like in the webcomic?

drilldo squirt posted:

So what about a racecar going 99% the speed of light on a train going 99% the speed of light like in the webcomic?

LtStorm posted:

I was one of the ones discussing that! She's right, there could be iron-based life though we might have trouble recognizing it because it would be so alien. That line is almost assuredly in the show because desert varnish could be the pre-biotic version of such life, such as a primordial ooze (be it in tidal pools, undersea cliffs, undersea volcanic vent, or wherever) was our pre-biotic predecessor.

Antifa Turkeesian posted:

Is there a pretty good chance that the predicted super-earth-mass object out in our solar system is really a thing and not an error in reading the data?

Libluini posted:

And then there was this weird Soviet SF-story I've read many years ago where the Soviet space men meet an alien space ship and the aliens turn out to have a Boron-based biology. And as if that wasn't absurd enough, the Soviet scientists find a way to help their Communist alien comrades, since Boron is claimed to be "inferior" to the mighty Carbon. They develop a way to replace the Boron in the aliens' bodies with Carbon and the alien communists rejoice when they hear the news! The End. No Moral.

WAR CRIME GIGOLO posted:

Gonna need to toke on this one

D-Pad posted:

I have an old 80s book called Texas Truimphant that has Texas as an independent country that fights the soviet union. A massive soviet tank formation rolls up on Texas soil, and the tanks are having a hard time in muddy ground so the commander gets out. He realizes the ground is soaked in oil as he looks up and sees a guy on horseback dressed as the lone ranger on top of a hill. Lone ranger shoots a flaming arrow and blows them all up. It also features space battles between Texas astronauts and cosmonauts and a bunch of other ridiculous Texas fanfiction. It's amazing and part of a trilogy although I haven't been able to find the rest.

Not sure what that has to do with the thread but the soviet sci fi convo made me think of it.

D-Pad posted:

I have an old 80s book called Texas Truimphant that has Texas as an independent country that fights the soviet union. A massive soviet tank formation rolls up on Texas soil, and the tanks are having a hard time in muddy ground so the commander gets out. He realizes the ground is soaked in oil as he looks up and sees a guy on horseback dressed as the lone ranger on top of a hill. Lone ranger shoots a flaming arrow and blows them all up. It also features space battles between Texas astronauts and cosmonauts and a bunch of other ridiculous Texas fanfiction. It's amazing and part of a trilogy although I haven't been able to find the rest.

Not sure what that has to do with the thread but the soviet sci fi convo made me think of it.

ashpanash posted:

Raenir Salazar posted:

Hey guys, the Expanse apparently has aired season 4 on Amazon Prime video and everyone should check it out!

I haven't paid much close attention to any of the science or anything but one thing DID stand out in episode 2 in light of the thread.



The Exo/Xenobiologist lady said something along the lines of "Life doesn't have to form as carbon based life, nothing says it couldn't also happen with any other element like iron."


I remember the thread discussing the chemistry of life many pages ago. Minor nitpick, continue on.

ashpanash posted:

Kesper North posted:

wow

Are the Native Americans supposed to be on the, uh, Texan side in this one?

Sensationalist Pop Science Reporting posted:

Study Claims Technologically Advanced Species Could Have Been On Earth Tens Of Millions Of Years Ago

We like to think that we are an exception: An intelligent life that has developed a vastly complex industrialized civilization unlike anything seen before. But would we actually know if millions of years ago some other life forms had created huge cities, altered the landscape, and formed their own civilization? What would be left of their exploits for us to find?

This is the thought experiment that the director of NASA’s Goddard Institute for Space Studies, Gavin Schmidt, and professor of physics and astronomy at the University of Rochester, Adam Frank, have been exploring. They want to understand if any evidence of a hugely advanced civilization could persist tens of millions of years into the future and, if so, what form it might take. Their results are published in the International Journal of Astrobiology.

“Gavin and I have not seen any evidence of another industrial civilization,” Frank lays out from the onset. Since they have not found any pre-human civilization, they have been looking at what impact we as a species are having on the planet, and how long those impacts are likely to be detectable into the future. “These questions make us think about the future and the past in a much different way, including how any planetary-scale civilization might rise and fall.”

While we have plenty of evidence of past civilizations in the form of statutes and foundations that date back maybe a few thousand years at most, things get far more opaque when the clock is rolled back by a few million or hundreds of millions of years.

Calling this the “Silurian hypothesis” – after the technologically advanced reptiles from Dr. Who – they speculate what would be left if a civilization lasted for 100,000 years or so around 60 million years ago. That may sound like a long time, but in the history of the Earth, it is but a blip. However, the chance of fossils would be rare, so what else could we look for?

As a species, we are currently laying down all sorts of traces that will be detectable in a 100 million years’ time. In feeding 7 billion people, we’ve completely altered the nitrogen cycle, with much of it now finding its way into sediment at the bottom of the ocean and the tops of mountains. On the flip side, rare earth elements that were once buried deep are now floating free at the surface as we develop ever more complex technology.

That’s not to mention the changes in the carbon cycle from burning so much fossil fuel or the millions of tonnes of plastic being laid down. Some have even suggested that all the plastic we’re producing is forming a new kind of rock, and all these changes will still be detectable far into the future.

All this is obviously hypothetical at the moment, but it has an important point. These are the kind of clues we could use to look for previously advanced civilizations on other planets.

“We know early Mars and, perhaps, early Venus were more habitable than they are now, and conceivably we will one day drill through the geological sediments there, too,” says Gavin Schmidt. “This helps us think about what we should be looking for.”

Still Sensationalist Pop Science Reporting posted:

Was There a Civilization On Earth Before Humans?

When it comes to direct evidence of an industrial civilization—things like cities, factories, and roads—the geologic record doesn’t go back past what’s called the Quaternary period 2.6 million years ago. For example, the oldest large-scale stretch of ancient surface lies in the Negev Desert. It’s “just” 1.8 million years old—older surfaces are mostly visible in cross section via something like a cliff face or rock cuts. Go back much farther than the Quaternary and everything has been turned over and crushed to dust.

And, if we’re going back this far, we’re not talking about human civilizations anymore. Homo sapiens didn’t make their appearance on the planet until just 300,000 years or so ago. That means the question shifts to other species, which is why Gavin called the idea the Silurian hypothesis, after an old Dr. Who episode with intelligent reptiles.

So, could researchers find clear evidence that an ancient species built a relatively short-lived industrial civilization long before our own? Perhaps, for example, some early mammal rose briefly to civilization building during the Paleocene epoch about 60 million years ago. There are fossils, of course. But the fraction of life that gets fossilized is always minuscule and varies a lot depending on time and habitat. It would be easy, therefore, to miss an industrial civilization that only lasted 100,000 years—which would be 500 times longer than our industrial civilization has made it so far.

Given that all direct evidence would be long gone after many millions of years, what kinds of evidence might then still exist? The best way to answer this question is to figure out what evidence we’d leave behind if human civilization collapsed at its current stage of development.

Now that our industrial civilization has truly gone global, humanity’s collective activity is laying down a variety of traces that will be detectable by scientists 100 million years in the future. The extensive use of fertilizer, for example, keeps 7 billion people fed, but it also means we’re redirecting the planet’s flows of nitrogen into food production. Future researchers should see this in characteristics of nitrogen showing up in sediments from our era. Likewise our relentless hunger for the rare-Earth elements used in electronic gizmos. Far more of these atoms are now wandering around the planet’s surface because of us than would otherwise be the case. They might also show up in future sediments, too. Even our creation, and use, of synthetic steroids has now become so pervasive that it too may be detectable in geologic strata 10 million years from now.

Still Sensationalist Pop Science Reporting posted:

When we burn fossil fuels, we’re releasing carbon back into the atmosphere that was once part of living tissues. This ancient carbon is depleted in one of that element’s three naturally occurring varieties, or isotopes. The more fossil fuels we burn, the more the balance of these carbon isotopes shifts. Atmospheric scientists call this shift the Suess effect, and the change in isotopic ratios of carbon due to fossil-fuel use is easy to see over the last century. Increases in temperature also leave isotopic signals. These shifts should be apparent to any future scientist who chemically analyzes exposed layers of rock from our era. Along with these spikes, this Anthropocene layer might also hold brief peaks in nitrogen, plastic nanoparticles, and even synthetic steroids. So if these are traces our civilization is bound to leave to the future, might the same “signals” exist right now in rocks just waiting to tell us of civilizations long gone?

Fifty-six million years ago, Earth passed through the Paleocene-Eocene Thermal Maximum (PETM). During the PETM, the planet’s average temperature climbed as high as 15 degrees Fahrenheit above what we experience today. It was a world almost without ice, as typical summer temperatures at the poles reached close to a balmy 70 degrees Fahrenheit. Looking at the isotopic record from the PETM, scientists see both carbon and oxygen isotope ratios spiking in exactly the way we expect to see in the Anthropocene record. There are also other events like the PETM in the Earth’s history that show traces like our hypothetical Anthropocene signal. These include an event a few million years after the PETM dubbed the Eocene Layers of Mysterious Origin, and massive events in the Cretaceous that left the ocean without oxygen for many millennia (or even longer).

Are these events indications of previous nonhuman industrial civilizations? Almost certainly not. While there is evidence that the PETM may have been driven by a massive release of buried fossil carbon into the air, it’s the timescale of these changes that matter. The PETM’s isotope spikes rise and fall over a few hundred thousand years. But what makes the Anthropocene so remarkable in terms of Earth’s history is the speed at which we’re dumping fossil carbon into the atmosphere. There have been geological periods where Earth’s CO2 has been as high or higher than today, but never before in the planet’s multibillion-year history has so much buried carbon been dumped back into the atmosphere so quickly. So the isotopic spikes we do see in the geologic record may not be spiky enough to fit the Silurian hypothesis’s bill.

But there is a conundrum here. If an earlier species’s industrial activity is short-lived, we might not be able to easily see it. The PETM’s spikes mostly show us the Earth’s timescales for responding to whatever caused it, not necessarily the timescale of the cause. So it might take both dedicated and novel detection methods to find evidence of a truly short-lived event in ancient sediments. In other words, if you’re not explicitly looking for it, you might not see it. That recognition was, perhaps, the most concrete conclusion of our study.

Still Sensationalist Pop Science Reporting posted:

By asking about civilizations lost in deep time, we’re also asking about the possibility for universal rules guiding the evolution of all biospheres in all their creative potential, including the emergence of civilizations. Even without pickup-driving Paleocenians, we’re only now learning to see how rich that potential might be.

Libluini posted:

That's interesting! The only alternate element I've heard people discussing before was Silicon. Something about Silicon being able to almost bind as good as Carbon.

And then there was this weird Soviet SF-story I've read many years ago where the Soviet space men meet an alien space ship and the aliens turn out to have a Boron-based biology. And as if that wasn't absurd enough, the Soviet scientists find a way to help their Communist alien comrades, since Boron is claimed to be "inferior" to the mighty Carbon. They develop a way to replace the Boron in the aliens' bodies with Carbon and the alien communists rejoice when they hear the news! The End. No Moral.

DrSunshine posted:

I want to return to the conversation about Von Neumann probes for a moment. I was thinking about them the other day. I wonder if the approach on them is a little bit misguided and rooted too heavily on our existing concepts and paradigms of engineering - almost like those old Victorian paintings of 'life in the year 2000' that show people in tophats and corset dresses with miniature dirigibles or playing croquet at the bottom of the sea.

See, it occurs to me that a self-replicating probe that is designed to set down and start sending out robots to mine for ores and build factories so that it can launch more rockets seems like a really overcomplicated task. What we're doing here is trying to invent a machine that is smart enough to basically set up a miniature version of our own presently-existing industrial process network. But even the process for making a single component, like an integrated circuit, is a tremendously complex thing with thousands of intricate steps, even disregarding the process of having to mine and fabricate the input components and materials. Moreover, there's little guarantee that any of the raw materials required for a complex metallic machine will even be available to easily-reachable locations on some distant exoplanet or asteroid.

Taking a cue from the history of life on earth, the first autonomous self-replicators on this world were built out of the most common elements in the universe - carbon, hydrogen, oxygen - and operated at temperature and pressure gradients found in naturally-existing environments. That's not to say that organic life isn't an insanely complicated series of chemical reactions involving millions of enzymes, proteins, and molecules evolved over billions of years. But the advantage, and the point that I'm getting at, is that organic life is built out of some of the most readily-accessible materials and operates in ranges that one might expect to find around the cosmos. It would take a tremendous amount of energy and effort to recreate the conditions of the inside of a blast furnace, which only exists in places like the cores of planets. Likewise, it takes a huge amount of infrastructure and engineering to create open-pit boreholes to mine for rare earth metals. It'd be inefficient to limit yourself in this way when there's a whole universe full of carbonaceous asteroids, comets filled with water and methane ices, and silicates and gases on rocky planets.

So I wonder if perhaps a future design for a Von Neumann probe might take this into account, and be based on some kind of organic machinery, and be designed to fabricate and replicate copies of itself just based on gathering resources that are plentiful either on the surfaces of rocky planets, or on asteroids and comets?

John von Neumann posted:

A coded representation of the replicator
A mechanism to copy the coded representation
A mechanism for effecting construction within the host environment of the replicator

quote:

Several groups of carbonaceous chondrites, notably the CM and CI groups, contain high percentages (3% to 22%) of water,[2] as well as organic compounds. They are composed mainly of silicates, oxides and sulfides, with the minerals olivine and serpentine being characteristic. The presence of volatile organic chemicals and water indicates that they have not undergone significant heating (>200 °C) since they were formed, and their compositions are considered to be close to that of the solar nebula from which the Solar System condensed. Other groups of C chondrites, e.g., CO, CV, and CK chondrites, are relatively poor in volatile compounds, and some of these have experienced significant heating on their parent asteroids.

quote:

The solid, core structure of a comet is known as the nucleus. Cometary nuclei are composed of an amalgamation of rock, dust, water ice, and frozen carbon dioxide, carbon monoxide, methane, and ammonia.

Captain Monkey posted:

Yeah, just solve the ‘create wormholes’ problem and we’re there.

Captain Monkey posted:

Yeah, just solve the ‘create wormholes’ problem and we’re there.