The Astronomy Thread

iannis · Jun 1, 2015

They had a hootananny about 7,000 years ago and were QUITE PUT OFF by our passive aggressive RSVP snub. We did not RS or VP. Neither one.

For a B.E.M. that's sort of a big deal. An unbearable deficiency of tact.

Tuco · Jun 1, 2015

reveite s'il vous plait?

Szlia · Jun 1, 2015

Mais que veut dire "reveite"?

I don't see what is so paradoxical about the Fermi paradox. It feels to me it is built on a number of weak assumptions. I mean, here on planet earth, right now, there are several million different types of life forms (8.7 some say - bacteria and the likes excluded). Put them all except humans on an earth like planet in a neighboring solar system and SETI would not detect them.

Lithose · Jun 1, 2015

Szlia_sl said:
Mais que veut dire "reveite"?

I don't see what is so paradoxical about the Fermi paradox. It feels to me it is built on a number of weak assumptions. I mean, here on planet earth, right now, there are several million different types of life forms (8.7 some say - bacteria and the likes excluded). Put them all except humans on an earth like planet in a neighboring solar system and SETI would not detect them.

Well, the paradox isn't about life, it's about intelligent life. Yes, there are some serious assumptions made, but the reason why it's troubling is because the sheer numerical scales that it takes into account. It's just troubling to believe either 1.) With millions of potential life bearing planets, we are the only ones that produced intelligence. 2.) Intelligence is out there and for some reason is ignoring us. (We assume it is ignoring us, because as said, even with sub light engines a fully tier 1 society would populate the galaxy in 4 million years.)

But yeah, there are all kinds of reasons why not. Maybe intelligence is actually an extremely rare subset of life (Which is a rare subset of chemical copying)...Evolution, after all, is not a drive to "be the best"--but rather a drive to "fit in the best". So in many cases maybe intelligence was not the top of the ladder. There could also be some kind of barrier that consistently destroys intelligence at a certain point--like maybe harnessing some quantum force, that we have yet to discover, can blow up solar systems--and every intelligence race has blown themselves up. Or maybe, at a certain point, it just becomes stupid to want to explore--because digital evolutions allow you to build your own universes. (Maybe we are in a universe from a species that made it this far--who in turn were a species in a digital universe, from ANOTHER species that made it that far?!?!)

Anyway, yeah, lots and lots of assumptions. I think the Fermi paradox is really just supposed to illustrate the numbers to people so they can really think about the sheer size of the universe.

khorum · Jun 1, 2015

This came up in the old foh boards too. The whole drake equation vs. fermi paradox argument has spawned a lot of awesome speculation as why there isn't more obvious evidence of intelligent life.

I'm a fan of the Carter Catastrophe/Doomsday Equation argument myself. Based on a range of how many humans have lived so far, there's a statistical probability of 95% that human civilization will last only another 9,120 years. There's a lot of variables obviously, but even if the Singularitarians are right and we achieve biological immortality in this century it would only bump the doomsday argument's outcome to about 180,000 years. That's purely on a bayesian curve of where we are on the population scale between the first human and extinction.

200k years doesn't even qualify as a blink in cosmological time---the dinosaurs of the jurassic lasted 300 times that long. So drake AND fermi could both be right and all those technological civilizations just twinkle in and out of existence faster than they can escape math. You don't need Reapers or Superintelligent AI that converts whole planets into paperclips or Kardashev Type-1 people hiding in dyson spheres... they just fade out.

iannis · Jun 2, 2015

While that's certainly possible, it is hard to believe that there isn't some sort of critical mass for civilization.

I wouldn't say we're at it yet. Or that we will be in the next few hundred years. But in over 9,000? If we colonize mars and a jovian moon, and then press into another solar system, there has to be a point where the the entire system will NOT all devolve at the same time. Civ rises and Civ falls, but the more you seed the less likely that it will all die at the same time.

Just for the sociologic side of things. If a star blows up. Well, I mean, fuck it. We had a good run. God can just be an asshole sometimes.

Tuco · Jun 2, 2015

Szlia_sl said:
Mais que veut dire "reveite"?

I don't see what is so paradoxical about the Fermi paradox. It feels to me it is built on a number of weak assumptions. I mean, here on planet earth, right now, there are several million different types of life forms (8.7 some say - bacteria and the likes excluded). Put them all except humans on an earth like planet in a neighboring solar system and SETI would not detect them.

I dont think you understand the problem. The article describes it very well but the paradox isnt that we dont see other civs like ours. It is that we dont see any civs much beyond our tech tree.

Dandain · Jun 2, 2015

When thinking of the Fermi Paradox this is what helped me contextualize it a bit. Our modern civilization is consuming a very substantial amount of energy. Currently we consume mostly stored sunlight from millions of years in the past we dig up out of the ground, but one fact seems to remain. As a civilization becomes more advanced it will need more energy as it advances. This increased consumption releases a meaningful amount of heat. If a species say - populated an entire galaxy - we should be able to detect the heat that their society would use to function on this astronomical scale. There is at least one experiment/telescope/instrument being developed with the task of hunting for this heat, as I believe it can be used to determine if there is at least substantial biological/technological heat being generated on the surface of a planet. Try and think what a distant civilization might conclude about Earth when they begin to measure it against all the planets they find with their observation and measuring tools.

Szlia · Jun 2, 2015

"any civs beyond our tech tree" is something already laced with assumptions. Assumptions about our own future (the fantasy civ is like us, but in the future - so assumptions about what is possible to achieve), assumptions about the linearity of technological discovery (even different human societies explored different paths of expertise), assumption about the incremental nature of scientific discovery (omitting that even humans forgot some of their own discoveries), assumptions about the philosophy of other civilizations (discovering implies a cultural will to discover that was/is not even present in all human societies), assumptions about the needs of other civilizations (that's partly philosophical, but you can imagine civilization reaching a state of self perceived perfection that does not involve activities that we can notice), etc, etc, etc.

So really that article that tries to use a string of 1% as if it was some kind of conservative estimate for anything is pretty much bullshit. Again 0.00001% of the life forms on earth have a tech tree. And that's really one life form, so it impossible to know with the data we actually have how singular that is (apparently pretty damn singular since it's not a thousand out of several millions, it's 1).

Anyway, as khorum mentioned, the biggest factor is time. Astronomical time scale vs intelligent life time scale. I mean modern human is a ridiculously recent thing and we already managed to wipe out a couple of our intelligent sub-species (though the jury is still out as to what exactly happened I believe), to have periods of cultural and technological shrinkage, and periods where we came dangerously close to end life on the planet (and for all we know we still might be in one of those period). Add the unknown frequency of civilization ending natural disasters and that "sparkling" theory of civilization that appear and disappear too fast in too big a space and timeline to have more than an infinitesimal chance of having one of them able to see another and even dramatically less of a chance for that one to be us, well... that theory seems pretty convincing to me.

Palum · Jun 2, 2015

Of course if you actually read the article it covers those things too but you know, nbd I guess.

gogusrl · Jun 2, 2015

The way I see it we already have the basic technology to start building Von Neumann machines (self replicating 3d printers). Considering the age and size of the universe, "someone else" should have had enough time to get to our technological level and build one of those. They did the math and it would take ~ 1 million years to get a machine on every planetary body in the galaxy. The Universe is 13.7 billion years ...

Brad2770 · Jun 2, 2015

Plus, we could be the first for the universe. There has to be one and it could very well be us.

Chanur · Jun 2, 2015

Abefroman_sl said:
I must be the only person who thinks the grown up forum is pathetic. A bunch of people constantly laughing at people needing a safe space have their own safe space.

I agree. The special moderation rules are also silly there.

Szlia · Jun 2, 2015

Palum_sl said:
Of course if you actually read the article it covers those things too but you know, nbd I guess.

Some things in the article are tangentially related but none are addressed in the same context. For instance the time scale problem is only addressed in the context of a thousand Type II and Type III civilizations existing in our galaxy (estimation reached by the absurd chain of 1% conservative estimates), but us being here for too short a while to have encountered them (though Sagan is quoted with another time related problem that does not lack charm: other civilizations might have a totally different relashionship with time - 12 years to say hello is the example).

Tuco · Jun 2, 2015

Szlia, what point are you making here?

Szlia · Jun 2, 2015

My points are that the article is not very good, that the Fermi paradox does not feel very paradoxical to me and that my speculations as to why are not covered by said article and that many of the speculations listed by the article use a number of poor assumptions.

Agraza · Jun 2, 2015

I didn't read the article, but why do we assume anything we're receiving would even make sense across the distance? There could be another civilization doing exactly what we're doing, but by the time our messages intersect with each others' respective detection apparatus they're indistinguishable from random noise.

Cad · Jun 2, 2015

Agraza_sl said:
I didn't read the article, but why do we assume anything we're receiving would even make sense across the distance? There could be another civilization doing exactly what we're doing, but by the time our messages intersect with each others' respective detection apparatus they're indistinguishable from random noise.

Why would someone broadcast random noise? There's no reason to think a radio transmission originating 1000 light years away would for some reason be transformed to random noise aside from dopplering and I believe we account for that when doing a sky survey.

Agraza · Jun 2, 2015

Since August 1992, the radio antennas on the spacecraft, called the plasma wave subsystem, have been recording intense low- frequency radio emissions coming from beyond the solar system. For months the source of these radio emissions remained a mystery.

"Our interpretation now is that these radio signals are created as a cloud of electrically charged gas, called a plasma, expands from the sun and interacts with the cold interstellar gas beyond the heliopause," said Dr. Don Gurnett, principal investigator of the Voyager plasma wave subsystem and a professor at the University of Iowa. [see illustration]

The sun is the center of our solar system. The solar wind is a stream of electrically charged particles that flows steadily away from the sun. As the solar wind moves out into space, it creates a magnetized bubble of hot plasma around the sun, called the heliosphere. Eventually, the expanding solar wind encounters the charged particles and magnetic field in the interstellar gas. The boundary created between the solar wind and interstellar gas is the heliopause.

"These radio emissions are probably the most powerful radio source in our solar system," said Gurnett. "We've estimated the total power radiated by the signals to be more than 10 trillion watts. However, these radio signals are at such low frequencies, only 2 to 3 kilohertz, that they can't be detected from Earth."

In May and June 1992, the sun experienced a period of intense solar activity which emitted a cloud of rapidly moving charged particles. When this cloud of plasma arrived at the heliopause, the particles interacted violently with the interstellar plasma and produced the radio emissions, according to Gurnett.

"We've seen the frequency of these radio emissions rise over time. Our assumption that this is the heliopause is based on the fact that there is no other known structure out there that could be causing these signals," Gurnett continued.

Because of the Voyagers' unique positions in space, they serendipitously detected and recorded the radio emissions. "Earth-bound scientists would not know this phenomenon was occurring if it weren't for the Voyager spacecraft," Gurnett added.

http://www-pw.physics.uiowa.edu/plas...r/heliopr.html

That kind of thing wouldn't have any effect? What if there are other larger effects outside the solar system?

Tuco · Jun 2, 2015

Szlia_sl said:
My points are that the article is not very good, that the Fermi paradox does not feel very paradoxical to me and that my speculations as to why are not covered by said article and that many of the speculations listed by the article use a number of poor assumptions.

ok.

Let me restate my assumptions about the paradox and you can point out which ones you feel are bullshit:
1. Once mankind got to the point of starting our tech tree some 6-10 thousand years ago we've advanced dramatically to where we are now.
2. Any pace that keeps up with our current one will have us continuously populating the galaxy in the next million years.
3. There are 100 billion stars in the milky way.
4. Even a very conservative estimation of how unlikely it is for an Earth-level inhabitable planet to exist would still result in many Earth like planets.
5. In a habitable planet, life has a chance of springing up over billions of years.
6. In planet with life, civilization has chance of springing up over billions of years.
7. Once that planet establishes a civilization, it has a chance of colonizing the milky way.
8. We have not seen any life colonizing the milky way, why not?

I think you see the paradox as sort of an impossible to answer question. Where as the article (and I) view it is a question with a long list of plausible answers.

The Astronomy Thread

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