The Astronomy Thread

Yep. Anyways I'm more or less pro-Martian colonies myself but it's UNDOUBTEDLY more immediately useful to build telescopes/observatories on the Moon.

Even the tiny telescope the Apollo landings put on the moon enriched human knowledge, confirming a couple theories about nebulas and the earth's atmosphere etc. A full-scale lunar observatory woud also be a great place for a LIGO-type gravity observatory since the moon is tectonically dormant and there aren't trucks or assholes rumbling around.

khorum said:

What could possiby be unreasonabe about the Drake Equation? It's about as straightforward as you could get:

Given that, Enrico Fermi posited that since the Drake Equation shows the likelihood alien civilizations to be extremely high, how come we haven't listened artificial radio transmissions or Dyson swarms or chemical contrails or __ANY__ sign of these alien civilizations. That's all the Fermi Paradox purports to be.

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Its the detection part. Not sure we have a good idea about what it'd really take to be able to detect radio signals at this distance. When we try to run fourier analysis on radio signals from an interstellar body, at this distance and considering how power drops at a rate of 1/d^2, are the detectors we are trying to use really big enough to detect the frequencies? Or do you get mega aliasing to the point where you don't really see anything? Put another way, the photon density of a wave front decreases the further it gets from its source. When we're light years away from a low-powered artificial source, the photon density we can see is going to be pretty damn small by the time it reaches us. I'd think you'd need an enormous radio telescope (maybe magnitudes bigger than something like Arecibo etc.) to be able to receive enough photons per second from the alien radio source to be able to properly perform the fourier analysis. I'm not saying we couldn't detect signals from some closer systems now, just saying there is some distance at which we could no longer recover signals given the size of the current dishes we are using to search.

I've never spent much time looking at the details of this, but just a minute of googling brought up at least one researcher that apparently has and thinks alien signals could only reach a small portion of the galaxy:

We still haven’t heard from aliens - here’s why we might never

Pharazon2 said:

Its the detection part. Not sure we have a good idea about what it'd really take to be able to detect radio signals at this distance. When we try to run fourier analysis on radio signals from an interstellar body, at this distance and considering how power drops at a rate of 1/d^2, are the detectors we are trying to use really big enough to detect the frequencies? Or do you get mega aliasing to the point where you don't really see anything? Put another way, the photon density of a wave front decreases the further it gets from its source. When we're light years away from a low-powered artificial source, the photon density we can see is going to be pretty damn small by the time it reaches us. I'd think you'd need an enormous radio telescope (maybe magnitudes bigger than something like Arecibo etc.) to be able to receive enough photons per second from the alien radio source to be able to properly perform the fourier analysis. I'm not saying we couldn't detect signals from some closer systems now, just saying there is some distance at which we could no longer recover signals given the size of the current dishes we are using to search.

I've never spent much time looking at the details of this, but just a minute of googling brought up at least one researcher that apparently has and thinks alien signals could only reach a small portion of the galaxy:

We still haven’t heard from aliens - here’s why we might never

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That's literally factored into the Drake Equation, dude. Its notation is L. It's the last variable in the equation and arguably the most important for SETI, the window of time wherein a sufficiently advanced civilization would transmit signals strong enough to propagate past its star's plasma bow shock.

Michael Shermer figures L at around 302-400ish years:


David Grinspoon argues that L might end up in the billions of years since the signals would degrade as noise but may still have enough energy to be detectable by sufficiently advanced civilizations:

khorum said:

That's literally factored into the Drake Equation, dude. Its notation is L. It's the last variable in the equation and arguably the most important for SETI, the window of time wherein a sufficiently advanced civilization would transmit signals strong enough to propagate past its star's plasma bow shock.

Michael Shermer figures L at around 302-400ish years:

Why ET Hasn't Called

The lifetime of civilizations in the Drake equation for estimating extraterrestrial intelligences is greatly exaggerated

www.scientificamerican.com

David Grinspoon argues that L might end up in the billions of years since the signals would degrade as noise but may still have enough energy to be detectable by sufficiently advanced civilizations:

. . : : Lonely Planets : David Grinspoon : : . .

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Pharazon2 is talking about the size of the antenna we need to pick up the signals from from faraway reaches of our galaxy, measured in kilometers. The L term you're talking about is a measurement of time, the units are years. Are you retarded?

Edit: Inverse-square law - Wikipedia etc

Melvin said:

Pharazon2 is talking about signal power output of the transmitters sending signals from faraway reaches of our galaxy, measured in watts. The L term you're talking about is a measurement of time, the units are years. Are you fucking retarded?

Edit: Inverse-square law - Wikipedia etc

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No, you fucking mongoloid, we were talking about his objection to the Drake Equation's role in the Great Filter Hypothesis and he proposed signal degradation over time as something that Drake had overlooked.

Except signals propagation---not just RADIO but heat and infrared signatures from cities all the way to ambient heat from occluded/Matrioshka-encased stars or potential Shkadov engines---have been factored into the Drake Equation since the 60's. And those limitations in OUR signal technology he's suggested have been proposed factors in the equation for years---all it would do is move the needle around from a 400-year window to the 50,000-year window that SETI itself uses. Like Michael Shermer said an advanced civilization wouldn't necessarily need to transmit radio or infrared deliberately but as a consequence of mass industrialization over time.

You could've avoided outing yourself as the fucking retard you are by just following a couple pages' worth of posts.

khorum said:

No, you fucking mongoloid, we were talking about his objection to the Drake Equation's role in the Great Filter Hypothesis and he proposed signal degradation over time as something that Drake had overlooked.

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You're incorrect right off the bat. He's talking about signal degradation over distance, not over time. The time element of the Drake equation is entirely a measurement of the duration of the source of the signal. Maybe you're mistaking the duration that it spends traveling as if that were relevant at all. It's not.

Once you hit control of your physical evolution space empires just may no longer be desirable.

It doesn't even have to be virtual realities of anything like that. If we evolve a branch of ourselves to thrive in the environ!ent of a gas giant, which give us 1000 years and that may not be absurd, then what use is an oniel cylinder.

I think the answer to Fermi is that there is a societal homeostasis. An organism only grows so large. A collection of organisms must be self limiting as well for some reason that goes deeper than environmental pressure.

That might be a great filter. Not sure.

Melvin said:

You're incorrect right off the bat. He's talking about signal degradation over distance, not over time. The time element of the Drake equation is entirely a measurement of the duration of the source of the signal. Maybe you're mistaking the duration that it spends traveling as if that were relevant at all. It's not.

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No dumbfuck, noone was having that argument at all.

Drake uses L simply to factor in the emissions footprint of a theoretical civilization, measured in how long they're emitting them. It doesn't imply how that signal is carried over radio or as the ambient heat of a dyson sphere or whatever, it's just there to ACCOUNT for the period during which any given civilization would be actively emitting signs of activity.

Michael Shermer used L as the total lifetime a civilization's activity might be observable as heat. Carl Sagan used the total time a civilization was capable of electrical industry via nuclear energy. David Grinspoon suggests that as civilizations transcend radio, a compound variable should be used alongside L. Whatever, L was just an abstract notation of a civilization's capacity to emit observable activity.

The point is it has been factored into the Drake equation from the very beginning and if you wanted to account for the degree to which our signals degrade way shorter than our 200-year lightcone, that's been done by someone at some point. You could argue against SETI's figure of a 50,000 year window in which a typical civilization may be active (which Shermer strenuously argues against) or you could plug in Bostrom's or Grinspoon's or you can jerk yourself off trying to work L down to a figure that reflects our radio activity---that was never the point.

iannis said:

That might be a great filter. Not sure.

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The Great Filter is just some cataclysmic condition all life across the universe succumbs to long before they can rise to the higher rungs on the Kardashev scale. Nuclear War, Climate Collapse whatever.

An example would be:

iannis said:

I think the answer to Fermi is that there is a societal homeostasis. An organism only grows so large. A collection of organisms must be self limiting as well for some reason that goes deeper than environmental pressure.

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That's close to the Malthusian dead end that's my particular favorite.

It's just one of the suggested answers to the Fermi Paradox. The Simulation Hypothesis, the Zoo Hypothesis, Matrioshka worlds and heat-neutral Dyson Spheres have been others.

khorum said:

No dumbfuck, noone was having that argument at all.

Drake uses L simply to factor in the emissions footprint of a theoretical civilization, measured in how long they're emitting them. It doesn't imply how that signal is carried over radio or as the ambient heat of a dyson sphere or whatever, it's just there to ACCOUNT for the period during which any given civilization would be actively emitting signs of activity.

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Melvin is right, I was talking about signal degradation, which I thought i was pretty clear about. I'm not talking about L in the Drake equation at all, only you are. I'm saying even if photons from a radio signal emanating from an alien planet are hitting earth right now, there's some range at which we wouldn't be able to discern them because you won't be able to receive enough photons from it within the needed amount of time. Its not accounted for in the Drake equation at all.

Why would aliens contact earthlings? Once you consider vast amount of time as well a distance involved. The odds of a star trek type scenario are so very limited as to be virtually nonexistent. Odds would be a very advanced alien civilization wouldn't wish to talk to humans. One because were so primitive that any exchange between to cultures would be deemed as nonproductive for the aliens. Second is they would be aware of the impact that revealing themselves will have on a primitive species. They will anticipate a mad dash for any species to catch up to them in possibly a reckless fashion. That will be something they will be well prepared to deal with as a matter of course. We on the otherhand can barely deal with the amount of change that exists naturally. The fear induced mad scramble to catch up to some alien empire that maybe 1000 to 1000000 year ahead of us may prove fatal to us as species though.

All of this will be simulated on computers that will predict outcomes basically perfectly. In fact I would say that those computers have already predicted what outcome would be and that is why we haven't seen any aliens.

Pharazon2 said:

Melvin is right, I was talking about signal degradation, which I thought i was pretty clear about. I'm not talking about L in the Drake equation at all, only you are. I'm saying even if photons from a radio signal emanating from an alien planet are hitting earth right now, there's some range at which we wouldn't be able to discern them because you won't be able to receive enough photons from it within the needed amount of time. Its not accounted for in the Drake equation at all.

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Melvin is a fucking retard who tried to be a badass without reading the conversation he parachuted into and you're the dumbass who foisted the signal propagation argument without realizing that the Drake equation accounted for it back in 1961.

Drake uses L to abstract the period during which a civilization's observable presence is active throughout its lifetime. SETI puts it around 50,000 years, Carl Sagan reckoned the time from the start a civilization is able to muster nuclear energy, Michael Shermer considers heat signatures from pre-industrial urbanization etc. It accounts for the totality of an advanced civilization, INCLUDING signal degradation, whether that's IR or radio or ambient temperature around a civilization's star, space farts, whatever---ALL OF THOSE, including the stochastic sigma fading of radio signals---can and have been factored in.

The reason SETI gives the value of 50,000 of L is because of Nikolai Kardashev's assessment that any successful civilization would follow similar macro-scale behaviors constrained by the laws of thermodynamics and conservation of energy and momentum---IE: that even if ___ONE___ successful spacefaring civilization exists, they would be compelled by expanding requirements for matter and energy to capture suns and eventually entire galaxies. Michio Kaku mathed it out that Humanity would hit Kardashev-2 in about 50,000 years or so and that's what they stuck with.


So it's not about whether or not radio transmissions lose power a little past a star's heliopause or that you can detect Dyson spheres by their gravitic pull or your argument that "photons" may have faded before we could detect them. Drake accounts for all that.

So the Fermi Paradox isn't merely about ancient radio transmissions' last feeble waves, it's about why we don't see encased galaxies or the gravity dimples of Dyson swarms or the gas contrails of star-powered Shkadov engines cruising across the galaxy.

khorum said:

Perchlorates on Mars also makes cultivation of the soil near impossible in the near term and prohitively expensive on the long term. In fact, the perchlorate saturation in Martian soil (1,400 times higher than the maximum concentration survivable by all terrestrial agriculture) is more expensive in terms of human habitation on the long term than the immense costs of radiation shielding a habitat would require due to Mars' lack of a magnetosphere.

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Perchlorates aside (I don't know that this is a problem EVERYWHERE on mars), the radiation problem on mars is going to be a lot less than on the moon, mars being farther from the sun reducing such.

khorum said:

So the Fermi Paradox isn't merely about ancient radio transmissions' last feeble waves, it's about why we don't see encased galaxies or the gravity dimples of Dyson swarms or the gas contrails of star-powered Shkadov engines cruising across the galaxy

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It also makes assumptions that Dyson Spheres/Shkadov engines are a natural progression of technology for a highly advanced civilization, which is honestly kind of arrogant (and in turn, a hallmark of humanity lol). We make future tech speculations based on what we know at the time we speculate. If a technology/component of physics/some exotic material is unknown to us, and we can't even speculate about it, then we stick to the known. If there is no unobtanium that we are aware of, then we think of creative applications of materials we do know about.

Plus it makes the assumption we are advanced enough to detect these things (or radiowaves that have dissipated/degraded to such a degree that they basically are just more bits of static in the cacophony of cosmic noise). History is littered with great and educated minds that dialed the arrogance up to 11 and made the assumption they were at peak knowledge/technology and in theory if something existed/something was possible, it would already be something they could do or something they could have figured out how to obtain evidence for.

That is part of the flaw of Fermi/Great Filter. It makes the assumption that we -should- be able to detect these things right now.

Siddar said:

Why would aliens contact earthlings? Once you consider vast amount of time as well a distance involved. The odds of a star trek type scenario are so very limited as to be virtually nonexistent. Odds would be a very advanced alien civilization wouldn't wish to talk to humans. One because were so primitive that any exchange between to cultures would be deemed as nonproductive for the aliens. Second is they would be aware of the impact that revealing themselves will have on a primitive species. They will anticipate a mad dash for any species to catch up to them in possibly a reckless fashion. That will be something they will be well prepared to deal with as a matter of course. We on the otherhand can barely deal with the amount of change that exists naturally. The fear induced mad scramble to catch up to some alien empire that maybe 1000 to 1000000 year ahead of us may prove fatal to us as species though.

All of this will be simulated on computers that will predict outcomes basically perfectly. In fact I would say that those computers have already predicted what outcome would be and that is why we haven't seen any aliens.

Click to expand...

Can't think like a human. Can't think logically. You have to forget current laws of the universe. A civilization so advanced they might exist anywhere/anytime in an instant. They might visit us because we have the last known source of peanut butter, and they hate we have bellybuttons.