Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

The Fermi Paradox

waitbutwhy.com

Post reply on HN
Print view View original

71–80 of 168 posts

Re: The Fermi Paradox

#71

Post by dennisgorelik »

XorNot wrote: post #39
nhaehnle wrote: post #29

Earlier quoted context omitted.

I often wonder this as well. The speed of light isn't really a physical limit to expansion - generation ships are theoretically possible. It may just be that the Great Filter takes the form of relatively benign[1] economic and/or sociological obstacles. At least, if you take a diff between typical beliefs at the time the Fermi Paradox was formulated vs. typical beliefs now, I would say the experience of the shutting…

If you consider the declining birth rates of modern nations as the standard of living goes up, then it stands to reason that once a civilization reaches the point where it might be able to engage in large scale space exploration, the population that can do so has become relatively stable. So you simply never (or rarely) get exponential cosmic expansion. There might be a few billions of that race roaming the stars, bu…

Evolution takes care of that obstacle: whatever individuals keep replicate themselves - win, and keep pushing expansion forward.

Re: The Fermi Paradox

#72

Post by thelollies »

Another possibility... there are plenty of civilisations within broadcasting distance from us that are all listening but not broadcasting for fear of predatory civilisations.

Re: The Fermi Paradox

#73

Post by danieltillett »

bdamm wrote: post #30
maaku wrote: post #10

The "we are the first" argument seemed less convincing than it could have been. A better argument from that perspective is the observation that Type III civilizations expand at an alarming rate. Whatever the motivation for expansion[1], basic simulations and back of the envelope calculations show that even with technology we could imagine building in the not so distant future, humans could expand into the cosmos at >…

This model assumes that interstellar travel is profitable. There is no evidence that this is the case, even if we had Star Trek technology. If it isn't profitable, then it turns into a drain on the home planet. That isn't sustainable.

Profitability is not an explanation for many activities that take place here on Earth (today is one). There are many reasons that would allow non-profitable expansion to occur. If the cost is low compared to the wealth of the society and the society is not a hive mind, then some individuals within that society would undertake it purely for non-profit reasons. For example, if I could send a problem to Sirius for $1000 that would beam back pictures of system in 18 years time I would do it right now even though I am not going to make any money from the exercise.

If we want to stay on the profit driven model only then it could still be profitable to send out colonising entities once the solar systems resources are fully utilised. Remote colonies could stream back computational information (say Pixar's Toy Story 42) thus increasing our wealth.

Re: The Fermi Paradox

#74

Post by danieltillett »

dennisgorelik wrote: post #70
danieltillett wrote: post #67

Earlier quoted context omitted.

We can't calculate the probability of life arising though because even if we did know how it arose here—which we don't exactly—we don't know all the possible different ways it can arise, which may or may not also be a number raised to a large power. We can't, but we can assume that any process that arises from a series of unlikely chained events (where the likelihood of each event are not correlated) will most likely…

Why do you think that current CO2 concentration levels are important for intelligent life? Slight adjustment in how body works can easily adapt organism to new CO2 levels.

I did explain it in my post, but maybe it was too short. Earth has been kept in the habitable temperature zone over the last 3.5 billion years through falling CO2 levels. Around 3.5 billion years ago the sun provided ~25% less energy than now and the CO2 levels were much higher. This is the green house effect. As the sun got brighter over time the level of CO2 in the atmosphere has fallen. For more on this see the slow carbon cycle [1].

The problem is that the level of CO2 in the atmosphere is getting very low (~0.2%). At this level plants are starved for CO2 - if it gets down to 0.01% then plants can't grow at all and the ecosystem needed to support the evolution of intelligent life would collapse.

1. http://earthobservatory.nasa.gov/Features/CarbonCycle/page2....

Re: The Fermi Paradox

#75

Post by ericb »

Pxtl wrote: post #16
ccvannorman wrote: post #4

i love this puzzle. here are some theories: 1. simulation argument 2. civilizations have a high or inevitable chance to self destruct after 3. civilizations transcend our observable universe after 4. due to the single observer problem, humans fail to grok some very important feature of larger scale space that prevents detection/increases isolation [1] http://accelerating.org/articles/transcensionhypothesis.html

4 seems likeliest. Interstellar colonization is simply impossible because of the vastness of the distance that must be covered. It requires more energy than can be summoned to get a useful amount of hardware across multiple lightyears.

At a certain point, if you can make a self-replicating machine, with harvested solar energy for travel, you would expect that machine's descendants to slowly get everywhere intended.

Re: The Fermi Paradox

#78

Post by quotemstr »

darkmighty wrote: post #54
maaku wrote: post #10

The "we are the first" argument seemed less convincing than it could have been. A better argument from that perspective is the observation that Type III civilizations expand at an alarming rate. Whatever the motivation for expansion[1], basic simulations and back of the envelope calculations show that even with technology we could imagine building in the not so distant future, humans could expand into the cosmos at >…

But the Milky Way is only 50,000 light years in radius (~ average distance between stars?). That's not much at all on a evolutionary scale. So your argument explains why we're not currently observing an alien civilization (i.e. they would expand so close to light speed we would likely either be conquered or observing nothing -- so observing nothing is a consistent scenario). But it does not explain why no Type III ci…

The OP's post rests on the Anthropic Principle. Essentially, we don't see evidence of a Type III civilization because anyone who dies is very quickly thereafter consumed by that civilization as it expands across the observable universe. It's a terrifying idea.

Re: The Fermi Paradox

#79

Post by handojin »

sgt101 wrote: post #38
DavidSJ wrote: post #27

Earlier quoted context omitted.

I had this idea recently myself and to the best of my knowledge you're the only other person who's mentioned it. The closest I've found is the "galactic preemption" hypothesis published in the 80's, but that's more an explanation for why only one civilization would exist in a single galaxy, rather than for why a newborn civilization such as our own would look at the sky and see no signs of civilization in the whole u…

I've read a novel that featured this, I am wracking my brains to remember the title/author. It featured a generation ship that switched to a .com mode as it approached the star to be colonized and a race of bat people who were the putative colonization targets. I am not making this up, but I may have dreamt it!

Nope. Ken MacLeod's 'learning the world'. The alien space bats were a nice touch. Charles Stross' book accelerando has an interesting take on the Fermi paradox too.

Re: The Fermi Paradox

#80

Post by danieltillett »

_greim_ wrote: post #41
gpsx wrote: post #32

Earlier quoted context omitted.

That is a good point. I agree with you. And people do have suggestions as to how life can be more probable than naively expected. But this answers the question why there is life at all as opposed to why we don't see more of it. My bias is that life is highly improbable and that we will not find any other life in our universe. But I also think it is no miracle that we exist, as I will describe. Given that I am trying…

The WAP accounts for high improbability by positing a multiverse, but (at least as I understand it) it doesn't predict high improbability, even if there is a multiverse. Also, in a multiverse scenario, the improbable thing might not be the formation of life, but the fine-tuning of the laws of physics which allows the formation of life. In which case life might be relatively common.

Also, in a multiverse scenario, the improbable thing might not be the formation of life, but the fine-tuning of the laws of physics which allows the formation of life. In which case life might be relatively common.

If we assume that this tuning is not an all or nothing event then the larger the possible universe size the more likely it is that we lie within an region where the features are tuned just enough to let one intelligent life form arise.

You can think of the tuned conditions that allow life to be common to be a bullseye that is surrounded by tunings that are close enough to allow life to occur infrequently. If you were to pick a region at random out of the regions that contain intelligent life then it is likely that you would pick one of the surrounding regions not the bullseye. This is also an explanation for Fermi's paradox.

Post reply on HN