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

A Lonely Universe

inference-review.com

Post reply on HN
Print view View original

171–180 of 210 posts

Re: A Lonely Universe

#171

Post by lariati »

TheOtherHobbes wrote: post #38
mongol wrote: post #6

Earlier quoted context omitted.

Is it not possible that colonizing a galaxy is simply too hard, no matter what intelligence?

Or it's so easy. Ants live in cities surrounded by humans, but have no idea what a human is or what humans do, and literally cannot experience - never mind imagine - what a human is, what a city is, what transport networks are, what culture is, what technology is. Every so often an ant nest is destroyed because it's an irritant, but if the ants notice at all they carry on relatively unthinkingly. There are only other…

Or a combination of both. Ants are a great example though. Like 10 million ants per person on Earth and they are almost all invisible to humans.

I would think there is quite a bit of intelligent life in the universe that all feels equally alone.

Space constraints * time constraints make this a near insurmountable problem and then even if that is overcome then it gets multiplied again by the minuscule probability with sharing anything close to perception like the ants.

Not to mention we are going to be orders of magnitude closer to ants in perception than to aliens from a different planet.

Re: A Lonely Universe

#172

Post by citizenpaul »

me_me_me wrote: post #144
hoseja wrote: post #78

Earlier quoted context omitted.

Why? What will thousand years of delayed seeding do? It's very dumb to smear our poop onto other planets before we thoroughly investigate them.

> It's very dumb to smear our poop onto other planets That is very clever way of putting it, looking at the state of our planet its 100% correct analogy. Thank you for making me chuckle.

So we should just leave other planets as lifeless husks? The self loathing you are experiancing must be miserable.

Re: A Lonely Universe

#173

Post by ncmncm »

GoblinSlayer wrote: post #156
brabel wrote: post #85

Earlier quoted context omitted.

I think we are in a relatively safe corner of the galaxy though... IIRC there's no cosmical existential threat we know of within the next billion years or so, and the kind of cataclism you're talking about would be the kind of thing we should already be able to predict millions of years in advance.

We are in the galactic habitable zone.

There is no such thing as a "galactic habitable zone" defined or meaningful.

There is a an obviously uninhabitable zone close to the core black hole, and uncountable similar zones elsewhere, but Sol could move into one of the latter at any time. And, distant events could wipe us out, anyplace else, with decreasing probability as the density of other stars in the immediate neighborhood decreases.

All we can say is that we have not entered any uninhabitable zones in the last billion years or so, i.e. five orbits, and not been blasted too badly from a distance, likewise. Milder events could wipe out everything but deep-sea microbes, which at this late date might not leave time to evolve intelligent life again.

Lots of galaxies have heavy star-forming going on in the rim, with increased risk of supernovas. I don't know if we know whether ours is among those. (I doubt we can tell. Such regions are identified by high UV flux, but UV is blocked by dust, which is plentiful.) But otherwise, farther from the core is generally safer.

Re: A Lonely Universe

#174

Post by ncmncm »

jeremyjh wrote: post #128
Thiez wrote: post #121

Earlier quoted context omitted.

And what exactly would our hypothetical descendents do there, in the middle of nowhere with no star, no planets, and no energy?

There are stars that are far from everything else and off-axis. There are even stars that get ejected from the galaxy all-together.

Yes, one of those last would be a good choice, if we could get to one.

But I don't expect our distant descendants to be dependent on starlight. A nice Kuiper Belt and Oort Cloud are good to stay in for access to building material and fusion fuel, but the most valuable resource, otherwise, will be abundant free cold.

Planets, as such, and sunshine are for the extremest primitives. Nobody advanced would want to be closer to the sun than, say, Neptune.

Re: A Lonely Universe

#175

Post by rewgs »

ncmncm wrote: post #168
rewgs wrote: post #165

Earlier quoted context omitted.

So, even though “100,000 light years” means “it will take 100,000 years to travel this distance at the speed of light,” those traveling won’t experience it as 100,000 years, but rather a much shorter time period? How long would the travelers experience that as? To be clear I’m not talking about “almost light speed,” I’m talking about traveling at exactly the speed of light (ignoring for a moment whether that’s possib…

At exactly the speed of light you would experience no duration at all. But it would take infinite energy to get going that fast, and infinite energy again to stop, and would still take 100,000 years as seen by anybody watching at either end.

Ah got it. Mind-boggling. Thank you!

Re: A Lonely Universe

#176

Post by therealbilly »

Our best bets right now for further exploration are bigger telescopes (even bigger than the WEBB), and trying to intercept laser communication events. I should have mentioned gravity astronomy...that will be huge as well.

Re: A Lonely Universe

#177

Post by WillPostForFood »

omnicognate wrote: post #163
WillPostForFood wrote: post #152

Earlier quoted context omitted.

is absurdly premature. Only relative to our own existence. If the universe is ~14 billion years old, and life was plentiful, you might expect life to have emerged elsewhere hundreds of millions or a few billion years before us. That allows for enough time for signals to have reached earth, even at slow light speeds.

That part was more about us being detected by others, really. The portion of the galaxy within which aliens could theoretically have noticed us since we developed radio technology and responded in a way we could have noticed by now is tiny. As far as us noticing other civilisations is concerned the second point is the major one: the signals involved would just be really, really tiny. The "prematureness" is relative t…

It is plausible that our visible light signature might be reduced (though I don't agree it is necessarily wasteful - like lighting up evening outdoor events). But we should consider the entire RF spectrum. You'd have to go to an extreme to not have a modern civilization without notable RF emissions at some level. (e.g. Dyson sphere).

Section 2 of this paper has some fun info on the ability to detect our radio signature at great distances.

https://arxiv.org/pdf/1207.5540.pdf

For example, the Arecibo Planetary Radar typically transmits at a power of 0.8 MW and a frequency of 2380 MHz, with a gain of ~108. This means that low bandwidth transmissions from Arecibo, with B ~ 0.1 Hz, would be detectable by a watcher with a 1 km2 receiving antenna at distances up to 200,000 light years, while high bandwidth signals, with B ~107 Hz, would be detectable out to about 5 light years by the same watcher.

By comparison, television carrier waves have similar power but gain ~10, B ~ 1 Hz, and frequencies in the range of 100 to 2700 MHz; such signals could be detected with a square kilometer array out to a distance of about 50 light years.

RIP Arecibo

Re: A Lonely Universe

#178

Post by WalterBright »

DrBoring wrote: post #132
WalterBright wrote: post #76

Earlier quoted context omitted.

America has solved the hunger problem. It hasn't ended human discontentment and hostility at all.

I'm ignorant in the matter of food scarcity in USA, but I would say that hunger is far from solved. USA may produce more food than it can consume, but there is still the cost of production and delivery of food. Hunger will still be a thing if food costs more than people can pay. USA may collectively have enough money to buy food for everyone, but the will to spend public money is not there at the current cost of food…

I've never seen anyone in my life in the US showing the symptoms of starvation. I've never heard of anyone starving to death in the US, that was not the fault of some underlying disease, alcoholism, or drug addiction rather than privation.

Having some hunger now and then is actually healthy for people. Fasting for a day or two here and there is a good practice. It also substantially lowers one's food expenses. If you walk down the street, you'll see many people who could use a day off from food :-)

Most of America's food problems are with obesity.

Re: A Lonely Universe

#179

Post by hwc »

rewgs wrote: post #100
Scarblac wrote: post #88

Earlier quoted context omitted.

> Of course the energy requirements are insane and would require some kind of physicists nightmare propulsion system like antimatter rockets. Lose reactor containment and you are instantly converted into plasma and gamma rays. If you hit something the size of a dust particle it will destroy your spacecraft. And, this one spacecraft needs to be able to slow down, have the telescopes and equipment needed to identify ex…

Ha! Funny, I've never considered it even though it's so incredibly obvious: the spacecraft needs to be able to slow down out of light speed. That might honestly be even harder than getting up to light speed, and that of course is almost certainly impossible. Imagine the "runway" you would need. How many lightyears would it take just to slow down? And that's before you even consider how some sort of reverse propulsion…

If you simply assume that your spacecraft uses its own engines to accelerate to cruising speed, then the Δv to decelerate is approximately equal to the Δv to accelerate.

Similarly, if the engines are operated at a constant acceleration, then the distance needed to decelerate is equal to the distance needed to accelerate.

Fuel(/reaction mass), on the other hand, us not equal. The fuel to be used to decelerate must also be accelerated first, meaning more fuel is used to accelerate than to decelerate.

Re: A Lonely Universe

#180

Post by me_me_me »

citizenpaul wrote: post #172
me_me_me wrote: post #144

Earlier quoted context omitted.

> It's very dumb to smear our poop onto other planets That is very clever way of putting it, looking at the state of our planet its 100% correct analogy. Thank you for making me chuckle.

So we should just leave other planets as lifeless husks? The self loathing you are experiancing must be miserable.

> The self loathing you are experiancing must be miserable

This is not reddit mate, cool of and take your personal attacks somewhere else. That and idea of jizzing at every planet you see just because you can sounds awfully indicative of your age.

Post reply on HN