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The Fermi paradox revisited: Technosignatures and the contact era

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Re: The Fermi paradox revisited: Technosignatures and the contact era

#321

Post by heavenlyblue »

thereddaikon wrote: post #158
btilly wrote: post #114

Earlier quoted context omitted.

Von Neumann pointed out that an advanced civilization, with technology that we can predict should be developable, can colonize the entire galaxy in roughly 10 million years. Which is a blink of time by geological standards.

Von Neumann was much smarter than I but for such a calculation you have to make so many assumptions as to make it worthless. How can we possibly be able to predict what happens to a civilization in 10 million years? And yes I am aware of Von Neumann probes. But as someone else pointed out there may be secondary effects we aren't even aware of.

> How can we possibly be able to predict what happens to a civilization in 10 million years?

Obviously under the assumption that no other changes but growth and colonisation happens to that civilisation.

Re: The Fermi paradox revisited: Technosignatures and the contact era

#322

Post by lapcat »

dromenkoning wrote: post #320
lapcat wrote: post #246

Earlier quoted context omitted.

> Perhaps you're not the person that should be explaining to everyone what is painfully obvious and what is not then. You didn't even understand my comment. I meant it's painfully obvious to me. It should have been obvious that I didn't mean it was obvious to everyone, but obviously some people can't see the obvious. I could write a long essay on why we're not on the verge of expanding beyond our home planet, but I f…

> I could write a long essay on why we're not on the verge of expanding beyond our home planet The reason that essay would be long is because you'd have to explain away so much progress from multiple independently operating space industries.

"progress"

We have a handful of humans living temporarily in Earth orbit. We have precisely zero humans living permanently off planet. That's not much progress toward a self-sustaining space colony millions of miles away in an extremely hostile environment.

We don't even know whether the human body can survive long term in the much lower gravity of Mars. Life on Earth didn't evolve for that. The whole idea could be doomed from the start.

Launching rockets is the "easy" part. That's not progress. The hard part is living in space.

Not to mention, even if we could live in space, we're going to bring our own nasty instincts along with us to any other planet. The instincts that are causing us to destroy our ecosystem here and fight amongst each other. If we can't live on Earth with peace, harmony, and sustainability, in an environment that was practically made for us, then what makes you think we can live in another environment that's totally hostile to all life? We'd be sending a clown car to Mars.

In general, we have too many people filled with visions they've got from science fiction, and not enough of a dose of science fact. Perhaps the most realistic bit from science fiction is the part of "Contact" where they're debating whether to send a Christian or an Atheist on the mission. Then extremists blew it up anyway. That's our human reality.

Re: The Fermi paradox revisited: Technosignatures and the contact era

#323

Post by actionfromafar »

DesiLurker wrote: post #277
AnimalMuppet wrote: post #85

Earlier quoted context omitted.

How far away do you think such a thing could be detected? Say someone set off a 100 megaton nuke in space within the Centauri star system. Could we detect it?

its inverse square falloff for radio energy dissipation so I'd say it goes away really really quickly. also you have the problem of overcoming Sun's 'blaring' background signal unless you took your signal generator and placed it outside of oort cloud or further.

Another idea is to put a mylar parabolic mirror behind the bombs. A very short burst of light is going to get focused in a beam before the mylar is vapourised. Maybe someone smart here could calculate exactly how short the beam would be.

That short burst could be in itself a significant signature. What, in nature, could produce such a short concentrated energy burst?

Re: The Fermi paradox revisited: Technosignatures and the contact era

#324

Post by harriet1 »

DesiLurker wrote: post #277
AnimalMuppet wrote: post #85

Earlier quoted context omitted.

How far away do you think such a thing could be detected? Say someone set off a 100 megaton nuke in space within the Centauri star system. Could we detect it?

its inverse square falloff for radio energy dissipation so I'd say it goes away really really quickly. also you have the problem of overcoming Sun's 'blaring' background signal unless you took your signal generator and placed it outside of oort cloud or further.

[dead]

Re: The Fermi paradox revisited: Technosignatures and the contact era

#325

Post by credit_guy »

dredmorbius wrote: post #299
credit_guy wrote: post #290

Earlier quoted context omitted.

Here's an amusing thing. Even if they were within Jupiter's orbit and decelerating and pointing straight at us, we wouldn't be able to detect them. Nuclear bombs produce a fireball here on Earth. In the first microsecond when the explosion actually happens, they produce gamma rays and X rays. The atmosphere is opaque to those rays, which is to say, it absorbs them. Their energy is enormous, so the part of the atmosph…

Rocket propulsion benefits from directional discharge. Project Orion lead to the investigation prospects for nuclear shaped charges , in which the blast is highly directional. The concept was developed further in the colourfully-named "Casaba-Howitzer": https://en.wikipedia.org/wiki/Casaba-Howitzer > Odds are reasonably good that any space-faring civilisation would create similarly directional reaction devices for sp…

Cool link about the Casaba howitzer. Thank you.

Re: The Fermi paradox revisited: Technosignatures and the contact era

#326

Post by twawaaay »

Valgrim wrote: post #284
twawaaay wrote: post #165

Earlier quoted context omitted.

What kind of argument is this "only if they are in our own solar system"? Even at the speed of Voyager 2, (15km/s), in a billion years it would cover about 4 * 10^17 km or about 40 thousand light years. I am pretty sure people who have been developing for hundreds of millions of years can do better than that, by orders of magnitude. Also you put a totally strange assumption that all civilisations will only restrict t…

If the dark forest hypothesis is true, you can bet any civilization advanced enough to detect us will go out of their way to avoid being detected by us. For all we know, there could be a gigantic tungsten rod slowly and purposefully accelerating toward us that would destroy all life on earth in ten thousand years, and we'd have no way of knowing.

I am not sure about usefulness of kinetic impactors at near light speeds over long distances.

Imagine you are in impactor frame of reference -- any particle of dust it meets will cause tremendous damage to it regardless of what the impactor is built of (assuming our existing technology).

It is in my opinion very likely that over long distances the impactor will just get converted to a shower of high energy particles over very large area.

Re: The Fermi paradox revisited: Technosignatures and the contact era

#327

Post by zshrdlu »

booleandilemma wrote: post #229

It always amazes me that right now, as I type this comment, there could be countless intelligent civilizations out there with their own histories, philosophies, science, literature, etc. All asking themselves the same thing: "are we alone?".

As Carl Sagan noted, the opposite is equally amazing. Are we really all alone? Such a waste of space-time ;)

Re: The Fermi paradox revisited: Technosignatures and the contact era

#328

Post by shireboy »

withinboredom wrote: post #319
jjoonathan wrote: post #304

Earlier quoted context omitted.

> A pissed off colony in the asteroid belt can sling asteroids at the home planet If planets become indefensible then people simply won't colonize them. Problem solved. They'll stay in artificial habitats, and I would expect this to accelerate the colonization of the galaxy, if anything, because then they wouldn't need to wait for a planet to fill up before sending out the next generation of colony ships, they would…

> If planets become indefensible Planets are indefensible, as is most of space if your orbit is predictable. All you need is a body bigger than your margin of computational error, and reaction mass. > exponential growth My point is that in order for civilization to be multi-starred, they'd need to communicate. Once a new star is colonized, due to the constraint on light speed, they become two separate civilizations.…

I really like this thread. Both make good points. I still land on space being really big and really hard. Maybe so much so that multi-stellar civilization is next to impossible and multi-galactic moreso.

If you think resources are scarce on Kepler-452b, wait til you see how bad things on the Space Mormon ship. Especially since it’s 60% harder to exit the gravity well than it would be on our destination at Sol-3. We used all our lift capabilities just to get the basics to orbit. Once we get out there, it’s 1400 light years away, so will take us 5600 years to get to Sol assuming we can get the drives going full speed and still retain enough delta-v to brake in Sol orbit. If not, it may even take longer or worse - we zoom by as a blip at the edge of the system. The good news is our telescopes are pretty sure it’s habitable, but we don’t hear any techno signatures. So with any luck we arrive in 6000 years and have enough gametes in storage for the incubators to build a viable colony from. I just hope the kids behave once they get there.

Re: The Fermi paradox revisited: Technosignatures and the contact era

#329

Post by vardump »

vardump wrote: post #295
twawaaay wrote: post #165

Earlier quoted context omitted.

What kind of argument is this "only if they are in our own solar system"? Even at the speed of Voyager 2, (15km/s), in a billion years it would cover about 4 * 10^17 km or about 40 thousand light years. I am pretty sure people who have been developing for hundreds of millions of years can do better than that, by orders of magnitude. Also you put a totally strange assumption that all civilisations will only restrict t…

Stars move relative to each other. You won't need much higher speeds than what we can already achieve, as long as you're willing to wait for another star to move nearby.

Stars don't have same velocities:

https://en.wikipedia.org/wiki/Stellar_kinematics

Gliese 710 is probably going to cross Oort cloud in 1.29M years. Perhaps we should wait and hop to this star?

https://en.wikipedia.org/wiki/Gliese_710#Computing_and_detai...

Re: The Fermi paradox revisited: Technosignatures and the contact era

#330

Post by denton-scratch »

actionfromafar wrote: post #285
denton-scratch wrote: post #265

Earlier quoted context omitted.

> so maybe it is a sequence At that point, you introduce the assumption that the interval is quantized. Up until then, you're dealing with an arbitrary period of time, which is a real, and can't be made into sequences. Once you have sequences you have integers, and so you can have primes. But you can't just switch from reals to countable numbers without explanation, and then say that two reals can be relatively prime…

So begin with a sequence of 1 1 1 1 1 1 1 1 1 1. That establishes a baseline cadence of minutes, or hours or whatever. A clock signal if you will. Then switch to primes. I think anyone looking at that kind of message will figure it out eventually. It can't be mistaken for a natural occurence.

> So begin with a sequence

That is the trick that I was calling out. The intervals are reals, and cannot be made into a sequence. Beginning with a sequence is even worse; what is in evidence (for the aliens) is a set of real intervals. That's what the aliens have to begin with.

Now explain how they get to primes.

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