Reply to: UFOs and Aliens corner

[AlfredJPruffock]

No doubt... though if other "civilisations" are much like that on Terra, then they light up briefly in the radio spectrum as radio & tv are invented, then go dark again when it all gets transmitted by optical fibre.

At which point the 'other civllisations' might assume that Earth showed 'too much talent for War' and had , like so many other delveoping civilisations - nuked themselves into oblivion in about 50 years after dicovering how to split the atom .

So then the 'Other Civilsation ' may conclude - no enviornmental issues then with detonating Betelgeuse which has become a growing concern to some of our galactic carrier ships.

[AlfredJPruffock]

Based on that we should have encountered *at least* one extraterestrial civilisation while being advanced enough ourselves to have recognised or recorded it in some way, or to have found evidence for the visit.

Well given that we have been only searching the Universe for a blink of an eye in the Cosmic Scale of Time - and then again its a massive assumption that we have developed the means of recoginizing and identifying such signals - in whatever form they may be - altough when Gamma Rays where first discovered some thought they could be signals from an other LifeForm - which makes you wonder .

For the time being I shall agree to differ with Fermis Paradox for reasons Ive explained I remain unconvicned.

[DaveB]

Aye Dave

... the size of the Universe does have a lot to do with the solution to the Paradox - even taking into account a conservative estimation of the universe you gage ...

Fermis paradox reportedly quipped to fellow physicists in 1950, when discussing why we haven't seen any signs of alien civilisations if, as many believe, our galaxy is teeming with life. Now, a maths model may have an answer to Fermi's paradox.

Rasmus Bjork of the Niels Bohr Institute in Copenhagen, Denmark, has calculated that eight probes - travelling at a tenth of the speed of light and each capable of launching up to eight sub-probes - would take about 100,000 years to explore a region of space containing 40,000 stars. When Bjork scaled up the search to include 260,000 such systems in our galaxy's habitable zone, the probes took almost 10 billion years - three-quarters the age of the universe - to explore just 0.4 per cent of the stars (http://arxiv.org/abs/astro-ph?papernum=0701238).

So, Bjork's answer to the Fermi paradox: aliens haven't contacted us because they haven't had the time to find us yet.

He adds that the search could be optimised by visiting only those stars that harbour habitable planets, which could be identified by planet-finding missions such as NASA's Terrestrial Planet Finder. Bj�rk is also "cautiously optimistic" about listening out for aliens with radio telescopes.

Time Will Tell ....

He also went on to say that increasing the number of initial probes to 200 ( not unreasonable if you are going to do this to begin with ) reduces the time taken to 400m years, or slightly more than a quarter of the age of the universe.

Now assuming that there is only 1 other civilisation out there advanced enough to do this then yes, chances are they will never find us which means for all practical purposes we are indeed alone in the universe.

However if we take the estimated 7*10^22 stars in the visible universe and assume only one in 10m supports a habitable planet capable of sustaining a suitable civilisation we still have 7x10^15 potential sources of exterterestrial contact.

If even only 1 in 10 million of these is ever capable of producing these exploratory probes we have 7x10^8 sources of probes each capable of exploring 0.4% of the universe in 400m years.

To completely explore the universe in this time scale would only require 250 civilisations launching probes. With these above numbers we have 2.8m times as many as, that so it would only take 142 years to explore the entire universe between them.

Based on that we should have encountered *at least* one extraterestrial civilisation while being advanced enough ourselves to have recognised or recorded it in some way, or to have found evidence for the visit.

To date we have found no such evidence.

If they were out there, we would have met them by now.

[AlfredJPruffock]

whs thank goodness. i don't think we aught to want to be found.

Of course there is Pruffocks Paradox - even in the relatively short time frame - they have attmepted to contact us - but we have not yet dveloped the means to receive and de-cypher their transmissions on their Wavelength - yet.

[DS23]

So, Bjork's answer to the Fermi paradox: aliens haven't contacted us because they haven't had the time to find us yet.

whs thank goodness. i don't think we aught to want to be found.

[AlfredJPruffock]

Aye Dave

... the size of the Universe does have a lot to do with the solution to the Paradox - even taking into account a conservative estimation of the universe you gage ...

Fermis paradox reportedly quipped to fellow physicists in 1950, when discussing why we haven't seen any signs of alien civilisations if, as many believe, our galaxy is teeming with life. Now, a maths model may have an answer to Fermi's paradox.

Rasmus Bjork of the Niels Bohr Institute in Copenhagen, Denmark, has calculated that eight probes - travelling at a tenth of the speed of light and each capable of launching up to eight sub-probes - would take about 100,000 years to explore a region of space containing 40,000 stars. When Bjork scaled up the search to include 260,000 such systems in our galaxy's habitable zone, the probes took almost 10 billion years - three-quarters the age of the universe - to explore just 0.4 per cent of the stars (http://arxiv.org/abs/astro-ph?papernum=0701238).

So, Bjork's answer to the Fermi paradox: aliens haven't contacted us because they haven't had the time to find us yet.

He adds that the search could be optimised by visiting only those stars that harbour habitable planets, which could be identified by planet-finding missions such as NASA's Terrestrial Planet Finder. Bj�rk is also "cautiously optimistic" about listening out for aliens with radio telescopes.

Time Will Tell ....

[DaveB]

The apparent size and age of the universe ...

So the whole premise of the Fermi Paradox is based upon the apparent size and age of the Universe.

Well then - how old is (this) Universe and what size is it - I wont go onto to enquire how many universes there are - for now.

From the post above... ( lifted from wikipedia btw, "other sources of information are available." )

...there are an estimated 250 billion (2.5 x 1011) stars in the Milky Way and 70 sextillion (7 x 1022) in the visible universe...

...13.7 billion years of the universe's history...

Even if you think the Universe(s) are bigger and older or more numerous than this it reinforces the argument made by Fermi and others.

[AlfredJPruffock]

The apparent size and age of the universe ...

So the whole premise of the Fermi Paradox is based upon the apparent size and age of the Universe.

Well then - how old is (this) Universe and what size is it - I wont go onto to enquire how many universes there are - for now.

[TimberWolf]

Long lived large fast flying objects (bigger than say a proton) seem to be rare or non-existent in nature. I don't mean distant or galaxy sized objects, which clearly do approach superluminal velocities wrt Earth, I mean we don't see, say, pebble sized objects that have been ejected from distant cosmic events hurtling past us or into the Moon. I wonder if they are slowed down by the instellar medium?

[DaveB]

If they existed, they'd be here by now.

The Fermi paradox is a conflict between an argument of scale and probability and a lack of evidence. A more complete definition could be stated thus:

The apparent size and age of the universe suggests that many technologically advanced extraterrestrial civilizations ought to exist.
However, this hypothesis seems inconsistent with the lack of observational evidence to support it.

The first aspect of the paradox, "the argument by scale", is a function of the raw numbers involved: there are an estimated 250 billion (2.5 x 1011) stars in the Milky Way and 70 sextillion (7 x 1022) in the visible universe. Even if intelligent life occurs on only a minuscule percentage of planets around these stars, there should still be a great number of civilizations extant in the Milky Way galaxy alone. This argument assumes the mediocrity principle, which states that Earth is not special, but merely a typical planet, subject to the same laws, effects, and likely outcomes as any other world.

The second cornerstone of the Fermi paradox is a rejoinder to the argument by scale: given intelligent life's ability to overcome scarcity, and its tendency to colonize new habitats, it seems likely that any advanced civilization would seek out new resources and colonize first their own star system, and then the surrounding star systems. As there is no conclusive or certifiable evidence on Earth or elsewhere in the known universe of other intelligent life after 13.7 billion years of the universe's history, it may be assumed that intelligent life is rare or that our assumptions about the general behavior of intelligent species are flawed.

The Fermi paradox can be asked in two ways.

The first is, "Why are no aliens or their artifacts physically here?"

If interstellar travel is possible, even the "slow" kind nearly within the reach of Earth technology, then it would only take from 5 million to 50 million years to colonize the galaxy. This is a relatively small amount of time on a geological scale, let alone a cosmological one. Since there are many stars older than the sun, or since intelligent life might have evolved earlier elsewhere, the question then becomes why the galaxy has not been colonized already. Even if colonization is impractical or undesirable to all alien civilizations, large scale exploration of the galaxy is still possible; the means of exploration and theoretical probes involved have bee discussed extensively. However, no signs of either colonization or exploration have been generally acknowledged.

The argument above may not hold for the universe as a whole, since travel times may well explain the lack of physical presence on Earth of alien inhabitants of far away galaxies.

However, the question then becomes "Why do we see no signs of intelligent life?"

A sufficiently advanced civilization could potentially be seen over a significant fraction of the size of the observable universe. Even if such civilizations are rare, the scale argument indicates they should exist somewhere at some point during the history of the universe, and since they could be detected from far away over a considerable period of time, many more potential sites for their origin are within our view. However, no incontrovertible signs of such civilizations have been detected.

There are a large number of counter arguments to the Fermi Paradox, none of which completley account for the absence of evidence for extra terrestrail life.

To sum it up, if they existed, they'd be here by now.

Hi ZG

[TimberWolf]

The end of Physics was predicted at the end of the 19th Century... it was all known apparently.

Then the quantum effect was discovered...

Keep banging the rocks together, monkeys, you'll get there in the end...

I blame the black monolith.

Advances in technology and the fundamental laws of physics are separate things and increased knowledge of the fundamental laws may further diminish what we think we can achieve, rather than increase it

[TimberWolf]

It is highly improbable that humans will ever explore beyond the Solar System http://www.universetoday.com/2008/08...ience-fiction/

I like the reader comments there alluding to the fact that science advances so we can't predict now what might be come up with in 20 years, let alone in humanity's entire lifetime. As if the laws of physics can be advanced in the same way computers get better every year

Yeah, in 50 years time breaking the speed of light will be child's play compared to today, current physics will have been long superseded.

[Clippy]

Seems appropriate to post this.

[Addanc]

Why the aliens travel in odd shaped flying objects
Haven't they studied aerodynamics ?

Only need aerodynamics if you are reliant on an interaction with atmospheric gases to keep you in the air.

[Addanc]

Odd that people only started seeing flying saucers after they appeared in Hollywood movies..........

Pilots were allegedly seeing "foo" fighters (UFO) during WWII. The only sci-fi that I can think of that pre-dates this is Flash Gordon and Superman; not really the sort of flying saucer movies you are hinting at.

The biggest pointer to the non-existence of flying saucers is a complete lack physical evidence.