ALIENS are surely AMONG US: Average star has TWO potentially Earth-like worlds

Re: Tidal forces required in early evolution

competition/mutual benefit.

One of the steps in evolution most overlooked is that the eukaryotic cell is actually most likely a symbiont of several separate "ancestor-organisms", of which one, the mitochondrium, even still has its' own DNA and reproduces separately within the cell.

Something along the lines of that mechanism still exists today,where ( very anaerobic) methanobacteria survive in an oxygen environment by living in the creases of the cell walls of E.Coli bacteria, occasionally temporarily being incorporated as "organelles" within the host body itself. ( and giving rise to the rather rare, but fun, "lightable fart". Ain't biology fun.. ;) )

As far as I can remember the biggest influence the moon has on the earth with regards to the "sustainability of life" is that it stabilises the earth's spin with regards to the ecliptic plane, creating an environment that is more stable than it would be without. Then again, we don't see Mars, or any other planet flipping its axis of rotation all around, so ymmv there.

Never been too fond of the tides-enabling-life/driving evolution theory, given that the moon at the crucial time was a lot closer to the earth, and the tides it created were a bit more frequent and.. prominent.. than the gentle stuff the moon gives us nowadays.

Re: Tidal forces required in early evolution

A moon stabilizes the axis of rotation of a planet. Without one, the axis of rotation is unstable, and sooner or later will pass through the plane of the planet's orbit (with a timescale of under a million years). That's too fast for the evolution of all but mono-cellular life to adjust to a planet that "suddenly" no longer has a day-night cycle. (ie, one where the whole planetary surface is like our poles: half a year of night, then half a year of day).

Don't know how large a moon is needed, but no moon at all is no good at all.

Can Kepler identify how many planets have moons?

Re: More than a coincidence?

It has been suggested that Bodes Law arises because of orbital resonances between planets in relatively circular orbits but even in our solar system it fails once you get to Neptune. We already know of solar systems containing large planets in very eccentric orbits which would presumably disrupt any Bodes Law pattern in their system. Hence it seems a bit of a stretch to attempt to calculate the average number of planets in the habital zone using such a law.

Re: More than a coincidence?

"I didn't think that Titius-Bode sequence was widely accepted as being anything other than a coincidence."

I've mentioned this in El Reg comments before when the subject of Bode has come up... but back in the early 1990s I did a maths GCSE for fun (already have an O level from school) and for the coursework I did a ridiculously long thing on Bode's Law - I keep hoping to find the file on one of my computers so I can re-read it, take out anything irrelevant and unnecessary, and throw the rest onto the web. Fat chance, though, because that was a silly number of computers ago - at least, that's what I thought.

I found a 3.5" disc recently with "Bode's Law" written on the label¹. :)

Unfortunately, though, while I can read the disc if I drag the right computer down from the loft, what that computer won't be able to do is shove the contents over the network to my current computer(s). Or print it. Or anything useful, really. Still, it's a start. :)

^{1. Actually, it says "Bodes Law" - well, I was over twenty years younger.}

Look for the EMP

@Bob W

If there have been nuclear wars on exoplanets, perhaps we should have detected the Electro Magmetc Pulses associated with those bombs exploding.

Re: Goldilocks?

If the aliens read the Wikipedia article on Goldilocks, especially the "interpretations" section where the psychoanalysts get at it, they would put out warning notices to keep away from such a bonkers civilisation.

Re: Goldilocks? @ravenviz

It's actually Girldie Larks and the Forebears, according to Afferbeck Lauder: Father Behr, Mother Behr, Baby Behr and Cammom Behr. Girldie Larks was a juvile dinquent tea nature, whose career in crime was ended when Cammom Behr cut out her heart and threw it down a well. It's a very popular Furry Tile.

Re: Space is big, signals are weak

Furthermore, they would probably switch to digital equally quickly and then start encrypting everything routinely, for commercial reasons if not for anything else. And a well encrypted transmission looks pretty much like random noise.

That's any well-coded signal, ie coded to make efficient use of available bandwidth. The main difference between encryption and "mere" efficient coding, is whether you publish the decoding algorithm and key(s), or not!

Re: When lewis gets back

When lewis gets back

make sure he holds his pen with the same hand he wrote with before he left. Other wise you can assume that ... Hang on there's someone at the door. …. John G Imrie

Knowing something of Lewis’s past history and present circumstance has one thinking of a perfect enough current placement for future deployments of new style 77th Brigade shenanigans/Intelligent Signalling Interdiction Services.

El Reg is certainly no sub-prime operation, is it, and surely a great deal more than just the simple sum of a number of parts.

Re: Lewis has gone out ...

Great minds think alike whenever fools seldom differ, DP ...... and whenever media presents a crooked picture of the present is reality distorted and perverted and a virtual construct for smarter manipulation ..... http://forums.theregister.co.uk/forum/2/2015/02/05/helloo_aliens_average_star_has_two_potentially_earthlike_habitable_worlds/#c_2432834

As soon as you can go to next 7/11 and bring back a thermos of compressed time.

We won't ever do interstellar travel as biological human beings. The speed of light and the vulnerability of mammalian life to interstellar radiation guarantee this.

However, AI or human uploads into Silicon might not be so constrained. They can be radiation-hardened, and can slow down their clock-rate to make the subjective speed of light seem faster by orders of magnitude.

It's also possible that other forms of bio-life might evolve with a slower and less radiation-sensitive chemistry. Some trees live 3000+ years. There's a fungus in the USA that's at least 100,000 years old (also the largest, most massive life-form yet discovered on Earth). Perhaps elsewhere, there are intelligences that live for many My, for whom a 30ky interstellar journey wouldn't seem impossible.

But back to the Fermi paradox - where are they? (Just possibly: out in our Oort cloud, living slowly and quietly. Or here on Terra: we call them fungi, they think too slowly for us to consider them sentient. When they get around to noticing us, they might decide we're a plague and do something about it ...).