Complex Life May Be Possible In Only 10% of All Galaxies

sciencehabit writes The universe may be a lonelier place than previously thought. Of the estimated 100 billion galaxies in the observable universe, only one in 10 can support complex life like that on Earth, a pair of astrophysicists argues. Everywhere else, stellar explosions known as gamma ray bursts would regularly wipe out any life forms more elaborate than microbes. The detonations also kept the universe lifeless for billions of years after the big bang, the researchers say.

Comments

Let's do the math

[cat_jesus]

10% of infinity is...... hmmm, carry the one...

Um 7?

Re:Let's do the math

[boristhespider]

No, it's definitely false. Current data strong favours a universe that is flat (ie infinite), while it only narrowly supports a universe that is open (ie infinite and shaped like a foliation of saddles), and only slightly better favours a universe that is closed (ie finite and shaped like a foliation of spheres.) More carefully speaking, I believe the constraints at the minute are something like \Omega = 1.02 +- 0.03 (at one sigma, or aroudn 67% confidence). Meaning that while it is possible the universe is open or closed our best evidence at the minute is that it is entirely consistent with flat, and that this consistency linked with Occam's razor suggests that we may as well take it as flat.

Meaning that the universe is probably infinite.

These considerations do not take into account the universe's topology, of course. The universe can be flat but finite if it is, for instance, on a torus. It could also be on any number of absurdly-shaped topological structures. This is because cosmology is based on general relativity which is, by definition, a local theory. Topology is, by definition, a global theory, and unless the characteristic length-scale of the topology of the universe happens to be within the characteristic length scale of the universe itself (ie if the "radius" of the torus is roughly of the order of the horizon), we're not realistically going to tell the difference between an infinite, flat universe and a flat, toroidal universe.

Occam's razor can again come into play here and suggest that the universe is, as a result, flat but we should probably begin wondering whether that razor's getting a bit blunt.

Practically alone...

[Anonymous Coward]

So there are only 10 billion galaxies out there that can support complex life like that on earth? We're practically alone!

Relativistic Species

[Scottingham]

I always like to think that any suitably advanced civilization eventually develops space-drives that can reach appreciable percentages of the speed of light. The time dilation effects would make traversing the galaxy relatively(heh) reasonable. The only hitch is that relative to all other lifeforms not moving at a such a speed would blink in and out of existence in the time it would take them to burp. Our current sliver of space-time is sooo tiny if you think about it like this.

What if there was a whole...dare I say...confederation of relativistic societies? In order to join you have to catch up. Otherwise you'll be gone in a blink.

Our galaxy is one of those 10%

[djnanite]

On the plus side, it seems that our galaxy is one of the 10% capable of supporting life.

So at least we only have to start looking locally...

My take is tech makes radios sound like noise.

[Ungrounded Lightning]

I also subscribe to the "great filter" theory. About 25 years after the radio was invented, we were busy gassing each other in trenches, followed closely by a global pandemic, then mass genocide, then teetering on the edge of nuclear war. That's not a very wide window for aliens to notice our presence, if they rely on artificial radio waves to detect intelligent life.

My take is that technological improvements make radio sound like noise after a few decades. Early radios systems are very simple things which have signals (CW, AM, FM, ...) that are very distinct from electrical and thermal noise. Their signals were both drastically different from, and drastically stronger than, the background, enabling simple detectors to separate a signal's information from all that chaff.

Modern radios (such as spread spectrum systems, especially OFDM) squeeze nearly the Shannon Limit out of precious bandwidth (and also be frugal with transmit power) by using nearly all of it to carry information. This makes them virtually indistinguishable from a celestial object with a little extra heat (buried among things like stars, which have a LOT of heat).

It was only about 120 years from when Hertz and Tesla started making easily detectable radio waves to the Analog Television Shutdown, a significant milepost in the decommissioning of easily detectable radio signatures. I expect that, within anther few decades, the Earth will be emitting very little that might be recognizable as a radio signature of intelligent life, unless we expend a bunch of energy sending such a signature deliberately.

So my solution to the mystery expressed in the Drake Equation is that L (the length of time for which such civilizations release detectable signals into space) is short, not due to the falls of civilizations, but to economic incentives to use the aether only in ways that are no longer noticeable at a distance.