Electromagnetic Spectrum
Posted on 04/05/2005 9:36:50 AM PDT by LibWhacker
The Universe could host billions of Earths
British researchers are more confident than ever that there are "Earths" out there waiting to be discovered.
The scientists say perhaps a half of all the known planetary systems today could be harbouring habitable worlds.
It must be said most of these systems are strange places where supergiant planets orbit close in to their stars.
But Barrie Jones and colleagues say their modelling work suggests that even with this oddness, there should be room for small rocky planets.
The Open University team presented its ideas here at the UK National Astronomy Meeting on Tuesday.
They extend recent and previously published theoretical work, "putting it on a firmer modelling basis," Professor Jones told the BBC News website.
The research calculates the likely number of Earths out there, based on what we know about how planets form and the conditions needed for life - in particular, the requirement to sit in the part of a solar system that is neither too hot for liquid water, nor too cold.
'Disaster' area
"The conclusions haven't changed, I'm pleased to say. Roughly half the systems out there could have Earths in their habitable zones today and have been there long enough for life to develop," Jones added.
The limitations of current telescope technology make it extremely difficult to view so-called extrasolar planets directly.
Astronomers have therefore made most of their detections indirectly - by finding stars that appear to "wobble" under the gravitational tug of what must be nearby, very large planets.
The technique has the bias of only showing up apparently bizarre systems - where planets that are sometimes many times the mass of our own Jupiter circle their stars in orbits that are smaller than Mercury's.
And this presents a problem because current thinking holds that these huge Jupiters probably formed some way out from their stars before migrating inwards. And if they did that, the chances are they would have destroyed all in their path, including any fledging Earths.
"We've now got some simple rules for establishing how far these disaster zones extend," explained Professor Jones.
Moving zones
Encouragingly, his team finds there is plenty room and time for Earths to evolve.
"At the stage these great giants sweep through, the Earths are not formed - they are still smallish planetary embryos. They get scattered but the simulations show enough material remains that Earths can form after the migration of the great giants has taken place."
The team found about half of the known exoplanetary systems offer a safe haven for a period extending from the present into the past that is at least long enough for life to have developed on any such planets.
The situation is complicated slightly by the fact that the habitable zone migrates outwards as the star ages, and in some cases this changes the potential for life to evolve.
Thus, in some cases a safe haven might have been available only in the past, while in other cases it might exist only in the future.
These scenarios of past extinction and future birth increase to about two-thirds the proportion of the known exoplanetary systems that are potentially habitable at some time during the main-sequence lifetime of their central star.
The research by Barrie Jones, Nick Sleep, and David Underwood has been published in Astrophysical Journal.
Good questions! Personally, I'm leaning more and more to the view that intelligent life -- never mind technologically advanced civilizations -- is exceedingly rare. Earth was around for four billion years before life ever evolved beyond the single cell stage, and of the perhaps billions of higher forms of life that have existed on Earth, only one has ever achieved high intelligence, despite its obvious evolutionary advantages, etc.
The Mayans, Toltecs, Aztecs, Souix, Cheyenne, Chippewa, etc.. never discovered the wheel...
The advent of Islam (eventually) destroyed Arab culture..
Without say, Newton, how much longer would it have taken to understand the laws of gravity?
Without Maxwell, would Einstein have deduced the theory of relativity?
Without Tesla, would we have slogged along with a direct current technology? ( He was the inventor/discoverer of alternating current, and the AC generators that provide our electrical services )
What's my point?
There are many things that can go wrong..
The Axis powers might have won WW2, changing the entire direction of world history..
Stalinism, instead of collapsing from economic and social failure, might have succeeded in gaining world control instead..
Politics can guide scientific endeavor.. So can religion, or the dictates of an insane tyrant..
Or, a Natural Disaster, catastrophic in proportion can set everything back to square one..
Even given the number of inhabitable worlds and the possibilities of intelligent life, technology, advanced civilization, War, some alien Bill & Hillary.. ... well, it's just too awful to consider..
They probably are too busy handling their own problems..
There's no guarantee that advanced civilizations mean that all problems are solved..
Just that there are new, and unforseen problems..
I recall a story about a self-replicating organic compound that inhibited the evaporation of water.. accidentally released into the world's oceans, and causing catastrophic drought conditions, turning the entire planet into a desert..
There have been many stories of Post-Armageddon Earth, destroying civilization in varying degrees, with nuclear war, pollution, galactic clouds, meteor strikes, plate tectonic shifts, magnetic poles shifting, overpopulation and.. Alien Invasion..
I'd rather not meet (meat?) anyone from "out there" for another 1,000 years or so.. maybe longer..
Humanity needs a couple of dozen inhabitable planets under our control before we meet (meat?) anyone else..
Did I mention R.U.R.? ( Rossum's Universal Robots.. "To Serve Man and Keep Him From Harm" )
Trouble is you can't get there from here. Not in less you learn how to "fold space".
I prefer the idea of the "Inhibitors" from Alistair Reynolds "Revelation Space." There are secret, relentless, ancient machine intelligences programmed to eliminate any star faring civilization when encountered. Intelligence can rise, but if it gets beyond its solar system, it is inhibited. That's why, in this future, humans have settled a few star system, with slower than light ships, and accidentally trigger the inhibitors.
http://www.amazon.com/exec/obidos/ASIN/0441009425/qid=1112723933/sr=2-1/ref=pd_bbs_b_2_1/104-7205075-7184732
Which ties in with an interesting fact I heard (sorry, don't recall the source). Apparently, thanks to the explosion of broadcasting and wireless communication over the past couple of decades this planet is now the brightest object in the galaxy in the radio spectrum.
If we are able to prove there are some sort of "membrane" separating our universal dimension from others, we someday be able to pierce that membrane, travel 1 "mile" in that other universe, and re-enter ours 1 million light years away..
This is one of these "Be careful what you ask for" situations. We might be able to contact another civilization but what happens if they view us as a food source? Sort of like the buffet table singing "come and eat me."
RadioAstronomer, I have two questions for you about this. First, is it true that the magnitude of radio signals from Earth makes us that bright? Secondly, if it is true, can't we do a survey scan the sky for bright radio objects, similar in intensity to Earth, in our own galaxy, then try to see if there is signal in them? It seems to me any alien civilization using radio technology could easily be as bright as our own world and would be easy to spot.
Interesting and possibly true.. ( it may just be human ego, too. )
The Broadcast "band" is a relativly low frequency portion of the electromagnetic spectrum.. just somewhat above the "bottom", where audible sound lies, and far below visible light..
Not sure it would attract much attention unless someone was specifically listening in that frequency range..
Considering "decades" as a time line, even 50 light years isn't very far, astronomically speaking..
Greetings Earthling.. We would like to "meat" you..
Consider this. Any alien race six to fourteen light years will think Clinton is President. Now you know why they're not talking to us.
Electromagnetic Spectrum
And if the aliens have seen Hillary, they're too afraid to come near us..
LOL. They'ld place a "keep clear" biohazard marker at Alpha Centauri.
Or nuke us from space. It's the only way to be sure...
The universe is one big place. How do you know if their radio waves have even got this far if there is another civilization out there?
The diagram shows "white blobs" in the illustration..
This is atmospheric interference or blocking of the frequency in that range..
Those frequencies in the microwave and infrared range are filtered by the atmosphere, as are the UV, X-Rays, Gamma rays..
I'm guessing that works both ways.. (obvious) and that such outgoing frequencies being transmitted are filtered as well..
This would tend to kill the "brightest radio source in the galaxy" theory..
Remember that most of the AM radio spectrum doesn't even get out of the atmosphere, it actually "bounces" off the stratosphere, and is reflected back to earth..
CB radio operators refer to this as "working skip", and use it to communicate over very long distances, far beyond the capabilities of their 5 watt transmitters..
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