Posted on 11/15/2005 6:45:01 PM PST by KevinDavis
Ever wondered how life began and whether there is life on other planets? You're not alone, but the curiosity rarely turns into a career.
The UW astrobiology program gives hope to would-be professional stargazers. Astrobiology -- the study of life in the universe -- looks for scientific answers to questions like "How did life begin on this planet?" and "Are we alone in the universe?" The field builds on knowledge across several disciplines.
UW biology professor Peter Ward and UW astronomy professor Donald Brownlee believe discovering intelligent aliens on other planets is unlikely. In Rare Earth, a book the two co-authored, they say the conditions needed for complex life are so narrow that microbial life may be common, but complicated life in the universe is likely rare.
(Excerpt) Read more at thedaily.washington.edu ...
I believe there are many 'professors' who could not find life-forms on THIS planet.
LOL! Funny story!
Based on what evidence? The problem is that we can not yet speak confidently of probabilities or improbabilites because we have only one data point on the graph paper on which we are trying to plot the probability curve.
One data point: we know there is life on Earth. The probability curve can flop around any way until we have just one more data point. We could use one lonely data point to extrapolate an infinite number of outcomes, none of which may be correct.
Your opinion is that we can not be alone in the universe, as is Kevin's, his based on the awe inspiring images returned by the Hubble Space Telescope. Yours are statements of faith. I have no problem with that. But I will wait patiently for data point number two, if it is out there.
Peter Ward says that the book was far from discouraging the possibility of life on other planets. Make a distinction between life and higher life. If we are higher life, it might be that the conditions we would need are rare. For life itself, it might well be that every planet in the galaxy contains life.
How can we prove this? They could have had high technology and there would be no sign of it after all this time.
My take is still that "Intelligent" life is very rare..
I think if it is a low possibility for us to find intelligent life, it stands to reason the opposite is true..
The possibility of Intelligent Life finding US is also very low..
I find it extremely possible that advanced life may have been born, advanced to a high state of civilization, and passed on, ( died out, transformed, emigrated..) without ever having met another intelligent species..
We may find evidence of just that at some time in the future, and it may be our only "contact" with such intelligent life..
Their archaeological remains..
It has been said that when a distinguished scientist says that something is possible, he is almost certainly right, but when that scientist says that something is impossible, he is almost certainly wrong.
We know too little of the universe to say that it is completely barren,
We are quite aware just how far it is "out there". With the speed of light being the fundamental limit for baryonic matter, it will be next to impossible to travel between the stars (at least under our current level of physics knowledge). So the universe may be populated with little isolated bits of intelligence all wondering if any other species are out there.
Just in the past few years we have advanced far enough in our technical prowess to both "announce" to the universe we are here (radio waves) and to receive the same from another species. With that in mind and the speed of light being a constant in a vacuum, the expanding sphere of radio noise heralding our presence has only gone about 60 light years or so. So there may be an entire galactic community out there but our "knock" hasn't yet hit the door so to speak.
(Note: Astronomers use another term for stellar distance that may be not so familiar called the Parsec. A Parsec (parallax-arcsecond) is the distance needed for one astronomical unit (AU) to subtend one second of arc. However for this discussion I will revert to the more familiar “Light Year”)
This also applies in the opposite direction. If there was a radio producing species only 70 light years away and they have had radio only for 50 years, we would have no possible way of detecting them for another 20 years. Expand that out to approximately 100,000 light years (diameter of just our little galaxy) and you begin to see the problem.
While SETI is indeed a long shot, we do have one example of a species that sends signals out into interstellar space: ourselves. This means that intelligent life in the universe is possible and proven. Further, it is possibly detectable if that intelligence uses any form of EM radiation to communicate as we have for years. It is therefore not without merit.
Moore's law has affected the Drake equation in ways we don't even know yet. I personally think the Fermi Paradox is pure BS and not well though out, however, the Drake equation seems to have stood up to scrutiny.
SETI (at least the current trend) is searching for extremely narrowband carrier signals that are Doppler shifted due to planetary rotation. The Doppler shift is extremely important since if it is not there, we know the signal is either terrestrial or an artifact of the equipment itself. The other thing that is very important is the two-antenna approach. If two antennas, separated by a thousand miles, were pointed at the same patch of sky, this would not allow a satellite to "spoof" the system. First, the likelihood of it being within the footprint of both antennas are exceedingly small, and the Doppler characteristics between the two antennas would rule it out if such a thing happened.
All that said, I think the advances in communications technology can cause a search to be futile for many types of broadcasts. Frequency hopping spread spectrum and the like will make it far harder to detect a tool building species that uses radio (EM).
To be fair to the other side there is another factor in this conjecture. A race is progressing along and figures out that the electromagnetic spectrum is the only real practical method of long-range communications. So high-powered transmitters are built as this technology is in its infancy. As the engineering and science of radio advances, they figure out that tight beam, spread spectrum, synthetic aperture, frequency hopping, etc. are a way of not only saving power, but also bandwidth. So for the first 50 years they have been "bleeding" EM into space across a huge range of frequencies into and ever-increasing sphere of radio noise. However, do to technological advances, this RF that is being bled into space quiets down dramatically.
Now, lets jump a few years. This race has expanded off its initial planet and is exploring the solar system it resides in. (IMHO, star travel still remains firmly in the realm of SiFi) Somehow they have to communicate. So again high power transmitters are employed to accomplish this. Light is not out of the question, however, microwave is easy, cheap, less pointing accuracy requirements, and wont be drowned out by the star. So suddenly this race again is radiating RF into the universe. So according to this scenario, a race can emit RF then grow silent for a time, and then restart emitting RF.
Why EM and not some other means I hear you ask?
There appears to be only four fundamental forces in all of nature; Strong Force, Weak Force, Gravity, and Electromagnetism EM. Both the strong force and Weak force are confined to the nucleus of the atom. Gravity requires prodigious amounts of energy to manipulate, so the only one that appears practical for long distance communication is EM. In an extremely short period of time, we are using EM across the entire spectrum from basically DC to light.
I personally believe for a race to become technologically advanced, it must eventually realize the need for the ability to store and convey information over long distances. Since radio waves (I am including any EM in this such as RADAR, TV, microwave, etc.) are still the best method for accomplishing this, any other race would use/do the same. For about the past 60 years we have been isotropically radiating EM across a huge RF spectrum into outer space. What many SETI systems are looking for is another species that is doing the exact same thing we are; unintentional radiation of EM into outer space.
Even the nearest star (Proxima Centauri), actually a member of a ternary star system, is 4.22 light years away. This is why radio and/or optics (I know some people who are contemplating optical SETI) are the best and at the moment the only way to find other civilizations. The advancing sphere of radio noise radiating from our own planet now encompasses an area more than 120 light years across. There are literally thousands of stars within that volume of space. As we measure the heavens with more precise instrumentation we are finding a plethora of planets orbiting other stars.
A few years ago there were many people who were quite skeptical about the possibility of extra solar planetary systems. Statements were made like "just because there is one known planetary system (ours), it doesn’t mean there are others". It appears now that planetary systems are the norm instead of the exception. I am now hearing the same argument against the possibility of ET. I personally do not "believe" ET is out there. I suspect ET is out there. We are finding the building blocks of life through out the heavens. I also think life is far more tenacious than most people believe. We even find life in the sulfur volcanic vents on this planet.
The other question that periodically comes up is “what about von Neumann probes”?
Two things. First, there may me thousands of races out there, but they are "stuck" just like we are by general relativity. Sigh! Second, the prodigious amount of time it would take to cross the galaxy at sub light speed would possibly prohibit even the most ambitious race from basically spending the money and wasting the precious resources of a local solar system to attempt that feat. Also how long can a machine function and replicate without error entering the picture. Not unlike evolution. :)
And just where in the heck do we look and at what frequency?
Lets start with a bit of a background:
Radio astronomers use temperature to describe the strength of detected radiation. Any body with a temperature above -273 deg C (approximately absolute 0) emits electromagnetic radiation (EM). This thermal radiation isn’t just in the infrared but is exhibited across the entire electromagnetic spectrum. (Note: it will have a greater intensity (peak) at a specific area of the EM spectrum depending on its temperature). For example, bodies at 2000 K (Kelvin), the radiation is primarily in the infrared region and at 10000 K, the radiation is primarily in the visible light region. There is also a direct correlation between temperature and the amount of energy emitted, which is described by Planck’s law.
When the temperature of a body is lowered, two things happen. First, the peak shifts in the direction towards the longer wavelengths and second, it emits less radiation at all wavelengths.
This turns out to be extremely useful. When a radio astronomer looks at a particular point of the sky and says that it has a noise temperature of 1500 K, he/she isn’t declaring how hot the body (nebulae, etc) really is, but is providing a measurement of the strength of the radiation from the source at the observed frequency. For example, radiation from an extra solar body may be heated from a nearby source such as a star. If this body is radiating at a temperature of 500 K, it exhibits the same emissions across all frequencies that a local test source does. The calculated noise figure will be the same across all frequencies. (Note: this does not take into account other sources of radiation such as synchrotron radiation).
So, here’s the rub. Not only does the source that is of interest to the radio astronomer emit thermal radiation but also both the local environment (ground, atmosphere, etc) and the equipment (antenna, amplifiers, cables, receiver, etc) being used to make the measurements. To accurately observe and measure the distant sources, the radio astronomer must subtract all of the local environment and detection equipment noise additions.
In 1963, Arno Penzias and Robert Wilson were working with a horn antenna trying to make it work with as high efficiency as possible for the Telstar project. This antenna was also going to be used for radio astronomy at a later date. They pointed it to a quiet part of the sky and took measurements. When they subtracted all of the known sources of noise, they found approximately 3 K left over. They worked very diligently to eliminate/describe this noise source and were unable to. This mysterious source of noise seemed to be there no matter where they pointed the antenna. What they had discovered was the microwave background produced from the Big Bang. This 3 (closer to 2.7) K microwave background originated approximately 300,000 years after the Big Bang itself had occurred. It has been determined that when these signals originated, the universe had already cooled down to around 3000 K.
So what frequencies do radio astronomers use and subsequently SETI?
There are two real sources of noise that limits the radio astronomer's ability to search for very weak signals. The galactic noise halo interferes with us below 1 GHz and noise due to earth's atmosphere interferes with us above about 10 GHz. This pretty much keeps all SETI searches (at least radio ones) between 1 and 10 GHz. Inside these two frequencies, from about 1.4 to 7 GHz the noise level drops off even further to near the 2.7 Kelvin Cosmic Microwave Background (CMB) that permeates all space. Hydrogen (H) molecules, the most abundant element in the universe, excite and emit (masers) at around the 1.4 GHz frequency (21 cm band) and the hydroxyl (OH) emits at around 1.65 GHz. This is where much of our radio astronomy and SETI research is concentrated. Since H + OH is water, the frequency gap between these two is often called the “Water Hole”.
Also SETI searches are not looking for intelligence riding on a signal itself. The scintillation of the interstellar medium will quickly make that unintelligible. What most current SETI searches are looking for, is the extremely narrowband signal (carrier) that the information rides on. Indeed as we evolve into more "spread spectrum" type signals, the carrier(s) will be harder to detect. However, I think that will be a temporary phenomena. As we spread out into the solar system, we again will require high power carriers to convey information from point to point. So there may be a naturally "quiet" period in many advanced races prior to then spreading through out their solar system.
(from: http://www.seds.org/~rme/seti.html)
"Given an effective radiated power of the transmitter (in watts), the effective area of the receiving antenna (in square meters), the excess receiver noise temperature of the receiver used (in K), the averaging time of the receiver (in seconds), and the accepted band-width of the signal (in Hz), the range at which we can detect a signal transmitted by an intelligent civilization, is:
R=8x10-6(PeA/T)1/2(t/B)1/4 light years.
Where the constant is calculated from 1/[9.4608x10 15(4”pi”k) ½]. Here the constant is the number of meters per one light year, and k is the boltzmann constant.
So to offset some of the limitations, we (SETI searches in general) are looking for extremely narrow band CW waves that have been Doppler shifted due to planetary motions.
However, this is not fraught with its own set of problems. Much of our own radio transmissions do not fall within this range. Also this is one of the coveted frequencies of radio astronomers, thusly we have international treaties to not broadcast at these frequencies since they would interfere with radio astronomers. So here we are looking for signs of a narrowband signal heralding the fact that intelligent life is not wholly constrained to our tiny little planet at these very frequencies.
Just imagine another tool building species that ends up developing radio and radio astronomy that may also recognizes the importance of this 21cm band. And they also may instigate a SETI search using these same bands such as we do. So here is the question. Would they hear us at those frequencies? They are the very ones that we are not transmitting on at all. I could just see 500 races all looking for each other at the very frequency band that none of them are transmitting on due to the very nature of its importance for the exploration of the universe.
Here is an excerpt from a paper I wrote a while back: (note: I cannot get the symbols for Pi or lambda to work )
With any link, there is parameter called a link margin. This the margin of degradation before the Bit Error Rate (BER) becomes unacceptable. This margin must take into account signal attenuation due to distance, atmospheric conditions antenna gain, transmitter power, frequency, etc.
The energy of an electromagnetic wave is directly proportional to its frequency. The Energy (E) equals Planck’s constant (h) times the speed of light (c) divided by the frequency of the wave (“lambda”): E = hc/”lambda” or in other words since c = “lambda”*v (v is frequency) then E = h v
Whereas Planck’s constant describes the nature of matter and energy at the atomic levels. Planck’s constant is; 6.626 x 10-34 Joule-second. A joule is the amount of energy exerted when a force of one (1) newton is applied over a displacement of one meter, which is also equivalent to one (1) watt of power radiated for one second.
All of these equations lead up to the simple fact that the shorter the wavelength, the higher the energy of the wave.,
The following are just a few of the things that affect link margin (being able to receive data):
1. The frequency of the wave
2. RF interference (local radio noise, solar RFI, another satellite, etc)
3. Bit rate of the data
4. Antenna elevation (such as a 5° contact with the satellite versus 85°)
5. Atmospherics (rain, clouds, snow and the like)
6. Solar affects (sunspots, geomagnetic storms, solar flares and storms, etc)
7. Antenna gain and size
8. Radiated power from the transmitter
9. Antenna type (omni, dish, yagi, etc)
10. Antenna efficiency (efficiency of the LNA and the like)
All of these items must be taken into account by the RF engineer whenever he/she is designing the link. I have defined a few of the terms you may run across that are used by the engineers when describing or computing link margins.
FSL (Free Space Loss)
Loss in free space is a function of frequency squared plus distance squared plus a constant. Free space means transmission without absorption or reflection of energy. Expressed in decibel form, the free space loss is:
(FSL)dB = 20log(4"pi"d/"lambda")
Where "lambda" is wavelength.
EIRP: (Effective Isotropically Radiated Power).
Dish Antennas are a very directional antenna. This allows most of the radiated power to be broadcast in a single direction. EIRP is the power received that the antenna appears to broadcast as if it was an isotropic radiator. Thusly it is the product of the gain of the antenna and the transmitter power.
EIRP can be calculated using the following formula: EIRPdBW = P0 + Lt + G1 where P0 is the power out of the transmitter, Lt is the transmission line loss, and G1 is the gain of the antenna.
Eb/N0: (Energy per Bit Noise Density Ratio)
This is the efficiency of the digital communications with respect to the noise on the link. N0 is commonly measured by the received bit energy to noise density ratio Eb/N0.
C/N0: (Carrier to Noise Ratio).
C equals Carrier power received and N equals the noise of the ground system.
G/T: (Gain-to-Noise Temperature Ratio)
Basically this is a ratio of the Gain of the ground station antenna to the Noise temperature of the ground station RF equipment.
Putting this all together gives us a “feel” for the link budget:
The link budget is a tabular method of calculating the space communications systems parameters. So the total equation would look something like this:
C/N0 = EIRP – FSLdB – (other losses) + G/TdB/K - k
Where FSL is the free space loss, k is Boltzmann’s constant (1.3806 x 10-23 joule/K) expressed in dBW or dBm, and the “other losses” may include:
· Polarization loss
· Pointing loss
· Off-contour loss
· Gaseous absorption losses
· Atmospheric effects (such as rainfall)
· Localized interference
Note: off contour loss refers to spacecraft antennas that are not earth coverage, such as spot beams, zone beams, or multiple beam antennas.
How do you explain how God was created ? If you can't explain it, we must assume God does not exist.<{> It is a stupid statement but no more stupid than the one you posted.
We are about ready to "go dark". Digital tv and radio consumes much less power than analog.
Hard to know what the article means by rare if one in a billion gives trillions of potentially habitable planets.
When science cannot explain something, it simply means it is unexplained. It says nothing about whether it can be explained.
Major scientific puzzles have been noted centuries before their explanation.
"Infinite time and infinite space yet we have had no contact. "
We have only been able to detect the most primitive forms of contact for less than 100 years.
Basically, we have existed as a grain of rice in a giant haystack for less than a blink of a cosmic eye - and you're apparently taken the fact that no other life has contacted us as an indication there is no life out there?
I guess it's the whole 'center of the universe' thing - "If we haven't been able to detect it yet, it can't exist"./
We're short timers in the universe - more people would be better served by humbling themselves according to their place in the vastness of the universe. It's not all about earth.
It is not just 5 billion years, but puddles of water and/or tide pools. Each one is a little test tube with its own chemistry. I don't know how many there were on earth, but it must have been in the trillions.
I think we would have found a satellite or some space junk still orbiting if the dinos could put one up. How about some platinum coinage too.
Humans junk would still be found 100 million years after we left earth if that were to happen. If nothing else, we should find unusual radiation where the dinos put radioactive waste dumps, even after 65 million years.
>>>How do you explain how God was created ? If you can't explain it, we must assume God does not exist.<<<
LOL! I see logic is not high on your list of educational tools.
This is a good point. I've thought for a while that birds are the closest thing we have to parallel, non-mammalian evolution of intelligence. This thought has occurred to me many times, as I live with a parrot.
Birds aren't mammals, of course, yet some of them-- like parrots-- have developed characteristics similar to ours: they are highly social, they have close family bonds and also organize into larger than family groups, they have sophisticated means of vocal communication, they are long-lived, they travel significant distances at various times of the year for food, and they have grasping limbs (their feet) with which they might manipulate their environment. These are the factors, we're told, that spurred the development of human intelligence. When you consider these factors, it's no suprise that parrots are very bright. My bird is cleverer than any dog I've known, for example.
The brains of intelligent birds are organized very differently than mammalian brains, too. They are more efficient per unit of weight and size than our designs-- hence the reason birds like parrots and crows can outthink similar sized mammals.
However, even more important than intelligence to a bird is the ability to fly. It's thought that the largest a non-gliding, flying bird could get is about thirty-five pounds. That's the weight of a swan. Birds with non-aquatic lifestyles-- hanging out in trees, building nests off of the ground, or eating foods that are widely dispersed and only available in smaller quantities at a time-- are probably even more limited in their largest practical sizes.
So, it might be that the most intelligent birds-- like parrots or crows-- are about as smart as birds can get given their lifestyles. At least, you would suspect that if it were an advantage for any birds of those kinds to be more intelligent, counting costs of that increase like larger body size, they would have developed more intelligence by now.
So, the case of birds might suggest that the favorable conditions for the development of technical intelligence are unusual, even among relatively bright, social animals.
Thanks for the Ping and exposition of the parameters involved!
It is known that there are an infinite number of worlds, simply because there is an infinite amount of space for them. However, not every one of them is inhabited. Therefore, there must be a finite number of inhabited worlds. Any finite number divided by infinity is as near to nothing as makes no odds, so the average population of all the planets in the Universe can be said to be zero. From this it follows that the population of the whole Universe is also zero, and that any people you may meet from time to time are merely the products of a deranged imagination.
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