The purpose of this document is partly based as a reply to the article in Scientific American of January 2011 with the Title: "Space Contact The Day after" By Tim Folger. See: Contact: The Day After
For more information about the SETI project read: Lit 1
The article starts with the following sentence:
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He wanted to aim at the two sunlike stars Tau Ceti and Epsilon Eridani, each a bit more than 10 light-years from Earth, to see if he could detect radio transmissions from any civilizations that might exist on planets orbiting either of the two stars.
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This raises immediate two questions:
- How do you receive those signals and
- How do you transmit those signals.
IMO the second one is the most difficult: How do you transmit a signal with a certain base frequency that is clearly stronger than the background noise from your star and that can received 10 lightyears away. Such is transmitter must be extremely powerfull. In fact there are two frequencies involved: A carrier frequency and a message frequency.
To get some idea about the problems involved read this: Basics of Space Flight Chapter 6 Electromagnetisme which explains the power law and Chapter 10 TeleCommunication Specific read the Section "Signal Power"
From that section we can learn two things:
- A spacecraft typically does this (transmitting data towards us and concentrating all available power into a narrow beam) by using a dish antenna, perhaps a few meters in diameter, trained precisely toward Earth.
In the context of Search for Extraterrestrial life this sentence becomes: - A civilization overthere communicates with us by using a dish antenna, perhaps a few meters in diameter, trained precisely toward our civilization.
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How does a civilization overthere do that ? How do you pinpoint the light from a lighthouse with an extremely small beam towards a star at a distance of 10 lightyears ?
- The spacecraft is the only thing that we can detect at that frequency (unless it is happens to be close to the noisy sun as seen in the sky).
Also here you have a problem:
- How can we detect this signal which originates close from a distant noisy star and which travels in our direction ?
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Next we read:
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He says:"That means one of every some million of stars (in our galaxy) has a detectable civilization"
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The question is what does he mean with detectable civilization ? Instead of "a detectable civilization" he should have used the words: a civilization like ours. A complete different question then becomes: can both civilizations in principle detect each other, which is the topic of my two questions.
Next we read:
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"If this experiment has merit, it's going to succeed (to detect a civilization) within two or three years" etc "If it doesn't then there is something fundamentally wrong in our assumptions. If it is going to happen , it's going to happen soon"
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What this means is that the author in fact supports both opinions.
Next we read:
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- What happens after we detect a signal from an alien intelligence ?
- Could we even translate the message?
- How likely is it that the message might contain knowledge
- and that would transform our culture?
- Would it be dangerous to respond
- and reveal our existance to beings from other worlds?
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There is one question before this: How do we decide that there we receive a signal which comes from an other civilisation.
Accordingly to the text: "The signal would have to be narrow with a lot of energy packed into a few frequencies." At the next page we read: "The frequency should be 1420 megaHerz, the spectral frequency of common hydrogen." Implying no frequency shift.
IMO there are three problems:
- Is it technical possible to make an hydrogen laser with enough power that it's light can be detected at a distance of 11 lightyears ?
- How do you use this signal for communication ? IMO the only way is by means of Amplitude modulation. Lit 6 at page 80 mentions a communication frequency of 5 Kz.
- Suppose that we receive a signal that is Amplitude Modulated, consisting of 0's and 1's of different lengths (?). How do we now that it contains information ?
- That means the modulated signal should not be completely random, implying no information
- Nor should the modulated signal be 100% periodic
- But some where in between.
That means certain parts should be periodic (identical) and certain parts should be different.
The periodic part are there to identify that the signal is artificial created. They serve as some form of synchronization signal.
The different parts should also not be to different. In fact only certain patterns are allowed to create an alphabet and to include additional communication patterns.
When we use Morse code as a modulated signal both sides perfectly know what the transmission alphabet is.
It is an interesting execercise by having two teams:
- one team sending and using its own code and the second team having two tasks a) to demonstrate that the receiving code contains information and b) what the message is. The extra constraint is that the second team has no clue when the message start and the message is not written in English.
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Now let me start with the first question of the 6 questions raised in the Scientific American Article.
1. What happens after we detect a signal from an alien intelligence ?
In the article we read:
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Accordingly to voluntary,nonbinding protocols adopted by SETI researchers around the world, if IAU astronomers confirmed a signal as geniune, they would then notify the United Nations and various world leaders.
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IMO only the part in bold is important. How do IAU astronomers come to the conclusion that a signal is generated by artificial means? I do not know how they decide. The article does not give a clue. It only states:
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SETI instruments are designed to search for steady,periodic narrow band radio pulses etc. The pulse itself would yield no information, other than its artificial nature.
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I expect that the message is: We are rather certain that etc. IMO the chances are very low.
2. Could we even translate the message?
Accordingly to the article:
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Even a large radio telescope would need to repeatedly scan a smalll patch of sky to build up the signal pulse above background radio noise. etc. Resolving the message would require an antenna for more powerful than the Earth's largest disc etc.
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I doubt if that will help you.
Near the ET's signal is the text:
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In the simulation above, the signal (at center) pokes through background noise.
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That simulation is misleading. It expresses a wish. In the document is written:
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Even if it proves impossible to directly translate the message, it might be possible to discover patterns that he suspects are fundamental to all languages. etc. He devised a computer program that compares any unknown language with a datbase of 60 human languages.
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I expect you have a better chance to communicate with other civilizations if you follow the solution proposed in the Seti exercise example.
3. How likely is it that the message might contain knowledge
I expect the chance is very small.
Try it Yourself.
4. and that would transform our culture?
The same: IMO the chance that we can learn anything from any other civilisation is extremely small.
Are we in anyway capable to do the reverse ?
5. Would it be dangerous to respond
I do not think that it really makes sense to try to reply, because communication around time is very large.
Anyway what should be your answer ? Something like:
- Hello out there. Yes we have received your message. We are glad that we are not the only civilization. How is the weather ?
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In the article we read:
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He said: "that transmitting messages without knowing what is out there could be dangerous." etc.
He warned of the possibility of predatory aliens ravaging the resources of world after world. etc.
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For more detail read: Lit 7. IMO that is not the right attitude for a scientist. We have absolutely no prove that such a scenario is realistic, nor are we in anyway capable to do this ourself.
6. reveal our existance to beings from other worlds?
IMO we can do that, without any fear, if we want.
In fact receiving messages and sending messages are two completely separate issues, because any form of communication will be very difficult. Its like sending a message by your paraents and receiving an answer by your children.
In the article we read:
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"Aliens who have a mere 1000 year head start on us could listen to our conversation right now" etc "They could read our lips"
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IMO this is all (sorry to say) "baloney". There exist absolutely no evidence that such a scenario is physical possible. This whole discussion has a rather high "suppose" content, which is not scientific.
In the article is written:
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Image a spacecraft with 50 passengers. etc. Suppose the nearest star with a habitable planet is only 10 light-years away. etc. And assume you can go 10 percent the speed of light. etc.
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A much more realistic speed is 1000 km/second and that is already very fast.
If you study document:Lit 2 than Voyager 1 has between "day 252 of year 1977" and "day 323 of year 2015" (which is a total of 13941 days or 1204502400 seconds) travelled a distance of approximate 133 AU or 19896516710 km. If you divide those two numbers you get a speed of approximate 16.5 km/sec
The fastest moving star has a speed of 1600000 miles/hour. See Lit 2. That is equal to 2574950 km/hour or 715km/sec.