Chance of life on other planets

I think even a single cell has the origins of DNA - Considering everything on Earth came from a single cell, it shows that everything is ancestors of a distant connection.

Suppose however we take into consideration how rare life is in the universe, would it not be more logical to assume that *and considering Panspermia is correct for a moment* that life originated outside our terrestrial sphere, that the rarity of life would assume that its more plausible to suggest that our distant ancestors would have been the same aliens we are hypothesizing right now?

If it came from two different sources, surely that would be more speculative?

 

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This entire thread is wild speculation...

Breaking this down...:
"Suppose however we take into consideration how rare life is in the universe,"
Unknown. We assume it is rare because in out tiny, itty bitty, little pond, we've not observed other life yet.
"would it not be more logical to assume that *and considering Panspermia is correct for a moment* that life originated outside our terrestrial sphere,"
It is only logical to assume that IF you accept as an axiom that Panspermia is correct. Otherwise, it's far more logical to assume that life originated here.
"that the rarity of life would assume that its more plausible to suggest that our distant ancestors would have been the same aliens we are hypothesizing right now?"
We had to go through a Lot of "what if" to get to the conclusion, don't you think?

Is it possible? Sure. But not probable.

The most logical assumption is that alien visitors would be unrelated to us and have evolved under their own conditions.

Given that our entire perception of life is based only on our observation of what evolved here after billions of years... we are remarkably ignorant as to the possibilities of diversity out there.
Would they have eyes? Would those eyes be optical like ours? The most basic things we take for granted as part of being a living thing come into question when speculating about extra-terrestrials.

Perhaps you watched This on T.V:
http://en.wikipedia.org/wiki/The_Chase_(Star_Trek:_The_Next_Generation)


Scientific Reaction to that Episode:

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Nonsense, almost every word.

Let's start with the 11 billion year old figure. There probably are no 11 billion year old Earth-like planets, no Earth-like (CHON-based) life from 11 billion years ago. The stars from 11 billion year ago were Population II and Population III. Carbon, oxygen, and nitrogen, and even more so the metals needed by life, formed with the deaths of the Population II stars. Our sun is a Population I star.

To add insult to injury, it almost certainly took quite some amount of time between the formation of the planet and the development of intelligent life (life capable of escaping the planet's atmosphere or communicating beyond the planet's atmosphere). Reasoning from a sample size of one, which is all we have available to us, several billion years must pass between the formation of the planet and the development of intelligent life. So for 11 billion year-old intelligent life to exist, we aren't talking Population II stars, we are talking Population III. Hydrogen, helium, tiny bits of lithium and beryllium, and nothing else.

Now for the next bunch of nonsense, this:

Do you know anything at all about communications, anything at all about the expansion of space? Apparently not. Signal attenuation becomes a huge problem long, long before the expansion of space even begins to come into play. Even a highly directional comm link such as those used to communicate with space probes in this solar system suffer due to distance. The bandwidth of those signals is very small compared to signals sent locally around the Earth. Distance weakens the carrier signal by 1/r[sup]2[/sup]. To make matters worse, distance also acts to smear the information content. The signal-to-noise ratio also decreases with increasing distance. Shot noise makes the SNR decrease as 1/r[sup]2[/sup]; Johnson noise makes the SNR decrease as 1/r[sup]4[/sup].

The expansion of space makes things worse, not better. The universe became transparent about 380,000 years after its formation. The radiation that was bouncing back and forth in the plasma in that early universe was suddenly free to travel across the universe. The signal was incredibly strong and bright at that time. The expansion of space has weakened and redshifted this signal so much so that what is left, the cosmic microwave background radiation, is now an incredibly weak and dim signal.

First off, the Earth is only 4.6 billion years old. Secondly, life (primitive life) formed soon after the Earth had cooled to the point where it could sustain life. We know life existed 3.5 billion years ago, so it obviously arose some time before that, with some archeobioligists hypothesizing that life formed much before that (more than 4 billion years ago according to some).

Wrong. I have specifically asked for a citation, anything, to justify this claim. Just because you or some other crackpot says something is so does not mean it is so.

 

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It was their lack of resistance to Earth bacterial (and or virus) that saved the Earth from the 30 October 1938 invasion from Mars by large tripod like creatures as told by Orsen Wells. This was a classic radio broadcast which caused great panic in the US.* Fortunately, you can still hear it (everyone should).

Go to http://www.rense.com/general4/hg.htm

then click on the "Listen to ..." link just above the only photo.

That will start the audio download. When it completes, click on it to get the audio started.

There is a couple of minutes at the start, which I am almost sure was not part of original broadcast, explaining that Earth is a tiny rock in space which probably has other more advanced civilizations. To fully appreciate this incredible historic broadcast try to put your self in the mental frame (beliefs about space, Mars, etc.) typical of population in 1938. It anticipates Laser like death rays etc.

This broadcast is part of the american cultural history. Find the time to listen to it.

*So much panic that 18 minutes before the end of the program, CBS's Lawyers or some one became concerned with possible law suits and briefly stopped the program to announce it was just a production of the Mercury Theater. There had been some reports of heart attacks, suicides and other deaths, but later none were confirmed.

After this break, there is little discussion of the violence being caused by the invaders and more philosophical considerations. I don't know, but suspect they dropped the script, or had an alternative ending ready.

 

Yes, it's a worthy classic with a very good social message.

But it ain't scientifically accurate, either.

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ETA: D H,
Point of note; accelerating expansion...

 

I agree everything so far is wild speculation - it's hard not to mind you, concerning the topic.

 

Certainly not with what we know now about Mars, but back then the "facts" about Mars, known by the general population were quite different. (The canals were accepted facts and most likely implied artificial constructions, probably used to transport water from the polar regions, etc. There was still, I think, a large monetary prize for the first definite proof of intelligent life on Mars., etc.)

Every era has its scientific facts, and others widely believed. IMHO Orson's story differs from scientific fact of that era, much less than a large fraction of the posts on science facts you can read here at Sciforums.

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Note the sad irony in right column - Jews finding refuge in Poland.

 

James, i dont think that is a good analogy because someone had to put the egg in the box. This leaves no room for chancne.

Recently i have come to the conclusion that it is VERY possible there is no other life on any other planets. I went from saying 'there has to be...' to 'maybe\probably there isnt.'

Even your own analogy denotes someone put the eggg there on purpose so really it was up to them as to how the results would turn out.

 

A better analogy would be:

"You find yourself inside a box and can't get out yourself. Through holes in the box, you can see an untold (but finite) number of other boxes. You cannot see what, if anything, is inside those other boxes, but you can see that many of them are submerged in water, on fire, or otherwise unsuitable for human life. You imagine that some of them must be suitable, but the only ones you can see, other than your own, are not.

How many other boxes would you expect to have a person in them?"

The problem with limiting the number of boxes to 100, is that you limit the error of anyone who guesses "1 in 10." In the grand scheme, being off by a factor of 10 is not that bad, so a "1 in 10" guess seems like it's in the ballpark. If you remove the safety net and say that you have no idea how many boxes there are, it removes the Schelling points that are the guesses "1 in 10" and "1 in 100". I think, as a species, we are geared to select Schelling points, but not because they are logically valid (or "more" logically valid); we do it because we like to coordinate with others, logic and reason be damned. The real answer to the "100 boxes" version is : between 1 in 100 and 91 in 100 boxes contain eggs...and there is insufficient data to say anything more.

 

False. That is only a list of all the possibilities, NOT an answer. It is possible to tell what is the most likely number of eggs in the remaining 99 boxes. I did and it is 7.

For proof, see: http://www.sciforums.com/showpost.php?p=2621567&postcount=101

All the possibilities are equally probable only when you are in total ignorance. That is far from the case James described in the OP. Humans rarely have complete information about many things, but often can tell which of many possible results is most probable.

For example, from memory, I think that the results of a roll of two die is most likely to be 7 also.

 

False.

First off, you rejected the possibility that James R is playing 99 box monte with us. You assumed, with no justification, that the first box that James showed us is anything like the other 99 boxes. Secondly, with this assumption, did you use a maximum likelihood estimator? A Bayesian estimator? A UMVUE estimator? Nope. You used the unpublished Billy T estimator.

 

No, I took James at his word - that the other boxes may or may not have eggs in them and considered the context he asked his question in. I.e. he was making a simple probability problem similar to the much more complex Drake equation probability calculation. Not "playing 99 monte with us"

Perhaps James will clarify?

I could not "publish my method" as it is standard in most probability books - Certainly in Feller's book which I studied from many years ago. It is the basic method that is the foundation of ALL probability calculations - I.e. enumerate ALL possible outcomes / possibilities and compute their chance of happening. Do you find some error in my analysis?

 

I accused James of playing 100 box monte way back in [post=2614033]post #13.[/post] James' response, [post]2614895[/post],

You did not enumerate all possible outcomes and you did not calculate the probabilities correctly. Let's do 10 eggs spread amongst the 100 boxes, but correctly.

Chance box 1 is found to be full is 1/10.
Chance box 2 found to be empty is 90/99.
Chance box 3 found to be empty is 89/98.
Chance box 4 found to be empty is 88/97.
Chance box 5 found to be empty is 87/96.
Chance box 6 found to be empty is 86/95.
Chance box 7 found to be empty is 85/94.
Chance box 8 found to be empty is 84/93.
Chance box 9 found to be empty is 83/92.
Chance box 10 found to be empty is 82/91.

Multiplying all of these together yields 0.040799532. Do the same for 11 eggs spread amongst 100 boxes and you get a probability of 0.040391537. For 9 eggs the product is 0.040749777. For 7 eggs the product is only 0.038895035.

As one would naively expect, ten eggs maximizes the probability of what was actually observed. Note very well: That what you saw in some experiment is apparently unlikely is a bit irrelevant in estimation theory. After all, if you put enough factors together the probability of seeing any particular event can be very small. You have to play Sherlock Holmes with estimation. The event that maximizes the likelihood of what you did see most likely is, in a Holmesian sense, exactly what did happen.

There are cases where the maximum likelihood estimate is not UMVUE. I do not believe that this is not one of them (but my stats books are ten miles away; I can't go to the bookshelf and grab them right now).

 

No your now red statement is false. James told it had an egg; thus the probably there is an egg in box 1 is unity. He also told that 9 more boxes did not. (I call those boxes 2 thru 10, but naming is just a convenience.) (I have called that box with egg number 1 but that does not matter, I could have called box 82.) What we know is that only 1 of the 10 boxes opened had an egg in it.

That is a lot of information and makes a probability calculation possible to determine the most likely number of eggs that were in the original 100 boxes, assuming James did not use his knowledge, if he had any,* to pick the first 10 boxes opened but that they are a "random sample."

If the contrary assumption is correct, I.e. James has "stacked the deck" to get this result for the first 10 boxes, I agree there is little that can be said about the content of the 90 unopened boxes. But then why would James have made this analogy to the Drake probability problem?

The context of James's question must be considered. The universe was not arranged to give us a sample of 1 planet with advanced life form and a few hundred (the 10 empty boxes) we know do not have advanced life forms with many more (the 90 un-opend boxes) we have no information about (yet).

I don't think we disagree on probability calculations but on what exactly was James asking, and perhaps on what information James had or did not have about the content of un opened boxes.

*I note that there is no reason to suppose that James even knows what the remaining 90 boxes contain, if anything. You seem to be assuming James knows what is in each box and is playing 9o monte with us. Here is what he said:

If James did not know, then the 10 that were opened are a random sample as I assumed. Something like a 5 to 10% sample is often in fact used to control quality in production runs. Calculations like my are done 100s of times in industry each week.

 

By your logic, you have no information at all regarding the contents of the other boxes. You know absolutely nothing.

Or, the result from James R showing the first box is a part of the experiment, and the probability of that event also needs to be incorporated into your results. That of course leads to the derivation of ten eggs total, not seven, in the 100 boxes.

Or, the results from James R showing that the first box is empty has nothing to do with the contents of the other 99 boxes, in which case the best estimate would be zero of the 90 unopened boxes contain an egg.

Your result of seven is nonsense.

 

Nonsense. If that were true then the quality of production runs could not be evaluated by testing a sample. Granted I do not know FOR CERTAIN, but I know what is likely. That is much more than "absolutely nothing." In James' problem, as I understand it, I know the most likely number of eggs in the remaining 90 un-opened boxes is 7.

To give an example from industry:
If GE tests 10% of the light bulbs it ships and one in each 10 tested fails to light, then GE can expect on average 7% of those shipped will be defective. Estimating what is the condition of the untested 90% of a production run is based on test of 10% of the production run is very accurate, in large numbers.

If 1000 egg boxes have been opened and 100 broken eggs were found, then the number of broken eggs in 9000 un-opened boxes is not far from 700, if sample is randomly taken (and all boxes have either a broken or whole egg in them). Such sampling for quality control is very routine - It does provide information.

 

No he's right, it's Nothing.

We can barely detect Jupiter sized planets, in stars only a few parsecs away.

 

Kepler 4b was detected at 1,794 ly and it is but 1/3 of Jupiter's radius.

The Kepler mission is designed to find earth size planets at much much further disances than a few parsecs (6.5 ly).

http://en.wikipedia.org/wiki/Kepler_Mission

Arthur

 

Yep. RIght now, the answer is we don't know. The Kepler mission is a good start toward addressing that lack of knowledge. We should know a whole lot more once the Kepler mission is complete: We should know quite a bit about how many stars have solar systems, period. We should know whether Earth-like planets in Earth-like orbits about Sun-like stars are common or somewhat rare. We should have a better picture of whether our solar system, with several planets spread out over a wide distance range, is the norm or an exception. That said, negative results won't be able to distinguish between rare versus very rare versus practically non-existent, and it won't tell us about life on other planetary systems.

Positive results will tell us where to look in detail.