SETI is the scientific
search for extraterrestrial intelligence, primarily by using radio telescopes. When I went to the homepage
of the SETI Institute (SETI.org) on January 2, 2017, the first thing
I saw was a great big red “Donate Now” button. I have a rule
about donating to organizations: I insist that they show no signs of
being anything less than completely straightforward and candid.
But does the SETI Institute meet such a criteria?
The crucial question you
should consider before donating to the SETI Institute is: what are the
chances that success will be achieved, and that some radio signals will be
discovered from extraterrestrial civilizations? That depends on what the chances
are of intelligent life existing elsewhere in our galaxy. The SETI
Institute has a FAQ page, and one of the “frequently asked
questions” is “Why do we think that life is out there?” This is
the entire answer given in the FAQ.
In addition, exploration of our own solar system and analysis of the composition of other systems suggest that the chemical building blocks of life – such as amino acids – are naturally produced and very widespread. There are several hundred billion other stars in our Galaxy, and more than 100 billion other galaxies in the part of the universe we can see. It would be extraordinary if we were the only thinking beings in all these vast realms.
This answer is questionable. Let's start with the first sentence:
“Over the last half-century, scientists have developed a theory of
cosmic evolution that predicts that life is a natural phenomenon
likely to develop on planets with suitable environmental conditions.”
This strongly
implies that during the past 50 years there has been some
revolution in our understanding of the likelihood of life developing
on a random planet the right distance from a star. But no such
thing has occurred. Thinking on this matter is pretty much as it was 50 years ago.
Far
from having any theory that predicts that life is likely to arise
whenever there are suitable environmental conditions, we still have a set of
facts that seem to suggest the opposite. We know that even the most
primitive life would require self-replicating molecules, a genetic
code that acts like a complex system of symbolic representations, and
proteins that seem fantastically improbable to have arisen by chance.
Then there's the difficulty of accounting for the origin of the very
complex machinery in cells. The facts we have discovered are still
quite consistent with the idea that the origin of life would be
unlikely to occur on one planet in a trillion, because of the
unlikelihood of these things all occurring because of lucky chemical accidents.
The
second sentence in the FAQ answer is: “Scientific evidence shows
that life arose on Earth relatively quickly (only 100 million years
after life was even possible), suggesting that life will occur on any
planets that have the requisite characteristics, such as liquid
oceans (either on the surface or underground).” SETI
enthusiasts have been making this claim for decades, but it is very
dubious indeed, relying on two assumptions: (1) that the earth's
oceans appeared about a billion years after the earth formed; (2)
that life also originated about a billion years after the earth
formed.
Our
planet is 4.6 billion years old, and claims are made that there are
geological signs of life dating back to 3.5 billion years. But such
claims are doubtful, as they rely on what are called
stromatolites, unusual-looking geological features which some claim
were formed by bacteria. We see no cells or biological structures in
the oldest stromatolites. The claim that very old stromatolites
(older than 3 billions years) are signs of ancient life relies on a
rather complicated and debatable line of reasoning. It's quite
possible that they are not signs of early life, and that there are
alternate geological explanations. This scientific paper says the
evidence for life older than 2.5 billion years is “meager and
difficult to read.”
Moreover,
as discussed here, many scientists think that the earth's oceans are almost as old as
the earth itself, having been brought here by comet bombardments. If
that assumption is true, there may have been as much as a billion years between
the time when life first had a chance to arise on our planet, and the
time that it first did arise. If the shaky claims about the oldest
stromatolites are in error, there may have been as much as 1.5
billion years between the time when life first had a chance to arise
on our planet, and the time that it first did arise. So the claim
long made by SETI enthusiasts that life arose here on our planet
“almost at the first opportunity” is quite doubtful.
Even
if it were true that life on Earth arose 100 million years after it
first had the opportunity to arise, this would not be a strong reason
for thinking that life in the universe is common. Consider this
case. You open your new pastry shop one day, and within an hour
someone comes in trying to order a pizza. The chance of this
happening is very low. You would be mistaken if you reasoned that the
chance of such a thing happening must have been high, or else it
would not have occurred within the first hour of your shop being
open. You are not entitled to draw such conclusions based on the
timing of a single occurrence.
The
article here states the following by MIT professor Joshua Winn
(referring to this scientific paper):
There is a commonly
heard argument that life must be common or else it would not have
arisen so quickly after the surface of the Earth cooled," Winn
said. "This argument seems persuasive on its face, but Spiegel
and Turner have shown it doesn't stand up to a rigorous statistical
examination — with a sample of only one life-bearing planet, one
cannot even get a ballpark estimate of the abundance of life in the
universe."
The next claim in the SETI
FAQ answer is: “In addition,
exploration of our own solar system and analysis of the composition
of other systems suggest that the chemical building blocks of life –
such as amino acids – are naturally produced and very widespread.”
This is true, but ignores the fact that you can't estimate the
probability of something complex arising merely from the availability
of building blocks. A big auto parts store may have all the
ingredients for a car, but the chance of such ingredients forming
into a car when a tornado passes by is presumably very, very low.
The
same type of misleading talk is served up by a recent book on SETI by
astrobiologist David Grinspoon. On page 339 of his book Earth
in Human Hands, he states this:
Much that we have
learned in over a half century of space exploration seems to tell us
that life and complexity are bound to be anything but rare. The basic
ingredients and conditions that facilitated the origin and evolution
of life here seem to be widespread throughout the universe.
The first sentence is not
at all true, and does not follow from the second statement.
Everything we have learned from space exploration is still completely
consistent with the hypothesis that the appearance of life is a
virtually miraculous event that we would not expect to occur on more
than 1 planet in a trillion. You cannot make conclusions about the
likelihood of great functional complexity arising from the mere
availability of ingredients. There may be all the ingredients for a
car in a large auto parts store, but that certainly does not allow us
to conclude that is likely that one day such ingredients will
randomly assemble into a car.
It is true that there may be some kind of purposeful cosmic teleology that assures life is common in the universe, but our SETI experts seem to never appeal to such a possibility, relying on dubious kind of "the ingredients are there, so it will happen" reasoning.
It is true that there may be some kind of purposeful cosmic teleology that assures life is common in the universe, but our SETI experts seem to never appeal to such a possibility, relying on dubious kind of "the ingredients are there, so it will happen" reasoning.
When asking for donations,
SETI experts can gain an advantage if they make it look like searches
for extraterrestrial intelligence are a fairly new undertaking.
People are more likely to donate to a promising new project than some
longstanding project that has failed so far. So if I tell you there
is a promising new cancer drug called thorsmixadine, and that I need
some money to fund initial research on it, you will be much more
likely to donate to such a project than if I had told you, “They've
spent 400 million dollars researching this drug, with no positive
results; but I want to spend even more money, so can you can please
help?”
In testimony before the US
Congress in 2014, the leading SETI scientist Seth Shostak made these
claims giving the impression SETI was some fairly fresh project:
We have only begun to
search...The fact that we haven’t found anything means nothing. It’s like
looking for megafauna in Africa and giving up after you have only examined one city
block.
Such statements were
misleading. By the year 2014 SETI had been going on for decades, and
scientists had checked many thousands of stars for extraterrestrial
radio signals. For example, there was Project Phoenix in the 1980's
consisting of 2600 hours of observations, using the world's largest
radio telescope. A similar project was the SERENDIP project. And when
Shostak made his testimony in mid-2014, most of the work reported in
this scientific paper had been done. The paper describes a negative
search for radio signals coming from 9293 stars, consisting of 19000
hours of observations carried out between May 2009 and December 2015.
An appropriate theme song
for SETI would not be the Carpenters' hit We've Only Just Begun
but a song with the same tune but different lyrics:
We haven't just
begun...to search
So many stars we've
checked
But we keep getting
nothing at all
We haven't just begun
If our SETI scientists
were to be more candid and frank, they would put away their “it's
almost a sure thing” talk and put away their “we've only just
begun” talk. They would instead give a very candid pitch for
donations like the one below. It would probably raise less funds, but
at least it would be forthcoming.
No comments:
Post a Comment