Chandra Wickramasinghe, an advocate of the panspermia hypothesis, is investigating the theory that the colored rains that occurred in Kerala, India in 2001 were colored by extraterrestrial (ET) cells discharged from an exploding meteor, or bolide event. The evidence for the bolide exists in reports of "thunder" during a storm from which red rains fell. While a study commissioned by the Government of India concluded in 2001 that the rains were colored by red algae spores (see), Wickramasinghe's team has to date not mentioned that study at their Cardiff University website.
British Satellite News (BSN) recently posted an inverview of Dr Wickramasinghe. Therein he reports that his team has found DNA in the red cells, which refutes the findings of Louis and Kumar, who reported that the cells had no DNA. In the BSN report, this criterion for knowing if the cells are ETs is presented:
"if no known DNA from Earth matches, the only remaining possibility would be that it is an alien life form from outer space."
The problem with that knowledge criterion is that the set of unknown terrestrial DNA is not proven to be empty. New terrestrial microorganisms are periodically discovered. So if no known terrestrial DNA match some DNA he might find, then a reasonable inference would be that it is uncataloged terrestrial DNA.
The logical fallacy in the criterion rests on is the false dilemma. To see this, note that the argument takes the form ~P -> Q, which is to say: If not P, then Q. A logically equivalent statement is P v Q, meaning simply: P or Q. Their equivalence is proven by way of two transformation rules:
So the following two statements are equivalent and the second makes the false dilemma clear:
1. ~P -> Q assume
2. ~~P v Q conditional exchange, 1
3. P v Q double negation, 2
1. If they do not match known terrestrial DNA, then they are extraterrestrial life.
2. Either they match known terrestrial DNA or they are extraterrestrial life.
Then the form of the indicated false-dilemma argument is:
However, while the argument form (disjunctive syllogism) is valid, in the given case assumption 1 should include as a disjunct "they are unknown terrestrial DNA"; which we could express in sentential logic as, P v Q v R , or naturally as:
1. P v Q assume
2. ~P assume
3. Q disjunctive syllogism, 1,2
Either they match known terrestrial DNA or they are extraterrestrial life or they are unknown terrestrial DNA.
and by conditional exchange back into the original form as:
If they do not match known terrestrial DNA, then they are either extraterrestrial life or unknown terrestrial DNA.
Of course that assumes that we're even inclined to include "or they are extraterrestrial life," which I find to be perfectly silly given there was no genuinely identified bolide event and thus not even a correlation between the colored rains and any astronomical event. Moreover, the rains fell on Kerala sporadically from July to September 2001, hardly like the fallout from a bolide event. Anyway, it will be interesting to see what Wickramasinghe concludes about the Keralan rains. ~Ian
Possible Causal Mechanism of Kerala's Red Rain
Edit: oops, the fallacious argument in the BSN report is not directly attributed to Wickramasinghe.