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Can anyone explain why George Bush is so keen to climb out of one deep gravity well (Earth) just to jump down another (Mars)? It makes much more sense, if (wo)manned space exploration is the aim, to target low-mass bodies such as moons, asteroids and comets where habitation resources and fuel for (far easier) onward …

Your article on perception states that 8 per cent of people have some degree of colour blindness (31 January, p 40) . Just a few pages later, Alexandra Aikhenvald relates how she was surprised to come across the word for "purple" in Tariana, given that the language does not distinguish between green and blue. I …

I for one was heartened to read Sandra Bennett's letter (7 February, p 30) making a connection between cannabis use and declining sperm counts. Surely in an ever overpopulated world, that is yet another argument for legalisation?

Ben Ayliffe is upset about genetically modified beet and skylarks (17 January, p 31) . Skylarks in abundance were a product of the agrarian revolution that was necessary to feed the people congregating in towns, the result of the industrial revolution. In the present day, the most effective and realistic ways of restoring balance to …

In writing about an Apollo lunar mission Phil Scott says, "the third stage then ignited and propelled the cargo…out of Earth orbit and onto a trajectory towards the moon" (31 January, p 26) . But to conform to gravitational theory, it isn't propelled "out of Earth orbit". Instead, it changes to a different gravitational Earth …

Leaving aside anything Einstein may have said on the matter, I hope Lee Baxter chooses the site for his faster-than-light "sweeping" skyscraper carefully (31 January, p 39) . It would be terrible if the mailbag were to collide with Uranus at that sort of speed – which a quick calculation indicates could happen – as …

The news in your story on "mindsight" could explain why, for instance, when you get new glasses, people ask, "Did you have your hair cut?", or why, when my dad started wearing a toupee, everyone said, "Did you shave off your beard?" (7 February, p 14) .

I liked the Feedback quote about hot air balloons from the "department of unusual units" (7 February) . Right next to it in my Â鶹´«Ã½ newsletter was the following, also quoted on page 25 of the same issue: "Capacious crystal breaks roominess record: each gram of the new material has an internal surface area …

Andrew McDonald is right (31 January, p 29) . As a southern African myself I can confirm that we do indeed use "now now" as indicating time urgency. However, I have observed that there is a similar use of repetition here in England, but in respect of location rather than time. For example, a broken …

• Contrary to what senior international health officials told Â鶹´«Ã½, a flu vaccine factory in the Czech Republic has not been turned over to smallpox vaccine production (31 January, p 4) . The pharmaceutical company that owns it, Baxter, did not reply to requests for confirmation before publication. Baxter spokesman Otfried Kistner has since …

I was dismayed to see, in your recent issue, yet another article extolling the benefits of aspirin without any mention of the side effects it can have for many people (7 February, p 36) . The suggestion that governments might consider adding aspirin to the water supply is particularly horrifying. Aspirin intolerance is a far …

I don't eat junk food or fast food, but when I heard of plans to sue the makers of it for causing obesity, I thought: "It can't be as simple as that." However, I have recently learned three surprising things. First, Morton Spurlock managed to gain nearly 12 kilograms in 30 days, and made himself …

Let there be no doubt about it. Fabricated or induced illness does exist (31 January, p 3) . It is rare, but hundreds of professionals involved in the care of children have seen cases. I have seen two. In one of them the mother was filmed attempting to suffocate the baby. It's hard to get …

I read with dismay the claims made in the article on MyDoom, specifically that: "Suspicion over MyDoom's authorship is centring on supporters of open-source software" (7 February, p 6) . This statement is completely contrary to the views of most of the computer security industry and has only been seriously claimed by one group: SCO. …

Good luck and more power to James Beck (17 January, p 42) as he fights to keep those only interested in the profit potential of ill-advised art restoration from destroying the true beauty of our artistic heritage. I remember the long, long queue I stood in during my last visit to the Vatican. I remember …