Tag: science

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Mayan Mystic Mathematics, no thanks

Ed Vulliamy has some reasonable things to say about the Mayan `prophecy’ of the end of the world  but he gets it wrong here:

The Maya were no fools. Likely inventors of the figure zero, their mastery of astronomy – bequeathed to history through various codices and stoneworks – was breathtaking not only for its time, but for all time. Their systems for measuring time were more sophisticated than ours, with pivotal numbers of 13, 18 and 20, based upon lunar, Venusian, astronomical and mathematical measurements, and expressed in glyphs.

Vulliamy seems to confuse obscurity and sophistication. Our Arabic-numeral, place-system, method for arithmetic is much more sophisticated than one based on different `pivotal numbers’, because it makes things simpler for the person using it. By having one, and only one, set of rules, all calculations are the same, no matter what size of problem you deal with, a point which will be appreciated by those who had to learn the pounds, shillings, pence system of currency, or by those in benighted countries which continue to use imperial measures. Try doing mental arithmetic switching from base 13 to 18 to 20, without mechanical aids.

Vulliamy then talks of `lunar, Venusian, astronomical and mathematical measurements’, without saying what a `mathematical’ measurement is, and how it might differ from the other three he mentions.

Finally, he is impressed by the Mayans’ use of glyphs: `glyph’ is a fancy word for `character’ or `letter’.

We seem to have here a journalist falling for the idea that any ideas which survive long enough are `ancient wisdom’ and therefore better than our own. Actually, mathematics, and arithmetic, are areas where we can be fairly sure that the modern state of knowledge is definitely better than what people had X centuries ago.

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Getting it wrong

Today’s Sunday Independent reports on a Boeing 757 flying from London to Boston which had to land at Dublin, due to “technical issues with the Boeing 757-200 plane’s nose-wheel steering”. You might ask why an aircraft with duff nose-wheel steering might not simply continue to Boston to be fixed there.

Somebody with a clue gives us some more information:

When the left hyd sys is u/s consequences are:
– 1 autopilot (out of 3) inop;
– No autoland;
– No Autobrakes;
– Some spoilers on each wings inop;
– Rudder ratio inop;
– Left thrust reverser inop;
– Electric slats and flaps extention required (takes longer time and less flaps must be used for landing, Flaps 20 iso Flaps 30);
– Alternate gear extension required (then it is not possible to raise the gear knowing it makes a lot of drag);
– Alternate brakes inop (reserve and narmal brakes are still working);
– Yaw dampres inop;
– Nose wheel steering inop (towing required after landing).

Of all the things that weren’t working, the Sunday Independent noticed the minor one.

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How peer review really works

Peer review is the process which scientific journals use to help editors decide on what to publish and what to reject. It is not perfect and not always a pleasant experience but on the whole it works and researchers freely, and unpaid, give their time to make it work.

The exact experience of peer review for a researcher submitting to a journal depends on the field they work in, but is much the same for most reputable publishers. First, you have to write a paper: you might already have a journal in mind when you start, or you might decide where to send it after you write the paper. You might be boycotting Elsevier or you might not. Either way, you pick a journal.

The choice of journal depends on how good you think the work is and who you want to read the paper. Most people want their work to appear in a good journal, if only as reassurance that the paper is of a certain standard. There is also the pressure to publish in `high quality’ journals which bring prestige to your CV and your department. If your work is good, you also want it to be read by the right people. This might mean other researchers who will appreciate the elegance of your method, or it might mean end-users who will make practical use of your work.

So you format the paper according to the requirements of the journal and submit it through their online system, by uploading a PDF. You might also be asked to nominate an editor to handle the paper, and maybe some potential reviewers. If the editor does not reject the paper immediately, as not within the scope of the journal say, she sends it to the reviewers for advice on whether to publish.

If you are one of the reviewers, you receive an email with some information about the paper, asking if you will take the job on. Usually, you do: other people are doing the same for your papers, so you should do likewise. Your first job is to read the paper. The editor wants to know if the paper should be rejected or accepted. Your second job is to say yes or no, giving reasons and conditions, with a commentary on the paper.

If the author has written a decent paper, the usual response is `Publish with changes’, meaning that the work is good enough to appear in the journal, and is of the right type, but it needs some changes, either to clarify some points, or to give some more evidence for the claims made. Often, this is the first time the paper has been read by another expert, so comments like this are useful and welcome.

The editor gets the reviews, after a month or two, and passes the comments on to the author, possibly with a few words of their own, along with a decision. If the decision is `Accept’ with no changes required (very unusual), the manuscript is sent to the publisher and a few months later, it appears online, and in a printed volume a bit later. If some changes are required, the author sets to work and rewrites the paper: this might take a day or it might take a year, depending on what is required. If it looks unfeasible, they might simply withdraw the paper and send it somewhere else. Likewise, if the paper is rejected, for reasons other than being rubbish, you reformat for another journal and send it to somebody else.

When the paper appears online, it is a `publication’ and you add it to your CV. If you are part of the Research Excellence Framework, you might submit the paper to be included in your department’s submission. Then you start all over again.

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Under pressure

A recent issue of the London Review of Books had this:

The unit of measurement of this pressure is the atmosphere, named after the weight of the air bearing down on us at sea level. We don’t normally think of the air as having weight, but it does. Hold your hand out flat, and imagine an invisible column of air above each of your fingernails stretching up from where you are to the top of the Earth’s atmosphere. That column weighs 1.03 kg per square centimetre—in other words, about one kilogramme’s weight of air bears down on each fingernail. That amount of pressure is one atmosphere.

What is wrong with this is that it misses the point of pressure. The misconception is not unusual. A GCSE physics site says that atmospheric pressure is “about the same force as having over a dozen cars piled on top of you!”

So why are these statements wrong? The error is in the idea that pressure “bears down”. As engineers learn in their first course on fluid mechanics, pressure acts equally in all directions. When John Lanchester says that one kilogramme’s weight of air bears down on a fingernail, he would have been just as right, or wrong, if he had said that one kilogramme’s weight of air bears up on a fingertip. The force on the end of your finger, or anything else, is about one kilogramme of air pushing down, balanced by one kilogramme pushing up: in sum, almost nothing.

But, you object, things get squashed by atmospheric pressure, or by pressure in the deep ocean. The reason is not the pressure, but the pressure difference. When pressure inside a submarine, or an aeroplane, or a soft drinks can, is not the same as the pressure outside, the force is out of balance and the structure has to carry a load to maintain its shape. If you inflate a balloon, you can see how the material stretches as the internal pressure is increased until it is greater than the pressure on the outside. The rubber of the balloon stretches so that the total force due to the difference in pressure, and the tension in the rubber, is zero. Likewise, though you cannot see it, the shell of a drinks can expands slightly to balance the difference in pressure between inside and outside. An aeroplane fuselage behaves the same way; a submarine hull likewise, though with the high pressure on the outside, rather than the inside.