Y Safle

The media is working itself up into a feeding frenzy again. This week’s issue: the alleged dangers of WiFi radiation. First BBC Radio news, then Newsnight, now the Daily Telegraph have all had articles from quoting from people who believe that there might be health risks from WiFi. The BBC programmes at least balanced the sillier claims by noting that WiFi power output is far lower than that from mobile phones.

The Daily Telegraph, on the other hand, had this nonsense:

However it is believed that a classroom containing 20 laptops and two routers could combine and be equivalent to the emission from a mobile phone.

Notice the use of passive voice: “it is believed”. Who believes this?

It turns out that no-one does, although the Telegraph quotes from the “Powerwatch” web site. On this site, there is a calculation designed to show that a room full of 20 computers and an access point (or two) is *approaching* the power output of a mobile phone call.

But this is arrant nonsense. It is nonsense because of the silly assumptions being made about average distance from antennae. It is nonsense because they first make an assumption of low power output from the phone, and it is especially nonsense because it makes no difference whether you have one computer or fifty in a room. The maximum power output is the same – capped in the UK at 100mw (but usually less than this).

Let me explain: WiFi stations are receiving a radio signal when they receive data. But if two stations transmit a signal at the same time then what occurs is a collision – the signal is garbled and not received. The solution is that WiFi uses a collision avoidance scheme to try to ensure that packets are never sent out whilst another station is already transmitting. A couple of carrier sense mechanisms are used to do this, and the result is a very low collision rate. Essentially, if one station is talking, all the other stations are quiet. Click on the thumbnail image to see how this looks in practice. Each wireless station waits a random amount of time before transmitting, and if another station transmits first, the wireless station will quietly defer to it.

Therefore the maximum power output from a room of 20 computers remains capped at 100mw. What is more, no one station is transmitting all the time. For the majority of the time, even on a congested network, each station is actually transmitting nothing.

And that brings us to the next bit of nonsense – the assumption of the amount of traffic in transit. The powerwatch page assumes more than 100% usage for periods of two hours or more in its calculations. Note that if a single wireless station on an IEEE 802.11g network were downloading constantly (and that the downstream network could maintain the same throughput), then even assuming protocol overheads reduce the actual throughput to a mere 30 Mbps, over a course of two hours, that station would download some 26 Gigabytes of data.

To put this in perspective, fairly heavy Internet users download about this quantity of data in a month. Light users (people just browsing the web, using email and similar) would not get close to this figure.

26 Gigabytes is the equivalent of about 44 CD images, or several thousand podcasts. It is a guge quantity of data – not the kind of thing people will be downloading in one sitting – and certainly not regularly.

Ah, you say – but spread between 20 computers? What classroom environment is encouraging pupils to download over a gigabyte of data per computer? None!

So the assumption of 100% utilisation is nonsense.

Next problem: The assumption is made that people are – on average – a metre from the transmitting antenna.

This is just silly. The writers seem to know that magnetic fields decrease by the square of the distance from the antenna, but they assume that on average, people are a metre from the emitted radiation. Based on the fact this is a classroom, and 20 stations are variously transmitting, the fact that some of these transmitters will be many metres away only really makes this assumption if the pupils have swallowed the transmitter.

Admittedly, I wouldn’t put this past some children – but if they have done so, they probably have worse problems to deal with than the emitted signal from the station!

No, in fact the vast majority of the transmissions come from the access point. (Remember, we download much morethan we upload) this may not even be in the class, but if it is, it will probably be several metres from even the nearest child. The law of squares tells us that these signals will be far lower than the silly assumption made on the powerwatch page and repeated uncritically by the Daily Telegraph.

As one commentator on the Telegraph page says:

“Can there ever be a better example of why the current decline of Physics teaching in schools and universities is so worrying?”

Let’s give the last word to Mike Clark, senior spokesperson for the Health Protection Agency. He has run the figures rather more intelligently than the Powerwatch pressure group, and tells us that 1 year of exposure to WiFi radiation in a classroom is equivalent to 20 minutes on a mobile phone.

Maybe we could quibble and bring that down to a month or so. So what? The worry with mobile phones is that the radiation causes excitation of water molecules in the brain near where the phone is held to the head. This causes a slight warming effect which could theoretically be a cause for concern, although there is no proof of harmful effects.

WiFi radiation – if it causes any warming at all – is so slight as to be unmeasurable.

There is no risk here.

Following the server crash yesterday, I have now replaced all the postings that went missing over the last month. As far as possible, I have also replaced the missing comments. These are posted with original attribution but under my name. Apologies that this will put the frequent commentator list out – but it was the easiest way.

Still to do:

- Upgrade WordPress (again!)
- Install “In Series” (again!)
- Recategorise the series
- Add some or all of the photos back from the last month’s posts
- Put back the rotating site banner and the associated pictures

If anyone else loses data in this way, remember – Google is your friend! (Particularly the Google cached text).

Please note that a few of the most recent comments were lost, as Google had not cached these.

“In my view, the Christian religion is the most important and one of the first things in which all children, under a free government ought to be instructed…No truth is more evident to my mind than that the Christian religion must be the basis of any government intended to secure the rights and privileges of a free people.”

Noah Webster (Preface to the 1828 edition of Webster’s American Dictionary of the English Language)

Photo by
Jonathon D Colman

Selahv mentioned in a comment the disdain of the world for America – but there are in fact two distinct types of anti-Americanism. There is one kind which is just prejudice. There are people who disdain Americans simply because they are in a different “in group”, and it is fallen human nature to disdain out groups. Therefore every bad thing from America (fast food and sugary drinks for instance) is held against them. Every good thing (Clam chowder for instance) is ignored.

Such prejudice is hard to battle against, but it really is not Americans that need worry about this. The same people that hate Americans because of this prejudice probably have similar prejudices about any out group they care to consider.

However, there is another kind of anti-Americanism which is really anti-American policy, rather than the nation or its people. This is the feeling expressed in surveys that suggest people across the world believe that America is the biggest threat to world peace. This feeling comes around because of the gun boat diplomacy of one or other American administrations.

The Opium Wars

Note that America is no different from other nations here. In the 19th Century, the UK fought two wars against China to force them to accept the trade in opium. The drug was legal in the UK at the time – used as a seditive – particularly for gripey babies! But China banned the drug, citing public morals as the reason. After an incident when Chinese authorities boarded British ships and confiscated smuggled opium, a contingent of the British navy, including the new “iron clads” steamed into China. The fleet was larger than anything the Chinese had expected, and the first opium war was quickly lost. The peace treaty opened up a number of Chinese ports and ceded a lease on Hong Kong island to the British.

If you asked at that time who was the biggest threat to world piece, the answer in Shanghai would no doubt have been “the British”.

All countries act out of self interest most of the time. The thing that people dislike about American policy is its willingness to flout international law and order to pursue its self interest. Failure to become signatories to the ICC, arming of Israel as they kill people in Lebanon, The invasion of Iraq, support of regimes that persecute their own people, the arms trade, sidelining the UN and excessive use of the veto when the issue concerns client states, failure to ratify the Kyoto protocol – the list goes on (and these are just the recent examples).

But whilst I personally have a problem with all of these policies, I am not personally against Americans. (Indeed I am opposed to much UK policy for very similar reasons, but I am not anti-British).

Iraq

Selahv was speaking about Iraq, so the question is: how does this help Iraq?

We are where we are, and Iraq is suffering. What can we do? Cut and run? That would cause the disintegration of the nation. Stay the course? There is no sign that this strategy will ever succeed.

We pray for peace in Iraq – and we pray for wisdom and humility in our leaders. Particularly the humility to go to the United Nations and ask for help. If the occupying force could be replaced with a peace keeping force, and if we gave up our claims to Iraqi assets, just as we forced Russia and France to give up their claims, then there may yet be a hope for this country.

It would take a miracle for the US to willingly humble themselves and pursue this problem through the UN. It would take another miracle to see the policy succeed, and peace finally come to the nation of Iraq.

But fortunately, I believe in miracles.

if my people, who are called by my name, will humble themselves and pray and seek my face and turn from their wicked ways, then will I hear from heaven and will forgive their sin and will heal their land.

2 Chronicles 7:14

When Mr Spock says something is logical in Star Trek, what he often seems to mean is that something is common sense in som ultilitarian way of thinking. Thus “The needs of the many outweigh the needs of the few” is a clear utilitarian statement.

What he does not do is couch everything he says in terms of formal logic. And there is one very good reason why that may be a good thing! There is a principle in logic known as “ex falso sequitur quodlibet” – from a contradiction, everything follows. What this principle tells us is that if there is a single inconsistency of the form “P is both true and false” (a negation inconsistency), then every other proposition can be validly implied. If such a contradiction is allowed, then essentially everything is true.

Here is the proof:

1. P and P’ (that is, P is both true and false)

2. P (therefore P is true)

3. P or Q (Either P is true or Q is true)

4. P’ (P is false from 1. above)

5. Q (from 3. If P is false, Q is true).

But that is nonsense, you say – because perhaps Q has nothing to do with P. Hold that thought, because the other problem is what propositions are actually both true and false?

Well let us suppose that I am standing in the doorway of a room. One foot is in the room, and one foot is out. Am I in the room or not? You could argue that it is both true and false that I am in the room. Let us apply the proposition to the proof above:

1. I am in the room AND I am not in the room

2. I am in the room

3. It is therefore true that either I am in the room or black is white.

4. But I am not in the room

5. Therefore, from 3 and 4 I can see that black is white.

(And, as Douglas Adams pointed out, I shall now go and get myself killed on a zebra crossing).

But the point here is not that we can really prove anything, but that we don’t instinctively think logically. We allow that some things can be kind of true and kind of false, and we don’t actuall accept step 3 in the above argument. If a proposition has nothing to do with another, then why should its negation inconsistency imply the truth (and simultanously the falsehood) of the other proposition?

Human brains are wired up to be “paraconsistent”. Paraconsistency is a type of logic that ignores or removes the ex falso proof, often by insisting on the relevance of conjoined propositions. Whether we strictly need paraconsistent logic is a whole larger debate, but we need to bear in mind that our own thinking is more relevance based than strictly logical. And that is, perhaps, a good thing.

Over several months of last year I reposted some essays I had written on the book of Joel. These formed a series which you can find using the “Joel” tag on this site, but now for the first time here is a table of contents for the whole series:

1. Joel 1:1
2. Joel 1:2
3. Joel 1:3
4. Joel 1:5
5. Joel 1:7-13
6. Joel 1:14
7. Joel 1:15-19
8. Joel 2:1-11
9. Joel 2:12-13
10. Joel 2:13-14
11. Joel 2:15-16
12. Joel 2:17-18
13. Joel 2:19,21
14. Joel 2:22-25
15. Joel 2:26-27
16. Joel 2:28-29
17. Joel 2:30-32
18. Joel 3:1-3
19. Joel 3:5-8
20. Joel 3:9-13
21. Joel 3:14
22. Joel 3:15-21

“We have no interest in oppressing other people. We are not moved by hatred against any other nation. We bear no grudge. I know how grave a thing war is. I wanted to spare our people such an evil. It is not so much the country; it is rather its leader. He has led a reign of terror. He has hurled countless people into the profoundest misery. Through his continuous terrorism, he has succeeded in reducing millions of his people to silence. The maintenance of a tremendous military arsenal can only be regarded as a focus of danger. We have displayed a truly unexampled patience, but I am no longer willing to remain inactive while this madman ill-treats millions of human beings.”

In hindsight we may argue that some of these threats regarding the military arsenal were over-estimated. But who can deny that the case for war was adequately made in this speach?

I will leave it as an exercise for someone to work out which great world leader said it, but in the same vein, he also said the following:

“By the most brutal methods of terrorism, a regime sought to maintain an existence that was condemned by the overwhelming majority of its people…I have tried to persuade the responsible authorities that it is impossible for a great nation, because it is unworthy of it, to stand by and watch millions belonging to a great, an ancient civilized people be denied rights by their government

There are a number of sites around which retell a piece of naval history. For instance this one on myspace:

It was necessary to keep a good supply of
cannonballs near the cannon on war ships. But how to
prevent them from rolling about the deck was the
problem. The best storage method devised was to stack
them as a square based pyramid, with one ball on top,
resting on four, resting on nine, which rested on
sixteen. Thus, a supply of 30 cannon balls could be
stacked in a small area right next to the cannon.

There was only one problem — how to prevent the
bottom layer from sliding/rolling from under the
others. The solution was a metal plate with 16 round
indentations, called a Monkey. But if this plate was
made of iron, the iron balls would quickly rust to it.

The solution to the rusting problem was to make Brass
Monkeys. Few landlubbers realize that brass contracts
much more and much faster than iron when chilled.
Consequently, when the temperature dropped too far,
the brass indentations would shrink so much that the
iron cannon balls would come right off the monkey.

Thus, it was quite literally, cold enough to freeze
the balls off a brass monkey. And all this time, you
thought that was a vulgar expression, didn’t you?

Similar stories can be found at Life with Larry and The Gray Monk. The latter even purports to have a picture of one of these.

The problem is, no such ships fittings ever existed.

The point I want to make is that we cannot always rely on the popular
explanations, just because someone we deem to be an authority has
proffered the information, and when we hold something to be true, it
is often necessary to undergo rather more research than to simply ask
a historian friend (or local pastor, or church website or whatever),
to verify that this thing is actually true.

You see, this explanation is wrong on
several points:

1. Stacks of cannon balls were held in garlands, not monkeys

2. These stacks were made from wood, attached to the edge of the ship. The balls were not piled in stacks, but each seated in the garland in such a way that they would not come loose when the ship was pitching and yawing at sea.

3. The thermal coefficient of expansion is such that, taking some
   reasonable values for the size of the brass plate and the size of the
   cannon balls, and allowing that they would not be stacked so
   precariously that they would fall at the slightest touch, let alone
   the movement of a ship’s deck, it has been calculated that the
   temperature would need to dip to minus several thousand degrees
   celsius to cause the stack to collapse (and we don’t really need to
   consider anything past absolute zero, obviously). A few degrees
   Celsius would not have a noticeable effect on the stack – it may not
   even be measurable.

4. There are no sources that verify the story. It seems to be a recent
   invention.

Another, slightly more plausible story is that the phrase referred to freezing a ball on a brass monkey. In this version, brass monkeys are lifting gear on ships used to raise cannon balls to the gun deck in the place of powder monkeys (small and agile boys who would fetch the gunpowder from the ship’s magazine in times of battle). The argument then is that the lifting gear (made from brass, so it did not rust) would get covered in saline sea water. In times of extreme cold, the water would freeze. A cannon ball would then be placed on the lifting gear, and because of its weight, the pressure would briefly melt the ice – but being so cold, the ice would re-melt by the time the ball was lifted to the gun deck. Thus the weather was cold enough to freeze the ball onto the brass monkey.

Sounds better, but it is also implausible, because:

1. I cannot find any clear evidence that such lifting equipment existed and was called a brass monkey.

2. Lifting gear for ships certainly did (and does exist), but why for cannonballs? Powder monkeys fetched gun powder from the magazine, hidden deep in the ships hull, behind a dampenned “fearnought screen”, because the worst thing that could happen in a sea battle would be to get so much as a spark in the magazine. Thus powder monkeys fetched powder on a just in time basis for safety. Cannon balls, on the other hand, were kept near the guns. Being large lumps of iron, there was no danger these would explode! Thus no lifting equipment required.

3. There are no sources that back up this explanation either.

The only source I have ever found was a secondary source that
suggested a monkey was a type of cannon. [The concise OED cites “Art,
Rendition Edinburgh Castle”, published 1650 which refers to “28 short
brass munkeys, alias dogs”. This would put the term in the civil war,
but the cannon, and not the ball or the stack is meant. I don’t have
any access to the original source material].

Thus all I am really certain of, regarding this phrase, is my ignorance.

But that is the point: We often believe things on trust. These blog writers have trusted some information they have been given about this term. I likewise have believed a similar explanation in the past.

But there comes a time, when a subject is important enough to us, that
we must move forwards – verify what we know, and treat critically that which
we believe.

And this is true in all walks of life. For instance, in our churches, we can go so far by
listening to the teachings of our church leaders, but how do we know
that the teaching is true? How do we know that a certain doctrine is
held by us to be correct, because it really is true, rather than
simply because we have been told it is true? (Yes, we can look at scripture – but my point is : how do we know that the interpretation we have accepted of that scripture is true)

Often we need to look past what we are told by people we trust, and
actually evaluate information as well as we are able from the primary
sources, or (if that is impossible) from secondary sources who do not
have a bias towards our own viewpoint.

Now this last matter is crucial, for if I read the works of a certain
respected preacher (Billy Graham perhaps), and I say, “yes, he is
quite correct on the need for evangelism” and such like, but then “he
is in error on the Holy Spirit”, then all I am saying is that I like
Billy Graham’s ideas when they agree with mine.

But if I read all he says on the Holy Spirit, and say “is his view
consistent?” then I am setting prejudgement aside, and exploring the
issue for myself.

We can do this with Brass Monkey’s, and we can do it with Christian
Doctrine. We can do it with current affairs and politics too.

When we do it well, I think we move closer to an appreciation of truth.

Regular visitors to this site would be forgiven for thinking they have clicked their way into a time warp, with all posts and comments after April 1st missing!

The posts will be back soon.

My hosting service suffered a disk crash last night. Well, these things happen. However, in proof of Murphy’s Law (if anything can go wrong, it will go wrong), it seems that their 24 hour backup overwrote the previous 24 hour backup with corrupt data.

So thus far, they have restored this site from backup to 1st April. It is up to me to do the rest (but never fear – Google has cached the posts, so I can get them all back including – I hope – the comments. It may just take me a while to do it all).

Oh well! Perhaps a timely reminder that if you want a secure backup of your blog – you are better off doing it yourself.

(Actually, I backed this blog up just last week when I upgraded the version of WordPress… something I will no doubt have to do again now! The only problem is, I left the backup on the server! Doh!!!)

The latest version of Ubuntu Linux has now been released. Feisty Fawn can be downloaded from the Ubuntu Site. You can also download Edubuntu’s Feisty Fawn release. This version of Ubuntu is loaded up with open source educational software and has a clean looking but appealing interface to it. If you want to set up a system for the kids, this is the version to use.

Ubuntu has rightly become one of the most popular Linux distributions, and here (in my opinion) is why:

- Everything is free. (Well this is true of all Linux distros more or less – although some hide the freeness a bit, but it is such a good reason to use Linux over old fashioned Operating Systems, it is worth mentioning)
- Sane Package management using APT. Installing new packages is really child’s play.
- Debian based (which is why the package management is so good)
- Free CDs are available
- Supported by a benevolent billionaire – this distro is not going to vanish like some have done
- Desktop neutral. Gnome or KDE? You choose. Kubuntu is released alongside Ubuntu.
- Focus on education with the edubuntu distro
- Well designed
- Things just work. (Well perhaps not quite as well as Apple systems just work – yet… but moreso than any other Linux I have used. This is the distro you can give to a novice user and know they will do better than with a Microsoft offering)
- Multilingual. This is an international project, and the internationalisation work shows through
- No viruses, bsods, annoying warnings etc. Just the security and stability of a Unix core. A lesson that Steve Jobs took to Apple with OS X’s Darwin core

So if you didn’t quite get any of the above, don’t worry. Just go and get Ubuntu. get the live CD and try it out. Install it on the old computer in the kid’s “office”. One way or another, give it a test drive… it’s not scary!