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...the United States of America, of course. Hamish Johnston, editor of, has put together a neat little piece looking at where Nobel physics laureates start and end their days. There's no surprise on the net migration front - a huge flow from everywhere to the US. You can read Hamish's piece here. What the graphic doesn't indicate is when the award winner migrated (e.g. was it before or after their prize?) and multiple migrations - he just shows where they were born, and where they died or are currently living. 

The biggest 'loser' is Germany - in fact a whopping 13 German-born laureates left Germany (11 of them for the US, including Albert Einstein, and 2 to Switzerland) although World War II accounted for many of the migrations here. 

While 30 laureates have immigrated to the US, only 2 have emigrated including the 2011 'Australian' laureate Brian Schmidt

There's been some shuffling about within Europe too, the biggest winner of this being France, but that is insignificant compared to the large, thick arrow that heads westward across the Atlantic. 




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The Institute of Physics (IOP) has recently released "Opening Doors: A guide to good practice in countering gender stereotyping in schools" (You can access the report here and read some commentary at a recent IOP conference here.) Although funded jointly by the Government Equalities Office (now I'm sure such a thing didn't exist when I lived in the UK) and the IOP, the study is not confined to physics, nor even to science. However, given the gender imbalance in physics, the IOP has a strong interest in this. Also, given the low numbers of students studying physics at Waikato, it is something I have a strong interest in too.

The report covers many areas, such as careers guidance, staff training, tackling sexist language (whether it be conscious or unconscious), use of statistical data, and so forth. But the one that caught my eye was subject equity. What is meant by this is treating all subjects on an equal footing. Often, maths and science are given a label that says 'this is a difficult subject'. For example, that can be done by teachers (and parents, older siblings and so forth) telling students that they are hard, or sometimes by setting higher entry requirements than for other subjects - e.g. to progress from GSCE to A-level physics one might need an 'A', but to progress in English one might need a 'B'. Why does this matter? Because there is an increasing body of research that suggests that when a subject is perceived as 'hard', gender sterotypes are emphasized. That is, the minority gender fears failure much more so than the majority gender and consequently does not take the subject. At the 'Opening Doors' Conference, Prof Louise Archer (King's College, London) is reported as saying:

It is taken for granted that physics is hard and masculine, and that can lead to self-censorship and self-exclusion

In other words, work on the image of physics being hard, and the gender bias may diminish. Note that it's the girls and women who are actively choosing not to do physics, rather than the boys and men actively choosing to do physics that leads to the imbalance. Fix the gender issue and we won't lose the males in our school and university classes, but we'll gain females.

Now, this is highly relevant to physics at Waikato, which has a much higher entry requirement into its first year physics papers than it has into other first year science papers. We also have a tangled web of complicated pre-requisites to do our second and third year physics papers. In other words, the information  we provide prospective and current students implicitly says "physics is harder than other sciences".  And, as the IOP report talks about, when you have the label 'hard' against something, the minority gender fears failure and doesn't engage with it. So, as a very first little step (and I would emphasize that there is a whole lot more that needs to be done with the way we offer physics here at Waikato) we can bring our entry requirements into line with those into the other sciences. If the IOP has done its research well, we should, at very least, see more women taking physics at first year. 



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I've recently received the final report from the Conference Organizing company that looked after the New Zealand Institute of Physics (NZIP) conference, back in July. The report includes such things as the final accounts, the breakdown of who attended, and feedback from participants. It's the feedback that is particularly interesting. 

When we attend an event, it's usual to find a piece of paper thrust in front of us before we leave, asking for feedback. Nowadays, it's often an electronic form that comes to your inbox. And it's easy to ignore it. However, what we write is really valuable to the event organizer. How are they going to know what went well and what didn't go  well, unless people tell them? If something needs changing, the organizer needs to know about it. Likewise, if something was really appreciated, the organizer wants to know too - so they're not tempted to remove it for their next group of people. I've just had an email arrive asking for feedback on the metrology conference I went to last month. It would have taken about a second to hit the delete key. However, having been part of the organization of NZIP 2015, I know that any feedback I give will be very valuable to the organizers. Hence I took a couple of minutes to put some things down in words for them. 

So, what of the feedback for NZIP 2015? I'm fairly confident that several of the delegates will be reading this, so here's a flavour of the comments:

First the positives. (Actually, I would say ALL (sensible) feedback is positive feedback, since it helps to improve things. But by positive here, I mean things people thought went well or they appreciated.) There were many (eight, in fact) comments about how the conference was enjoyable and greatly appreciated.  It was fun to be at. For example:

I am glad I attended the conference this year (for the first time). The distance travelled and the days spent out of the school holidays was worth it.

Our choice of speakers went down well:

Thank you for such a well though out line-up of speakers

There were also many pertaining to the conference's ability to draw high-school teachers and university researchers together. For example...

As an interloper from a more chemistry-based focus, I really enjoyed the full participation of high-school teachers and the strong emphasis on teaching

Many people liked the venue (University of Waikato in Hamilton), though I wonder if these are locally based (Waikato, Bay of Plenty) participants who have endured many years with the NZIP conference located far away. There were equally those who didn't appreciate having a conference in Hamilton...

Now the not so good. By far and away the largest single theme was one over which we had little control: the food. 

Food was AWFUL and there was not enough

...and there were another sixteen comments along the same lines. We ran out of food on the first day. The reason the caterer's gave was uncomfortably erudite - there were too many males at the conference. The gender-imbalance in physics is of course a big issue in itself. I won't pursue that further in this entry. One relies on caterers to get it right, and in this case they were thrown by the uncharacteristically large appetites of the male-dominated physics population. 

Cost was another issue. Some thought the registration fees were too high, and others that airfares to Hamilton are too expensive (and therefore we should have held the conference in Auckland or Wellington, though presumably that comes at extra cost on accommodation). Setting registration fees is a real balancing act for a small professional body like NZIP. Conferences are expensive things to run. Getting good keynote speakers (which we evidently did) costs. But saving money on food (which we also evidently did, though perhaps inadvertently) isn't appreciated. For the record, we made a profit of nearly $4,000 for this conference, but that has to be put into perspective of a thumping loss (around $10k) made the previous time. I doubt many professional bodies of NZIP's size make money out of conferences in the long-run. If the fees are too high, we lose participants. If the fees are too low, we don't cover our costs. It is very much a fine line. 

There were comments regarding parallel streams. Some people like them (you get to choose which presentation to attend) but when there are two or more presentations that you'd like to be at that are scheduled for the same time it gets difficult.

It's a hard one, but there were several presentations on at the same time that I would have liked to have gone to.

Getting a programme together is hard work. It's like doing a seating plan for a wedding reception - it sounds easy until you actually try to do it. It's tied up with issues such as "how long should the conference be" (longer conferences mean more cost to the participants in time and money) and "how much free time should there be in the conference?" We had comments on both those issues too. It certainly isn't helped by the extra-ordinary ability of academics not to be able to submit abstracts by deadlines, or even extended deadlines. (And we moan at students who don't submit on time...) 

So where is NZIP going for 2017? Who will be the keynote speakers? What will the fees be? What strange concoction of after-dinner entertainment will be proposed? All of these questions are, as far as I know, still undecided, If you have thoughts, please let NZIP know. 






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We have a spring-loaded umbrella at home. The idea is that you press a button, and it automatically springs into shape - its shaft springs out and the canopy unfolds. I've often wondered about the wisdom of such a mechanism and thought what would happen if it went off in an inconvenient confined space, such as a shop packed with expensive china ornaments.To reset, after use, you press the button again to fold up the canopy, but then need to reset the spring mechanism by pushing half the shaft inside the other half. It's that resetting bit that got me yesterday morning. On coming back inside the house after tending to the chickens I tried to collapse and reset the umbrella, but didn't push the shaft hard enough for the mechanism to engage. Instead, when I let it go, the shaft sprung back and hit me in the face - hard enough to draw blood. 

Fortunately my injury was entirely superficial (but it hurt!) and I won't be appearing in the 2015 ACC funny list for the craziest effectors of injury*. 

So how hard did it hit me? Let's do a quick estimate. First, how much energy is in the mechanism when enabled? This depends on the force required to push the spring into place and the distance one needs to push it. The latter is the easy one - about 20 cm. The force is harder to estimate. Imagine putting the umbrella on its end and gradually applying an increasing weight to its shaft, until the spring is fully compressed. How much needs to be applied? About 3 kilograms of mass, maybe. That's 30 newtons of force. So the energy stored in the spring is the force times the distance compressed, divided by two. The factor of half comes from the fact that as the spring compresses the force required increases linearly with the compression. So that gives us about 30 newtons, times 0.2 metres, divided by 2, which equals 3 joules of energy. 

That energy stored in the spring got transferred to the kinetic (movement) energy of the shaft when I let it go. So, how hard did it hit me? One can do the calculation in reverse. About 3 joules has to be dissipated over a small distance as it hit me. Maybe I moved a couple of centimetres. So what force would dissipate 3 joules when acting over 2 cm. Divide 3 J by 0.02 m and we get 150 Newtons. 

That's the weight of 15 kg of stuff, applied through the end of the shaft, to my face. Imagine a suitcase perched on top of the umbrella with the other end supported by my lower lip. Ouch.  The force is substantially larger than that I need to compress the spring in the first place, because it is dissipated over a much smaller distance. However, the suitcase comparison shouldn't be taken too far because the umbrella force was applied only for a very brief period. 

I have now learned to be a bit more careful when resetting the umbrella. 

*But let's not forget the 1978 umbrella-assassination of Bulgarian dissident Georgi Markov on Waterloo Bridge in London



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I take back what I said last week about amazing vehicle management systems on milk tankers. Last night a GPS took a forty-two tonne tanker onto the three-tonne-rated Cambridge High Level Bridge, in what could have been a catastrophe. The bridge, with which I am very familiar, was designed for people, horses-and-carts, and the occasional small mob of sheep or a few head of cattle. Out of necessisty (witness the traffic mayhem this morning)  it now takes cars. NO trailers, and absolutely NO trucks. It's not as if it's difficult to see the warning signs - the approach is designed to slow you right down before you get onto the bridge. But then, if the GPS tells you to go that way, what are a few large, conspicuous warnings on a narrow 117 year-old bridge other than a mere distraction. 


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Someone has to do it. There are laws in NZ pertaining to how the stated  volume of bottled liquids corresponds to their actual volume.  If, for example, you are selling beer in 375 ml capacity bottles, you need to make sure that your bottling plant is working to the NZ definition of what 375 ml actually means. In a bottling plant, the volume of liquid supplied to a bottle is often controlled by back-pressure. This is the same mechanism that causes a petrol-pump to cut-out when your tank is full. Generally speaking, it gives an adequate measure of when your bottle is filled with the appropriate amout of liquid. 

There will always be variations in the amount supplied. One bottle will never contain exactly the same amount as the next. So for trading purposes, 375 ml must have an appropriately practical definition. One of the talks at the Measurement conference last week, by Chris Sutton, looked at some of the issues behind this. Chris talked about the current law - I didn't write this down - but it includes such things as the average volume per bottle not being less than 375 ml when sampled over a certain number of bottles, and restrictions on just how much below the stated volume of any individual bottle can be. However, there's no point having any laws or industry standards if it's not possible to measure it. 

And there is the problem, really. Measuring volume isn't an easy thing to do. One could sample lots of beer bottles and tip out the contents into calibrated measuring containers. Such things exist. The problems with that, however, are that the process is slow and your small craft brewery doesn't enjoy having a significant fraction of its output being destroyed in the process of checking it's obeying the law. Consequently, it's actually better to measure volume by using mass and density. Here, one first would measure the density of a sample of the beer being fed into the bottling line. Then a number of empty bottles are chosen, and accurately weighed. The bottles go back into the production line, and after they are filled they are weighed again. That gives the weight (and therefore mass) of the beer that's been added. Knowing the density of the fluid inside, one can then do a simple calculation of volume = mass/density to find the volume in each bottle. That way, the volume is measured without significant loss of the end product. That keeps the small breweries happy. 

Except, there is a problem with this. That's the carbon dioxide content. The density of the beer changes with the concentration of CO2 dissolved. So when we talk about volume of beer, do we mean with or without the CO2? Currently, the most robust way of defining a measurable standard is for de-gassed beer. Get rid of the CO2 and then measure. But doing this is a destructive process - you don't get your beer back afterwards. So, how do we come up with a practical standard for the case of carbonated drinks  that keeps both the maker and the consumer happy? It's still an open problem. Answers to Chris Sutton, please.


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I'm currently at the Metrology Society of Australasia conference in beautiful Queenstown. For those that don't know, which might be most of you, metrology is the science of measurement. How do you measure things well?

At this conference, we've got presentations on measuring temperature, pressure, liquid volume (a surprisingly tricky one this - if you want to do it accurately, quickly and non-destructively), electrical properties, so on and so forth. There's lots of industry engagement here - unsurprising since making measurements well can make real differences in a company's bottom line.

For example, Richard Suckling from Fonterra talked this morning about some of the problems that Fonterra faces in terms of collecting milk from farms, and the measurement technology that is packed into each milk tanker. Milk tanker routing is a real example of a 'travelling salesman problem' - how do you optimise the route that a tanker takes to go between all its pick-up points? There's a lot of computer power that goes into doing just that - to ensure that the minimum number of tankers are sent out, they arrive within time constraints, with enough spare capacity to take on board the milk, but with enough weight on board already in the right part of the truck  to get traction of the more tricky farm tracks, be able to turn in and out of the farm safely and so on. Coupled with large seasonal changes in milk production, optimized tanker routing means lower fuel costs, and that's a huge saving. Then there's all the technology that goes into measuring just how much milk is being taken onboard at each farm, monitoring the temperature of the milk, taking samples for testing quality, and so on. This is just collecting the milk. He didn't go into what happens after that.

But for me the most interesting comment was regarding the colouring and finish of the tankers, because it has parallels with military stealth technology , the area in which I used to work. There was a time when the tankers were just shiny metal, but a series of night-time accidents changed that. Several incidents occured where cars (with headlights on) drove into the sides of tankers. The shiny metal just wasn't visible at night, even when illuminated with a car's headlights? Why? The shape was such that the large majority of the light from the car was reflected away from the car. Only a small fraction was reflected back to where it came from, meaning that the driver wouldn't necessarily see the large object straight in front of him. The current finish, including retroreflective paint and diffuse surfaces is much easier to see at night - and can be made into a nice attractive logo to boot.

This afternoon we had an industry 'site visit' to Gibbston Valley Winery, to check out the measurement technology involved in the wine-making industry. Sugar content, pH, yeast content, etc, all need to be measured (Or so some winemakers say. Others just go on 'experience'.) And there were lots of nice samples for us to 'measure' too...

I'm sure we'll get a good lot of talks tomorrow, too.



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In our first-year physics lab we have the following horticultural experiment. 


Here we have some bulbs growing on a rotating turntable. The array of five pots is placed on the turntable so that the centre pot is at the centre of the turntable; the left- and right-hand pots are at the perimeter.The turntable is rotating at about half-a-revolution a second. What happens as the plants grow?

Actually, this is a demonstration of centrifugal force just as much as it is a horticultural experiment. First the biology bit. Plants grow, pretty-much, towards the light. I'm sure someone will tell me the mechanism by which this happens, but for now I'll just state that as true. In this case, however, what is towards the light is constantly changing. The plants get equally illuminated from all sides. So we can take light out of the equation. 

The other direction plants grow is upwards. What do we mean by 'up'. It's against gravity. Again, someone will tell me the mechanism by which they achieve this (rather than sending their shoots straight down into the ground). But what is 'up' when you're on a turntable. 

Imagine you're standing on the spinning turntable. To remain 'upright' you'd have to lean into the centre. Why? In the rotating frame of reference, the one you're in, you experience centrifugal force pushing you outwards. You need to counter-act that. The same is true for the rotating plants. They effectively experience gravity as being downwards and a little bit outwards. Consequently they grow upward and a little bit inwards. Note how the centripetal force is proportional to the radius at which the plants are growing, so the ones on the ends of the line have more of a lean than the ones in the centre. (Unfortunately the left-hand plant as we see it has been a bit slow-off-the-mark, but you can still clearly see the lean.) Indeed, the central plant, sitting on the axis of rotation, experiences no centrifugal force and it grows straight upward. 

We can get a little more mathematical. The turntable takes T=1.7 seconds to do one revolution (I've just gone and timed it) and the outer plants are about r=20 cm off the axis. This means the centrifugal acceleration is given by omega squared times r, where omega is the angular velocity (= 2 pi / T). Doing the calculation we then get a centrifugal acceleration of about 2.7 metres per second squared outward. Compare this with the acceleration due to gravity, which is about 9.8 metres per second squared downwards. It's about a quarter the strength of gravity. So, for every four centimetres the outer plant grows upwards, it should grow by one centimetre inwards. A glance at the image will tell you that seems to correspond with what actually happens. 

Finally, then, a challenge to those who say centrifugal force is just something that you think is happening when you go round a bend in your car - it's not a real thing. Plants don't have a brain. They aren't just thinking they are experiencing centrifugal force. They ARE experiencing centrifugal force. 


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A colleague remarked to me yesterday, as we were trudging up the two flights of stairs from the tea-room to the third floor, "I'm sure they turn up the force of gravity in this building each year." I feel like that too, sometimes. However, I suspect it has more to do with the aging process that any changes in physical constants. 

But...what if...? What would life be like if gravity were say, double what it is now. How different would life be? There are many ways of tackling that question. So I'll phrase it in this way. Imagine that there's another universe in which a similar-sized and atmosphered Earth exists, but where the force of gravity is double what it is in this universe. What might life look like on that Earth?

First, I need to say that the 'Earth' itself would be different in many ways. The atomosphere could be very different, the structure of the earth very different, the shape and size of mountains very different, etcetera etcetera. But let's narrow it down, and suppose the Earth itself is the same, It's just the force of gravity that's different. What would people look like? (Again, assuming this new Earth evolves people). Well, we'd need stockier legs. Why? If we double our weight, we'd need more surface area in our leg bones to support it. We'd start looking more like elephants. 

But, that's just one option. An alternative is that double-gravity-Earth-humans could look exactly like our-Earth-humans, but with all our dimensions halved. (Yes, with a bucketful of assumptions.) How does that work? The stress in our shin bones would be given by the weight supported by the bone, divided by the area squared. Now, our weight would scale as the force of gravity times our volume; the latter scales with our dimension (e.g. height) cubed. But the surface area squares as our dimension squared. So the stress in our shin bone would scale with gravity times dimension cubed divided by dimension squared, which is gravity times dimension. If gravity doubles, and our dimension halves, we our back to the same stress. So, our sister-beings could look exactly as we do, but just be half our height (and half our width). Rather like hobbits, minus the furry slippers. 

However, that's not the same thing as saying that life for them would be the same, just on half the scale.  Let's consider the double-gravity-Earth-Olympics. Would they be able to do the same sports that we do, just at a different scale? At first glance, it might seem yes. Take running. Half the size, and (roughly speaking) you'd expect them to run slower than us - they cover less ground with every leg swing. (Although they'd also be able to swing their legs quicker.)  So they'd still be able to have running races, but for them the 100 m would seem like a longer distance than it would for us. To compensate for this, they'd make their track a bit shorter.

But what about the pole-vault? This event is a great example of physics. The faster you run with the pole, the more it bends when its planted in the... what is it called?....and the more spring force upwards it gives you. Basically, it comes down to kinetic energy of the athlete being converted to gravitational potential energy, via elastic potential energy in the bent pole. How would this work in the double-gravity-Earth-Olympics?

Let's just estimate the height one can pole-vault by a simple equating of kinetic energy to potential energy. That gives us mv2/2 = mgh, or h = v2/2g, where m is the athelete's mass (note how it cancels in the expression for h), v is his or her velocity on the run,  g the acceleration due to gravity, and h is the height they vault  to.  If we double g, h will halve, so long as v stays the same. But  our diminuitive sister-humans will be running slower than us. So v doesn't stay the same, it's lower. With g doubling, that means h, the height of the vault,  is more than halved. So, measured in terms of how many times their height they can vault, it will be less that us. The pole-vault event isn't then just a halved copy of ours - it would look different. 

One can take this line of thinking a whole-lot further still. In a double-gravity-Earth-Rugby-World-Cup, Namibia would be hot favourites, for example. But I'll leave it there.

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I read the 'Rental Nightmare' article on last night. Some of the stories are horrific indeed, and I'm reasonably confident that the writer has deliberately sought out the worst situations rather than the most common situations. But one cannot deny that a great deal of housing in New Zealand is sub-standard. In housing-deficient Auckland, in particular, families are forced into cold, damp homes because there is nowhere else they can afford. 

I've been in NZ eleven years now, and I have still to wrap my head around why this is. It seems that up to the 1970's, houses were designed with three underlying assumptions: 1. New Zealand has a warm climate, 2. New Zealand has a dry climate, 3. Everyone needs a large, detached house. While the first is arguably true for parts of the country for parts of the year, the second is true almost nowhere and unfortunately the consequences of the third are coming home to roost as Auckland has to struggle with the concept of high-denisty housing inside the city or yet more expansion on its already sprawling fringes. 

So New Zealand is left with uninsulated, poorly ventilated, high-surface area housing, in which we put our most vulnerable families. 

Back to the article. As I said, I expect sensationalization in an article like this. But I do take issue with the comment from Andrew King, whom the article says is representing the Property Investor's Federation. The article reports him as saying (note that this is the words of the reporter, not Andrew King's direct words):

He says tenants often do things that encourage mould, such as not heating homes and drying clothes on clothes racks.

Not heating your home isn't clever. But there's only so much money you can fork out on power bills, and when the house isn't insulated the benefit you get per dollar spent on heating isn't high. So it's not at all surprising that some houses are left unheated. Money is better spent elsewhere. 

But drying clothes on clothes racks? Where do you expect people to dry them? Outside on a washing line? Try doing that in Hamilton yesterday, or, I suspect having seen the forecase, for the next week. What about in a dryer? First, that assumes the tenants can afford to run a dryer, and that, secondly, the dryer is properly vented to the outside of the house. Putting a hole in the wall for a permanent vent is the landlord's job. How many of them make that a reality? Venting the air into a room puts the same amount of moisture into the room that drying on a rack would do - but in a much shorter space of time. 

So what's the problem with drying clothes? Imagine a load of washing that leaves your machine after a wash and spin. How much water does it contain. A large load might contain around three kilograms of water. (That's my estimate based on the weight of the laundry basket when laden with wet clothes compared with when the clothes are dry.) All that water needs to evaporate. How much air is needed to do that?

Let's assume you are drying at 18 Celsius (in a student flat in Dunedin in winter, yeah, right). How much water can the air in a room hold? Consulting a psychrometric chart, you can see that at a relative humidity of 100% (the air holding as much water as it can) air can hold about 13 grams of water per kilogram of dry air. Roughly speaking a kilogram of dry air is about a metre cubed (1000 litres) in volume, so that's about 13 grams of water in a thousand litres of air. So to soak up say three kilograms of water, you need about 250 thousand litres of dry air. The ambient air almost certainly isn't dry - if it's a relative humidity of 70% outside, the air is already containing 70% of all the water it can hold. So that boosts the requirment to around 800 thousand litres of air needed. Call it a round million litres of air to dry your load of washing.

Now, a small room (3 m x 3 m x 2 m) would be about 20 metres cubed, or contain about 20 thousand litres. You need therefore about 50 rooms-worth or air to provide enough capacity to suck the water out. If you dry your clothes in that room (and they will dry eventually) it helps considerably if the room is well ventilated. That allows the damp air inside to exchange with the slightly less damp (this is Hamilton) air outside. 

So where does condensation come from? Let's suppose you hang out your clothes on a rack on an 18-degree cloudy afternoon, with 70% relative humidity. Your house is uninsulated (and unheated), so it's also 18 degrees inside your laundry-room. You won't get condensation. The psychrometric chart will tell you that the dew point is about 15 C - that's the temperature below which air of this humidity will start dropping its water content. Your walls are at 18C so it's not a problem. But as you head through the night, the temperature outside drops. The clouds clear, and you go down to 5 Celsius, say. Your house is uninsulated, and your interior walls find themselves at 5 Celsius, with a room full of moisture laden air. The walls are well-below dew point, and now the water condenses onto them. 

The problem then? The house is uninsulated and poorly ventilated. Fix the fundamental problem (a bad house), the walls stay above dew-point, and then there is no reason why you shouldn't dry your clothes inside when it's a damp day. 





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