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How to calculate wind chill

24 February, 2015 - 10:18

Wind-chill, windchill, wind chill factor, wind chill index is an estimate of how cold you will feel at a given air temperature when there is a wind blowing. It is a popular tool used by weather presenters to make you feel worse about going outside when it’s cold and windy! Seriously, if, for example, the reported air temperature (as measured by a thermometer housed in one of those white boxes with the grills, a Stevenson screen, or shelter) is -7 Celsius and the wind is blowing at a steady 8 km/h, then it will “feel” like it’s -11 Celsius. But why and how does one get from -7 to -11, 4 degress C cooler?


Here’s the physics and formula courtesy of Wikipedia: “A surface loses heat through conduction, convection, and radiation. The rate of convection depends on the difference in temperature between the surface and its surroundings. As convection from a warm surface heats the air around it, an insulating boundary layer of warm air forms against the surface. Moving air disrupts this boundary layer, or epiclimate, allowing for cooler air to replace the warm air against the surface. The faster the wind speed, the more readily the surface cools.” Additionally, skin sweats so air blowing on exposed sweaty skin will cause cooling by evaporation, but the likelihood of you sweating and then exposing your skin when you’re outside and it’s -7 Celsius is quite low…

The calculation used by the US and UK weather forecasters and meteoroligists for wind chill is quite complicated looking but relatively easy to implement with a modern calculator, although different regions use different units F vs C, mph vs kmh, so you have to make sure you’re using the appropriate formula. A neat chart (by RicHard-59 on Wiki) saves you the trouble of doing the calculations yourself, if you’re a common or garden weather presenter.

And, here’s a nice video description of wind chill that I first saw mentioned on the Free Technology for Teachers blog:

For pedants in Australia, it’s rare that a wind chill is observed, you might want to try “heat index” instead… ;-)

How to calculate wind chill is a post from the science blog of science journalist, photographer and musician David Bradley
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Is it okay to kick a robot?

12 February, 2015 - 15:34

By now, you’ve probably seen the astounding quadruped robots that have been built and demonstrated by Boston Dynamics. These machines run like four-legged animals and don’t seem to mind when their human companions give them a kick…hold on…give them a kick? Is that really the best example to set impressionable people watching the videos?

One could argue that it’s a machine, it doesn’t “mind” being kicked, if that demonstrates just how robust the software and servos are to disturbances in the forces around them. But, it is still quite a disconcerting thing to see. The next generation might be togged up with heads and fur, for instance, to make them look even more like animals, that would make for even more uncomfortable viewing, I reckon. And, then, of course, ultimately, such a robot might be endowed with artificial intelligence, sentience, even. Would kicking a bot that knows what you’re doing be moral?

This also raises another question. If we build sentient robots, would it be sensible to give them pain receptors? Would we want them to know to avoid things that might hurt. And, Asimov aside, might a robot in pain having been kicked feel that retaliation was the ethical thing to do from its perspective?

Is it okay to kick a robot? is a post from the science blog of science journalist, photographer and musician David Bradley
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Follow me, follow them

5 February, 2015 - 09:07

Not quite in the words of the 1978 Genesis hit “Follow you, follow me”, I took a look at Twitter dashboard and found that there is a neat Top 9 (don’t ask) of twitter users who a lot of people who follow @sciencebase also follow

sciencebase-followers@NASA · @NatGeo · @wiredscience · @TEDTalks · @Discovery · @ScienceNews · @neiltyson · @NatureNews · @guardianscience

Follow me, follow them is a post from the science blog of science journalist, photographer and musician David Bradley
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My first chemistry experiment #UnRealTimeChem

2 February, 2015 - 17:06

My choral friend Jo mentioned making “poisonous” orange juice when she was a nipper and giving it to a boy she and her friends didn’t like. Apparently, they crushed up some bits of plants, including foxgloves, which of course contain digitalin, the heart drug. Add enough of that to his OJ and they could’ve been in serious trouble. Just as well there was no belladonna (deadly nighshade) or monkshood (Devil’s Helmet or wolfsbane).


Anyway talking of serious trouble…as a kid I was always messing around with magnets and motors, batteries and bulbs, iron filings, little circuits, broken radios (well they were broken after I’d messed around with them), watches, telescopes, magnifying glasses and stuff. But, by aged 9 or 10 I’d taken my first foray into chemistry. I’d got hold of a little stoppered plastic vial and mixed up some washing-up liquid and water and added some of the 3-in-1 oil I usually drizzled on to the chain and into the little holes on the underside of my bike. I don’t remember what I was trying to do with this, my first chemistry experiment. Obviously, the mixture would have formed some kind of mucky emulsion. Hashtag #JuvenileAlchemy.

Anyway, I remember some snitch reported me to my teacher when they saw me shaking my vial behind the bike sheds (no, that is not a euphemism!). I got hauled in to see the headmaster, I think my parents were dragged in too. Of course, the vial with its gloopy contents was confiscated but not before the headmaster had a good sniff. I’m not sure what any of the adults thought I had been up to. I was just naively doing chemistry. Maybe they thought I was abusing solvents or sniffing glue or something, but at age 9 I didn’t even know that was a thing…

I almost certainly had an idea from a science library book, I used to read three or four each evening at that age. Anyway, the experience put me off chemistry for years and so I went back to messing with magnets (again, not a euphemism) and I seem to remember trying to make an electromagnet from a chunk of steel from my Dad’s toolbox and a bit of insulated wire that I jabbed into the wall socket…oh dear…did I mention I was a bit naive, almost electrocuted myself, needless to say. Still, at least I didn’t try to give anyone a heart attack with poisonous orange juice, eh?

*The photo isn’t me, by the way…

My first chemistry experiment #UnRealTimeChem is a post from the science blog of science journalist, photographer and musician David Bradley
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Predictive text: Darwin’s computers

21 January, 2015 - 10:05

Charles Darwin’s IBM computers

There are lots of quotes around attributed to the great and the good throughout the years, but often these are anything but direct quotes and in some cases turn out to have far more intriguing origins.

For example, the quote often attributed to Thomas John Watson, Sr. (1874–1956) who was chairman and CEO of International Business Machines (IBM) in 1943 had him as saying:

“I think there is a world market for maybe five computers.”


There are no recorded speeches nor documents that providence evidence for this as a quote from Watson. Indeed, the earliest mention of it was on the Usenet in 1986, although that may well have come from an article in the San Diego Evening Tribune by Neil Morgan, who wrote: “Forrest Shumway, chairman of The Signal Cos., doesn’t make predictions. His role model is Tom Watson, then IBM chairman, who said in 1958: ‘I think there is a world market for about five computers.’

It seems that Sir Charles Darwin (grandson of the naturalist) who was head of the UK’s computer research centre, the NPL (National Physical Laboratory) is probably the true father of the thought of this particular predictive text when he said in 1946:

“it is very possible that … one machine would suffice to solve all the problems that are demanded of it from the whole country”

But, The Yale Book of Quotations may have the truth about this particular misquote. Watson did indeed mention a market for only 5 computers, at IBM’s annual stockholders’ meeting in 1953, but he was referring specifically to the IBM 701 Electronic Data Processing Machine which had been touted to 20 potential clients but Watson reported that they only expected to get orders for five (they actually sold 18).

More on the myth on Wiki and on the Freakonomics site.

Predictive text: Darwin’s computers is a post from the science blog of science journalist, photographer and musician David Bradley
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Bait and Switch – a song

17 January, 2015 - 17:59

Don’t worry, you’re not going to be Rickrolled, despite the song title ;-)

Songs of Experience by Dave Bradley

Words and music by Dave Bradley, vocals, guitar, bass, percussion dB

Bait and switch

There was a key under-the-mat,
but you changed all the locks
There was a note deep in your pocket,
but no stamp for the box

I saw a light up in your room,
but your heart was like stone
And though you strayed out of the gloom,
there was nobody home

There was a seed inside the pot,
but no water for the bloom
There was food there on the table,
but no taste in the room

You wore a smile and a little more,
but you cried on the inside
And though you veil all that you feel,
there’s no place left to hide

When you turn about face
I can’t stay in that place
Switch and bait me
I know that you’re cunning

When I find the right pace
It’s the end of the race
Bait and switch
is the game that you’re running


Bait and Switch – a song is a post from the science blog of science journalist, photographer and musician David Bradley
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WebElements: the periodic table on the WWW []

Copyright 1993-2011 Mark Winter [The University of Sheffield and WebElements Ltd, UK]. All rights reserved.