Kategoriarkiv: Science

Vart tog alla bin vägen ?

Läste i Scientific American om det man kallar CCD (Colony Collapse Disorder) och den senaste forskningen om detta. CCD handlar om att extremt många bin plötsligt dör utan att man först hade en aning om varför, framför allt sker detta i USA men också i Europa. Det handlar om allt från 25% till 90% av alla bin beroende på vilken region man ser på. Detta är naturligtvis väldigt allvarligt eftersom bina används för att pollinera en mängd grödor som används som mänsklig föda.

Tydligen har man nu kommit fram till vad som kan vara orsaken eller i alla fall en del av orsaken. Det har visat sig att i de flesta kolonier som genomgår CCD har man påvisat ett virus IAVP (Israeli Acute Paralysis Virus). Det som jag tycker var intressant var att man i artikeln pekade ut att USA har haft förbud på import av bin från andra länder ända sedan 1922 och fram till 2005 då påtryckningar från bi-industrin om att man behövde mer bin gjorde att man hävde detta importförbud och började importera bin från Australien till USA.

Image by: Antonio Machado (CC - by-nc-sa 2.0)
Image by: Antonio Machado (CC – by-nc-sa 2.0)

Man tror att dessa importerade bin kan vara vad som introducerade IAPV till USA. Tål att tänka på att man inte ska leka med naturen hur som helst; den kan slå tillbaka värre än man kunde tänka sig. Ett annat problem nu när viruset är introducerat är att bin inte kan vaccineras eftersom deras immunsystem inte fungerar som hos oss däggdjur. Men man forskar på om man kan odla fram bin som är resistenta mot viruset. Biodlarna har också börjat använda sig av tekniker för att förhindra spridningen av viruset så mycket som möjligt t.ex. genom att desinficera kupor innan man låter nya kolonier flytta in, och man har börjat ge bina extra tillsatser eftersom de ofta får pollinera enorma fält av den samma grödan vilket gör deras kost extremt enahanda jämfört med vad vilda bin får.

Som exempel på vad bin betyder är värdet på odlingen som till fullo är beroende av pollinering från bin i USA mer än 15 miljarder dollar (~120 miljarder SEK / ~100 miljarder NOK).

Ferrofluid disaster

Just for fun I bought some ferrofluid to play with. It’s quite cool to see those spikes when moving a magnet around. Unfortunately even though I decided to try to be careful (because this liquid can stain things it get in touch with) I managed to screw up this experiment badly 🙂 I had poured the liquid into a different container (a glass) to experiment with it but when I was done and was going to pour it back into the original glass bottle I forgot that I had put the magnet a bit too close to the bottle (yes that was obviously stupid, I know) Suddenly they smashed together like a magnet do when it’s close enough to something it likes to stick to, and SPLAT !! I got ferrofluid all over my face and around in the room… I fortunately managed to avoid my eyes, and I managed to get most of the stains out of my face…. Well so now I only got to play with it once 🙁 , but well it was quite an exciting single experiment !.

I read on the bottle that it’s relatively safe, whatever they mean by ”relatively”. Too bad I had to wait for weeks to get this small bottle just to splash it all over my face…

But well, I also bought several other magnet toys so I have things to play with.

I might put up a small video of the ferrofluid experiment later. Unfortunately I had turned the camera off when the incident happened so you can’t see that 🙂

Pollution

During the Olympics in Beijing there have been quite a lot of discussion about the bad air in Beijing. And as I have myself visited Beijing several times I can say that the pollution is something that you definitely notice and can be quite bad at times. It’s quite boring when you do not see the blue sky for many days in a row. But it’s also shifting a lot, suddenly the air is very clear.

By the way here is an image of me in front of the olympic stadium which was under construction about one year ago:

There are official measuremnts of the air quality in Beijing that can be seen at MEP, while both BBC and Associated Press are making their own measurements.

The figures differs a bit and of course there can be big local variations, but until now AP has measured an average value of 326 micrograms per cubic meter of PM10 which is the most common measurement for air pollution. You can read more about PM10 at Wikipedia but one reason for importance of this measurement is that it measures particles with a size smaller than 10 micrometers, which is small enough to settle in the lungs and cause health problems. BBC’s values are a little lower with maximum values around 300, also according to BBC the yearly average is around 89. The official government data is around 160 under the olympics so far. Nevertheless it can be interesting to compare these values with other cities and your own local area.

BBC also mentions that the yearly average for London is 21. The most polluted city in the world, Cairo has a yearly average of 169, thats almost double the average of Beijing.

I found an article with numbers from Linköping in Sweden which is not far from where I grew up, there the numbers for the yearly average ranges from 18-26 depending on location in the city. Perhaps the numbers can’t be compared, but just looking at them it seems that London and Linköping is equally polluted, I find that hard to believe but anyway they are far from Beijing. In Sweden the yearly average can not be above 40 without actions being taken.

Looking at the city where I live (Oslo, Norway) one can see that the yearly average is around 25, and the report I looked at actually had data back to the 1970’s and it’s interesting to note that the PM10 values for Oslo are now only a third of what it was then, the average for 1971 for example was 74. In the 1980’s it was around 40-50, in the early 1990’s around 30. The same report also looks at SO2 where the measurements go back to the 1950’s with values around 300-400 micrograms per cubic meter, and in the early 2000’s the values were down at only 4-5 micrograms per cubic meter. NO2 was also down by the way. I was not aware that the air is so much better now (at least when looking at those three pollutants) then a few decades ago, interesting… But I am just looking at some numbers, how much of an improvement this really means I can’t say. Anyway all reports about Oslo and daily measurements can be found at luftkvalitet.info.

Well enough numbers and measurements, I am going to watch some Olympics instead 🙂

The barometer problem

I found this story on another blog:


Some time ago I received a call from a colleague. He was about to give a student a zero for his answer to a physics question, while the student claimed a perfect score. The instructor and the student agreed to an impartial arbiter, and I was selected.

I read the examination question: “SHOW HOW IT IS POSSIBLE TO DETERMINE THE HEIGHT OF A TALL BUILDING WITH THE AID OF A BAROMETER.”

The student had answered, “Take the barometer to the top of the building, attach a long rope to it, lower it to the street, and then bring it up, measuring the length of the rope. The length of the rope is the height of the building.” The student really had a strong case for full credit since he had really answered the question completely and correctly! On the other hand, if full credit were given, it could well contribute to a high grade in his physics course and to certify competence in physics, but the answer did not confirm this.

I suggested that the student have another try. I gave the student six minutes to answer the question with the warning that the answer should show some knowledge of physics. At the end of five minutes, he had not written anything. I asked if he wished to give up, but he said he had many answers to this problem; he was just thinking of the best one. I excused myself for interrupting him and asked him to please go on.

In the next minute, he dashed off his answer which read: “Take the barometer to the top of the building and lean over the edge of the roof. Drop the barometer, timing its fall with a stopwatch. Then, using the formula x=0.5*a*t^^2, calculate the height of the building.” At this point, I asked my colleague if he would give up. He conceded,and gave the student almost full credit.

While leaving my colleague’s office, I recalled that the student had said that he had other answers to the problem, so I asked him what they were.

“Well,” said the student, “there are many ways of getting the height of a tall building with the aid of a barometer. For example, you could take the barometer out on a sunny day and measure the height of the barometer, the length of its shadow, and the length of the shadow of the building,and by the use of simple proportion, determine the height of the building.”

“Fine,” I said, “and others?”

“Yes,” said the student, “there is a very basic measurement method you will like. In this method, you take the barometer and begin to walk up the stairs. As you climb the stairs, you mark off the length of the barometer along the wall. You then count the number of marks, and this will give you the height of the building in barometer units.”

“A very direct method.”

“Of course. If you want a more sophisticated method, you can tie the barometer to the end of a string, swing it as a pendulum, and determine the value of g at the street level and at the top of the building. From the difference between the two values of g, the height of the building,in principle, can be calculated.”

“On this same tact, you could take the barometer to the top of the building, attach a long rope to it, lower it to just above the street, and then swing it as a pendulum. You could then calculate the height of the building by the period of the precession.”

“Finally,” he concluded, “there are many other ways of solving the problem. Probably the best,” he said, “is to take the barometer to the basement and knock on the superintendent’s door. When the superintendent answers, you speak to him as follows: ‘Mr. Superintendent, here is a fine barometer. If you will tell me the height of the building, I will give you this barometer.”

At this point, I asked the student if he really did not know the conventional answer to this question. He admitted that he did, but said that he was fed up with high school and college instructors trying to teach him how to think.


It’s just a story but I think it’s quite nice :-). It exists in many different variants, and snopes.com has dated the first known version of it to 1958.