Why does dust form dust-balls?
31. okt 2003 06:00
Everyone has been bothered by dust-balls from time to time, but few of us have spent several days observing their exciting lives, unlike the pupils of primary 6b at Ulsmåg School in Bergen.
This year’s winner of the ”Nysgjerrigper” prize:
Why does dust form dust-balls?
I was just wondering!
No matter how much we wash and vacuum-clean the house, the dust-balls always seem to come back. A mother wonders where they come from. The primary 6 pupils decide to do a bit of detective work to find the answer to the question: “Why does dust form dust-balls?”
Why are they like this?
The pupils based their work on four likely hypotheses (a hypothesis is a suggested explanation that can be tested experimentally:
- Static electricity makes the dust gather into “balls”.
- Dust-balls form according to the same principles as snowballs.
- Dust-balls are whirled up by draughts and settle down in “calm” areas of the room.
- Heating cables attract dust.
Draw up a plan for the investigation!
Obviously, the project needed to concentrate on dust. The young scientists wanted to question experts and have the dust analysed in order to find out how a dust-ball is built up. And they wanted to carry out advanced “space research” by looking at how the dust-balls develop and move around the room.
Looking for information!
Four lucky (?) pupils were allowed NOT to wash or vacuum their rooms for six weeks so that they could study the lives of the dust-balls. They followed their movements by marking existing dust-balls with tiny brightly-coloured feathers. The dust-balls were given names like “Goldie” and “Greenie”, and the pupils drew accurate plans of their rooms so that they could document the dust-balls’ travels for the six weeks of the experiment.
Each pupil kept a logbook, one of which contains the following entry: “February 20th: Today I have noted the first movements of my dust-balls. Greenie has found a cosy corner beside the radio. Bluey has pirouetted to the wall. Lilac has done the same and is only about 15 cm from Bluey”. Three days later: “February 23rd: Bluey and Lilac have fallen in love”. And again: “February 26th: I have noticed that the dust-balls settle down in shady places. Perhaps light is not good for them? So I close the curtains a bit, in order to see whether dust-balls will form in other places, if I let as little draught and light as possible into the room”.
Tristan, one of the boys in the class, has an uncle in Oslo who knows a lot about dust and dust-balls, so Tristan travelled to Oslo to look at dust (which he collected from his grandmother’s house in Oslo) in an electron microscope. The pictures gave him a shock: dust consists of a mixture of hair, dandruff, bits of insects, pollen, sawdust, crystals of ceramic tiles, insect faeces and red blood cells, algae and bacteria. A typical dust sample, says the laboratory.
What we found out!
Of course, the pupils managed to find out all there is to know about dust, and they drew the following conclusions:
Static electricity attracts textile fibres to each other and these “suck up” the dust. There must have been movement in the room for static electricity to occur. This hypothesis is true, but we don’t know how much credit static electricity should be given for the birth of dust-balls. We know that different types of textile fibres can have different electric charges and that this is what attracts them to each other. At the same time, they have to be very close to each other before they will join up.
This hypothesis is almost completely false. Our space research showed that the dust-balls grew even when they lay almost completely at rest. This means that dust and textile fibres are most attracted to the dust-balls, rather than the other way round. We know that they do move now and again, and we cannot reject the possibility that dust “hooks up” to the body of the dust-ball if it moves.
This is the most important reason of all. Draughts are stronger than static electricity forces. Our “space research” showed us where the dust-balls grew in size. All of them ended up in “backwaters” of the room, without any possibility of getting out of them. The feather draught project that we carried out in the classroom showed that it was incredibly difficult to persuade dust-balls to leave such draught-free areas. We really tried! Draughts often pass through the whole room.
Heating cables in the floor may create air-currents that encourage the formation of dust-balls. This is the hypothesis that we have least faith in. Heating cables have no electromagnetic field worth mentioning in comparison with the electromagnetic field from a computer screen.
The pupils thus felt that hypothesis/3G was the most important cause of dust-ball formation. As the Ulsmåg School pupils pointed out “ …draughts often pass through the whole room. Static electricity only works if two objects carrying different electrical charges are brought close together. Static electricity may help in the final stage of accumulation, but by that time the draught has already done the job, perhaps at a distance of several metres…”.
Telling everyone else!
The pupils produced a very readable report and their tireless research and creative problem-solving was celebrated for all of three days, with visits to Tusenfryd Amusement Park, the Research Factory, the Kontiki Museum and the Teknotek science experience centre. Finally, representatives of the 27 pupils who had carried out the project received the ”Nysgjerrigper” prize on national TV.
Their victory meant several TV appearances, (e.g. on the “Newton” popular science programme and news broadcasts), talks given to school heads and teachers in Bergen, etc.
Sist endret: 31.10.2003