It is the nature of science to ask questions and science year should encourage pupils to ask more of them. No teacher can know everything about science, or you may want pupils to try to find out for themselves, so here are some “ask the experts” websites to check out.

Sciencenet at www.sciencenet.org.uk is the web based version of the “Ask a Scientist” telephone service run by Science Line. You can search to see if a similar question has been asked already, or fill in a form and they will e-mail an answer to you within a couple of weeks. They will not do pupil’s science homework, but among a sizeable database of previously answered questions there are plenty of homework questions that were obviously accepted once upon a time and are well worth pupils trawling through.

The counterintuitive nature of much science is responsible for many of the questions being asked at New Scientist’s Last Word site at www.newscientist.comlastword The answers are provided by the New Scientist readership and there could be several answers to one question, reminding us that our understanding of scientific concepts can be arrived in a variety of ways.

The BBC’s online education empire building continues. For a few years now secondary school pupils have been able to Ask a Teacher at www.bbc.co.ukeducationgcsebitesizeask or www.bbc.co.ukeducationks3bitesizeask for help preparing for SATs and GCSEs. SOS Teacher expands the service beyond the few months leading up to exams. Most services will not help you with their homework - these will. Launch is imminent and they are aiming at a turn-around time of just four hours.

Pupils are also welcome to ask science homework questions at Homework High at www.4learning.co.ukappshomeworkscienceindex.jsp The hours of business are fairly limited, but if a question is accepted the response is speedy - unlike the couple of weeks’ wait from most of the competition. I got a swift response to my question, although unfortunately not an answer, so I am none the wiser about why the letter I represents current in the Ohms Law equation V=IR.

The Madsci Network at www.madsci.org panders unashamedly to the stereotype of the nutty scientist but has a massive database of previously answered questions. The in-your-face style will appeal to children, but adults are welcome to ask away, too.

All Experts at www.allexperts.com are the big guys of the ask an expert field with science just a tiny sliver of their act. Depressingly, the category of science includes subjects with dubious scientific credentials. I put this to expert astrologer Zane Stein, and got a thoughtful and reasoned response. You get a brief biography of the person who will answer your question, so you can steer clear of civil engineers if your question concerns general relativity.

Ask Dr Universe is the alter ego of a female cat based in Washington Sate University at www.wsu.edudruniverse The site is very child friendly and appears to have been swamped with questions as a result, so it may take a while to get a response. However, the site is well worth visiting for younger pupils, even if they do not want to send in a question.

Scientific American at www.sciam.comaskexpert allows you to browse nine categories of previously answered questions. If a question similar to yours has not been previously tackled, you could try asking away, but it is chancy. This is the least personal service, with only the most interesting questions being accepted and answers posted on the site, so do not bother asking them why the sky is blue.

Ian Francis is a science writer and teaches in Hertfordshire