How do antidepressants work ? Daniel

Depression seems to result from low levels of certain 'feel-good' chemicals in the brain. There are about billion nerve cells in the brain, which talk to each other using electrical signals. When these signals get to the end of one nerve cell they jump to the next at a site called a synapse, using a chemical messenger known as a neurotransmitter. One of the most important of these is a substance called serotonin, and people with depression tend to have low levels of this and similar chemicals. Antidepressants help to push up the levels of of these chemicals, helping to improve mood. St John's Wort is an example of a natural remedy that some people use, which is said to have a positive effect. Of course some people don't suffer from depression, but seasonal affective disorder (SAD), which can be worse at this time of year.

October 2004

How long will it be before our current Big Bang theory is out of date? David

One thing in science is that you can go out and do an experiment about peoples' claims. If the facts don't fit the theory, then the theory goes straight out the window. Huxley once said that there's nothing more tragic in science than the slaying of a beautiful hypothesis by an ugly fact. That's how science works. Scientists are not so arrogant as to say they know everything, but there are things in cosmology that are absolutely certain, for instance the influence of radiation. There are other things that we don't know much about, however, for instance dark matter, and cosmologists are happy to admit this. At the moment it's impossible to say.

October 2004

why don't woodpeckers get brain damage when they hammer into a tree? Neil

In the late 1970s scientists tackled this by using a very fast camera capable of taking 2000 pictures every second. Analysis of these images showed that a woodpecker's head tolerates a force of about 12 thousand times the force of gravity whenever it hits something, which is a considerable force going through its head, so why shouldn't it get brain damage? Well there are various woodpecker adaptations which means they are able to cope with this trauma, and one of them is that their skull bones are quite spongy which mean they can absorb shocks very well. Another adaptation is that a woodpecker's brain is small and so has a very big surface area to weight ratio, and so the force is spread over a large area. The photography also revealed that woodpeckers line their heads up very straight with whatever they tap into, so there's no rotational injury which, at least in people involved in car accidents, is a major cause of brain injury as delicate nerve fibres are torn by the brain trying to twist on itself.

October 2004

In Mill Road in Cambridge last Halloween I was out trick or treating with my daughter. We arrived at a door and mother and daughter came to the door, with another little girl who didn't speak at all, and was dressed in a Victorian dress which is what I thought was her costume. A few days later I asked the mother who this little girl was, she said no one else had been there - but myself and my daughter had clearly seen her. Corinne

This is interesting because most sightings of ghosts last between 5 and 30 seconds. But this this lasted longer if you saw her the entire time you had a conversation. You couldn't see her feet, which is also a give-away because ghosts don't usually respect floors ! If it is real it sounds like this was someone who probably lived in this house previously. If I were you I would find out a bit more about who lived there and see if it ties up, but a sighting of this duration would certainly raise eyebrows !

October 2004

Whilst visiting a friend an electric toy belonging to her children suddenly switched on, doors opened and things moved around in the room ! What was this ? Debra

There doesn't seem to be enough in this one, I'm afraid. These are things that can't be explained but it needs more for me to say yes or no whether this was a ghost. It needs more examination in more detail such as whether anyone has reported anything like this before.

October 2004

As a young child I woke up in the middle of night and found a man in red and white pyjamas standing at the end of my bed. He wasn't anyone I knew, I shouted out loud and he started crying and then disappeared. Clare

This is a well known, and there a lot of cases like this where people wake up and see an old woman or old man at the end of the bed. It has been put down to something psychological, almost like a waking dream. It is the kind of thing that we would like to get photos of, because then we would be more likely to believe it, although ghosts are very difficult to photograph.

October 2004

Why can't we photograph ghosts if you can see them? Chris

This is a good point, we don't know why they can't be photographed. We don't know what ghosts are - whether they are something that has come back from the dead, or something else entirely. It would be brilliant if we could get photos, or even better would be a video. Stories of people saying they've got names from ghosts are probably not true.

October 2004

I grew up in an incredibly old house. Our dog was the most placid animal, and yet it would run at the fastest pace possible up the stairs from the ground floor, to the third floor and visibly shake. Also at other times I felt like I was being kicked in the back although there was no-one in the room. I also see a 'glow' in my present house. Sally

Animals do react to things that we are unaware of, and are very sensitive to paranormal activity. Regarding the glow, try and get a photograph of it, and we can analyse it.

October 2004

I lived in a house where the dining room which was always colder than all the other rooms, and both my wife and I could see something in our peripheral vision. Then one evening I was sitting in this room, and our cat jumped up looked spooked and I suddenly felt cold, and a presence. Alan

It could have been something, but lots of people feel presences in houses. I would need to see a lot more to be convinced.

October 2004

I lived in a large house in Norfolk on a farm and one night I heard a coach and horses come up the drive, yet we didn't see anything. Angie

That's a common thing, but an interesting one. Sounds of ghosts also evade recording, which is what would be needed here, but I think this is probably a likely paranormal occurence.

October 2004

what is absolute zero? Bob

The temperature of an object is a measure of how much energy it has, and when something has energy the atoms in that object vibrate. The hotter it is the more they vibrate, the colder it is the less they vibrate. As you lower the temperature those vibrations reduce. As you get towards what we call absolute zero, that's when the vibration has almost completely stopped, so you can't get lower than -273 degrees, that's zero degrees Kelvin, matter has not energy or motion at this temperature, hence it's absolute zero.

October 2004