There are lots of things that can increase your heart rate, such as drinking caffeinated drinks or alcohol, or even having an heated argument!  The heart should match the beat rate to the demands of your body, so that the right amount of blood gets pumped.  If you pump too little blood your tissues become starved, but if you pump too much you’re wasting energy.  There are some medical conditions that can make the heart pump too fast, but usually they don’t cause the heart to go fast all the time.

It’s hard to say what’s a ‘normal’ heart rate, as diet and level of fitness can really make a big difference.

When the moon is low on the horizon you are looking through more atmosphere, but although this can have the effect of making the moon look orange (because blue light is scattered), and can distort the shape of the moon, this does not make it look bigger.  
Actually, it’s all a matter of perception – you can see other objects near the moon, such as trees or building on the horizon, so your brain interprets the moon as being bigger.  If you were to view the moon through a cardboard tube, and so cut out all the surroundings, you would perceive it as being exactly the same size as it is when you look straight up!

There are two possibilities with this; noises you can hear that come out of nowhere could be tinitus, which is caused when you have damage to your hearing system.  The damage removes the input of certain parts of the hearing spectrum, (you hear across a range of frequencies).  In the same way as some people get “phantom pain” in an amputated limb, the brain ‘invents’ some sound to make up for a lack of input from a part of the hearing system.  Tinitus is normally a high pitched ringing noise, so probably not the cause of a droning sound.

The most likely explanation for a drone is that you have blood vessels in your ears, and these pulsate.  In some situations, such as a very quiet room or when you put your head on a pillow and create a sound chamber in your ear, you can hear the sound of blood rushing through those vessels.

We have had declines up to 90% of some fish, and overfishing seems to be the main culprit.  Whether or not fish stocks can recover is a different matter, we may have altered the marine ecosystem so much that recovery might not be possible.  
You may have heard that there’s not much cod left in the sea, especially around Canada.  A crash in cod numbers shut down many canadian fisheries in the 1980s, but the numbers of cod have not recovered despite much lower fishing.

A caller also pointed out that although trawlermen must throw back any juvinile fish, those below a certain size, often the nets damage or kill the small fish anyway, and so the damage is already done.  A better way would be to establish protected areas, but they may be prone to poaching.  We currently only have about 1% of the Earth’s ocean protected.

This only works on old fashioned tv screens or computer monitors, so to understand why this happens we need to know how they work.  Inside a television there is a big glass chamber which has had all the air sucked out to make a vacuum.  At the back of this chamber is an electrical gun which fires electrons towards the back of the screen.  The screen is covered with tiny lumps of phosphor, which glows when an electron hits it.  If you cover the whole screen with one colour of phosphor, you get a black and white tv.

To make a colour tv screen, they put tiny spots of three different colours of phosphor on the screen in groups.  Each group contains a spot of red, a spot of green and one of blue.  Lighting these up in different combinations can make all the colours you see on your tv.  

As electrons fly towards the screen, they can be moved using a magnetic field – this lets you aim the electrons at the right spot of phosphor and get the right colours in the right place.
When you put a magnet near the tv, it diverts the electrons away from where they should go, and so the wrong phosphor spots light up and you don’t get the right colours.

Sometimes, if you put a magnet near a tv for too long, you can make bits of it magnetic and so it will always distort the colours, thish is how the colours stay there.

Some tv’s have a degaussing coil inside them that re-sets the magnetism when you switch them on, so the colours go back to being correct.

Even the Earth’s magnetic field is enough to distort the colours, so if you turn a tv upside down when it’s switched on, this can also make the colours go wrong.

The light must be reflecting of something, and on a very dry night this could be dust.  However in the UK the most likely candidate is water vapour – not dense enough see normally, more like a very light mist.  This mist can form when moist air cools, and water condenses into a vapour, and is very likely the reason why you can see the town’s lights on a clear night.

Self-raising flour contains baking powder, which is usually a mixture of bicarbonate of soda, crème of tartar and something called calcium aluminium phosphate.  Bicarbonate of soda has lots of carbon dioxide locked up in it, which is let out by reacting with an acid.  Crème of tartar becomes tartaric acid when it gets wet, so these then react together and produce bubbles of carbon dioxide in the cake, making the cake rise.  Calcium aluminium phosphate only becomes acidic when it gets to a certain temperature, giving extra bubbles, and so extra rising, while the cake bakes.

CT, or Computerised Tomography scanning  technology was a massive breakthrough in medicine.  It gave us the first £D views of the inside of the body without having to open people up.  CT scans rely on x-rays, which pass through the body and different tissues absorb different amounts.  Instead of shooting one x-ray straight through you, which gives a kind of x-ray shadow on a photographic plate, CT scanning shines lots of x-rays through the body at lots of different angles.  By taking a picture from every one of these angles a computer can then work out how much of the x-rays were soaked up by each tissue they went through, from each angle.  The computer can the use this information to build up a picture of what you look like inside in 3 dimensions.

CT scans can be made even more sensitive by adding contrast – heavy atoms of things like iodine or barium that soak up lots of x-rays.  This can help show up things like blood vessels compared to other tissue.

CT is very useful for looking at things like stroke, where you can look in the brain and see if there’s a blood clot or bleed – as blood contains a lot of iron is shows up quite well.

When you’ve got a blocked coronary artery for example in the heart, what people used to do was to stick a line in through the top of the leg, into the artery, thread it back to where the heart is, go into the blood vessels supplying the heart and then you inflate a tiny balloon inside the artery.  This opened up the artery by squashing the blockage which was making the artery narrow.

When they did that to start with, what would happen is, very quickly the artery would block up or fur up again. So then doctors discovered that the best approach is you if you deploy what’s called a stent, which is like a metal scaffold.  Now it’s very very tiny when you first put it in and it’s threaded over the end of the balloon and when it gets to the right point in the artery where you want to deploy it, you inflate the balloon which stretches the scaffold.  It’s almost like it ratchets out and locks in position.  It props open the wall of the artery, stopping it constricting again and this should hold the problem area open and make sure it doesn’t block again.

Soap is a very good way of cleaning your hands because its got oily molecules in it that will break down the membranes of microorganisms.  All microorganisms are surrounded by an oily bag which separates the good things inside a cell from the environment outside.  And because it’s oily, if you’ve got some detergent or soap it can stick its wiggly chain into that oily bag, break it open and then bust open the bug.  This is why soap actually works and detergents work. Physically rubbing your hands together also helps, as it detaches microorganisms when under a stream of water.