There’s nothing worse than hearing a recording of your voice for the first time!  The reason is that how we think we sound isn’t really how we sound.

Inside your ears there is an organ called a cochlea, a special neurological structure that converts the vibrations of sounds in the air into electrical signals that the brain can understand.  It gets stimulated by the pressure waves caused by sounds in the air, but at the same time can pick up the vibration of the bones in your skull.  When you are listening to sounds in the environment, the chief source of those sounds is coming through the air, very little comes through the bone.  When you’re speaking, however, your whole head resonates; it vibrates.  This means that your cochlea gets stimulated by your skull vibrating, as well as the sound coming out of your mouth and going through the air to your ears.

The body does two things; it gets a different version of those vibrations (through the bone and the ear), but it also has a protective mechanism to cut down the amount of sound which is going into the cochlea.  It reduces sensitivity of your ear a little when you’re speaking, so you get a slightly different rendition of what your voice sounds like.

That’s why, when you hear yourself recorded and played back, you sound totally different, because all you hear back from the tape recorder is sound coming through the air, minus the skull vibration and bone conduction.

There’s no special technology involved, it’s basically the same as when you launch a rocket off the surface of the Earth; you have to go fast enough to escape the Earth’s gravity.  If you were standing on the surface of the sun (and could cope with the 5000 degree temperature) and launched a rocket, you would have to get it up to 617.5 kilometres per second (km/s) to get it to escape the gravitational attraction of the sun and out of the solar system.

As the Earth is already travelling at 30 km/s you don’t need to get it quite as fast, but you couldn’t possibly launch something at those sorts of speeds.  To get out to the far reaches of the solar system, and beyond, you need to get a boost by whizzing past another planet.  This is called ‘gravity assisted’ because you use the gravity of a planet to sling shot you further out into the solar system.

Well, actually yes.  Stars are at relatively low density in a galaxy, and so if two galaxies collide, the probability is that actually not one single star would collide in the process.

There is, however, a lot of gas between the stars in a galaxy, and this gas would collide and be compressed, and that would, in itself, form a whole new generation of stars.  The gravity from these stars would affect everything around them, and you would end up with a great big mess.  Here on Earth, in the outer spiral arm of the Milky Way, we would probably survive.

David Block, of the University of the Witwatersrand, South Africa, observed the Andromeda galaxy and a nearby dwarf galaxy and noticed a ripple effect in Andromeda.  He worked out that if you wind back the clock on these ripples, it puts the origin at about 200 million years ago.  The ripples are thought to be the result of Andromeda having previously collided with one of it’s companion galaxies, so galaxies can definitely survive such a collision, but it’s anybody’s guess what the results of this ripple effect would be.

Galaxies are not necessarily all moving in the same direction, some, found in clusters of galaxies, orbit each other.  In all, it’s a bit of a mess!  This means that galaxy collisions do happen.

We do know that the Andromeda galaxy is going to collide with our own.  In about 3 billion years, even before our sun has died, Andromeda will collide with the Milky Way.  Maybe future generations of humans, or whatever is living on Earth in 3 billion years, will be able to observe what does happen when two galaxies collide!

It’s actually neither.  A rainbow is caused by sunlight hitting clouds or rain, and can usually only be seen if there is a background of dark clouds.

Sunbeams go into a raindrop, reflect off the back inside surface of the raindrop and come back out of the front.  When they come back out, the raindrop behaves like a prism, and splits the light into all the different wavelengths that make up white light.  White light, such as light from the Sun, consists of lots of different colours of light added together, so when they are all together it looks white, but if you split them up you can see the colours.

A double rainbow occurs when the light does a double journey; it reflects off the back of the raindrop, then bounces off the front inside surface, back to the back surface and then out.  This causes a second rainbow outside the first one, but with the colours the other way around.

The curvature of a rainbow different.  If you could look at a rainbow from far enough away, you would see a complete circle.  This is caused by the angle at which light exits a (roughly spherical) raindrop.  We can’t see the entire circle because the Earth gets in the way.

You do get some similar effects from the moon.  When you get very high altitude clouds consisting of many ice particles, you can often get a similar effect to a rainbow.  It’s less common and less bright than a rainbow though.

The reason a rainbow effect is created on oil is because of interference.  Oil on a puddle will tend to create a thin film, which can be anything from 10 to 100 molecules thick, so it’s very thin.  Each of them can act like a tiny mirror, so when light hits the surface of an oily puddle, some will reflect off the water under the oil, and some will reflect off the oil layers.

As light is a wave, if you cause the waves to stop lining up with each other, you can get the ‘up’ part of one wave aligning with the ‘down’ part of another wave, and these can cancel out.  This is called interference, and it causes a pattern of colours according to how much interference is occurring.  Oil films of different thicknesses cause different amounts of interference, so you get a rainbow effect.

The same effect is seen on the surface of a bubble, which is also a thin oily film with varying thicknesses.

This is likely to be caused by water condensing out of the atmosphere onto a point.  Once there is a nucleation centre, such as an ice crystal in the mud on which more ice can form.  This small crystal of ice would not only offer a nucleation point, but would also separate the condensed water vapour from the relatively warm Earth, encouraging freezing on this, slightly higher, point.  This would lead to a ‘stalagmite‘ of ice forming from atmospheric water vapour.

Actually, the temperature is colder in space than on Earth, as we have an atmosphere which keeps us warm.  So at the same distance as the Earth from the Sun it’s about –50 degrees in space.  On Earth, we lose heat through radiation, evaporation of sweat and by conduction of heat to the air.  It is harder to lose heat in space as you can only lose heat through radiation.  Electrons in the molecules in our body go from a high energy state to a low energy state, and so lose energy by radiating infra-red radiation.  

When you face the sun, you will absorb the Sun’s radiation and be warm, but at the same time, your back will be in shade and will lose heat rapidly as there’s no atmosphere to conduct the heat around you.  Large temperature gradients are found in space; things get very hot when they are in the Sun’s rays, but very cold when they are in shade.

Black holes are a lot smaller than the milky way, which actually has what’s called a Supermassive black hole in it’s centre.  Each galaxy seems to have a black hole in the middle of it, around which the stars in the galaxy orbit.  As far as we know, there is no ‘other side’ to a black hole, and if we were to go into one, we would undergo a process known as spaghettification, where the gravity of the black hole pulls matter into long thin shapes, rather like spaghetti.

[We put this question to Jonathan Shanklin, who discovered the hole in the ozone layer and was our guest on the Atmospheric Analysis show]

The Earth does go through regular cycles of warm and cold, and we are currently in one of the warm periods.  The cycles are clearly shown in Antarctic ice cores, which show several cycles over the last 750,000 years, each one lasting around 120,000 years.  Carbon dioxide levels and methane levels are high during the warm periods and low during the cold periods.  The main driver behind these changes are variations in the Earth's orbit, and these would suggest that we should now be heading towards a very slow cooling.
We have however changed our atmosphere so fundamentally that carbon dioxide levels are much higher than at any time in the last 750,000 years.  This much higher level of carbon dioxide (30%) is what is giving rise to the anthropogenic global warming.  We are probably committed to at least a 5 degree rise in average global temperature.  This will have dramatic effects on ice cover and sea level.  The need to cut carbon dioxide levels so urgently is to prevent things getting even worse.  The problem is actually even greater than this, as in the developed world we are consumming the resources of over three planets.  This is not sustainable as we only have one planet!