First assume that the cereal is made up completely of carbon. 12 grams of carbon contains approximately 6.023 x 10²³ atoms of carbon (The Avogadro Number from earlier on).  So 200 grams of carbon contains (200/12) ~ 17 x 6.023 x 10²³ atoms. Each atom of carbon contains 6 electrons. So the final total is 6 x 17 x 6.023 x 10²³ which comes to 6.14 x 10²⁵ atoms.

Next assume that the milk is made up completely of water. 18 grams of water contains approximately 6.023 x 10²³ molecules of water (The Avogadro Number again). So 200 grams of water contains (200/18) ~ 11 x 6.023 x 10²³ atoms. Each molecule of water contains 2 atoms of hydrogen each with 1 electron and 1 atom of oxygen each with 8 electrons which makes 10 electrons per molecule. . So the final total is 10 x 11 x 6.023 x 10²³ which comes to 6.63 x 10²⁵

These two numbers are so similar that it barely makes any difference what we assume – so 400 g of cereal – made up of any mix of milk/cereal contains roughly 6.14 x 10²⁵ + 6.63 x 10²⁵ ~ 1.27 x 10²⁶ electrons.

And pretty much exactly the same number of protons.

We use the word in two quite distinct ways. We use the word to describe the both the body of scientific knowledge – which is now vast – and the process by which ‘knowledge’ is added to the body. Both aspects have their roots in prehistory – but both were profoundly affected by the introduction of mass produced printed books.

Some important elements in the scientific process are that

• - Nothing is sacred – any idea or results can be found to be incorrect no matter whose idea it was.
• - Ideas need to be tested experimentally.
• - Experiments need to be reproducible by more than one group

Let’s look at the power 20 squad members in a Rugby team training together might produce.

• Rowing Machines: If I try hard I can generate 150 W of power on a rowing machine for around 10 minutes. Let’s assume rugby players can generate for 250 W for 15 minutes. If we had 5 machines then we could rotate banks of 5 players through these machines to generate a continuous 5 x 250 = 1250 W – that’s impressive .
• Treadmills: A treadmill actually consumes energy, and a typical device might have a 2 horse power (1500 W) motor. So either we could have 6 rowing machines powering one treadmill, or more sensibly, we could just abandon treadmills and get the team to run around a Rugby pitch.
• Exercise bikes: I don’t have a figure for bikes, but in my experience they are less knackering than rowing so I would guess they can generate less energy. Let’s guess we have 5 exercise bikes and each one can generate 150 W then we could rotate banks of 5 players through these machines to generate a continuous 5 x 150 = 750 W.
• Cross Trainers: I don’t have a figure for cross-trainers (sometimes called elliptical trainers),  but in my experience they are less knackering than rowing but more knackering than exercise bikes, so I would guess they can generate power somewhere in between the previous two. Let’s guess we have 5 cross-trainers and each one can generate 200 W then we could rotate banks of 5 players through these machines to generate a continuous 5 x 200 = 1000 W.

So with 5 of each type of cardio machine and no treadmills, 15 rugby players could generate 1250 W + 750 W + 1000 W = 3000W – a useful amount of power. Each person would be working at a rate which would burn roughly 1000 kCal/hour which is pretty intense exercise, so let’s guess that they could do this for one hour.

• Muscle Machines: In these machines pulleys translate the physical motion into a lift of some weights, typically by about half a metre. Let’s assume that each lift is of 40 kg, then each lift requires (m x g x h) (40 x 10 x 0.5) 200 Joules of energy. If we could capture this in a way that generated electricity, and  a lift was performed on average every second (assuming several people are exercising simultaneously) then that could generate 200 W of power.

Is it feasible?

Given these simple calculations the answer has to be – ‘Yes’. But there are caveats

• In general one can’t capture all the energy people dissipate in these machines. Dynamos are not ideally efficient and the muscle machines would not couple easily to dynamos; some players may not be ideally fit; and we have assumed 100% occupancy of the equipment. So in practice our 3000 W of power would be substantially reduced, but 1000 W would be a fair estimate.
• Human’s generate heat when they exert themselves – about 10 times more than work they produce. So if 3000 W of work is being produced there would be an astonishing 30 kW of heat produced – so some kind of cooling or ventilation would be required – which would take energy. Let’s assume this is negligible and that we cool using a chimney effect.
• The gym would need to have a relatively large floor area which would probably require lighting – which would probably require several hundred watts  - but let’s ignore this and assume the training is in daylight.
• Over one hour, the team would have plausibly generated 1 kWh of useful electrical energy, which would have cost at most £0.25.
• Over one day (12 hours) assuming the equipment was highly utilised, this might amount to 12 kWh of energy, which would have cost at most £3.00.
• Over a week (5 days) this might amount to 60 kWh of energy, which would have cost at most £15.
• Over a year this might amount to 3120 kWh of energy, which would have cost at most £780.

So all in all: this 2.6% per annum return on investment might well make sense in the context of the £30,000 or so which such a gym might cost.

But would that be carbon neutral?

Well No.

Such a gym would not recoup the carbon released during in the manufacture of the equipment for many decades – probably beyond the lifetime of the equipment. But people might well prefer a gym where they feel their efforts aren’t being wasted. However, what would be the worst possible outcome would be that additional generating equipment was incorporated into gym equipment to make people feel better, and that the carbon cost of the additional equipment was not recouped either!

As many people have found micro-generation of electricity can make sense in certain contexts. For instance if the gym  was in an isolated location which could not connect to the electricity grid. But nothing can approach the low cost of central generation of electricity using cheap carbon-emitting fuel. If electricity from the grid was all  renewably generated lots of schemes such as this one would make economic sense. However electricity might then cost perhaps £1.00/kWh and we would all take much more care not waste a joule. Anyone in favour of massively increasing electricity prices?

This question was originally posted on Michael’s blog

Yawning is an involuntary respiratory reflex, which regulates the carbon dioxide and oxygen levels in the blood.

A yawn is commonly triggered either by fatigue or boredom and when a person is tired or bored the breathing is not regulated and it is shallow, and little oxygen is carried to the lungs by the oxygen-toting cardiovascular system.

Yawning elevates ones alertness, as the sudden intake of oxygen increases the heart rate, rids the lungs and the bloodstream of the carbon dioxide buildup, and forces oxygen through blood vessels in the brain, while restoring normal breathing and ventilating the lungs.

Yawning is a kind of physiological mechanism that is designed to maintain attention and regulate our breathing.

• Fukushima is a triumph for nuke power: Build more reactors now!

to the mundanely exagerated

• Japan nuclear crisis ‘over in nine months’

However, I have yet to read a clear web account of what has actually happened! The Wikipedia timeline somehow confuses rather than elucidates. A couple of weeks back I was lucky enough to receive a PowerPoint presentation by Mattias Braun from Areva. Using this and other sources I have attempted to summarise what actually happened.

The Fukushima Daiichi Site #1 consisted of 4 boiling water reactors:

• Unit 1 – GE Mark I BWR (439 MW), Operating since 1971
• Units 2-4 – GE Mark I BWR (760 MW), Operating since 1974

The structure of each reactor was similar

The structure of each reactor

11th March 2011: 14:46 The Earthquake struck causing an immediate ‘scram’ and all three operating reactors shut down safely. As I have described previously, this reduced the heat generated in the core from a breathtaking 1500 MW to something close to 100 MW – still a great deal of heat. Diesel generators started to provide power to circulate water to keep the cores cool. At this point the plant was stable and the operators were perhaps feeling relieved that things had gone at least roughly according to plan.

11th March 2011: 15:41 Now the tsunami arrives. With a height of 14 metres, it overtopped the defences designed for a 7 metre tsunami. The entire plant was disconnected from mains electricity, and the diesel generators and their fuel supplies were destroyed. The cooling system continued to cool the core powered by batteries and the operators began to cope with what had happened.

Reactor#1 At 16:36 – barely two hours after shutdown – the batteries failed. The  operators now had only one core-cooling option. This was to relieve the excess pressure in the reactor vessel by discharging steam into the ‘wet well’ where it can condense as long as the temperature is below 100 °C. This reduces the temperature and pressure in the  reactor vessel and provides some cooling, but inevitably lowers the level of water in the reactor vessel, eventually exposing the core material.

Read more on Michael’s blog >>>

Then the second part: can this link be an explanation for mimicry eg. Mantis orchid? This is almost surely not the case. To find out why, we need to have a look at the relations between all living things according to the theory of evolution.

Life is believed to have started as single cells, probably not very different from some of the more primitive bacteria that are still around today. There is lots of debate about how this exactly came to pass, and some scientist called ‘synthetic biologists’ are trying to re-create living, replicating cells from simple chemical building blocks.

These single cells are the root of the ‘tree of life’ (image http://www.flickr.com/photos/stephenjjohnson/3568141985/in/pool-316313@N20) which shows how life has evolved over millions of years, from this starting point into all the living things around us today. The branching point between animals and plants happened a long time ago, so the mantis and the orchid are on branches that are very far apart.

This means that although they are related, they are very distant relatives, i.e. they will not share that many genes which could explain the similarity in appearance, as in the case of humans and chimpanzees, where approximately 95% of the genes are similar.

Question asked by Iain, London

Normally the nucleus of atoms is ‘protected’ deep within the atom. But it is possible to split the nucleus by hitting it with (for example): a neutron; a very fast moving proton ; or a collection of two protons and two neutrons which is known as an ‘alpha particle’. When the nucleus is split, two new nuclei of two different atoms are formed.

There are a number of funny technological and scientific reasons for doing this, but the most important one by far is the extraction of energy. When we ‘burn’ wood we cause the carbon atoms to stick to oxygen atoms – and the resulting molecules move faster than the original molecules – i.e. they get hot. Similarly, splitting a nucleus of uranium causes the fragments to move very fast. But the amount of energy available is stupendous.

Burning one kilogram of wood might heat your house for an hour. If we could safely extract the energy from one kilogram of uranium (which would fit in a cube 4 cm x 4 cm x 4 cm ) there would be one million times as much energy – enough to heat a house for around 100 years! The stupendous energy density of nuclear fuel is the basic motivation for nuclear power.

Asked by Charlie from Guildford. Photo by Darren Hester.

It needs water because its body (like any animal) is to a great extent made up of water. But there is a continuous loss of water through sweating and the production of urine. Sweating contributes to cooling of the body, and urine will excrete some of the waste that is produced when the animal extracts energy from its food.

We could liken hibernation to turning down the thermostate in your house. A lower setting means that your energy bill will be less, and so it is for the animal too. What the hibernating animal does is literally turning down its body thermostate, so it uses a lot less energy in keeping its body warm. Added to this, it will retreat into a safe corner and stay there, motionless. This means no energy needs to be used for muscle movement.

When less energy is used, less has to be produced. As a result, there will be less waste that needs to be excreted, so less water will be needed for this. With a lower body temperature, sweating will also be reduced. Taken together, the animal can use its body reserves of water and fuel (fat) to survive for a long time while it is in this “energy saving mode”. Long enough to survive the period of hibernation without dying of starvation and thirst.

Question asked by Rich from Wimbledon

Visible light from the sun is made up of components of different wavelength (the electromagnetic spectrum as in a rainbow; red, orange, yellow, green, blue, indigo, violet). When the light hits a single ice crystal, some of it is absorbed and some reflected back; on passing through the crystal the light changes direction due to a process called refraction, as in a prism, and can be internally reflected within the crystal.

With vast numbers of individual crystals of different form in snow, and the differing wavelengths of the components of white light, the overall effect is very complex. The resulting appearance,  including reflection of much of the incident white light, is white.

Asked by Shelley, Hounslow

3 D glasses typically have the left-hand optic covered in red and the right hand-optic covered in blue. The 3-D material – a picture or a single frame of a film – has two images printed, one in red and one in blue. When we view this image through the glasses our left eye mainly sees the image printed in red and our right eye mainly sees the image printed in blue. Our brain interprets the differences between the  different images as being due to differences n perspective and reconstructs a 3-D view of the scene.

Asked by Tim, South London

*Photo credit