Archive of posts by Michael de Podesta
How many electrons are there in the average bowl of cereal?
Wednesday, November 9th, 2011
Well typically breakfast consists of around 200 grams of cereal and roughly 200 millilitres of milk. For these purposes I will make some assumptions:
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.
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What is science?
Saturday, October 29th, 2011
The word Science is derived from the Latin word Scire – ‘to know’. It is probably related to the word ‘scindere’ (from which I think we get ‘scissors’) which means to split or separate – i.e. it means to sort things out.
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A carbon neutral gym?
Monday, September 5th, 2011
While sweating and struggling in a gym, you may have wondered if all the energy you’re putting into your workout could be put to some use. How about, using that energy to help power the lights, or the actual treadmill you’re running on, rather than it all being wasted. What’s more, could all this energy being produced actually offset all of the gym’s power needs and create an entirely carbon neutral gym?
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.
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Fukushima: What happened?
Tuesday, April 19th, 2011
It’s been 6 weeks since the Fukushima nuclear accident, and news reports of the incident vary from the facile
to the mundanely exagerated
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
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Why split the atom?
Monday, November 15th, 2010
First of all the phrase ‘splitting the atom’ is a misnomer – atoms are ‘split’ all the time as they lose electrons in chemical reactions. The phrase really refers to ‘splitting the nucleus of an atom’. You can read more about this on my answer to the question What does “splitting the atom” mean?
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.
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How do 3D glasses work?
Thursday, August 12th, 2010
Normal 3 D vision works because our left eye has a slightly different view of the world from our right eye.
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. (more…)
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What is beyond the edge of the universe?
Tuesday, June 15th, 2010
Firstly – and obviously – nobody knows. But you have actually asked two questions.
Firstly there is the observable universe, and then there is the Universe, and then there is your question. As we understand it at the moment, the story goes like this:
Initially the universe was filled with ‘primordial substance’ (protons, neutrons, and electrons mainly but not assembled into atoms) and was opaque to light and radio waves. About 300,000 years after the big bang, the universe condensed from separate protons and neutrons and electrons into atoms and at this point the universe became transparent.
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What does “splitting the atom” mean?
Monday, June 14th, 2010
It is a very confusing term. In a sense every chemical reaction ‘splits’ atoms because it takes or adds electrons away from atoms. However the phrase would be more correct if we spoke of splitting the nucleus of an atom.
This can be done in a number of ways, but typically, it involves bombarding a substance with protons or neutrons or even entire nuclei of other atoms. Most of the particles don’t hit nuclei in the target but some do, and by interact electrically and through the strong force they can break up a nucleus.
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