Mar 28, 2010
Materials, water, and light
Some scientific links from this week, including my Materials Today news round up.
- Periodic Table of Parodies – Yet more periodic table fun and games
- Similar websites to Sciencebase – This neat little tool automagically works out your site's keywords and searches for other sites with the same keywords
- The long and winding road to synthetic silk – Unravelling the secret of silk's incredible strength could allow materials scientists to develop a synthetic version for a wide range of applications in engineering, aeronautics, and even clothing.sc
- Bubbling up water repellence – Nanoscopic air bubbles prevent water from wetting a nanopatterned superhydrophobic surface
- Magnetic solder for 3D microelectronics – A low-melting and magnetically-responsive alloy could be the key to soldering the components of three-dimensional microelectronics
- Water vapor and global warming – Climate change denialists often cite water vapour as the main greenhouse gas, supposedly accounting for almost 100% of the greenhouse effect, but this is wrong. Water vapour and clouds account for only 65-85% of the greenhouse effect.
- Light controls matter, matter controls X-Rays – Light has an upper speed limit, but not a lower one, in some materials it is possible to slow light to almost a standstill
"Deceived Wisdom: Why What You Thought Was Right Is Wrong" from David Bradley. Available now on 
That’s one way of looking at it. Of course when light particles, photons interact with matter they are “dragged around hither and thither” like you say, but it isn’t the same photons that emerge from the other. A photon is absorbed, which excites electrons in an atom, when the electrons drop back down to their lower enery, they emit a photon. Given that there are vast numbers of atoms and so vast numbers of such interactions each of which would introduce a delay between absorption and emission, then it’s no surprise that in some materials light “travels” more slowly through it. Of course, for an opaque object the delays are so great that the minute losses of energy with each absorption emission add up so that the light never emerges from the other side.
I’m sure an optics expert will contradict me if that isn’t what’s happening, but light does not simply “pass through” a transparent object. And, I haven’t even thought about the quantum mechanics…
“Light controls matter, matter controls X-Rays – Light has an upper speed limit, but not a lower one, in some materials it is possible to slow light to almost a standstill”
I had always assumed that the speed of light in more obdurate materials was not slower, but simply that its route was more complicated, being dragged around hither and thither as it made its way through the material. Is this wrong?