Last post of 2023. If you look at a river, you will quickly realise that the water flows at different speeds depending on where you’re looking. Near the river banks it usually flows quite slowly, whereas it will typically flow much faster near the centre, if unimpeded. A closer inspection reveals that the currents in… Continue reading Time is not constant – not in our universe

The great physicist, Richard Feynman, once said that if you claim to understand quantum physics, then you don’t understand quantum physics. Anyone who has studied it will tell you that it is bizarre, unfathomable and completely counter-intuitive. One of the strange issues is the wave-particle duality of fundamental ‘particles’ such as electrons and photons. When… Continue reading Waves or particles – the conundrum in Quantum Physics

When light enters the skin the photons immediately encounter atoms and molecules. With each encounter there is a probability that each photon will be either absorbed or scattered. The skin is a highly scattering medium, so the probabilities of scattering are usually much greater than the probability of being absorbed (in most events). Some of… Continue reading How does fluence vary with depth in the skin?