eli5 how does water stop radiation and not everything else outright, and how can radiation do damage to us if we are mostly made of water?
In: 0
So there are different types of radiation to begin with, the major groups would be neutron radiation, beta radiation (a free electron flying around), gamma radiation (also known as a photon or packet of pure energy, common example is sunlight), or alpha radiation (an alpha is a helium nucleus that is ejected with no electrons, so not an atom, just 2 neutrons and 2 protons stuck together flying around)
Two common ideals when discussing shielding are 1: what is the likelihood that radiation will interact with it and 2: if it does interact, how much energy is lost, and/or velocity change
To adress the first point density of the medium plays a big role, water is more dense than air, at a molecular level there is more “stuff” packed together for these particals to hit. However, the radiation varies too, the largest radiation particle is the alpha, this is the big rig truck of the radiation, it isn’t fitting through much, so typically a single sheet or paper or your dead skin layer is enough to stop this radiation, neutrons are smaller, so can travel farther through a medium without potentially interacting, down to betas and gammas, extremely small, will travel far through most things
For the second point, the similarities in mass come into play, consider you are at a bar playing pool, and you hit the cue ball directly into the 8 ball, the cue ball stops dead in its tracks, and the 8 ball is accelerated at the same speed away as the cue ball was traveling, this is maximum energy transfer. In a molecular world of a cue ball flying through 10 billion 8 balls packed closely together, its energy will be diminished and lost throughout quickly. This is the case for water and neutrons, water contains a ton of hydrogen, which at its base is a single proton, which has basically the same mass as a single neutron. Now imagine you went outside the bar and threw the cue ball at the brick wall of the bar, it would bounce off and basically retain all energy, this is the case for shielding like lead, very very heavy and large atom, but very dense, so instead of removing energy from radiation, it just directs it back. In general though, water has the right mass, and right density to be a good shield.
Yes you are made of water, but you are not made of tens of feet of water surrounding every individual cell, radiation will still get through to your important stuff. These small particles always have a chance to pass your skin, and blood and water and interact with a cell. Generally the simple way of thinking about radiation damage is the particles hit your DNA and knock pieces out of it, ripping pages out of the instruction manual of you per se, so when those cells reproduce, they get it wrong, and then those daughter cells are also messed up, and they reproduce wrong too now, after generations of cell reproduction then you have a mass of messed up cells. Cancer.
Latest Answers