The Physics of Bleach

Ever wondered what would happen if you poured bleach into coke? (DON’T TRY THIS AT HOME!!!!!!)

Bleach contains highly reactive molecules, like the loosely-bound sodium hypochlorite that functions as the active ingredient in standard chlorine bleaches like Clorox. When it’s poured onto a stain, (or into a glass of coke) the chlorine-oxygen group sticks to the pigment molecules, bending them out of shape and changing which wavelengths excite their electrons. Like a bent radio antenna, those molecules can no longer absorb or reflect the electromagnetic energy they were previously sensitive to, and the photons pass on through them. When we bleach a ketchup stain, it may look like it comes out of the fabric, but the reality is that the lycopene molecules are still there—they’ve just been rendered invisible by all the extra atoms that have been stuck onto them!

Calculating the Speed of Light

Here is an interesting post explaining how to calculate the speed of light.  Some of the formulas are AP physics level, but the concepts are understandable even if you don’t know exactly how the formulas work.

If you plug in the actual numerical values for the vacuum permittivity and permeability, it works out to 299,792,400 meters per second—precisely the speed of light!

So what does this mean? … [I]t gives us a clue as to why the speed of light in vacuum is what it is; it’s the speed where electric and magnetic forces balance out to create a stable electromagnetic wave packet that can travel indefinitely. Any slower and the photon would come undone, just as the wires would be pushed apart by the electric repulsion. Any faster, and the magnetism would overcome that repulsion and draw them together, collapsing the system. With nothing more than high school-level math, it’s easy to show that the speed of light in a medium (or in the vacuum of space) inevitably arises as a consequence of that medium’s electric permittivity and magnetic permeability.

Physics Phriday: The Tiny Scope of Earth’s Influence

Radio waves travel at the speed of light (186,000 miles/second).  We’ve been using radio since 1895.  Here’s a picture showing how much of the galaxy could have heard our radio waves by now.  Ready to feel a bit small? (click the picture to read the article)


Japan maglev train breaks world speed record again

A Japanese mag-lev train has broken the speed record again.  The train hit 603 km/h (374 mph) during a test run.  At that speed you could get from Houston to Dallas in 38 minutes.


The test run was conducted on an experimental track in Yamanashi prefecture in central Japan