#PhysicsFactlet:
Signals (e.g. light) move at a finite speed, so there is a time lag between when they are emitted and when they are detected. If the source is moving, the detector will "see" the signal that was emitted at a previous time, not the signal that is being emitted right now, and this time lag can change with time in a complicated way.
(Notice that, as the source is always moving slower than the signal, the detector sees the signals in the same order they were emitted.) #Physics#ITeachPhysics#Electrodynamics#Optics#Relativity
As someone working in #Optics, it will never cease to amaze me how easy it is for people to misunderstand each other when the word "mode" enters the discussion.
(To be fair, the proper definition of "mode" in #electrodynamics is far from obvious and/or trivial.)
Neurons forge direct physical connections to create functional networks. What drives these circuits and networks to come together? New evidence suggests that some of this coordination comes from electric fields.
@ekmiller Oh My Various Goddess Abstractions. This is so incredibly beautiful 😍
STDP reveals that timing reshapes connections.
This paper reveals how, and it's... musical.
The brain as an "instrument" takes on new meaning.
In the early 20th century, G. Schott set out to develop a model that would explain atomic #spectra and radioactivity, from classical #electrodynamics (from Maxwell's equations). As it turned out, he unwittingly discovered the mechanism of synchrotron radiation instead.
He was a German physicist and, together with Carl Friedrich Gauss, inventor of the first electromagnetic telegraph, which connected the observatory with the institute for physics in Göttingen.
The first usage of the letter "c" to denote the speed of light was in an 1856 paper by Kohlrausch and Weber (Elektrodynamische Maassbestimmungen). The SI unit of magnetic flux, the weber (symbol: Wb) is named after him. via @Wikipedia
Short story time:
When I was doing my PhD, we had in the lab an old Argon laser (which we used to pump a Ti:Sapphire, for those familiar with lasers). If you have never seen one, Argon lasers are massive, can output a ton of power, and eat a crazy amount of current, so much that the laser had its own dedicated industrial pentaphase plug.
I don't remember how many Amperes of current flew in those cables. What I remember is that, when you turned on the switch in the morning, the change in current (from zero to whatever the steady state value was) was enough to make the cable shake.
This happens because the electromagnetic field inside and around the cable stores momentum, and so it kicked the cable when building up.
I am not sure that laser still exists, and I have never been able to find a video of a cable shaking when the current is switched on, but it would be great to have such a video when teaching electrodynamics (and in particular how momentum and angular momentum can be stored in an electromagnetic field). #ITeachPhysics#Physics#Electrodynamics#Laser