Sound Science Bite: September 9, 2020. "Holy Galloping Glaciers, Batman!"
One of the most troubling glaciers in West Antarctica, the Thwaites Glacier, appears to be in more trouble than previously thought. Scientists watch nervously as this glacier rapidly diminishes. New bathymetry results reported in the journal The Cryosphere just today (Kelly A. Hogan et al and Tom A. Jordon et al) suggest that more warm ocean water is feeding into the point where the glacier is grounded than previous studies indicated. If the entire glacier were to collapse (hopefully not any time soon), sea level would rise over half a meter on average worldwide.
Index of Previous Sound Science Bites
Science News from the American Association for the Advancement of Science
I-10, On Road To Big Bend
Thrust Fault On Us 90
South Rim - Igneous Intrusions
Boot Canyon
Boquillas Canyon Fault
Heroic Effort at Grapevine Hills
Chihuahuan Greater Earless Lizard
Fossil Near Hot Springs
Volcanic Rock In Tuff Canyon
Rio Grande Terraces
Burro Mesa Pouroff
Inside A Thrust Fault At Dog Canyon
Faulted Fold At Persimmon Gap
Lava Flow Over Alluvium, Rancherias Canyon
Sitting On A Dike - Lost Mine Trail
Agave Above Juniper Canyon - Lost Mine Trail
Native American Petroglyphs - Chimneys
Oak Creek Pouroff - Only Water Outlet From The Basin
Carousel Mountain - Dodson Trail
Del Rio Clay On Santa Elena Limestone - Ernst Tinaja
Calcite Crystals - Near Mule Ear Peaks
On Mesa De Anguila
Above Santa Elena Canyon
Cannon holes? - Estufa Canyon
"Hitchcock Rock" - Blue Creek Canyon
Outcrop - Telephone Canyon
Septarian Concretions - Banta Shut-In
Tornillo Graben
Cattail Falls
Giant Dagger at Devils Den
Mule Ear Peaks
Thrust Fault Drag Folds - Strawhouse Trail
Dike Swarm Radiating from Dominguez Mountain
Animal Den in Tornillo Flat
Hoodoos in Tornillo Flat
Build a Wall Along the Rio Grande? Hell No!
"You can have my rock hammer when you pry it from my cold, dead fingers."
These three paradoxes (Vaidman's paradox, Mansuripur's paradox, the Aharonov-Casher effect) and be resolved without assuming hidden momentum exists in charge-magnet systems or an induced electric dipole resides on a moving magnet.
Redfern, F. Canadian Journal of Physics, 2019, 97(2): 125-132
There is no charge separation on a moving magnetic dipole. The apparent presence of charge is due to the relativity of simultaneity. An electric dipole does not appear on a moving magnetic dipole and a magnetic dipole does not appear on a moving electric dipole. I argue that the magnetization-polarization tensor is not a genuine four-tensor and is not a valid way to find transformed fields. Only the Lorentz transformation of fields directly can give the correct transformed fields.
Correction: The magnetization-polarization tensor is a relativistic four-tensor if you transform the space and time coordinates the elements of the tensor depend upon at the same time you transform the tensor.
Redfern, F. Eur. Phys. J. D (2017) 71: 325.
Magnetic coils in electric fields contain no hidden momentum.
Redfern, F. Eur. Phys. J. D (2017) 71: 163.
In 1967 Shockley and James addressed the situation of a magnet in an electric field. The magnet is at rest and contains electromagnetic momentum, but there was no obvious mechanical momentum to balance this for momentum conservation. They concluded that some sort of mechanical momentum, which they called “hidden momentum”, was contained in the magnet and ascribed this momentum to relativistic effects, a contention that was apparently confirmed by Coleman and an Vleck. Since then, a magnetic dipole in an electric field has been considered to have this new form of momentum, but this view ignores the electromagnetic forces that arise when an electric field is applied to a magnet or a magnet is formed in an electric field. The electromagnetic forces result in the magnet gaining electro- magnetic momentum and an equal and opposite amount of mechanical momentum so that it is moving in its original rest frame. This moving reference frame is erroneously taken to be the rest frame in studies that purport to show hidden momentum. Here I examine the analysis of Shockley and James and of Coleman and Van Vleck and consider a model of a magnetic dipole formed in a uniform electric field. These calculations show no hidden momentum.
Redfern, F. Phys.Scr, (2016) 91: 045501.
Updated discussion of hidden momentum, the Mansuripur paradox, moving dipoles, and electromagnetic momentum in a charge-dipole system. Also, analysis of the paradox involving a magnetic dipole moving in an electric field and the Aharonov-Casher effect.
A discussion of this paradox and momentum flow
I show that the usual harmonic plane-wave equation can be derived from kinematic principles only; that is, requiring the wave to propagate without changing shape in a non-dissipative medium. Not only can the usual second order wave equation be acquired this way, but also an equation that is quadratic and of first order. These equations have a common set of solutions. The second-order equation corresponds to the restoring forces of a physical medium whereas the first-order quadratic equation corresponds to energy in a conservative medium. Properties of electromagnetic waves, including energy conservation (Poynting's theorem) and radiation pressure can be obtained from this kinematic approach.