23 research outputs found
On the gravitational redshift
The study of the gravitational redshift\,---\,a relative wavelength increase
of was predicted for solar radiation by Einstein in
1908\,---\,is still an important subject in modern physics. In a dispute
whether or not atom interferometry experiments can be employed for
gravitational redshift measurements, two research teams have recently disagreed
on the physical cause of the shift. Regardless of any discussion on the
interferometer aspect\,---\,we find that both groups of authors miss the
important point that the ratio of gravitational to the electrostatic forces is
generally very small. For instance, the gravitational force acting on an
electron in a hydrogen atom situated in the Sun's photosphere to the
electrostatic force between the proton and the electron is approximately . A comparison of this ratio with the predicted and observed
solar redshift indicates a discrepancy of many orders of magnitude. Here we
show, with Einstein's early assumption of the frequency of spectral lines
depending only on the generating ion itself as starting point, that a solution
can be formulated based on a two-step process in analogy with Fermi's treatment
of the Doppler effect. It provides a sequence of physical processes in line
with the conservation of energy and momentum resulting in the observed shift
and does not employ a geometric description. The gravitational field affects
the release of the photon and not the atomic transition. The control parameter
is the speed of light. The atomic emission is then contrasted with the
gravitational redshift of matter-antimatter annihilation events.Comment: 19 Pages; 2 Table
Impact Models of Gravitational and Electrostatic Forces
The far-reaching gravitational force is described by a heuristic impact model with hypothetical massless entities propagating at the speed of light in vacuum transferring momentum and energy between massive bodies through interactions on a local basis. In the original publication in 2013, a spherical symmetric emission of secondary entities had been postulated. The potential energy problems in gravitationally and electrostatically bound two-body systems have been studied in the framework of this impact model of gravity and of a proposed impact model of the electrostatic force. These studies have indicated that an antiparallel emission of a secondary entity—now called graviton—with respect to the incoming one is more appropriate. This article is based on the latter choice and presents the modifications resulting from this change. The model has been applied to multiple interactions of gravitons in large mass conglomerations in several publications. They will be summarized here taking the modified interaction process into account. In addition, the speed of photons as a function of the gravitational potential is considered in this context together with the dependence of atomic clocks and the redshift on the gravitational potential
Plasma flows in the cool loop systems
We study the dynamics of low-lying cool loop systems for three datasets as
observed by the Interface Region Imaging Spectrograph (IRIS). Radiances,
Doppler shifts and line widths are investigated in and around observed cool
loop systems using various spectral lines formed between the photosphere and
transition region (TR). Footpoints of the loop threads are either dominated by
blueshifts or redshifts. The co-spatial variation of velocity above the
blue-shifted footpoints of various loop threads shows a transition from very
small upflow velocities ranging from (-1 to +1) km/s in the Mg\,{\sc ii} k line
(2796.20~\AA; formation temperature: log (T/K) = 4.0) to the high upflow
velocities from (-10 to -20) km/s in Si\,{\sc iv}. Thus, the transition of the
plasma flows from red-shift (downflows) to the blue-shift (upflows) is observed
above the footpoints of these loop systems in the spectral line C\,{\sc ii}
(1334.53~\AA; \log (T/K) = 4.3) lying between Mg\,{\sc ii} k and Si\,{\sc iv}
(1402.77~\AA; log (T / K) = 4.8). This flow inversion is consistently observed
in all three sets of the observational data. The other footpoint of loop system
always remains red-shifted indicating downflowing plasma. The multi-spectral
line analysis in the present paper provides a detailed scenario of the plasma
flows inversions in cool loop systems leading to the mass transport and their
formation. The impulsive energy release due to small-scale reconnection above
loop footpoint seems to be the most likely cause for sudden initiation of the
plasma flows evident at TR temperatures.Comment: 29 Pages, 14 figures, The Astrophysical Journal (in press