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Lightsails are a promising spacecraft concept that can reach relativistic speeds via propulsion by laser light, allowing travel to nearby stars within a human lifetime. The success of a lightsail mission requires that any motion in the…
Exact solutions of traversable wormholes were recently found under the assumption of spherical symmetry and the existence of a non-static conformal symmetry. In this paper, we verify that in the case of the conformally symmetric spacetimes…
It is shown in a variant of two dimensional dilaton gravity theories that an arbitrary, localized massive source put in an initially regular spacetime gives rise to formation of the wormhole classically, without accompanying the curvature…
In general relativity, traversable wormholes are possible provided they do not represent shortcuts in the spacetime. Einstein equations, together with the achronal averaged null energy condition, demand to take longer for an observer to go…
The concept of an objective spatial direction in special relativity is investigated and theories assuming light-speed isotropy while accepting the existence of a privileged spatial direction are classified. A natural generalization of the…
In this talk I discuss pertinence of the wormholes to the problem of circumventing the light speed barrier and present a specific class of wormholes. The wormholes of this class are static and have arbitrarily wide throats, which makes them…
Real Time Relativity is a computer program that allows the user to fly through a virtual world governed by relativistic physics. The user controls a 'rocket' carrying a 'camera'. The rocket may be accelerated and steered, and the camera may…
The visual distortion effects visible to an observer traveling around and descending to the surface of an extremely compact star are described. Specifically, trips to a ``normal" neutron star, a black hole, and an ultracompact neutron star…
We consider the linear kinematics of large-scale peculiar motions in a perturbed Friedmann universe. In so doing, we take the viewpoint of the "real" observers that move along with the peculiar flow, relative to the smooth Hubble expansion.…
Over the last few decades, a plethora of modifications to general relativity have been proposed to solve a host of cosmological and astrophysical problems. Many modified gravity models are now ruled out with further astrophysical…
The concept of a physical space, which actualizes Euclidean geometry, is not confined to the statics of solids but extensible to the phenomena where Newtonian mechanics is valid, defining its concept of time. The laws of propagation of…
In this paper, we propose novel methods to increase total luminosity and decrease error propagation during subluminal or luminal interstellar transits by navigation with star maps. We demonstrate with theoretical and simulation models in…
Gravitational radiation is an elusive form of radiation predicted by general relativity, it is the subject of intense theoretical and experimental research at the limit of the sensitivity of today's instrumentation. In spite of the fact…
Using spacetime algebra, the geometric algebra of spacetime, the general problem of relativistic addition of velocities is addressed. The successive application of non-collinear Lorentz boosts is then studied in Minkowski spacetime. Even…
The current acceleration of the universe leads us to investigate higher dimensional gravity theory, which is able to explain acceleration from a theoretical view point without the need of introducing dark energy by hand. We argue that the…
A gravitational theory with derivative matter coupling is proposed which adopt de Sitter expansion at late times with ordinary baryonic matter. Matter components are conserved separately in the cosmological background and the Newtonian…
It is commonly asserted that superluminal particle motion can enable backward time travel, but little has been written providing details. It is shown here that the simplest example of a "closed loop" event -- a twin paradox scenario where a…
Real Time Relativity is a computer program that lets students fly at relativistic speeds though a simulated world populated with planets, clocks, and buildings. The counterintuitive and spectacular optical effects of relativity are…
Hubble's correlation of red-shift with distance reveals that the universe is expanding, and that spacetime curvature has increased over time. And since time and space have equal status as dimensions, an object moving through time…
In this work we demonstrate that wormholes can in principle be naturally created during the cosmological bounce without the need for the exotic matter or any kind of additional modifications of the gravitational sector, apart from the one…