SELF is sometimes as a noun, noting the individual subject to his own contemplation or action, or noting identity o
Two-dimensional visualization of an Alcubierre drive, showing the opposing regions of expanding and contracting spacetime that displace the central region
The Alcubierre drive, Alcubierre warp drive, or Alcubierre metric (referring to metric tensor), is a speculative warp drive idea based on a solution of Einstein's field equations in general relativity as proposed by theoretical physicist Miguel Alcubierre during his PhD study at Cardiff University, Wales, by which a spacecraft could achieve apparent faster-than-light travel if a configurable energy-density field lower than that of vacuum (that is, negative mass) could be created.[1][2]
Rather than exceeding the speed of light within a local reference frame, a spacecraft would traverse distances by contracting space in front of it and expanding space behind it, resulting in effective faster-than-light travel. Objects cannot accelerate to the speed of light within normal spacetime; instead, the Alcubierre drive shifts space around an object so that the object would arrive at its destination more quickly than light would in normal space without breaking any physical laws.[3]
Although the metric proposed by Alcubierre is consistent with the Einstein field equations, construction of such a drive is not necessarily possible. The proposed mechanism of the Alcubierre drive implies a negative energy density and therefore requires exotic matter or manipulation of dark energy.[4] If exotic matter with the correct properties cannot exist, then the drive cannot be constructed. At the close of his original article,[5] however, Alcubierre argued (following an argument developed by physicists analyzing traversable wormholes[6][7]) that the Casimir vacuum between parallel plates could fulfill the negative-energy requirement for the Alcubierre drive. Some research has claimed that such a concept is possible with purely positive energy using 'soliton' waves.[8][9][10][11]
Another possible issue is that, although the Alcubierre metric is consistent with Einstein's equations, general relativity does not incorporate quantum mechanics. Some physicists have presented arguments to suggest that a theory of quantum gravity (which would incorporate both theories) would eliminate those solutions in general relativity that allow for backward time travel (see the chronology protection conjecture) and thus make the Alcubierre drive invalid.
Through advances in prenatal imaging and the field of immunology, the truly wondrous miracle that is pregnancy is now being more fully understood. Two aspects of pregnancy that your readers might be interested in knowing more about relate to the placenta and something known as fetomaternal microchimerism.
As many of your readers may know, the placenta is the organ through which the mother and prenatal child interface. The placenta is an organ that is attached to the inside of the uterus and connects to the prenatal child through the child’s umbilical cord.
What is not as well known about this organ is that the placenta is the only organ in human biology that is made by two persons, together, in cooperation. The placenta is ‘built’ from tissue that is part from mom, and part from the growing baby. Because of this, the placenta is referred to as a ‘feto-maternal’ organ. It is the only organ made by two people, in cooperation with providence. It is the first time mom and her baby come together, ...
