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kateoplis:

Construction of the Statue of Liberty in Bartholdi’s studio, Paris, 1882-1883

cwnl:

Wormholes

We’ve seen them in our most beloved sci-fi movies (Contact anyone?) and series (Star Trek, Dr. Who), we’ve heard physicists, astrophysicists and astronomers speak of it with great enthusiasm and interest. But what exactly are these cosmic phenomena?

Wormholes are solutions to the Einstein field equations for gravity that act as “tunnels,” connecting points in space-time in such a way that the trip between the points through the wormhole could take much less time than the trip through normal space.

The first wormhole-like solutions were found by studying the mathematical solution for black holes. There it was found that the solution lent itself to an extension whose geometric interpretation was that of two copies of the black hole geometry connected by a “throat” (known as an Einstein-Rosen bridge). The throat is a dynamical object attached to the two holes that pinches off extremely quickly into a narrow link between them.

Theorists have since found other wormhole solutions; these solutions connect various types of geometry on either mouth of the wormhole. One amazing aspect of wormholes is that because they can behave as “shortcuts” in space-time, they must allow for backwards time travel! This property goes back to the usual statement that if one could travel faster than light, that would imply that we could communicate with the past.

Wormhole geometries are inherently unstable. The only material that can be used to stabilize them against pinching off is material having negative energy density, at least in some reference frame. No classical matter can do this, but it is possible that quantum fluctuations in various fields might be able to.

via ScientificAmerican

scipsy:

Penicillium

14-billion-years-later:

How X-rays Work.

X rays hold a certain fascination in their ability to peer into the unknown and see bizarre things like snakes that have ingested light bulbs but like a lot of good things in science, X-rays were discovered entirely by accident. They’re usually attributed to Wilhelm Rontgen who noticed that a film across his lab begun to fluoresce during experiments with a Crooke’s Tube despite taking action to block radiation (in the form of a sheet of black card). It was then discovered that by moving his hand in between the Crooke’s tube and fluorescing screen he could see the bones in his hands.

The ability for X rays to penetrate flesh and render hidden things visible lies in the amount of energy contained within them. They simply cannot be absorbed by most atoms because there is not enough of an energy difference between electron orbitals, as such they pass through most molecules and atoms unhindered. However heavier elements, such as calcium, are capable of absorbing X rays and so effectively block them. The formation of X rays lies in the reverse process. To produce high energy electromagnetic radiation electrons are accelerated and fired at a metal (typically tungsten) plate. These high velocity electrons ionize the metal by bumping off one of electrons in a lower energy orbital causing a higher energy electron to fall to the lower state and emit the difference of energies in the process as an X ray photon.

puella puellae

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puellae puellis

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