Mood

u dont understand how disappointed i am that this dog didnt appear on my dash this year and how hard i tried to find a post that included both pictures

this always gives me solace when i’m feeling alone. the one is out there, just keep looking :)

Royal Air Force mechanics add ballast to a Hawker Hurricane while either its pilot or another mechanic test runs its engine.

It was common, for instance, for a fitter to sit on the tail plane when a Spitfire was taxiing on rough terrain as the aircraft was tail-light and nose-heavy. To prevent the tail bouncing up and the propeller striking the ground, fitters often rode the tailplane all the way to the takeoff point.

This practice had a freak outcome on one occasion when a pilot took off without first allowing his female fitter, Margaret Horton to get off. As strange as it may seem, Horton rode this way, clinging to the vertical stabilizer all the way through a circuit after the pilot suddenly realized what he had done but was too high to land straight ahead.

The story on the BBC People’s War website, written by Mary Blood:

“Involved a W.A.A.F. flight mechanic, ACW Margaret Horton, and a veteran Spitfire. When an aircraft engine had been serviced, the practice was for the training instructors to run the engine and do a particular test. Margaret had finished work on the Spitfire, when the pilot began this test. It was necessary, if it was windy, for a mechanic to sit on the tail of the aircraft while it taxied to the end of the runway ready for takeoff. The mechanics were given the order, ‘Tails’. Having got to the runway, the aircraft would pause for the mechanic to drop off. This time the pilot did not pause. Whether he was unaware that the order to ‘tail’ had been given, nobody knows. He just carried on with Margaret Horton hanging on for grim death, and him unaware that he had a ‘passenger’ on the tail. ‘I thought the aircraft was tail-heavy’, he said later. The Spitfire had risen to 800 feet or more when the strange shape of the tailplane was noticed from the ground. The emergency services were called out and the pilot talked back in without being told what had happened. The aircraft landed safely with Margaret Horton still in one piece. Just how daft the [bureaucratic] machinery of the R.A.F. could be was shown when she was reprimanded for her unofficial flight and charged for the loss of her beret! She was posted later to West Raynham and, despite her ordeal, survived into her eighties.”

This particular 17 Squadron Hurricane (P3482) was lost during the Battle of Britain when it crash landed. Its pilot survived

What is Gravitational Lensing?

A gravitational lens is a distribution of matter (such as a cluster of galaxies) between a distant light source and an observer, that is capable of bending the light from the source as the light travels towards the observer. This effect is known as gravitational lensing, and the amount of bending is one of the predictions of Albert Einstein’s general theory of relativity.

This illustration shows how gravitational lensing works. The gravity of a large galaxy cluster is so strong, it bends, brightens and distorts the light of distant galaxies behind it. The scale has been greatly exaggerated; in reality, the distant galaxy is much further away and much smaller. Credit: NASA, ESA, L. Calcada

There are three classes of gravitational lensing:

1° Strong lensing: where there are easily visible distortions such as the formation of Einstein rings, arcs, and multiple images.

Einstein ring. credit: NASA/ESA&Hubble

2° Weak lensing: where the distortions of background sources are much smaller and can only be detected by analyzing large numbers of sources in a statistical way to find coherent distortions of only a few percent. The lensing shows up statistically as a preferred stretching of the background objects perpendicular to the direction to the centre of the lens. By measuring the shapes and orientations of large numbers of distant galaxies, their orientations can be averaged to measure the shear of the lensing field in any region. This, in turn, can be used to reconstruct the mass distribution in the area: in particular, the background distribution of dark matter can be reconstructed. Since galaxies are intrinsically elliptical and the weak gravitational lensing signal is small, a very large number of galaxies must be used in these surveys.

The effects of foreground galaxy cluster mass on background galaxy shapes. The upper left panel shows (projected onto the plane of the sky) the shapes of cluster members (in yellow) and background galaxies (in white), ignoring the effects of weak lensing. The lower right panel shows this same scenario, but includes the effects of lensing. The middle panel shows a 3-d representation of the positions of cluster and source galaxies, relative to the observer. Note that the background galaxies appear stretched tangentially around the cluster.

3° Microlensing: where no distortion in shape can be seen but the amount of light received from a background object changes in time. The lensing object may be stars in the Milky Way in one typical case, with the background source being stars in a remote galaxy, or, in another case, an even more distant quasar. The effect is small, such that (in the case of strong lensing) even a galaxy with a mass more than 100 billion times that of the Sun will produce multiple images separated by only a few arcseconds. Galaxy clusters can produce separations of several arcminutes. In both cases the galaxies and sources are quite distant, many hundreds of megaparsecs away from our Galaxy.

Gravitational lenses act equally on all kinds of electromagnetic radiation, not just visible light. Weak lensing effects are being studied for the cosmic microwave background as well as galaxy surveys. Strong lenses have been observed in radio and x-ray regimes as well. If a strong lens produces multiple images, there will be a relative time delay between two paths: that is, in one image the lensed object will be observed before the other image.

As an exoplanet passes in front of a more distant star, its gravity causes the trajectory of the starlight to bend, and in some cases results in a brief brightening of the background star as seen by a telescope. The artistic concept illustrates this effect. This phenomenon of gravitational microlensing enables scientists to search for exoplanets that are too distant and dark to detect any other way.Credits: NASA Ames/JPL-Caltech/T. Pyle

Explanation in terms of space–time curvature

Simulated gravitational lensing by black hole by: Earther

In general relativity, light follows the curvature of spacetime, hence when light passes around a massive object, it is bent. This means that the light from an object on the other side will be bent towards an observer’s eye, just like an ordinary lens. In General Relativity the speed of light depends on the gravitational potential (aka the metric) and this bending can be viewed as a consequence of the light traveling along a gradient in light speed. Light rays are the boundary between the future, the spacelike, and the past regions. The gravitational attraction can be viewed as the motion of undisturbed objects in a background curved geometry or alternatively as the response of objects to a force in a flat geometry.

A galaxy perfectly aligned with a supernova (supernova PS1-10afx) acts as a cosmic magnifying glass, making it appear 100 billion times more dazzling than our Sun. Image credit: Anupreeta More/Kavli IPMU.

To learn more, click here. 

i want to know what bears think sometimes

The Tuskegee Airmen, the highly decorated, all-black unit that served in WWII; 1940s

via reddit

JOYLESS

[Unlimited Hate, Black Metal, Norway, ATMF (republication), 1996 (2018 for the republication)]

- https://atmfsssdtp.bandcamp.com/album/unlimited-hate