optics

10

A 200 Year Old Lesson: Scientific Predictions Are Worthless Unless Tested

“So the next time you run across what appears to be a theoretical absurdity, either because you believe such a thing must be so or cannot be so, don’t forget the vital importance of putting it to the experimental test! It’s the only Universe we have, and no matter how solid the footing of our theoretical predictions, they must always be subject to the scrutiny of unrelenting and continuous tests. After all, you never know what secrets the Universe will reveal about itself until you look!”

For centuries, Newton’s theoretical predictions were as unassailable as physics got. His ideas about mechanics, gravitation and optics passed test after test after test. Yet around the dawn of the 19th century, one class of observations appeared to run counter to his assertions: light appeared to exhibit a wave-like nature. The phenomena of diffraction and interference could not be well-explained by a corpuscular theory of light. Towering scientific figures such as Fresnel, Fraunhofer and Poisson calculated what they expected from a wave-like theory under various conditions, with Poisson getting the most absurd result. In theory, light that was shined around a spherical obstacle should produce a shadow… with a brilliant bright spot at the center. This was ruled a victory by Newton for all, proving the wave nature of light’s absurdity.

Fools! For you cannot simply claim an absurdity without doing the experiment to check! The results, the lessons, and the work of Francois Arago must never be forgotten.

This is Alexandrite, it’s also called “emerald by day, ruby by night”

It changes colour based on whether the light source is from the sun or from a candle.

It does this because Alexandrite strongly absorbs yellow light due to chromium ions in its crystal structure, leaving the other colours behind. Light from the Sun emits all colours, but it peaks in the green, and our eyes are most sensitive to green, so in Sunlight Alexandrite is green.

Incandescent lights are things like candles and filament light bulbs. They also emit all colours of light, but they peak far, far into the red, so there’s not nearly as much green or blue, so under those, Alexandrite is red. 

Gemstones are awesome.

Stars align in test supporting 'spooky action at a distance'

Quantum entanglement may appear to be closer to science fiction than anything in our physical reality. But according to the laws of quantum mechanics – a branch of physics that describes the world at the scale of atoms and subatomic particles – quantum entanglement, which Einstein once skeptically viewed as “spooky action at a distance,” is, in fact, real.

Imagine two specks of dust at opposite ends of the universe, separated by several billion light years. Quantum theory predicts that, regardless of the vast distance separating them, these two particles can be entangled. That is, any measurement made on one will instantaneously convey information about the outcome of a future measurement on its partner. In that case, the outcomes of measurements on each member of the pair can become highly correlated.

Keep reading

9

Hummingbirds: among the smallest but most stunning of birds

Tracy Johnson has had hummingbird feeders in her yard in California for the past 20 years and eventually got the birds used to being photographed. She has several plants in the yard that they love and uses also a handheld feeder to help her capture closeup photos.
These amazing colors many male hummingbirds demonstrate result both from pigmentation in the feathers and from prism-like cells within the top layers of feathers to impress females and serve territorial competition.

Here’s how tiny their feathers are:

all images by Tracy Johnson

10

Quiet Riot with @silencerco and their Saker 7.62 with muzzle brake, Saker 7.62 without muzzle brake, and Omega Silencers. Noveske SBR, and full size rifle with Trijicon ACOG, and EOTECH.

This is the first ever silicon nanocomposite

Scientists at the Technical University of Munich (TUM) have developed a stable composite material that can be processed with standard polymer technology. Credit: Tobias Helbich / TUM

Like graphene (the two-dimensional honeycomb form of carbon), silicon forms atom-thick networks known as nanosheets. Now, researchers at the Technical University of Munich (TUM), Germany, have embedded these sheets into a polymer for the first time, physically stabilising the nanosheets and protecting them from decay and oxidation.

‘Silicon nanosheets are particularly interesting because today’s information technology builds on silicon and, unlike with graphene, the basic material does not need to be exchanged,’ explains Tobias Helbich from the WACKER Chair for Macromolecular Chemistry at TUM. ‘However, the nanosheets themselves are very delicate and quickly disintegrate when exposed to UV light, which has significantly limited their application thus far.’ 

The nanosheets could be used in flexible displays, field-effect transistors and, because of silicon’s ability to store lithium ions, are being considered as an anode material for rechargeable batteries. 

In fact, colleagues at TUM’s Institute of Nanoelectronics have already built a working photodetector based on the new nanosheets.  

Originally posted by thefilmstage