I Am Not A Native Japanese Speaker But The First Word That Comes To Mind Is 懐かしい (natsukashii),

The Fibonacci sequence can help you quickly convert between miles and kilometers

The Fibonacci sequence is a series of numbers where every new number is the sum of the two previous ones in the series.

1, 1, 2, 3, 5, 8, 13, 21, etc. The next number would be 13 + 21 = 34.

Here’s the thing: 5 mi = 8 km. 8 mi = 13 km. 13 mi = 21 km, and so on.

Edit: You can also do this with multiples of these numbers (e.g. 5*10 = 8*10, 50 mi = 80 km). If you’ve got an odd number that doesn’t fit in the sequence, you can also just round to the nearest Fibonacci number and compensate for this in the answer. E.g. 70 mi ≈ 80 mi. 80 mi = 130 km. Subtract a small value like 15 km to compensate for the rounding, and the end result is 115 km.

This works because the Fibonacci sequence increases following the golden ratio (1:1.618). The ratio between miles and km is 1:1.609, or very, very close to the golden ratio. Hence, the Fibonacci sequence provides very good approximations when converting between km and miles.

Curves of constant width

                                                    Source

The width of a circle is constant: its diameter.

But the circle is not the only shape that holds this pristine title. For instance let’s look at the Reuleaux triangle

Reuleaux triangle

A Reuleaux triangle is a shape formed from the intersection of three circular disks, each having its center on the boundary of the other two.

The Reuleaux triangle is the first of a sequence of Reuleaux polygons, curves of constant width formed from regular polygons with an odd number of sides.

Some of these curves have been used as the shapes of coins

To drill square holes.

They are not entirely square, their edges are fillets i.e the edges are rounded and not sharp.

This animation offers a good insight as to why that is so.

And in china, apparently on bicycles.

The man Guan Baihua shows his self-made multi-angle-wheel bicycle on May 6, 2009 in Qingdao of Shandong Province, China. Guan Baihua spent 18 months to complete this strange bicycle.

Other shapes of constant width

There are other shapes of constant width beside the Reuleaux triangle ( that has been discussed in this post ), a whole bunch of them really. Do take a look at them. ( links below )

I will leave you guys with my favorite one.

More:

If this post fascinated you, i strongly suggest you check these out. They go in-depth with the mathematics that underlies these curves and talk about other cool stuff:

An animation of non-circular rollers

Shapes and Solids of Constant Width - Numberphile  

Shapes of constant width

Reuleaux Polygons,           

Edit:

For those who are wondering if these are something that one would stumble upon on a regular basis. You may not find perfect ones but similiar ones definitely.

I found mine on a really old BMI calculator thingy. ( not sure what you would call it )

Have fun exploring !

File Format Posters

By Corkami, “Reverse engineering & visual documentations”

The collection of images includes all kinds of formats — GIF, ZIP and WAV are all represented, but it even gets into some real esoterica — DOLphin format executables are here if you’re a total GameCube fanatic. Each poster breaks down the format into parts, such as the header, metadata and descriptor sections, and come in a variety of formats themselves — most available in SVG, PDF and PNG.

(via Hackaday)

Book Lovers Day - Free Aeronautics e-Books from NASA

Quieting the Boom

The Shaped Sonic Boom Demonstrator and the Quest for Quiet Supersonic Flight.

Download it HERE

Elegance in Flight

A comprehensive History of the F-16XL Experimental Prototype and its Role in our Flight Research. 

Download it HERE

Probing the Sky

Selected National Advisory Committee for Aeronautics (NACA) Research Airplanes and Their Contributions to Flight.

Download it HERE

Cave of the Winds

The huge Langley Full-Scale Tunnel building dominated the skyline of Langley Air Force Base for 81 years (1930–2011). Explore how the results of critical tests conducted within its massive test section contributed to many of the Nation’s most important aeronautics and space programs.

Download it HERE

A New Twist in Flight Research

A New Twist in Flight Research describes the origins and design development of aeroelastic wing technology, its application to research aircraft, the flight-test program, and follow-on research and future applications.

Download it HERE

Sweeping Forward

Developing & Flight Testing the Grumman X-29A Forward Swept Wing Research Aircraft.

Download it HERE

Thinking Obliquely

Robert T. Jones, the Oblique Wing, our AD-1 Demonstrator, and its Legacy.

Download it HERE

The Apollo of Aeronautics

The fuel crisis of the 1970s threatened not only the airline industry but also the future of American prosperity itself. It also served as the genesis of technological ingenuity and innovation from a group of scientists and engineers at NASA, who initiated planning exercises to explore new fuel-saving technologies.

Download it HERE

X-15: Extending the Frontiers of Flight

X-15: Extending the Frontiers of Flight describes the genesis of the program, the design and construction of the aircraft, years of research flights and the experiments that flew aboard them.

Download it HERE

Ikhana

Delve into the story of the Ikhana, a remotely piloted vehicle used by NASA researchers to conduct Earth science research, which became an unexpected flying and imaging helper to emergency workers battling California wildfires.

Download it HERE

NASA’s Contributions to Aeronautics, Volume 1

This first volume in a two-volume set includes case studies and essays on NACA-NASA research for contributions such as high-speed wing design, the area rule, rotary-wing aerodynamics research, sonic boom mitigation, hypersonic design, computational fluid dynamics, electronic flight control and environmentally friendly aircraft technology.

Download it HERE

NASA’s Contributions to Aeronautics, Volume 2

Continue your journey into the world  of NASA’s Contributions to Aeronautics with case studies and essays on NACA-NASA research for contributions including wind shear and lightning research, flight operations, human factors, wind tunnels, composite structures, general aviation aircraft safety, supersonic cruise aircraft research and atmospheric icing.

Download it HERE

Interested in other free e-books on topics from space, science, research and more? Discover the other e-books HERE.

Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com

Southeast Asians on 4/20 be like

Everyone else: SMOKE WEED EVERYDAY

Us: EAT WEED EVERYDAY @useless-indonesiafacts

Aristotle’s Wheel Paradox. Can you figure out what the paradox is? (What doesn’t make sense?) More info at http://mathworld.wolfram.com/AristotlesWheelParadox.html

BHL Book Feature: The Birds of Singapore Island

Our book feature this week is The Birds of Singapore Island (1927), co-authored by John Alexander Strachey Bucknill and Frederick Nutter Chase with SciArt by Gerald Aylmer Levett-Yeats, and published by the Raffles Museum. This work is the first book on the birds of Singapore!

Our featured illustration is a Greater Racket-tailed Drongo (Dicrurus paradiseus platurus). This book is written in an informal, non-scientific style to appeal to tourists and bird enthusiasts, and the description of the Greater Racket-tailed Drongo is a good example of this writing style.

All this week, we will be sharing several of the 31 plates from The Birds of Singapore Island, which was digitized for BHL by National Library Board, Singapore. You can view all of the plates from this work in our Flickr album, and check out our blog post, which was written by Ong Eng Chuan, Senior Librarian of the National Library Board, Singapore. 

fangtooth moray photos by Sacha Lobenstein

Black Holes are not so Black (Part 3) - Gravitational Waves

The existence of Gravitational Waves have been confirmed. But you probably have heard that. In this post, we will break down this profound discovery into comprehend-able chunks.

This is going to be a amazing journey. Ready ?

Redefining Gravity

When we usually talk of Gravitation we are bound to think like Newton, where objects are assumed to exerting a force upon each other.

Like imaginary arrows of force in space. But this picture, although good for high school crumbled, with the advent of Einstein’s theory of Relativity.

What is the Space-Time Fabric?

Think of space-time fabric as an actual cloth of fabric. ( An analogy )

When you place an object on the fabric, the cloth curves. This is exactly what happens in the solar system as well.

The sun with such a huge mass bends the space-time fabric. And the earth and all the planets are kept in orbit by following this curvature that has been made by the sun.

Attributing to the various masses of objects, the way they bend this fabric also varies.

What are Gravitational Waves?

If you drop an object in a medium such as water, they produce ripples that propagate as waves through the medium.

Similarly, Gravitational waves are ripples in space-time fabric produced when you drag heavy objects through space time.

And the nature of these waves is that they don’t require a medium to propagate.

How do you make one?

Everything with mass/energy can create these waves.

Source

Two persons dancing around each other in space too can create gravitational waves. But the waves would be extremely faint.

You need something big and massive accelerating through space-time in order to even detect them.

And orbiting binary stars/black holes are valuable in this retrospect.

How can you detect them?

Let’s turn to the problem to detecting them assuming you do find binary stars/black-holes in the wondrous space to suite your needs.

Well, for starters you cannot use rocks/ rulers to measure them because as the space expands and contracts, so do the rocks. ( the distances will remain same in both the cases )

Here’s where the high school fact that the speed of Light is a constant no matter what plays an important and pivotal role.

If the space expands, the time taken for light to reach from A to B would be longer. And if it contracts, the time taken for it to reach from A to B would be smaller.

PC: PHDComics

By allowing the light waves from the contraction and expansion to interfere with each other, such as done in any interferometry experiment we can detect the expansion or contraction. Voila!

And this is exactly what they did! ( on a macroscopic level ) at LIGO (Laser Interferometer Gravitational-Wave Observatory)

14 September 2015

Two Black Holes with masses of 29 and 36 solar masses merged together some 1.3 Billion light years away.

Two Black Holes colliding is the header animation of the ‘Black Holes are not so Black Series’, in case if you haven’t noticed.

The merger of these two black holes results in the emission of energy equivalent to 3 solar masses as Gravitational Waves.

This signal was seen by both LIGO detectors, in Livingston and Hanford, with a time difference of 7 milliseconds.

And with the measurement of this time difference, physicists have pronounced the existence of Gravitational Waves.

Source

All this is most certainly easily said than done and requires meticulous and extensive research, not to mention highly sensitive instruments.

Had they not have measured this time difference, we might have had to wait for the merger for more massive black holes to collide and maybe even build more sensitive instruments to detect these waves.

And Einstein predicted this a 100 years back!

Mind Blown!

Note: Hope you are able to understand and appreciate the profundity of the discovery done by mankind.

** All animations used here are merely for Educational purposes. If you have any issues, please write to us at : 153armstrong@gmail.com

Categorizing Posts on Tumblr

Millions of posts are published on Tumblr everyday. Understanding the topical structure of this massive collection of data is a fundamental step to connect users with the content they love, as well as to answer important philosophical questions, such as “cats vs. dogs: who rules on social networks?”

As first step in this direction, we recently developed a post-categorization workflow that aims at associating posts with broad-interest categories, where the list of categories is defined by Tumblr’s on-boarding topics.

Methodology

Posts are heterogeneous in form (video, images, audio, text) and consists of semi-structured data (e.g. a textual post has a title and a body, but the actual textual content is un-structured). Luckily enough, our users do a great job at summarizing the content of their posts with tags. As the distribution below shows, more than 50% of the posts are published with at least one tag.

However, tags define micro-interest segments that are too fine-grained for our goal. Hence, we editorially aggregate tags into semantically coherent topics: our on-boarding categories.

We also compute a score that represents the strength of the affiliation (tag, topic), which is based on approximate string matching and semantic relationships.

Given this input, we can compute a score for each pair (post,topic) as:

where

w(f,t) is the score (tag,topic), or zero if the pair (f,t) does not belong in the dictionary W.

tag-features(p) contains features extracted from the tags associated to the post: raw tag, “normalized” tag, n-grams.

q(f,p) is a weight [0,1] that takes into account the source of the feature (f) in the post (p).

The drawback of this approach is that relies heavily on the dictionary W, which is far from being complete.

To address this issue we exploit another source of data: RelatedTags, an index that provides a list of similar tags by exploiting co-occurence patterns. For each pair (tag,topic) in W, we propagate the affiliation with the topic to its top related tags, smoothing the affiliation score w to reflect the fact these entries (tag,topic) could be noisy.

This computation is followed by filtering phase to remove entries (post,topic) with a low confidence score. Finally, the category with the highest score is associated to the post.

Evaluation

This unsupervised approach to post categorization runs daily on posts created the day before. The next step is to assess the alignment between the predicted category and the most appropriate one.

The results of an editorial evaluation show that the our framework is able to identify in most cases a relevant category, but it also highlights some limitations, such as a limited robustness to polysemy.

We are currently looking into improving the overall performances by exploiting NLP techniques for word embedding and by integrating the extraction and analysis of visual features into the processing pipeline.

Some fun with data

What is the distribution of posts published on Tumblr? Which categories drive more engagements? To analyze these and other questions we analyze the categorized posts over a period of 30 days.

Almost 7% of categorized posts belong to Fashion, with Art as runner up.

The category that drives more engagements is Television, which accounts for over 8% of the reblogs on categorized posts.

However, normalizing by the number of posts published, the category with the highest average of engagements per post isGif Art, followed by Astrology.

Last but not least, here are the stats you all have been waiting for!! Cats are winning on Tumblr… for now…