Hackaday Forced Into Light Mode

April 1, 2021 by Elliot Williams 94 Comments

Hackaday has always been dark mode. Gray10 is less jarring when you’re burning the midnight oil on a project, so we give you a lot of it. Fifteen years ago, it was called “reverse video” or “trog mode“, and we were the freaks. We were doing it wrong. We had the colors “backwards”. Dark mode used to be edgy, outré, but dare we say it, a bit sexy.

Hackaday … QuickBooks. Just sayin’.
They even ripped our highlight yellow!

Flash forward, and everyone has come over to the dark side. Facebook has a dark mode. Google has dark mode. Across the Microsoft empire, from Windows 10 to GitHub, you can live your life in the dark. Heck, even the White House has a dark mode! (They call it high-contrast mode, but they’re not fooling anyone.)

Dark mode here, dark mode there. It’s mainstream. Dark mode has become corporate cool which is nobody’s idea of cool.

We’re not saying that all of the aforementioned institutions are biting the Hackaday style, but, well, they’re all biting our style. Where were they when we were the only website on the whole darn Internet with a sensible background color? Huh? Dark-mode-come-latelys!

But Hackaday doesn’t rest on its laurels. We have our fingers on the pulse on the modern hacker. Where previously you would be up late at night researching Hackaday for juicy nuggets of communal wisdom to help out with your current hack, you’re probably “telecommuting” these days — a euphemism for working on your private projects even while the fiery ball is still in the sky. (Wink, wink, nudge, nudge.) It’s only natural that you’d want a lighter background color to match your new lifestyle. We hear you!

So we present you, Hackaday Light Mode™. Enjoy!

[Editor’s note: For historical accuracy, we had phosphor green headings in the very beginning, in place of the jarring white. If you want to relive those glory days of yore, or just to go back to Hackaday in dark mode, there’s always CSS scripting.]

The Difference Between 4WD And AWD

March 31, 2021 by Lewin Day 102 Comments

Car manufacturers will often tout a vehicle’s features to appeal to the market, and this often leads to advertisements featuring a cacophony of acronyms and buzzwords to dazzle and confuse the prospective buyer. This can be particularly obvious when looking at drivelines. The terms four-wheel drive, all-wheel drive, and full-time and part-time are bandied about, but what do they actually mean? Are they all the same, meaning all wheels are driven or is there more to it? Let’s dive into the technology and find out.

Part-Time 4WD

Part-time four-wheel drive is the simplest system, most commonly found on older off-road vehicles like Jeeps, Land Cruisers and Land Rovers up to the early 1990s, as well as pickup trucks and other heavy duty applications. In these vehicles, the engine sends its power to a transfer case, which sends an equal amount of torque to the front and rear differentials, and essentially ties their input shafts together. This is good for slippery off-road situations, as some torque is provided to both axles at all times. However, this system has the drawback that it can’t be driven in four-wheel drive mode at all times. With the front and rear differentials rotating together, any difference in rotational speed between the front and rear wheels — such as from turning a corner or uneven tyre wear — would cause a problem. The drive shaft going to one differential would want to turn further than the other, a problem known as wind-up.

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The $50 Ham: WSPR-ing Around The World

March 25, 2021 by Dan Maloney 18 Comments

Everybody has a bucket list, things to be accomplished before the day we eventually wake up on the wrong side of the grass. Many bucket-list items are far more aspirational than realistic; very few of us with “A trip to space” on our lists are going to live to see that fulfilled. And even the more realistic goals, like the trip to Antarctica that’s been on my list for ages, become less and less likely as your life circumstances change — my wife hates the cold.

Luckily, instead of going to Antarctica by myself — and really, what fun would that be? — I’ve recently been getting some of the satisfaction of world travel through amateur radio. The last installment of “The $50 Ham” highlighted weak-signal digital modes using WSJT-X; in that article, I mentioned a little about the Weak Signal Propagation Reporter, or WSPR. It’s that mode that let me test what’s possible with very low-power transmissions, and allowed me to virtually visit six continents including Antarctica and Sweden-by-way-of-Alaska.

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How Fast Is The Universe Expanding? The Riddle Of Two Values For The Hubble Constant

March 25, 2021 by Moritz v. Sivers 44 Comments

In the last decades, our understanding of the Universe has made tremendous progress. Not long ago, “precision astronomy” was thought to be an oxymoron. Nowadays, satellite experiments and powerful telescopes on earth were able to measure the properties of our Universe with astonishing precision. For example, we know the age of the Universe with an uncertainty of merely 0.3%, and even though we still do not know the origin of Dark Matter or Dark Energy we have determined their abundance with a precision of better than 1%.

There is, however, one value that astronomers have difficulty in pinning down: how fast our universe is expanding. Or, more precisely, astronomers have used multiple methods of estimating the Hubble constant, and the different methods are converging quite tightly on two different values! This clearly can’t be true, but nobody has yet figured out how to reconcile the results, and further observations have only improved the precision, deepening the conflict. It’s likely that we’ll need either new astronomy or new physics to solve this puzzle.

The Discovery of the Expanding Universe

In the 1920s Edwin Hubble used the newly built telescope at Mount Wilson Observatory to study fuzzy objects known as nebulae. Back then, astronomers were arguing whether these nebulae are clouds of stars within our Milky Way or if they are whole different galaxies. Hubble discovered stars within these nebulae whose brightness slowly fades in and out. These were known as Cepheids and previously studied by Henrietta Levitt who showed that there was a tight relationship between the star’s intrinsic brightness and the period of its variation. This means Cepheids could be used as so-called standard candles which refers to objects whose absolute brightness is known. Since there is a simple relationship between how the brightness of an object decreases with distance, Hubble was able to calculate the distance of the Cepheids by comparing their apparent and intrinsic brightness. He showed that the Cepheid stars were not located within our galaxy and that nebulae are actually distant galaxies.

Hubble also measured the velocity at which these distant galaxies are moving away from us by observing the redshifts of spectral lines caused by the Doppler effect. He found that the further away the galaxy is located, the faster it is moving away from us described by a simple linear relationship.

$\bf v = H_0 d$

The parameter H₀ is what is known as the Hubble constant. Later the Belgian priest and physicist Georges Lemaître realized that the velocity-distance relationship measured by Hubble was evidence for the expansion of the Universe. Since the expansion of space itself causes other galaxies to move away from us we are not in any privileged location but the same effect would be measured from any other place in the Universe. An effect that is sometimes illustrated by drawing points on a balloon, when it is inflated the points move away from each other at a speed that depends on their distance. It is also better not to think of the cosmological redshift as being caused by a real velocity as the parameter v in the above equation can easily exceed the speed of light. Continue reading “How Fast Is The Universe Expanding? The Riddle Of Two Values For The Hubble Constant” →

Hey Google, Is My Heart Still Beating?

March 23, 2021 by Tom Nardi 18 Comments

University of Washington researchers studying the potential medical use of smart speakers such as Amazon’s Echo and Google’s Nest have recently released a paper detailing their experiments with non-contact acoustic heartbeat detection. Thanks to their sensitive microphone arrays, normally used to help localize voice commands from the user, the team proposes these affordable and increasingly popular smart home gadgets could lead a double life as unobtrusive life sign monitors. The paper goes so far as to say that even with multiple people in the room, their technique can be used to monitor the heart and respiratory rate of a specific target individual.

Those are some bold claims, but they aren’t without precedent. Previous studies performed at UW in 2019 demonstrated how smart speaker technology could be used to detect cardiac arrest and monitor infant breathing. This latest paper could be seen as the culmination of those earlier experiments: a single piece of software that could not just monitor the vitals of nearby patients, but actually detect a medical emergency. The lifesaving potential of such a program, especially for the very young and elderly, would be incredible.

So when will you be able to install a heart monitor skill on the cheap Echo Dot you picked up on Prime Day? Well, as is often the case with this kind of research, putting the technique to work in the real-world isn’t nearly as easy as in the laboratory. While the concept is promising and is more than worthy of further research, it may be some time before our lowly smart speakers are capable of Star Trek style life-sign detection.

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Science Officer…Scan For Elephants!

March 17, 2021 by Al Williams 29 Comments

If you watch many espionage or terrorism movies set in the present day, there’s usually a scene where some government employee enhances a satellite image to show a clear picture of the main villain’s face. Do modern spy satellites have that kind of resolution? We don’t know, and if we did we couldn’t tell you anyway. But we do know that even with unclassified resolution, scientists are using satellite imagery and machine learning to count things like elephant populations.

When you think about it, it is a hard problem to count wildlife populations in their habitat. First, if you go in person you disturb the target animals. Even a drone is probably going to upset timid wildlife. Then there is the problem with trying to cover a large area and figuring out if the elephant you see today is the same one as one you saw yesterday. If you guess wrong you will either undercount or overcount.

The Oxford scientists counting elephants used the Worldview-3 satellite. It collects up to 680,000 square kilometers every day. You aren’t disturbing any of the observed creatures, and since each shot covers a huge swath of territory, your problem of double counting all but vanishes.

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Design Solutions For The Heat Crisis In Cities Around The World

March 16, 2021 by Lewin Day 75 Comments

It was 1999 when Smash Mouth dropped the smash hit All Star, stating “The ice we skate is getting pretty thin, the water’s getting warm so you might as well swim.” Since then, global temperatures have continued to rise, with no end in sight. Political will has been unable to make any grand changes, and the world remains on track to blow through the suggested hard limits set by scientists.

As a result, heatwaves have become more frequent, and of greater intensity, putting many vulnerable people at risk and causing thousands of deaths each year. This problem is worse in cities, where buildings and roads absorb more heat from the sun than natural landscapes do. This is referred to as the heat island effect, with cities often being several degrees warmer than surrounding natural areas. It’s significant enough that experts are worried some cities could become uninhabitable within decades. Obviously, that’s highly inconvenient for those currently living in said cities. How bad is the problem, and what can be done?

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