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kottke.org posts about physics

Carl Sagan explains the fourth dimension

posted by Jason Kottke   Dec 06, 2016

From his seminal TV program Cosmos, Carl Sagan attempts to explain the fourth dimension of spacetime. The story starts with Edwin Abbott’s Flatland, but Sagan being Sagan, his explanation is especially lucid.

We Work Remotely

The Map of Physics

posted by Jason Kottke   Dec 01, 2016

In this video, physicist Dominic Walliman explains how all of the various disciplines of physics are related to each other by arranging them on a giant map. He starts with the three main areas — classical physics, quantum mechanics, and relativity — and then gets into the more specific subjects like optics, electromagnetism, and particle physics before venturing across The Chasm of Ignorance (dun dun DUN!) where things like string theory and dark matter dwell.

Posters of The Map of Physics are available.

NASA’s analysis of seemingly impossible engine: it works

posted by Jason Kottke   Nov 21, 2016

EM Drive NASA

NASA has published their highly anticipated and peer-reviewed analysis of the EM Drive and they’ve concluded the engine works despite appearing to violate Newton’s third law of motion.

In case you’ve missed the hype, the EM Drive, or Electromagnetic Drive, is a propulsion system first proposed by British inventor Roger Shawyer back in 1999.

Instead of using heavy, inefficient rocket fuel, it bounces microwaves back and forth inside a cone-shaped metal cavity to generate thrust.

According to Shawyer’s calculations, the EM Drive could be so efficient that it could power us to Mars in just 70 days.

But, there’s a not-small problem with the system. It defies Newton’s third law, which states that everything must have an equal and opposite reaction.

According to the law, for a system to produce thrust, it has to push something out the other way. The EM Drive doesn’t do this.

Yet in test after test it continues to work. Last year, NASA’s Eagleworks Laboratory team got their hands on an EM Drive to try to figure out once and for all what was going on.

There’s a lot of skepticism around this project, but NASA’s review is definitely a boost to the EM Drive’s credibility.

Update: Just to reiterate, even with this latest paper, there is still skepticism about the EM Drive.

In the end, we can’t conclude that this is a null result, nor can we excitedly say that it works. The sad truth is that this paper is not much better than the researchers’ last one, and it doesn’t actually have enough detail to let us fully evaluate the data. Nor does the paper have enough data to allow a conclusion in the absence of a model. And despite mention of a model in the paper, any model that exists is very well hidden.

Also a clue that the science isn’t quite there on this one yet: very few mainstream science outlets covered this. When the NY Times picks this up and gets prominent physicists on the record about the thruster’s promise, that’s when you’ll know something’s up. Until then, remain skeptical. (via @paudo)

The Most Efficient Way to Destroy the Universe

posted by Jason Kottke   Oct 24, 2016

Kurzgesagt shares a speculative bit of physics called vacuum decay that could very efficiently erase the entire Universe.

To understand vacuum decay, you need to consider the Higgs field that permeates our Universe. Like an electric field, the Higgs field varies in strength, based on its potential. Think of the potential as a track on which a ball is rolling. The higher it is on the track, the more energy the ball has.

The Higgs potential determines whether the Universe is in one of two states: a true vacuum, or a false vacuum. A true vacuum is the stable, lowest-energy state, like sitting still on a valley floor. A false vacuum is like being nestled in a divot in the valley wall — a little push could easily send you tumbling. A universe in a false vacuum state is called “metastable”, because it’s not actively decaying (rolling), but it’s not exactly stable either.

There are two problems with living in a metastable universe. One is that if you create a high enough energy event, you can, in theory, push a tiny region of the universe from the false vacuum into the true vacuum, creating a bubble of true vacuum that will then expand in all directions at the speed of light. Such a bubble would be lethal.

Such a process could already be underway, but don’t worry:

But even if one or multiple spheres of death have already started expanding, the Universe is so big they might not reach us for billions of years.

Scientists accidentally discover a process to turn CO2 into fuel

posted by Jason Kottke   Oct 19, 2016

Scientists at Oak Ridge National Laboratory have stumbled upon a process that uses “nanospikes” to turn carbon dioxide into ethanol, a common fuel.

This process has several advantages when compared to other methods of converting CO2 into fuel. The reaction uses common materials like copper and carbon, and it converts the CO2 into ethanol, which is already widely used as a fuel.

Perhaps most importantly, it works at room temperature, which means that it can be started and stopped easily and with little energy cost. This means that this conversion process could be used as temporary energy storage during a lull in renewable energy generation, smoothing out fluctuations in a renewable energy grid.

This sounds like a big deal…is it now possible to limit the effects of climate change by sinking carbon while also placing less dependence on fossil fuels? Here’s the Oak Ridge press release. That this news is almost a week old already and we haven’t heard more about it makes me a bit skeptical as to the true importance of it. (Of course, CRISPR is potentially a massive deal and we don’t hear about it nearly enough so…)

Update: A relevant series of tweets from Eric Hittinger on “why creating ethanol from CO2 cannot solve our energy or climate problems”. Wasn’t fully awake when I posted this apparently because, yeah, duh. (via @leejlh)

A well-designed reissue of Newton’s Principia

posted by Jason Kottke   Oct 18, 2016

Newton Principia

Small Spanish publisher Kronecker Wallis is doing a Kickstarter campaign to print a well-designed version of Isaac Newton’s Principia, one of the most important texts in science.

We have spent several months working on a desire. The desire to have a new edition of Isaac Newton’s Principia in our hands that is on a par with the importance of the text and of modern editorial design. To put it back on our shelves so that we can leaf through it from time to time and feel the pages beneath our fingers.

An opportunity has now arisen. Taking advantage of the fact that the original publication is to celebrate its 330th anniversary in 2017, we wish to republish it with an editorial design that pays attention to every last detail.

I am enjoying this trend of reviving old classics through the lens of modern design and packaging; see also the NYCTA Graphics Standards Manual, the NASA Graphics Standards Manual, and the Voyager Golden Record.

Richard Feynman’s Tiny Machines

posted by Jason Kottke   Oct 06, 2016

In 1959, physicist Richard Feynman, who had already done work that would win him the Nobel Prize a few years later, gave a talk at Caltech that didn’t have much to do with his main areas of study. The talk was called There’s Plenty of Room at the Bottom and it was a scientist at the peak of his formidable powers asking a question of the scientific community: What about nanotechnology?

I would like to describe a field, in which little has been done, but in which an enormous amount can be done in principle. This field is not quite the same as the others in that it will not tell us much of fundamental physics (in the sense of, “What are the strange particles?”) but it is more like solid-state physics in the sense that it might tell us much of great interest about the strange phenomena that occur in complex situations. Furthermore, a point that is most important is that it would have an enormous number of technical applications.

Even though he made no formal contribution to the field, Feynman’s talk has been credited with jumpstarting interest in the study of nanotechnology. No recording exists of the original talk, but in 1984, Feynman gave a talk he called Tiny Machines, in which he recalled his original talk and spoke of the progress that had been made over the past 25 years. (via @ptak)

How German physicists reacted to the Hiroshima bomb

posted by Jason Kottke   Oct 03, 2016

During World War II, a group of scientists led by Werner Heisenberg worked on designing a nuclear weapon for Nazi Germany. They were, thankfully, unsuccessful. After the war, the Allies detained ten German scientists in England for six months. Hoping to learn about the German bomb program, they secretly taped the scientists’ conversations. In August 1945, the scientists were told about the US dropping a nuclear bomb on Japan. Here’s a transcript of the resulting reaction and conversation.

Shortly before dinner on the 6th August I informed Professor HAHN that an announcement had been made by the B.B.C. that an atomic bomb had been dropped. HAHN was completely shattered by the news and said that he felt personally responsible for the deaths of hundreds of thousands of people, as it was his original discovery which had made the bomb possible. He told me that he had originally contemplated suicide when he realized the terrible potentialities of his discovery and he felt that now these had been realized and he was to blame. With the help of considerable alcoholic stimulant he was calmed down and we went down to dinner where he announced the news to the assembled guests.

“Professor HAHN” is Otto Hahn, who co-discovered nuclear fission in Germany right before the war and won the 1944 Nobel Prize in Chemistry for it. The rest of the world may have gotten there eventually, but think of how different the war (and resulting Cold War period) would have been if Germany had sequestered their scientific progress a couple years earlier or if Hahn and Lise Meitner had made the discovery a year or two later.

WEIZSÄCKER: I think it’s dreadful of the Americans to have done it. I think it is madness on their part.

HEISENBERG: One can’t say that. One could equally well say “That’s the quickest way of ending the war.”

HAHN: That’s what consoles me.

HAHN: I was consoled when, I believe it was WEIZSÄCKER said that there was now this uranium - I found that in my institute too, this absorbing body which made the thing impossible consoled me because when they said at one time one could make bombs, I was shattered.

WEIZSÄCKER: I would say that, at the rate we were going, we would not have succeeded during this war.

HAHN: Yes.

WEIZSÄCKER: It is very cold comfort to think that one is personally in a position to do what other people would be able to do one day.

I particularly like Heisenberg’s distinction between between theoretical and applied science:

There is a great difference between discoveries and inventions. With discoveries one can always be skeptical and many surprises can take place. In the case of inventions, surprises can really only occur for people who have not had anything to do with it. It’s a bit odd after we have been working on it for five years.

If this stuff interests you at all, I’d highly recommend reading Richard Rhodes’ The Making of the Atomic Bomb. (via real future)

Update: The complete transcripts of the secret recordings were collected into a book called Hitler’s Uranium Club. The story of the Allied sabotage of a key element in producing a German bomb is told in Neal Bascomb’s The Winter Fortress. Alex Wellerstein writes that the Nazis didn’t know very much about the Manhattan Project. (via @CarnegieDeputy, @hellbox, @AtomicHeritage)

Meet the nano sapiens

posted by Jason Kottke   Sep 28, 2016

Nano Sapiens

In a 1959 talk at Caltech titled There’s Plenty of Room at the Bottom, Richard Feynman outlined a new field of study in physics: nanotechnology. He argued there was much to be explored in the realm of the very small — information storage, more powerful microscopes, biological research, computing — and that that exploration would be enormously useful.

I would like to describe a field, in which little has been done, but in which an enormous amount can be done in principle. This field is not quite the same as the others in that it will not tell us much of fundamental physics (in the sense of, “What are the strange particles?”) but it is more like solid-state physics in the sense that it might tell us much of great interest about the strange phenomena that occur in complex situations. Furthermore, a point that is most important is that it would have an enormous number of technical applications.

In a reaction to Elon Musk’s plan to colonize Mars, David Galbraith suggests there might be plenty of room at the bottom for human civilization as well. Don’t colonize Mars, miniaturize humanity. Create nano sapiens.

If we think of this as a design problem, there is a much better solution. Instead of expanding our environment to another planet at massive cost, why wouldn’t we miniaturise ourselves so we can expand without increasing our habitat or energy requirements, but still maintain our ability to create culture and knowledge, via information exchange.

The history of information technology and the preservation of Moore’s law has been driven by exactly this phenomenon of miniaturization. So why shouldn’t the same apply to the post technological evolution of humankind as it approaches the hypothetical ‘singularity’ and the potential ability for us to be physically embodied in silicon rather than carbon form.

When humans get smaller, the world and its resources get bigger. We’d live in smaller houses, drive smaller cars that use less gas, eat less food, etc. It wouldn’t even take much to realize gains from a Honey, I Shrunk Humanity scheme: because of scaling laws, a height/weight proportional human maxing out at 3 feet tall would not use half the resources of a 6-foot human but would use somewhere between 1/4 and 1/8 of the resources, depending on whether the resource varied with volume or surface area. Six-inch-tall humans would potentially use 1728 times fewer resources.1

Galbraith also speculates about nano aliens as a possible explanation for the Fermi paradox:

Interestingly, the same rules of energy use and distance between planets and stars would apply to any extraterrestrial aliens, so one possible explanation for the Fermi paradox is that we all get smaller and less visible as we get more technologically advanced. Rather than favoring interstellar colonization with its mind boggling distances which are impossible to communicate across within the lifetimes of individuals (and therefore impossible to hold together in any meaningful way as a civilization) perhaps advanced civilizations stick to their home planets but just get more efficient to be sustainable.

Humans are explorers. Curiosity about new worlds and ideas is one of humanity’s defining traits. One of the most striking things about the Eames’ Powers of Ten video is how similar outer space and inner space look — vast distances punctuated occasionally by matter. What if, instead of using more and more energy exploring planets, stars, and galaxies across larger and larger distances (the first half of the Eames’ video), we went the other way and focused on using less energy to explore cells, molecules, and atoms across smaller and smaller distances. It wouldn’t be so much giving up human space exploration as it would be exchanging it for a very similar and more accessible exploration of the molecular and atomic realm. There is, after all, plenty of room down there.

Update: I knew the responses to this would be good. Galbraith’s idea has a name: the transcension hypothesis, formulated by the aptly named John Smart. Jason Silva explains in this video:

The transcension hypothesis proposes that a universal process of evolutionary development guides all sufficiently advanced civilizations into what may be called “inner space,” a computationally optimal domain of increasingly dense, productive, miniaturized, and efficient scales of space, time, energy, and matter, and eventually, to a black-hole-like destination. Transcension as a developmental destiny might also contribute to the solution to the Fermi paradox, the question of why we have not seen evidence of or received beacons from intelligent civilizations.

Before we get there, however, there are a few challenges we need to overcome, as Joe Hanson explains in The Small Problem With Shrinking Ourselves:

As it often seems in such matters, science follows science fiction here. In Kurt Vonnegut’s Slapstick (Amazon), the Chinese miniaturize themselves in response to the Earth’s decreasing resources.

In the meantime, Western civilization is nearing collapse as oil runs out, and the Chinese are making vast leaps forward by miniaturizing themselves and training groups of hundreds to think as one. Eventually, the miniaturization proceeds to the point that they become so small that they cause a plague among those who accidentally inhale them, ultimately destroying Western civilization beyond repair.

Blood Music by Greg Bear (Amazon) has a nano-civilization theme:

Through infection, conversion and assimilation of humans and other organisms the cells eventually aggregate most of the biosphere of North America into a region seven thousand kilometres wide. This civilization, which incorporates both the evolved noocytes and recently assimilated conventional humans, is eventually forced to abandon the normal plane of existence in favor of one in which thought does not require a physical substrate.

James Blish’s short story Surface Tension tells the tale of microscopic human colonists. (via @harryh, @mariosaldana, @EndlessForms, @vanjacosic, @chumunculus)

Update: For some years, director Alexander Payne has been working on a film called Downsizing:

“Downsizing,” after all, starts off in Norway and takes place in a not-too-distant future where humans are now able to shrink themselves to 1/8 their size as a means to battle over-consumption and the rapid depletion of earth’s natural resources, thanks to enlightened hippie-like Scandinavian scientists. “Smalls” get small, then become members of small cities (the main characters moves to a city called Leisureland) protected by large nets (keeps the bugs out) and built like Disney’s Celebration Town (all planned, all pre-fabricated). Small people cash-in their savings and retire small; 1 big dollar equals 500 small dollars. Smalls live on less food, less land, and produce less trash. As the story progresses, Americans are free to get small, but in Europe, where resources are beginning to truly run out, legislation arises suggesting 40% of the population get shrunk (whether they like it or not). For the big, the world grows smaller and scarier; for the small, the world grows bigger and scarier.

Word is that Matt Damon will play the lead role. Mr. Payne, consider a title change to “Nano Sapiens”? (via @stephenosberg)

Photo by Poy.

  1. This is not a straightforward matter however. The 6-inch human wouldn’t eat 1728 times less food…that would mean you could live on a Big Mac for a year. Small animals often eat a significant percentage of their body weights each day, which normal-sized humans never approach. For example, according to this chart a grey squirrel weighs about 21 oz and eats about 1.6 oz of food, the equivalent of a 180-pound human eating about 14 pounds of food a day.

A year-long time lapse of the Earth rotating in space

posted by Jason Kottke   Jul 22, 2016

NASA recently released a time lapse video of the Earth constructed from over 3000 still photographs taken over the course of a year. The photos were taken by a camera mounted on the NOAA’s DSCOVR satellite, which is perched above the Earth at Lagrange point 1.

Wait, have we talked about Lagrange points yet? Lagrange points are positions in space where the gravity of the Sun and the Earth (or between any two large things) cancel each other out. The Sun and the Earth pull equally on objects at these five points.

L1 is about a million miles from Earth directly between the Sun and Earth and anything that is placed there will hover there relative to the Earth forever (course adjustments for complicated reasons aside). It is the perfect spot for a weather satellite with a cool camera to hang out, taking photos of a never-dark Earth. In addition to DSCOVR, at least five other spacecraft have been positioned at L1.

L2 is about a million miles from the Earth directly opposite L1. The Earth always looks dark from there and it’s mostly shielded from solar radiation. Five spacecraft have lived at L2 and several more are planned, including the sequel to the Hubble Space Telescope. Turns out that the shadow of the Earth is a good place to put a telescope.

L3 is opposite the Earth from the Sun, the 6 o’clock to the Earth’s high noon. This point is less stable than the other points because the Earth’s gravitational influence is very small and other bodies (like Venus) periodically pass near enough to yank whatever’s there out, like George Clooney strolling through a country club dining room during date night.

And quoting Wikipedia, “the L4 and L5 points lie at the third corners of the two equilateral triangles in the plane of orbit whose common base is the line between the centers of the [Earth and Sun]”. No spacecraft have ever visited these points, but they are home to some interplanetary dust and asteroid 2010 TK7, which orbits around L4. Cool! (via slate)

On the Origins of Life, Meaning, and the Universe Itself

posted by Jason Kottke   Jun 23, 2016

Big Picture Carroll

After an unbelievably stressful and busy winter/spring, I am hoping to find some time to read this summer. One of the books on my short list is Sean Carroll’s The Big Picture, one of those “everything is connected” things I love. From a post by Carroll on what the book’s about:

This book is a culmination of things I’ve been thinking about for a long time. I’ve loved physics from a young age, but I’ve also been interested in all sorts of “big” questions, from philosophy to evolution and neuroscience. And what these separate fields have in common is that they all aim to capture certain aspects of the same underlying universe. Therefore, while they are indisputably separate fields of endeavor — you don’t need to understand particle physics to be a world-class biologist — they must nevertheless be compatible with each other — if your theory of biology relies on forces that are not part of the Standard Model, it’s probably a non-starter. That’s more of a constraint than you might imagine. For example, it implies that there is no such thing as life after death. Your memories and other pieces of mental information are encoded in the arrangement of atoms in your brain, and there’s no way for that information to escape your body when you die.

Yeah, that sounds right up my alley.

What are the physical limits of humanity?

posted by Jason Kottke   May 12, 2016

A new video from Kurzgesagt explores the limits of human exploration in the Universe. How far can we venture? Are there limits? Turns out the answer is very much “yes”…with the important caveat “using our current understanding of physics”, which may someday provide a loophole (or wormhole, if you will). Chances are, humans will only be able to explore 0.00000000001% of the observable Universe.

This video is particularly interesting and packed with information, even by Kurzgesagt’s standards. The explanation of the Big Bang, inflation, dark matter, and expansion is concise and informative…the idea that the Universe is slowly erasing its own memory is fascinating.

The Backyard Astronomer

posted by Jason Kottke   Mar 04, 2016

With the homemade telescope in his backyard observatory, amateur astronomer Gary Hug has discovered over 300 asteroids.

What are gravitational waves?

posted by Jason Kottke   Feb 12, 2016

From PHD Comics, and explanation of what gravitational waves are and why their discovery is so important to the future of science. (via df)

Update: Brian Greene’s explanation of gravitational waves to Stephen Colbert is the best one yet:

Greene is great at explaining physics in terms almost anyone can understand. Even though it’s more than 15 years old now, his book, The Elegant Universe, still contains the best explanation of modern physics (quantum mechanics + relativity) I’ve ever read.

Gravitational waves detected

posted by Jason Kottke   Feb 11, 2016

Lights Askew In Heavens

After a potential detection of gravitational waves back in 2014 turned out to be galactic dust, scientists working on the LIGO experiment have announced they have finally detected evidence of gravitational waves. Nicola Twilley has the scoop for the New Yorker on how scientists detected the waves.

A hundred years ago, Albert Einstein, one of the more advanced members of the species, predicted the waves’ existence, inspiring decades of speculation and fruitless searching. Twenty-two years ago, construction began on an enormous detector, the Laser Interferometer Gravitational-Wave Observatory (LIGO). Then, on September 14, 2015, at just before eleven in the morning, Central European Time, the waves reached Earth. Marco Drago, a thirty-two-year-old Italian postdoctoral student and a member of the LIGO Scientific Collaboration, was the first person to notice them. He was sitting in front of his computer at the Albert Einstein Institute, in Hannover, Germany, viewing the LIGO data remotely. The waves appeared on his screen as a compressed squiggle, but the most exquisite ears in the universe, attuned to vibrations of less than a trillionth of an inch, would have heard what astronomers call a chirp — a faint whooping from low to high. This morning, in a press conference in Washington, D.C., the LIGO team announced that the signal constitutes the first direct observation of gravitational waves.

The NY Times headline above is from when the concept of gravitational lensing suggested by Einstein’s theory of relatively was confirmed in 1919. I thought it was appropriate in this case. Wish they still ran headlines like that.

Update: The LIGO team has detected gravitational waves a second time.

Today, the LIGO team announced its second detection of gravitational waves-the flexing of space and time caused by the black hole collision. The waves first hit the observatory in Livingston, Louisiana, and then 1.1 milliseconds later passed through the one in Hanford, Washington.

By now, those waves are 2.8 trillion or so miles away, momentarily reshaping every bit of space they pass through.

Bill Gates’ tribute to Richard Feynman, “The Best Teacher I Never Had”

posted by Jason Kottke   Jan 29, 2016

As part of a celebration of the legacy of Richard Feynman at Caltech this week, Bill Gates contributed a video about what he learned from Feynman.

In that video, I especially love the way Feynman explains how fire works. He takes such obvious delight in knowledge — you can see his face light up. And he makes it so clear that anyone can understand it.

I love that video as well…just watched it again and it’s so so good.

Quantum Chess: Stephen Hawking vs Paul Rudd

posted by Jason Kottke   Jan 29, 2016

So, this is a time travel movie with Keanu Reeves (narrator) and Alex Winter (director), but it’s not Bill & Ted’s Excellent Adventure, Part 3? No, of course not. It’s actually a video about quantum chess featuring Paul Rudd, Stephen Hawking, and music from The Matrix. Like, WHAT?! If The Chickening hadn’t dropped earlier, this would be the oddest thing you’ll watch this week. (And it’s not quite clear, but the video appears to be an advertisement for a quantum chess game that’s launching on Kickstarter next week. Nothing about this makes any sense…) (via @gavinpurcell)

Black holes explained

posted by Jason Kottke   Dec 16, 2015

Kurzgesagt makes some of the most entertaining science explainers around. Check out their most recent video on black holes.

Cool car built from a battery and two magnets

posted by Jason Kottke   Dec 07, 2015

If you take two circular magnets and slap them on the ends of a AA battery, the resulting axel will drive on a road of aluminum foil. This is called a homopolar motor and it’s one of the simplest machines you can build. How does it work? Well, it’s been awhile since my last electromagnetism class, but the homopolar motor works because the combination of the flow of the electric current (from the battery) and the flow of the magnetic current produces a torque via the Lorenz force. This short video explanation should give you a good idea of the principles involved. (via digg)

A final test of relativity

posted by Jason Kottke   Nov 27, 2015

A European Space Agency probe will be launched into space early next month to help test the last major prediction of Einstein’s theory of general relativity: the existence of gravitational waves.

Gravitational waves are thought to be hurled across space when stars start throwing their weight around, for example, when they collapse into black holes or when pairs of super-dense neutron stars start to spin closer and closer to each other. These processes put massive strains on the fabric of space-time, pushing and stretching it so that ripples of gravitational energy radiate across the universe. These are gravitational waves.

The Lisa Pathfinder probe won’t measure gravitational waves directly, but will test equipment that will be used for the final detector.

LISA Pathfinder will pave the way for future missions by testing in flight the very concept of gravitational wave detection: it will put two test masses in a near-perfect gravitational free-fall and control and measure their motion with unprecedented accuracy. LISA Pathfinder will use the latest technology to minimise the extra forces on the test masses, and to take measurements. The inertial sensors, the laser metrology system, the drag-free control system and an ultra-precise micro-propulsion system make this a highly unusual mission.

(via @daveg)

The space doctor’s big idea

posted by Jason Kottke   Nov 19, 2015

Randall Munroe has a new book coming out called Thing Explainer: Complicated Stuff in Simple Words in which he uses the 1000 most common English words to explain interesting mostly scientific stuff. In a preview of the book, Munroe has a piece in the New Yorker explaining Einstein’s theory of relativity using the same constraint.

The problem was light. A few dozen years before the space doctor’s time, someone explained with numbers how waves of light and radio move through space. Everyone checked those numbers every way they could, and they seemed to be right. But there was trouble. The numbers said that the wave moved through space a certain distance every second. (The distance is about seven times around Earth.) They didn’t say what was sitting still. They just said a certain distance every second.

It took people a while to realize what a huge problem this was. The numbers said that everyone will see light going that same distance every second, but what happens if you go really fast in the same direction as the light? If someone drove next to a light wave in a really fast car, wouldn’t they see the light going past them slowly? The numbers said no-they would see the light going past them just as fast as if they were standing still.

It’s a fun read, but as Bill Gates observed in his review of Thing Explainer, sometimes the limited vocabulary gets in the way of true understanding:1

If I have a criticism of Thing Explainer, it’s that the clever concept sometimes gets in the way of clarity. Occasionally I found myself wishing that Munroe had allowed himself a few more terms — “Mars” instead of “red world,” or “helium” instead of “funny voice air.”

See also Albert Einstein’s Theory of Relativity In Words of Four Letters or Less. You might prefer this explanation instead, in the form of a video by high school senior Ryan Chester:

This video recently won Chester a $250,000 Breakthrough Prize college scholarship.2 Nice work!

  1. Other quibble: I would have called Einstein the time doctor. [cue Tardis noise]

  2. Which reminds me of when I was a high school senior and I showed a clip of Bill & Ted’s Excellent Adventure to my physics class for a report on time travel and wormholes. It’s been all downhill for me since then.

Study: quantum entanglement is real

posted by Jason Kottke   Oct 22, 2015

The scientists who conducted a study at the Delft University of Technology in the Netherlands say they have proved that quantum entanglement is a real effect.

The Delft researchers were able to entangle two electrons separated by a distance of 1.3 kilometers, slightly less than a mile, and then share information between them. Physicists use the term “entanglement” to refer to pairs of particles that are generated in such a way that they cannot be described independently. The scientists placed two diamonds on opposite sides of the Delft University campus, 1.3 kilometers apart.

Each diamond contained a tiny trap for single electrons, which have a magnetic property called a “spin.” Pulses of microwave and laser energy are then used to entangle and measure the “spin” of the electrons.

The distance — with detectors set on opposite sides of the campus — ensured that information could not be exchanged by conventional means within the time it takes to do the measurement.

The study, published in Nature, has yet to be verified, but still, exciting!

Scaling laws and the speed of animals

posted by Jason Kottke   Oct 19, 2015

Animal Speed Scaling

A recent paper found that the time it takes for an animal to move the length of its own body is largely independent of mass. This appears to hold from tiny bacteria on up to whales — that’s more than 20 orders of magnitude of mass. The paper’s argument as to why this happens relies on scaling laws. Alex Klotz explains.

A well-known example is the Square-Cube Law, dating back to Galileo and described quite well in the Haldane essay, On Being the Right Size. The Square-Cube Law essentially states that if something, be it a chair or a person or whatever, were made twice as tall, twice as wide, and twice as deep, its volume and mass would increase by a factor of eight, but its ability to support that mass, its cross sectional area, would only increase by a factor of four. This means as things get bigger, their own weight becomes more significant compared to their strength (ants can carry 50 times their own weight, squirrels can run up trees, and humans can do pullups).

Another example is terminal velocity: the drag force depends on the cross-sectional area, which (assuming a spherical cow) goes as the square of radius (or the two-thirds power of mass), while the weight depends on the volume, proportional to the cube of radius or the first power of mass. As Haldane graphically puts it

“You can drop a mouse down a thousand-yard mine shaft; and, on arriving at the bottom, it gets a slight shock and walks away, provided that the ground is fairly soft. A rat is killed, a man is broken, a horse splashes.”

Scaling laws also come into play in determining the limits of the size of animals: The Biology of B-Movie Monsters.

When the Incredible Shrinking Man stops shrinking, he is about an inch tall, down by a factor of about 70 in linear dimensions. Thus, the surface area of his body, through which he loses heat, has decreased by a factor of 70 x 70 or about 5,000 times, but the mass of his body, which generates the heat, has decreased by 70 x 70 x 70 or 350,000 times. He’s clearly going to have a hard time maintaining his body temperature (even though his clothes are now conveniently shrinking with him) unless his metabolic rate increases drastically.

Luckily, his lung area has only decreased by 5,000-fold, so he can get the relatively larger supply of oxygen he needs, but he’s going to have to supply his body with much more fuel; like a shrew, he’ll probably have to eat his own weight daily just to stay alive. He’ll also have to give up sleeping and eat 24 hours a day or risk starving before he wakes up in the morning (unless he can learn the trick used by hummingbirds of lowering their body temperatures while they sleep).

Is the world real? Or are we all just hallucinating?

posted by Jason Kottke   Oct 16, 2015

Hopes&Fears asked a group of scientists and researchers if reality is actually real or if it’s all an illusion or hallucination.

How do we know this is real life? The short answer is: we don’t. We can never prove that we’re not all hallucinating, or simply living in a computer simulation. But that doesn’t mean that we believe that we are.

There are two aspects to the question. The first is, “How do we know that the stuff we see around us is the real stuff of which the universe is made?” That’s the worry about the holographic principle, for example — maybe the three-dimensional space we seem to live in is actually a projection of some underlying two-dimensional reality.

Why is there something rather than nothing?

posted by Jason Kottke   Oct 05, 2015

That is the question that physicist Lawrence Krauss answers in his book, A Universe from Nothing. The book’s trailer provides a little more context.

Everything we see is just a 1% bit of cosmic pollution in a Universe dominated by dark matter and dark energy. You could get rid of all the things in the night sky — the stars, the galaxies, the planets, everything — and the Universe would be largely the same.

And my favorite line from the trailer:

Forget Jesus, the stars died so you could be born.

(via open culture)

Edward Snowden’s Fermi Paradox solution

posted by Jason Kottke   Sep 21, 2015

Edward Snowden has come up with a solution to the Fermi Paradox that I hadn’t heard of before. Maybe we haven’t discovered intelligent life elsewhere in the Universe, says Snowden, because their communications encryption is indistinguishable from cosmic background radiation.

“If you look at encrypted communication, if they are properly encrypted, there is no real way to tell that they are encrypted,” Snowden said. “You can’t distinguish a properly encrypted communication from random behaviour.”

Therefore, Snowden continued, as human and alien societies get more sophisticated and move from “open communications” to encrypted communication, the signals being broadcast will quickly stop looking like recognisable signals.

“So if you have an an alien civilization trying to listen for other civilizations,” he said, “or our civilization trying to listen for aliens, there’s only one small period in the development of their society when all their communication will be sent via the most primitive and most unprotected means.”

After that, Snowden said, alien messages would be so encrypted that it would render them unrecognisable, “indistinguishable to us from cosmic microwave background radiation”. In that case, humanity would not even realise it had received such communications.

Snowden shared his hypothesis with Neil deGrasse Tyson on Tyson’s podcast, StarTalk.

The Earth’s nuclear scars

posted by Jason Kottke   Sep 15, 2015

Last month I shared a video showing the thousands of nuclear weapons that humans have detonated on Earth. I hadn’t really thought about it too much apart from the two dropped in Japan in WWII, but those weapons created some permanent physical changes in the landscape of the Earth. For instance, dozens of circular scars are visible at this testing range in Nevada near Area 51.

Nuke Blast Holes

Also located in the same area is the Sedan Crater, the largest man-made crater in the United States. The crater is 320 feet deep, 1280 feet across, listed on the National Register of Historic Places, and was made by a thermonuclear device with a 104 kiloton yield detonated in 1962.

Sedan Crater

Now, I haven’t read a whole lot about nuclear tests, but this one seems particularly idiotic. The purpose of the Sedan shot was not to test a new kind of weapon or to determine the effects of the bomb, but to move earth. Yeah, no big deal, we’re just gonna use a fusion bomb like a big stick of dynamite. Sedan was part of Operation Plowshare, an effort to use nuclear devices for peaceful purposes like mining and moving earth. From Wikipedia:

Proposed uses for nuclear explosives under Project Plowshare included widening the Panama Canal, constructing a new sea-level waterway through Nicaragua nicknamed the Pan-Atomic Canal, cutting paths through mountainous areas for highways, and connecting inland river systems. Other proposals involved blasting underground caverns for water, natural gas, and petroleum storage. Serious consideration was also given to using these explosives for various mining operations. One proposal suggested using nuclear blasts to connect underground aquifers in Arizona. Another plan involved surface blasting on the western slope of California’s Sacramento Valley for a water transport project.

The Pan-Atomic Canal! This quaint US government video has more on Sedan:

In my post the other day, I said that the Soviets didn’t care about their citizenry when testing nuclear devices. Apparently the US didn’t either: the Sedan shot — the purpose of which, as a reminder, was to move a bunch of dirt — resulted in a significant amount of nuclear fallout, about 7% of the total radioactive fallout generated by all the nuclear tests in Nevada. Fallout from the test reached as far as West Virginia and was particularly high in counties in Iowa and Illinois. Buy hey, they moved 12 million tons of soil! (via @kyledenlinger)

The varying wavelengths of colors

posted by Jason Kottke   Sep 03, 2015

Rain Bros

Rain-Bros by Daniel Savage is a fun visualization of the different wavelengths of light in the visible spectrum, from the loping walk of red to blue’s energetic bounce.

Everything is made from something

posted by Jason Kottke   Aug 21, 2015

In A Children’s Picture-book Introduction to Quantum Field Theory, Brian Skinner explains quantum field theory — “the deepest and most intimidating set of ideas in graduate-level theoretical physics” — as if you and I are five-year-old children.

The first step in creating a picture of a field is deciding how to imagine what the field is made of. Keep in mind, of course, that the following picture is mostly just an artistic device. The real fundamental fields of nature aren’t really made of physical things (as far as we can tell); physical things are made of them. But, as is common in science, the analogy is surprisingly instructive.

So let’s imagine, to start with, a ball at the end of a spring.

(via @robinsloan)

Supermassive black holes are *really* massive

posted by Jason Kottke   Aug 19, 2015

How massive are they? The Sun is 1 solar mass and as wide as 109 Earths. Sagittarius A, the black hole at the center of the Milky Way, weighs 4.3 million solar masses and is as wide as Mercury is far from the Sun. The black hole at the center of the Phoenix Cluster is one of the largest known black holes in the Universe; it’s 73 billion miles across, which is 19 times larger than our entire solar system (from the Sun to Pluto). As for how much it weighs, check this out:

I also like that if you made the Earth into a black hole, it would be the size of a peanut. (thx, reidar)