Most of you here probably know that our perception of color comes down to physics. Light is a type of radiation that our eyes can perceive, and it spans a certain range of the electromagnetic spectrum. Individual colors are like building blocks in white light: they are subdivisions of the visible spectrum. For us to perceive an object as being of a certain color, it needs to absorb some of the subdivisions in the light that falls on it (or all of them, for black). The parts it reflects (doesn’t absorb) are what gives it its color. But not so for purple, because it is a non-spectral color.
A pair of physicists from MIT and Jefferson Lab and an animator have created a new visualization of the atomic nucleaus.
For the first time, the sizes, shapes and structures of nuclei in the quantum realm are visualized using animations and explained in the video.
The video also establishes what appears to be a new unit of measure with an adorable name, the babysecond:
To better define the velocities of particles at such small distance scales, we establish the baby second as 10^-23 seconds. A photon moving at the speed of light crosses three femtometers (a bit more than the radius of oxygen-16) in one baby second.
In a collaboration with Red Bull & Prada (uh, ok) and with the help of the Polish State Railways, Dawid Godziek rode a mountain bike on a ramps course on top of a moving train, performing tricks & flips between cars. The train and rider moved at the same speed in opposite directions, which made it seem as though, from the perspective of someone on the ground next to the train, that the rider is nearly horizontally stationary.
The result is trippy & counterintuitive and also a demonstration of Newton’s laws of motion & frames of reference. But since Godziek was not riding in a vacuum, there were some real world details to contend with:
We observed something interesting — the lack of air resistance. In theory, this could have made it easier, but the opposite was true. The air resistance creates a tunnel that somehow keeps me in a straight line and doesn’t allow me to shift right or left. Luckily on the recordings we had, the headwind gave me artificial air resistance, which helped me to get a feel for the flight on classic hops. On the tests, the wind was blowing weaker or in a different direction, making shooting tricks difficult. Not bad, right? We’re always complaining about air resistance, and when it wasn’t there, we found that it was impossible to fly without it.
The folks at Kurzgesagt have done a few time travel videos now, but this one is notable for its concise, intuitive explanation and visualization of our constant speed through spacetime (special relativity).
Everything in our universe moves at the speed of light through four dimensional spacetime. Your speed through spacetime is the sum of your separate speeds through time and space. It is impossible for you to stay still. Even if you are not moving through space dimensions, you are moving through the time dimension, blasting face first into the future.
You can slow down in the time dimension, by moving faster through the space dimensions but in total, you will always move at the speed of light through spacetime.
And you can “trade” moving through space for moving through time: “Move faster through space, go slower in time. Move slower through space, go faster in time.” Or as a commenter put it:
Your speed is constant. So the faster you move through the space dimensions, the slower you move through the time dimension, and vice versa.
Not sure this textual explanation makes as much sense as the visualization in the video, so maybe just watch that? Oh, and check out the sources for the video.
Kurzgesagt attempts to answer the question (from the perspective of physics): Do we have free will? Here’s the deterministic perspective (from the show notes):
Now imagine that if right after the Big Bang, a supersmart supercomputer looked at every single particle in the universe and noted all their properties. Just by applying the deterministic laws of physics, it should be able to predict what all the particles in existence would be doing until the end of time.
But if you are made of particles and it’s technically possible to calculate what particles will do forever, then you never decided anything. Your past, present and future were already predetermined and decided at the Big Bang. This would mean there is a kind of fate and you are not free to decide anything.
You may feel like you make decisions, but you are on autopilot. The motions of the particles that make up your brain cells that made you watch this video were decided 14 billion years ago. You are just in the room when it happens. You are only witnessing how the universe inside you unfolds in real time.
And the other side of the argument (in favor of free will):
We know that we can reduce everything that exists to its basic particles and the laws that guide them. While this makes physics feel like the only scientific discipline that actually matters, there is a problem: You can’t explain everything in our universe only from particles.
One key fact about reality that we can’t explain by looking just at electrons and quantum stuff is emergence. Emergence is when many small things together create new fundamental traits that didn’t exist before.
Emergence occurs at all levels of reality, and reality seems to be organized in layers: atoms, molecules, cells, tissues, organs, you, society. Put many things in one layer together and they’ll create the next layer up. Every time they do, entirely new properties emerge.
Having thought about this for all of 20 minutes (or, practically all of my life), the emergence argument against determinism makes a lot of sense to me. Then again, James Gleick’s Chaos and Steven Johnson’s Emergence both made a huge impression on me when I read it more than 20 years ago.
Kurzgesagt is back with another video about black holes; it has the innocuous-seeming title of The Easiest Way To Build a Black Hole. But the main topic of the video is the speculation that universes (like ours!) might exist within black holes.
Black holes might create infinite universes while destroying time and space. Everything in existence could be black holes, all the way down. We might live inside a black hole that is inside a black hole, that is inside a black hole. But let’s start at the beginning and build a black hole out of air.
This one is a bit of a brain-bender. From the show notes:
The first part of the script is based on the empirical fact that, somewhat intriguingly, the observable universe seems to have the exact size and mass that would be required to make a black hole as big as the observable universe itself.
The second, completely independent proposal we explore is the idea that our Universe could be born from the singularity of a black hole, and that in turn the universe that contains that black hole could be born from a black hole itself. If so, universes in later generations of this process could be better fitted to produce an abundance of black holes, in a sort of “natural selection” towards efficient black hole production.
The movies begin with the camera located nearly 400 million miles (640 million kilometers) away, with the black hole quickly filling the view. Along the way, the black hole’s disk, photon rings, and the night sky become increasingly distorted — and even form multiple images as their light traverses the increasingly warped space-time.
In real time, the camera takes about 3 hours to fall to the event horizon, executing almost two complete 30-minute orbits along the way. But to anyone observing from afar, it would never quite get there. As space-time becomes ever more distorted closer to the horizon, the image of the camera would slow and then seem to freeze just shy of it. This is why astronomers originally referred to black holes as “frozen stars.”
At the event horizon, even space-time itself flows inward at the speed of light, the cosmic speed limit. Once inside it, both the camera and the space-time in which it’s moving rush toward the black hole’s center — a one-dimensional point called a singularity, where the laws of physics as we know them cease to operate.
“Once the camera crosses the horizon, its destruction by spaghettification is just 12.8 seconds away,” Schnittman said. From there, it’s only 79,500 miles (128,000 kilometers) to the singularity. This final leg of the voyage is over in the blink of an eye.
Using a scale model of the solar system the size of New York City and some dazzling visual effects, Epic Spaceman explains that black holes are generally smaller than you might think (because they’re so dense) — even the supermassive black hole at the center of our galaxy. But when you consider some of the biggest black holes we’ve discovered…wow.
Is the universe finite or infinite? If finite, what shape is it and how does that shape influence its overall size and properties? If it’s infinite, what meaning of “expanding” can be applied to it? I don’t know if this video provides any satisfying answers, but even being able to ponder these questions is thrilling.
Infinity gets much weirder though. As you travel with your spaceship in a straight line, you find new galaxies, stars and planets, new wonders, new weird stuff, probably new aliens and new lifeforms stranger than you could ever imagine. But after a long time, you might find the most special thing in the universe: Yourself. An exact copy of you watching this video right now.
How can that be? Well, everything in existence is made of a finite amount of different particles. And a finite number of different particles can only be combined in a finite number of ways. That number may be so large that it feels like infinity to our brains — but it is not really. If you have finite options to build things, but infinite space that is full of things in all directions forever, then it makes sense that by pure chance, there will likely be repetition.
Kurzgesagt’s latest video on the paradox of time is a bit more of a brain-bender than their usual videos. From the accompanying sources document:
This video summarizes in a narrative format two well-known theories about time: the so-called “block universe” and the “growing block”.
The block universe is an old theory of time which appears to be an unavoidable consequence of Einstein’s theory of special relativity. In philosophical contexts, basically the same idea is known as “eternalism”. Simplified, this theory posits that, although not apparent to our human perception, both the past and the future exist in the same way as the present does, and are therefore as real as the present is: The past still exists and the future exists already. As a consequence, time doesn’t “flow” (even if it looks so to us) and things in the universe don’t “happen” - the universe just “is”, hence the name “block universe”.
But then: “Quantum stuff is ruining everything again.” And so we have the growing block theory:
The Evolving/Growing Block: A relatively new alternative to the classical block universe theory, which asserts that the past may still exist but the present doesn’t yet, and all that in a way that is still compatible with Einstein’s relativity.
And there are still other theories about how time works:
Some scientists think that the idea of “now” only makes sense near you, but not in the universe as a whole. Others think that time itself doesn’t even exist — that the whole concept is an illusion of our human mind. And others think that time does exist, but that it’s not a fundamental feature of the universe. Rather, time may be something that emerges from a deeper level of reality, just like heat emerges from the motion of individual molecules or life emerges from the interactions of lifeless proteins.
In a video for the Royal Society, physicist Brian Cox explains the science of snowflakes, from how they form to where their shape and symmetry comes from. Plus this bombshell: “Snowflakes aren’t actually white.” (via aeon)
In their latest video, Kurzgesagt takes a break from their more serious topics to consider a scenario from the realm of science fiction: interstellar combat. Using technology that is theoretically available to us here on Earth, could a more advanced civilization some 42 light years away destroy our planet without any warning? They outline three potential weapons: the Star Laser, the Relativistic Missile, and the Ultra-Relativistic Electron Beam.
Here’s what I don’t understand though: how would the targeting work? In order for an alien civilization to hit the Earth with a laser from 42 light years away, it has to not only predict, within a margin of error of the Earth’s diameter, precisely where the Earth is going to be, but also have a system capable of aiming across 42 light years of distance with that precision. Is this even possible? How precisely do we know where the Earth is going to be in 42 years? And if you’re aiming at something 42 light years away, if you move the sights a nanometer, how much angular distance does that shift the the destination by? And how much does the gravity of matter along the way shift the trajectory and is it possible to accurately compensate for that? Maybe this should be their next video…
If you look closely at a rainbow made from sunlight (e.g. through a prism or an actual rainbow), you’ll notice that some of the colors are missing. It turns out that these absent colors (called Fraunhofer lines) have something to do with the types of elements that are present in the Sun (and the Earth’s atmosphere). Dr. Joe Hanson explains in the video above.
Over 200 years ago, scientists were looking at sunlight through a prism when they noticed that part of the rainbow was missing. There were dark lines where there should have been colors. Since then, scientists have unlocked the secrets encoded in these lines, using it to uncover mind-boggling facts about the fundamental nature of our universe and about worlds light-years away.
Science is fascinating…Fraunhofer lines can tell us something about objects and processes all along the Powers of Ten scale, from the inner workings of the atom to the composition of the Earth’s atmosphere to how quickly the universe is expanding or contracting.
Erik Wernquist made his short film One Revolution Per Minute to explore his “fascination with artificial gravity in space”. The film shows what it would be like to travel on a large, circular space station, 900 meters (0.56 miles) in diameter that rotates a 1 rpm. Even at that slow speed, which generates 0.5 g at the outermost shell, I was surprised to see how quickly the scenery (aka the Earth, Moon, etc.) was rotating and how disorienting it would be as a passenger.
Realistically - and admittedly somewhat reluctantly — I assume that while building a structure like this is very much possible, it would be quite impractical for human passengers.
Putting aside the perhaps most obvious problem with those wide windows being a security hazard, I believe that the perpetually spinning views would be extremely nauseating for most humans, even for short visits. Even worse, I suspect — when it comes to the comfort of the experience — would be the constantly moving light and shadows from the sun.
I calculated that the outer ring of the space station is moving at 105.4 mph with respect to the center. That’s motoring right along — no wonder everything outside is spinning so quickly.
You just have to admire a chart that casually purports to show every single thing in the Universe in one simple 2D plot. The chart in question is from a piece in the most recent issue of the American Journal of Physics with the understated title of “All objects and some questions”.
In Fig. 2, we plot all the composite objects in the Universe: protons, atoms, life forms, asteroids, moons, planets, stars, galaxies, galaxy clusters, giant voids, and the Universe itself. Humans are represented by a mass of 70 kg and a radius of 50 cm (we assume sphericity), while whales are represented by a mass of 10^5 kg and a radius of 7 m.
The “sub-Planckian unknown” and “forbidden by gravity” sections of the chart makes the “quantum uncertainty” section seem downright normal — the paper collectively calls these “unphysical regions”. Lovely turns of phrase all.
But what does it all mean? My physics is too rusty to say, but I thought one of the authors’ conjectures was particularly intriguing: “Our plot of all objects also seems to suggest that the Universe is a black hole.” Huh, cool.
Here’s a fun thought experiment: can you destroy a black hole? Nuclear weapons probably won’t work but what about antimatter? Or anti black holes? In this video, Kurzgesagt explores the possibilities and impossibilities. This part baked my noodle (in a good way):
Contrary to widespread belief, the singularity of a black hole is not really “at its center”. It’s in the future of whatever crosses the horizon. Black holes warp the universe so drastically that, at the event horizon, space and time switch their roles. Once you cross it, falling towards the center means going towards the future. That’s why you cannot escape: Stopping your fall and turning back would be just as impossible as stopping time and traveling to the past. So the singularity is actually in your future, not “in front of you”. And just like you can’t see your own future, you won’t see the singularity until you hit it.
I really enjoyed this piece by Tom Vanderbilt on how time is kept, coordinated, calculated, and forecast. It’s full of interested tidbits throughout, like:
Care to gawk at one of the world’s last surviving original radium standards, a glass ampoule filled with 20.28 milligrams of radium chloride prepared by Marie Curie in 1913? NIST has it in the basement, encased in a steel bathtub, buried under lead bricks.
And:
For GPS to work, it needs ultra-exact timing: accuracy within fifteen meters requires precision on the order of fifty nanoseconds. The 5G networks powering our mobile phones demand ever more precise levels of cell-tower synchronization or calls get dropped.
And:
And as Mumford could have predicted, nowhere has time become so fetishized as in the financial sector, with the emergence over the past decade of algorithmic high-frequency trading. Donald MacKenzie, the author of Trading at the Speed of Light, estimated in 2019 that a trading program could receive market data and trigger an order in eighty-four nanoseconds, or eighty-four billionths of a second.
And:
All this makes F1 staggeringly accurate: it will gain or shed only one second every 100,000,000 years. Since the days when time was defined astronomically, the accuracy of the second is estimated to have increased by a magnitude of eight.
And:
“A clock accurate to a second over the age of the cosmos,” Patrick Gill, a physicist at the U.K.’s National Physical Laboratory, is quoted as saying in New Scientist, “would allow tests of whether physical laws and constants have varied over the universe’s history.”
And:
“If you were to lift this clock up a centimeter of elevation,” Hume told me, “you would be able to discern a difference in the ticking rate.” The reason is Einstein’s theory of relativity: Time differs depending on where you are experiencing it.
And I could go on and on. If any or all of those tidbits is interesting to you, you should go ahead and read the whole thing.
My ideal version of this film would have begun in the 1900s or ’10s, with flashes of Relativity and then the steps of Quantum Mechanics with Planck, Bohr, and Heisenberg. Quantum tunneling with Gamow and Gurney. The nuclear shell model with Maria Goeppert Mayer and J. Hans D. Jensen. Chadwick’s discovery of the neutron. Anderson’s positron unveiling. Hold the camera longer on Lawrence and his cyclotron. What’s going on there? (I mean, ya got Josh Hartnett’s pretty head, plaster it up!) Shoot in high-grade mega-IMAX-bokeh the oddly simple experimental setups, the beakers, the blips, the radiation tick-tick-ticks, the iterations, the step-by-step expansion of understanding the fabric of everything around us. Give us an hour of this, this arguably greatest moment of human insight. You can still call the film Oppenheimer. Let the man loom, weave him between it all as he makes his way through Europe, sets up at Berkeley, is selected to lead Los Alamos. Ramp up the Nazi threat. Show the diaspora of brilliance more clearly. Believe the audience is willing to sit through more than just “Is it a wave … or is it particle?” Oh! There is so much excitement, so much incredible science to be mined, and Nolan mined so little.
Mod and I both share a love for that masterpiece of a book and I would watch the hell out of an 10-part HBO series (in the vein of Chernobyl) based on it, American Prometheus, and John Hersey’s Hiroshima.
This short animation from NASA shows the sizes of some of the supermassive black holes that feature at the center of galaxies. Some are relatively small:
First up is 1601+3113, a dwarf galaxy hosting a black hole packed with the mass of 100,000 Suns. The matter is so compressed that even the black hole’s shadow is smaller than our Sun.
While others are much larger than the solar system…and this isn’t even the biggest one:
At the animation’s larger scale lies M87’s black hole, now with a updated mass of 5.4 billion Suns. Its shadow is so big that even a beam of light — traveling at 670 million mph (1 billion kph) — would take about two and a half days to cross it.
I saw this video on the front page a YouTube a couple of weeks ago and ignored it. Like, of course water can solve a maze, next! But then it got the Kid Should See This seal of approval so I gave it a shot. It turns out: water can solve a maze…but specifics are super interesting in several respects. Steve Mould, who you may remember from the assassin’s teapot video not too long ago, built four mazes of different sizes and shapes, each of them useful for demonstrating a different wrinkle in how the water moves through a maze. Recommended viewing for all ages.
The assassin’s teapot is certainly an eye-catching name for pottery, but there’s also an interesting bit of physics going on here. The teapot in question has two separate chambers for holding liquid, and the flow out of the pot from each chamber can be controlled by covering or uncovering small holes located on the handle. So, as the legend goes, a would-be assassin could pour themselves a perfectly fine drink from one chamber and then pour a poisoned drink to their prey from the other chamber, just by discreetly covering and uncovering the proper holes with their fingers. As the video explains, the mechanism here has to do with surface tension and air pressure.
You can get your own assassin’s teapot right here.
In an article published in the journal Leonardo, the researchers draw upon a fresh look at one of da Vinci’s notebooks to show that the famed polymath had devised experiments to demonstrate that gravity is a form of acceleration — and that he further modeled the gravitational constant to around 97 percent accuracy.
Da Vinci, who lived from 1452 to 1519, was well ahead of the curve in exploring these concepts. It wasn’t until 1604 that Galileo Galilei would theorize that the distance covered by a falling object was proportional to the square of time elapsed and not until the late 17th century that Sir Isaac Newton would expand on that to develop a law of universal gravitation, describing how objects are attracted to one another. Da Vinci’s primary hurdle was being limited by the tools at his disposal. For example, he lacked a means of precisely measuring time as objects fell.
As the piece notes, Leonardo didn’t get things exactly right:
Da Vinci sought to mathematically describe that acceleration. It is here, according to the study’s authors, that he didn’t quite hit the mark. To explore da Vinci’s process, the team used computer modeling to run his water vase experiment. Doing so yielded da Vinci’s error.
“What we saw is that Leonardo wrestled with this, but he modeled it as the falling object’s distance was proportional to 2 to the t power [with t representing time] instead proportional to t squared,” Roh says. “It’s wrong, but we later found out that he used this sort of wrong equation in the correct way.” In his notes, da Vinci illustrated an object falling for up to four intervals of time-a period through which graphs of both types of equations line up closely.
But it’s still pretty impressive how far he did get. The piece also notes that this work was discovered because the codex was made available online to the general public, demonstrating the value of easy access of materials like this.
A group of astronomers say they have evidence that links supermassive black holes at galactic centers with dark energy, the mysterious force that accounts for roughly 68% of the energy in the universe. Here’s the news release and the paper. From the Guardian:
Instead of dark energy being smeared out across spacetime, as many physicists have assumed, the scientists suggest that it is created and remains inside black holes, which form in the crushing forces of collapsing stars.
“We propose that black holes are the source for dark energy,” said Duncan Farrah, an astronomer at the University of Hawaii. “This dark energy is produced when normal matter is compressed during the death and collapse of large stars.”
The claim was met with raised eyebrows from some independent experts, with one noting that while the idea deserved scrutiny, it was far too early to link black holes and dark energy. “There’s a number of counter-arguments and facts that need to be understood if this claim is going to live more than a few months,” said Vitor Cardoso, a professor of physics at the Niels Bohr Institute in Copenhagen.
And here’s a short video explainer:
It’s a radical claim to be sure — it’ll be interesting to see how it shakes out in the weeks and months to come as other scientists interpret the results.
From Wikipedia contributor Cmglee and Astronomy Picture of the Day, a color-coded periodic table that displays which cosmic events — the Big Bang, exploding stars, merging neutron stars, etc. — was responsible for creating each element, according to our present understanding of the universe.
The hydrogen in your body, present in every molecule of water, came from the Big Bang. There are no other appreciable sources of hydrogen in the universe. The carbon in your body was made by nuclear fusion in the interior of stars, as was the oxygen. Much of the iron in your body was made during supernovas of stars that occurred long ago and far away. The gold in your jewelry was likely made from neutron stars during collisions that may have been visible as short-duration gamma-ray bursts or gravitational wave events.
The nitrogen in our DNA, the calcium in our teeth, the iron in our blood, the carbon in our apple pies were made in the interiors of collapsing stars. We are made of starstuff.
It is Friday and this is the perfect Friday sort of post. BeamNG is a video game of sorts that’s “a dynamic soft-body physics vehicle simulator capable of doing just about anything”. In the simulator, you can quickly devise all sorts of situations with a variety of cars and then press play to see what happens, with (mostly) realistic physics and collisions. For instance, here’s Cars vs Big Bulge:
Chained Cars vs Bollards:
Cars vs 100 Fallen Trees:
Trains vs Giant Pit:
And many many more. My god if this simulator had been around when I was 12 years old, I might not have done anything else. Hell, if I downloaded and installed this right now, I might not ever get anything done ever again. (via @tvaziri)
No doubt motivated by this month’s release of Moonfall, the latest movie from disaster shlockmeister Roland Emmerich, Kurzgesagt has made a video that shows what would happen to civilization should the Moon somehow get knocked from its orbit and head straight for the Earth. Spoiler: the Moon doesn’t even need to reach us to kill almost all life on the planet.
The James Webb Space Telescope is designed to be positioned near one of the five Lagrange Points in the Sun/Earth system, special areas of gravitational equilibrium that keep objects stationary relative to both the Earth and the Sun. Here’s how Lagrange Points work and why they are so useful for spacecraft like the Webb.
The James Webb Space Telescope is still winging its way to its permanent home at the L2 point1 about 930,000 miles from Earth — it’s due to arrive in about 4 days. It’s a massive and fascinating project and for his YouTube series Smarter Every Day, Destin Sandlin talked to Nobel laureate John Mather, the senior project scientist for the JWST, about how the telescope works.
Also worth a watch is Real Engineering’s The Insane Engineering of James Webb Telescope:
It really is a marvel of modern science & engineering — I can’t wait to see what the telescope sees once it’s fully operational.
You can read about Lagrange points here or here…they are interesting!↩
In this clever simulation, bouncing balls obeying the laws of physics somehow arrange themselves, mid-chaos, into neat patterns. This is immensely satisfying.
Spoiler: the trick here is a pair of simulations stitched together, like a physics Texas Switch: “Each sequence is obtained by joining two simulations, both starting from the time in which the balls are arranged regularly. One simulates forward in time, one backwards.”
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