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kottke.org posts about physics

“If It Doesn’t Shine In Your Face, You Don’t See Anything”

posted by Jason Kottke   Jul 28, 2021

Jocelyn Bell Burnell as a graduate student

As I’ve written before, in the history of astronomy and astrophysics, women have made major discoveries and played a significant role in advancing our understanding of the universe but have often not gotten the recognition their male peers enjoy. In 1967, while she was working on her doctoral research with her advisor Antony Hewish, Jocelyn Bell Burnell (then Jocelyn Bell) discovered a new and unusual kind of object, the pulsar. In this short documentary, Bell Burnell shares her story — how she got interested in radio astronomy, the prejudice with which she was treated as the only woman in her university program, how she discovered the first pulsar and persisted (more than once) through Hewish’s assertions that the object was “interference”, and how she was passed over for the Nobel Prize for her discovery.

In 2018, Bell Burnell was awarded the Special Breakthrough Prize in Fundamental Physics “for fundamental contributions to the discovery of pulsars, and a lifetime of inspiring leadership in the scientific community”, joining past honorees like the LIGO team, Stephen Hawking, and the team that discovered the Higgs boson. She donated the entire $3 million prize to the Institute of Physics to help support “PhD physics students from under-represented groups” with their educations.

It’s not justice, but I will note that Bell Burnell’s Wikipedia page is longer and more substantial than Hewish’s, despite his Nobel.

Visualization of How Fast a Ball Drops on Various Solar System Bodies

posted by Jason Kottke   Jul 14, 2021

This is an animation of how quickly an object falls 1 km to the surfaces of solar system objects like the Earth, Sun, Ceres, Jupiter, the Moon, and Pluto. For instance, it takes 14.3 seconds to cover that distance on Earth and 13.8 seconds on Saturn.

It might be surprising to see large planets have a pull comparable to smaller ones at the surface, for example Uranus pulls the ball down slower than at Earth! Why? Because the low average density of Uranus puts the surface far away from the majority of the mass. Similarly, Mars is nearly twice the mass of Mercury, but you can see the surface gravity is actually the same… this indicates that Mercury is much denser than Mars.

(via @thekidshouldsee)

UFOs Are Not Aliens

posted by Jason Kottke   Jun 01, 2021

Due to recent government reports, declassified data, media interest in those data & reports, and a long-simmering interest by the public, UFOs are back in the public imagination. Adam Frank, an astrophysicist at the University of Rochester who is searching for signs of extraterrestrial life, says that there’s little chance that UFOs are aliens.

I understand that U.F.O. sightings, which date back at least to 1947, are synonymous in the popular imagination with evidence of extraterrestrials. But scientifically speaking, there is little to warrant that connection. There are excellent reasons to search for extraterrestrial life, but there are equally excellent reasons not to conclude that we have found evidence of it with U.F.O. sightings.

If UFOs are alien craft, we would never see them:

There are also common-sense objections. If we are being frequently visited by aliens, why don’t they just land on the White House lawn and announce themselves? There is a recurring narrative, perhaps best exemplified by the TV show “The X-Files,” that these creatures have some mysterious reason to remain hidden from us. But if the mission of these aliens calls for stealth, they seem surprisingly incompetent. You would think that creatures technologically capable of traversing the mind-boggling distances between the stars would also know how to turn off their high beams at night and to elude our primitive infrared cameras.

More people talking about a thing doesn’t make it credible. More people talking about potential evidence of a thing doesn’t make it credible. Evidence makes something credible.

Was the Microwave Invented to Thaw Out Frozen Hamsters?

posted by Jason Kottke   May 28, 2021

We all know that the microwave oven was invented by Raytheon’s Percy Spencer in 1945. What this video presupposes is, maybe it was invented to thaw out frozen hamsters? And somehow James Lovelock, who formulated the Gaia hypothesis, is involved? (via @fourfoldway)

Hisako Koyama, the Woman Who Stared at the Sun

posted by Jason Kottke   May 26, 2021

In the history of science, there are women who have made significant contributions to their field but haven’t gotten the recognition that their male peers have. The field of astronomy & astrophysics in particular has had many female pioneers — Vera Rubin, Cecilia Payne-Gaposchkin, Annie Jump Cannon, Nancy Grace Roman, Maria Mitchell, Jocelyn Bell Burnell, Henrietta Swan Leavitt, Caroline Herschel, Williamina Fleming, and many others. Add to that list Hisako Koyama, a Japanese astronomer whose detailed sketches of the Sun over a 40-year period laid the foundation for a 400-year timeline of sunspot activity, which has aided researchers in studying solar cycles and magnetic fields.

Ms. Koyama was a most unusual woman of her time. As a scientist, she bridged the amateur and professional world. She preferred “doing” activities: observing, data recording, interacting with the public, and writing. No doubt many Japanese citizens benefited from personal interaction with her. The space and geophysics community continues to benefit from her regular and precise observations of the Sun. Although we know very little of her young personal life other than she was relatively well educated and had a father who supported her desire to view the skies by providing a telescope, we can see from snippets in Japanese amateur astronomy articles that she had a passion for observing, as revealed in her 1981 article: “I simply can’t stop observing when thinking that one can never know when the nature will show us something unusual.”

Here are a few of her sunspot sketches, the top two done using her home telescope and the bottom one using the much larger telescope at the National Museum of Nature and Science (that shows the largest sunspot of the 20th century):

drawings of sunspots on the Sun by Hisako Koyama

drawings of sunspots on the Sun by Hisako Koyama

(via the kid should see this)

The Final Border Humanity Will Never Cross

posted by Jason Kottke   May 11, 2021

This video focuses on one of my favorite astrophysics facts: 94% of the observable universe is permanently unreachable by humans. (Unless we discover faster-than-light travel, but that’s fantasy at this point.)

This expansion means that there is a cosmological horizon around us. Everything beyond it, is traveling faster, relative to us, than the speed of light. So everything that passes the horizon, is irretrievably out of reach forever and we will never be able to interact with it again. In a sense it’s like a black hole’s event horizon, but all around us. 94% of the galaxies we can see today have already passed it and are lost to us forever.

“Since you started watching this video, around 22 million stars have moved out of our reach forever.” And future generations, billions of years from now, won’t even be able to see any other galaxies or detect cosmic background radiation, making knowledge about the Big Bang impossible.

The Otherworldly Sounds of Ice

posted by Jason Kottke   May 05, 2021

The holes drilled into Arctic, Antarctic, and glacial ice to harvest ice cores can be up to 2 miles deep. One of my all-time favorite sounds is created by dropping ice down into one of these holes — it makes a super-cool pinging noise, as demonstrated in these two videos:

Ice makes similar sounds under other conditions, like if you skip rocks on a frozen lake:

Or skate on really thin ice (ok this might actually be my favorite sound, with apologies to the ice core holes):

Headphones are recommended for all of these videos. The explanation for this distinctive pinging sound, which sounds like a Star Wars blaster, has to do with how fast different sound frequencies move through the ice, as explained in this video:

(via the kid should see this)

An Animated Primer on Black Holes

posted by Jason Kottke   Apr 28, 2021

You’re probably aware that black holes are weird. You can learn more about just how extremely odd they are by watching this animated primer on black holes by Kurzgesagt. The explanation about how long black holes live starting at ~9:30 is legitimately mindblowing — that hourglass metaphor especially.

Wobbling Muons May Hint at Unknown Forces

posted by Jason Kottke   Apr 08, 2021

Muon Ring

The preliminary results of a study of elementary particles at Fermilab and elsewhere show that the behavior of particles called muons deviates from standard physical theories, indicating that previously unknown forces are at work.

Evidence is mounting that a tiny subatomic particle seems to be disobeying the known laws of physics, scientists announced on Wednesday, a finding that would open a vast and tantalizing hole in our understanding of the universe.

The result, physicists say, suggests that there are forms of matter and energy vital to the nature and evolution of the cosmos that are not yet known to science.

“This is our Mars rover landing moment,” said Chris Polly, a physicist at the Fermi National Accelerator Laboratory, or Fermilab, in Batavia, Ill., who has been working toward this finding for most of his career.

The particle célèbre is the muon, which is akin to an electron but far heavier, and is an integral element of the cosmos. Dr. Polly and his colleagues — an international team of 200 physicists from seven countries — found that muons did not behave as predicted when shot through an intense magnetic field at Fermilab.

The aberrant behavior poses a firm challenge to the Standard Model, the suite of equations that enumerates the fundamental particles in the universe (17, at last count) and how they interact.

“This is strong evidence that the muon is sensitive to something that is not in our best theory,” said Renee Fatemi, a physicist at the University of Kentucky.

Update: At Quanta Magazine, Natalie Wolchover dives deeper into the preliminary results and what they might mean.

The Secret of Synchronization

posted by Jason Kottke   Apr 02, 2021

What do swaying bridges, flashing fireflies, clapping audiences, the far side of the Moon, and beating hearts have in common? Their behavior all has something to do with synchronization. In this video, Veritasium explains why and how spontaneous synchronization appears all the time in the physical world.

I was really into the instability of the Millennium Bridge back when it was first opened (and then rapidly closed), so it was great to hear Steven Strogatz’s explanation of the bridge’s failure.

Oh, and do go play with Nicky Case’s firefly visualization to see how synchronization can arise from really simple rules.

What Would We Experience If Earth Spontaneously Turned Into A Black Hole?

posted by Jason Kottke   Nov 05, 2020

Let’s say the Earth turned into a black hole. What would happen to someone standing on the surface and for how long would it happen? From Ethan Siegel:

As spectacular as falling into a black hole would actually be, if Earth spontaneously became one, you’d never get to experience it for yourself. You’d get to live for about another 21 minutes in an incredibly odd state: free-falling, while the air around you free-fell at exactly the same rate. As time went on, you’d feel the atmosphere thicken and the air pressure increase as everything around the world accelerated towards the center, while objects that weren’t attached to the ground would appear approach you from all directions.

Universe Sandbox

posted by Jason Kottke   Feb 14, 2020

Universe Sandbox is a interactive space & gravity simulator that you can use to play God of your own universe.

You can create star systems: “Start with a star then add planets. Spruce it up with moons, rings, comets, or even a black hole.” You can collide planets and stars or simulate gravity: “N-body simulation at almost any speed using Newtonian mechanics.” You can model the Earth’s climate, make a star go supernova, or ride along on space missions or see historical events.

I found Universe Sandbox after watching this video about what would happen if the Earth got hit by a grain of sand going 99.9% the speed of light (spoiler: not much). This game/simulator/educational tool is only $30 but I fear that if I bought it, I would never ever leave the house again.

New Solar Telescope Shows the Sun’s Surface in Unprecendented High Resolution Images & Video

posted by Jason Kottke   Jan 29, 2020

Sun's Surface

Sun's Surface

The National Science Foundation has just released the very first images of the Sun taken with the new Inouye Solar Telescope in Hawaii. They are the highest resolution images ever taken of the Sun’s surface, showing three times more detail than was possible using previous imaging techniques. Those cells you see in the image…they’re each about the size of Texas.

Building a telescope like this is not an easy task — there’s a lot of heat to deal with:

To achieve the proposed science, this telescope required important new approaches to its construction and engineering. Built by NSF’s National Solar Observatory and managed by AURA, the Inouye Solar Telescope combines a 13-foot (4-meter) mirror — the world’s largest for a solar telescope — with unparalleled viewing conditions at the 10,000-foot Haleakala summit.

Focusing 13 kilowatts of solar power generates enormous amounts of heat — heat that must be contained or removed. A specialized cooling system provides crucial heat protection for the telescope and its optics. More than seven miles of piping distribute coolant throughout the observatory, partially chilled by ice created on site during the night.

Scientists have released a pair of mesmerizing time lapse videos as well, showing ten minutes of the roiling surface of the Sun (wide angle followed by a close-up view) in just a few seconds:

The Daniel K. Inouye Solar Telescope has produced the highest resolution observations of the Sun’s surface ever taken. In this movie, taken at a wavelength of 705nm over a period of 10 minutes, we can see features as small as 30km (18 miles) in size for the first time ever. The movie shows the turbulent, “boiling” gas that covers the entire sun. The cell-like structures — each about the size of Texas — are the signature of violent motions that transport heat from the inside of the sun to its surface. Hot solar material (plasma) rises in the bright centers of “cells,” cools off and then sinks below the surface in dark lanes in a process known as convection. In these dark lanes we can also see the tiny, bright markers of magnetic fields. Never before seen to this clarity, these bright specks are thought to channel energy up into the outer layers of the solar atmosphere called the corona. These bright spots may be at the core of why the solar corona is more than a million degrees!

Man, I hope we get some longer versions of these time lapses — I would watch the hell out of one that ran for 10 minutes. (via moss & fog)

An Astronomer Explains Black Holes in 5 Levels of Increasing Complexity

posted by Jason Kottke   Jan 21, 2020

In this video from Wired’s 5 Levels series, NASA astronomer Varoujan Gorjian explains the concept of black holes to five different people, ranging from a five-year-old to a college student to a Caltech astrophysicist.

A research astronomer at NASA’s Jet Propulsion Laboratory, Grojian specializes in — and I’d just like to pause here to emphasize that this is the official title of his research group at JPL — the structure of the universe. Which means the guy not only knows about event horizons and gravitational lensing but stuff like tidal forces (what!), x-ray binaries (hey now!), and active galactic nuclei (oh my god!). Seriously, the guy’s knowledge of black holes is encyclopedic.

Gorjian lost me somewhere in the middle of his conversation with the grad student.

How Do You Move a Star? Stellar Engines!

posted by Jason Kottke   Dec 30, 2019

In this episode of Kurzgesagt, they’re talking about building engines powerful enough to move entire stars, dragging their solar systems along with them.

At some point we could encounter a star going supernova. Or a massive object passing by and showering earth with asteroids.

If something like this were to happen we would likely know thousands, if not millions of years in advance. But we still couldn’t do much about it.

Unless… we move our whole solar system out of the way.

Kurzgesagt did something interesting for this one. Instead of relying on already available sources, they commissioned physicist Matthew Caplan to write a paper about a novel stellar engine design, a massive contraption that could theoretically move the solar system a distance of 50 light years over 1 million years.

Stellar engines, megastructures used to control the motion of a star system, may be constructible by technologically advanced civilizations and used to avoid dangerous astrophysical events or transport a star system into proximity with another for colonization.

Is this the first scientific paper published in a peer-reviewed journal commissioned by a YouTube channel? The 2019 media landscape is wild.

Cecilia Payne-Gaposchkin, a Giant of Physics

posted by Jason Kottke   Dec 17, 2019

Prompted by this Facebook post, I have been reading about astrophysicist Cecilia Payne-Gaposchkin, who should be more widely known than she is. From a piece last year in Cosmos:

Cecilia Payne, born on May 10, 1900, in Wendover, England, began her scientific career in 1919 with a scholarship to Cambridge University, where she studied physics. But in 1923 she received a fellowship to move to the United States and study astronomy at Harvard. Her 1925 thesis, Stellar Atmospheres, was described at the time by renowned Russian-American astronomer Otto Struve as “the most brilliant PhD thesis ever written in astronomy”.

In the January, 2015, Richard Williams of the American Physical Society, wrote: “By calculating the abundance of chemical elements from stellar spectra, her work began a revolution in astrophysics.”

Even though she completed her studies at Cambridge, she was not awarded a degree because the university did not give degrees to women. That’s when she decided to move to the US, where Harvard offered greater educational opportunities and a “collection of several hundred thousand glass photographs of the night sky” that Payne-Gaposchkin was uniquely qualified to analyze.

Miss Payne applied the new theories of atomic structure and quantum physics to her analysis of stellar spectra. No one at the Harvard Observatory had yet attempted such an investigation, as no one there possessed the necessary background. She, in contrast, had learned the complex architecture of the “Bohr atom” directly from Niels Bohr, winner of the 1922 Nobel Prize in physics. She had also followed the work of Indian physicist Meg Nad Saha of Calcutta, the first person to link the atom to the stars. Saha maintained that the line patterns in stellar spectra differed according to the temperatures of the stars. The hotter the star, the more readily the electrons of its atoms leaped to higher orbits. With sufficient heat, the outermost electrons broke free, leaving behind positively charged ions with altered spectral signatures.

Building on Saha’s base, with insights gained from a couple of her professors in England, Miss Payne selected specific spectral lines to examine. Then she estimated their intensities in hundreds of stellar spectra. Element by element she gauged, plotted, and calculated her way through the plates to take the temperatures of the stars.

Her groundbreaking work on spectra, laid out in her Ph.D thesis published when she was just 25, puts Payne-Gaposchkin in the same league as some other physics heavy hitters.

Her discovery of the true cosmic abundance of the elements profoundly changed what we know about the universe. The giants — Copernicus, Newton, and Einstein — each in his turn, brought a new view of the universe. Payne’s discovery of the cosmic abundance of the elements did no less.

Incredible Display of Ice Crystal Halos Around the Sun in the Swiss Alps

posted by Jason Kottke   Dec 05, 2019

Ice Halos

This is a photo of several ice crystal halos around the Sun taken by Michael Schneider in the Swiss Alps with an iPhone 11 Pro. It. Is. Absolutely. Stunning. I can barely write more than a few words here without stealing another peek at it. According to Schneider’s post (translated from German by Google), this display developed gradually as he waited for a friend as some icy fog and/or clouds were dissipating at the top of a Swiss ski resort and he was happy to capture it on his new phone.

Using this site on atmospheric optics, Mark McCaughrean helpfully annotated Schneider’s photo to identify all of the various halos on display:

Ice Halos 02

Displays like this are pretty rare, but Joshua Thomas captured a similar scene in New Mexico a few years ago and Gizmodo’s Mika McKinnon explained what was going on.

Ice halos happen when tiny crystals of ice are suspended in the sky. The crystals can be high up in cirrus clouds, or closer to the ground as diamond dust or ice fog. Like raindrops scatter light into rainbows, the crystals of ice can reflect and refract light, acting as mirrors or prisms depending on the shape of the crystal and the incident angle of the light. While the lower down ice only happens in cold climates, circus clouds are so high they’re freezing cold any time, anywhere in the world, so even people in the tropics mid-summer have a chance of seeing some of these phenomena.

Explaining the optics of these phenomena involves a lot of discussing angular distances.

So so so so cool.

Neutron Stars and Nuclear Pasta. Yummy!

posted by Jason Kottke   Nov 13, 2019

The latest video from Kurzgesagt is a short primer on neutron stars, the densest large objects in the universe.

The mind-boggling density of neutron stars is their most well-known attribute: the mass of all living humans would fit into a volume the size of a sugar cube at the same density. But I learned about a couple of new things that I’d like to highlight. The first is nuclear pasta, which might be the strongest material in the universe.

Astrophysicists have theorized that as a neutron star settles into its new configuration, densely packed neutrons are pushed and pulled in different ways, resulting in formation of various shapes below the surface. Many of the theorized shapes take on the names of pasta, because of the similarities. Some have been named gnocchi, for example, others spaghetti or lasagna.

Simulations have demonstrated that nuclear pasta might be some 10 billion times stronger than steel.

The second thing deals with neutron star mergers. When two neutron stars merge, they explode in a shower of matter that’s flung across space. Recent research suggests that many of the heavy elements present in the universe could be formed in these mergers.

But how elements heavier than iron, such as gold and uranium, were created has long been uncertain. Previous research suggested a key clue: For atoms to grow to massive sizes, they needed to quickly absorb neutrons. Such rapid neutron capture, known as the “r-process” for short, only happens in nature in extreme environments where atoms are bombarded by large numbers of neutrons.

If this pans out, it means that the Earth’s platinum, uranium, lead, and tin may have originated in exploding neutron stars. Neat!

Google Announces They Have Achieved “Quantum Supremacy”

posted by Jason Kottke   Oct 23, 2019

Today, Google announced the results of their quantum supremacy experiment in a blog post and Nature article. First, a quick note on what quantum supremacy is: the idea that a quantum computer can quickly solve problems that classical computers either cannot solve or would take decades or centuries to solve. Google claims they have achieved this supremacy using a 54-qubit quantum computer:

Our machine performed the target computation in 200 seconds, and from measurements in our experiment we determined that it would take the world’s fastest supercomputer 10,000 years to produce a similar output.

You may find it helpful to watch Google’s 5-minute explanation of quantum computing and quantum supremacy (see also Nature’s explainer video):

IBM has pushed back on Google’s claim, arguing that their classical supercomputer can solve the same problem in far less than 10,000 years.

We argue that an ideal simulation of the same task can be performed on a classical system in 2.5 days and with far greater fidelity. This is in fact a conservative, worst-case estimate, and we expect that with additional refinements the classical cost of the simulation can be further reduced.

Because the original meaning of the term “quantum supremacy,” as proposed by John Preskill in 2012, was to describe the point where quantum computers can do things that classical computers can’t, this threshold has not been met.

One of the fears of quantum supremacy being achieved is that quantum computing could be used to easily crack the encryption currently used anywhere you use a password or to keep communications private, although it seems like we still have some time before this happens.

“The problem their machine solves with astounding speed has been very carefully chosen just for the purpose of demonstrating the quantum computer’s superiority,” Preskill says. It’s unclear how long it will take quantum computers to become commercially useful; breaking encryption — a theorized use for the technology — remains a distant hope. “That’s still many years out,” says Jonathan Dowling, a professor at Louisiana State University.

Strange Stars and Strange Matter

posted by Jason Kottke   Apr 17, 2019

Nuclear physicists hypothesize that when the cores of neutron stars are subject to enough pressure, the quarks that make up the core can turn from up and down quark varieties into strange quarks. As this Kurzgesagt video explains, this strange matter is particularly stable and if it were to escape from the core of the neutron star, it would convert any ordinary matter it came into contact with to more strange matter. If you hadn’t heard about this hypothesis before, you can read up on it in their list of sources for the video.

The first photo of a black hole

posted by Chrysanthe Tenentes   Apr 10, 2019

The first photo of a black hole

Ok, this is pretty cool. We have the first photo of a supermassive black hole, from imagery taken two years ago of the elliptical galaxy M87 (in the constellation Virgo) by the Event Horizon Telescope project. The EHT team is a group of 200 scientist that has been working on this project for two decades. The image was created using data captured from radio telescopes from Hawaii to the South Pole and beyond using very long baseline interferometry.

The image, of a lopsided ring of light surrounding a dark circle deep in the heart of the galaxy known as Messier 87, some 55 million light-years away from here, resembled the Eye of Sauron, a reminder yet again of the power and malevolence of nature. It is a smoke ring framing a one-way portal to eternity.

Now is a good time to (re)read Jonathan Lethem’s early novel, the absurdist physics love story As She Climbed Across the Table.

Update: Vox’s Joss Fong has a good 6-minute video that explains how the photo was taken:

And this video by Veritasium is even more meaty (and this one too):

A Timelapse of the Entire Universe

posted by Jason Kottke   Apr 01, 2019

John Boswell has made a 10-minute time lapse video showing the history of the universe, from its formation 13.8 billion years ago up to the present. Each second of the video represents the passing of 22 million years. But don’t blink right near the end…you might miss the tiny fraction of a second that represents the entire history of humanity.

See also: Boswell’s Timelapse of the Future, a dramatized time lapse of possible events from now until the heat death of the universe many trillion trillion trillions of years from now.

Timelapse of the Future

posted by Jason Kottke   Mar 27, 2019

One of my favorite Wikipedia articles is the timeline of the far future, which details the predictions science makes about the possible futures of the Earth, solar system, galaxy, and universe, from Antares exploding in a supernova visible from Earth in broad daylight in 10,000 years to the end of star formation in galaxies 1 trillion years from now…and beyond.

In his new video, Timelapse of the Future, John Boswell takes us on a trip through that timeline, a journey to the end of time.

We start in 2019 and travel exponentially through time, witnessing the future of Earth, the death of the sun, the end of all stars, proton decay, zombie galaxies, possible future civilizations, exploding black holes, the effects of dark energy, alternate universes, the final fate of the cosmos — to name a few.

A regular time lapse of that voyage would take forever, so Boswell cleverly doubles the pace every 5 seconds, so that just after 4 minutes into the video, a trillion years passes in just a second or two.1 You’d think that after the Earth is devoured by the Sun about 3 minutes in, things would get a bit boring and you could stop watching, but then you’d miss zombie white dwarfs roaming the universe in the degenerate era, the black hole mergers era 1000 trillion trillion trillion trillion years from now, the possible creation of baby “life boat” universes, and the point at which “nothing happens and it keeps not happening forever”.

  1. This is similar to Charles and Ray Eames’ Powers of Ten increasing its speed and field of view every 10 seconds.

Actually, Mercury Is Our Closest Planetary Neighbor

posted by Jason Kottke   Mar 21, 2019

If you look at the orbits of the planets adjacent to the Earth’s orbit (Venus & Mars), you’ll see that Venus’s orbit is closest to our own. That is, at its closest approach, Venus gets closer to Earth than any other planet. But what about the average distance?

According to this article in Physics Today by Tom Stockman, Gabriel Monroe, and Samuel Cordner, if you run a simulation and do a proper calculation, you’ll find that Mercury, and not Venus or Mars, is Earth’s closest neighbor on average (and spends more time as Earth’s closest neighbor than any other planet):

Although it feels intuitive that the average distance between every point on two concentric ellipses would be the difference in their radii, in reality that difference determines only the average distance of the ellipses’ closest points. Indeed, when Earth and Venus are at their closest approach, their separation is roughly 0.28 AU — no other planet gets nearer to Earth. But just as often, the two planets are at their most distant, when Venus is on the side of the Sun opposite Earth, 1.72 AU away. We can improve the flawed calculation by averaging the distances of closest and farthest approach (resulting in an average distance of 1 AU between Earth and Venus), but finding the true solution requires a bit more effort.

What the calculation also shows is that Mercury is the closest planetary neighbor to every planet, on average. Also, the authors of the paper don’t explicitly mention this, but the Sun (at 1 AU) is closer on average to the Earth than even Mercury (1.04 AU).

What Time Is the Super Bowl? (According to a Theoretical Physicist)

posted by Jason Kottke   Jan 31, 2019

Ever since the Huffington Post struck SEO gold in 2011 with their post about what time the Super Bowl started, pretty much every online publication now runs a similar article in an attempt to squeeze some of Google’s juice into their revenue stream. My “attempt” from last year: What Time Isn’t the Super Bowl?

For this year’s contest, Sports Illustrated decided to ask theoretical physicist Carlo Rovelli, author of The Order of Time, his thoughts on time and Super Bowls.

6:30 p.m. is the time the Super Bowl will start in Atlanta. Most of us are not in Atlanta. So for us, the game will start later than that. You need the time for the images to be captured by the cameras, be broadcasted to air or cable, be captured by my TV screen, leave my TV screen, get to my eyes (not to mention the time my brain needs to process and decode the images). You may say this is fast — of course this is fast. But it takes some time nevertheless, and I am a physicist, I need precision. For most of us, the game will actually start some time later than the kickoff in Atlanta.

Not only that, but time moves at different speeds for each of us:

We have discovered that clocks run at different speed depending on how fast they are moved, and depending on how high they are positioned. That’s right, it is a fact: Two equal clocks go out of time with respect each other if one is moved and the other is kept fixed. The same will happen if one is kept, say, above your head, and the other lower, say, at your feet. All this was discovered by Einstein a century ago; for a while it was just brainy stuff for nerds, but today we are sure it is true. A good lab clock can check this, and it is truly true. Your head lives a bit longer than your feet (unless you spend a lot of time upside down).

So, the clock of the guy up in the high sections of the stadium runs faster than the clock of the referee on the field. And Tom Brady’s clock (if he were to wear one) runs slower, because Tom moves fast (okay, maybe not “fast,” but faster than the people sitting and watching him).

P.S. The Super Bowl starts at approximately 6:30pm EST on Feb 3, 2019. (via laura olin)

In a Race to the Edge of the Solar System, Which Star Trek Ship Would Win?

posted by Jason Kottke   Jan 29, 2019

These visualizations of the speed of light I posted last week somehow demonstrate both how fast light speed is and how slow it is compared the vastness of the galaxy & universe. Science fiction often bends the rules of physics as we currently understand them, with fictional spacecraft pushing beyond the speed of light. In Star Trek, the measure of a ship’s velocity is warp speed. Warp 1 is the speed of light, Warp 6 is 392 times the speed of light, etc. In this Warp Speed Comparison video, EC Henry compares the top speeds of various Star Trek vessels (the original Enterprise, Voyager, the Defiant), racing them from Earth to the edge of the solar system.

Once again, you get a real sense of how fast these ships would be if they actually existed but also of the vastness of space. It would take 10 seconds for the fastest ship to reach the edge of the solar system at maximum warp and just over 6 hours to get to the nearest star, Proxima Centauri. Wikipedia lists a few dozen stars that are within a day’s journey at full warp…a trip that takes light more than 16 years. The mighty speed of light is no match for the human imagination. (thx, jim)

Visualizing the Speed of Light

posted by Jason Kottke   Jan 24, 2019

Light is fast! In a recent series of animations, planetary scientist James O’Donoghue demonstrates just how fast light is…and also how far away even our closest celestial neighbors are. Light, moving at 186,000 mi/sec, can circle the Earth 7.5 times per second and here’s what that looks like:

It can also travel from the surface of the Earth to the surface of the Moon in ~1.3 seconds, like so:

That seems both really fast and not that fast somehow. Now check out light traveling the 34 million miles to Mars in a pokey 3 minutes:

And Mars is close! If O’Donoghue made a real-time animation of light traveling to Pluto, the video would last over 5 hours. The animation for the closest undisputed galaxy, Seque 1, would last 75,000 years and 2.5 million years for the Andromeda galaxy animation. The farthest-known objects from Earth are more than 13 billion light years away. Light is slow!

See also The Leisurely Pace of Light Speed.

Universe, a Short Documentary from 1960 that Inspired Kubrick’s 2001

posted by Jason Kottke   Jan 23, 2019

In 1960, the National Film Board of Canada released a short documentary called Universe. The film follows the work of astronomer Donald MacRae at an observatory in Ontario, which is accompanied a special effects-heavy tour of the solar system, galaxy, and universe: “a vast, awe-inspiring picture of the universe as it would appear to a voyager through space”. Universe was nominated for an Oscar in 1961 and also caught the eye of Stanley Kubrick, who used it as inspiration for 2001: A Space Odyssey.

“Stanley had seen the National Film Board movie Universe.” Most of the crew on 2001 were familiar with the Canadian production, made by filmmakers Colin Low and Roman Kroitor, all having seen it at the early stages of 2001’s production, it being “required watching” at the insistence of Kubrick himself, who had seen the documentary “almost 100 times”, “until the sprockets wore out,” 2001 special effects supervisor Con Pedersen remembers.

Kubrick was so taken by the depiction of the celestial objects in the film that he hired the co-director and a special effects technician from Universe to work on 2001. The narrator of Universe, Douglas Rain, also became a integral part of Kubrick’s masterpiece. After ditching the idea that 2001 would be narrated by Rain — “as more film cut together, it became apparent narration was not needed” — Kubrick chose Rain as the now-iconic voice of HAL 9000.

After finally excising the narrator altogether, he simply made Rain the voice of HAL, liking his “bland mid-Atlantic accent”. The decision was entirely Kubrick’s, who had become concerned with the character of the computer. “Kubrick was having,” Rain says, “a problem with the computer. ‘I think I made him too emotional and too human,’ he said. ‘I’m having trouble with what I’ve got in the can. Would you consider doing his voice?’ So we decided on the voice of the computer.”

But back to Universe, which is a marvelous little film (even though it asserts at one point that “it is reasonably certain” that Mars contains vegetation). I love the early sequence of the astronomer setting up his telescope — the way he walks along inside of it and then casually lifts it up into place. It’s really just a bigger version of the small reflector that I have, not any more complicated than a couple of mirrors pointed in the right direction. It’s incredible what we humans have learned about the universe simply by collecting ancient starshine with polished lenses and mirrors. (via clayton cubitt)

Why Is the Night Sky Dark?

posted by Jason Kottke   Jan 17, 2019

I love how simple questions can reveal deep truths about how the universe works. Take “why is the night sky dark?” It’s a question a small child might ask but stumped the likes of Newton, Halley, and Kepler and wasn’t really resolved until Einstein’s theory of general relativity and the Big Bang theory rolled around. Here’s the paradox: if we live in a static infinite universe, shouldn’t the sky be unbearably bright?

Distant stars look weak, and very distant stars shine too dimly for you to see with your eyes. But when space telescopes like Hubble peer deep into the darkest spots of sky, they uncover bunches of incredibly faint galaxies. And the deeper they look, the more they find. If the universe went on forever with stars sprinkled evenly throughout — as many early stargazers assumed — the night sky would be full of so many points of light that it would never look dark.

“The fact that the stars are everywhere makes up for the fact that some of the stars are far away,” says Katie Mack, an astrophysicist at North Carolina State University. No matter which way you look, in an endless universe your line of sight would always end smack on the surface of a star, and the entire sky would always blaze with the brightness of the sun.

The answer to this paradox is that the universe is both finite & unbounded (per Einstein) and the darkness we see is the Big Bang.

The mystery of the dark sky is solved by the fact that this history has a beginning — a time before stars and galaxies. Many cosmologists think the universe started out as a very small point, and then started inflating like a balloon in an event called the Big Bang. If you look deep enough, you can see so far back in time that you get close to the Big Bang. “You just run out of stars,” Kinney says. “And you run out of stars, in the grand scheme of things, relatively quickly.”

If you’re anything like me, you just had a Little Bang go off in your brain. (via laura olin)

Our Unbounded Finite Universe

posted by Jason Kottke   Jan 08, 2019

I’ve always had a hard time wrapping my head around the idea that the universe could be both finite and infinite at the same time (or something like that *takes bong rip*), but this passage from Coming of Age in the Milky Way by Timothy Ferris succinctly explains what’s going on:

General relativity resolved the matter by establishing that the universe could be both finite — i.e., could contain a finite number of stars in a finite volume of space — and unbounded. The key to this realization lay in Einstein’s demonstration that, since matter warps space, the sum total of the mass in all the galaxies might be sufficient to wrap space around themselves. The result would be a closed, four-dimensionally spherical cosmos, in which any observer, anywhere in the universe, would see galaxies stretching deep into space in every direction, and would conclude, correctly, that there is no end to space. Yet the amount of space in a closed universe would nonetheless be finite: An adventurer with time to spare could eventually visit every galaxy, yet would never reach an edge of space. Just as the surface of the earth is finite but unbounded in two dimensions (we can wander wherever we like, and will not fall off the edge of the earth) so a closed four-dimensional universe is finite but unbounded to us who observe it in three dimensions.

In the terms of Edwin Abbott Abbott’s Flatland: A Romance of Many Dimensions, we are Flatlanders living in a Lineland world who, with the aid of mathematics, have been able to peer into Spaceland.