kottke.org posts about physics
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)
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.
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.
With the homemade telescope in his backyard observatory, amateur astronomer Gary Hug has discovered over 300 asteroids.
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.
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.
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.
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)
Kurzgesagt makes some of the most entertaining science explainers around. Check out their most recent video on black holes.
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 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.
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!
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!
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).
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.
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 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.
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.
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.
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)
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.
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.
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)
CERN’s LHC (Large Hadron Collider) has discovered a new subatomic particle, the pentaquark.
“The pentaquark is not just any new particle,” said LHCb spokesperson Guy Wilkinson. “It represents a way to aggregate quarks, namely the fundamental constituents of ordinary protons and neutrons, in a pattern that has never been observed before in over fifty years of experimental searches. Studying its properties may allow us to understand better how ordinary matter, the protons and neutrons from which we’re all made, is constituted.”
Here’s the paper, with more than 680 authors. Between New Horizons zipping past Pluto earlier today (look at this pic!) and this, what a day for science.
Unlike the Earth, Mars and the Moon don’t have strong directional magnetic fields, which means traditional compasses don’t work. So how did the Apollo rovers and current Mars rovers navigate their way around? By using manually set directional gyroscope and wheel odometers.
While current un-crewed rovers don’t have to return to the comfort of a lunar module, some aspects of the Apollo systems live on in their design. Four U.S. Martian rovers have used wheel odometers that account for slippage to calculate distance traveled. They’ve also employed gyroscopes (in the form of an inertial measurement units) to determine heading and pitch/roll information.
One of the fun things about reading The Martian is you get to learn a little bit about this sort of thing. Here’s a passage about navigation on Mars where astronaut Mark Watney is trying to get to a landmark several days’ drive away.
Navigation is tricky.
The Hab’s nav beacon only reaches 40 kilometers, so it’s useless to me out here. I knew that’d be an issue when I was planning this little road trip, so I came up with a brilliant plan that didn’t work.
The computer has detailed maps, so I figured I could navigate by landmarks. I was wrong. Turns out you can’t navigate by landmarks if you can’t find any god damned landmarks.
Our landing site is at the delta of a long-gone river . NASA chose it because if there are any microscopic fossils to be had, it’s a good place to look. Also, the water would have dragged rock and soil samples from thousands of kilometers away. With some digging, we could get a broad geological history.
That’s great for science, but it means the Hab’s in a featureless wasteland.
I considered making a compass. The rover has plenty of electricity, and the med kit has a needle. Only one problem: Mars doesn’t have a magnetic field.
So I navigate by Phobos. It whips around Mars so fast it actually rises and sets twice a day, running west to east. It isn’t the most accurate system, but it works.
I wonder why the rovers in the story weren’t outfitted with directional gyroscopes and wheel odometers? (See also the operations manual for the lunar rovers.) (via @JaredCrookston)
Here’s something that I knew as a kid but had forgotten about: if you get a bike going on its own at sufficient speed, it will essentially ride itself. MinutePhysics investigates why that happens.
Interesting that the bike seems to do much of the work of staying upright when it seems like the rider is the thing that makes it work. (via devour)
In 1983, the BBC aired a six-part series called Fun to Imagine with a simple premise: put physicist Richard Feynman in front of a camera and have him explain everyday things. In this clip from one of the episodes, Feynman explains in very simple terms what fire is:
So good. Watch the whole thing…it seems like you get the gist about 2 minutes in, but that’s only half the story. See also Feynman explaining rubber bands, how trains go around curves, and how magnets work.
This video, shot at 36,000 frames per second, shows a balloon popping underwater. I am not quite sure what I expected, but it wasn’t this.
For instance, the air bubbles do not immediately rise to the surface…it takes them about 20-25 ms to get in the mood. Compare with a slow motion video of popping a water balloon in air:
Again, watch how it takes for gravity to kick in. It’s like Wile E. Coyote after having run off a cliff, hanging in midair holding a sign that says “EEP!” (via @BadAstronomer)
Astronomers have been able to view the same supernova in a distant part of the Universe several times due to the gravitational lensing effect of a cluster of galaxies in-between here and there. From Dennis Overbye in the NY Times:
Supernovas are among the most violent and rare events in the universe, occurring perhaps once per century in a typical galaxy. They outshine entire galaxies, spewing elemental particles like oxygen and gold out into space to form the foundations of new worlds, and leaving behind crushed remnants called neutron stars or black holes.
Because of the galaxy cluster standing between this star and the Hubble, “basically, we got to see the supernova four times,” Dr. Kelly said. And the explosion is expected to appear again in another part of the sky in the next 10 years. Timing the delays between its appearances, he explained, will allow astronomers to refine measurements of how fast the universe is expanding and to map the mysterious dark matter that supplies the bulk of the mass and gravitational oomph of the universe.
Scientists expect the supernova to reappear in the next few years. Gravitational lensing was predicted by Einstein’s general theory of relativity and as Overbye writes, “the heavens continue to light candles for Albert Einstein.”
For Scientific American, Jen Christiansen tracks down where the iconic image on the cover of Joy Division’s Unknown Pleasures came from. Designer Peter Saville found the image, a stacked graph of successive radio signals from pulsar CP 1919, in a 1977 astronomy encyclopedia but it actually originated in a 1970 Ph.D. thesis.
By now I had also combed through early discovery articles in scientific journals and every book anthology on pulsars I could get my hands on to learn more about early pulsar visualizations. The more I learned, the more this descriptor in the 1971 Ostriker caption began to feel significant; “computer-generated illustration.” The charts from Bell at Mullard were output in real time, using analogue plotting tools. A transition in technology from analogue to digital seemed to have been taking place between the discovery of pulsars in 1967 to the work being conducting at Arecibo in 1968 through the early 1970’s. A cohort of doctoral students from Cornell University seemed to be embracing that shift, working on the cutting edge of digital analysis and pulsar data output. One PhD thesis title from that group in particular caught my attention, “Radio Observations of the Pulse Profiles and Dispersion Measures of Twelve Pulsars,” by Harold D. Craft, Jr. (September 1970).
When a star gets old and fat, it explodes in a supernova, leaving a neutron star in its wake. Neutron stars are heavily magnetized and incredibly dense, approximately two times the mass of the Sun packed into an area the size of the borough of Queens. That’s right around the density of an atomic nucleus, which isn’t surprising given that neutron stars are mostly composed of neutrons. A teaspoon of neutron star would weigh billions of tons.
A pulsar is a neutron star that quickly rotates. As the star spins, electromagnetic beams are shot out of the magnetic poles, which sweep around in space like a lighthouse light. Pulsars can spin anywhere from once every few seconds to 700 times/second, with the surface speed approaching 1/4 of the speed of light. These successive waves of electromagnetic pulses, arriving every 1.34 seconds, are what’s depicted in the stacked graph. Metaphorical meanings of its placement on the cover of a Joy Division record are left as an exercise to the reader.
From the Physics arXiv Blog, a list of paradoxes in modern cosmological physics, i.e. areas where theory and observation disagree, sometimes by a whopping 120 orders of magnitude.
Perhaps the most dramatic, and potentially most important, of these paradoxes comes from the idea that the universe is expanding, one of the great successes of modern cosmology. It is based on a number of different observations.
The first is that other galaxies are all moving away from us. The evidence for this is that light from these galaxies is red-shifted. And the greater the distance, the bigger this red-shift.
Astrophysicists interpret this as evidence that more distant galaxies are travelling away from us more quickly. Indeed, the most recent evidence is that the expansion is accelerating.
What’s curious about this expansion is that space, and the vacuum associated with it, must somehow be created in this process. And yet how this can occur is not at all clear. “The creation of space is a new cosmological phenomenon, which has not been tested yet in physical laboratory,” says Baryshev.
What’s more, there is an energy associated with any given volume of the universe. If that volume increases, the inescapable conclusion is that this energy must increase as well. And yet physicists generally think that energy creation is forbidden.
Baryshev quotes the British cosmologist, Ted Harrison, on this topic: “The conclusion, whether we like it or not, is obvious: energy in the universe is not conserved,” says Harrison.
This is a problem that cosmologists are well aware of. And yet ask them about it and they shuffle their feet and stare at the ground. Clearly, any theorist who can solve this paradox will have a bright future in cosmology.
Luckily, these paradoxes are an opportunity to do some great science.
Nothing is faster than the speed of light. But compared to the unimaginable size of the Universe, light is actually extremely slow. This video is 45 minutes long and during that time, a photon emitted from the Sun1 will only travel through a portion of our solar system.
In our terrestrial view of things, the speed of light seems incredibly fast. But as soon as you view it against the vast distances of the universe, it’s unfortunately very slow. This animation illustrates, in realtime, the journey of a photon of light emitted from the sun and traveling across a portion of the solar system.
It takes light more than 43 minutes to travel to Jupiter and even to travel the diameter of the Sun takes 4.6 seconds. (thx, andy)