Bad Astronomy
The entire universe in blog form

May 18 2016 8:45 AM

Watch the Expansion of Debris Hurled Into Space by a Supernova

When you look at the image above, you may be reminded of a cell undergoing mitosis. Certainly, even if you knew it was an astronomical object, you’d be excused if you missed the idea that it’s actually one of the most catastrophic events in the Universe: a supernova.

The violence of a supernova is almost too huge to overstate. When a star explodes (an entire star! Exploding!), the energies involved crush our human perspective into dust. There are two general types of supernovae; one where the core of a massive star collapses, generates ridiculous amounts of energy, and the outer layers explode outward. The other — the kind we are concerned with here — is when a white dwarf (the dead, dense core of normal star) steals matter from a nearby companion, compresses it, and eventually explodes. In both cases, a vast amount of material, as much as an octillion tons of vaporized star-matter, is hurled outward at a significant fraction of the speed of light. This debris covers millions of kilometers in seconds, billions in hours, detonated by a blast that’s equivalent to the entire lifetime’s supply of energy from a star ignited all at once*.

We have observed literally thousands of these events, but, even for the closest, the fantastic speeds of their motions are dwarfed by their distance from us, seemingly frozen in time when you see their images.

Only, that is, if you aren’t patient. In a single image that motion is invisible, but wait a few years, and even the chilling remoteness of a galactic supernova cannot erase the motion of its debris.

And we do have the sharp eyes and glacial endurance of telescopes. In the case of the image above, the Chandra X-ray Observatory (together with radio observations from the Very Large Array in New Mexico) observed a supernova remnant over the course of several years, and when those images are put together in an animation, the expansion of the vast cloud of matter is visible. Behold!

Let that animation repeat a few times; the motion is most apparent in the outer blue ring, the glow from electrons heated to 10 million degrees Celsius by the exploded star’s shock wave. The debris itself is turbulent, bubbling away from the center, and its motion too can be seen over the decade and a half of observations.

As the animation plays, let this thought run through your brain: These observations indicate that in some places in the cloud, the debris is expanding at a numbing 5,000 kilometers per second. In the time it takes you read this paragraph, the gas will have traveled comfortably farther than the diameter of the Earth.

The star that gave up its life for these observations lies between 6,000 and 9,000 light-years from us—60,000 to 90,000 trillion kilometers—and when its light reached Earth in 1572, it was bright enough to outshine every other star in the sky, and even be visible during broad daylight. Astronomer Tycho Brahe was captivated by it, documenting his detailed observations made before telescopes were commonly used to peer into the sky. Had he been able to see its motion, he may have guessed what it was.

To me, this is thrilling. Astronomical objects are so distant and so vast that change in them seems impossible; it feels as if they will appear now as they always have, and always will. But the Universe changes at its own pace, and that evolution is perceivable by humans due to our own curiosity and sense of exploration. Despite its appearance over the puny duration of a human life span, the cosmos is neither eternal nor static. But we only notice if we’re paying attention.

P.S. This type of animation has also been done for the famous Crab Nebula, showing the debris expansion over time as well. It can even be used to determine when the star actually exploded!

*Correction, May 19, 2016: I originally described only a core collapse supernova, but this particular event was from a Type Ia, where a white dwarf explodes. My thanks to Peter Edmonds for pointing this out to me!

May 17 2016 11:45 AM

Sunrise on a Crater Rim

Every now and again, a photograph from a spacecraft stops me dead in my tracks. The shot above is one such image, taken by the wonderful Lunar Reconnaissance Orbiter.

It shows sunrise on the western part of the rim of Jackson Crater, on the far side of the Moon. Jackson is a relatively young crater about 70 km across, with a well-defined rim that extends around it like a single, long rampart bent into a battered circle.

Because the rim rises up from the terrain around it, it’s the first to be lit by the rays of the rising Sun. The Moon spins once every 27 days or so, so sunrise takes 27 times longer than it does on Earth. Here on Earth the Sun takes about two minutes to clear the horizon, so on the Moon it takes roughly an hour.*

What a view that must be! And what magnificent scenery it illuminates. On the Moon, with no atmosphere, there’s no reddish-pink hue to the sky. It’s black all the time, even during the day. When the Sun rises, it must be like a light switch being thrown. Still, the low angle will illuminate the level ground less than something angled up, tilted such that it’s flatter to the incoming rays. So the inside wall of the rim is lit well, the lunar terrain outside the rim still appears somewhat dim, and the inside of the crater is cloaked in inky blackness.

Jackson crater
Jackson crater in all its glory, also taken by LRO, this time in a nadir view.

NASA/Arizona State University/Lunar Reconnaissance Orbiter

The combination of stark lighting, soft lighting, and no lighting at all is entrancing. The moon is always a beautiful object to see, but it’s the shadows that add to the poetry of the composition. There’s mystery and intrigue in the shadows’ edges.

Another reason this image is so striking is that most LRO shots are “nadir angle,” looking straight down at the surface below the spacecraft. This one was taken at an oblique angle, the better to see contours and shadows (a zoomable map of Jackson using LRO nadir images shows just how different it looks in full sunlight and peering straight down at it). Between its unusual angle and the striking lighting, this image has quickly become one of my favorites from a mission that has provided so many stunning photographs of our cosmic companion.

*Ignoring atmospheric effects (on Earth) and latitude, which can actually change the length of sunset significantly. There’s no air on the Moon, but latitude effects can make the sunrise last for many hours or more near the poles.

May 17 2016 8:45 AM

March … I mean April 2016 Is the Sixth … I Mean Seventh Temperature Record-Breaking Month in a Row

N.B. If this article sounds familiar, it should. This has been happening so frequently I just copied the post for March and updated it.

October. November. December. January. February. March. And now April.

For the sixth seventh month in a row, we’ve had a month that has broken the global high temperature record. And not just broken it, but shattered it, blasting through it like the previous record wasn’t even there.

According to NASA’s Goddard Institute for Space Studies, March April 2016 was the hottest March April on record, going back 136 years. It was a staggering 1.28°C 1.11°C above average across the planet.* The previous March April record, from 2010, was 0.92° 0.87° above average. This year took a huge jump over that.

Welcome to the new normal, and our new world.

As you can see from the map above, much of this incredible heat spike is located in the extreme northern latitudes. That is not good; it’s this region that’s most fragile to heating. Temperatures soaring to 7° or more above normal means more ice melting, a longer melting season, loss of thinner ice, loss of longer-term ice, and most alarmingly the dumping of billions of tons of fresh water into the saltier ocean which can and will disrupt the Earth’s ability to move that heat around.

What’s going on? El Niño might be the obvious culprit, but in fact it’s only contributing a small amount of overall warming to the globe, probably around 0.1° C or so. That’s not nearly enough to account for this. It’s almost certain that even without El Niño we’d be experiencing record heat.

Most likely there is a confluence of events going on to produce this huge spike in temperature—latent heat in the Pacific waters, wind patterns distributing it, and more.

JMA temperatures
The Japanese Meteorological Agency measured similar temperatures as GISS (though it uses a different baseline for the average). Note the trend. See a "pause"? I don't.

Japanese Meteorological Agency

And underlying it all, stoking the fire, is us. Humans. Climate scientists—experts who have devoted their lives to studying and understanding how this all works—agree to an extraordinary degree that humans are responsible for the heating of our planet.

That’s why we’re seeing so many records lately; El Niño might produce a spike, but that spike is sitting on top of an upward trend, the physical manifestation of human induced global warming, driven mostly by our dumping 40 billion tons of carbon dioxide into the air every year.

Until our politicians recognize that this is a threat, and a very serious one, things are unlikely to change much. And the way I see it, the only way to get our politicians to recognize that is to change the politicians we have in office.

That’s a new world we need, and one I sincerely hope we make happen.

*GISS uses the temperatures from 1951–1980 to calculate the average. The Japanese Meteorological Agency uses 1981–2010, which gives different anomaly numbers, but the trend remains the same. Realistically, the range GISS uses is better; by 1981 global warming was already causing average temperatures to rise.

May 16 2016 9:00 AM

Astronomers Take the Measure of a Monster Black Hole

Seventy million light-years from Earth lies the somewhat odd galaxy NGC 1332. It falls somewhere in between the two main galaxy types of elliptical and spiral; it’s disk shaped but lacks obvious spiral arms and is quite elongated.

Like all big galaxies, though, it has a black hole in its very center. And not just any black hole, but a supermassive black hole. Current astronomical thinking is that these monsters form at the same time as the galaxy, and affect each other’s growth. Gas pours down to the center from the growing galaxy, feeding the black hole, and the black hole also emits a ferocious wind that can curtail the birth of stars in the galaxy.

When we look at a galaxy now, billions of years later, we see correlations between the mass of the black hole and the behavior of the galaxy. Because of that, knowing the mass of the black hole is important in understanding how galaxies are born, age, and evolve.

But how do you measure the mass of a black hole?

Isaac Newton helps us here. Objects near the black hole orbit it, and the speed at which they move (together with their distance from it) reveals the strength of the gravity of the black hole. That in turn—as Newton pointed out 400 years ago—depends on the mass doing the pulling.

It’s not that simple, of course! But it can be done, and has been done. A camera I worked on for Hubble, called STIS, was designed in part to be able to make these kinds of measurements.

For NGC 1332, various methods have been used, including measuring the velocities of stars near the center of the galaxy (and therefore close to the black hole) and looking at hot gas surrounding the galaxy. These methods have some issues, though, and can have large uncertainties.

A new telescope has come online recently, though, and has something to say about the matter. ALMA, the Atacama Large Millimeter/submillimeter Array, is a collection of large and very sensitive telescopes that detect light well outside the energy our eyes can see—between infrared and radio waves. Very cold gas and dust emit light in this range, and that’s where ALMA comes into the game.

NGC 1332
NGC 1332 (center) has been observed by Hubble (upper left), which showed the dust disk, and ALMA (upper right), which measured the Dopler shift across the disk.

A. Barth (UC Irvine), ALMA (NRAO/ESO/NAOJ); NASA/ESA Hubble; Carnegie-Irvine Galaxy Survey

Many black holes have huge, swirling disks of dust around them. These can be several hundred light years across, the whole thing moving around the supermassive black hole at high speed. Even though they’re big, from 70 million light-years away they look small and hard to see. ALMA, though, has terrific vision, able to resolve the disk down to just a dozen or so light-years from the central black hole.

That’s important. More than about 75 light-years out from the black hole, the gravity of the stars in the central region of the galaxy start to dominate; an estimated 10 billion stars exist within the central 750 light-years. So the closer you are to the black hole, the less an effect the stars have over the hole.

Measuring the disk rotation speed depends on measuring the Doppler effect: The part of the disk rotating around the black hole and heading toward us gets its light blueshifted (the wavelength gets compressed) while the side heading away from us is redshifted (the wavelengths get longer). ALMA can measure these shifts all along the disk, thereby measuring its velocity at different distances from the black hole.

By carefully modeling the gravitational effects of stars and the black hole and applying them to their observations, astronomers using ALMA have determined that the black hole has a mass of—I hope you’re sitting down—660 million times the mass of the Sun.

That’s a lot of hole.

As supermassive black holes go, that’s pretty supermassive-y. Quite a few have been found that are even bigger, but 660 million solar masses is pretty big. The Milky Way’s central black hole has a mass of only (!) about 4 million times the mass of the Sun, for comparison. So the one in NGC 1332 is a lot heftier than ours.

The good news is that this mass jibes with what’s been found for that galaxy using the other, independent methods. That gives us confidence the answer is correct. And the uncertainty in the ALMA measurements is pretty good, only about ±10 percent, better than most other measurements.

And it means we have yet another tool in our kit to measure the masses of these monsters. To put this in context, the ALMA observations aren’t a groundbreaking discovery, but they’re something just as important: a new way to probe distant cosmic objects. ALMA can perform similar observations on other galaxies, building up a census of black hole masses, which can be combined with all our other knowledge to help us better understand the lives of galaxies.

Galaxies are in many ways the building blocks of the Universe, and we happen to live in one, so I’m all for understanding them better. Everything we learn in this way is a piece of the puzzle and adds to the picture we build of the Universe.

I’m all for that, too.

May 15 2016 9:15 AM

Kinked Vortices

Wow! What a great example of von Kármán vortices!

This image, taken by Landsat 8 on May 3, 2016, shows a layer of stratocumulus clouds over the southern Indian Ocean. Poking above the layer is Mawson peak, a stratovolcano (lots of stratos in this shot) on Heard Island, one of a chain of volcanic islands near Antarctica.

The wind is blowing to the east near the island, which creates a wiggling tail of air downstream from the island as it flows around. As that tail “flaps”, the vortices are spawned, which then flow along with the wind. As I’ve written before:

Imagine you have a cylinder (a pencil, or a bucket, or a concrete pylon) that you place in flowing water. It’s an obstacle, and the water will flow around it.
However, near the cylinder’s surface the water slows, piling up a bit. The water farther from the cylinder is moving faster. This causes eddies (vortices) to form, curls in the water. This kind of motion is a bit unstable, and can cause a slight force, pushing the water perpendicular to the direction of flow. But the water all around the flow pushes back, causing a sort of oscillation, like a pendulum swinging. The result is a series of vortices forming and flowing downstream, one on each side of the obstruction, alternating in pattern.
An animation, in this case, is worth way more than a thousand words:
See how the fluid wiggles like a tadpole tail downstream? Eventually those vortices dissipate, losing coherence due to turbulence and drag. This process from start to finish is called “vortex shedding”, which just sounds intrinsically cool.

I love stuff like this, but what makes this even more fun is that in the Landsat 8 image, you can see the winds take an abrupt left turn, suddenly blowing north. That’s not easy to see in the clouds themselves, but it’s pretty obvious when you look at the chain of vortices, which make a sudden change in direction.

I found this picture (via @NASAEarth) on NASA’s terrific Earth Observatory Image of the Day site, one of my favorite places on the ‘net. They also mention that you can use the NASA WorldView page to zoom in and out of this shot, putting in in the greater context of flows around the southern continent. Amazing.

If you’re a US citizen, your tax dollars have already paid for all this, so go play. And if you’re not American, please allow us to let you use this for free. If I may speak for NASA, it’s honestly our pleasure to share our wonderful planet with you.

May 14 2016 10:48 AM

JWST Preps for Its Cameras

On the occasion of the recent revealing of the James Webb Space Telescope’s completed golden mirror array, I wrote a post describing the mirror(s) and how they got their golden atomically layered sheen.

Apropos of that, a couple of pretty nifty videos were recently released. Right now, JWST is in the big “clean room” at Goddard Space Flight Center, a huge warehouselike room that is kept almost entirely free of dust and other particulates that might muck up the optical works. There are a couple of webcams installed there (called “Webb cams,” because of course), and they were online when the entire mirror assembly was moved from the horizontal to vertical position. The result is pretty cool, especially when you consider just how big this assembly is: Remember, it’s 6.5 meters across!

I think my favorite part is at the 30-second mark when all the engineers in the bunny suits pose for a snapshot in front of it.

Here it is from another angle. The color is a bit distorted since it’s through a window, but the gold mirrors are still really something.

The reason the mirror was moved into this position is for the next very, very big step in the assembly: Installing the detectors behind the array. As I wrote before, the telescope is set up so that the big primary array collects the light from astronomical sources, reflects it up to a smaller secondary mirror, which in turn reflects that light down through a hole in the primary down into the instruments behind it. Those instruments include cameras and spectroscopes that will capture and dissect the light from distant galaxies, exploding stars, planets around other stars, Kuiper Belt objects in our own solar system, and much, much more.

Launch is planned for 2018, so there’s still plenty of time for assembly. I’m glad to see, after so many years, this whole thing finally coming together.

May 13 2016 9:00 AM

A Map That Goes Medieval on Mars

I’ve always been something of a map dork. I remember sitting in the back of the car on long rides as a kid, poring over the foldout maps, the U.S. map, and the key map my folks had under the passenger’s seat. It was so much fun to look at the roads, the landmarks, the cities, and places I had never heard of before. … It’s easy to see now why so many great stories start with finding a secret map.

Sometimes it goes the other way, though: Our stories inspire maps. Eleanor Lutz is an artist who has a self-professed love of medieval maps. She created an amazing and really quite beautiful map of Mars in that historical style. A portion is shown above; but you really should see and peruse the bigger version. It’s lovely. I’ll note she has prints of the map for sale, too.

She titled it “Here Be Robots,” which I love. As many people have pointed out, Mars is the only planet we know of inhabited entirely by robots. She has the landing sites of a few of them labeled, too.

I love the layout and flow of the map; it does have that medieval style, but with a modern take—it’s Mars, after all, and it’s real. This map is based on observations made by humans from Earth over the centuries, and then the details filled in by a score of probes sent there in the past half-century.

There’s a story for you: the exploration of an alien world, close by but still terribly distant, full of wonder and bizarre terrain and things we still don’t understand. And apropos of the style of the map, Mars is like a monster guarding the bridge; half the missions sent there have resulted in failure.

Like Scylla and Charybdis, Mars is a dangerous stretch of water, apt to eat unwary travelers. If there were ever a warning to put on a map like this, “Here Be Dragons” would be appropriate.

And yet we pushed through, and we have sent spacecraft there successfully, one after another. Unlike those old fables that promote the fear of the unknown, when we keep our eyes open, our heads high, and our brains fully on alert, we can push through the ignorance and turn terra incognita into Mars cognita.

Lutz has more of her artwork at her blog, Tabletop Whale, and on Deviantart. Seriously, watch this animated graphic of human fetal development. Amazing!

May 12 2016 1:16 PM

Reminder: There’s Still Space Left for Science Luau 2016

Look, I know you like science: You’re reading my blog (QED). And I’m guessing you like gorgeous tropical beaches, amazing food, incredible scenery, active volcanoes, and being around other science-minded people.

So let me gently remind you that there are slots still available for Science Luau 2016, a trip to the Big Island of Hawaii with bonus added SCIENCE! My wife and I are doing this through our company Science Getaways, where we start with vacations you’d want to go on anyway and then add tons of science to them.

Our agenda for Science Luau 2016 includes swimming with manta rays, visiting a native Hawaiian dry forest filled with endangered wiliwili trees, and touring the active Kilauea volcano … after sunset you can see the sulfurous plume illuminated from below by the glowing red-hot lava in the Halema'uma'u crater.

Manta ray
Want to meet this creature? This photo was taken from the boat trip we'll be on.

Fair Wind Big Island Ocean Guides

Sometimes, along the highway lined with jagged volcanic rocks laid down by eruptions decades ago, you can see families of goats walking along eating the sparse invasive grass, too. You know how I feel about that.

There'll be plenty of down time, too, where you an just sit back and enjoy the tropical island. I'll be packing my solar telescope, so we'll be doing some Sun observing (seeing towering prominences and winding filaments on the Sun is pretty common). And, of course, since my wife and I are running the show, I'll be there the whole time if you want to ask questions about astronomy or just sit on the ocean's edge and talk about the Universe.

This will be a fantastic trip, with the extra advantage of being with other science enthusiasts; we’ve found that many people who meet on these trips become lifelong friends. It’s really quite lovely.

So come join us! Who wouldn’t want to experience science in paradise?

Marcella and Phil Plait at Kilauea
Your hosts—my wife, Marcella, and I—standing in front of the Halema'uma'u crater vent on Kilauea, where we'll be taking you for Science Luau 2016.

Phil Plait

May 12 2016 8:30 AM

Ken Ham Really Doesn’t Understand Science

In 2014, popular science communicator Bill Nye “debated” creationist Ken Ham in a live webcast on YouTube. The event went pretty much as expected; Nye presented levelheaded evidence that science works, that evolution is real, and the Universe is very old, while Ham used bad logic, cherry-picking, and blatant twisting of scientific claims.

At the time (and still today) I think Nye made the right decision to participate in the event. Ham runs the Answers in Genesis ministry, and also the Creation Museum in Kentucky, and is well-known for his outrageous statements. It might seem silly to elevate the debate by paying any attention at all to Ham, but that ignores the fact that polls consistently show that half of the American population believes in some form of creationism.

We ignore this at our own peril.

Debating creationists is slippery. When your opponent doesn’t have to adhere to facts or logic, it’s tricky to find traction. My friend Zach Weinersmith once wrote that it's not that most creationists are anti-evolution, it's that they're anti-some distorted version of it told to them by their pastors.

He’s completely correct. That became even clearer to me when, shortly after the debate, BuzzFeed posted an article called “22 Messages From Creationists to People Who Believe in Evolution”. It was clear from the questions asked that the creationists involved had no idea about how evolution—even science itself—worked. The questions were universally based on false premises, a distortion of the science that made it actually pretty easy to answer those supposedly “gotcha” queries.

So I did answer them, in a post titled “Answers for Creationists.” I politely, but firmly, answered the questions posed, with links to expert sources if anyone wanted to dig a little deeper. It became one of my most popular articles of all time.

But as Zach pointed out, while these questions have been answered countless times, they still get asked. Why? The answer is obvious: Because the people asking those questions are still getting their information from people like Ken Ham who refuse to listen to anything science has to say and who still propagate falsehoods.

And I know this for a fact. That’s because Ham took to Twitter recently, posting a series of tweets that are not just wrong, but completely wrong, again demonstrating not just a misunderstanding of the topic, but a deep—I daresay fundamental—lack of understanding of even the most basic facts about the science he’s trying to deny.

It’s enlightening to look over what he said, because, again, a lot of people listen to him. And, like my previous post about answering creationists’ questions, I address this not to Ham, but to those who might listen to him: Perhaps you’ve heard these claims, and wondered about them. Here’s what science has to say about them.

First up: a bad Moon rising.

Like most such claims, it’s based on a kernel of truth: The Moon is in fact receding from the Earth, by a rate of about 4 centimeters per year. That’s roughly at the same rate your fingernails grow. The motion is due to the way Earth’s gravity affects the Moon, through the tidal force.

This means that, in the past, the Moon was closer to the Earth. And this is where—if you believe Ham—you run into a problem. The rate at which the Moon recedes depends very strongly on its distance from the Earth. In the past, when it was closer, it would have receded even more quickly.

According to Ham’s thinking, that means the Moon must be younger than science would say, only a billion or so years old at the most. A relatively simple calculation shows that, given the faster recession in the past, the Moon would have been touching the Earth about a billion years ago.

But this is incorrect. The real problem here is a common one with claims like this: taking a trend and simply running it backward or forward as if nothing ever changes.

In this case, there are other factors that affect the Moon’s recession rate, and Ham ignores them. For example, the shape of the continents and shorelines on Earth has a large effect as well (because the tidal interaction depends strongly on the way the water and seabed on Earth interact). It turns out that we have an anomalously high rate of recession today; many studies show that in the past the rate was actually slower.

Yes, initially, right after the Moon formed, it receded very rapidly indeed. But as it receded, other factors came into play. The numbers as we see them now easily allow a 4.5 billion year old Moon, just as scientific theory predicts.

Moving on, a little closer to home:

Again, a nugget of truth: The Earth’s magnetic field is changing. It does this all the time; it’s generated deep inside the Earth by our very hot iron core. The inner core is solid, but the outer core is liquid. The heat from the inner core causes the molten iron to rise, cool, and sink again. The iron is so hot it’s ionized (electrons are stripped from their atoms), and when an ionized fluid moves, it can generate a magnetic field. Changes in the liquid outer core change the Earth’s magnetic field, which we can see. For example, the magnetic poles of the Earth wander and the field strength changes.

If the field is decreasing now, it must have been stronger in the past. Ham’s mistake here, again, is assuming that increase in the past just keeps on going up and up. But we know that’s not true; there’s copious evidence the field cycles—waxing and waning in strength, and even reversing polarity. And even if Ham were right, he simply asserts life couldn’t exist in a stronger magnetic field but offers no reason why that might be the case.

Next, Ham ventures out into the Universe:

When you look at the spiral of cream in your coffee cup after you stir it, the inner part does spin faster than the outer parts. But galaxies aren’t like that. The arms aren’t coherent structures that spin like cream in your mug o’ java; they’re more like traveling traffic jams.

Pity Ham hasn’t seen my episode of Crash Course Astronomy where I talk about exactly this:

By the way, scientists have known for nearly a century that spiral arms don’t and shouldn’t wind themselves up.

Now let’s see what Ham has to say about the entire Universe:

This is a little confused. First of all, the use of the word pagan is odd. That refers to a religion that’s not one of the world’s main religions. But the Big Bang, and science at large, is not a religion. It’s not even faith-based.

But then Ham compounds his mistake:

The Big Bang is not a belief or a religion. It’s actually a model of how the Universe began, or more accurately what happened in the teeniest tiniest fraction of a second after the Universe began. And it’s supported by a vast amount of observational and theoretical evidence. No faith is needed.

And I just happen to have covered that in Crash Course Astronomy as well!

And then we get to this statement by Ham:

(I assume he meant “clearly,” not “clearing.”)

This one is odd as well. All he’s really saying is that science contradicts a literal interpretation of the Bible. But we’ve known for a long time. If that’s his complaint, he better have a seat. Even if you just stick to Genesis, the contradictions make for a long, long list.

In this case, the Bible says the Earth was created before the Sun. Science says they actually formed around the same time, 4.56 billion years ago. The Sun may have started nuclear fusion in its core, becoming an actual star, a few million years before the Earth grew to become a planet … but it hardly matters, since Ham isn’t really trying to refute any actual scientific claim here.

Also, he is very confused about what the Big Bang model says. That’s all about how the Universe itself got its start nearly 14 billion years ago. But the Sun has nothing to do with that; it was born nearly 10 billion years later. I see this confusion by creationists quite a bit; I strongly suspect it has to do more with trying to scare believers using the term “Big Bang” than understanding what the model is actually telling us.

I could go on and on; digging back through Ham’s tweets provides endless material for this exercise. But the point is clear: Ham’s mistake here is not sticking with his religion, but instead trying to disprove science using science. Given his bias, and his basic misunderstanding of what science is and how it works, he’s doomed to fail.

I’ve said this before, but it bears repeating: I think that people have the right to believe what they want. But when that belief clearly contradicts what we know to be true due to our observations of the Universe, and someone is vocal about it, well, we’re going to have a problem.

Ham clearly feels that his religion is threatened by science. That’s true, because it is. But not all religion feels that way; in the same year Ham stood up and said all those wrong things to Bill Nye, Pope Francis stood up and declared that the Big Bang and evolution are no threat to Catholic beliefs.

Catholicism is followed by more than 1 billion people on our planet. If their leader feels science is no threat to them, then maybe there’s hope that other, more intractable religions will follow suit.

Clearly, though, Ham won’t. The fact that he’s repeating provably false statements literally decades after they’ve been shown to be wrong, and publicly displaying his profound lack of understanding of science, shows that all he will do is dig in further.

We have all the evidence we need for that.

Post script: The claims Ham made, and my rebuttals, are a drop in the bucket compared with what’s out there. If you want to read more, then I suggest checking the following sites:

May 11 2016 11:45 AM

Cassini Takes a Last Close Look at Epimetheus

That lumpy pierogi in the photo above is Saturn’s moon Epimetheus, taken by the Cassini spacecraft in December 2015. This is a pretty cool shot; instead of the sharp blackness of space behind the moon, you see the fuzzy grayness of Saturn’s atmosphere. There’s a bit of what I believe is Saturn’s narrow F ring in the shot as well. This is an unusual geometry, giving a different perspective on the moon.

This is one of the highest-resolution images of Epimetheus that Cassini has sent back to Earth; it passed a mere 2,700 kilometers from the moon during the series of photos it took. Epimetheus is only about 115 kilometers across along its widest point, so it’s not huge (our Moon is 3,470 kilometers wide).

But it has a story to tell. It doesn’t look as sharply defined as you might expect; it has lots of dust on its surface that flows along the weak gravity to settle in low spots. The craters all look shallow, too. Some of that is from this material filling in the crater floors, but shallow craters are typical in icy bodies, where the impact energy tends to spread out more than down.

Epimetheus is weird in another way, too: It shares almost exactly the same orbit as the much larger moon Janus. Not quite exactly though. One is on a slightly smaller orbit than the other, and goes around Saturn every so slightly faster. As they slowly approach, they pull on each other with their mutual gravity. This effect gets big enough when they’re a few tens of thousands of kilometers apart that the one in the outer orbit is pulled back, dropping it closer to Saturn, while the one in the lower orbit is pulled forward, lifting it into a higher orbit. When it’s all done, the two moons swap orbits! The difference is only about 100 kilometers, but it’s enough that the moons swap roles, starting the process all over again.

Sadly, this is the last close flyby of the Moon by Cassini. It’ll pass it at a decent distance many times in the next year or two (and once as close as 6,000 kilometers in January 2017) but never again this close. In September 2017 Cassini is scheduled to end its mission by plunging into Saturn’s thick atmosphere, burning up as it sends its last few bits of data back toward Earth. This will be done to prevent it from accidentally hitting some moon in the future once the fuel has run out for maneuvers.

It’s sad, to be sure, but it’s also reason to celebrate. Cassini will have spent an astonishing 13 years orbiting Saturn, dwarfing everything we’ve ever learned about the ringed planet from before the mission.

All good things, as they say. Even all great, fantastic, and inspiring things.

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