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Brian Koberlein
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Brian Koberlein

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Vaccines, Meteors, And Why Details Matter

It’s flu shot season, which means an annual popup of anti-vax memes in my social media feeds. Most of the memes this year are of the “OMG! The flu shot contains mercury!” variety. While it’s true that some versions of the flu vaccine do contain trace amounts of mercury, such a statement is largely meaningless.

Thimerosal, the organic compound used as a preservative in some vaccines, breaks down in the body into ethyl mercury. Since our bodies can remove ethyl mercury from our bodies, it doesn’t bioaccumulate. This is very different from methyl mercury, found in trace amounts in certain fish like tuna. Methyl mercury is hard for our bodies to remove, and can bioaccumulate. It’s the buildup of mercury over time that can be dangerous, which is why the FDA recommends limiting consumption of certain varieties of fish. While both compounds contain mercury, the two molecules are structurally different and behave differently in our bodies. It’s similar to the difference between ethyl alcohol and methyl alcohol. The former is found in beer and wine and used as a social lubricant, while the latter is used in things like antifreeze and is highly toxic. Simply stating some vaccines contain mercury is like saying “OMG! Beer contains antifreeze!”

The glossing over of these kinds of details is depressingly common in popular science writing. For example, a while back there were posts about how there is evidence of life found in some meteorites, supporting the idea that life came from outer space. What was actually found was that some meteorites, such as the Murchison meteorite, contain more than 70 types of amino acids, which are sometimes referred to as the building blocks of life. Since the fall of the Murchison meteorite was observed, and the meteorite was recovered soon after it reached Earth, we can be confident that those amino acids are not due to terrestrial contamination. It’s in the details, however, where things get interesting.

Amino acids are chiral molecules. This means they come in two different forms that are mirror images of each other. Each type of amino acid has a left handed and right handed version. Terrestrial organisms mainly use left-handed proteins (of which amino acids are the building blocks) and right-handed sugars. The amino acids on the Murchison meteorite were found to be roughly equal parts left and right handed. This means they were likely produced by a nonbiological process. We know from other studies that complex molecules can form in deep space. So the Murchison meteorite actually contradicts the idea that terrestrial life began in space. Cosmic amino acids may have played a role, but likely some mechanism on Earth gave rise to the handedness of biology we see today.

Often in science it’s the smallest of details that make all the difference. Some evidence can’t be reduced to a catchy headline, and doing so can often lead to headlines that are downright misleading.

Some vaccines contain mercury. Some meteorites contain amino acids. But it's in the details where things get interesting.

Brian Koberlein

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Dark Beginnings

Dark matter is one of the great unsolved mysteries of modern astronomy. We’ve reached the point where we know most matter in the cosmos is made of matter that interacts weakly with light if at all, but drives much of the gravitational interactions between galaxies. While it’s often portrayed as a modern idea added simply to shoehorn observations into the standard model, it actually has a history spanning more than a century, and the theory of dark matter has been refined and improved as we’ve learned more about our Universe.

The origins of dark matter can be traced to the 1600s. Soon after Isaac Newton presented his theory of universal gravity, some astronomers began to speculate about the existence of objects that might emit little or no light, but could still be known by their gravitational tug on bright objects like stars and planets. This idea was strengthened in the 1700s when Pierre Laplace argued that some objects might be massive enough to trap any light they emit (a simplistic idea of a black hole), and by the 1800s Urbain Le Verrier and John Couch Adams used gravitational anomalies in the motion of Uranus to predict the presence of Neptune. By this point astronomers had demonstrated the presence of dark nebulae, seen only by the light they absorb from bright objects behind them. It was clear that there was more in the Universe than could be seen by visible light.

Our modern take on dark matter as a major contributor to galactic mass can be traced to Fritz Zwicky. In 1933 he studied the motion of galaxies within the Coma Cluster. The Coma Cluster is a galactic supercluster containing more than 1,000 galaxies. Since these galaxies are gravitationally bound, the speed of these galaxies can provide a measure of the cluster’s mass. Basically, the more mass the cluster has, the wider the distribution of galactic speeds following a relation known as the virial theorem. A few years earlier Edwin Hubble had estimated that the Coma Cluster contained about 800 galaxies, each containing about a billion stars. Using the virial theorem Zwicky calculated a cluster mass more than 500 times larger than that of Hubble. Zwicky noted that if his measurements held true “dark matter is present in much greater amount than luminous matter.” Over the next couple decades the virial theorem was applied to other galaxy clusters with similar results. Not everyone accepted these results, largely because the virial theorem is a statistical calculation that depends upon certain assumptions. For example, it assumes the clusters are gravitationally bound. Perhaps the galaxies in these clusters are actually flying away from each other, so that the virial theorem simply doesn’t apply. But there was another line of evidence to support dark matter. One that couldn’t be so easily dismissed.

In the early 1900s astronomers began to look at the spectra of galaxies. From this they could determine the speeds of stars as a function of their distance from galactic center, known as a galactic rotation curve. Seen in visible light, most galaxies have a bright center, dimming as you move away from the center. This would imply most of the stars (and thus most of the mass) is located near the center of a galaxy. If that’s the case, one would expect stars far from the center to move much more slowly than stars near the center, just as in our solar system Earth orbits the Sun much more quickly than distant Pluto. When Max Wolf and Vesto Slipher measured the rotation curve of the Andromeda galaxy, they found it was basically flat, meaning that stars moved at the same speed regardless of their distance from galactic center. One solution to this mystery was that Andromeda is surrounded by a halo of dark matter so that its mass is not concentrated in the center. While other galaxies showed similar rotation curves, seeming to support the presence of dark matter, even Fritz Zwicky was skeptical. Gas and dust within a galaxy might exert some kind of drag on fast moving stars, he argued, thus flattening the rotation curves. But by the 1950s radio astronomy had progressed to the point where it could detect monatomic hydrogen through the famous 21 centimeter line. Radio observations of both the Andromeda galaxy and our own Milky Way galaxy showed similarly flat rotation curves. Since hydrogen is by far the most abundant element in the Universe, the results proved that not only stars, but the gas of any dark nebulae were orbiting the galaxies at similar speeds. Either galaxies contained significant dark matter, or our understanding of gravity was very wrong.

As the evidence for dark matter grew, it soon became clear that there was a serious problem. Assuming our gravitational theories were correct, dark matter must be far more plentiful than luminous matter both in galaxies and among galactic clusters. If this dark matter consisted of things like dark nebulae, their presence should be detectable by the light they absorb. If so much dark matter exists, it must not only be non-luminous, it must not absorb light either. It couldn’t simply be regular matter that is cold and dark, but must be something very different. This was such a radial idea that many astronomers questioned the validity of Newtonian gravity. By the 1980s several alternative gravitational models, the most famous of which was Modified Newtonian Dynamics (MoND), proposed by Mordehai Milgrom. While these models did work well for things like dwarf galaxies, they worked horribly with things like galactic clusters. Dark matter models were not without their problems, but they agreed more readily with observations.

In the past couple decades data gathered from gravitational lensing and deep sky surveys have allowed us to further refine our dark matter models. From the large scale distribution of galaxies we know that dark matter must be cold and slow moving, so the countless neutrinos that zip through the cosmos at nearly the speed of light cannot account for dark matter. From gravitational lensing we know the distribution of dark matter within galaxies. By observing the distribution of dark matter within colliding galaxies we know that not only does dark matter not interact with light, it also doesn’t interact strongly with regular matter or itself. While this further verifies the existence of dark matter, it also makes it more difficult to determine just what dark matter is.

The most recent challenge for dark matter has been to determine its composition. The most popular idea is that they are Weakly Interacting Massive Particles (WIMPs), but these particles should be detectible by the same experiments used to observe astrophysical neutrinos. So far, no evidence for these particles has been forthcoming. Direct efforts to detect dark matter have only served to eliminate our options for dark matter. After studying dark matter for more than a century, it continues to elude us.

And so the dark history of dark matter continues.

The history of dark matter spans more than a century, and continues to raise interesting questions.

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Strange Relations

There's an interesting correlation between the distribution of visible matter in a galaxy and the radial acceleration of stars around a galaxy. It could allow modified gravity models to challenge dark matter once again.

New research on galaxy rotation casts a shadow on dark matter.
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Encyclopedia Galactica

A popular dream of science fiction has been the creation of a vast database containing all known information about the galaxy, an Encyclopedia Galactica. It would list the characteristics of stars in the Milky Way, their planets, and even the history of human alien civilizations. While still a dream in most ways, the foundation of such a cosmic Library of Alexandria is being laid with the first release of data from the Gaia spacecraft.

The initial data release contains information on more than a billion stars. It gives the position and brightness of 1,140,622,719 stars in our galaxy and nearby dwarf galaxies, with distance and motion data for about 2 million stars. If a cosmic encyclopedia is created, it will begin with the data from Gaia. What makes the data so powerful is its combination of size and precision. Other spacecraft such as Hipparcos have mapped about 100,000 stars, but the Gaia mission will precisely determine the position and motion of more than a billion stars. That’s still only about 1% of the total number of stars in our galaxy, but it’s large enough that we can study aspect of the Milky Way like never before.

For example, since stellar motion is determined by gravitational interactions, the data will allow us to determine the overall mass and distribution of mass within the Milky Way. Comparing the mass distribution to the distribution of stars, we can better determine the distribution of dark matter in our galaxy. The data will also allow us to determine the motions of stars within clusters, which will not only help us understand the origin and evolution of star clusters, it will help us learn more about our galactic history.

Measuring the positions and motions of all these stars requires precise observations of the stars’ brightness and spectra over time. This data can also be used to discover exoplanets. It’s expected that Gaia will discover any Jupiter-mass planet orbiting stars within 150 light years of Earth. It could detect nearly 50,000 planets over the course of its mission. The data not only determines the location of stars, but also their size and type. The initial data contained 3,194 variable stars, which not only help us understand stellar evolution, they are also used to determine galactic distances. Overall the precision of the data is so high it will allow us to test theories such as general relativity in new and subtle ways, possibly leading to the discovery of new physics.

Then there are the secondary discoveries that might occur. While Gaia’s mission is to measure stars, in practice it measures the brightness and location of any object over an apparent magnitude of 20. This includes countless asteroids, Kuiper Belt objects, and any large outer solar system planet within 200 parsecs. It will also observe occultations of stars by solar system bodies, such as the recent occultation of a faint star by Pluto, which helped us study Pluto’s atmosphere.

Perhaps what makes Gaia most exciting is that the data is released publicly. Since anyone can access the data, it can be used in ways the Gaia team hasn’t anticipated. It truly is a great encyclopedia available to all.
The Gaia mission has released initial data on more than a billion stars in our galaxy.
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Hey.Foundation trilogy.Asimov would be proud.
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Planet X-Ray

Pluto is emitting x-rays, and we don’t know why.

X-rays aren’t something we’d expect from Pluto, since the planet has no clear way of generating them. It’s a small, cold world with little magnetic field. Some solar x-rays might scatter off Pluto in our direction, but the level of x-rays is higher than what could be produced by scattering. So what gives?

The most likely explanation is that the x-rays are produced through an interaction between the solar wind and Pluto’s atmosphere. As the New Horizon’s flyby found, Pluto’s atmosphere is actually quite stable, so interactions with the solar wind could produce x-rays. Similar interactions between the solar wind and the comas of comets have been seen to produce x-rays. But the level of x-rays from Pluto is even higher than we’d expect from such an interaction, so that isn’t the whole story.

While these x-rays are a mystery, it’s important to keep in mind that the amount of data is actually quite small. Only seven x-rays were detected by the Chandra spacecraft in this study. That’s enough to make random chance unlikely, but it’s difficult to get much detail from such a small sample. What this study does show is that Pluto does produce x-rays, and perhaps we should give it a closer look.

Paper: C.M. Lisse, et al. The puzzling detection of x-rays from Pluto by Chandra. Icarus. (2016) DOI: 10.1016/j.icarus.2016.07.008

Pluto is emitting x-rays, and we don't know why.
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come on +Brian Koberlein , what do you think of my superconducting tholin-layer theory?! With no more commenting on your posts, this is my last chance to establish my astrophysics credentials! ;)

PS - I can take rejection!
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The Constant Of Time

When Edwin Hubble first demonstrated the Universe was expanding in 1929, you could do a simple calculation to determine the age of the Universe. Take the rate at which galaxies expand from each other (known as the Hubble constant H) and set it equal to the inverse age of the cosmos (1/t). This simple model assumed that the Universe expands at a constant rate, thus Ht = 1. When this was first proposed within the context of the big bang model, it actually raised a few questions. Early measurements of the Hubble constant were much higher than the current accepted value, which gave a cosmic age that was actually younger than some stars.

We now know the Universe hasn’t expanded at a constant rate. The rate of cosmic expansion is determined both by dark energy driving galaxies apart, and the overall density of matter in the Universe, which tries to slow the rate of expansion. In the early universe, matter dominated, so the rate of expansion was actually decreasing. About 6.5 billion years ago the average density of the Universe dropped to the point that dark energy began to dominate, and the Universe began expanding at an ever increasing rate. An accurate determination of the age of the Universe has to account for the initial inflationary period, then deceleration, then acceleration. If you do that you get an age of about 13.8 billion years, which is the currently accepted age.

Because of this variation in cosmic expansion, the Hubble constant has changed over cosmic time. This is why you can’t simply set Ht = 1. And yet, if you take the current Hubble constant and multiply it by the currently accepted age of the Universe, you get exactly 1 (to within known uncertainties). In other words, if the Universe had expanded at a constant rate, it would be exactly the same size and age as the Universe currently is. This is known as the synchronicity problem. It’s not a problem, per se, but rather an interesting coincidence. This hasn’t been true for any other epoch of the cosmos. It’s also not the only odd coincidence. The vacuum energy density (as determined by the Hubble constant) and the matter energy density are also about equal, and is known as the coincidence problem.

As the Universe expands the matter density drops, while the vacuum density doesn’t, so it’s tempting to think that the synchronicity problem and the coincidence problem are two sides of the same coin. But a recent work shows this isn’t the case. By varying the parameters of a hypothetical universe, one could create a model where one is true but the other is not. These two unusual correlations are independent of each other. This raises the question of whether the two actually are related by some unknown physical process. We always have to be a bit careful with these kinds of questions. It is perfectly possible that the two “problems” are just due to random flukes. But when you start seeing coincidences in your data it is sometimes worth exploring.

If there is a connection, it will only be a matter of time before we find it.

Paper: Arturo Avelino and Robert P. Kirshner. The dimensionless age of the Universe: a riddle for our time. The Astrophysical Journal, Volume 828, Number 1 (2016) arXiv:1607.00002 [astro-ph.CO]

The rate of cosmic expansion has changed over time. So why does it look like a constantly expanding universe?
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+Lisa Doodson +Lisa Doodson 🐳 Equinox more like it. See Quintom pysic at the moment has to do with 💧 as of age of Aquarius. See piceses consolation has got so much shit in it we don't call them whales but uglys... See revelations was glorious compared to was coming.. Every culture in this worldly ignorant bunch of race.. What the one symbol Mayans feared most???? Seen or heard anything new up up away!!!! Don't forget for in the days of Noah BEFORE the flood it shall be at the end times... Mohhaahahaaaaaa beached as bro. Everyday a blessings lovenlight love thy nabour... Just not these ones unto death... Yes.. B4 the flood. Capiiton. Blessings
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Brian Koberlein

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Google+ Comments Are Dead: Discuss

One of the big plusses of G+ has been the comments. Unlike other social networks, G+ has had seriously good conversations. I can't speak for others, but I remember when comments on my posts not only added to my posts, they drove new conversations. People would discuss the implications of new research, argue over the validity of dark matter and dark energy, discuss how best to credit and use the work of others, and held me to task when I made mistakes. There were always times when some drive-by troll would start a flame war, or someone would attack people in such a way that they were eventually banned, but these were limited. Which was good, because on personal posts only the author can moderate comments. I tried to limit moderation to a few simple rules: no spam, be civil, and try to stay on the topic at hand. All moderation has some manner of bias, but I tried to keep it limited and fair.

When G+ changed its format, the floodgate of comments opened, and spam became a much, much bigger issue. Almost overnight comments were flooded with spam, drive-bys, and trolls. As my posts became popular it's gotten worse and worse. Moderating comments soon became a full time job, and with no one to hand it off to I simply couldn't keep up.

The folks at Google have actually asked for feedback from many popular folks, including myself. How could they make G+ better?

I asked for basic moderation tools, specifically:

1. First time comments don't appear until they pass moderation. This ensures that all spam, hateful comments, etc. don't even get past the post. Since they never appear there is no reward for posting them, and they don't have a chance to feed retaliatory comments.

2. Commenters that have had a few comments approved on your posts get theirs to appear automatically, i.e. if you can play nicely you can play without supervision.

Those two conditions alone would, in my opinion, basically kill spam and trolling. Since comments don't automatically appear, the game of spam/troll and run becomes pointless.

What Google gave us instead was the ability to add images to comments, bringing with it another layer of spam.

For the past two days I've had to delete dozens of spam images, including some of a pornographic nature. Links to "make easy money" and "find russian brides." Then there has been the four pseudoscience flame wars and three religious flame wars, all on different posts. Despite deleting comments and banning the instigators they keep raging. In part, as I realized today, that my blocking of people hides their comments from me, but not from others, so I have to activate viewing them again in order to delete them.

Then there's been a flood of self promoters who go through dozens (in one case nearly a hundred) of my posts giving them +1s and linking to their own pages in the comments.

All this in only TWO DAYS. And it keeps happening day after day after day. The notification box that awaited me this morning was so dismal I forced myself to try turning off comments before leaving G+ entirely. I simply cannot keep up with all the moderation. I've tried just leaving them unless they are too egregious, but those comments simply feed bad behavior. I have come to dread opening G+ anymore.

I'm done. I have to be done. It's too much work to do Google's job. This is the last post where comments will be open, and I won't be moderating them. I don't know if I'll open comments again, but they are going to be closed for a while.

If y'all want a discussion, you can have it on my blog. I'll even start a forum if that's what you want. I know it's not G+, but it will at least be free of spam and trolls.

For now, y'all get the last word. Make it count.
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You are right! Implementing these two rules would stop most all of the spam and inappropriate comments. It would also put some responsibility on the poster to approve the comments and wouldn't help those who post and run!! I'd like to see these functions even if they were optional.
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Why Are Comments Off?

In the words of the great philosopher Popeye, That's all I can stands, I can't stands no more. 
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My god's book said this 1,000 years ago
Hi! +1
Shut up about your stupid god!
Typical NASA cgi lies

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Ignorance Peddling In The Age Of YouTube

Devil’s tower, a laccolithic butte in Wyoming, is the stump of an ancient silicon tree. This amazing fact was sent to me by a reader complete with YouTube link for proof. If only I would watch the video with an open mind, I would learn the error of my scientific ways.

The video itself follows a common pattern, where an amazing claim is made, and the evidence presented is simply that two things look similar. Since an intrusion of magma through Earth’s crust looks somewhat similar to a tree stump, it must be a giant tree stump. It is the same method used by those who claim the Earth is flat, deny global warming and evolution, or espouse young Earth creationism, the electric universe, the doomsday planet Nibiru, that vaccines cause autism, and even that our solar system moves in a helical vortex. Their arguments are buttressed by claims that science is closed-minded, arrogant and dogmatic, or simply covering up the truth to protect their jobs.

It’s tempting to laugh these ideas off. After all, fringe ideas have always been proposed throughout history. But the difference is that with the rise of YouTube and social media this ideas spread faster and can become more ingrained in the minds of followers. The “Devil’s tower is a tree stump” video has more than half a million views, and is posted by someone with nearly three quarter of a million subscribers. That’s more than subscribe to the Sixty Symbols video series, for example. I can almost guarantee that in response to this post supporters of some of the pseudoscience I listed above will send me long diatribes about how their model shouldn’t be lumped in with the others. As wrong as these ideas are, they have staunch supporters willing to defend them. Not only do supporters of pseudoscience defend their ideas, but they vote and drive political conversations. Our society is shaped in part by these ideas, whether we like it or not. So it’s important to push back against these claims.

That might sound like I’m saying people are stupid, and that they need to be told what to think by intelligent and knowledgeable scientists like me. I’m not. Being wrong about a particular concept doesn’t make you stupid, and being open to new ideas even when they sound crazy at first is part of the curiosity science tries to foster. The problem isn’t stupidity or ignorance, it’s a failure of critical thought. And it’s not just a problem with pseudoscience advocates. Most modern scientific discoveries are promoted through press releases and media packets, many of which don’t even link to the actual research. They use exactly the same approach as the video above, where a few pretty pictures are used to support a wild scientific claim without linking to any actual evidence. A press release made without citing research is just as pseudoscientific as a YouTube video making unsubstantiated claims. We’re all capable of being intellectually lazy.

The good news is that critical analysis and intellectual discourse can be encouraged and promoted. The same tools that are used to promote pseudoscientific ideas can be used to raise the bar on scientific discussion. But making that change depends upon those of us who want to see a richer and more thoughtful exploration of knowledge. It’s easy to point fingers at the fringe and declare how poorly they behave. It’s more difficult to look at ourselves with a critical eye. That means calling out press releases and popular news stories that don’t cite actual research. It means taking the time to present ideas clearly as well as the evidence behind them. And it means having the patience to engage in discussions with those of opposing ideas, even though sometimes it will feel like feeding the trolls. If we want to promote knowledge and critical thought, as lovers and promoters of scientific ideals we have to encourage it ourselves.

If we don’t do this, then we are simply peddling ignorance in the name of knowledge.
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+Paulette Taverner "we are just energy".
Energy that has been manipulated and shaped by 9 billion years of evolving suns, plus 4 billion years of our sun and our planet evolving.
Most definitely not "just" energy.
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OMG! Beer contains antifreeze!

I've been getting a ton of anti-vax posts in my social media feeds, particularly those claiming that flu shots contain mercury. While that's true for some versions of the flu shot, it's only the beginning of the story.
Some vaccines contain mercury. Some meteorites contain amino acids. But it's in the details where things get interesting.
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Jupiter Rising

The Juno spacecraft has captured detailed images of Jupiter’s north pole for the first time. It’s churning, mottled patterns are quite different from the familiar Jovian clouds.

On the one hand this is somewhat to be expected. Jupiter generates more heat in its interior than it receives from the Sun, and so a pattern of convection forms, where warmer material rises to the surface, then cools and sinks again to the depths. Near the equatorial region Jupiter’s fast rotation smears out these patterns into the familiar band patterns, but near the poles there is no great rotation to create a banded pattern.

On the other hand, the view is quite unexpected. Saturn, likewise, generates more heat than it receives, but on Saturn the banded patterns still exist close to the poles. Then there is the fact that Saturn’s north pole has a hexagon pattern not seen on Jupiter. It’s not clear why the two gas planets should have such different poles.

Jupiter's polar regions are very different from its equatorial region.
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The Enemy's Gate Is Down

I’ve been getting a flurry of emails and comments recently from folks who don’t believe the Earth is round. It’s pretty straightforward to demonstrate to yourself that the Earth is indeed round, but this time the argument is about gravity and Earth’s (supposed) rotation. Water droplets on a ball will fly off if you rotate the ball due to centrifugal force. If the Earth rotates once a day, then stuff on the equator is moving at over 1,000 mph, while stuff near the poles is barely moving. How can gravity be strong enough to keep things from flying off the equator without simultaneously crushing things at the poles?

The basic idea of gravity is that masses are mutually attracted to each other. As Newton described it, masses exert a force on other masses depending on how much mass it has, and how far away it is. Near the surface of the Earth, the gravitational force is about 10 times your mass. This number comes from that fact that force is a product of mass and acceleration, and the acceleration of gravity is about 10 meters per square second. That means that if you took a mass and let go of it, its speed would increase by about 10 meters per second (22 mph) each second. If the Earth weren’t rotating, the force of gravity would be basically the same everywhere on the planet, and “down” would always be toward the center of the Earth. But the Earth is rotating, say the scientists, so surely that would have an effect, right?

It turns out centrifugal force is easy to measure in the lab. Just swing a mass and measure how much the mass seems to pull outward. Yes, I know some of you will point out that this actually involves centripetal force, but the end result is the same. A common introductory physics lab involves performing just such an experiment to see how the speed of an object affects the centrifugal force. What you find is that the force depends upon the square of the speed divided by the radius of the circular motion. At the equator an object is moving about 1,000 mph, and it’s moving in a circle with a radius of about 4,000 miles. Plug these into our equation and that gives 250 miles per square hour. That sounds huge, but if you convert it to metric, you get 0.03 meters per square second. So gravity pulls an object at the equator with a force of about 10 times its mass, while the centrifugal force is pulling it away from the Earth at about 0.03 times its mass. Yes, things at the equator are moving fast, but the radius of the Earth is so large that it doesn’t produce much centrifugal force.

Since centrifugal force is only about 0.3% of the gravitational force, gravity always dominates, and we don’t notice the centrifugal force in our everyday lives. But modern gravitational measurements are extremely sensitive. We’ve measured the variation of gravity all over the globe, and we find it varies with latitude just as predicted by Newtonian gravity and centrifugal force. Earth’s rotation means you are slightly lighter at the equator, but Earth would have to rotate much, much faster to overcome gravity. Earth isn’t the only place where centrifugal force has an effect. Saturn, for example, has a day that is only 10 hour long, and as a result it’s equator is moving at more than 23,000 mph compared to its poles. That isn’t enough to make things fly off Saturn, but it does mean that the centrifugal force at the equator is about 19% of Saturn’s surface gravity. As a result Saturn bows outward at its equator.

So Earth’s rotation really does mean that you weigh less at the equator. The effect is small, but we can measure it, and it confirms once again that the Earth is round.

The equator of the Earth moves at more than 1,000 mph, so why don't things at the equator fly into space?
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+Nick Alcock Yes, we are trying.. and another chapter awaits.. 
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The Universe is amazing, let me tell you.
An astrophysicist and physics professor at Rochester Institute of Technology.  Author of "Astrophysics Through Computation" with David Meisel.  Creator of the science outreach project Prove Your World, developing a science television show for children.

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