The Gravity of the Situation


Oh Aunty Acid, I hate to be the bearer of bad news, but…there is gravity on the Moon.  There’s gravity everywhere.

I’ve seen this misconception enough that I figure it warrants some discussion.  Take a trip back in time with me to the days of Sir Isaac Newton.  Newton is known for many things, including his Law of Universal Gravitation, which says that any two particles in the Universe will attract each other with a force that is proportional to the product of their masses, and inversely proportional to the square of the distance between them.

In plain English, imagine you have two particles (and particles can mean any two objects, large or small.  They don’t have to be protons or electrons, for example.)  Let one of the particles have a mass of A kilograms, while the other particle has a mass of B kilograms.  As long as the two particles stay the exact same distance apart, then the gravitational pull between them will be proportional to AB.  If you increase the mass of either particle, then you increase the gravitational pull between them by that same ratio.  For example, double the mass of Particle A only, and the gravitational pull between A and B will also double.  If you double both masses, then the gravitational pull between them will quadruple, since 2 x 2 = 4.

The second part of Newton’s L.U.G. tells us that the gravitational attraction between any two “particles” decreases as the particles get farther apart from each other.  You might expect that, but the force doesn’t drop off in a linear way.  Instead, the force decreases with the square of the distance.  So let’s say that you keep the masses of A and B the same, but double the separation between them.  The gravitational force will drop to (1/2)², or 1/4 of its original value.  If you triple the separation between the particles, the gravitational pull drops to (1/3)² = 1/9 of its original value.

As you can see, gravity drops off rapidly with increasing distance.  Perhaps this is what leads some people to conclude that the Moon has no gravity; after all, it is quite far away from Earth by human standards.

But the Moon does have its own mass – quite a lot of it, in fact – and it has its own gravitational pull on nearby objects, separate and distinct from the Earth’s gravitational tug.  In fact, if you fly your spaceship to a point about 66,000 kilometers away from the Moon, the Moon’s gravity will be the dominant force that guides your trajectory.  This is what happened with the Apollo missions (indeed, with any lunar mission, manned or unmanned, that has ever successfully reached its target).

On the surface of the Moon, you experience a gravitational pull that is about 1/6 of what you experience on Earth.  Again, that’s not because you’re so far away from Earth; it’s because the Moon’s mass – albeit large – is still significantly less than the Earth’s mass.  When you stand on the Moon, there is simply less mass beneath your feet pulling you downward.

Contrary to what some people believe, there is even gravity in outer space, between the Earth and Moon, and anywhere else in the Universe that you care to look for it.  Remember, the gravitational influence of a body drops dramatically as you get farther from the body, but it never actually drops to zero.  Plug in any number you want for x, and the expression (1/x)² will never, ever be equal to zero.  So even when a spacecraft is far from Earth, far from the Moon, far even from the Sun, there will be a gravitational influence guiding its path.

(But wait a minute, you might interject, if there’s gravity everywhere, how come the astronauts float around inside the space station?  Check and mate, mister science nerd!)

Strangely enough, astronauts float inside the space station not because they have escaped gravity, but because gravity affects the space station as well as the astronauts.  The entire kit and kaboodle is in a state of free fall, just like on the Drop Zone ride.  The astronauts are indeed falling…and the space station is falling around them.  And they avoid falling to Earth because the station is also moving sideways fast enough that it falls around Earth instead of down to Earth.  But that’s a topic for another day.

So let’s summarize this meme’s misconception: there is gravity on the Moon (and everywhere else) so your saggy parts will continue to sag, albeit less severely.  But instead of trying to figure out how to get to the Moon, Aunty Acid, why don’t you focus on loving yourself the way you are?

Flat Earth Week, Day 7: Water We Going To Do About It?


All things must come to an end, except for Earth, which does not have ends because it is not flat.  We have reached the final day of Flat Earth week.

And wouldn’t you know it?  I’ve just stumbled across a veritable gold mine of Stupid Bad Flat Earth memes in the form of the Facebook community Flat Earth Matters.  There are enough memes there for a dozen Flat Earth weeks, but alas, I would never write about anything else if I tried to tackle them all.  Perhaps I’ll revisit the topic another time.  Until then, we bid a fond adieu to the looniest of loony conspiracy theories, and what better meme to send us off than this stunning display of Flat Earth “physics”?

Now the obvious answer to this meme is “Yes it does, because gravity.”  But you have to remember that Flat Earthers often don’t believe in gravity.  More specifically, they don’t believe that Earth has gravity, although some of them allow the Sun, Moon, planets, and stars to have gravitational influence because they think that this patches holes in their rapidly sinking model.

I’ll explain how water is able to “stick to a ball spinning 1000 mph”, although I know it won’t convince the average Flat Earther.  That’s okay; this blog has never really been about convincing the other side.  I try to bring logic and evidence to the table while ranting about the stupidity of memes, and the reader may decide for himself or herself whether I have sufficiently made my case.

So let’s start by establishing that Earth does in fact have gravity.  Newton said that anything with mass has a gravitational influence on any other object with mass, and there’s no reason to believe that Earth is any different.  Henry Cavendish showed in 1798 that objects much less massive than Earth have their own gravitational sway, albeit minuscule.

Einstein overhauled Newton’s ideas by showing that gravitation is actually the result of massive bodies curving the fabric of spacetime.  In doing so, Einstein predicted that not only can gravity affect the motion of objects with mass, but it can bend the path of massless light as well.  The famous Eddington experiment of 1919 proved that Einstein was correct.

Although Newton’s and Einstein’s models of gravity vary in important ways, they agree in one important detail: the more massive an object is, the more gravitational influence it wields.  That’s why in the realistic model of the cosmos, the Moon orbits around Earth and Earth orbits around the Sun.

Now the average Flat Earther believes that the Sun and Moon are much smaller – and presumably less massive – than Earth is.  (Well, they’re correct about the Moon, but definitely not about the Sun.)  Let’s pretend that they’re right in both cases.  If the Sun is still massive enough to bend the light from distant stars in exact accordance with Einstein’s General Theory of Relativity (and it is), and if Earth’s mass is much greater than the Sun’s mass (which, according to Flat Earth models, it must be), then surely Earth’s mass is enough to exert a gravitational influence on the objects that rest upon it, right? In fact, Earth’s gravity ought to be enough to squash it into a ball.

Or are Flat Earthers prepared to admit that their model is inconsistent in that it treats Earth as a physically special object, separate from and immune to the laws that govern the heavenly bodies?  No, even the most fact-averse Flat Earther, if he is intellectually honest (he isn’t), must concede that Earth has mass; ergo, it also exerts a gravitational tug.

Earth has gravity, anyway you look at it.  And in the Globe Earth model (i.e. the correct model) Earth is indeed spinning at a seemingly high rate of speed.  However, your speed with respect to the center of Earth diminishes as you move away from the equator.


The difference in speed between diverse latitudes gives rise to the Coriolis effect, which causes the rotation of tropical storms and ocean currents (but has no effect on the direction your toilet flushes!)  The easily measurable rotation of wind and water currents is just one more piece of evidence that we live on a spinning, ball-shaped Earth.  But we were talking about gravity.

Using Newton’s Law of Universal Gravitation (which will do in a pinch, although it is not as complete or exact as General Relativity), we can calculate that gravity exerts a “force” of about 9.8 newtons (about 2.2 pounds-force) on every kilogram of mass near Earth’s surface.  Is that enough force to keep Earth’s water from flying off into space, especially near the equator where it is moving the fastest?  Let’s find out.

The force required to keep something moving in a circular path is called centripetal force.  The faster an object is moving, or the more mass it has, or the tighter the circle you want to keep it moving in, the more force is required.  For example, imagine swinging a bowling ball in a horizontal circle on the end of a chain.  (No, I don’t know where one might find a bowling ball attached to a chain…just go with me on this one.)  It would take more force to swing a 12-pound ball then it would to swing an 8-pound ball.  It would also take more force to keep a ball swinging in a circle  5 feet across, compared to a circle 10 feet across.

Using the centripetal force formula, we can show that at the equator, it only takes 0.034 newtons (0.0076 pounds-force) of force to keep a kilogram of water moving in a circle with the same radius as Earth.  But remember, Earth’s gravity provides about 9.8 newtons of force per kilogram of matter, which means that each kilogram of water experiences way more than enough force from gravity to prevent it from flying off into space, even at the equator where it is spinning the fastest.  Q.E.D.

Now you might reasonably ask: if Earth’s rotation is causing me to move at hundreds of miles per hour, why don’t I feel like I’m moving that fast?  The answer to that question is two-fold:

  1. Compared to the size of Earth, even 1000 mph is not a very high speed, and
  2. Everything around you, including the air, is moving with you at the same speed.

See, it’s all relative.  We live on a ball-shaped Earth that spins once a day, moving around the Sun at more than 67,000 miles per hour (30 kilometers per second).  The Sun itself is whizzing through space at hundreds of kilometers per second, depending on which reference frame you choose.  But to us tiny humans held fast to Earth by gravity, none of this is readily apparent.  It’s only when we take the time to study the universe that we see the truth.  Humans have been studying the Universe and our place in it for centuries; its only the Flat Earthers, Creationists, and other reality-denying ideologues who seek to turn back the clock of scientific progress.

Creationist Meme Week, Part 7: Wrapping It All Up

Evolving Snowmen

I have run out of week before I ran out of Stupid Bad Creationist Memes, so I’ll shoehorn the last few memes into one post, if nobody minds. If you do mind, tough. Start your own snarky meme dissection blog.

Ahem, anyway. I wouldn’t expect a snowman to be particularly well-versed in evolution, and this meme does nothing to change my expectations. The speaking snowman (!) is making two critical mistakes. First: snowmen – even talking snowmen – are not people. A snowman being built up from individual flakes is not the same as humans evolving from single-celled organisms in the distant past. Therefore, you cannot use the absurdity of snowflake evolution to discredit biological evolution. Second: mutations occur by chance, but evolution does not. Evolution selects for beneficial mutations (where beneficial means bestowing a survival or reproductive advantage). It’s not that hard to get it right, unless you’re getting it wrong on purpose.

Creationism in Vietnam

Settle down, Batman! North Vietnam’s condition has nothing to do with its rejection of Creationism. I’m no expert on Vietnamese history, but I’ll bet there have been far more important events that molded North Vietnam. Why would Batman make a connection between Vietnam and Creationism anyway?

Perhaps because North Vietnam is an atheist state. Batman thinks that barring Creationism from public school science classes will make America an atheist state as well. Actually, accepting evolution does not go hand in hand with atheism. There are lots of theists who accept evolution (the Pope does), and I assume there are atheists who don’t believe in evolution. Granted, most atheists do accept evolution as a fact because they have no religious reason to reject it, but I won’t speak for all of them.

The United States is not an atheist nation, and preventing Creationism from being taught in public schools will not make us one. The United States is a secular nation, which means that we don’t favor one particular religion over another (at least in theory). And that has nothing to do with science class. We don’t teach Creationism in science class because Creationism isn’t scientific. If you combine science with religion, students will be confused about what is science and what isn’t.

Newton Vs Dawkins

Although this meme pits theist against atheist, it may as well be Creationist Vs Evolutionist, since Dawkins’s support for evolution is nearly as well-known as his atheism. I’m not sure what Isaque Newton is known for. I wonder if he’s any kin to Isaac Newton. They kind of look alike.

Whether we’re talking about Isaque or Isaac, there are a few issues that need to be addressed.

  1. I have no idea what revolve integral counting means. It sounds like it might be related to calculus (which Newton was instrumental in developing) but I’ve never heard that actual phrase before.
  2. Newton had nothing to do with the laws of thermodynamics. The memer is probably thinking of Newton’s Laws of Motion.
  3. I’m not sure how one opens a law. Perhaps with a law opener?
  4. Newton did not formulate the principle of conservation of energy. Although scientists in Newton’s time were aware of kinetic energy and were vaguely suspicious that something might be conserved, they did not know how to pull it all together. Scientists working in the mid-19th century created the first modern version of conservation of energy…more than a century after Newton’s death.

Newton did a lot of important things in his life, but you don’t help your argument by not knowing what they were. Now let’s talk about Richard Dawkins, the evil atheist and evolution proponent. It’s true that Dawkins did not study the nature of light, invent calculus (or revolve integral counting), open any major laws of physics, or become a father of modern astronomy. Then again, he didn’t have to do any of those things because they had all been done long before he was born. Are Dawkins’s opinions any less valid because he did not literally re-invent the wheel?

This meme is entirely pointless. The author wants to discredit Dawkins and all atheists (and perhaps evolution accepters) by showing that Dawkins’s list of accolades is shorter than Newton’s list, but he fails to explain why that’s relevant. Dawkins’s arguments should be judged on their own merits, and not because he hasn’t turned the scientific world upside down.

One more thing, memer: there are plenty of modern scientists who do believe in God and whose accomplishments are no more impressive than Richard Dawkins’s. Why don’t you single them out for an unfavorable comparison to Newton? Oh right, because it would reduce the strength of your argument to zero.

And so we come to the end of Creationist Meme Week. We have plenty of racist, sexist, and generally unpleasant memes that need discussing, so we’ll give the Creationists a break for a while.