Preface

“We've arranged a global civilization in which most crucial elements profoundly depend on science and technology. We have also arranged things so that almost no one understands science and technology. This is a prescription for disaster. We might get away with it for a while, but sooner or later this combustible mixture of ignorance and power is going to blow up in our faces.” 

- Carl Sagan

Now that Neil deGrasse Tyson has schooled rapper B.o.B. on how wrong it is to believe the earth is flat can we finally have an honest discussion about how we know it's moving? Unlike some of the evidence for sphericity the evidence for Earth's motion can't easily be captured in a cartoon or a photo. Just how certain are you of this basic fact about our world, and - more importantly - how do you know?

It seems like almost everyone nowadays has a strong opinion and a plethora of supporting "facts" for or against evolution, climate change, vaccines, genetically modified foods, and a host of other complex scientific questions. Heated debates occur regularly in Congress and around the water cooler at work or the dinner table at Thanksgiving. Nuance is avoided at all costs. Certainty reigns on all sides. Single data points or lines of evidence are offered up as "proof" - the "smoking gun" to silence our critics once and for all. We are confident that we are right and our critics are wrong. We are all graduates from the "University of Google." We research the issues ourselves. How can we possibly be wrong? In a collection of essays written by the British philosopher and mathematician Bertrand Russell in the early twentieth century, he noted that "the fundamental cause of the trouble is that in the modern world the stupid are cocksure while the intelligent are full of doubt" (Mortals and Others). In our Information Age this problem only seems to have gotten worse.

This politically charged public discourse on certain scientific issues stands in stark contrast to a general consensus on other similarly complex empirical questions. For example, according to a recent survey by the National Science Foundation, three quarters of Americans believe that the Earth revolves around the Sun. How hard would it be to convince those who are ignorant of this basic fact about our world? We experience direct evidence of geocentrism every day. It is embedded in our language (sunrise and sunset) and our tools (maps, globes, and star charts). And few of us can cite, much less have observed, any evidence whatsoever for heliocentrism. Science tell us that the Earth is moving at about 100,000 kilometers per hour around the Sun and spins on its axis at about 1,670 kilometers per hour at the equator. So we're not only moving, we're moving very fast!

Why do most of us accept this counterintuitive fact about our world? Why don't we have politically charged debates about it? Why are geocentrists (and Flat Earthers like B.o.B) viewed as fringe and nutty cranks while evolution, climate change, and vaccine "skeptics" are embraced by some celebrities, powerful politicians, taxi drivers, and janitors? How does a man named Oz become "one of American's most trusted docs" (according to NBC) while promoting untested weight loss supplements such as raspberry ketones and green coffee beans as a "miracle in a bottle" and a "magic weight-loss cure"? How did the "Food Babe" become a New York Times best-selling author and one of "the 30 most influential people on the internet" (according to Time Magazine) by promoting nutritional pseudoscience on her blog? Why does a major party presidential candidate and former First Lady of the United States believe (or pander to people who believe) that the government is withholding information from us about UFOs?

We have what neurologist Robert Burton has called a "certainty bias" - we "seek escape from ambiguity and indecision." We suppress our doubts. And we are all too willing to embrace strict ideologies and reject ambiguity and critical thinking when our most cherished beliefs are challenged. At the same time, many of us claim to love science - almost 20 million of us are fans of a popular Facebook page called "I fucking love science." But our "scienceyness" seldom leads to any serious questioning or inquiry, and we cling to "facts" that reinforce our preconceived ideas about the world without doing any actual investigation or critical thinking about them.

Of course, we can't all be scientists or personally investigate everything ourselves even if we were. We rely on trusted experts as well as our own education, experiences, and intuitions. But I want to challenge you to ignore the former and embrace the latter for just a moment. Let's apply some skepticism to heliocentrism.

Earthrise by NASA / Bill Anders, Public Domain.

i. Personal experience and common sense about a still Earth

Common sense, and direct observation, tells us that the Earth is flat, that the sun (like the moon) rotates around the Earth and that forces don’t operate at a distance. 

 - Barry Jones

Seeing is apparently not believing when it comes to heliocentrism. The only evidence most of us have seen ourselves actually supports geocentrism. I mean you actually can sit outside on a sunny day and watch the Sun move (slowly) across our sky! And on calm days there is no evidence of wind to indicate we're moving (like one experiences in a car with the windows down). A ball thrown straight up in the air lands back at its source. Sunbathers stand up occasionally and move their chairs to adjust to the movement of the sun across our sky. People sitting in the shade sometimes have to move to stay in the shade. Our direct experience tells us that the Earth is stationary and the Sun, Moon, stars and planets are moving around us.

To believe in heliocentrism is to suggest that our direct experience and basic intuitions about how the world works is an illusion. Moreover, geocentrism is a valid reference frame to describe the movement of the Sun across the daytime sky (sunrise and sunset), and geocentric star charts can help us locate stars in the night sky.

And unless we want to travel to another planet in our solar system, most of us will never need a heliocentric model (much less a galactic coordinate system to talk about the motion of galaxies). If you think about it, even a Flat Earth theory is sometimes a valid reference frame - for building houses for example.

Ptolemaic model by Bartolomeu Velho, Public Domain.

ii. Personal experience and common sense about an Earth that moves

“eppur si muove” - Galileo?

This chapter was left blank intentionally...you can use this time to Google "evidence for heliocentrism" if you want (or check my appendix).

And if you have had any personal experiences that confirm heliocentrism, I'd love to hear about it in the comments...

Sunset at Jockey's Ridge State Park by SkepticalPoet, Public Domain.

iii. Scientific models and evidence for an Earth that moves

"It is important to note that well-tested theories in the mature sciences are supported in general by a powerful web of interlocking evidence coming from a variety of sources."

 - Alan Sokal 

If you didn't already know something about this subject, you've undoubtedly attended the University of Google and graduated with a degree in astrophysics by now. So what's your "proof" - or "smoking gun" evidence for heliocentrism? Retrograde motion of the planets? The phases of Venus? The aberration of starlight? Stellar parallax? And more importantly, do you have any personal experience with collecting or analyzing any of this evidence? I doubt it.

Or perhaps you're frustrated that you couldn't really find a single line of "smoking gun" evidence that conclusively proves heliocentrism? But did you spend any time looking at non-parsimonious geocentric models with epicycles - for example, to explain the retrograde motion of planets or the phases of Venus?  Did you look at evidence for any models other than heliocentrism? Why not?

Did you look at any mathematical models at all? Because that's really what we're talking about here. And it wasn't until Kepler added elliptical orbits to the Copernican model that it better fit the best data we had at that time - Tycho Brahe's very detailed and comprehensive astronomical observations.
Galileo's discovery of moons orbiting Jupiter and the phases of Venus got him into some trouble with the Church on this issue, but it was really Kepler's elliptical orbits and his laws of planetary motion, which better predicted Brahe's data, that led to a simpler heliocentric model being widely regarded as true. Not until 1838 did we have the first successful measurements of stellar parallax (Friedrich Bessel), and by then almost every educated person was already convinced that heliocentrism was true. But let's face it: Most of us don't believe in heliocentrism because of the evidence - which very few of us have even examined.

Copernican model by Andreas Cellarius, Public Domain.

iv. Both/neither models are "true"

"in [general relativity], it is equally true to say that the Sun moves around the Earth as vice-versa.

 - Sean Carroll, physicist

Scientific models are "testable idea(s)… created by the human mind that tell a story about what happens in nature." Ideally - but perhaps not always - these models or theories make predictions that can be tested in the real world. The models are mathematical. Heliocentrism and general relativity are both mathematical models that have multiple lines of evidence to support them.

But general relativity (GR) forces us to abandon the notion of a stationary inertial frame of reference with the Sun at its center (heliocentrism) as being "true" in any complete sense. GR teaches us that geocentrism and heliocentrism are both valid - but not absolute - reference frames for describing the motion of the Earth, Sun, Moon, planets, and stars. And while both these models are unreasonably effective at describing our natural world, they are based on a provably partial and incomplete (mathematical) way of understanding.

The story of heliocentrism not only forces us to abandon the conceit that we are at the center of the universe, but it also reinforces the idea that our knowledge is tentative and subject to change based on new evidence. The goal in science is to falsify our ideas instead of prove them true: Try this approach the next time you consult Google.

GR by Mysid - Own work.

v. So what am I supposed to do?

"It seems to me what is called for is an exquisite balance between two conflicting needs: the most skeptical scrutiny of all hypotheses that are served up to us and at the same time a great openness to new ideas. Obviously those two modes of thought are in some tension. But if you are able to exercise only one of these modes, whichever one it is, you’re in deep trouble...Some ideas are better than others. The machinery for distinguishing them is an essential tool in dealing with the world and especially in dealing with the future. And it is precisely the mix of these two modes of thought that is central to the success of science."

 - Carl Sagan 

Ubi dubium ibi libertas! And first and foremost we should always be willing to apply some skepticism to our own ideas. After all, we just might be wrong! But skepticism, like most things, can also be taken too far. This exquisite balance requires a rigorous method for advancing our knowledge. Human reason is at the heart of that method, and empirical evidence is how we validate our ideas - or, more accurately, falsify them. However, openness to new ideas and experiences is what pushes the envelope on our understanding.

But all ideas should be subject to questioning, and genuine questioning shouldn't result in ridicule. As the old cliché goes, there are no stupid questions. However, our answers should be based on the evidence and subject to change in light of new evidence. We must also evaluate our information sources. In this regard, Robert Harris' Evaluating Internet Research Sources is a classic for our information age. And Carl Sagan's Baloney Detection Kit is still a relevant guide to reasoning through these questions.

In the end, the process we use to determine the facts and evaluate the evidence is much more important than just knowing (or being able to Google) the facts and the evidence.

James Randi: James Randi Educational Foundation.

Prologue

"There is talk of a new astrologer who wants to prove that the earth moves and goes around instead of the sky, the sun, the moon, just as if somebody were moving in a carriage or ship might hold that he was sitting still and at rest while the earth and the trees walked and moved. But that is how things are nowadays: when a man wishes to be clever he must . . . invent something special, and the way he does it must needs be the best! The fool wants to turn the whole art of astronomy upside-down. However, as Holy Scripture tells us, so did Joshua bid the sun to stand still and not the earth." 

 - Martin Luther, 1539  

Heliocentrism - like many of the ideas behind human progress - was opposed by religious fundamentalists of the time. But despite Luther's concern in 1539, Aristarchus of Samos (310 - 230 BCE) had first proposed a heliocentric model and suspected stars were other suns and very far away. He also appears to have recognized that this fact would explain why there was no observable stellar parallax (before the invention of the telescope). Pliny the Elder and Seneca also referred to retrograde motion of the planets as an apparent (and not real) phenomenon, but better theories and evidence for this speculative, revolutionary, and counterintuitive idea would have to wait for Galileo and the invention of the telescope and Luther's "new astrologer" - as well as Brahe, Newton, Kepler, and others.

There are many reasons why our society is so anti-science today and why some claim that we are living in an "Age of Magic," but religious fundamentalism continues to be a factor in debates about evolution, climate change, women's health care, and many other issue of public interest.  Chris Mooney, reporting on a paper published in the journal Social Forces in 2015 by sociologist Gordon Gauchat of the University of Wisconsin-Milwaukee, notes that "being a biblical literalist — endorsing the statement, 'The Bible is the actual word of God and is to be taken literally, word for word' — was a much bigger factor than liberalism or conservatism in explaining why some people disagreed with the use of science in 'concrete government policy decisions,' and also why they were against federal science funding."

When science is discounted based on ideology, we all lose. But when science is accepted based on authority or tradition, instead of critical thinking and evidence, we also lose. We must be both skeptical and open to new ideas and experiences to make progress. And as Richard Feynman said, "The first principle is that you must not fool yourself – and you are the easiest person to fool."

So...with that said, how would you prove heliocentrism to a skeptic?

And no, this is not an open (or memorized) book test...

Luther Bible, 1534 by Torsten Schleese, Public Domain.