But it moves! How we know the Earth rotates.

“I feel the earth move under my feet
I feel the sky tumbling down
I feel my heart start to trembling
Whenever you’re around” -Carole King

I had so much fun earlier this week telling you about how we know that the heliocentric model is better than the geocentric one, that I thought I’d go a little farther down that rabbit-hole. You see, the first astronomical thing that any living creature likely notices is that, as seen from Earth, the Sun rises in the East each day and sets in the West.

(I don’t want to hear it from you kids at the poles, either!)

The Sun, as it were, appears to move in half of a great circle throughout the sky. What’s more, is that if you look up at night, you’ll find that the night sky appears to move along a similar path, like the entire heavens rotates.

Why does this happen?

It turns out that there are two possible explanations that — at first glance — are equally good.

First off, the Earth could be stationary, and everything in the heavens, including the Sun, stars, Moon, and planets, could be revolving around it, once per day.

The other option, though, is that these objects in the sky don’t move so rapidly, around the Earth, once per day. Rather than having everything orbit the Earth, the Earth could simply be rotating.

How would we know? What test could you perform on Earth to tell these two cases apart?

You’d hope that there’d be some easy way to see it from looking at the atmosphere, but when things with atmospheres rotate at constant rates, their atmospheres rotate at constant rates with them. It turns out that it wasn’t until the 1850s that we figured out a simple, straightforward method to test it. The key device, believe it or not, is a simple pendulum.

If you have a perfect pendulum, it will simply swing back-and-forth in a straight line forever, until something like air resistance slows it down to a full stop. For a very long, very heavy pendulum, this could take days.

But if you have a perfect pendulum that lives on, say, a rotating planet, something very, very interesting happens.

Image credit: Cleon Teunissen.

The pendulum, swinging back and forth, will be affected by the Earth’s rotation! The effect won’t be visible in just a few swings; in fact, if you were at 30 degrees North latitude (as the diagram above shows), it would take two full days for the pendulum to spin around once, or five minutes for it to rotate a mere one degree.

So what happens if you do this?

Well, the first time this was demonstrated was in 1851, by the Frenchman Leon Foucault, and the device is now known as the Foucault Pendulum. In fact, there are many of these all over the world, including the world’s heaviest one right by me in Portland, OR. The results are almost immediately striking.

The simplest way to do it is to build a long pendulum with a heavy mass, and tie it off at a small but significant (5-10 degree) angle. Leave it overnight. In the morning, come in and mark its position, and then burn the string you used to tie it off.

Why burn it? Because this way, you won’t accidentally introduce any angular momentum; the pendulum will simply swing back-and-forth in a straight line.

And then come back to it. Or, if you’ve got some time, just watch it go. Know what you’ll see?

The pendulum indeed rotates at the exact rate you’d expect if the Earth rotated once per day, regardless of your latitude! Not only that, but there are some pendula out there that are situated with a spike on their bottoms and a sand-pit beneath them to draw in.

Over the course of a day, they trace out a very telling pattern.

Image credit: Cleon again. Note, this cuspy, updated image replaces an old one, which is less correct because of the rounded edges.

This is firsthand, easy proof that the Earth, indeed, moves! Although we already knew it via other means, this is an experiment that anyone can do with a little effort, and many people all over the world already have!

In fact, some people even videotape it…

And that’s how you know the Earth moves, and how you can demonstrate to anyone who thinks otherwise what science actually has to say!

Comments

  1. #1 timberwoof
    September 17, 2010

    Excellent posts. (I enjoyed the ones on heliocentric and terracentric models. Next, how is the absolute size of the solar system determined?)

    I’m not clear on the relationship between the latitude of the pendulum and how long it takes for its rotation to become apparent. I get that a pendulum at the North or South pole would take 24 hours to make a full circle (or 12, depending on whether you count swings one or two at a time). What would a pendulum at the equator do? How about at 30°, 45°, 60° latitude?

    I’m not happy with he first animation: It looks like the pendulum stays in the same direction when it’s on my side of the sphere and reversing on the back side. That process should be evenly distributed all around the circle, right? Is that some odd trick of perspective?

  2. #2 Ktesibios
    September 17, 2010

    The relationship between latitude and the period of precession of the pendulum is:
    period=24/sin(latitude) (answer is in hours). You’ll notice that for the poles (latitude= +- 90 degrees, the period is 24 hours, while at the equator (latitude= 0) the period is infinite, i.e., at the equator a Foucault pendulum doesn’t precess at all.

    Check out Amir D. Aczel’s book Pendulum: Leon Foucault and the Triumph of Science,. Aczel gives two derivations of the sine law in an appendix.

  3. #3 P Smith
    September 17, 2010

    James Burke mentioned Foucault in one of his two major TV series (I believe it was “The Day The Universe Changed”) when he was discussing Gallileo, Copernicus and/or clocks. Foucault’s use of the pendulum is as simple and as inspired a way of proving the Earth is round as was Ptolemy’s use of a stick in Egypt.

    Unfortunately, the ignorant and short sighted cannot grap the concept for the same reason they can’t graps the big bang, evolution and abiogenesis: they lack the intellectual capacity to see past their short 70 year lifetimes.

  4. #4 jcmartz.myopenid.com
    September 17, 2010
  5. #5 IBY
    September 17, 2010

    Wait, how is the pendulum kept moving at an indefinite amount of time?

  6. #6 Jonathan Lee
    September 18, 2010

    In principle, this is a really good demonstration. The problem is that the publicly accessible ones would all be too affected by vibrations from external traffic and people walking around.

    To keep them going indefinitely for display, they have electromagnetic kickers built into them. Foucault’s experiment was still good proof, but you don’t see the same experiment in museums today.

  7. #7 Stefanus
    September 18, 2010

    Great poetry you’ve got up there
    copied to be posted at Facebook

  8. #8 Dale Sheldon-Hess
    September 18, 2010

    “Next, how is the absolute size of the solar system determined?”

    Oh, yes, great idea, since I believe part of the answer will be very relevant in about 8 or 9 months!

    (I’d’ve sworn it’d already been discussed here, but can’t seem to find any evidence of that fact. I must’ve read about it somewhere else recently?)

  9. #9 csrster
    September 18, 2010

    The movement of the Foucault pendulum can also be described (from the frame of the rotating Earth) using the concept of Coriolis force. One other clearly measurable consequence of Coriolis force due to the rotation of the Earth is the deviation of artillery shells fired in a North-South direction.

  10. #10 Puddock
    September 18, 2010

    Thanks for this – it’s just the kind of thing I should have known but didn’t!

  11. #11 Anasva
    September 18, 2010

    I thought I should share my confusion regarding the finer details of this. I got confused about what happens to the hook & string from which the pendulum is hanging. The hook rotates with the earth. And then shouldn’t it also take the pendulum along with it? But then I realized that the string has 360-degree rotational freedom around the hook. And because gravitational force is always pointing downwards, pendulum remains in the plane containing the center of the circle & the current position of the pendulum. On these lines, the string would get twisted over time, right? And when it twists too much, it will exert angular momentum over the pendulum, right?

    So, in summary, there are some finer aspects of how to hang this pendulum.

  12. #12 FarmerTodd
    September 18, 2010

    IBY, put simply, the pendulum isn’t really moving as much as you’d think: the floor and earth and everything under the pendulum is. It gets its energy from the motion and gravitational pull of the earth.

  13. #13 Michel
    September 18, 2010

    This is fun.
    An “how to” to making your own Foucault pendulum:
    http://www.galeschools.com/sci_try/foucault.htm

    Now I´m going to need some space.

  14. #14 rpenner
    September 18, 2010

    But… that takes too long.

    Can’t you just read the rotation directly with a laser (fiber optic) gyroscope?

  15. #15 Caleb Fennell
    September 18, 2010

    How cool. I didn’t know we had teh world’s heaviest Foucault’s Pendulum in Portland! Well then, off I go to the Oregon Convention Center!

  16. #16 g724
    September 19, 2010

    There are active geocentrists afoot, and they are having a conference.

    http://www.talk2action.org/story/2010/9/12/18017/5649

    “Galileo Was Wrong, The Church Was Right – that’s the sensationalistic heading for the 1st Annual Catholic Conference on Geocentrism….”

    The author of the article is a subject-matter expert on religious extremism in America, whose research is taken seriously in high places. He is also the one who exposed the video of Sarah Palin at an extremist religious service that included “casting out of demons” and praise for actual witch-hunting: when this came to light it cost McCain/Palin points in the opinion polls (and thus presumably at the voting booth).

    BTW, the conference in question is not supported by the Vatican, it appears to be on the fringes of Catholicism. In the same way that dominionism was once on the fringes of Protestantism.

    We need to know about this stuff and we need to fight it ferociously.

    Keyword search “dominionism” and read up. This is not snark or sarcasm, this is a five-alarm fire that has to be fought.

  17. #17 MadScientist
    September 19, 2010

    @IBY: For as long as I can remember, we cheat. The plumb is usually a ferromagnetic material and there is a large electromagnet directly below the pendulum’s pivot point. Now you just need a very simple electronic circuit whose timing can be finely adjusted to coincide with the pendulum’s period; that timer triggers a brief pulse of current as the plumb approaches the electromagnet. Some massive plumbs do without cheating; they rely on the mass to help compensate for loss of momentum through air friction, but they do need to be given a push at least once every few days whereas the cheaters have pendula which run for much longer periods (until something goes wrong – power goes out, electronics fail, the wire suspending the plumb snaps, or someone decides to stop the pendulum).

  18. #18 MadScientist
    September 19, 2010

    @Anasva: Yes, the wire twists and this torsion in turn twists the pendulum (but does not affect the direction of the swing). That torsion would also ensure that the plumb does not appear to twist. So, if you painted a stripe on the plumb and set the pendulum swinging that stripe would appear to face the same direction all the time – for example, if you put a peephole in a wall at some distance, you will always see the stripe facing you when the pendulum is in the lowest position in its swing even though the pendulum itself appears to swing in a different direction.

  19. #19 MadScientist
    September 19, 2010

    Oh – I forgot to mention – that short loop shows a pendulum which is wobbling out of the plane. The blue part (if you swing the pendulum correctly) should simply be an arc.

  20. #20 Joffemannen
    September 20, 2010

    Hmm, with the earth in the center, and the known distance to the furthermost stars, and the earth stationary, those distant stars and galaxies travel so fast (some 200 billion light years in 12 hours) that they surely induce some force on a pendulum?

  21. #21 markogts
    September 20, 2010

    Please don’t misunderstand my comment: I do agree with the HC model and I know about the Coriolis & Focault effects. However, with Mach’s principle, we could still say the Earth is static while the stars spinning around us create a gravity effect that has the very same effect of the Earth rotation.

    It’s all a matter of reference frames: there is no “correct” one, there is only that one that simplifies requested hypothesis, approximations and calculations. And this one is, most often, the HC model.

  22. #22 Mu
    September 20, 2010

    The pendulum indeed rotates at the exact rate you’d expect if the Earth rotated once per day, regardless of your latitude! and if you were at 30 degrees North latitude (as the diagram above shows), it would take two full days seem to contradict each other.

  23. #23 MiLee
    September 27, 2010

    Markogts is correct – there is no “correct” reference frame. HC or GC are equally valid frames – sorry to say. While a nice blog entry, Foucault’s pendulum does not “prove” one frame over another – in fact there is absolutley no proof one way or the other. That is the whole point of the GC crowd –

  24. Wow this is a great post!

    To think Galileo almost lost his life for his work on the heliocentric nature of the universe.

    Markogts makes a great point with respect to “correct/non-correct” reference frame, although I have to say I tend to lean towards the HC model. Reason being there just is too much compelling evidence for me to ignore.

  25. Wow this is a great post!

    To think Galileo almost lost his life for his work on the heliocentric nature of the universe.

    Markogts makes a great point with respect to “correct/non-correct” reference frame, although I have to say I tend to lean towards the HC model. Reason being there just is too much compelling evidence for me to ignore.

  26. Wow this is a great post!

    To think Galileo almost lost his life for his work on the heliocentric nature of the universe.

    Markogts makes a great point with respect to “correct/non-correct” reference frame, although I have to say I tend to lean towards the HC model. Reason being there just is too much compelling evidence for me to ignore.

  27. Wow this is a great post!

    To think Galileo almost lost his life for his work on the heliocentric nature of the universe.

    Markogts makes a great point with respect to “correct/non-correct” reference frame, although I have to say I tend to lean towards the HC model. Reason being there just is too much compelling evidence for me to ignore.

  28. Wow this is a great post!

    To think Galileo almost lost his life for his work on the heliocentric nature of the universe.

    Markogts makes a great point with respect to “correct/non-correct” reference frame, although I have to say I tend to lean towards the HC model. Reason being there just is too much compelling evidence for me to ignore.

  29. Wow this is a great post!

    To think Galileo almost lost his life for his work on the heliocentric nature of the universe. I have been encouraging my pupils to explore science fair projects that explore astronomy and the HC and GC models.

    Two of my pupils attend strict catholic schools and this has raised some debate in their household. Still their parents acknowledge the overwhelming evidence for the HC model. It has really been a great conversation provoker.

    Markogts makes a great point with respect to “correct/non-correct” reference frame, although I have to say I tend to lean towards the HC model. Reason being there just is too much compelling evidence for me to ignore.

  30. Wow this is a great post!

    To think Galileo almost lost his life for his work on the heliocentric nature of the universe. I have been encouraging my pupils to explore science fair projects that explore astronomy and the HC and GC models.

    Two of my pupils attend strict catholic schools and this has raised some debate in their household. Still their parents acknowledge the overwhelming evidence for the HC model. It has really been a great conversation provoker.

    Markogts makes a great point with respect to “correct/non-correct” reference frame, although I have to say I tend to lean towards the HC model. Reason being there just is too much compelling evidence for me to ignore.

  31. Wow this is a great post!

    To think Galileo almost lost his life for his work on the heliocentric nature of the universe. I have been encouraging my pupils to explore science fair projects that explore astronomy and the HC and GC models.

    Two of my pupils attend strict catholic schools and this has raised some debate in their household. Still their parents acknowledge the overwhelming evidence for the HC model. It has really been a great conversation provoker.

    Markogts makes a great point with respect to “correct/non-correct” reference frame, although I have to say I tend to lean towards the HC model. Reason being there just is too much compelling evidence for me to ignore.

  32. Wow this is a great post!

    To think Galileo almost lost his life for his work on the heliocentric nature of the universe. I have been encouraging my pupils to explore science fair projects that explore astronomy and the HC and GC models.

    Two of my pupils attend strict catholic schools and this has raised some debate in their household. Still their parents acknowledge the overwhelming evidence for the HC model. It has really been a great conversation provoker.

    Markogts makes a great point with respect to “correct/non-correct” reference frame, although I have to say I tend to lean towards the HC model. Reason being there just is too much compelling evidence for me to ignore.

  33. Wow this is a great post!

    To think Galileo almost lost his life for his work on the heliocentric nature of the universe. I have been encouraging my pupils to explore science fair projects that explore astronomy and the HC and GC models.

    Two of my pupils attend strict catholic schools and this has raised some debate in their household. Still their parents acknowledge the overwhelming evidence for the HC model. It has really been a great conversation provoker.

    Markogts makes a great point with respect to “correct/non-correct” reference frame, although I have to say I tend to lean towards the HC model. Reason being there just is too much compelling evidence for me to ignore.

  34. #34 AMDG
    September 28, 2010

    It turns out that there are two possible explanations that — at first glance — are equally good. < \i>

    second glance, too….. every glance.

    If you have a perfect pendulum, it will simply swing back-and-forth in a straight line forever, until something like air resistance slows it down to a full stop. For a very long, very heavy pendulum, this could take days. < \i>

    Glosses over important practical details…. Most FP require additional energy to maintain the plane of motion… like electromagnet pulses. This pumps energy into the FP which may affect the normal response.
    Some FP won’t produce any planar rotation…. or do, but in the opposite sense of the Earth’s rotation!
    Most won’t start rotating anywhere if in an East-West vertical plane, but will if in a N-S plane.

    The pendulum, swinging back and forth, will be affected by the Earth’s rotation! < \i>

    How does the Earth’s rotation affect the FP?… there’s no physical contact, except through the wire.
    How does the FP ‘know’ that it is above a rotating object and should start rotating?
    Where’s the cause for the observed effect?

    The pendulum indeed rotates at the exact rate you’d expect if the Earth rotated once per day, regardless of your latitude! < \i>

    We expect a 24 hour rotation, but that only happens at the poles … there’s no rotation at the equator. How is that independent of latitude??

    This is firsthand, easy proof that the Earth, indeed, moves! < \i>

    Only if you ignore other logical possibilities.
    If absolute rotation were detectable, then relativity of rotation – expressed in Mach’s principle – would be refuted.
    But Mach’s principle was the key to the final version of the GR field equations. If the Earth does rotate absolutely, then the GR model collapses… Pretty serious implied claim for an astrophysicist….

    Although we already knew it via other means, < \i>

    ….What are the other experimental proofs?

    And that’s how you know the Earth moves, and how you can demonstrate to anyone who thinks otherwise what science actually has to say!< \i>

    Great graphics, as usual. But short on logic… as usual. Aristotle 101.
    Wiki says the FP is sensing the stars motion…. or lack thereof. This is an even greater leap of faith – how does the FP know the stars are moving, or not?
    This reasoning allows one to also say that if the stars are moving… as actually observed …. then the FP is moving with the stars….. and the Earth is not! In other words – proves nothing.

    The model of an aether wind circulating every sidereal day on a static earth solves all the issues above, including the practical anomalies. This aether wind was detected by Michelson-Gale in 1925 but reported as proof of the Earth’s rotation.
    The difference in timing of E-W radio signals also supports the aether wind model – a natural aether flow, not caused by dragging by the Earth’s spin.
    3
    Yes, what a burden of ignorance – using the scientific method of testing, Popper’s logic and reasoning – which prevents acceptance of scientific speculation masquerading as fact.
    5
    Ah, an inquisitive mind.
    16
    Oh dear… why such virulence? What about freedom of speech??? Are these people terrorists?
    All we need to do to silence them is use the scientific method and reasoning to show that the Earth moves.
    The problem is finding such evidence…. here, or anywhere.
    20
    Yes, but how, without an aether?
    21
    But we do misunderstand ….. why agree with the HC model if it’s not testable?
    Simplification of hypothesis, approximations and calculations is personal subjective aesthetics…. Occam’s Razor is not part of the scientific method.
    22
    They do contradict.
    23
    Agreed…. but why ‘sorry to say’? Is there some kind of bet going on….. or an ego thing?
    24
    And the complelling evidence is….??
    25
    Show your students and their parents this post.

    AMDG

  35. #35 Elmer PhuD
    September 28, 2010

    AMDG,
    You obfuscate like a coward.
    I dare you to answer in one word this simple question:
    does the earth move?

    Do not blow smoke, do not cite “research”, do not impugn others. Just answer the question; everyone else can.
    In one word: does the earth move?

  36. #36 Tim DeLaney
    September 30, 2010

    AMDG’s post reminds me strongly of a poster found on Talk.Origins (newsgroup) who goes by the name Anthony Pagano. Are you two folks the same?

    As we can see, the GC crowd has ways to ‘explain’ FC and Coriolis effects. But there is one evidence that, IMHO, cannot be satisfactorily explained by GC. Earth is not a sphere, but (approximately) an oblate spheroid. This is a matter of comparatively simple and reproducible measurement. Moreover, the plane of its putative rotation exactly corresponds to the plane of its bulge. We can see this bulge on many other objects in our solar system, and it always corresponds with their respective (and observable) planes of rotation.

    Nobody has ever proposed a mechanism that could explain the Earth’s shape except that it rotates on its axis.

  37. #37 David Marjanović
    September 30, 2010

    If absolute rotation were detectable, then relativity of rotation – expressed in Mach’s principle – would be refuted.
    But Mach’s principle was the key to the final version of the GR field equations. If the Earth does rotate absolutely, then the GR model collapses… Pretty serious implied claim for an astrophysicist….

    Have I got news for you…

    Rotation is absolute. Uniform motion — straight, no change in direction, no change in speed — is relative, but acceleration is not, and rotation is a form of acceleration, because it’s a change of the velocity vector.

    You’ve misunderstood general relativity. Try again.

    Occam’s Razor is not part of the scientific method.

    :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D :-D

    Falsification and parsimony are the two parts of the scientific method.

    When 2 or more falsifiable but unfalsified hypotheses explain the data equally well, those of them that require the fewest extra assumptions must be preferred. What else would you do? Prefer the hypotheses with the most extra assumptions? Every event caused by its very own law of physics?

    …Are these rhetorical questions? :-)

  38. #38 AMDG
    October 1, 2010

    68 The Earth has two aether rings – for the Sun and Moon. The planets are in secondary aether rings surrounding the Sun. Their moons are in tertiary aether rings around the planets … see the neo-Tychonian hierarchy model.
    You could have saved a lot of words by just saying “magic”. If everything moves like it does because the aether currents send it where they flow, and they can basically flow anywhere … where’s the predictive power?

    Magic is the word for Newtonian gravity – objects fall to the ground with nothing between.. spooky AAAD, said big Al.
    The cosmic aether currents/rings are seen to be quite stable, so we predict that the celestial objects will continue on the orbits we see now, like balls floating in a river.
    There are innumerable weather sensors around the world, in space and in the oceans. Yet the specific local weather is only known a few days in advance.. WHERE’S THE PREDICTIVE POWER?
    The implication that knowledge is useless unles it has predictive power is tunnel vision. What about truth for its own sake?
    Is it the goal of science to know how everything works? Or is there a limit to such knowledge by humans?

    LeSage particles use the ideal-gas paradigm – there is no drag/friction in matter interaction , only absorption – which produces the inverse square law locally.
    No drag/friction, only absorption? First, that is not an ideal gas (particles elastically scattering off whatever you put into it). Second, you still get drag in your model due to velocity distribution in front of an object being different from the velocity distribution behind your object.

    First- The LeSage particles convert to photons(heat) within mass … so an ideal gas, with energy conversion.
    Second- A log is floating downstream, moving at the same speed as the water touching it. Where’s the drag??

    69 ….. The Casimir effect was predicted by quantum physics (more precisely: Heisenberg’s uncertainty relation) before it was observed, and the observation fits the prediction.

    Aether pressure also explains the Casimir effect, which supports both theories.

    The exact same holds for your misunderstanding of the tunnel effect. The light in that experiment did not have 310 c, it had no velocity at all, because it never was between the ends of the tunnel.
    So the speed of light wasn’t 310 times c(as reported), it was zero! Thanks for clearing that up….

    …… There is, ultimately, no such thing as mechanics. There are no forces in this universe that do not reduce to electromagnetism, the weak nuclear force, the strong nuclear force, gravity, or the expansion of the universe.
    So you reject the electroweak unification…. why?
    Tell us more about the fifth force of BB expansion… what is the source? How is it measured?

    Parsimony, man. We don’t need an aether. You, on the other hand, haven’t even explained the experiments by Michaelson and Morley yet!
    Why no discussion of M&MX? Parsimony, man! Nobody asked us….. because it’s pretty obvious.
    With an Earth at rest and a weak aether flow that only the Mic-Gale-1925 exp. could detect, what fringe shift result would you expect?
    Null – right!

    Oh, and, just to repeat what so many people have already said, uniform motion is relative, but acceleration is not, and rotation is a form of acceleration because it’s a change in the velocity vector. According to relativity, you cannot tell how big the vector is, but you can tell when it changes!
    Relativity of motion means that Va,b(t) = – Vb,a(t) for any frames a,b.
    The rate of change of this equation gives the acceleration: Aa,b(t) = – Ab,a(t)
    So velocity and acceleration are relative…. in relativity theory

  39. #39 Elmer PhuD
    October 1, 2010

    AMDG,
    Answer the simple question, coward.
    In one word: does the earth move?

  40. #40 Elmer PhuD
    October 2, 2010

    AMDG,
    Ah sorry, I see you did answer, but in the wrong thread, and lumped in with other piffle.

    In one word: does the earth move?
    According to the scientific method and logic, no. But this is a question you should ask yourself, using the same epistemics, not us.

    There it is, unvarnished medieval arrogance: as special Jesus headquarters, AMDG’s planet doesn’t move. Nor, I presume, do the turtles under it.

    That’s all I wanted. Thanks for admitting it at least, even though you felt compelled to wrap it in more commentary.

    But wait: I clearly asked AMDG alone. So who is “us?” Is AMDG plural?
    Anonymity is the right of an individual, not of an organization too cowardly to own its propaganda.

    I’ll not respond further, but I urge you sincerely: take as many Jesus Points as you want on the way out, but just stop, please. You are naked here, and pulling more rhetorical underpants over your head as an Epistemic Helmet will not make it better. The fun’s over; practice letting go and walk away.

  41. #41 Sue Church
    October 3, 2010

    Galileo was not the first to propose a Sun-centered system. That was a Catholic priest from Poland named Nicolaus Copernicus. He was never punished for his theory.

    Several comments here mention people wondering about the Earth-centered theory, but being swayed to a Sun-centered one by “impressive” and “overwhelming” evidence. However no particular evidence is cited.

    The Astronomy professor who taught us at The New School in New York would always post two diagrams side by side and allow us to choose. He had his degree from Harvard in 1925 and was on the Editorial Board at Scientific American. He told us, “if anyone insists our system is Heliocentric, ask them to prove it.”

    Some folks simply like to politicize Science. This is to its great detriment.

  42. #42 Sue Church
    October 3, 2010

    Galileo was not the first to propose a Sun-centered system. That was a Catholic priest from Poland named Nicolaus Copernicus. He was never punished for his theory.

    Several comments here mention people wondering about the Earth-centered theory, but being swayed to a Sun-centered one by “impressive” and “overwhelming” evidence. However, no particular evidence is cited.

    The Astronomy professor who taught us at The New School in New York would always post two diagrams side by side and allow us to choose. He had his degree from Harvard in 1925 and was on the Editorial Board at Scientific American. He told us, “if anyone insists our system is Heliocentric, ask them to prove it.”

    Some folks simply like to politicize Science. This is to its great detriment.

  43. #43 Elmer PhuD
    October 4, 2010

    Sue’s comment is… interesting… enough that I’ll make a brief reprise.

    Let’s assume that Sue Church is a real person, joining us for the first time, and not a sockpuppet. Welcome Sue!

    Let’s assume that Sue has read the evidence cited by numerous commenters here — including this very blog post by Dr. Siegel — and, quite ingenuously, failed to recognize it, mistaking it for, say, a turnip.

    Let’s assume that, while making an Argument From Authority (ingenuously of course!),
    Sue is able to remember exactly when and where her beloved professor got his degree and which editorial boards he sat on, but sadly unable to remember his name.

    Even with those assumptions, I think Sue would have to agree that her credibility is an unlucky casualty of timing, doomed by the stench of dishonesty left by Liars for Jesus who, coincidentally, share her position.

    Sorry Sue; it’s a shame people politicize science.

  44. #44 Colter Siebert
    November 13, 2011

    Everyone,

    In the Michelson-Morley Experiment(http://scienceworld.wolfram.com/physics/Michelson-MorleyExperiment.html), it was proven that light is constant in all directions at any speed. But, if we think that is true, we would be saying that the simple math of net forces is untrue, because if the earth is moving against the way the light is traveling, the light would move at a slower velocity than if it was traveling with it. This, in turn, proves that since light is the same in all directions, that the earth must be hanging still in the universe(because of the net forces), which then shows that, since we can observe the sun and other planets and stars moving above us, they must be orbiting around the earth, which means the earth is the center of the universe.

  45. #45 islam
    egypt
    October 16, 2012

    I read a book and the reader proofed that earth don’t spin but the sun and moon is rotating around it and the proofes was from quran and um muslim so I said I have 2 search the net to see other proofes that tells that the earth rotates around the sun then I get nothing except a stupid penedulm so now I just believes in what god said in quran… Can any body answer me if the earth spins how can we see the stars constant and how can an air flight takes the same duration for leaving and coming back??

  46. #46 DavidL
    October 17, 2012

    Islam, I will assume for now that this is a genuine question and it is only the penedulm that is stupid.

    “how can an air flight takes the same duration for leaving and coming back??”

    Simple answer, because the air through which the airliner flies is spinning too.

    More complicated answer, it does not. In the Northern Hemisphere at temperate latitudes, winds blow predominantly from west to east, so east-west flights usually take longer. The winds blow west to east because the earth is spinning, so the surface of the earth at the equator is moving faster than the surface of the earth in Europe and America. As air heated at the equator it rises and moves north, and as it is still traveling at about the same speed as the earth’s surface at the equator, it is traveling west to east with respect to the ground now under it.

  47. #47 OKThen
    Child's Museum (Cairo)
    October 17, 2012

    Islam
    If you are in Egypt, visit the Child Museum in Cairo.
    It is located at: 34, Abo Bakr EL Seddik Street Heliopolis, Cairo, Egypt
    It “Looks at the history of science in Egypt, through both a static hands on exhibition that looks at stars, ships, astrolabes, telescopes, airplanes and space travel, and also an immersive 4D experience dome show, in which the pioneers of Egypt appear to tell the history of science and encourage visitors to participate in the future.”

    The Child Museum (Cairo) has “specialized working groups of Egyptian and world experts in fields of science, technology, physics, history, geography, civilization, geology, architecture, engineering and arts of exhibitions have all exerted concerted efforts to create a distinguished and unique museum for the Egyptian child.”

    Remember the holy books of the world (the Koran, Old Testament, New Testament, Bhagavad Gita, Upanishads, Five Classics, Talmud, Tao-te-ching, Veda and others) are not science books.

    Experimental science in the modern sense is only about 400 years old. Whereas the Quran is 1600 years old.

    Visit the Child’s Museum in Cairo, I’m sure you’ll find the exhibit fascinating and learn a lot about astronomy and other sciences. Like all science museums, I’m sure it will be very interesting and educational for adults also. It sounds like a greate museum.

  48. #48 Wow
    October 17, 2012

    “I read a book and the reader proofed that earth don’t spin but the sun and moon is rotating around it”

    Except it didn’t. It gave a plausible explanation whilst not actually testing (the old and original meaning of the word “proof”, which makes the homily “the exception proves the rule” sensible, where the modern usage makes it nonsense) it for proof.

    Shooting a long range artillery shell produces a different track on whether you shoot directly west, directly east, north or south. And the differences are EXACTLY what are the result of a rotating earth.

    “Can any body answer me if the earth spins how can we see the stars constant”

    Go on a roundabout. Spin round on it. Enjoy the movement. Now explain how you can see the rest of the playground contents as constant.

    “how can an air flight takes the same duration for leaving and coming back??”

    It doesn’t.

  49. #49 Wow
    October 17, 2012

    “But, if we think that is true, we would be saying that the simple math of net forces is untrue”

    And that led to Special Relativity.

    “that the earth must be hanging still in the universe(because of the net forces)”

    Nope, we have a non-net force. Our gravitational attraction to the sun is not zero and is not balanced out by objects elsewhere.

  50. #50 EAO
    Earth that doesn't spin
    October 23, 2012

    If the earth spins and its not perfectly flat (mountains and places below sea level), wouldn’t there be some kind of wobble created or a vibration? I know with mechanical equipment that spins, any defect or out of true-ness causes imbalance, i think the earth would be effected the same way, especially the speed at which the earth rotates. Thanks

  51. #51 CB
    October 23, 2012

    There’s a reason Einstein’s famous “man in a rocket-propelled trunk” experiment has a closed trunk. This is because, while the General Principle of Relativity says acceleration and gravitation as the same, and to always craft the laws of the universe as if your reference frame was stationary, this does not mean that there is never a reason to prefer one explanation over another.

    For example, it is pretty trivial to conclude that the experience of gravity on the surface of the earth is caused by the mass-energy of our planet exerting gravity, and not constant uniform outward acceleration of the planet’s surface.

    Similarly, if the man in the trunk looked out and saw that there was no mass around him, he was in the middle of empty space, and there was a rocket on his trunk, he would conclude — based on the laws of General Relativity — that the apparent gravitational field he was in was caused by that rocket.

    One could formulate the universe as if the stars were apparently moving at many times the speed of light via a coordinate transform from the straightforward explanation. But to prefer this system, one would have to explain where the source of gravity to perform this feat is. Clearly it’s not the earth. This makes the mysteries of dark matter and dark energy look like trifles.

    “Relativity” is not a “Get out of making sense free” card.

  52. #52 CB
    October 23, 2012

    I meant “the General Principle of Relativity says acceleration and gravitation as the same, and *that you can* always craft the laws of the universe as if your reference frame was stationary”

  53. #53 David L
    October 23, 2012

    @EAO

    In mechanical equipment it is the imbalance around its spin axis which causes the “wobble”. Any solid object in space can only spin around its centre of gravity, so it is in balance

  54. #54 Ijlal Haider
    Islamabad,Pakistan
    December 26, 2012

    I want to know the reason that “Why does Earth rotates about own Axis.”
    (plz give answer other than the nebula story)

  55. #55 Wow
    December 27, 2012

    Why?

    The nebula story is correct or at least extremely plausible given we are seeing it in action.

  56. #56 mdwasefali
    wb, india
    January 19, 2013

    “earth rotate around the sun” this sentence written early 1400 years ago in the book of islam the “QURAN”

  57. #57 ken
    February 21, 2014

    The earth doesn’t spin,the sun does. You going to tell me everything in the universe rotates around the sun? Bullshit!

  58. #58 IBRAHIM ABDULLAHI DAMBATTA
    KANO STATE NIGERIA
    February 22, 2014

    Earth and othes planets don’t spin but the sun is rotating around them.
    From the charastracts of nine planets and the visible evidences, we can see that earth and other planets are not vkrevolving. As astronomers say that nine planets are revolving round the in a circular orbit and at diffrent distance from the sun with diffrent speed which lead to diffrent time for completing theirs revolution round the sun. As mercury takes 88days,Venus 225days etc to complete their revolution round the sun, during the revolving, the distance between planet to the sun e.g
    57,600,000km the distance of sun from the mercury will be constant and unchange but, the diffrence of distance between one planet to another will quaitly diffrent from time to time that is some time to be long and some time to be short due to their revolving at diffrent speed. For example when in september the distance from the earth to mars is 20,000km but may be in June it can be decreares or increase to about 10,000 or 40,000 respectively.
    But in the current study of planets there is no diffrence of distance from one jplanet to another. And in my proof there most be diffrence of distance from time to time.
    This proof that earth and other planets are not revolving. There evidences and research I made before proofed this and I found how the season,year,varying length of the day and night and change of season tempreture are occur with the revolution of the earth. Than I made a drawing of how the sun rotate the planets. 5v

  59. #59 Manny Clay
    Georgia
    February 23, 2014

    All agree that you cannot feel motion in a strait line, only acceleration or deceleration, and Kepler proved that the orbits of the planets are elliptical and not circular. His 2nd law states that planets sweep thru equal areas in equal periods of time. This would mean that when approaching nearest the sun the planet must accelerate for this to be true. (See Wikipedia on Kepler’s 2nd Law) It would then have to decelerate until it came to midpoint where it had constant velocity. Opposite the sun the planet again must decelerate until midpoint where it again will have a constant velocity only to accelerate again as it neared the sun and so on. We feel none of this change in velocity although we can feel a faint breeze on our cheek on an otherwise still day, or a slowing on the velocity in a wind tunnel.
    I have conversed at length with an ascentist who agrees with Einstein that you cannot determine if it is the earth moving or the sun and stars in order to make the earth 24 hour day/night event. He stated that there were innumerable possibilities for this. When pressed he could not argue that there were only 2, that is, the heliocentric model or that proposed by adherents to the geocentricity position. Only 1 can be the TRUE frame, relativity notwithstanding. How can we know that? Which way does the moon go? Our eyes tell us it goes east to west just as the sun and stars. But the heliocentrist MUST BELIEVE that it goes west to east. The moon is not going in both directions, its going one way or the other.

  60. #60 kurt
    June 6, 2014

    I would like to see you do the experiment with a wooden, or non magnetic pendulum please