[waps]

In other news : 3 in 4 hacker news readers don't know the earth doesn't orbit the sun at all. That is an impression created by the fact that the space around the sun moves as a result of gravity. This results in that the location of the earth doesn't change, but as the sun is sucking in space and constantly pushing out it's matter the distance doesn't change. This results in the fact that a straight line path around the sun at the relative speed difference that the earth the sun have, and then transpose said trajectory into an approximate euclidean space with the sun as it's point of origin results in a (roughly) ellipsoid trajectory.

But make no mistake : the earth is standing still, it's not moving. There is no actual movement of either the earth, or the sun, or for that matter, any other planet or body, as a result of gravity. The earth is not circling the sun, it is moving in a straight line through what just happens to be non-euclidean space. Hell there is no gravity acting on the earth, nor for that matter on you (on the contrary : you are being accelerated upward, not downward at roughly the rate at which the earth sucks up space).

(Here movement is defined as the only viable relativistic definition of movement : a movement that can be observed to be different from standing still, meaning travelling at a fixed speed in a straight line is not moving at all)

If the earth ever starts orbiting the sun, life on earth will become impossible in a matter of minutes, as the resulting acceleration would affect magma flow and would very quickly change the entire surface of the earth into a liquid state. In that case the earth's surface would quickly change to the average temperature of the earth itself : ~6000 degrees celcius.

People say that the earth is orbiting the sun, because people are thinking within an euclidean reference frame. If you ignore the fact that we live in a relativistic universe and just act as if it's euclidean, it looks like the earth is orbiting. But in (what we think) is the real structure of the universe, that's not the case at all.

Saying that the earth orbits the sun, or God forbid, that it circles the sun, are flat-out wrong statements. The last time scientists actually believed that was about 1931. The "science" that is being popularized is either old, or just flat-out wrong. This goes for other popular versions of scientific theories as well. If evolution is "mutate + natural selection + goto 1", then humans don't evolve at all, and neither does any larger lifeform (and it's still an open question if bacteria evolve or not). Hell, did you know the earth is the exact center of the universe ? No joke. Read a bit about Hubble's discovery. The big bang is not actually the beginning of time, google inflation theory (and even inflation theory doesn't model the beginning of time). Did you know that we lost ~98% (that's a lower bound) of all mass in the universe ? We have zero clue where the rest of the universe is.

[pavelrub]

There is so much wrong with this comment I don't even know where to begin. It will suffice to say that this is a huge conceptual muddle, and a great example of where conceptual confusion can lead us if we are not careful. You are confusing 'discovery' with 'giving new definitions', 'reality' with 'a mathematical model that describes...', physics with everyday language, and you also seems to be unaware of what 'orbit' and 'motion' actually mean: http://en.wikipedia.org/wiki/Orbit http://en.wikipedia.org/wiki/Motion_(physics)

It should be clear that it can never be the case that by using a new mathematical model we can come to the conclusion that "the earth is standing still". This would be equivalent to inventing a new theory of mind according to which people never get angry. At best, what we can achieve is a new interpretation of the words "standing still", different from what they actually means, under which the earth is doing something else. However, this would simply be a matter of choice, not of discovery, and a pretty bad one at that (see Wittgenstein's criticism of Freud).

[lutusp]

> It should be clear that it can never be the case that by using a new mathematical model we can come to the conclusion that "the earth is standing still".

Apart from the OP's many outright errors, this one suffers from the defect that it assumes there is only one possible frame of reference. One can obviously choose a frame of reference in which the earth is motionless, but relativity denies any special significance to a particular frame of reference -- indeed, that's what relativity means.

[waps]

Which is exactly the point. Whether the earth rotates depends on your frame of reference. You can pick one where it is, you can pick one where it isn't. Neither is "true". So saying the earth orbits the sun is a choice : it is not a true or false statement, just a statement reflecting an opinion. Occam's razor (as well as general mathematical practice) dictates that we declare this to be not true in that case (note the massive difference between "not true" and "false". Not true means you don't know it to be true AND you don't know it to be false either). But this is only possible in euclidean space, you have to transform space (change the normal/distance function) before you can choose a reference frame where there is rotation.

If you look at it in the original relative space, without an euclidean transformation, there's only 2 ways to see it : you can only pick reference frames where the earth is standing still entirely, or you pick reference frames where it is moving along a straight line. You cannot pick a reference frame in relativistic space that shows ellipsoid movement (like the one predicted by the Newtonian theory which is generally what people mean by "orbit").

So you can't actually pick reference frames to do whatever you want. In order to get something looking like an orbit you have to pick a reference frame where you not only have messed with the point of origin, but also projected the distances between objects to be invariant under the influence of gravity. Which they're not in reality (effectively you're claiming that distances everywhere in the universe are as they are at an earth-sun lagrange point, which is not true). Only by doing that transformation can you get an orbital pattern.

At that point, from a purely mathematical point of view you can analyze what other motions you could get that are equally true as saying it orbits. So you can say, you can put the origin point anywhere you like, moving, accelerating, whatever you want. In addition to that you can arbitrarily change the distance function. So you could make one where the earth spirals into the sun. Or spirals away from it (simply introduce a time component in the distance function). Hell, you could make one where the earth and the moon look like they're bouncing on the surface of the sun that looks like the disc in the discworld (put origin at the center of the sun, distance function is a the normal multiplied by the tangent of an angle that goes from the center of the sun to where the moon was 48 hours ago, and in the z direction all distances are zero). Hell, I bet that even if you demanded the reference frame be euclidean you could still make it look pretty silly (I think my spiraling examples would still be euclidean). Reasons for picking one over the other ? None.

Well, one : if you want to calculate the influence of the laws of physics inside our solar system, having an euclidean reference frame centered on the sun-planets lagrange point (which is not the center of the sun) is pretty useful, as it means you need 11 (number of planets) transformations to calculate the path of a satellite moving through the solar system, whereas a relativistic reference frame would require 12 transformations (imho because they don't change rotation they're simpler though).

Aside from the utilitarian choice, all those statements are simply equally true to saying that "the earth rotates around the sun". Just because we prefer one arbitrary kind of reference frame above others here on earth (ie. euclidean) doesn't make it any more real.

And yes, compared to objects "near infinity" the earth arrives at the same spot once a year, but that doesn't make it's path any less straight.

[lutusp]

> Whether the earth rotates depends on your frame of reference. You can pick one where it is, you can pick one where it isn't. Neither is "true".

No, both are true, yet you claimed that "3 in 4 hacker news readers don't know the earth doesn't orbit the sun at all" which is a false and ignorant claim.

> So saying the earth orbits the sun is a choice : it is not a true or false statement, just a statement reflecting an opinion.

False! Mathematical physics is as far from opinion as you can get, and it has vast amounts of supporting evidence.

> You cannot pick a reference frame in relativistic space that shows ellipsoid movement (like the one predicted by the Newtonian theory which is generally what people mean by "orbit").

Yes, you can! As I said earlier, sufficiently above the sun's north pole, you would see a classic Newtonian orbit, because of the choice of reference frame.

> you can only pick reference frames where the earth is standing still entirely, or you pick reference frames where it is moving along a straight line.

I just proved this claim to be false. But you know what? I'm not going to go through and correct all your false arguments (they're all false). I've had this exact experience more times than I care to remember. You don't know anything about physics or mathematics, your overall argument is post-modern ("It's all opinion"), and you're a waste of time.

If you actually understood the topic, you would use 10% of the words you use while being wrong, and your posts might become worth reading.

[waps]

> Yes, you can! As I said earlier, sufficiently above the sun's north pole, you would see a classic Newtonian orbit, because of the choice of reference frame.

No you would not. Here I assume a correct reference frame : the start point is above the sun's north pole, but it is in gravitational freefall, not artificially accelerated to the same relative position above the sun. If you looked at the earth moving and describe it's movement as an equation in relativistic space you'd get p = k * s + c (with k a real number, p s and c vectors).

This is not a rotation, obviously.

Intuitive observation would show rotation, but that's wrong, or at least that's not really what's happening. Note that your position "above the sun's north pole" is actually an accelerated movement at a point in time. As such it is not a reference frame that is at rest, and as such is not the type of reference frame you'd want to use for anything, unless of course you're using newtonian physics.

[pavelrub]

> Just because we prefer one arbitrary kind of reference frame above others here on earth (ie. euclidean) doesn't make it any more real.

You got it all backwards. Our preference for a certain reference frame is exactly what makes it real, because that's what 'real' means.

Certain frames of reference are almost useless, while others are very useful in our everyday life. This is why "I'm going to the store" is true, while "the store is moving toward me" is false: it is our application of those words in everyday life that defines what we would call 'true' and 'false' here.

It is ridiculous to claim that the above are equally true because supposedly we can choose our reference frame however we like: this is simply not what we mean when we talk about "true" and "false" here. By focusing too much on physical vocabulary, you are losing sight of what certain words mean in the first place.

If you develop a theory that says the fridge is moving toward me when I'm hungry (= I'm going to the fridge, from a different frame of reference) - you are not making a discovery, you are simply making up new definitions of existing words, and you are confused.

Also, mathematical models are just that - math, useful abstractions we can predict stuff with. Assigning to them an ontological status is a matter of choice and of personal belief, not of knowing anything about physics.

[lotharbot]

> "Occam's razor ... dictates that we declare this to be not true"

Note that Occam's razor does not actually have the authority to dictate anything. Occam's razor is a useful heuristic -- like frames of reference, you may treat it (or various similar heuristics) as true, but may also treat it as not true.

----

This whole exchange reminds me of one of my favorite Asimov essays, The Relativity of Wrong [0]. You can certainly make the argument that the reference frame "the earth goes around the sun" is not true, but it's less not-true than "the sun goes around the earth". "The earth goes around the sun" is a correct assessment of the relative behavior of the bodies in a reference frame which is in a sense arbitrary, while "the sun goes around the earth" is an incorrect assessment of the relative behavior of those bodies under either Euclidian or relativistic reference frames.

[0] http://chem.tufts.edu/answersinscience/relativityofwrong.htm

[ealloc]

There are 3 main proofs (I know of) that the Earth orbits the Sun:

1. Stellar parallax: Stars will appear at slightly different positions in the sky due to the changing position of the Earth during its orbit. Many astronomers from the 1500s to 1800s hoped to measure parallax, and it was finally measured by Friedrich Bessel in 1838. This is the work that first made Bessel famous.

2. Stellar Aberration: Stars appear at slightly different positions during the course of the year due to the finite speed of light relative to the (changing) velocity of the Earth. This was first explained and carefully measured by James Bradley in 1729, making him the most famous scientist of the 18th century according to scientists of the time, including Laplace.

3. The Foucault pendulum: Pendulums on Earth precess. This is not so much proof that the Earth orbits the Sun, but that the Earth rotates in place. The fact that the sun appears to rise/fall/go around us is an illusion due to this rotation. First demonstrated by Foucault in 1851.

I disagree with you on the reference frame/general relativity argument. It is true that, by GR, the actualy picture of spacetime is more complicated. However, there is an intuitive notion of 'orbiting' which is very useful which applies in classical/SR, which applies in inertial reference frames, and in that ase the above observations make clear that the Earth orbits the sun.

Also:

>it's still an open question if bacteria evolve or not

> If the earth ever starts orbiting the sun...as the resulting acceleration would affect magma flow

This is silly.

[baddox]

I don't think that's an appropriate analysis, because "orbit" has a specific definition in science that abstracts away the technicalities like Euclidean space vs. gravity as "bent space." The Earth absolutely does orbit the Sun.

[lutusp]

> This results in that the location of the earth doesn't change, but as the sun is sucking in space and constantly pushing out it's matter the distance doesn't change.

This is just one of many egregious errors the OP makes, scattered alongside a few obviously misunderstood elements of real physics. I advise HN readers to ignore the OP's post.

[300bps]

the earth is standing still, it's not moving...The earth is not circling the sun, it is moving in a straight line

You may have this somewhat right in your head but it comes out as contradictory nonsense in your comment.

[everyone]

Yes the relativistic model is more accurate but like any physics it is still a model and only an approximation.

The newtonian / euclidian model is going to be accurate enough for most people (and some space missions) + its much simpler to compute and also it lies closer to human 'common sense' making it a lot easier for people to grasp and think about intuitively.

[chc]

What is the meaningful difference between orbiting and moving in a straight line that creates an ellipsoid in Euclidean space?

[lutusp]

Well, apart from the fact that the OP is an undisciplined mixture of almost-right physics and fantasy, spacetime isn't Euclidean, it's curved by masses.

But, contrary to the OP, if you took a position above the sun's north pole, you would certainly see the planets orbiting the sun, just as in pre-relativistic physics. The reason? A different spacetime curvature at that location.

It's true that, in modern physical theory, there's no force called gravity. It's also true that the earth is moving in an inertial "straight" path through curved spacetime. But it is absolutely false to say that the earth isn't orbiting the sun.

[GhotiFish]

hell. No one knows anything if you assert that you don't truly know what something is unless you understand every minute intricacy of it. Most people wouldn't define gravity as an object moving in a straight line through space time. However those that know that that is the nature of gravity, would then define gravity as such.

[wvenable]

> the earth is standing still, it's not moving... it is moving in a straight line

Wait, is the earth moving or not? I also can't figure out what definition of orbit you are using. Your comment feels far too clever for it's own good.

[lutusp]

The OP is trying to argue that there's a preferred frame of reference in a physical theory (relativity) that explicitly disallows preferred frames of reference. If you took a position roughly 200 million miles (about 320 million kilometers) above the sun's north pole, and watched from there, you would certainly see the earth orbit the sun. The reason? Different curvature from that perspective.

The OP could have simply said that, in relativity, there's no force called gravity, instead planets orbit their parent bodies because of curved four-dimensional spacetime. He then could have quoted physicist John Wheeler, who famously said, "Matter tells space how to curve, and space tells matter how to move."

After the OP correctly said that the earth is moving through curved spacetime in a straight line, IMHO he should have turned in his golf clubs.

> Your comment feels far too clever for it's own good.

You got that exactly right. The OP's intention is to confuse, not enlighten.

[Iftheshoefits]

It is too clever, by half. From my perspective it's a long-winded and self-contradictory (as you note) attempt at punning with curvature tensors and metrics, only not doing it right.