2

The earth (-------) around the sun.

Also, if there is a word to describe motion of an object that is rotating but moving ahead in a straight line.

  • 1
    Better: The earth simultaneously rotates on its axis and revolves around the sun. Simultaneously rotating and revolving around the sun means that we are doing both around the sun, but we are not actually rotating around the sun. – Yosef Baskin Feb 3 '17 at 17:47
  • Do you want a technically accurate term or a "poetic" one? – Hot Licks Feb 3 '17 at 17:50
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    There is no single word for that. – Lambie Feb 3 '17 at 17:51
  • It will be interesting to get both technically accurate word options as well as "poetic" ones .. – Monzoor Feb 3 '17 at 17:56
  • 4
    Each planet is a slithy tove. It gyres and gimbles in the wabe. – cobaltduck Feb 3 '17 at 19:00
5

The earth whirls around the sun.

Whirl can mean rotate, spin, orbit, revolve, wheel, circle, or twirl. It can also be used to mean moving in a straight line while spinning.

From the Free Dictionary:

To move while rotating or turning about

"The dancer whirled across the stage".

In this case, of the Earth revolving on its axis around the sun, it has been used in Stargazer's manuals:

The ecliptic is inclined to the celestial equator by 23.5 degrees because the earth's axis is tilted by that same 23.5 degrees as its whirls around the sun every year.
New England Starwatch by Mike Lynch

...as well as in lesser scientific descriptions:

As you whirl around the fire and the Earth whirls around the Sun, so our star, in one of the four arms of our Milky Way Galaxy, whirls in a similar but far greater cycle, passing through its own stellar seasons on a scale of time spanning millions of years, billions of handclaps.
The Goodly Spellbook; Olde Spells for Modern Problems by Dixie Deeman, Steve Rasmussen

And even served in the first line of the poem by Tua Forsström, The snow whirls over the courtyard's roses, to describe as what I imagine to be a rotating swirl of white moving through a garden.

  • @JasperLoy That´s why "whirl around", as in the sample, sentence works. Yes, it needs a preposition to accompany to work. – Cascabel Feb 3 '17 at 18:41
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    I think this answer demonstrates that "whirl" is appropriate both for "rotating and revolving" and for "rotating while moving in a straight line." If you want to distinguish between those two cases, I think you need more than one word. – David K Feb 3 '17 at 22:23
4

A single-word term limited to the precise meaning you want (rather than a broader definition including similar types of motion) would be a technical term in mathematics, and unfortunately it seems not to exist.

However, there is a mathematical term, epicycloid, that comes quite close to your intended meaning: “the path traced out by a point P on the edge of a circle of radius b rolling on the outside of a circle of radius a” (from Wolfram MathWorld).

This isn’t quite what you want, for two reasons:

  1. There isn’t a corresponding verb (the term is a noun, describing the path of a point on the edge of the rolling curve, not a verb describing the motion). However, the adjective epicycloidal is available; it generally refers to the path but would be understood (by mathematicians/physicists/engineers anyway) if used to describe the motion.
  2. The earth’s orbit is not quite circular (plus a few other minor complications). A better approximation would be to replace the base motion by an ellipse, but I have browsed MathWorld and other maths sources and can’t find any such term. There are more general terms for which neither motion has to be circular, but nothing that means precisely base curve = ellipse; rolling curve = circle.

As there appears to be no mathematical term for precisely your meaning, it is most unlikely that there is an everyday term. Whirl can imply a combination of rotation and forward motion, but the forward motion isn’t limited to an ellipse, or even to closed curves in general.

The motion of an object that is rotating and moving ahead in a straight line is cycloidal: “the locus of a point on the rim of a circle of radius a rolling along a straight line”. Again, there isn’t a corresponding verb.

  • +1 Welcome to ELU! If you want to add to your already very good answer, there is actually a very old verb form, epicycle, per the OED: "† epicycle, v. poet. Obs. rare. 2. intr. To move in a path resembling an epicycle." ("† epicycle, v." OED Online. Oxford University Press.) and "epicycle, n. 3. A curve described by a point on the circumference of a circle as it both revolves around its centre and moves along the circumference of another circle; = epicycloid n." ("epicycle, n." OED Online. Oxford University Press.). Feel free to edit any of this into your answer, or not. – 1006a Feb 3 '17 at 23:35
  • @1006a: Thank you very much for your suggestion - I'll edit my answer. (OK, so there's no corresponding verb that even a mathematician/physicist/engineer would know.) – Lucky Feb 3 '17 at 23:42
  • Heh, yes, if it can only be found by browsing the OED, which has it marked as poetic, obsolete, and rare, that's pretty much as obscure as a word can get. – 1006a Feb 4 '17 at 18:25
  • @Lucky I was going to post epicycles before you beat me to epicycloid..... (I do have a math degree, but I thought of the word because of its astronomical history.) – Hellion Feb 8 '17 at 3:01

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