A stray Miri thought -- non-spheroid worlds?

There's one tiny point of dialogue I noticed while taping ``Miri'' for a friend who hasn't got practical access to the remastered Trek. In the opening scene as Spock reels off the physical measurements of Miri-Earth, he mentions that the planet is spheroid-shaped.

It's mighty hard to get something planet-sized which isn't spheroid, though, unless you've run into what are probably artificial constructs like ringworlds or more ornate constructs. Or have Our Heroes run into such a planet recently enough that they can't assume things are back to normal, in an adventure too expensive to be shown on network TV?

 

Oblate worlds are not uncommon (e.g. Saturn)

 

Hydrostatic equilibrium implies sphericity in planetary formation, but doesn't demand it. The planet Mesklin featured in Hal Clement's 1954 hard LitSF novel Mission of Gravity is a notable example of a natural world with a period of rotation so high (Mesklin's "day" is less than eighteen minutes long) that its equatorial diameter is more than double that of the polar value. On a slightly less serious note, one short story in Stanislaw Lem's 1967 collection The Cyberiad depicts an alien supercivilization existing on the surface of cube shaped planets orbiting a cube shaped star.

TGT

 

yes, and I believe Mars isn't round but rather flattened at it's northern pole. It's true, planets need not be spherically inclined.

 

Mars is certainly close enough to be spherical to pass Mr. Spock's first order analysis. So is the Earth, despite its very minor pear-shapedness.

Another good science fiction example of a non-spherical inhabitable planet is Jinx from Larry Niven's Known Space series. Somehow, I doubt the likelihood of an easter-egg shaped terrestrial planet, but who knows?

 

That planet from VOY's "Blink of an Eye" was certainly nonspheroid. It looked like a big donut.

And there's Htrae, of course...the cube-shaped Bizarro homeworld.

 

Folks, "spheroid" doesn't mean "sphere." A sphere is to a spheroid as a circle is to an oval -- a special case where the equatorial and polar dimensions are equal. Just about all known planets (certainly everything that's defined as a planet by current IAU standards, because it's part of the definition) are essentially spheroidal in shape. An oblate spheroid, such as the Earth or Saturn, is one where the equatorial radius is larger than the polar. I believe one where the polar radius is larger (kind of an egg shape) would be a prolate spheroid.

 

For years I've been calling Earth a "flattened spheroid." I never knew the technical term was "oblate spheroid."

Who says Star Trek can't teach you something new?

 

You're absolutely right. In which case, the only times you won't get a spheroid world is if it is too small to collapse into a regular shape.

 

...Or is so big and slowly rotating that it actually becomes a perfect sphere, no longer eliciting the use of the term "spheroid" from Mr Spock.

Timo Saloniemi

 

Not really, because a sphere is a special case of a spheroid, just as a circle is a special case of an ellipse (I should've said "ellipse" before instead of "oval"), a square a special case of a rectangle, and so on.

 

Which is exactly what I meant. Spock would use the more specific "spherical" instead of "spheroid" to describe the rare perfect planet - just like he would use the more specific "circular" instead of "elliptical" to describe a rare orbit whose ellipse indeed was a perfect circle.

Known planets are described as "spheroid" exactly because they cannot be honestly described as "spherical". But as argued by others, the only planets out there that are likely to be "non-spheroid" are those that are a special case of spheroid, that is, perfect spheres or perhaps perfect ellipsoids.

Timo Saloniemi

 

Or minor planets.

Or maybe the writer didn't know what spheroid meant either.

 

Which would, of course, make Miri's world unremarkably like every other planet that the Enterprise crew could beam down to.

Spock makes the "spheroid" observation simply because the writer wanted to give him some scientific-sounding throwaway remark to make.

 

My astronomical knowledge isn't as extensive as Christopher's but I seem to remember hearing that there's no such thing as a perfectly circular orbit. I guess it depends on how many decimal places you use to define "perfect" though.

But there's always something out there that'll mess up your perfect orbit. If they try to put the space shuttle into an orbit with an eccentricity of 0.000 it'll immediately start getting messed up by the sun, moon and other planets.

I wouldn't know about a perfectly spherical planet but it seems I also heard that the closest a celestial body comes to being a perfect sphere is a neutron star because the gravity is so strong. Or so I hear anyway.

Edit: I was wrong about the neutron star. I looked it up and read they can be oblate spheroids because they spin so fast.

Robert

 

The ``pear-shapedness'' of Earth is vastly played up. The difference between the Earth's shape and a sphere is absurdly tiny: the polar diameter is about 20 km less than the equatorial diameter, this on a planet that's 12,000 kilometers in diameter. The gas giants are the least spherical -- Saturn and Jupiter, respectively -- but it's not much and still doesn't come close to making them non-spheroid.

More exactly that's why Nimoy says the word. The writer's needs can't motivate Spock in-character, though.

As it's pretty much impossible to come up with a way to make something you could call a planet that isn't by natural forces driven to a spheroid shape, though ... can we take it as suggestive that there are non-spheroid planets common enough in the Trek universe that it's worth mentioning? That they've run into a ringworld, or an Alderson disc, or something we haven't imagined yet? This is a universe where neutronium can be a structural element, after all.

 

But then he'd be unlikely to call it a "planet" but rather "a structure" of some kind.

 

Well, again, the litany of attributes that Spock gives is the 1960s canon on how Earth should be described. And Earth is described as spheroid because it's almost a sphere but not quite. That's what motivated the writers, not just a general desire to use cool-sounding words.

Why couldn't this motivate Spock, too? It's classic Vulcan slapstick: describe a phenomenon in a run-on sentence and wait and see when the stupid Earthlings catch up and go "You mean it is X?". Then retort with an eyebrow lift and "I believe I just said so". In other words, "spheroid" is not vitally important information, it's petty details intended as such.

Timo Saloniemi