Today’s full moon happens to (almost) coincide with the the moon being its closest to Earth for 15 years (it was last closer on 8th March 1993). The BBC have an article, including:
Its orbit is elliptical, meaning it does not follow a circular but rather an oval path.
It is currently approaching the point where this oval orbit is nearest to the Earth.
Gotta love the generic term “oval”. From the latin word for egg (ovum), it’s a rather generic word for a squashed circle and is often used to describe an ellipse in common speech.
However, that’s where the “dumbing down” comes. The ellipse is a precise term used to describe the shape of an orbit (like that of the moon) – it is the bounded case of the conic section produced by the intersection of a plane and a cone. It has two foci, and can be described by a clear mathematical formula: (x/a)^2 + (y/b)^2 = 1.
So why use the rather inaccurate “oval”, especially since you’ve already used the words “ellipse” and “elliptical” earlier in the article? Where’s Kepler when you need him?
Entries (RSS)
Graeme, is this blog only for the purpose of highlighting flawed BBC journalism? What about the size of parsnips? or the fact you’re getting married? or your favourite cheese?
You know – at some point I might even do some astronomy – that’d shock you all!
actually.. all ellipses are oval. but not all ovals are an ellipse. Like he said, an ellipse is an exact formula.
Visualizing an elipse you could divide it horizontally and vertically right across the middle and you would have 4 exactly equal shapes, (mirrored)
but an oval is like he said, just a squashed circle, it could have most of its “guts” hanging out the lower left quadrant the vertical and horizontal split, and all 4 parts could be different as long as its a continuous roundish shape that connects back to its end.
But then, it wouldn’t be an ellipse.
ellipse are oval, and oval also contains egg shape, squashed circle, circle, and ellipse?
Well – yes, that’s the whole point. Using the two interchangeably as in this (rather old!) example is simply wrong.
The circle is a special case where a=b=radius of circle – but then if it is actually a circle or an ellipse, why not just call them that rather than using the rather indeterminate “oval”?