Engineering News

How does one precisely measure an object that does not have discrete surface boundaries?

AH, if you *had* to, how would you approach the problem? It's this sort of thing wot makes it fun, yes? :)

I guess an extra long tailor's tape is out of the question?

No, as long as I get the contract! :)

Don't forget the sunblock!

Do it at night. We've gotta cut costs! :)

That is genius!

You wouldn't be captain of the B Ark by any chance?

It was done photographically/photometrically, so I'd guess they scanned the images using an algorithm to detect a specific rise/fall in luminance. If the Sun is truly spherical it wouldn't matter what constant you used, the 50 percent point, the 5 percent point, the 1/e² point, or whatever. You'd set your edge-detection algorithm to some number and find out that, no matter what number you chose, the diameter for that number was always the same, for any positional angle, at any point in the satellite's orbit around the sun.

Bingo!

(AH, I'm still game for that contract lol)

Well, I was gonna say do it a night, but you beat me to it.

Ah, the race goeth to he/she/it wot hath connected to the fasteth CR4 server!

It would seem the Sun is in a gravitationally balanced orbit...

It ought to be slightly oblate from rotation--how much, though?

About as much as Jupiter would be if it's 'day' were 28 Earth days long (rather than 10 hours), i.e., 'not too', but certainly more than it is. Some speculate that the Sun is so spherical because the convection currents within the Sun are much stronger than previously assumed. This seems to make sense, as these currents have no preferential direction with respect to the Sun's spin axis. Stronger currents would tend to swamp the effects of the Sun's spin on its shape, by pushing the 'surface' (chromosphere) outward and fairly uniformly overall. Were these currents to somehow stop, I'm sure the Sun would both be somewhat smaller and assume a more oblate shape consistent with its rotation, IMO. I would hazard a guess that the Sun's *density* cross-section *is* oblate, however. Again, IMO.

That makes sense. I haven't done any calcs on it, or anything.

This resembles the situation of Kansas being flatter than a pancake (in scale, that is).

Hang on a minute

"If the sun were a meter-wide (3.3-foot-wide) beach ball, Kuhn said, the variation in the sun's shape from the highest to the lowest point would be about 17 microns-less than the width of a fine human hair, according to the SDO measurements."

This doesn't sound very impressive compared to.

"Were the electron scaled up to the size of the solar system, any deviation from its roundness would be smaller than the width of a human hair, the team said."

From a recent news article:-

http://www.guardian.co.uk/science/2011/may/25/electrons-round-cosmos

Let's see that picture of the electron again.....cause I don't remember anything round....sounds like hooey to me...

Round in the Classical sense. In the QM sense electrons have no size whatsoever.

Yes, that kind of confounds me, too. Either they are a probability wave or they are a point charge of no dimension, yet in classic physics they can be determined to have a specific radius.