# Rocket Scientists Should Know Better

A while back I posted a little rant about false precision in measurements (though it turns out a chose a poor specific example). Today I was perusing the list of exoplanets discovered to date (how cool is that?), and I noticed another source of ridiculous artificial precision. For instance, according to the table planet tau Gem b is 299.8125 light-years away — which is simply ridiculous. They are claiming to know the distance to the planet to a precision of less than one light-hour, which could well be less than the orbital radius of the planet. (It has a mass eighteen times that of Jupiter.) So even if the distance were exactly 299.8125 light years when tau Gem b was found, that’s not the distance now.

I looked a little more at the table, and saw a pattern. Many of the ridiculously precise numbers were conversions of fractions. 13/16 (itself suspect in my book) becomes 0.8125; a measurement rounded to the nearest sixteenth of a light year is suddenly represented as being accurate to 0.0001 light years.

Way to set an example, Jet Propulsion Laboratory! I hope the guys in charge of this table aren’t expected to do any actual science over there — although surely the guys who discovered the planets drop by to check the list now and then. Someone should have said something by now, you’d think.

The public-facing aspect of the scientific community needs to be careful what example they set. If the rocket scientists at JPL don’t care enough to get it right, no wonder the public accepts advertising claims with ridiculous precision. (51% of your fiber for the day!)

## 3 thoughts on “Rocket Scientists Should Know Better”

1. Yeah, like the sugar substitute commercial that claims you can save 100 calories a day by removing a mere 3 teaspoons of sugar from your daily intake. Apparently, when you round it off correctly, 3 x 16 = 100

2. I agree. Additionally, let’s take a different tack and posit for a second that the precision is good, that they miraculously were able to measure to such a degree. If we accept that degree of precision then we move to what is it doing for us? What do we gain by knowing the exoplanet is 299.8125 lightyears versus 299 lightyears? Nothing. Hells bells they shoulda rounded off to an even 300 light years. 300 ltyrs is damn far, while 299 is “damn far” with too much useless chatter.

• Oh, but “300 light years” just sounds so simplistic. Never mind that 300 is what you get when you round correctly, even if you are keeping 3 significant figures.