An Incompetent Astronomer

Ptolemy the Incompetent Astronomer

It is difficult to tell whose works Ptolemy plagiarized because nearly all of the works on astronomy prior to Ptolemy are now lost. Ptolemy does credit Hipparchus with providing certain parts of his theories on the Sun and Moon but denies that Hipparchus developed models for the planets, even though Hipparchus did develop such theories.

Ptolemy makes vague and disparaging remarks about other astronomers that came before him but happily plagiarizes Hipparchus’ star catalog. Ptolemy’s truthfulness about his astronomical observations has been controversial since Tycho Brahe first pointed out that the observations Ptolemy claimed to make in the year 141 are definitely not genuine. As others have proven, Ptolemy did not observe the 1,000+ stars listed in “his” star catalog.

Scholars lament the loss of the star catalog of Hipparchus to history but as R. R. Newton noted, that isn’t true at all. We do have the star catalog of Hipparchus. All we have to do is subtract 2°40′ of arc from the longitudes of the all of the stars in the catalog and we have their original positions as viewed by Hipparchus.

Ptotle is a liar.

We’re going to prove that to you. Everyone else uses math to disprove Ptotle. We’re not big on math. You’re probably not big on math, either. We’re “from Missouri.” You have to show us. We will give you the same respect and assume you’re “from Missouri.” We’re going to take an approach no one else has taken to prove our point.

We’re going to show you in pictures proving Ptotle lied when he said he “made careful observations of the night skies.”

Night sky seen by Ptotle from Alexandria (Egypt) at the same time.

There’s your proof.

That’s irrefutable evidence that proves beyond any reasonable doubt Ptotle lied.

Now, we don’t want to mislead anyone and we’ll explain what you’re looking at so’s you can understand it.

At approximately 6:00 pm, Ptotle can see the fixed-star Canopus rise from Alexandria, Egypt if only he had truly made the “careful observations” he claimed he made, but Hipparchus from his location on the Island of Rhodes in the Mediterranean Sea cannot see it. Not yet. Canopus will eventually rise high enough above the horizon for Hipparchus to see it later in the evening.

That’s the whole point.

Think of the Southern Cross. That is a southern constellation visible mainly from the Southern Hemisphere. Lydia can see most of the Southern Cross from her location in Florida, but Hunter? He’d have to drive twelve (12) hours south to be able to see even one star in the Southern Cross.

Many of the stars in southern constellations never rise higher than Canopus. They either rise briefly then disappear or they skirt the horizon over the course of night which means Hipparchus would never seen them. But Ptotle could have if he had made the “careful observations” he claimed he made.

We all failed miserably at kindergarten so please excuse the crude drawing. The gray shaded area is what Ptotle sees but Hipparchus cannot. We thought we’d do a little very simple math to improve your understanding and you might even find it useful in your world.

Hipparchus made his observations on the Island of Rhodes in the Aegean Sea at Latitude 36°N26’. We want to know what percentage of Earth’s sky is visible to him. To do that, we use the cosine function.

We need to convert 36°N26’ to decimal notation. There are 60’ in 1° of arc so we need only divide 26’ by 60’ to convert to decimal. Doing so gives us 0.433. In decimal notation the Latitude is 36.433°N.

The cosine of 36.433° is 0.804 and your calculator might have the cosine function or if you are clever, you can use a spreadsheet function. Next, we multiply 0.804 by 100 to get the percentage of the sky visible to Hipparchus which was 80.4%.

Ptotle lived in Alexandria, Egypt at Latitude 31°N12’. Ptotle made no effort to carefully observe the skies. All of his data is fabricated which is what you would expect an incompetent to do. Convert 31°N12’ to decimal notation by dividing 12’ by 60’ and we get 0.200 so the decimal notation is 31.200°N.

The cosine of 31.200° is 0.855 and multiplying by 100 gives us 85.5% of the sky visible to Ptotle.

85.5% minus 80.4% means Ptolemy could see 5.1% more of the sky that Hipparchus could never have seen from the Island of Rhodes.

But it’s only 5.1%!

From the film Armageddon, Dan Truman (Billy Bob Thornton) talking to the U.S. President (Stanley Anderson):

Well, our object collision budget’s about a million dollars. That allows us to track about 3% of the sky, and begging your pardon sir, but it’s a big-ass sky.

A “big-ass sky” indeed.

So big, that if Ptotle had made “careful observations” he would have seen more than three dozen 1st, 2nd, 3rd, 4th, 5th and 6th magnitude fixed-stars that Hipparchus could not possibly have seen from his location farther north on the Island of Rhodes.

That’s our proof that Ptotle lied.