<p>The anomalous precession of Mercury's perhelion is 43 arcseconds per century.</p>
<p>The perhelion distance of Mercury is 46 Mkm. A 43 arcsecond shift is therefore approximately equivalent to a displacement of 9600 km, or 96 km per year.</p>
<p>(i.e. Construct an isoceles triangle with an opening angle of 43 arcseconds and equal sides of 46 Mkm. The base will have a length of 9600 km.)</p>

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2021-12-08T19:47:02.917Z
2021-12-08T21:33:24.113Z
2021-12-08T21:33:24.113Z
ProfRob
<p>If I divide the elliptical circumference of Mercury's orbit by .43 arcseconds, I get an answer of almost exactly 75 miles....</p>
<p>BUT, it is the precession of the periapses that is off, not 'just' its position along its orbit, so...</p>
<p>Is my calculation correct?  If I drew a straight line (actually, a slightly curved one) from its actual position after one year, to its Newton-predicted one, would it be off by 75 miles?</p>

<observational-astronomy><orbit><orbital-mechanics><general-relativity><orbital-elements>
Does the .43 arc-second per year deviation of Mercury's orbit from Newtonian predictions mean that its position is 'off' by 75 miles per year?
Kurt Hikes
# Does the .43 arc-second per year deviation of Mercury's orbit from Newtonian predictions mean that its position is 'off' by 75 miles per year?

(Asked by: username_0 on 2021-12-08)

If I divide the elliptical circumference of Mercury's orbit by .43 arcseconds, I get an answer of almost exactly 75 miles....

BUT, it is the precession of the periapses that is off, not 'just' its position along its orbit, so...

Is my calculation correct? If I drew a straight line (actually, a slightly curved one) from its actual position after one year, to its Newton-predicted one, would it be off by 75 miles?

**Tags:** observational-astronomy, orbit, orbital-mechanics, general-relativity, orbital-elements

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## 1 answers

### Answer by username_1 on 2021-12-08. Score: 2

The anomalous precession of Mercury's perhelion is 43 arcseconds per century.

The perhelion distance of Mercury is 46 Mkm. A 43 arcsecond shift is therefore approximately equivalent to a displacement of 9600 km, or 96 km per year.

(i.e. Construct an isoceles triangle with an opening angle of 43 arcseconds and equal sides of 46 Mkm. The base will have a length of 9600 km.)


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