the earth is 'fixed in its orbit, it is immovable from that orbit, it cannot be shaken from that orbit'
Would I be right in saying that?
Probably not, since the Earth's orbit is a constantly changing thing. This graph shows how the eccentricity - the "ovalness" - of our orbit changes over time. Even at our low present-day eccentricity, we're 5,000,000 km closer to the Sun in January than in July. At eccentricities near maximum, the annual difference is three times that.
And in any case. "immovable" seems a pretty poor description for something travelling 100,000 km per hour. One would expect better from multiple texts that are "inspired."