Why couldn't the Lord Ruler correct the planets orbit?

[Fallen Rope Oldblood]

When he modified plants to be both edible, and able to exist with very low sunlight, was he granted knowledge about biology, or did he just tell the power to create an outcome. 

If the first, why wasn't he also granted knowledge of what temperature life needs to be, and the knowledge of physics to calculate how far that means the planet needs to be, although I guess he might not have been able to tell the temperature of the sun. 

If the second, why couldn't he instruct them to put the planet in a safe orbit. 

[Ookla the Excessive Mistborn]

1 minute ago, Fallen Rope said:

When he modified plants to be both edible, and able to exist with very low sunlight, was he granted knowledge about biology, or did he just tell the power to create an outcome. 

If the first, why wasn't he also granted knowledge of what temperature life needs to be, and the knowledge of physics to calculate how far that means the planet needs to be, although I guess he might not have been able to tell the temperature of the sun. 

If the second, why couldn't he instruct them to put the planet in a safe orbit. 

I believe that it was because, when he first started out with his powers, he was too inexperienced to do it correctly, and it was one of the first things he did. By the time he realized his mistake, his power had waned too much for him to fix it.

(Don’t quote me on this, my knowledge is a bit rusty.)

[Ookla the Quill Twinborn]

The Lord Ruler was far too new to the power to be able to shove a planet around willy-nilly, with no accurate reference points in space. The reason why he was able to make the plants work correctly was that by that time, he was dealing with the influx of Preservation into his mindset and couldn't move the planet anymore, solely reacting to what his earlier attempts to do so had caused.

[Calderis God Beyond]

1 hour ago, Lunamor said:

I believe that it was because, when he first started out with his powers, he was too inexperienced to do it correctly, and it was one of the first things he did. By the time he realized his mistake, his power had waned too much for him to fix it.

(Don’t quote me on this, my knowledge is a bit rusty.)

This is partially correct. Rashek had the strength to move the planet... But on that scale he didn't have the necessary control. So he worked on a smaller scale. 

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Brandon Sanderson

Chapter Forty-Four - Part One

Subtlety with the Power

The Lord Ruler created koloss, kandra, and Inquisitors during his time holding the power. This took some practice and experimentation, however. As has been explained, holding the power granted some intuitive understanding of how to use it. For instance, he knew how to make Hemalurgic creatures—but he wasn't practiced enough with the specifics at first to know exactly what he wanted to make or what the results of his experimentations would be.

In a similar way, he knew that he could move a planet—and did. With practice, he could have figured out how to shove the planet the right way to place it correctly in orbit. Unfortunately, you can't really experiment with moving a planet around without causing a whole lot of damage.

And so, he could do something as subtle as create three new races—and, with that practice in biology, redesign the world's plants and animals slightly—but could be so far off in the way he shoved the planet about the first time.

The Hero of Ages Annotations (Dec. 4, 2009)

Quote

Brandon Sanderson

Chapter Seventy-Six

The North Pole

One of my big challenges in the geography of this world was figuring out how we could have a kingdom set at the pole of the world while at the same time maintaining a normal day/night cycle. My original plan was for the Well of Ascension to be located a distance to the north of Luthadel, up at the geographic north pole of the planet. When I was revising the second book, I realized that wouldn't work for various reasons. (More on this on the MISTBORN 2 Alternate Ending deleted scene page.) I changed things so that when the Lord Ruler held the power in the Well, he decoupled the geographic north pole and the magnetic north pole.

In our world, the magnetic north pole is located about eleven degrees of latitude south of the geographic north pole. On Scadrial, the two poles were originally in the same location. When the Lord Ruler moved the planet too close to its sun and realized he didn't have the control to place the planet in the proper orbit, he created the ashmounts to cool the atmosphere. He also wanted to keep access to the Well under his control, so he decided to build his capital city right above it. However, he realized that on a planet with a tilted axis, a city at the north pole would have seasonal daylight variation so extreme that at the height of summer the sun would never set and during the dead of winter the sun would never rise. He could remove the axis's tilt, but that would just make the sun perpetually skirt the horizon all year round.

What Rashek decided to do (and he had to make split-second decisions in the brief time he held the power) was to shift the crust of the whole planet so that the Well was at a latitude that would have more standard seasonal variation, and to re-create the Terris mountains in the new North (to maintain the rumors that the Well was located there). He worried that the new location of Luthadel would be too hot due to the latitude, but it turned out that moving the Well created an unexpected effect. The planet's magnetic pole followed the Well as he relocated it—and the ash from the ashmounts was slightly ferromagnetic. (Ferromagnetic volcanic ash has some precedent in our world.) So the interaction of the ash with the planet's magnetic field's new alignment meant that its protective cloak over the area of the Final Empire caused it to be cooler than the now unprotected geographic north pole.

One side effect of this is that all compasses point toward Luthadel. Since it's been that way for a thousand years, no one finds it odd–in fact, it's used as evidence of the Lord Ruler's divinity. It also makes it mathematically very easy to pinpoint one's exact location in the Final Empire using a combination of the compass reading and noon observations. Not that it's easy to get lost in the Final Empire in the first place—the geographical area of the planet's surface that the Final Empire covers is actually quite small.

Ultimately, when it comes down to sophisticated geography and astrophysics, I'm out of my element. If there are mistakes in my reasoning above, that is why I write fantasy and not hard sf.

And I still haven't said anything about what happened at the south pole.

The Hero of Ages Annotations (May 4, 2010)

 

[Ookla the Nameless Mistborn]

Sazed's explanations in the epigraphs also add that Rashek was being influenced by Preservation's intent and so wouldn't have been able to fix the planet's orbit after his disastrous first attempt even if he wanted to.

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The subtlety displayed in the ash-eating microbes and enhanced plants shows that Rashek got better and better at using the power. It burned out in a matter of minutes—but to a god, minutes can pass like hours. During that time, Rashek began as an ignorant child who shoved a planet too close to the sun, grew into an adult who could create ashmounts to cool the air, then finally became a mature artisan who could develop plants and creatures for specific purposes.

It also shows his mind-set during his time with Preservation's power. Under its influence he was obviously in a protective mode. Instead of leveling the ashmounts and trying to push the planet back into place, he was reactive, working furiously to fix problems that he himself had caused.

 

[Calderis God Beyond]

@Weltall thank you! That is what I was originally looking for, but forgot it was an epigraph.

I specifically searched Arcanum for "Rashek+reactive"