A Mercurial Circumnavigation

Well, sticking with the slightly off-topic for a second, the simplest form of this is probably tiny wings.

When you can get into a rythmn that allows you to use and play with the undulations of the passing landscape it's very satisfying.
Heh, I've never seen that one. That's really great, for something so simple! :D

Progress continues! Last night I made it to about 0, -128.9, for a total of about 160 degrees covered. Almost, but not quite, half-way around. I've transitioned into the night side, so the evening's travel was all about watching the sun set.

For this leg, I used the chrome SRV.

Watching the sun slowly travel down to the horizon, and then disappear:

And finally below the horizon, but some of the corona is still visible:

And of course, I found a few more wrecks along the way:

And some general scenery:

Hi, me again! I watched your videos, great stuff, makes me instantly want to get back out there again. I can see you're already doing a great job of picking your landing spots (the side that's facing you of small smooth mounds) but I have a couple of suggestions for other skills for you to practice if I may make so bold. One is tilting the nose of the SRV down a bit when you're boosting in the air since it will aim your vertical thrusters backwards slightly and increase your speed (called "tilt boosting"). The other (and this is a really really good skill to master) is correcting your yaw attitude with a combination of pitch and roll. Basically, when you find yourself fliving somewhat sideways (crabbing) I can see you slowing down 'cos you know the landing could result in a skid and/or spin out. You can correct this in mid-air by pitching down, rolling towards the way you want to twist and then pitching back again. It's somewhat hard to describe and only comes with lots of practice but basically, the main thing with those bounces (especially at higher speeds) is to hit the ground facing as near as dammit dead square to your direction of travel.

Here's a couple of videos that kinda illustrate me doing this if you watch closely ...


As well as subtle corrections you can actually use the same technique to pull off mid-air 180's when a bad bounce spins you completely around. You'll see me doing this (and almost pulling it off - LOL) near the start of this next one.


Practice makes perfect and one thing a planetary circumnavigator has is plenty of time to practice!
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Yeah, I already do those things, but don't bother as much when the terrain is relatively easy. :) I do need to practice them more though. Conceptually I have that all down. Executing it with finesse is the hard part. :D
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Nicolaus Copernicus was a mathematician and astronomer, in the Renaissance era. His book De revolutionibus orbium coelestium (On the Revolutions of the Celestial Spheres) brought about a revolution in science, with his heliocentric theory of the solar system. Interestingly, he was reluctant to publish it, despite the urging of his closest friends, because he feared the scorn that it would bring him. The dominant theory until then, was still Ptolemy's geocentric system of epicycles.

Among the revelations presented in his book were Earth's rotation on its axis, the fact that Earth is a planet like the others in the solar system, and the correct order of orbits of the planets, from the sun outward. These ideas were not widely popular when he first published his theory, but it gradually took hold in secret.

His system of circular orbits around the sun still had problems with accuracy, as the elliptical nature of orbits was yet to be discovered. He made corrections by retaining a set of small epicycles, which he called "epicyclets." However the correct ordering of the planets naturally fell into place, as he scaled the orbits of each planet relative to the Earth's motion. While he was mostly correct, and his theory could explain the retrograde motion of the planets in the sky, it couldn't fully prove the heliocentric model until Kepler later cracked the math behind elliptical orbits, eliminating the need for epicycles altogether. In the meantime, his model was comparable in accuracy to Ptolemy's model that was still in widespread use after more than a thousand years. Copernicus offered a much simpler system that achieved comparable results.

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Wow, I made a ridiculous amount of progress yesterday, since my wife wasn't home for most of the evening. :D I traveled a whopping 80 degrees, crossing both the 1/2 and 2/3 marks of my journey, ending at 0, -48.98, leaving just about 120 degrees to go.

Since I'll be wrapping up a lot sooner than planned, I'll need to accelerate the science history posts. I had originally planned to post them 1-2 days apart, but daily might have worked better this week. As it stands, I have one more written, and two more to write.

I crossed the 50% mark at the base of a mountain (actually already on part of the slope) that I decided to call Olympus Mons. While I'm sure it's quite tiny compared to its namesake, it's probably the largest single mountain peak that I've come across here. So of course, I had to climb up to the summit. The curvature of the planet was visible from up there. The side I climbed was pretty steep, but it had a much more gradual slope on the other side.

And of course, the usual crashed junk: (I post one screenshot of each crashed object, so apparent duplicates are actually separate locations)

Various Nebula shots:

Parked for the night, under the Magellanic Clouds:

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And I have been hurrying to find the volcanism on this planet before you were done, but with it being so small, the glide technique is not beneficial at all, and it only being Minor magma, there aren't many sites to find...you are probably going to beat me as I have only covered about 20% of the total surface area :D
Heh, something I didn't notice immediately is that even though I was only partly up the slope toward the mountain, this screenshot shows the gravity dropped to 0.05.

I have noticed the same with my volcanic hunt. Since gravity is determined, at least in part, by distance from the body center, variations like this are more likely on oddly shaped bodies where you are on an outward bulge.
Rep tank's empty for now. :D I had a surprising amount to give for the circumnavigation and the history lesson. I'll be back once I've spread around the love. ;)

Kepler & Galileo

Galileo, born approximately 100 years after Copernicus, revolutionized astronomy with the use of the telescope. He was able to observe the phases of Venus, which is an inner planet that will never show us its fully illuminated side, which proved the heliocentric model. He also observed moons circling Jupiter.

Around the same time, Johannes Kepler was working out a series of laws to describe the orbits of the planets around the sun. It took him about 10 years to complete his book, Astronomia Nova (A New Astronomy), before publishing it. In his book, he outlined equations and terminology to fully describe elliptical orbits in three dimensions, all of which are still in use today.

Prior to working out his theory, Kepler had worked as an assistant to the astronomer Tycho Brahe, who had collected a lifetime of astronomical observations, but kept it mostly hidden from Kepler for fear that he would use it to try to prove a Copernican heliocentric theory. When Tycho Brahe died, the collection of data passed on to Kepler, who was able to use it for completing his theory.

Like those who came before him, Kepler believed that orbits should be perfect circles, but struggled to make that work with the recorded observations of Mars that Brahe had collected. Eventually he stumbled upon the fact that an imaginary line drawn from the Sun to a planet's position will sweep out an equal area of space in an equal time, regardless of which side of the orbit the planet is in, and how fast it is moving there.

This discovery, which became his second law of orbital motion, led to what became his first law: that the planets move in elliptical orbits, with the sun at one focus of the ellipse. His third law shows that there is a precise relationship between the planet's distance from the sun, and the period of the orbit (the length of time it takes to complete one orbit).

Kepler had tried various other orbital shapes, including an egg-shaped ovoid, to explain the equal area over equal time phenomenon. This was unsuccessful until after approximately 40 attempts, that he tried fitting it to an ellipse. He had previously dismissed it as too simple of a solution to have been overlooked by his predecessors. Once he demonstrated that this perfectly fit the Mars data, he concluded that it must be true for all of the planets.

What Kepler lacked though, was an understanding of why. He proposed that there were two forces acting upon the planets: one to propel them forward through their paths, and one to attract them toward the sun. What he didn't understand was that these were simply inertia and gravity, respectively. He did however correctly deduce that whatever solar force was acting on the planets, it must lose strength over distance, since the planets move more slowly when they're further away.

While very precise, there are still orbital effects that can't be accounted for using his perfect elliptical equations. His system assumes a 2-body system, with planets represented as point-masses orbiting a stationary sun. In reality, the sun orbits a barycenter that is contained within itself, and the planets interact with each other in subtle ways. This is referred to as the N-body problem, and it results in the orbits changing over time, in many cases oscillating in eccentricity, and perhaps also a precession of the orbit, meaning the direction of the ellipse's long axis can slowly rotate. Newtons laws of motion and universal gravitation were still decades away.

(As an aside, my ship is named Astronomia Nova, after Kepler's book)

EDIT: Aside #2: Elite uses perfect Kepler orbits in the game.

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I managed another 60 degrees last night, ending at 0, 11. Just 60 degrees to go! I think I'll make a serious stab at completing this today.

The reasons I'm moving faster toward the end are many:

* I'm getting better at keeping my speed up without spinning out so often. Fewer unplanned stops.

* I'm full on the easier materials to collect here, and the others are just scarce, so I'm not hunting down rocks very often.

* The night side is dark. Since there's not as much to see, I'm not as compelled to explore the terrain and look for scenery.

* I get into a good rhythm, and just enjoy the drive.

* The last few nights I had a bit more time to devote to it, than I did at the start of the journey.

Some of the usual wreckage (again, no actual duplicates, I'm just posting one picture of each wreck):

And I have no idea what happened here. No wreckage exactly, just some small debris. But a whole bunch of occupied escape pods:

Stopped for the "night" close to dawn. The star's corona has been visible for a short time now.



Sir Isaac Newton brought further understanding to the orbital motion of the planets, beyond the pure elliptical mathematics that Kepler described. As previously noted, Kepler didn't fully understand why the planets moved as they did, and only postulated the existence of forces acting upon them.

Newton came to the conclusion that all objects in motion, whether it was the orbit of a moon or planet, or an apple falling from a tree, must follow the same principles. Previous Aristotelian lines of thought had assigned different rules and types of motion to different things. Newton shifted the overall scientific perspective to unified patterns in nature.

In his book, Philosophiæ Naturalis Principia Mathematica ("Mathematical Principles of Natural Philosophy", often simply referred to as Principia, pronounced with a hard-C, and published in 1687), Newton laid the foundations of classical mechanics, and proposed that all matter exerts a gravitational force that attracts matter toward its center. The strength of this force depends on the mass of the object, and weakens with distance.

In a famous example, Newton created a thought experiment with the idea of climbing a tall mountain, above the atmosphere, and firing a cannon parallel to the ground. He proposed that as the power of the shot increased, the cannonball would travel further with each shot, and that there would be a speed at which the trajectory of the cannonball would match the curvature of the planet, returning the shot to the point of origin. This would effectively create an orbit (diagram below).

Newton's laws and equations worked so well, that they are still used today as classical mechanics, and the foundation of modern classical physics.

Newton's laws of motion and universal gravitation seemed to complete the entire picture of how objects move through space, and how gravity works. But this too was incomplete. Astronomers began to notice something odd about the planet Mercury. Even after taking into account the influences of all of the other planets in the solar system, the orbit of Mercury seemed to precess (rotate) more than it should. This anomalous effect was measurable, and could not be explained away until a new, additional theory came along.

Thanks, commanders!

I'm somewhat embarrassed to admit I haven't had it above 20 yet, and I'm often running at 10-15. More practice required!
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