#mahri-nui

[rahiwatching]

BIONICLE Science: The Depth of Mahri-Nui and the Length of the Cord

This is the second in a 5-part series of interconnected BIONICLE Science investigations that all feed into each other (the other parts will all be included in my BIONICLE Science master post).

After answering the question of the size of Voya-Nui (see this post), I turned my scientific sights onto Mahri-Nui: How deep underwater is it? And how long is the stone cord that connects it to Voya-Nui above?

Returning to the scale map of 2001-2008 locations from the previous post in this series, we can clearly see that the cord is depicted, a line extending south east from Voya-Nui to Mahri-Nui in the ocean depths.

Of course, this line only shows the Cord as it appears from directly above, it doesn’t show us the true length of the Cord or how far below the surface it stretches, it only shows is the straight-line distance between Voya-Nui and Mahri-Nui. But that is still a key piece of data to gather in order to uncover the wider question.

Using the same pixel measurements as before, this distance works out to be 30 pixels, or 43.2km when scaled up.

Now that we have that distance measured, we actually only need one other measurement in order to find both the length of the Cord and the depth of Mahri-Nui, and that is the angle at which the Cord is oriented relative to the sea floor (here, we are assuming that the Cord is a completely straight line, something that is backed up in its various depictions in canon).

Once we have that, we can form a right triangle and from there use a bit of trigonometry to find both its height and its hypotenuse – the depth of Mahri-Nui and the length of the Cord respectively. 

I took the following image of Mahri-Nui from the ones available in order to make this measurement, as it is the best image available to show the city and the cord directly side on, meaning there would not be any viewing angle issues that may affect the angle measurement.

 Measuring the angle of the Cord relative to the horizontal plane, the Cord is pointing upwards at an angle of just over 59 degrees.

Now all that’s needed is to plug this angle and the measurement for the base of the right triangle (43.2km) into the trigonometry equations and we can find our answers.

 The height of the right triangle – the Depth of Mahri Nui:

Height = 72.9456511km (or 72.95km when rounded to 2 decimal places)

The hypotenuse of the right triangle – the length of the Cord:

Hypotenuse = 84.77809061km (or 84.78km when rounded to 2 decimal places)

 Mahri-Nui is deep. Incredibly deep.

On Earth, the deepest known point of the ocean is the Challenger Deep, a smaller trench within the larger Mariana Trench in the Pacific Ocean. It has been measured to be 10,929 meters (10.93km) below the surface.

Mahri-Nui sits 6.67 times deeper than the deepest point in the Earth’s Oceans!

This is even more impressive when you remember that Mahri-Nui does not sit on the true sea floor, but actually on top of the sediment covered body of the GSR, meaning that the Ocean of Aqua Magna is even deeper than this! While this is an incredible depth of the scale of the Earth, it is not unprecedented. The size of the inferred subsurface ocean on Jupiter’s moon Europa is estimated to be between 60 and 150km deep, so this depth is not impossible.

One thing is for sure though, the Black Waters surrounding Mahri-Nui would certainly live up to their name. Water absorbs light as it passes through it, meaning that the deeper you go, the darker it gets. This absorption rate is exponential with more and more light getting absorbed with every meter of depth. With the intensity of sunlight on Earth, this means that beyond 1000 meters in depth, essentially no light from the surface penetrates the ocean, leaving anything there in darkness. Mahri-Nui sits over 70 times deeper than this. Even assuming that Solis Magna has a higher luminosity than our Sun doesn’t help due to that exponential decrease, Mahri-Nui is just too deep.

Without Lightstones, the Black Water would be dark indeed.

In terms of the length of the Cord, it appears from canon that the Toa Inika took a few days at most to travel down its length, with various battles etc. along the way slowing them down. The inside of the Cord is also described as having many twists and turns, so the actual distance traveled by the Inika in that time would have been larger than the 84.78km that the Cord appears to be from the outside.

If we assume a steady walking pace of around 5km per hour, it would take around 17 hours to complete a journey of approx. 85km, so taking the various stops for battles with the Zyglak, stops for rest, and the longer actual distance due to the labyrinthine nature of the Cord, a travel time of a few days is reasonable.

I was pleased with these results, but my brain still wouldn’t let me finish on this line of questioning just yet. If Mahri-Nui doesn’t sit on the true sea bed, but rather on top of the GSR, then how deep does the ocean of Aqua Magna really go? And given just how much water pressure increases with depth, how much pressure are the Matoran subjected to down there?

If you want to know the answers to these too, stick around for parts 3 and 4.

[mask-of-prime]

Took me way too long to realize that Voya-Nui is supposed to be that atoll-looking island in the Mariana Islands and that Mahri-Nui is supposed to be the Mariana Trench

Oh... and Mariana..... Mahri-ana

[kanohicafe]

2007-2017 : SINK OR SWIM #12 - Reysa (Rough)

[rahiwatching]

BIONICLE Science: Water Pressure at Mahri-Nui

This is the third in a 5-part series 6-part series (guess who thought of another connected question to answer?) of interconnected BIONICLE Science investigations that all feed into each other (the other parts will all be included in my BIONICLE Science master post).

In the last post I determined that Mahri-Nui sat 72.95km below the surface of the Aqua Magna Ocean and I wondered, what kind of pressure would things be under there thanks to having that much water above them at all times? That is what this post is here to find out.

The equation for water pressure at a given depth is fairly simple:

The density of water is 997kg/m^3

The depth of Mahri-Nui is 72.95km or 72950m

The acceleration due to gravity on Aqua Magna is 4.84m/s^2 (as determined in my Science of Spherus Magna paper).

Therefore, by plugging all of these numbers into the above formula, we get a pressure around Mahri-Nui of 352,018,766 Pa.

Let’s put that into context. As discussed before, the deepest point of the Earth’s oceans is the Challenger Deep in the Pacific Ocean. We already know that Mahri-Nui sits 6.67 times deeper than this point, however we also know that the acceleration due to gravity is stronger on Earth than it is on Aqua Magna (9.81m/s^2 vs 4.84m/s^2) – so how do the two pressures compare?

The measured pressure at the Challenger Deep is around 116,000,000 Pa, meaning that the pressure at Mahri-Nui is 3.03 times higher than at the deepest point of Earth’s Oceans.

That is a very high pressure to be living under. It is the equivalent of having 35,895.74 metric tons of weight resting on every square meter. Or to put it another way, it is like having the weight of 239 Blue Whales, all stacked on top of each other, for every square meter of surface.

However, even in the crushing pressures of the Challenger Deep life can still be found, ranging from microbes to marine worms and sea cucumbers. If organic life can evolve to handle the pressure at that depth, then it may be reasonable that biomechanical life (which should be far hardier) could exist at 3 times that pressure. The biomechanical beings we see at this depth may have also been given a helping hand in being able to survive these pressures. The Toa Mahri were given transformed bodies by the Mask of Life to allow them to survive in this environment and all other biomechanical beings we see here were in some way affected by the Pit Mutagen (even the Matoran to a small degree) and we know that the Mutagen changes biomechanical bodies to be able to survive underwater, so an ability to survive the intense pressures here would likely be part of that.

It is even not that unreasonable to suggest that the organic life found around Mahri-Nui, such as the Sea Squid, could possibly survive at these pressures. While an extreme example, microscopic Tardigrades here on Earth have been found in experiments to be able to survive pressures of six times greater than that of the Challenger Deep, twice what is found at Mahri-Nui (admittedly the experiments only tested this for short periods and they are hardly on the same size scale as a Sea Squid, but still, life finds a way).

So, there you have it, the intense pressures found around Mahri-Nui revealed. Next up, we will look at just how much deeper this ocean goes…