In his inaugural post, PVL Summer Undergraduate Michael Tabascio takes a look at a most unusual crater that appears in popular culture, on the map of the game "fortnite" as pictured above. As frequent readers of this space will appreciate, I think it's absolutely critical to bring the public along for the ride that is planetary exploration. As such, depictions of planetary processes like these offer a unique opportunity to connect our work with that public experience and to deepen the appreciation of both perspectives.
By Michael Tabascio
Fortnite is a hunger games style
third person shooter has taken the world by storm, with the objective to be the
last one alive by eliminating your opponents. It can be said with great
assurance that Fortnite is the biggest game of the year, with the map evolving
every couple months. Perhaps the most notable change came in May, when the map
was struck by a meteor leaving a gigantic crater in the middle of the map. Using
the dimensions of the crater, the direction and angle of the meteor, as well as
the material of both the meteor and the ground beneath it, we can estimate what
the size of the meteor was that hit the map.
A few
assumptions will need to be made prior to beginning. The game Fortnite takes
place on Earth and shares the same direction of rotation and gravitational
acceleration as Earth, and that the material found in game has the same
properties that it would have on Earth. Using a JavaScript program developed by
Yogsther[1] we can determine the diameter of the crater. The program
works by calculating the time it takes to run across the marked distance and by
knowing the speed at which the player runs at, we can work backwards to find
the distance. Fortunately, the crater is circular so there is no change in
diameter. From the program, the diameter of the crater is determined to be 270
meters.
On the map there is a tail formed
when the meteor hit, meaning it did not travel straight down to the surface
(i.e. 90 degrees to the surface).
Only for extremely low impact angles, much less than 30ยบ from the horizontal, where the impactor seems to be
“grazing” the surface, will a non-circular shape be produced. For these craters, the ejecta blankets appear on
the sides perpendicular to the direction the impactor was travelling giving it the
appearance of butterfly wings (figure 2).
Since in our case the crater is fictitious and
was made most likely by imitating the general look of a crater, rather than the
outcome of the meteor hitting at a specific angle, we will use some simple
trigonometry to estimate an impact angle. In the game there are walls that can
be placed during the game to shelter your player from gunfire, but in our case,
we will use them to estimate the impact angle of the meteor. Assuming each
wall is 1 storey or 3 meters, 8 walls are needed to reach the top of the crater
from the bottom, giving us a crater depth of 24 meters. Using the JavaScript
program again, it is determined the tail begins 120 meters away from the
crater. Knowing these two lengths, we can use the tangent ratio for right angle
triangles find the impact angle, which turns out to be approximately 12°.
The average impact speed of asteroidal terrestrial impactors is
approximately 17 km/s. As the meteor hit the map, it left debris that could be
salvaged by players to use as material to build walls as discussed earlier.
When mining the rocks left by the meteor, players gain material in the metal
category, in which the emblem associated with metal is an iron bar. We will use
this information to assume the meteor was made of iron which has a density of
8000 kg/m3. Finally, it can be seen from the crater that the ground
where the meteor hit was made of soil and clay, much like Earth, which has
density of 1500 kg/m3.
We now have
all the information we need to estimate the size of the meteor. For this I will
use a program available on OpenLearn[2]. The size is calculated by
using the kinetic energy equation (E = 0.5 m v^2) where E represents the amount of energy in
Joules, m represents mass in kg and v represents velocity in m/s. The energy is
found by comparing the crater size to craters made by explosives, where the
energy released from explosives is known. We know the speed at which the meteor
impacts the ground at and can work backwards to find the mass. Plugging in the
information we found, it was determined that the meteor that hit the map was
approximately 7.02 meters in diameter, which is consistent with the video released
of the meteor hitting the map.
Fortnite is
a game that is continuously evolving to appeal to the gaming community and it
is only a matter of time before another event like this occurs, in which case
the science community will be thrilled as it provides more opportunity to learn
about impactors. Note, no people were harmed during this study other than the
people who tried to kill me while I was gathering information.
Figure 2: A picture of
an impact crater on Mars created from an extremely low impact angle, as described by Emily Lakdawalla (http://www.planetary.org/blogs/emily-lakdawalla/2011/2894.html ). Note how the crater seems
tear dropped shaped rather than circular and how the ejecta dominantly spreads
perpendicular to the impact, creating the effects of butterfly wings when
looking straight down.
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