

In episode 8, it is revealed that Rory Mercury's halberd is extremely heavy.

The thief who tries to steal it collapses and is crushed by it. And when
Hideyo tries to pick it up, he hurts himself.

[![enter image description
here](https://i.stack.imgur.com/O9lC4.png)](https://i.stack.imgur.com/O9lC4.png)

But in episodes 6 and 17, Itami picks up Rory along with her halberd and runs
with them in his arms.

[![enter image description
here](https://i.stack.imgur.com/4FzaD.png)](https://i.stack.imgur.com/4FzaD.png)

What gives? Itami is human. He doesn't have superhuman strength like Rory.


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2016-02-09T23:15:22.020
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2016-08-10T08:15:20.507
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question
gate
If Rory's halberd is that heavy, how does Itami pick her up and run?


In canon, it is unexplained. But the explanation by user
[almost.time](https://anime.stackexchange.com/users/19042/almost-time) is the
closest call:

> I’d consider that halberd more of a GATE version of Thor’s Hammer. If you’re
> not worthy ... you won’t be picking that thing up. But Itami can carry Rory
> around while she’s holding it, just like an Iron Man can throw Thor while
> he’s holding his hammer, but he still remains unable to lift the damn thing
> himself.

So probably her halberd is not of a super-heavy material alloy at all, just
some tool only the assigned users can wield.

Given that Rory is a immortal demi-goddess, that is entirely plausible.

So, from the halberd's point of view, **he is not being carried by Itami at
all**. He is still in Rory's hands. As an Earth analogy, you cannot feel the
Earth spinning around the sun, because you are attached to Earth. So to you
(or to the Halberd), the fact that another entity (the sun or Itami) is
carrying your bearer (Earth or Rory) is either unknown, unmeasureable or
irrelevant.


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answer


To prove my theory of reduced gravitational pull, I will bring in some data
and only use 1 simple equation: **F=mg**

**g** e=9.81ms^-2

**g** g=gravitational pull in gate's world

Data:

  * Average BMI for a 1.9m (Itami's height) tall person is 23, thus the mass of the person is 83.09kg. Thus, we assume this average person can only lift 90.0kg (above average).
  * We assume Rory's halberd is 100.0kg, far too heavy for that thief and Hideyo to lift. Rory can lift it as she has [Superhuman strength](http://gate-thus-the-jsdf-fought-there.wikia.com/wiki/Rory_Mercury#Skills_.26_Abilities).
  * We assume Rory weighs about 50.0kg (Average 14 year old)
  * Itami is a [Ranger](http://gate-thus-the-jsdf-fought-there.wikia.com/wiki/Itami_Youji#Skills_.26_Abilities). Thus, he should be able to lift up to 170.0kg (below average for a ranger). According to this [website](http://www.muscleandfitness.com/workouts/workout-routines/full-spectrum-strong-army-ranger-workout-0), a ranger should be able to lift up to 400 pounds/181.437kg.

Weight of (Rory+Halberd)=(100+50)(9.81) = **1471.5N**

Weight that Itami can lift=170(9.81)= **1667.7N**

Therefore, Itami should still be able to lift (Rory+Halberd) even if he was on
earth. However, we will assume he barely trained after his Ranger training, so
he can only lift 1470N on earth.

Thus, on Gate's world, where the gravitational pull is smaller( **g** g),
which lowers (Rory+Halberd)'s weight from 1471.5N to 1470N so weakened Itami
can lift them.

**g** g=1470/(150)= **9.8ms^-2**

Now, I will prove that this lowered gravitational pull will bring no effects
whatsoever onto firearms and breathing for Earth's people to answer
[almost.time](https://anime.stackexchange.com/users/19042/almost-time)'s
queries. This is due to the difference in **g** being only **0.01ms^-2**.

Firstly, the maximum height that a person can go before having to
[acclimatise](https://en.wikipedia.org/wiki/Acclimatization) is [2,438
meters](https://www.princeton.edu/~oa/safety/altitude.html).

> There are no specific factors such as age, sex, or physical condition that
> correlate with susceptibility to altitude sickness. Some people get it and
> some people don't, and some people are more susceptible than others. Most
> people can go up to 8,000 feet (2,438 meters) with minimal effect.

To prove there will be no breathing problems, I will use data from this
[website](http://www.engineeringtoolbox.com/standard-atmosphere-d_604.html)
for air density at 2000m above sea level.

[![enter image description
here](https://i.stack.imgur.com/xUzPC.png)](https://i.stack.imgur.com/xUzPC.png)

The pressure at 2000m is **7.95x10^4Nm^-2** when **g=9.8**. Thus, at gate's
sea level, the pressure would be about **7.95x10^4Nm^-2** as well this would
mean a person can traverse between the gates without suffering any side
effects as air pressure tends to be almost the same for every 1000m or so.

> For firearms, they can [fire without
> oxygen](http://www.livescience.com/18588-shoot-gun-space.html) but they will
> most likely leave behind more residue. Furthermore, it you are worried about
> **less air pressure=bigger explosion** , do not fret as the projectiles
> would fly further away than normal due to the lower air density offering
> less air resistance and a smaller gravitational pull retarding the motion of
> the projectiles so its range actually increased. Thus, the mortars they used
> in episode 14 would not have cause possible disasters. Furthermore, a bigger
> explosion would mean more energy is converted to heat and sound energy than
> kinetic energy. Thus, it would actually mean that the weapons are less
> effective in Gate's world compared to Earth as the projectiles now fly with
> less speed than before.

It would seem that reduced gravity is not the only possible explanation in
terms of physics for Itami being able to lift (Rory+Halberd) as I read the
Fire Dragon chapter in the manga and found another possible explanation in
terms of momentum.

[![enter image description
here](https://i.stack.imgur.com/3IWQ9.png)](https://i.stack.imgur.com/3IWQ9.png)

> In this picture, you see that Rory is carried differently compared to the
> anime and this is important as she can be considered a plank while Itami's
> shoulder is the pivot. According to the [Principle of
> Moments](http://physicsnet.co.uk/a-level-physics-as-a2/mechanics/moments/),
> if Rory was exerting an upward force, then she would cause a anti-clockwise
> moment about Itami's shoulder in comparison to the clockwise moment
> resulting from the halberd about Itami's shoulder. If she was to exert
> enough force across her arm to have an anti-clockwise moment equal to the
> clockwise moment caused by the halberd about the pivot, then the resultant
> torque about Itami's shoulder would equal to 0. This means that Itami would
> not have to bear the weight of the halberd at all. Though he has to bear
> Rory's weight, the halberd would not impede his motion at all due to all the
> momentum being countered by Rory and we all know a regular person (using
> myself as an example, I can lift up to 77.5kg) like Itami can definitely
> lift Rory.


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answer