8

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.

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

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

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    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 it’s either that or ... yeah, not everybody’s good at thinking about physics. – almost.time Feb 9 '16 at 23:35
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    i guess the weight only affects those that tries to carry it directly but since rory is the one holding it, the weight returns to normal? – Bahamut Feb 10 '16 at 3:14
  • Another possibility is Gate's world has a smaller gravitational pull than earth's (9.81ms^-2), thus, the halberd would weigh lesser over there, allowing Itami to carry Rory with the Halberd. Also, during running, the momentum of the Halberd is countered by the resistive forces involved, partial vectors of upthrust are amplified, this would also contribute to helping him lift Rory with the Halberd. Plus, Itami has Ranger and Special Forces Training, so he is stronger than the average person. – Astral Sea Feb 10 '16 at 6:45
  • @AstralSea I actually don’t think so. If the world beyond the “Gate” had a different gravitational pull, then those ballistic tests and presentations they did in episode 14 would have gone horribly wrong. (Same applies to regular bullets, rockets, tank shells … any kind of ballistics really.) Less gravity would also mean that this world shouldn’t be able to “lock” the same “level of atmosphere.” (If one can call it that …) This would lead to thinner air and less atmospheric pressure, but we’ve seen characters traverse between the worlds without problems. – almost.time Feb 10 '16 at 17:07
  • @almost.time I have posted an answer to just explain that my theory is within the realm of possibility as physics is a delicate subject so even a small difference of 1N can lead to a large change in experimental results. – Astral Sea Feb 11 '16 at 9:47
5

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

ge=9.81ms^-2

gg=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.
  • We assume Rory weighs about 50.0kg (Average 14 year old)
  • Itami is a Ranger. Thus, he should be able to lift up to 170.0kg (below average for a ranger). According to this website, 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(gg), which lowers (Rory+Halberd)'s weight from 1471.5N to 1470N so weakened Itami can lift them.

gg=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'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 is 2,438 meters.

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 for air density at 2000m above sea level.

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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 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

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, 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.

3

In canon, it is unexplained. But the explanation by user 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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