What could people notice about someone who is two times as dense as a regular person?

Question

I've got a group of magical people living mostly incognito in an ancient society. They look and act exactly the same as regular people, but they are really magicians, and a side effect of having those powers is that they are two times as dense. E.g. a lithe woman who looks like 50kg/110lbs would really weigh 100kg/220lbs. They've got twice the muscle strength to compensate, but the mass is still there. It is congenital, they are born that way (perhaps even since conception).

What are things people could notice about them? It's not enough extra weight to make them fall through floors, but sitting on one end of a boat betrays them as it leans over more than it should. I think the extra inertia would also matter in some places, but I'm not sure where.

Answer 1

They can't swim.

Normal humans are just barely buoyant enough to float in water. We need to generate some hydrodynamic lift to get far enough out of the water to breath.

The average human body has a relative density of 0.98 compared to water. Your humans would have a relative density of 1.96. That means while a normal human swimmer just needs to create a little bit of hydrodynamic lift in order to get their face high enough out of the water to breath, your dense humans would need to support half of their whole body weight with swimming motions.

To get an impression of how difficult that would be, imagine trying to keep your head above water while there is another person of the same weight as you standing on your shoulders. Even if you were twice as good of a swimmer, that would be impossible.

Normal people can't do that and your people wouldn't be able to do that either, even with twice the strength. They would sink like rocks. It would be next to impossible for any bystanders to get them back to the surface before they drown.

For that reason you will likely not get them into a boat. They would know that being so close to deep water would put them in mortal danger.

You would notice if they compete in contact sports

In sports like wrestling or rugby, a trained athlete quickly learns to judge the momentum of their opponent by how they look. This skill is crucial if one wants to succeed. When their opponent is twice as heavy as they should be, they will notice. A professional might even notice when they observe a match where one participant is heavier than they should be.

Answer 2

A number of common situations could give them away.

If you ever paid attention to people getting in and out of your car, you notice that it shifts by noticeably different amount depending upon the weight of the person. Maybe the fact that I notice this makes me a bit of a rarity.

But there are other small things. How loud a floorboard or chair creaks. How much a cushion or mattress compress.

Again, these may be subtle, but the brain is good at pattern recognition -- and although you may not notice these things in in normal people, does not mean you would fail to recognize the exception to the pattern for high-density people.

Of course, early in-life people weigh babies, hold them, and even pass them around to friends and relatives. This would be instantly noticeable and all high-density people would be detected as infants.

If high-density people don't realize their condition, they would be detected in medical exams. Or broken toilet seats, chairs, etc. as they would not expect to cause damage by simple actions. If they try to conceal their condition, it will be harder for others to detect of course.

Answer 3

In addition to the answers listed, here are some more things that these people will need to be careful about, otherwise it could put them in a situation that could result in their exposure:

Speaking

Their vocal cords are also twice as dense. The length, size, and tension of the folds in the vocal cords affect the pitch of ones voice. It is doubtful that the tension will go unchanged as a result of the density doubling. Unfortunately I could not find any studies on what happens if you change the density of the larynx. So, I cannot say for sure if it would cause them to naturally have higher or lower pitch voices. For example, if the density increases the tension, then it will cause their voices to have a higher pitch. If they get scared or excited it would increase the tension even further, resulting in them hitting some rather high pitch notes you would not expect a person to reach (specially if it is a man).

Getting Their Hair Cut

Their hair is going to be twice as dense as regular hair. Any barber or hair stylist will notice something is wrong. Specially when their scissors or clippers start having trouble cutting through their hair or become blunt faster. They might not be able to conclude that the person is twice as dense, but they will know something is different with these people.

Corset and Brassiere Problems

Corsets, brassieres, and other types of clothing are designed and intended to provide women with support. Unfortunately for any women that is twice as dense, means their clothing will need to provide twice as much support. As such the extra unexpected weight could damage corsets and cause more flimsy outfits to struggle and break leading to wardrobe malfunctions. This would not directly reveal them as being more dense, but it could put them in a situation which could easily lead to their discovery if someone tries to help them.

Answer 4

Besides what everyone has already said: their steps would be generally louder. They would impact the ground with twice the energy on each step, for the same footfall used by a person of regular density.

Also, they would be putting twice the pressure on the ground when standing. Their feet will sink a little bit on beach or desert sand. Their footprints will be deeper in any soil. And on snow, depending on the environment, they might sink anywhere from less than an inch to more than their full height depending on how compact the snow is.

Answer 5

They would also likely need to consume a fair chunk more food to account for the increased energy needed to move. You mentioned the extra inertia, well coincident with that is larger amounts of energy needed to move, such as in kinetic ($\frac{1}{2}mv^2$) and potential ($mgh$) energy.

Or else they'd become tired and start losing weight/look emaciated.

Certainly the existing range in metabolism may make it difficult for many notice, similar to Gary's answer. Indeed I've certainly had "smaller" friends who ate nonstop, weren't all that active, and somehow didn't gain weight. But it might at least make people suspicious.

You could use this calculator to get a rough idea of how much additional energy consumption would be needed.

Answer 6

Physical contact between humans is not rare, especially on sports teams but also in other social situations.

• High five: normally the momentum of both people's arms cancels out. It might be possible to simulate a less dense arm by using your muscles, but even this could give you away.

  A simple hand-shake might not be a give-away if the person is well-practiced at making their hand easy for the other person to pump up and down. Sometimes a handshake starts with a slap or hand-clasp that could give it away.

• Hugs, especially a "man-hug" that starts with a handshake and involves pulling the other person in until you bump shoulders. The other person's inertial mass is readily apparent. Illustration from this article:

  Holding someone's shoulders as you greet them with air kisses next to their cheek (like in some parts of Europe) might give things away. The more touchy-feely the culture, the harder it will be to go undetected.

• slap someone on the shoulder or give them a friendly push: if it's at all forceful, you expect their body to move some.

• non-friendly pushes or fighting: it will be very obvious if you punch, push, or kick someone. Physical play between children might not be a "fight" per-se, but any kind of roughhousing will be a giveaway even to other children unless they're very young.

• dancing with a partner: you don't push/pull your partner around the dance floor, but I think you would notice the difference just touching them while they move. Any "spin your partner" move where you hold on to each other and spin around a common centre of mass would be a dead giveaway.

Even in non-contact sports like Ultimate [frisbee], it's not rare to accidentally bump in to someone. A factor of 2 mass increase will be very obvious. You'll bounce off and they'll barely move.

At walking speed in a crowd, you sometimes jostle with other people a little bit, and even that could be enough to notice something was weird.

If a dense person is trying to stay undetected, just being physically near other people is a big risk. You never know when one will bump into you accidentally or touch you on purpose and notice the difference.

If you slip and someone tries to help catch you, they'll notice. If someone thinks you slipped or might need help, they might grab your hand and notice that it has twice the inertia it should.

Answer 7

They will sink like a stone in water.

I don't think a doubled strength could fully compensate for a doubled density, as the buoyancy force is not doubled. If they can swim at all, it will be obvious that they're making a huge effort just to stay afloat.

Of course, knowing that, and also knowing about drowning, they'll avoid deep water like lava. Especially around outsiders. They won't stand out for it either, since "I don't know how to swim" is a perfectly valid excuse. But any accidents with them falling on water will surely reveal that they sink unnaturally.

Answer 8

You also need to think of things like body heat. You'll have the same surface area through which you emit heat, but you'll have muscles -- and I assume other body/cell functions -- that are emitting twice as much heat. Someone very near to or touching you would feel the unnaturally high heat. Perhaps your metabolism could somehow be twice as efficient, but... (Also, if your metabolism is higher, even things like breathing would be an issue, since you'd need more oxygen but you have normal-sized nostrils and lungs, so you might be "out of breath" a lot.)

In terms of your remark on inertia, imagine bumping into a normal person on a sidewalk -- a situation where extra strength wouldn't help them because you wouldn't have time to use that strength to oppose your inertia. People would naturally assume from the force of the impact that you purposely put your shoulder into them. And this is assuming you possibly could use your strength to modify the situation, so imagine a situation where you're ballistic -- jumping, falling -- where no amount of muscle action could compensate. (This would apply to accidental impacts with anything, not just people, so you would be more likely to knock things over or destroy them if you bumped into them.)

You would also wear out horses pretty rapidly as an adult. I don't think horse stamina falls off linearly, so you'd wear out a horse more than twice as fast as someone else of your size. And your horse would generally be slower than those of any companions.

Answer 9

In the movie Shallow Hal, Jack Black's character sees a woman who is extremely over weight as skinny an petite.

Some things the film did to show his perception of her wasn't accurate-

• Getting in to a car, it sinks much more than her weight would suggest it should.
• A chair that looks like it could easily manage her weight fails under the stress.
• After she gets out of bed, Hal rolls over to where she was laying and falls into a deep recession in her mattress.

Answer 10

They would eat a lot

You could expect these people to need many more calories than a normal human. It takes energy to start and stop the additional mass, even if the enhanced muscle ability make the movement look completely normal. Additionally, even at rest, muscle take more calories to maintain than other tissues in the body. I imagine the enhanced muscle would need a similarly enhanced flow of calories in upkeep.
Net result: these people probably spend much more time eating than others, or possibly would only eat calorie dense foods

Note: a similar effect might be found with their breathing. Even a professionally athlete is going to get tired and breathe heavily if they carry around another person's weight all the time. Lung capacity / efficiency might increase to compensate, but if it plays out like this, I think it unlikely that these people would spend much, if any, time at high elevation where the air is thinner.

Abnormal body temperature

Or at least, that's how it would likely feel. I'm interpreting twice as dense to mean that there's literally twice as much physical stuff in the same space. This would mean there is effectively twice as much surface area for purposes of thermal transfer.
Net result: with any physical contact (say, shaking hands, for instance) both parties would feel any temperature differences much more acutely. It's possible these people would have constant hot/cold hand syndrome, or at least be perceived that way by normal people.

No static electricity(possibly)

Higher material density decrease electrical conductivity, all other thing bring equal. (I'm using compression of air as a logical reference point, so this might not even apply since people are made of solids and incompressible fluids). These people would effectively be electrically insulated.
Net result: tasers, Van der Graff generators, etc might not work as well on these people. It could also protect them from electrical magic you have them wield, if that's a thing in your world.

They don't get sick

Traditional diseases rely on germs bring suspended in a person's blood or cells. If these people are twice as dense, this simply would not happen. It's like the swimming problem in the other answers, except in reverse. Normal diseases would simply float and collect in certain points of the body where they would be quickly eliminated. If magical traits are at all genetic, you could expect their immune system to eventual center around (or even create) these points. Perhaps the magical community have their own unique set of diseases that normal people can't get?

Deep footprints

This one is pretty simple. Heavy people would displace more dirt/mud when walking

Biological waste

If everything in their bodies is twice as dense, it's fair to assume that their... excrement would be as well. This would create a problem if they needed to use modern plumbing, as it's entirely possible moving water would simply not have enough mass to clear a toilet bowl.

Note: hair is interesting to consider as a non living component of a person. Either the hair is just as strong as normal (limiting it's length due to the extra weight) or it doubles in strength like everything else so it would look sort of normal. Sort of, because if it's denser, it wouldn't blow in the wind as much as a normal person's. It's possible normal people would want to use it for making rope, given its strength. Or if it is just denser but not stronger, normal people might grow their own hair past that point to prove, immediately and visually, that they are not magical (useful for a diplomat, say for instance, since the couldn't then be a magical assassin)

I'm sure there's more, but that's all I can think of off the top of my head. Cheers!

Answer 11

You would notice the difference in children at a playground. Almost all playground sets use weight as a factor of play with the exception of the climbing sets.

Sets like the swings, seesaw, rope bridge, bouncy horses and the roundabout. You could see the difference if a children who was twice as heavy played with a normal child on a set.

A person with a keen eye could even spot the difference in the sand as the children ran and jumped.

Children could also not play contact sports like soccer, football, rugby or basketball without revealing their weight difference.

If a segment of the population was prosecuted for this difference, then it would be interesting to see how places like playgrounds would change. Instead of being an open place at the park and welcome to everyone. There might be police there keeping an eye out for heavy children. We might find that strange, but for parents living in that world it might be a necessary thing to ensure their children are safe.

Answer 12

The every day sign, especialy in an ancient time.

Chair, Ladder, and Car:

Every things is build and design with a weight limitation. Take a good old wooden chair, A average man of 80Kg will not break a chair by sitting on it. A Dense Joe will easy break it, especialy if he give it a little swing. For a 50Kg woman the sign will be the floor wear. In ancient time floor were wood or dirt, this will be easly noticable.

For bench, once a normal man sit down, a dense one can catapult him just by sitting to fast or getting up too fast. If he goes slowly you will notice the weigth simply by the bench vribration and bend. On a bench you can notice if a kid(light) or an grown up sit on it even with your eye close.

For car and transport, this will be fun. They will either break the horse back or make a noticable shift in the car balance. Old vehicule don't have the sweet car suspension we have now. And even car suspension will give them away, same test for bench close your eye and ask someone to sit next to you. You should be able to tell witch is 50kg or 100Kg.

Ask Dense Joe to use a teen bicycle for fun.

In general every they use will wear faster, If those dense live together like a familly they should not invite people home.

When we build thing we trend to build them so they can be use in normal usage. 2 people usage instead of 1 is more than -50% life time, it could be imediat failure. Things like ladder won't like your Dense Joe.

The one that don't Knock:

They also never knock on door. You can have physical expectation when earing a door knock. You will notice that the 50 Kg girl knock like a 100Kg man.

Dense Joe don't drink booze:

There is nothing that test its own inertia on object like a drunk man. Any one that even encounter a drunk Dense joe can tell: "You don't pick them up."

Dense Joe sleep on the floor:

He will tell you that it's good for hes back. But Dense Joe simply break the bed every time. (50kg+80kg)x2 in the middle of the bed.

Answer 13

They'd ask you to speak louder. Their denser ear and bone tissues would require a higher sound frequence in order to perceive clearly our speaking. Also, while eating, they should pay more attention if eating meat with bones. They could accidentally shard a bone and end up with mouth wounds.

Answer 14

Any time they need to get on a vehicle—in an ancient society, probably some kind of cart or chariot—or ride a horse, it will go much slower than it should. And if you know how much your own horse can carry, you’d at the least be worried that something’s the matter with your horse. In any situation where you have to balance a load, say by putting two people the same size on opposite sides of the cart, it becomes obvious that it takes twice as much weight as it should.

Someone who knows the strategies wizards use to stay inconspicuous might therefore look for the person who always makes very sure to sit in the middle of the wagon, not on either side, but also to sit directly over the legs of a bench, not in the middle.

Answer 15

They would need to eat more for the same growth (unless the extra weight magically clings to them upon absorbtion in the body).

Besides swimming, they would have trouble jumping/falling and have a lot of problems with steep stairs or climbing up/going down. Even with double muscle strength and equivalent bones, the impacts would be immense and because they have twice the mass but the same shape they would accelerate to terminal velocity twice as fast (and have higher terminal velocity), so their bones and muscles would need to be about 4x stronger for the same height jump/step.

They would basically move around the world like geriatrics. A simple stumble can break their arm or leg. A crash with a car (or even a simple bicycle) would be lethal far sooner. In reverse, it takes more force to start moving their body so you need something bigger to hit them and get a damaging response. Even that has downsides as you'll absorb more energy in less time as well.

Answer 16

I thought I could write something about how changing direction (walking around a corner) would look weird, but turns out that since F = m * a is a linear relationship between force (twice as strong) and mass (twice as dense), so they should be able to accelerate/decelerate just as normal people do.

They also likely won't skid when trying to slow quickly, since friction is calculated as F = u * m * g, so the available friction to excert the force needed to decelerate them also grows linearly with the mass.

Thus, the only new thing that I can still mention is... That they would buy very sturdy shoes (nothing with a middle sole that would be compressed by their extra weight, ruining the shoe quickly, or a sole profile that would suffer similarly) and would have to replace them more often than normal since all that extra friction they need to accelerate/decelerate with every step will eat the rubber quickly.

So, people could notice strange (footwear) fashion choices, and a quicker-than-usual (for this kind of shoes) need to replace them. Might be something that makes for an amusing quirk to their friends :)

Answer 17

Playing contact sports

If they played say gridiron or rugby, they would be like the bowling ball and normal people would be like bowling pins.

Footprints in sand

They would leave much deeper impressions is sand (IIRC the depths is proportional to the square root of the weight of the person - citation needed)

Martial arts

Especially sports like Judo - attempting to throw someone of twice the mass as you expect to the floor wouldn't work so well

Anywhere you are weighed

When flying in commerial light aircraft (less than about 20 passengers), they weigh you beforehand so they can distribute passengers mass evenly in the small cabin to provide safer flying

Jockeys, boxers, etc are also weighed

Answer 18

They will have significant problems walking on non-solid grounds.

Since their feet sizes are the same, they will be applying twice as much pressure per foot than a normal person.

If they walk on soft ground, they will sink much further in than the next guy of the same size. Assisting them out of the hole will also reveal their extra weight.

Answer 19

To the other excellent answers I would add that there are a number of areas where the difference in inertia would be apparent.

Any sport that involves sudden stops and starts like tennis or baseball would be affected. More dense people would slide farther. (There's a whole science of mastering sliding on clay or grass courts.) Dense children would be at a disadvantage in games like tag.

I don't know about the climate in your world, but if they do things like sledding, ice skating or skiing I think the difference would be noticeable.

Their greater strength would be apparent in tasks that don't involve moving around much of their body weight. If I understand correctly, their legs would be strong enough to jump about as high as a normal person. That means that their kicking power would be much greater. If they can do chin-ups as well as a normal person, they would be great at arm-wrestling.

Magicians would probably be very picky about footwear. Unless their feet were magically tough, they would be more prone to foot problems due to twice the weight being spread out over the same area. Sitting on a hard bench would be twice as uncomfortable. Falling would hurt twice as much.

Answer 20

One slightly unfortunate impact would be on social activity.

• Raves/dances - a bunch of these people dancing or jumping (social or to escape something) on the floor above you.... Crunch?

• Sex - uh oh! Those forceful passionate quickies will have to go. They'll probably have enough inertia/momentum to break shower panels/tiles, destroy car suspension, crack thin dividing walls between hotel/motel rooms, and break beds. They'll have to be gentle and languid!

• Running - you run, you tread on a plank or paving slab, and it has to withstand twice the impact force. Crack!

• Scuba - requires strict control of weight neutrality using belts around the waist.

• Lifts/elevators/escalators/hot air balloons - have weight limits. Oops!

Answer 21

Alcohol Tolerance

A dense person has more tolerance for ethanol and will take more booze to get drunk.

For a real-world example consider Andre the Giant.

It has been estimated that Andre the Giant drank 7000 calories worth of booze every day. That's about 46 beers a day.

Andre the Giant once admitted once on Letterman to having consumed 119 beers in a single sitting and passed out in a hotel hallway, and that wasn't even his record.

from https://www.stuff.co.nz/entertainment/celebrities/82494695/

Admittedly he was physically big as well as muscular, so the quantity of fluid vs the potency of the alcohol content could be a factor. That is, fitting a lot of beer inside the torso could be a challenge so they'd prefer higher-proof spirits.

Answer 22

Just another addition:

Put them into / onto any vehicle such as a car or a motorized bike that has suspensions

In 'X-Men Origins', Wolverine, now with a freshly adamantized skeleton, gives himself away by just sitting on the motorbike and pressing it all the way down due to his unusual weight.

Answer 23

If they are a secret society, then definitely you will not know to look for such signs to recognize them. As well they likely use magic to conceal.

Additionally imagine in a technocrat society nobody would believe any strange signs. Most people would rather think they are going crazy than thinking the other person is a magician.

There was an old movie where a robotic young man/boy went to college and there were all sorts of funny moments when others hit him, the bed broke, etc. I don't remember the name of the movie but you can search for it.

Update: I think movie was "Still Not Quite Human"