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In my novel, my main character has come from earth to a fantasy world. She has been reborn on an island of giants (10-meter tall humanoids) where everything is scaled up to match what they would look like to a normal size person.

My question is what could my main character look for to tell that she is, in fact, a giant when compared to a normal person in a world that is scaled up to match her size?

I mean that the trees and rocks and everything around her is scaled up, not just the artificial structures. What physical effects could she notice?

There are no normal sized people in this area until much later on as the area that she starts in is completely separated from the outside world.

What may make it clearer is if you imagine that the world is a 10x scale replica of our world and you are viewing it from an outside perspective, what effects could you observe that would give you an idea of the scale of the world that you were in?

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  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$ – L.Dutch Apr 17 at 19:15
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    $\begingroup$ Please clarify what you mean by 10X scale world, many many things in the real world can't be scaled up without drastically altering them. $\endgroup$ – John Apr 17 at 20:07
  • $\begingroup$ Thank you everyone for the answers. I realise now that I have left out some information in the question and also not worded it as well as I could have but I can't change it now without invalidating some answers. I have accepted Separatrix's answer as the surface tension of water is probably going to work best for what I have in mind. $\endgroup$ – Sparrowonfire Apr 18 at 7:50
  • $\begingroup$ Feel free to ask a better worded question with the details. The important point is to detail exactly how you deal with all the impacts of the square-cube law. $\endgroup$ – Martin Bonner Apr 18 at 12:10
  • $\begingroup$ Evil Alien Conquerors reverses this for comedy value. A giant on his own planet is normal size when transported to Earth. Despite all evidence to the contrary, he simply will not accept it. $\endgroup$ – Schwern Apr 18 at 17:34

16 Answers 16

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What you're looking for is largely the opposite of what we saw for the 1mm tall robots.

Surface tension of water is a noticeable thing, there's a clear bulge that would seem smaller than memory suggests it should on any given surface. Of course we're not looking at such a pronounced effect in this case, but it would be significantly reduced.

Gravity would have interesting effects, jumping or falling body height would have a considerably greater impact than expected. The square cube law would make things like sudden changes of direction inexplicably harder.

Assuming it's the same world, your biggest giveaway could be the distance to the horizon. A 6 foot tall person would see a 3 mile horizon, a 10 foot tall person would see a 4 mile horizon. At 10m (32ft) tall they're looking at a horizon distance around 7miles (11km). This is a non-linear relationship, the taller you get, the closer your horizon appears to be. The world seems ever smaller.

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    $\begingroup$ You can also note that mists and rain would seem finer, and splashes would be more frothy that splooshy. $\endgroup$ – Joe Bloggs Apr 16 at 9:40
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    $\begingroup$ @Separatrix If everything is at scale, she would be strill five feet tall. Five exceedingly large feet, though. Like two meters each. :p $\endgroup$ – Rekesoft Apr 16 at 10:39
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    $\begingroup$ If everything has scaled then, vocal cords must have too, this will result in a difference in voice, an immediate giveaway. $\endgroup$ – V.Aggarwal Apr 16 at 11:00
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    $\begingroup$ @Falco, you're missing the non-linear part, it's now only 450 lengths away. $\endgroup$ – Separatrix Apr 16 at 17:11
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    $\begingroup$ You're right, the answer could make that more prominent. The horizon will look as if it is only half the distance away you're used to. So you feel the world is somehow smaller, if you're looking over a plain in good weather. If it is foggy out you're in the mountains or in a big city you will probably not notice $\endgroup$ – Falco Apr 16 at 17:14
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Gravity - Time of fall.

Assuming they live in the same gravitational field as the non-giants then simply drop something and see how long it takes to hit the ground.

A normal human is about $2m$ tall. It takes an object roughly $0.6$ seconds to fall $2m$ in our approximately $10\, ms^{-1}$

A $10m$ fall would take about $1.4$ seconds.

The relevant formula is :

$$t = \sqrt{\frac{2h}{g}}$$

Edit : From discussion in comments, I'll add some explanations.

Even without having previously e.g. dropped things and measured the time to fall you would notice this difference. It would be like watching things fall in slow motion - very obvious to anyone in an instant that something is off.

It might take you a little effort to work out exactly what is causing the "slow-motion" effect you see, but you would get to the fact that you're bigger than you used to be.

This effect would be less noticeable if you were not quite so tall. For example the fall from $4m$ (still twice normal human height) would only be $1.4$ times longer (a change from $0.6 s$ to $0.84s$) and you might not notice that before you mentally adapted to the new environment. But the $10m$ tall human would find the change really big and much harder to "adapt away" or dismiss mentally.

Note that this would also be jarring because your horizontal speed of movement would not seem to change, while time of fall did. Your gait and walking speed might seem more like normal when you scale up size, but you cannot fool gravity, so you'll have a permanent inconsistency between the apparently normal horizontal walking speed and vertical motion. This would be hard to ignore.

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    $\begingroup$ @Pelinore I didn't need to look up any formula - that's pretty basic from the formula for motion in a straight line under constant acceleration and for me it's pretty well hardwired into the brain. You don't need to have preciously done any dropping, but the difference between the fall time for dropping a ball (or bouncing one) is going to be immediately obvious if your protagonist ever did anything like that - it would seem like falling in slow motion). $\endgroup$ – StephenG Apr 16 at 10:53
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    $\begingroup$ It would seem like slow motion, then it would hurt a whole lot more. $\endgroup$ – Separatrix Apr 16 at 11:37
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    $\begingroup$ "It would seem like slow motion, then it would hurt a whole lot more" [+] you should pop that in your answer rather than just leave it in comments. $\endgroup$ – Pelinore Apr 16 at 12:44
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    $\begingroup$ ^ But would it though? time perception is subject to the physiology & current chemical balance in the brain (it seems shorter as you get older) while pain can be massively adjusted depending on the number of nerves & how they're tuned. $\endgroup$ – Pelinore Apr 16 at 12:49
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    $\begingroup$ @Pelinore or else at some time in the past test dropped objects & memorized the results, very unlikely for most I can't tell you exactly how fast my car accelerates, but I can tell you when something is off. Just because I can't put a number to it does not mean that I can't see if it's different. I've done (simple) animation work and it's much easier to eyeball if something is off than it is the figure out what the exact speed/movement should be. $\endgroup$ – Flater Apr 16 at 15:14
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I'm assuming the new giant is made out of materials and mechanics that can support the weight and don't cause problems with the person itself. Otherwise her bones would break more easily (not guaranteed, depends on how much of a giant she is) and she would overheat like crazy (less surface area to lose heat compared to the volume that generates heat).

Liquids have less cohesion. Think of a droplet of water on a leaf, you won't see that kind of thing when you are big as the water would pool more. Blood loss will also be much worse, as you'll lose a lot more and the flow rate will be higher, making it harder for the blood to clot and seal the wound.

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  • $\begingroup$ The OP suggested 10m tall - that's more than 5x an average human. $\endgroup$ – Martin Bonner Apr 16 at 15:42
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My plan is to basically use magic for a localised weight reduction on the giants themselves. They are still physically as dense as they would be but weigh less. The world around them will still have normal gravity.

Will their physical strength be scaled to their inertial mass or their weight? Because you've now made those different (by a factor of ~5 for 2m -> 10m height), to overcome the square-cube effect!!

If their strength matches their inertial mass, they can change direction as quickly as before, but jump very high. (Or lift/throw objects of their own weight very easily.)

If their strength matches their weight, so it's about equally strenuous to stand up, or do yoga / plank / push-ups, then they'll find it much harder to pick up objects of the same apparent size. And they'll find it very hard to get up to speed / change direction when running, with 5x the momentum they're used to relative to their strength.


If they start to notice a discrepancy and try to investigate, they might use a rough balance (like a fallen log) to find something of their own weight.

Or maybe more simply, they will float like a cork in water

Because their gravitational weight is ~5x less than it should be for their volume.

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  • $\begingroup$ Damn, I was typing basically the same answer just now :-P $\endgroup$ – ChatterOne Apr 16 at 12:03
  • $\begingroup$ This is a nice problem, which will be immediately obvious, when you run around or pick anything up. And a factor of 5 will be noticeable! $\endgroup$ – Falco Apr 16 at 17:20
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Health issues, bodily proportions and mass

Depending on how realistic you want it, and how faithfully everything is scaled up, she'd probably find out by the numerous health problems she'll encounter pretty quickly. Undersized heart and undersized joints and bones in the legs for instance. This would be shared by pretty much all living things (trees scaled up beyond the limits of their current biology would either fall or die off at the top).

If we're assuming that things have been scaled up disproportionately to allow for these things not to be a problem, she'd probably notice her legs are proportionately bigger as a start. People are pretty intimately aware of their own bodies' proportions, so changes will be obvious.

The next most obvious thing might be mass. Bigger things take disproportionately longer to accelerate and decelerate due to the square-cube law causing weight to increase at a greater rate than size. Anything she manipulates will feel disproportionately heavier (even accounting for her added musculature). Whatsmore, falls would hurt, so if she tripped and fell she'd be able to work out something was off. Provided she's young and healthy it's not normal to be thoroughly bruised all over from a simple fall.

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The green flash.

Green flashes and green rays are meteorological optical phenomena that sometimes occur just after sunset or right before sunrise. When the conditions are right, a distinct green spot is briefly visible above the upper rim of the Sun's disk; the green appearance usually lasts for no more than a second or two. Rarely, the green flash can resemble a green ray shooting up from the sunset (or sunrise) point.

The green flash is seen at the horizon during sunset/sunrise.

And we know that the distance between the observer and the horizon depends on the elevation of the observer above the sea level.

In principle, if one is laying flat on the ground when observing the green flash, by rapidly standing up another green flash can be observed, because by standing up the horizon has moved slightly farther. This is already cool because one can see 2 green flashes close to each other. However..

For a normal human the height change will be about 2 meters at best, while for a giant it will be 10 meters: this will have a measurable effect on the time separation between the two green flashes, which will have a larger separation than the one measured by a normal human.

By comparing the two time intervals your character can conclude that her body has increased in height.

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    $\begingroup$ To add to your answer, rather than just looking for a green flash, you can instead look at the sunset as a whole. If you were to lay on the ground and wait for the sun to drop behind the horizon, by standing up you would be able to see the sun again. For a 10 meter giant, they would see far more of the sun by doing this than a 2 meter human would. $\endgroup$ – Liam Morris Apr 16 at 10:03
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    $\begingroup$ A nice phenomenon, but I have personally never witnessed it and even if I had I couldn't tell the normal time for it to occur again after standing up. $\endgroup$ – Falco Apr 16 at 17:18
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    $\begingroup$ I think this is a bit of an overcomplication of Separatrix's answer - you can lay down and stand up at any time of day and see the distance to the horizon double. Not much need to wait for sunset, and as @LiamMorris points out, you don't need to count on this uncommonly seen optical phenomenon, just use the sun itself. $\endgroup$ – Nuclear Wang Apr 16 at 18:32
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Small soap bubbles behave differently than large soap bubbles.

Small soap bubbles start out as blobs but quickly form a well-rounded sphere. They then float around with a stable "tight" outer surface.

enter image description here

Large soap bubbles start as amorphous blobs and they stay that way for a while, and even when they start to round off, they are usually only as round as a potato, which is noticeably different than a perfect sphere. And as they float around they continue billowing and changing shape:

enter image description here

This is because of a molecular property of the soap. Unless you scale up the actual soap molecules, this effect will remain. So if your protagonist tries to blow a spherical soap bubble on a whim, it will not look or behave the way they expect, because what they think is a small bubble is actually a giant one.

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    $\begingroup$ "Dude. Why are you blowing bubbles?" / "I think I'm a giant and this is what I came up with to prove it" / "Nah, dude. Bubbles have always been like this!" $\endgroup$ – Beefster Apr 18 at 0:04
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It takes time to send commands and receive sensory feedback along the length of a nerve. Having longer limbs, your character may experience a delay between asking a finger to move and then seeing and feeling it move. Just enough to feel slightly inebriated. They could acclimate to this sensation eventually.

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  • $\begingroup$ Interestingly, slow nervous signal may alter perception of time and that would invalidate one of the top voted answers. $\endgroup$ – Pere Apr 18 at 8:08
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If giant humans are proportionally stronger, and all health & movement issues are handwaved away, there is still a number of things that would give the scale away.

  1. Water tension (already mentioned in the other answers). If water tension remains a constant, it would look very different for 10-meter tall persons.

    • Drops (raindrops, condensed mist and just accidental splashes) would look tiny;
    • Pouring water would look different;
    • Ocean waves would look funny (knee-high surf with "white horses");
    • Just water in a cup would look different - a visible ripple on the surface (while in a human-sized cup water tends to stay perfectly still);
  2. Material toughness. Many day-to-day objects would usually survive 1-meter fall from one's hands with minimal or no damage. Same objects, if scaled up, would shatter if dropped from 5-6 meters. Softer ground would be swallowing giant's feet;

  3. Invasive/migratory species. Are only the "giant" versions of animals allowed on the island? Any normal sized seagull or dolphin would become a surprise.

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Beach Sand

Your giant will see what looks like silt sized particles behaving like sand.

Sand particles can't get below a certain size and still behave the same way. If sand is worn down to a powder like consistency it becomes silt which behaves in different ways, (when wet it can't reflect enough light to look white for instance) if it is worn even more water will chemically alter it into clay. Thus white beach sand particles never get below a certain size. More importantly to have sand dunes you need, well sand, silt will not form dunes. the closest it can get is loess hills which do not happen in wet environments. If your character goes to the beach they will notice the white dune sand looks like powder which can't happen. It is pretty big leap to "I'm a giant" but it could certainly give hem their first clue, and it would be concrete evidence not just a feeling. If they know a little geology it will be a very glaring issue.

If they can get a hold of a strong magnifying glass or low powered microscope they can confirm it is shelly beach sand (made largely out of shell fragments) and thus cant be silt. Finding a bay with normal silt in it will help confirm as well. Sand also behaves differently than silt, a footprint in dry silt will not fill itself back in the way sand will. The can further confirm with a simple soil testing trick using a jar. if you mix sand and silt with lots of water and then swirl it around the silt will stay suspended in the water a long time but the sand will fall out. Scale will not effect this.

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  • $\begingroup$ The sand particles are scaled up, too, so they'll be more gravel-sized, but will appear the same to the giant. Would that behave like normal sand? I'm not following the part about silt and powder, since there are no particles of that size in this scenario. $\endgroup$ – Nuclear Wang Apr 17 at 12:30
  • $\begingroup$ then your world does not obey the laws of chemistry and physics as we know them making the question unanswerable. on an earthlike planet, sand sized particles will exist and they will behave like sand. You can't "scale" physics. Your giant will see what looks like silt sized particles behaving like sand. you can't scale up silt and still get it to behave like silt. particle size actually controls its behavior because it relates to static and friction bonding forces relative to mass. the square cube law applies to everything not just living things. $\endgroup$ – John Apr 17 at 12:53
  • $\begingroup$ Unless there's someone replenishing the gravel-sized sand, it'll turn into sand-sized sand eventually. It'll also move differently in the water compared to sand-sized sand, which is I believe why some beaches are sandy and others stoney – hence when people import sand to make sandy beaches, it has to be replenished. But you'd need to be an expert to know that the beach had the wrong stuff on it, so not likely to help as a clue. $\endgroup$ – Dan W Apr 17 at 16:03
  • $\begingroup$ Expert is stretching it, you would have to be versed in soil science or geology. $\endgroup$ – John Apr 17 at 20:03
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I assume that if everything scales up x10, then so do the units of measurement. So 1 meter in the new world would be equivalent to 10 meters in this world. Clearly measuring herself would be useless.

However, your main character can measure the speed of light (or ask around to see if anyone else has measured it). If it's given as 30 million meters per second, then she knows she's a giant. Furthermore, she knows the exact scale to which she grew. (The actual speed is about 300 million m/s.)

Whether the speed of light can be measured depends on their technology, I guess. But in our world it was measured as early as 1676 by Danish astronomer Ole Rømer. Basically, he noticed that Jupiter's moon Io took longer to finish its orbit in periods when Earth was moving away from Jupiter in its own orbit around the sun, than when Earth was moving towards Jupiter. Because we also roughly knew the distance from the sun (which was known earlier), the relative angle of Earth's orbit with respect to our separation from Jupiter, and (obviously) the orbital period of Earth around the sun, we know the speed of Earth with respect to Jupiter. Given this and the delay in Io's orbit, it's quite easy to calculate the speed of light.

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At 10 meters, the ambient temperature differential between your head and your feet would be far more noticeable. Outside, you'd notice that it seems really cold when you're standing up and much warmer when you're sitting on the ground or lying down. Indoors, you might detect the opposite, as heat tends to rise and get trapped at the ceiling. Either way, you'd definitely notice a distinct difference in temperature between standing and sitting heights. You might even notice that the atmosphere is thinner up there, resulting in your breath being shorter when standing than while sitting.

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    $\begingroup$ Adiabatic cooling occurs at around 10C per 1000m, so a change of 10m will cool the air by ~0.1C. It's not noticeably colder on the roof of a 3-story building, nor do you get out of breath from the marginally thinner atmosphere. You're way overestimating the magnitude of these effects over a paltry 10m. $\endgroup$ – Nuclear Wang Apr 16 at 18:45
  • $\begingroup$ @NuclearWang Adiabatic cooling is only one effect, and near the surface won't be the most significant. Near the surface there are more significant changes in temperature. Partly this is due to radiation off the ground, and partly due to wind being stronger higher up (though if all the scenery is scaled, this might not be as significant). This question (earthscience.stackexchange.com/questions/9406/…) cites 4-5C differences between 2m and 10m. $\endgroup$ – Dan W Apr 17 at 15:53
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    $\begingroup$ @NuclearWang but you're absolutely right, it won't have a noticeable effect on breathability. $\endgroup$ – Dan W Apr 17 at 15:58
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    $\begingroup$ Though I suspect having giant lungs and having to supply air to a giant body would have an effect on breathing overall, but in that case I suppose your stance might not matter. At any rate, I can definitely say from experience that it's definitely noticeably cooler on top of a 3 story building than it is on the ground. And on the inside, it's definitely warmer near the ceiling. $\endgroup$ – Darrel Hoffman Apr 17 at 16:04
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If all the limbs are bigger, then the heart will beat more slowly : it will need more energy to push all the blood necessary and the heartbeat will slow down to 20 to 30 bpm (20 is the whale, 30 the elephant). The character could make an effort that'll left him/her exhausted, and sense his pulse at a horrendous slow rate in his head.

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Maybe a good way to tell if you're a giant is gravity. If the gravity in this world is the same from earth, she'll notice that she's heavier and that something doesn't seem quite right. Also, you can put on some normal sized animals, or giant sized animals, but not as big to scale to the Giants, so she'll see familiar animals but smaller and start questioning things.

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Simple, just jump up and down.

Creating a crater when you jump is not normal, it would certainly make the character realize that something is wrong.

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    $\begingroup$ Assuming that everything is just scaled up and the planet isn't denser to accommodate its larger inhabitants. $\endgroup$ – DonielF Apr 17 at 2:26
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Is this a trick question? Her weight will be 10X, if she had a weighing scales , she will suddenly be 10 times heavier!

So she could observe the effect of the dial going from ~50KG to ~500KG

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  • $\begingroup$ No, it's not a trick question. Yes, if a scale exists, she would remember her previous weight and would see the difference. The answer lacks elegance and reasonable dialogue with the OP to see if such apparatus exist... but it is an answer. $\endgroup$ – JBH Apr 18 at 5:25
  • $\begingroup$ You've neglected to allow for the square-cube law, she's a lot more than 10x heavier. $\endgroup$ – Separatrix Apr 18 at 9:43

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