How is it that bugs take no fall damage?


How is it that bugs take no fall damage?

In: Physics

They aren’t very dense so they don’t hit the ground very hard. In scientific terms, their low terminal velocity and lack of mass mean there is not much force on them when they hit the ground.

The bigger the thing, the more gravity affects it. So, the smaller the thing, the less gravity affects it. Human go splat, ant go plop.

Their body can take the proportional impact force of freefall on earth. This is because of the square cube law. As an organism gains surface area by 1, it’s volume increases 3. Smaller organisms terminal velocity with their mass doesn’t create a disproportionate impact.

If an object gets larger and maintains the same density, the volume of that object increases much faster than its surface area. Or, as the outside of something grows, the inside grows way more.

There’s a very useful thought tool called “squares versus cubes”. The idea is that if one property is proportional to the square of something, and another property is related to the cube of something, you can pretty much ignore everything else.

In this case, the mass an object (an insect, in this case, but the same applies to all objects) is roughly proportional to the cube of its length, because stuff on the inside has mass. And the drag that an object experiences is roughly proportional to the square of its length, since it’s only the leading surface that has to push through air.

So the bigger a thing gets, the less drag matters, and conversely, the smaller a thing gets, the more drag matters. Bugs, being very small, are greatly slowed by the air they’re falling through because the ratio of their mass (which gravity pulls against) to their area (which wind pushes against) is small.

Smaller things are stronger relative to their size.

Some effects and forces dominate at different size scales. Like how an ant can carry 10-50 times their body weight. And grasshoppers can jump so far compared to their size. And why bugs find water to be very gloopy.

Suppose that a thing has length ***L***. It then has area ***L******^(2,)*** ***and volume L******^(3)***. Now imagine increasing L and see what happens to each. Area increases more than length, and volume increases even faster. Some effects may depend upon area, some on volume, and so the relative strength of these changes at different size scales.

The mass and weight will scale with it’s volume. But the strength the material it’s made of will scale with area (think of the thickness of an iron rod). So bugs are very tough and strong for their weight.

Also, the air resistance they feel scales with area, so they will fall slower and fly easier.

If you get scaled down so you’re half the height, you’re 1/4 as strong, and have 1/4 the surface area, but you’re only 1/8 as heavy. This continues the smaller you go. For a very small bug, you might have a surface area to weight ratio similar to a sheet of paper.

Speed required to damage them is greater than maximum falling speed possible due to air friction

When you fall you push air around you. Feel it with your hand. The air is also pushing on you. When a bug falls, the air pushes against it too hard for it to go fast because it it so small and light. Drop a leaf and a rock, observe.

Edit: Gravity pulls on the leaf and rock equally.

The terminal velocity of an object, aka the fastest a thing can fall before air resistance stops it from speeding up any more, gets bigger with weight, and smaller with cross-sectional area (you can think of cross-sectional area as just, how much of the object you can see from one direction).

This means heavy things fall faster, and wide things (like paper when its wide side is facing down, or a frisbee) fall slower.

Now, weight increases according to how big a thing is, and so does area **but** they increase a different speeds.

Imagine you have a single cube. Now imagine growing that cube so each edge is twice as long as the original.

To fill this new, bigger cube, it takes *8 of the original cube* (2 cubes along each edge). This makes the cube *8 times as heavy*.

On the other hand, each side of the cube only takes 4 of the original cube’s sides to make. This means the cube’s *cross-sectional area 4 times as big* as the original.

From those examples, you see that increasing something’s size increases its weight faster than its cross-sectional area.

This holds in reverse too. Shrinking something shrinks its weight faster than its area.

Now, remember that bigger area means slower fall, and bigger weight means faster fall.

If you take a human, who falls fast enough to hurt a lot, and shrink them down to the size of a bug, their weight will shrink a lot more than their area, so in turn, they’re going to fall a lot slower than a normal human.

This is most of the reason that bugs “don’t take fall damage”, as you said.

Fall damage is the body being unable to keep up with the massive forces required to bring an object to a stop in a short period of time. For a human, trying to stop 100lbs within 5 feet (a **20:1** ratio for my example human) gets tough pretty quickly depending on how fast they are going. According to a brief google search, the average house fly weighs something like .00001lbs and is .023ft tall (a **1:2300** ratio). So the ratio is like 23,000 times better for them to start with. IE: bugs have less weight to decelerate in a relatively longer period of time (if we assume the two creatures are falling at the same speed)

However, another result of this smaller weight, is that air resistance becomes a much bigger factor when falling. A tiny little updraft can make the insect lose almost all of its downward momentum, and their terminal velocity is much slower as a result. So even though my previous paragraph assumed that the human and bug were falling at the same speed, that’s almost impossible. A bug will fall WAY slower.

Not only that, but there’s something called the Squared-Cubed law which says things like “if something doubles in height, it usually multiplies its weight by around 8” and that has further implications for our comparison. One effect of this is that while large creatures may have stronger bones compared to small ones (you don’t see us getting flattened by a fly swatter, for example), but a lot of that strength is spent simply keeping us upright in the first place to counteract the massive increase of weight our size comes with (see that ratio I posted earlier), so when something like a human is met with an impact, that force is being added on top of the strain our bodies are already under as we maintain our own shape. A bug barely has to spend any energy maintaining its own structure, so nearly all of its strength can be devoted to absorbing the impact properly.


So yeah, with all of that combined, comparing the amount of damage a human takes from a fall vs an insect, any damage the bug takes would be basically nonexistant compared to what us humans are used to.

Basically same way we don’t damage using parachutes. Some bugs have simply air friction and weight ratio that it’s like having a natural parachute at all times.

To a such bug, air is more like a liquid, so it falls through it like you would sink into a deep lake. Even if lake is super deep – like 15 stories deep, you still won’t crash the bottom of the lake in the end, water slows you down so much all the way.

Even though acceleration by gravity is same, water limits the speed you end up with (called terminal velocity) much more than air would. But if gravity was – 10 times stronger – say – on different a planet or whatever, you could totally splat to the bottom of such lake and water friction couldn’t overcome it enough to save you.

To break anything you need to spend a certain amount of energy, depending on the material it is made. It’s easier to break the shell of chocolate egg by hitting it , than it is to break a baguette, than it is to break a cube of steel.

Every material needs a certain amount of energy to break its structure.

Energy is greater when the speed of the moving object is greater and when the weight of the moving object is greater.

A bug is very light. Its weight is very small. Thus when falling from a table, the energy it gets from the speed is smaller than for example an egg gets.

Also, a bug’s shell is made by cythin which is extremely durable. You know that when you try to squash a bug, you need to make some effort. That energy you spend to squash a bug is higher than the energy the bug has during the fall.

So you get a creature that is small, light, which is also extremely well armored. The fall energy it gets is not enough to break its shell. It’s smaller than what your finger can produce to squash it.

Additionally, beetles have a protective shell encasing their squishy bits. Because they’re so small, they need armour to protect themselves from damage that would otherwise kill them. Humans are complex enough that we can heal bruises instead of dying from them, so we don’t need armoured skin.

Bugs are Small so no fall fast. No fall fast means doesn’t splat hard. Bugs don’t splat hard.

Late to this party but here is a video by Kurzgesagt explaining this very thing perfectly!

I’ve heard that cats are the same (not willing to test), their fur slows them down enough to prevent fall damage.

Tarantulas are very susceptible to injuries by falling as far as I know. So pet tarantula enclosures should not be built with steep falls. Yes. Even the smaller falls that could happen inside the enclosure. They could result in abdominal bleeding or broken legs.

It’s like the saying goes. The fall doesn’t kill you, it’s the sudden stop.

Newton: an object at rest tends will stay at rest unless acted on by an outside force. And object in motion will stay in motion unless acted on by an outside force. This is momentum.

The faster you fall the more momentum your body gains. When the force of that momentum exceeds the strength of you bones/structural integrity of your body, when you stop your body’s own momentum will crush it against the ground. Because the momentum is greater than the strength of the body, the body breaks.

Bugs have very little mass and relatively large surface area to that mass so they have a very low terminal velocity (maximum speed they can fall/point at which the force of air resistance which increases as speed through the air does, matches the force of gravity so you stop accelerating). Their mass and terminal velocity is so low that they don’t have enough momentum at their maximum falling speed to exceed the strength of and break their body.

So no matter how far they fall they never get hurt on landing.

Lease cutter ants use this to their advantage by purposely jumping out of trees when they want to get down because they can’t be damaged from the fall.


This is a good explanation and a pretty cool video to watch on the topic.

How can I flick a bug and it be totally fine? That’s like getting smacked by a tree and shrugging it off