system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why is it impossible for animals to grow to certain sizes without collapsing under their own weight? If you just scale everything up 1:1, why can’t they just function normally at increased sizes?
gpt
Imagine a cube with each edge of length 1.    
The sides have an area of 1 x 1 = 1.      
The volume is 1 x 1 x 1 = 1.  

Now scale it up "1:1" so all the edges are now length 2.  
The sides have an area of 2 x 2 = 4.    
The volume is 2 x 2 x 2 = 8.  

So despite you scaling all the lengths equally "1:1" by 2.  
Area went up 4 times, and volume went up 8 times.   

Things like strength of bones are how wide they are, so they vary by area.  
Stuff like weight depends on how much stuff there is, so they go up by volume.   

And as you can see, area goes up a lot slower than volume does.  

This is called the square-cube law, because the sides are squares which go up a lot slower than the volume. 

Bone strength is just one factor.  
Stuff like heat loss is skin area (goes up with the total area of the sides), heat generation is how much organism there is ( goes up with volume)  
And many other factors like oxygen flow, etc.