<span>Czech Republic (west)
Austria (south-west)
Hungary (south)
Ukraine (east)
<span>Poland (north)</span></span>
Because of the sound waves that can travel through walls. Our ears are very intelligent and can process many sounds. Light rays are different though, because objects can block them because the light rays are not as strong as the sound waves.
When people perform experiments of any sort, the professional people only change one variable so that they know what is being changed. For instance if I compared the effect of the growth of flies, and one group had more food and cleaner water, and the other group had neither, it would be pointless. It would be pointless because even if the experimental results were a success, you wouldn't know for sure which variable caused the change, the water or the food variable. That's why there can only be one man-made variable at a time.
Hope this helps!
Basically it would mean that there isn't enough space for people to move into which means the economy takes a poop and overpopulation happens and spacial inequality becomes a thing.