A woman of the native religion explained that the world rests on the back of a giant turtle. A doubter asked “And what does the turtle rest on?” “On a bigger turtle”, said the woman. “And what does the bigger turtle sit on?” was the persistent question. The woman, seeing the infinite regress, replied defiantly “It’s turtles all the way down”.

That is exactly what it is NOT. Under ordinary substances are molecules, under molecules are atoms, under atoms are nuclei, under nuclei are protons and neutrons, under these are quarks, under them are strings. The underlying entities differ radically from the ones above. The laws change from ordinary mechanics to quantum mechanics to whatever obtains at Planck dimensions. Beyond common organisms is the planet Earth with its rocks, seas and air, beyond that is the solar system, beyond that the Milky Way galaxy, then the local supercluster, finally the whole universe, and maybe beyond. Again, the entities and laws change, from Newton to Einstein to Hawking.

Similarly, we encounter phase transitions when we go to high temperatures (solids to liquids to gases to nucleielectron plasma to proton-neutron plasma to quark-gluon plasma) or to extremely low temperatures (to solids with various transitions or superfluids and finally to BoseEinstein condensate). Even numbers go beyond infinity to many different kinds of infinity.

Black holes out-do neutron stars which out-do white dwarfs which follow stars on the main sequence which are bigger than brown dwarfs which are bigger than giant gas planets like Jupiter which are bigger and different than rocky planets which differ from asteroids which differ from comets which differ from meteorites.

It’s definitely NOT turtles all the way down. It’s a many-splendoured thing, like Love.