Appearance and Reality: The ancient Parmenidean distinction still holds!
To think deeply in a scientific sense often means to think counter intuitively.
For example, the things all around me, including me, appear to be solid matter, but in reality, they are just energy fields and empty space.
The earth appears to be standing still, but in reality, it is rotating on its axis and revolving around the sun.
When you think counter intuitively, you are thinking DEEPLY.
Appearance Vs. Reality
Philosophical example: Kant’s Copernican revolution: Defining reality from the inside out.
Things like space, time, and causality that appear to be outside of us - as objectively reified features belonging to the world – are in reality, the products of our mind.