Time moves at the speed of light and energy and mass slow it down to form their own spacetime geometry in three dimensional space. The broken spherical symmetry of light forms the geometry of spacetime that the observer will see and feel as the arrow of time
The atoms bound together and form their own three dimensional space-times relative to their own position and momentum. Because of this time is a variable and is only relative to each spacetime therefore we have Einstein's theories on relativity.
Each observer has created their own broken symmetry this can be seen as mirror or line symmetry in the physical shape of the observer. They will feel this symmetry as the arrow of time or as the time line from the past into the future.
The observer will see time as linear because there was an evolutionary advantage in seeing time this way. The atoms of the observer have bonded together forming their own broken spherical symmetry of their own evolutionary path. As a three dimension object the observer is at the centre of their own created broken symmetry of spacetime geometry.
We have the beauty of a universal symmetry formed by the forward momentum of light that continuously forms the fabric of spacetime. Energy or mass continuously break this symmetry to form their own spacetime geometry. This universal symmetry is the foundation that human geometry and mathematics is based upon.
A link to Qantum Atom Theory on You Tube