This is a question I have been thinking about for the last two years. In this article, I will give a little overview of what I have discovered in that time.
The part of the brain that controls the sleeping cycle is made up of two groups of neurons. In order for you to be able to sleep at night, the activity of these neurons needs to be synchronized with the cycle of the sun (e.g. active during the day and inactive at night). When you abruptly change the cycle of the sun (by flying to New York) these two groups need to re-synchronize to the new sun-cycle.
In the interactive simulation in this article, developed by Martijn Gosgens, you can see how the two-community Kuramoto model works.
We can represent the interactions between the neurons in the body-clock as a network. In our case the network has two communities, where each community has many edges between the nodes, while there are only few edges between the nodes in different communities.
The body-clock, which is a cluster of neurons in the brain, has the same structure in all mammals, which is remarkable. It consists of two groups: two-communities of neurons that are strongly linked within each community and less strongly linked between the communities.
Synchronization is a phenomenon which has received a lot of attention in the last few decades. It is the mechanism by which a group of individuals that go through some periodic motion begin moving through the same parts of their cycles at the same time.