Is it possible that the accelerating expansion of the universe is an illusion caused by time dilation? Space is already expanding, so from the perspective of a gravity well, it should appear to expand faster in deep space, unless I'm mistaken.

The accelerating expansion of the universe is not an illusion caused by time dilation. It is a well-established cosmological phenomenon that has been observed through various astronomical observations, such as the redshift of distant galaxies, the cosmic microwave background radiation, and the distribution of large-scale structures in the universe. This phenomenon is described by the Lambda-CDM (Lambda Cold Dark Matter) model, which incorporates dark energy as the driving force behind the accelerated expansion.

Time dilation, on the other hand, is a well-understood consequence of Einstein's theory of relativity, and it does play a role in our understanding of the universe, especially in the context of gravitational fields. In regions of strong gravitational fields, such as near massive objects like black holes or in the vicinity of dense clusters of galaxies, time dilation can cause time to appear to pass more slowly compared to regions of weaker gravity.

However, time dilation due to gravity is not responsible for the accelerating expansion of the universe. The expansion of the universe is a global phenomenon that is observed on cosmic scales and is not related to local gravitational effects. In fact, dark energy is believed to be the dominant factor driving the accelerated expansion, and it has a repulsive effect on the large-scale structure of the universe, counteracting the attractive force of gravity.

So, while time dilation due to gravity is an interesting aspect of relativistic physics and can affect local observations, it is not the cause of the accelerating expansion of the universe, which is a separate and well-established cosmological phenomenon explained by the presence of dark energy.