Time dilation is primarily based on velocity, not acceleration. It is a phenomenon predicted by Albert Einstein's theory of relativity, specifically the theory of special relativity. According to this theory, time appears to pass slower for objects that are moving relative to an observer at rest.
The faster an object moves relative to an observer, the more pronounced the time dilation effect becomes. As the velocity approaches the speed of light, time dilation becomes significant. This means that time appears to slow down for objects traveling at high velocities compared to an observer at rest.
Acceleration, on the other hand, can have secondary effects on time dilation. When an object undergoes acceleration, it can experience changes in its velocity, and these changes can affect the overall time dilation experienced by the object. However, the primary factor for time dilation is the velocity of the object, not its acceleration.
It's worth noting that there is another form of time dilation called gravitational time dilation, which is based on the gravitational field strength rather than velocity. In this case, time appears to pass slower in regions of stronger gravitational fields, such as near massive objects like black holes. However, this form of time dilation is not directly related to acceleration.