This paper discusses the construction of classical time-dependent solutions in open string field theory describing the motion of the tachyon on unstable D-branes. Despite the string field theory action containing an infinite number of time derivatives, making the initial value problem unclear, the theory contains a family of time-dependent solutions characterized by the initial position and velocity of the tachyon field. The world-sheet action of the boundary conformal field theories associated with these solutions is studied, and the corresponding boundary states are analyzed. For D-branes in bosonic string theory, the energy-momentum tensor evolves asymptotically towards a finite limit if the tachyon is pushed in the direction of the potential's local minimum, but hits a singularity if pushed in the direction of unbounded potential. The paper also explores the effective field theory analysis of the decay process, showing that the energy is stored in the plane of the original brane rather than being carried away by radiation. The boundary state analysis confirms that pushing the system towards the minimum of the tachyon potential leads to a smooth evolution of the energy-momentum tensor, while pushing it in the other direction results in a singularity. The paper concludes that the tachyon condensation process on unstable D-branes is a complex phenomenon with implications for string theory and cosmology.This paper discusses the construction of classical time-dependent solutions in open string field theory describing the motion of the tachyon on unstable D-branes. Despite the string field theory action containing an infinite number of time derivatives, making the initial value problem unclear, the theory contains a family of time-dependent solutions characterized by the initial position and velocity of the tachyon field. The world-sheet action of the boundary conformal field theories associated with these solutions is studied, and the corresponding boundary states are analyzed. For D-branes in bosonic string theory, the energy-momentum tensor evolves asymptotically towards a finite limit if the tachyon is pushed in the direction of the potential's local minimum, but hits a singularity if pushed in the direction of unbounded potential. The paper also explores the effective field theory analysis of the decay process, showing that the energy is stored in the plane of the original brane rather than being carried away by radiation. The boundary state analysis confirms that pushing the system towards the minimum of the tachyon potential leads to a smooth evolution of the energy-momentum tensor, while pushing it in the other direction results in a singularity. The paper concludes that the tachyon condensation process on unstable D-branes is a complex phenomenon with implications for string theory and cosmology.