Earth-sized planet around nearby star is astronomy dream come true

[VMA131Marine]

26. We send low power laser beams out of the atmosphere all the time

If you know where to point it, you can use a laser to measure the distance to the moon by bouncing the beam off one of the mirrors left by the Apollo missions. The thrust produced by the laser would be very low, but a craft could achieve huge speeds by operating the beam continuously. Theoretically, the speed would asymptotically approach the speed of light itself, although it could never quite get there, of course.

The momentum of a photon is h/wavelength, where h is Planck's constant. If you have an ideal mirror, the momentum imparted to the spacecraft by one photon would be double the initial momentum of the photon.

According to my (non-relativistic) estimates, a 10GW red laser at 633nm could accelerate a 1000kg spacecraft so that it reached Proxima Centauri in 34 years. The spacecraft would be travelling at 25% of the speed of light at that point so it would not spend much time in that neighborhood as it would have no way to slow down.

You would not want to get in the way of the laser beam unless you were highly reflective.