Amy and Alex are astronauts traveling at relativistic velocities with respect to each other. At some time they are at the same place, and they make some measurements that they compare with each other. Disregarding the time of travel of light and measurement, by name or number identify all of the four following measurements that both would agree on. 1) The length of Alex's spaceship 2) The magnitude of the electric field on Alex's nose 3) The magnitude of a point charge 4) The rest mass energy of Amy's spaceship