Science Why hasn’t NASA flown a microphone to Mars? Will future probes, to places like Europa, carry audio sensors?
Science When a gravitational lens magnifies a background galaxy, why don’t we see the object doing the lensing, as we would if looking through an optical lens?
Science Can we turn Minuteman missiles into cheap launchers to deliver small payloads to the Moon and Earth-passing asteroids?
Stars If neutron stars don’t produce energy from fusion, like normal stars, how can they shine in visible light?
