(Photos and image at link.)A powerful transmitter in remote Alaska sent long wavelength radio signals into space Tuesday with the purpose of bouncing them off an asteroid to learn about its interior.The asteroid, 2010 XC15, is estimated to be about 500 feet across and is passing by Earth at two lunar distances, which is twice the distance between the Earth and the moon. Results of Tuesday’s experiment at the High-frequency Active Auroral Research Program research facility at Gakona could aid efforts to defend Earth from larger asteroids that could cause significant damage.“We will be analyzing the data over the next...