The formula for collisional excitation of the atoms responsible for auroral emission can explain why green auroras from excited oxygen atoms can occur at relatively low altitudes, but red auroras from these same atoms are constrained to higher altitudes of lower density. The same formula also suggests much lower electron velocities (~100 km/s) than are required to excite the oxygen atoms to the required metastable levels for subsequent emission (~1000 km/s).

Fast Radio Bursts are flashes of radio emission lasting for several milliseconds. The time of arrival of signals depends on the radio frequency, called the dispersion measure (DM), which depends on the environment through which the signals travel, specifically the number of free electrons in their path. Very few FRBs have matches with sources observed at other wavelengths (Wikipedia - Fast Radio Burst).

...What we have come to appreciate is the seminal role played by clustered star formation in driving the physical and chemical evolution of the galaxies that host these stellar nurseries. Such concentrated sites of newborn stars along with their nebular environs constitute what are known as galactic ecosystems. These energized realms represent vital “crucibles” for growing the chemical complexity that is necessary for biotic processes.

Carl Sagan wrote that "If you wish to make an apple pie from scratch, you must first invent the universe.” We wish to know our home, so back we go, to the Big Bang, and step by step to today.

This edition combines fun and science as only Dr. Waller can do, as we take a colorful look at what's going on in supposedly empty space between the stars in the Milky Way galaxy.