How does the scale of the Forerunner Empire compare to that of Humanity’s in the 26th century? How does that compare to the timescales of the galaxy and universe?

What can we learn about climate change on Earth in the 26th century, specifically how much has Earth's climate warmed and how much have sea levels risen in the past 530 years?

How does explosive decompression actually work in space, and is its portrayal in the halo universe accurate to physics or just a bunch of science fantasy?

How does the gravity assist maneuver, aka an orbital slingshot, work in real life, and does halo portray it in a scientifically-accurate manner?

Based on what we know about the Nova bomb from Ghosts of Onyx and Envoy, how large must a Nova bomb be, and is it small enough to be feasibly built by 26th century humans and actually used in combat?

What would happen to a magnetic accelerator cannon (MAC) round if it missed its target, and are there hundreds of MAC rounds flying aimlessly in space, waiting to destroy a random ship it comes into contact with?

How plausible is the Single Occupant Exoatmospheric Insertion Vehicle (SOEIV / ODST drop pod) and what would it feel like to perform a combat drop in one? There is a bonus short story at the end.

What is up with the gravity on Meridian, the colony visited in Halo 5: Guardians?

How much surface area do the Forerunner mega-structures actually have, including the halos themselves, the Lesser Ark (Halo 3 Ark / Installation 00), and the Sarcophagus (formerly Onyx / location of ONIRF Trevelyan), and how do they compare to the Earth and other common celestial bodies?

Could the element that was used to kill humans on Sedra, Element 121, exist, and could the radiation pulse that it caused actually happen?

How feasible is the Planet of Blue and Red as it is described in Halo: Broken Circle?