Champion Principal retweeted

Look at this astronaut's face during reentry, knowing the capsule exterior is at 5,000°F.
The physics of why he's alive are wild.
The air in front of the capsule compresses so violently at Mach 25 that it turns into plasma. 5,000°F on the surface. Half the temperature of the sun. The heat shield absorbs that energy by literally burning itself away, layer by layer, carrying the heat with it as gas.
One inch of material is the entire margin. On the outside of that inch: 5,000°F. On the inside: 75°F. Room temperature. The thermal gradient across that single inch is the steepest temperature drop humans have ever engineered.
The orange glow in the window is ionized nitrogen and oxygen. That plasma is why comms go black for six minutes during reentry. Ground control can't reach the crew. The astronauts are alone inside a fireball, falling at 25,000 mph, watching the laws of thermodynamics keep them alive through a 1-inch wall.
Artemis II did exactly this last night. Four astronauts hit Earth's atmosphere at 24,664 mph, rode a 4,900°F plasma sheath for six minutes of radio silence, and splashed down a mile from target.
The heat shield is now being inspected for cracks. They found over 100 on the last unmanned test.
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