Why, exactly, does kryptonite hurt Superman?
To my understanding, kryptonite is a rock that is from the planet Krypton. Superman is also from planet Krypton. Yet somehow kryptonite weakens Superman and can even kill him.
How does this work? Why exactly does kryptonite hurt him? Isn't his entire home planet made of kryptonite?
Kryptonite is a transuranic element or compound (we are never told which for certain) whose inherent radioactivity inhibits the absorption of high-energy solar radiation which Kryptonians use to power their feats of superhuman ability.
Not only does it prevent the further absorption of solar energy, it displaces, painfully, said solar energy with kryptonite radiation causing the immediate loss of a Kryptonian's superhuman abilities within seconds and can, depending on the purity and exposure length, lead to the death of a Kryptonian by a form of "radiation poisoning".
A nice analogy (promoted by AncientSwordRage) in a fashion similar to "carbon monoxide poisoning" where carbon monoxide molecules are being taken up by blood's hemoglobin instead of the normal Oxygen molecules. The CO is displacing the O2 molecules but not providing any oxygen necessary for life. With sufficient displacement of O2 molecules a person can die.
DC has made no official "scientific" rationalization as to HOW Kryptonite works. Over the decades, we are given a variety of reasons it works, but just vague enough we cannot be exact on the process within his cellular activity.
- Though Kryptonite first appeared on a radio broadcast in 1943 and made its first non-green appearance in 1949’s Superman #61, we would not actually see the signature GREEN Kryptonite until 1951 in Action Comics #161.
Kryptonite's origins vary but most describe their creation at the core of the planet Krypton and were in some continuities responsible for the explosion and destruction of that world. Many pieces arrive on Earth because they traveled near the space-ship Jor-El sent baby Kal-El to Earth in. Other pieces were thought to arrive later.
Most depictions indicate it was only the core of the planet which was comprised of Kryptonite, though some of the earlier ones indicated any piece of Krypton that came to Earth was considered Kryptonite.
Kryptonite's origins vary depending on the continuity from which it appears in. In the Silver Age, kryptonite came in a variety of colors and each color had specific affects which were caused by exposures to different radiations, natural phenomena or scientific experimentation.
In almost all known continuities it is Green Kryptonite which has proven to be lethal to Kryptonians who have been exposed to its radiation. Green Kryptonite was lethal to any Kryptonian from the same universe the Kryptonite was derived from.
- This fact was discovered by Post-Crisis Superman when he was forced to execute the Phantom Zone villains of another Universe after they had killed everyone on Earth. Post-Crisis Superman was immune to green Kryptonite from their universe and was unaffected by its radiations. (See SE Article: In comics how many people have been killed by Superman?)
Several of Superman's foes use Kryptonite as part of their arsenal of weapons including Lex Luthor, who wore a ring with a piece of Kryptonite embedded in the ring. Luthor wore this ring until it gave him cancer.
Said ring was recovered by Superman and given to Batman, as a part of a contingency plan to "stop" Superman should he ever be mind-controlled or have his free will compromised.
Metallo has a robotic body whose powerplant uses a hunk of Kryptonite as its power sources. Brainiac was also fond of using Kryptonite in many of his schemes including creating a body covered with the material.
More modern depictions of Kryptonite only show small amounts of Green Kryptonite on Earth, but some advanced science has been able to duplicate the signature radiation making it capable of being used as a weapon against Superman.
As an aside, the Green Lantern's ring is also able to replicate the signature of a piece of Green Kryptonite potentially making them capable of defeating Superman, if necessary.
Im wondering if the radiation is more a vacuum to supermans stored solar energy, then it is a blocker. Since he feels "drained" every time he's around it.
Exactly. The Kryptonite "pushes" out Superman's stored energy and replaces it with poisonous radiation he cannot process!
When you mentioned it 'inhibits absorption' it made me think of how ethanol (makes you drunk) inhibits the uptake of methanol (makes you blind). Or carbon monoxide being absorbed instead our oxygen by haemoglobin. Perhaps a similar analogy would help your already very good answer?
I asked this question hoping to get an answer from specifically you, @Thaddeus. You rocked it again.