Krypton's core is made of uranium? (mathy types wanted)

[Captain Kal]

The Earth has 10.75 g/cm^3 core density compared with the average density of 5.52 g/cm^3 for the overall Earth.

Iron has a density of 7.87 g/cm^3 compared with Uranium's 19.1 g/cm^3.

While that would tend to give us a Krypton core density 2.43 times the density of our own planetary core, the proportion of lighter elements in the outer planetary layers may compensate for that.  Natural giant planets tend to have higher gas content in the outer layers, like Jupiter and Saturn do, so the compensating density layers isn't a stretch.  It's also possible the other elements in the core may compensate for density making it somewhat less dense.  No planetary layer is a pure element of any kind or even close to it, though some elements tend to dominate.

While it may be possible to make a 35 G planet with a smaller mass, I don't think it can be much less massive than a brown dwarf mass (0.8 solar masses) or else Gresh's & Weinberg's objection about impossible densities rears its ugly head again.

It must be noted that not only does the Sun-Thrivers origin of Krypton -- reaffirmed for Post Crisis per Wolfman's History of the DC Universe books -- give an atypical planetary formation, but the details of Krypton's composition and structure suggest, if not a unique planet, certainly an exceedingly rare one. Perhaps only Daxam came close.

[Captain Kal]

FYI, I just figured out that for a proportionate Krypton core largely made of uranium, only less than 1/480th of the uranium needs to fission to blow-up Krypton.  Of course, that would have to happen all at once instead of being spread out over years else the energy would harmlessly dissipate instead of exploding.

[Captain Kal]

According to Maggin's "The Greatest Green Lantern of All!", Krypton had an erratic magnetic field.  Said field was capable of disrupting other stars
systems to the point of dooming them.

http://superman.nu/tales2/greatestGL/?page=3

That erratic field is consistent with an unstable planetary core.  The sheer power of a field that could do that to other stars in a space sector suggests it's powered by more than just ordinary radioactivity.  Instead, perhaps that erratic magnetic field was an early indicator of Krypton's coming nuclear explosion.  Certainly, the Guardians were aware of this.

[JulianPerez]

The question I originally asked was, if planetary density is greater as a result of heavier elements in the uranium core, how would that affect calculations about Krypton's size and circumference, if we need to have it be brown dwarf mass to produce a superbeing? In other words, how BIG was Krypton?

Here's one interesting point about how Krypton may have been liveable despite a Uranium core - wasn't gold the most common element on Krypton, found extensively in the planet's crust and mantle? Gold has a property of absorbing radiation, like lead - in fact, use of gold sheets around uranium was how the current atomic model was formed and the nucleus was discovered. It may have been the case that the gold absorbed much of the radiation and made life on the surface possible for hardy beings.

Many life forms have different tolerance to radiation; bacteria can absorb nearly a thousand times as much as mammals can, and reptiles have shown resistance as well. It's not inconceiveable Kryptonian life, with a shield of gold, has such an immunity.

There are many, MANY problems with Maggin's "A Name is Born" story.

For instance, how could a whole race spring from just two people?

If Kryptonians sprang from space explorers, why did they spend so much of their history in a primitive state?

If all Kryptonians sprang from two space explorers, why is there so much variation in Kryptonian appearance if they didn't evolve on the planet? For instance, the blackskinned inhabitants of Varaho.

Here's the big objection: if Kryptonians came from elsewhere, and are not a product of evolution on Krypton...why would ANY of them exhibit unusual powers and abilities of the kind Superman does as a result of the red sun, just like Kryptonian animal and plant life has been shown to do so? Why would any of them be vulnerable to Kryptonite?

It also conflicts with the fact that except for a few comments told well, well after the story, there's no sign of Kryptonians even BEING from space, nothing to show this in their civilization or culture or tradition. It conflicts with established stories, unusual for Maggin, who usually understands previous rules.

[Captain Kal]

Quick and dirty answer: I stick by the 0.26 Sun radius size I've posted elsewhere.  Krypton cannot be much smaller or less massive or else we couldn't build it with normal matter or have a 35 G gravity.  We can compensate for the uranium in the core several ways which I've posted earlier.

I'll post on your other comments later.

[Captain Kal]

Great theory on how gold, and possibly other heavy elements, helped shield life from the radiation brewing in the core.  I like it.  Remind me to quote you on it in the future, Julian.

Re: a whole race springing from two people: That could be the result of genetic engineering  from their parent world for just such a possibility.  It may more logically be the result of the outworlder colonists' initial lack of adaptation to the relatively higher radiation and other mutagenic factors in the environment that caused a higher mutation rate in the early generations.  That would allow for the genetic diversity needed here.  While the heavy elements would shield life from the nuclear reactor in the core, the overall radiation levels would tend to be higher on a high-G world from the higher proportion of radioactives on the surface itself.  Conceivably, a space-faring race would have engineered their astronauts to have higher radiation tolerance though the mutation rate would still be higher for their offspring.  The inhabitants of Vathlo island may be an extreme case of genetic variance due to the higher background radiation.

Of course, it's entirely possible that others were marooned on Krypton so they weren't the only two, though that's not documented.

Despite our 'high' tech compared with our ancestors, one good nuke war and we'd be back to the Stone Age.  IIRC, someone once said WW 3 would be fought with nukes and WW 4 would be fought with sticks.  The same could apply to the colonists.  They didn't have the infrastructure to create nor maintain what they had.  They had no way to rebuild sophisticated microciruits when they inevitably failed.  They had no means of reproducing high-grade alloys.  The list goes on.  Without the infrastructure of their homeworld's eventually everything they brought with them would fall into disrepair.  Only after civilization had been regenerated to the point of their homeworld's could this occur.

Kryptonian humanoid powers are mostly based on gravitational adaptation according to LSOK, with the sun amplifying those base abilities to an incredible degree.  LSOK also does mention Krypton being colonized from outside twice: Once on the opening page of the story, and twice when Jor-El tells Einstein about the legends surrounding Krypton's origin.

Kryptonite happens to be the antidote to the Daxamite lead vulnerability.  Daxam is the parent world of Krypton according to TOLSH #325. It may be the generations of undirected Kryptonian evolutionary descendants both acquired the normal reaction to lead and an unexpected counter vulnerability to the once beneficial kryptonite.  Hey, we can't breathe water anymore like our fishy ancestors.  Also, Daxam has always been a pioneer in bioengineering.  The powers from gravity and sun differences may have been engineered so though they might not have anticipated the drastic effects of a yellow sun environment.  Others have suggested that it seems quite artificial for a potentially powerful race like the Daxamites to both be vulnerable to common lead yet be on a world curiously lacking in that very element.  The same goes for the powers of Kryptonians.  They suggest an Oan offshoot like the Guardians were behind both races, much like the Oans once created the Psion race.  We do know 10,000 odd offshoots of Oans departed Maltus and we only know the fates of about half a dozen of them (Guardians, Controllers, Zamarons, Leprechauns, Krona, mortal Maltusians).

[llozymandias]

Of course krypton was not made of ordinary matter.  Everything from krypton becomes super when under a yellow sun.  That includes totally inanimate objects.

[Captain Kal]

Absolutely true, Ilozymandias.

But under red solar influence, it does behave like our matter.

It only acquires super characteristics outside Rao's influence.