QUESTION

If Superman has X-ray vision, why can’t he see through lead?

ANSWER

Ever wonder why Lois Lane wore those lead lined dresses? Perhaps to keep Clark Kent wondering and speculating?  Oh yes, Superman was ” more powerful than a locomotive”,  and “able to  leap tall buildings in a single bound”, and “faster than a speeding bullet”.  And he could see through solid objects, but not lead.

There is good physics behind Jerry Siegel and Joe Shuster’s 1930’s cartoon character. X-rays are a form of electromagnetic radiation, same as light, microwaves, cell phones, radio, and television waves.  All these energy waves are bouncing up and down and sideways as they all move at the speed of light.

The higher the frequency (more vibrations per second), the higher the radiation energy. The higher the energy, the deeper any rays will penetrate matter. That’s what we want to happen when we get an X-ray at the dentist or doctor’s office. The X-rays go right through flesh, but some are absorbed by the denser bones, and toss a nice diagnostic shadow on a piece of photographic film.

That’s the good news. The bad news is that X-rays, and gamma rays also, are ionizing radiation. They knock electrons off atoms, leaving behind an ion. An ion is an atom that is missing some electrons.

These atoms are not playing with a full deck, so to speak. They can change body chemistry in harmful ways. One such bad outcome is cancer. What can stop X-rays?

Anything that has a lot of atoms with lots of electrons going around the nucleus. Because each time an X-ray knocks an electron out of orbit, it loses energy.

Get a material that has the most electrons per atom and the most atoms per cubic inch, i.e. densely packed. Uranium is an excellent choice.  Uranium has 92 electrons per atom and is 19 times as dense as water. Gold is beautiful, with 79 electrons per atom and 21 times denser than water. Platinum is nice with 78 electrons per atom and 21 times denser than water.

But uranium, gold, and platinum are too expensive. We settle for lead, which has 82 electrons per atom and is 11 times denser than water. Lead is cheap, about one dollar a pound.

The X-ray technician drapes a lead lined vest over the patient at the dental office. Then she stands behind a lead lined wall and looks through a lead laced window before zapping the mouth with X-rays.

Lead is used to stop any kind of ionizing radiation.  Russian KGB officer Alexander Litvinenko fled to London and wrote two books critical of his former spy superiors, including Vladimir Putin. In November 2006, some really bad people put highly toxic and radioactive Polonium-210 in his tea at London’s Mellinnium Hotel. He fell seriously ill and died 3 weeks later from radiation poisoning. He was buried in a lead-lined coffin in Highgate Cemetery.

Those assassins chose wisely. Polonium-210 is an alpha particle emitter. It doesn’t give off much gamma rays. Geiger counters work by detecting beta particles and gamma rays. Because alpha particles can be stopped by a piece of paper, skin, or a few centimeters of air, the Polonium-210 can be carried around in a suitcase or pocket and not be detected nor be harmful to the carrier. But once inside the human body, the massive alpha particle causes enormous damage to cells, tissue, and organs.

Google in “Litvinenko” and read more about this plot, the investigation, arrests, evasions, denials, and the whole sordid affair.