Yet 2 meters of water will stop neutrons. Water is pretty cool.
this post was submitted on 25 Aug 2026
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Sure, but just because it's chock full of Hydrogen, which happens to be about the same mass as a neutron and thus takes up a lot of its energy per collision. Plastic, being a hydrocarbon, does the same thing.
That being said, water is pretty cool. You could use 2 inches of lead to stop 90% of gamma radiation, or 2 feet of water for the same effect. On top of that, metal is terrible at slowing neutrons (due to metal not being hydrogen), but that same 2 feet of water will slow down the neutrons by about 99.5%.
It is because of the hydrogen, but it's not really to do with the mass, but rather because a "collision"/interaction is much more likely. For instance, ^58^Ni has the same likelihood to interact as hydrogen, while deuterium has only a fifth. ^135^Xe meanwhile has some millions of times the absorption power of hydrogen and it's quite a lot heavier. It's just not very practical as an absorber.
Hydrogen's cool man. It's just like, one little proton out there in the universe, with his Jiminy Cricket Electron buddy circling around all times, making sure he stays balanced. An unfathomable number of them, more than anything else. All exactly the same yet repelled by each other, like speed dating at comic-con.
This is why you need to drink a lot of water
or 4 morbid humans on each direction
Tell me more about how you're unstable, full of bugs and need to finish your development
And unfit for the pubic to interact with.
And they're so insanely positive all the time that they can rip the negativity out of you twice in such a way that it scrambles your DNA.
Never underestimate the toxic positivity of an alpha particle...
And, from the "size really doesn't matter that much" faction, the neutrino just arrived...
They come and just keep going.
The Neutrinos? From Dimension X? They're so cool they're frozen!
Tbf you actually want 0 penetration. Its already a hole, you just want to insert yourself into said preexisting hole.
Making a new one is probably a bad idea
Yeah I'm a Neutron Male
Gives new meaning to Jimmy Neutron
"Oh, that's-"
The speaker was crushed as OPs sudden extreme gravity ripped the earth asunder
I see you've met my cat
Gotta blast!
I am a gamma male.
Sweet, Dr. Banner is on the Fediverse!
What prevents Superman from being able to see through lead but not concrete?
Narrativium
Comic book authors
If you're talking about the neutron it's because concrete has a lot of hydrogen. Alpha particles, beta particles, and light (gamma rays in this picture) interact with electrons, with the probability of being stopped increasing with electron density. Lead has a lot of electrons (its lower on the periodic table, called a "high z" element).
Neutrons, however, don't care about electrons and instead interact with the nucleus, with the probability of being stopped depending on the spin state of the nucleus and the neutron. This doesn't follow a specific pattern on the periodic table, but hydrogen has a big chance of interacting with the neutron while lead doesn't. Cadmium, boron, and I think lithium 7 also would stop neutrons easily (there are more of course but those are what I remember offhand).
Nah, that's not what they're talking about. Superman's vision is capable of penetrating concrete, but gets reliably stopped by lead. None of the particles here (or, I'm guessing, anywhere) have that property.
Gamma rays kinda do, you need 10x more concrete to block them than lead: https://en.wikipedia.org/wiki/Half-value_layer
Phew, good to know. I was beginning to think Superman isn't real.
Gammas might be able to penetrate a little bit of concrete, since concrete has lower electron density than lead
what do neutrons care about though? how do we appeal to that demographic?
Yeah! Well if i get inside your body 🥵 (IF) I can rip your DNA to shreds unlike any of those other beta or gamma particles 😤
Well, duh. Did you not notice the blonde constantly chasing him?
Aren't Gamma-Rays impossible to stop even with lead? You can only weaken them.
Gamma rays are stopped by things with a lot of electrons, so a sufficiently thick block of lead will stop it
EDIT: higher energy light has more penetration power (so gammas are quire penetrating), but it's a finite value
The madder they get, the stronger they get.
How much concrete do you actually need to stop a neutron with probability 1/2? Is 1 lightsecond enough?
Neutron Male don't interact with nuthin'.