Playing with quarks

Returning to Geraint F. Lewis and Luke A. Barnes, A Fortunate Universe: Life in a Finely Tuned Cosmos (Cambridge: Cambridge University Press, 2016):

“[T]he up and down quarks are 4.5 and 9.4 times heavier than the electron.  These aren’t nice, neat numbers.  And yet, they are fundamental to the Standard Model of particle physics.  Frustratingly, we can measure them, but we can’t explain them in terms of anything else.

“The other paraphernalia of the Standard Model aren’t any better.  The other four quarks are 190, 2495, 8180 and 338,960 times heavier than the electron, while the muon and tau are 206.768284 and 3477.15 times heavier.

“Is there anything special about the particular values they have?  What happens in a universe in which the electron and quark masses are slightly different?

“One might think that, since life is so hardy and robust, you’d just get a different form of life.  It might not look like us, but since life in our Universe can make use of the hodge-podge of chemical reactions on offer, any old universe would do something.  Right?

“In fact, it is rather easy to arrange for a universe to have no chemistry at all. . . . ”  (47-48)

In what they call the “Delta-Plus-Plus Universe,” for instance, Lewis and Barnes increase the mass of the down quark by a factor of about 70, resulting in a universe where something “helium-like” would be the only element.  “The online PubChem database in our Universe lists 60,770,909 chemical compounds (and counting); in the [Delta-Plus-Plus] universe it would list just one.  And being like helium, it would undergo zero chemical reactions.”  (50)

Hence, no life.

But how about a “Delta-Minus Universe”?

“Beginning with our Universe again, let’s instead increase the mass of the up quark by a factor of 130.  Again, the proton and neutron will be replaced by one kind of stable particle made of three down quarks, known as the [Delta-Minus].  Within this [Delta-Minus] universe, with no neutrons to help dilute the repulsive force of their negative charge, there again will be just one type of atom, and, in a dramatic improvement on the [Delta-Plus-Plus] universe, one chemical reaction!  Two [Delta-Minus] particles can form a molecule, assuming that we replace all electrons with their positively charged alter-ego, the positron.”  (50)

So, again, no life.  But what would happen with a “Hydrogen Universe”?

“To create a hydrogen-only universe, we increase the mass of the down quark by at least a factor of 3.  Here, no neutron is safe.  Even inside nuclei, neutrons decay.  Once again, kiss your chemistry textbook goodbye, as we’d be left with one type of atom and one chemical reaction.”  (50-51)

Which means . . .  no life.