Our Almost Empty Universe, Robert Piccioni

A must read, I think…

What follows is the most recent “newsletter” from Robert Piccioni. I have no idea, or rather little understanding of what he is talking about, but there are two observations in what he writes below that I get, or at least I think I do.

These being one and two—

1. Our observable universe is almost completely empty and 2. Everything we see is comprised of the 1-in-a-billion surviving particles of matter.

Now most people probably prefer that our universe not be empty at all but be filled to overflowing with the love of an all seeing and all knowing God, the Father or Mother figure. I guess I prefer that myself, but my preference and probably that of some 7 billion others is based on no observable evidence. And hence why we speak of the ultimate incompatibility of science and religion.

Anyway here’s what he writes in his recent newsletter of October, 2019. This sort of thing has always been for me must reading, for I still want to understand what so far I’ve been unable to understand.


Amazingly, even with 100 billion galaxies, each averaging 300 billion stars, our observable universe is almost completely empty.
These two facts should clarify the emptiness of space.

1) Imagine a giant balloon surrounding our Sun that expands until it reaches the nearest neighboring stars. That balloon would be big enough to contain every star in our observable universe, and then some. But, it actually contains only 1 star. Most of the universe is the space between galaxies, which is even emptier.
2) Everything we see — stars, oceans, mountains, even lead bricks — is almost entirely empty space. All we see is made of atoms comprised of protons, neutrons, and electrons.

Physicists believe electrons have zero size. Protons and neutrons are also probably almost entirely empty space, but just for fun, let’s say they are solid balls with radii of about 1 trillionth of a millimeter.

We know the radius of our observable universe is about 45 billion light-years, and that it contains 10^80 (1 followed by 80 zeros) protons and neutrons. So, even if protons and neutrons were solid, our universe would be: 99.999,999,999,999,999,999,999,999,999,999,999,999,999,999,93% empty.  To save you from counting, this number has 45 nines.

Anything other than empty space is very special indeed.

One might ask: Why is there so little stuff? But, the really interesting question is: Why is there anything at all?

When our universe began in a Big Bang, energy was converted into exactly equal amounts of matter and antimatter. If this equality had continued, every particle of antimatter would have annihilated with a corresponding particle of matter, taking both into oblivion, and leaving only light. Our universe would have been entirelyempty.

Our existence depends on a tiny, inexplicable asymmetry in one of the four forces of nature: CP-violation in the weak force.

Symmetries are powerful simplifying principles that physicists love. Here, C denotes the symmetry operation of replacing particles with their corresponding antiparticles and vice-versa, and P denotes taking the mirror image.

The strong nuclear force, the electromagnetic force, and gravity all seem perfectly symmetric under C alone, P alone, and the combined symmetry CP. These three forces treat matter and antimatter exactly the same, thus preserving their relative numbers. But, the weak force, an iconoclast in many regards, is just a little bit different.

The weak force is completely antisymmetric under C, and under P.
For example, nature produces left-handed neutrinos but never right-handed neutrinos — a 100% P-violation. Nature also produces left-handed neutrinos but never left-handed antineutrinos — a 100% C-violation. But for every reaction that produces left-handed neutrinos, there is a comparable reaction that produces right-handed antineutrinos.

Physicists were distraught to discover nature violated C and P, but at least nature was decisive — violating these symmetries 100% of the time. And at least nature preserved CP-symmetry…or so we thought.

About 50 years ago, physicists discovered CP-violation in several decay modes of KL, the long-lived neutral kaon. One of those experiments was my Ph.D. thesis. [“Long-lived” is relative — the KL lifetime is 52 nanoseconds, 578 times longer than the short-lived neutral kaon.]

In KL decays, which involve the strange quark, CP-violation is a 0.3% effect. This is even more distressing than C and P-violation — why is nature 99.7% symmetric?

Theorists showed this tiny effect must be indirect; it could only result if there were as-yet-undiscovered particles mediating these processes. And over the next 25 years, physicists discovered a complete third generation of fermions — the top quark, bottom quark, tauon, and tau neutrino.

In some decays of the bottom quark, CP-violation is as much as 70%. We now know CP-violation occurs both directly in the weak decay processes and indirectly in the mixing of quantum states before decays.

While 50 years of research has improved our measurement precision from 10% to 1%, we still have no clue why CP-violation exists. But, we wouldn’t exist without it.

Without CP-violation, matter and antimatter would have completely annihilated one another, leaving only light.

CP-violation enabled a slight shift in the matter/antimatter balance. In round numbers, by the time the universe was 1 second old, for every 1 billion particles of antimatter, there were 1 billion and 1 particles of matter. The billions annihilated one another, creating the ubiquitous cosmic microwave background radiation (CMB), and leaving only the 1 extra particle per billion of matter.

Everything we see is comprised of the 1-in-a-billion surviving particles of matter.

The exact number is critical. If slightly more matter had survived, the universe would have collapsed into a single black hole. If slightly less matter had survived, the universe would have expanded too rapidly for stars to develop. Only in an extremely narrow range would just enough matter have survived to make our universe habitable.

We know precisely what the survival rate was, but have no idea why it has that specific value. This remains one of our universe’s charming mysteries.

Dr. Robert Piccioni  is an author, experienced public speaker, educator and expert on cosmology and Einstein’s theories. His goal is to present real science to real people in a way that everyone can understand and enjoy.

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