Any compelling origin story seeks to explain traits of someone or something. How past events shaped what we currently observe or experience. The Big Bang theory for the observable universe is a tall order.
(Wiki) The model … offers a comprehensive explanation for a broad range of observed phenomena, including the abundance of light elements, the cosmic microwave background (CMB) radiation, and large-scale structure.
How do the known laws of physics play into this model? Moving forward and backward in time. Do the assumptions of the cosmological principle stand up?
This article (below) reminded me about the mystifying timescale for an aspect of the Big Bang theory – cosmic inflation – that, while essentially accepted, remains a subject of ongoing research. Research seeking To Tell the Truth among various models: Will the real model of cosmic inflation please stand up?
What do the BICEP (Background Imaging of Cosmic Extragalactic Polarization) experiments tell us?
• Symmetry Magazine > “BICEP3 tightens the bounds on cosmic inflation” by Nathan Collins (10/26/2021)
(quote) the latest results from the BICEP3 experiment at the South Pole have tightened the bounds on models of cosmic inflation, a process that in theory explains several perplexing features of our universe and which should have produced gravitational waves shortly after the universe began [leaving an imprint on the polarization of light in the CMB].
Here’s how the article notes the mind-boggling timescale for inflation. Yikes! 
(quote) Cosmic inflation is the idea that very early in the history of the universe, the amount of space in the universe exploded from roughly the [spherical] size of a hydrogen atom [~1.1 x 10^-10 m in diameter] to about a light-year across [~9.46 x 10^15 m in diameter], in about the time it would take light to travel one-trillionth [10^-12] of the way across the same atom.
Wiki just notes that:
“At approximately 10^−37 seconds into the expansion, a phase transition caused a cosmic inflation, … [which] stopped at around the 10^−33 to 10^−32 seconds mark, with the universe’s volume having increased by a factor of at least 10^78.”
So, why does the article talk about ruling out models? Merely fine tuning? 
(quote) Inflation can explain a lot—notably, why the universe appears to be fairly smooth and look the same in all directions, why space is flat and why there are no magnetic monopoles. Still, physicists have not succeeded in working out the exact details, and they have come up with many different ways inflation might have occurred.
Check for imprints of those primordial gravitational waves, eh.
(quote) The results rule out a number of inflation models, including some popular older models and some versions of newer ones motivated by string theory, says Silverstein [Stanford theoretical physicist Eva Silverstein]. The findings suggest that the correct model will be slightly more complicated that those that have been ruled out, although there is still a wide range of viable alternatives. “It’s not as though we’re going back to the drawing board,” Silverstein says, but the results “help us focus.”
This is big science. Unraveling the “sacred scroll” of the cosmic microwave background requires exceptional, heroic patience. Not something for Captain Kirk 😉
 “The Big Bang is not an explosion in space, but rather an expansion of space.” And normal scaling of space over time has a hiccup.
Space-time, as a sort of material, need not attend to any cosmic speed limit (as does whatever is moving within that material).
 By my rough calculation, that’s ~0.4 x 10^-30 seconds to expand (spherically) in volume by a factor of ~10^78.
Width of hydrogen atom = ~1.1 x 10^-10 m
One-trillionth (10^-12) of that = ~1.1 x 10^-22 m
Speed of light = ~3 x 10^8 m/s
So, time to travel = ~0.4 x 10^-30 s
A Planck unit of time is ~5.39 × 10^-44 s and Wiki notes: “As of October 2020, the smallest time interval uncertainty in direct measurements was on the order of 247 zeptoseconds (2.47 × 10^−19 s).”
A light-year = ~9.46 x 10^15 m
(9.46 x 10^15)^3 / (1.1 x 10^-10)^3 = ~10^78 factor for increase in volume
 Wiki notes:
(quote) The detailed particle physics mechanism responsible for inflation is unknown. The basic inflationary paradigm is accepted by most physicists, as a number of inflation model predictions have been confirmed by observation; however, a substantial minority of scientists dissent from this position.
2 thoughts on “Size of an atom to light-year sphere instantly – cosmic inflation’s burp”
A new twist on more contemporary acceleration of the expansion of the universe.
• Scientific American > “Could Gravity’s Quantum Origins Explain Dark Energy?” by Conor Purcell (October 28, 2021) – A potentially transformative theoretical study links a new model of quantum gravity with the universe’s bizarrely accelerating rate of expansion.
Here’s a short tutorial on the Cosmic Microwave Background, a key tenet of modern cosmology and topic of ongoing research in astrophysics. The video has some helpful visualizations (something that’s outside the budgets of some science communicators).
• YouTube > Fermilab > “What is the Cosmic Microwave Background?” by Don Lincoln (Dec 1, 2021) – A treasure trove of information about the cosmos, the remnant fireball of the Big Bang.
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