Physicists have been unable to solve the puzzle of what happened when a vanishingly tiny seed exploded into the cosmos for a long time. Now, one physicist believes he understands why scientists haven’t been able to come up with a physical explanation for inflation: the world won’t let us.
The physicist explains a recent theory that states that “the observer should be protected” from actually observing the cosmos’ most minor systems in the early universe.
To put it another way, physicists may never be able to construct a model of inflation using traditional methods and may have to devise a new strategy.
But, well, why not? This latest conjecture, which is an opinion or perception founded on insufficient knowledge, blames an aspect of inflation models in particular. These models magnify very tiny variations in spacetime. But since we don’t have a whole physical theory of such minor fluctuations, models of inflation with that function (which almost all of them do) will never work.
Enter string theory, which could hold the key to unlocking inflation’s mysteries.
Allow yourself to be inflated.
Observations of the universe’s large-scale composition and residual light from the Big Bang have shown that our universe underwent a period of extremely rapid expansion in its infancy. Inflation was a remarkable phenomenon that caused the universe to grow trillions upon trillions of times more significant in a fraction of a second.
In the course of being massive, inflation made our universe a little bumpy. The tiniest random quantum fluctuations — fluctuations constructed into the very structure of spacetime itself — became much, much more prominent as inflation progressed, implying that certain regions became more tightly populated with matter than others. Those sub-microscopic variations eventually evolved to be macroscopic… and much more significant, extending from one end of the universe to the other. Those minute variations in density grew to become the roots of stars, galaxies, and the cosmos’ most significant systems millions and billions of years hence.
And though astronomers believe something similar to this inflation tale occurred in the early moments of the universe, when it was less than a second old, they have no idea what caused inflation, what driven it, how long it lasted, or what turned it off. To put it another way, scientists don’t have a complete physical explanation of this historic occurrence.
In specific inflation models, variations at microscopic scales are exaggerated to become macroscopic disparities, adding to the mix of mysteries. How little is it? 1.6 x 10minus 35 meters is less than the Planck dimension (the number 16 preceded by 34 zeroes and a decimal point). That’s the point at which gravity’s power equals or exceeds the strength of the other fundamental forces of nature. To explain reality at that size, we need a unified theory of physics.
We don’t have such a hypothesis.
As a result, we have a dilemma. Most (if not all) inflation theories call for the universe to expand to such a size that sub-Planckian variations become macroscopic. However, we can not comprehend sub-Planckian mechanics. But how do we construct a theoretical inflation model if we don’t grasp the physics?
Above and beyond the Planck scale
Maybe the answer is: We’ll never be able to. The TCC (Trans-Planckian Censorship Conjecture) is the name given to this definition (in this name, “trans-Planckian” means anything reaching below the Planck length).
An analysis of the TCC was recently published by Robert Brandenberger, a Swiss-Canadian theoretical cosmologist, and professor at McGill University in Montreal, Canada.”The TCC is a modern theory that constrains feasible cosmologies,” Brandenberger says.
According to him, the TCC means that every outsider in our large-scale universe would never be able to “see” what occurs at the tiny trans-Planckian scale. The TCC says that something living in the sub-Planckian regime would never “jump over” into the macroscopic universe, even though we had a theory of quantum gravity. In terms of what the TCC could mean for inflation models, the news isn’t good.
The majority of inflation theories use a methodology called “efficient field theory.” Since we don’t yet have a hypothesis that unifies science at high energy and minor scales (a.k.a. inflation), scientists attempt to develop lower-energy variants to make advancements. However, under the TCC, the technique fails because, when used to construct inflation models, the inflation mechanism occurs so quickly that it “exposes” the sub-Planckian regime to macroscopic observation, according to Brandenberger.
In terms of this, some scientists ask whether we can treat the early universe in a slightly different way.
Out of the mudslide
String gas cosmology is a possible way to simulate the early universe using string theory and is a promising contender for a coherent approach to physics that combines classical and quantum physics. The world in the string gas model never goes through a time of rapid inflation. Instead, the inflation cycle is much gentler and slower, and deviations less than the Planck duration are seldom “exposed” to the macrocosm. The TCC is pleased because physics below the Planck scale never rises to become measurable. On the other hand, String gas simulations lack sufficient information to measure against detectable proof of inflation in the universe.
The TCC is linked to another point of contention between inflation and unified physics theories like string theory. String theory predicts a massive number of possible worlds, of which ours (with its collection of forces and particles, as well as the rest of physics) is only one. At a fundamental level, it seems that most (if not all) inflation models are incompatible with string theory. Instead, they belong to the “swampland,” a field of alternate worlds that aren’t scientifically plausible.
The TCC may be a manifestation of the swampland’s anti-inflationary stance.
It might still be possible to construct a conventional model of inflation that satisfies the TCC (while remaining outside of string theory’s swampland); but, if the TCC is valid, the types of models that physicists may construct are minimal. Inflation theory could succeed if it can continue for a long enough time (imagine slowly blowing up a balloon and stopping until it pops) while also planting the seeds that would eventually develop into large structures.
The TCC is currently unproven — it’s just a theory. It corresponds to other string theory lines, but string theory is unproven as well (the approach isn’t complete and can’t make predictions yet). However, concepts like this are helpful because physicists fundamentally do not appreciate inflation, and something that can help them think more clearly is welcome.
