1
$\begingroup$

How might cosmic inflation affect chemistry and nuclear interactions?

Hypothetically, if I am alone (wearing a spacesuit) in a large but empty universe, and the inflation of this universe is such that 1 meter becomes 2 meters every 60 seconds, what will happen to me?

$\endgroup$
0

3 Answers 3

0
$\begingroup$

If the question had been about our actual universe at the time when it hypothetically underwent inflation ($\sim10^{-33}$ seconds), in the most common inflationary models, then the answer would have been that the density and temperature are so high that you are instantly annihilated, and nuclei can't even form yet out of the quark-gluon plasma. We don't even have to worry about whether gravitational fields could kill you or not, because the hot, dense matter fields aren't even going to allow you to start out by existing.

Hypothetically, if I am alone (wearing a spacesuit) in a large but empty universe [...]

But you're talking about a hypothetical different universe, so the answer to your question depends on what physics you're choosing for your universe. Depending on your choices, most likely the decay of the vacuum out of its metastable state is a violent process involving the release of a lot of ionizing radiation, even if the universe was empty before inflation began. This radiation would presumably vaporize you instantly.

You can say that you want the inflation without the deadly matter, but this is impossible. A cosmology with exponential expansion is not a vacuum solution of the field equations of general relativity. According to general relativity, under a certain set of reasonable assumptions, the effect of cosmological expansion on matter is to produce strain proportional to $\dot{\rho}$, the rate at which the density of matter is decreasing. For a vacuum, $\rho=0$ and therefore $\dot{\rho}=0$. (Other answers are possible, e.g., in a Big Rip scenario, which violates the assumptions given in the linked answer above.)

$\endgroup$
7
  • $\begingroup$ Thank you for answering. :) So you are saying that a higher rate of inflation would mean a higher probability of the vacuum decaying out of its metastable state, is that correct? Also, I don't understand why a "cosmology with exponential expansion" is required. Our own real universe appears to be expanding at an increasing rate. Eventually, the rate of expansion really will be such that 1 meter becomes 2 meters every 60 seconds, will it not? $\endgroup$
    – cowlinator
    Commented Nov 9, 2018 at 23:40
  • $\begingroup$ @cowlinator: * So you are saying that a higher rate of inflation would mean a higher probability of the vacuum decaying out of its metastable state, is that correct?* No, the decay is what causes inflation to happen. Also, I don't understand why a "cosmology with exponential expansion" is required. Our own real universe appears to be expanding at an increasing rate. Exponential expansion is one of the defining characteristics of inflation. "Exponential" doesn't just mean "accelerating," it means a function like $e^t$. Inflation is not a synonym for cosmological expansion. $\endgroup$
    – user4552
    Commented Nov 10, 2018 at 2:57
  • $\begingroup$ Eventually, the rate of expansion really will be such that 1 meter becomes 2 meters every 60 seconds, will it not? No, as it becomes more and more dominated by dark energy, the expansion will become closer and closer to an exponential, but the doubling time will essentially be constant at billions of years. $\endgroup$
    – user4552
    Commented Nov 10, 2018 at 2:59
  • $\begingroup$ @cowlinator Wikipedia's "Lambda-CDM model" explains that the scale factor is varying as $a(t)=(\Omega_m/\Omega_\Lambda)^{1/3}\sinh^{2/3}{(t/t_\Lambda)}$ where $t_\Lambda=2/(3H_0\sqrt{\Omega_\Lambda})$. This means at large $t$ the e-folding time is $\frac{3}{2}t_\Lambda$ and the doubling time is $\ln{2}$ times this or $\ln{2}/(H_0\sqrt{\Omega_\Lambda})$. Putting in the Hubble time $1/H_0=14.4$ billion years and the dark energy density parameter $\Omega_\Lambda=0.6911$ gives a scale-factor doubling time of $12.0$ billion years, as Ben Crowell explained. $\endgroup$
    – G. Smith
    Commented Nov 10, 2018 at 6:09
  • $\begingroup$ @cowlinator In case you're wondering how the Big Rip occurs if the doubling time stays billions of years... The Big Rip is not because the doubling time goes to zero, but because the size of the observable universe goes to zero. $\endgroup$
    – G. Smith
    Commented Nov 10, 2018 at 6:12
0
$\begingroup$

Matter (leptons and quarks) is thought to be produced (from inflaton field) after inflation, in the reheating process. So inflation doesn't directly affect chemistry, it just sets the stage for the subsequent processes where the conventional "chemistry" is created. One of them is the big bang nucleosynthesis.

$\endgroup$
-1
$\begingroup$

How might cosmic inflation affect chemistry and nuclear interactions?

Cosmic inflation is continually happening in the cosmos, clusters of galaxies are expanding away from each other, and we do measure clusters of galaxies, their distances and velocities. And even we have measured an accelerated rate, attributed to inflation over the normal expansion measured by the Hubble constant and described by the Big Bang cosmological model.

Evidently, by construction, if everything was expanding, then one would never know it, because the units would be expanding accordingly. Meters and seconds are a matter of definition after all. If the defining measure is expanding there would be no way to know it.

What is happening can be understood by quantifying the forces holding matter together, in our present units. The weakest of all forces as seen in the table is gravitation. The fact that clusters of galaxies are not dispersing, means that the gravitational force holding them together is much stronger than the impulse conveyed to the galaxies within the cluster, so the galaxy cluster keeps together, and the same is true for gravitational systems down to stars and planets. Much stronger are the electromagnetic and strong forces keeping atoms and nuclei together, so the current expansion does not affect us, similar to the raisins in the dough analogy for the expansion. The raisins are tightly bound and are not puffed like the dough.

What is the measured number of the current expansion?

The H0liCOW estimate puts the Hubble constant at about 71.9 kilometers (44.7 miles) per second per megaparsec (one megaparsec equals about 3.3 million light-years). In 2015, another team, using observations of the cosmic microwave background, determined the rate was 67.8 kilometers per second for megaparsec. And last year, a different team, using observations of Cepheid stars and supernovae put it at 73.2 kilometers per second for megaparsec. That figure was higher than most earlier estimates, and surprised many astronomers. Hubble’s own estimate—500 kilometers per second for megaparsec—was way off, but such is the nature of discovery when the right technology isn’t around yet.

This is a very tiny number, for meter dimensions, as seen here , ~$2e^{-18}$meters per second.

Hypothetically, if I am alone (wearing a spacesuit) in a large but empty universe, and the inflation of this universe is such that 1 meter becomes 2 meters every 60 seconds, what will happen to me?

This is answered by Ben , and more assumptions have to be provided. Considering the numbers for our stable universe, the expanding impulse would rip you apart, as you are assuming expansion rates seen in the beginning of the universe.

$\endgroup$
2
  • $\begingroup$ Cosmic inflation is continually happening in the cosmos, clusters of galaxies are expanding away from each other, and we do measure clusters of galaxies, their distances and velocities. No, inflation is a different phenomenon from cosmological expansion. $\endgroup$
    – user4552
    Commented Nov 11, 2018 at 15:13
  • $\begingroup$ @BenCrowell I am answering the chemistry part, which certainly does not exist during inflation $\endgroup$
    – anna v
    Commented Nov 11, 2018 at 15:24

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.