The Big Rip

Not the chile, nachos, and beer, big rip many of you may be familiar with. No the fate of the universe has a few differing conclusions by the notable smarty pants scientists, physicists, and mathmeticians way above my pay grade, of whom I am greatly indebted to for their services. These conclusions fall into three main categories.

First there is the Big Crunch, where it is thought by some that the expansion of the universe will gradually slow, and then fall back in upon itself. Creating a big crunch calamity where all matter recondenses into, what I understand, an enormous black hole state, that may be able to repeat the singularity event that is believed to have started the universe as we know it.

Then there is the Big Freeze, where the universe expands so far that the gases needed for new star formation is spread so thin that star formation ceases, the universe grows cold, and dies a lonely death.

Finally we have the Big Rip, the Big Rip takes into account what is thought to be driving the expansion of the universe. This cause has been labeled dark energy. Dark energy is an as of yet, unproven entity, however it is almost sure to exist, we just haven’t exactly determined the how or why it exists, or how to detect it. The only way we can tell it is there is by studying how it infuences the matter we can detect, and measure the effects of the matter as it relates to the expansion we know is happening. Did that make sense? The Big Rip theory generally claims that over time the universe basically strectches beyond its capability to stretch and everything pretty much flies apart, even at the atomic scale.

A team from Vanderbilt University, right here in my home state of Tennessee, (thus lending some credibility to the notion that we aren’t all a bunch of bible addled hillbillies) released a paper earlier this year, the result being some new math that appears to favor the Big Rip outcome. I should note the key players involved with the paper, and I quote:

The new approach was developed by Assistant Professor of Mathematics Marcelo Disconzi in collaboration with physics professors Thomas Kephart and Robert Scherrer and is described in a paper published earlier this year in the journal Physical Review D.

BigRip

This new math concerns itself with cosmological viscosity. Cosmological viscosity? Now admittedly, I am not familiar with cosmological viscosity. This viscosity is thought to have a similar effect on universe expansion as is expected of dark energy. This paper and its math takes into account this viscosity and its effects. I tried to do some research on this subject and quickly ran into info behind paywalls, although I did find this:

http://www.researchgate.net/profile/Suresh_Kumar187/publication/225118853_Viscous_fluid_cosmology_with_a_cosmological_constant/links/00b495201c90cb1633000000.pdf

…but that quickly devolved into some chicken scratch math I have no comprehension of.

Then I found this page:

http://physics.stackexchange.com/questions/192147/cosmological-bulk-viscosity-is-the-universe-a-fluid

Where someone (who apparently had access to the paper, or payed for it) was trying to make heads or tails of this cosmological viscosity thing and asked a question there to see if he could get a clarification. One of the answers was thus: Protip: Just about anything on arxiv posted to gr-qc and cross-posted to astro-ph is pseudoscience. (Yes, this offends lots of people employed as “scientists.” No, I will not back down on this claim.) –  Chris White (end quote)  Note that this paper is available on arvix.org if you would like to pay for it.

So I’m not exactly sure how seriously I should take all of this viscosity stuff, but let’s continue. I don’t like to stick my neck out and report on something I am not at least a little familiar with, but let’s assume for the sake of argument this cosmological viscosity thing is real and has a measurable effect on our universe. This next paragraph offers an interesting theory, quoted in full:

Most dark energy theories to date have not taken cosmic viscosity into account, despite the fact that it has a repulsive effect strikingly similar to that of dark energy. “It is possible, but not very likely, that viscosity could account for all the acceleration that has been attributed to dark energy,” said Disconzi. “It is more likely that a significant fraction of the acceleration could be due to this more prosaic cause. As a result, viscosity may act as an important constraint on the properties of dark energy.”

If there is anything to this possibility it does raise some interesting aspects to the dark energy problem. I’m not real sure yet if they are offering a solution to a problem, that may have its own problems just yet though. All I can say is they are pretty sure this new math poses a distinct possibility to consider. Here is a little more info from the article, relevant to cosmic viscosity, that might help.

The type of viscosity that has cosmological relevance is different from the familiar “ketchup” form of viscosity, which is called shear viscosity and is a measure of a fluid’s resistance to flowing through small openings like the neck of a ketchup bottle. Instead, cosmological viscosity is a form of bulk viscosity, which is the measure of a fluid’s resistance to expansion or contraction. The reason we don’t often deal with bulk viscosity in everyday life is because most liquids we encounter cannot be compressed or expanded very much.

Disconzi began by tackling the problem of relativistic fluids. Astronomical objects that produce this phenomenon include supernovae (exploding stars) and neutron stars (stars that have been crushed down to the size of planets).

Scientists have had considerable success modeling what happens when ideal fluids — those with no viscosity — are boosted to near-light speeds. But almost all fluids are viscous in nature and, despite decades of effort, no one has managed to come up with a generally accepted way to handle viscous fluids traveling at relativistic velocities. In the past, the models formulated to predict what happens when these more realistic fluids are accelerated to a fraction of the speed of light have been plagued with inconsistencies: the most glaring of which has been predicting certain conditions where these fluids could travel faster than the speed of light.

“This is disastrously wrong,” said Disconzi, “since it is well-proven experimentally that nothing can travel faster than the speed of light.”

So, I take it that this new idea allows for a cosmic viscosity that doesn’t violate the speed of light. That would be an important hurdle to clear. Honestly I’ve been in over my head for a while now, but I can see the other side, and if I flail around a little longer I believe I can get to the other side. With that in mind I will quote the last few paragraphs of the article to offer further explanation as to how this new theory applies:

In reference to the Big Rip. “It is predicated on a type of “phantom” dark energy that gets stronger over time. In this case, the expansion rate of the universe becomes so great that in 22 billion years or so material objects begin to fall apart and individual atoms disassemble themselves into unbound elementary particles and radiation.

The key value involved in this scenario is the ratio between dark energy’s pressure and density, what is called its equation of state parameter. If this value drops below -1 then the universe will eventually be pulled apart. Cosmologists have called this the “phantom barrier.” In previous models with viscosity the universe could not evolve beyond this limit.

In the Desconzi-Kephart-Scherrer formulation, however, this barrier does not exist. Instead, it provides a natural way for the equation of state parameter to fall below -1.

“In previous models with viscosity the Big Rip was not possible,” said Scherrer. “In this new model, viscosity actually drives the universe toward this extreme end state.”

According to the scientists, the results of their pen-and-paper analyses of this new formulation for relativistic viscosity are quite promising but a much deeper analysis must be carried out to determine its viability. The only way to do this is to use powerful computers to analyze the complex equations numerically. In this fashion the scientists can make predictions that can be compared with experiment and observation.”

So, if you are still with me and haven’t fallen asleep, the new theory appears to harmonize with speed of light problems. Offers an explanation that either coincides with dark energy or perhaps removes the necessity of it. Lends some credence to the Big Rip, and may help adequetely describe the observations we already have. Admittedly there is a lot of work to do yet to achieve additional support for this theory. There is a lot of speculation, especially on my part, but it is an interesting side show for now. If you’re into that sort of thing.

I’ll be waiting for Sheldon to weigh in on the matter. 🙂

My initial source:

http://news.vanderbilt.edu/2015/06/new-model-of-cosmic-stickiness-favors-%E2%80%9Cbig-rip%E2%80%9D-demise-of-universe/

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Let’s Slow This Thing Down A Little Bit…

The universe that is. According to a Peter A. Milne of the University of Arizona, the standard for measuring universe acceleration, the type 1A supernova, is not quite as standard as they initially thought. There are at least two types of type 1A supernova detected in the recently accumulated data.

Apparently the trick, the key to the new data was looking at the supervovae in ultraviolet light. There is a different aspect noticed between ultraviolet and visible light. They detected this difference with data from Swift, NASA’s orbital satellite with ultraviolet detectors, and compared them to observations from Hubbles visible light observations. The difference appears to be, and I’ll quote the source, first with our old data:

“The faraway supernovae should be like the ones nearby because they look like them, but because they’re fainter than expected, it led people to conclude they’re farther away than expected, and this in turn has led to the conclusion that the universe is expanding faster than it did in the past.”

Then with the new data:

“As you’re going back in time, we see a change in the supernovae population,” he added. “The explosion has something different about it, something that doesn’t jump out at you when you look at it in optical light, but we see it in the ultraviolet.

“Since nobody realized that before, all these supernovae were thrown in the same barrel. But if you were to look at 10 of them nearby, those 10 are going to be redder on average than a sample of 10 faraway supernovae. (edit: Referring to red shift/blue shift, basically red shift means it is moving away from us and blue shift moving towards us. There are  numerical increments that determine how far away an object is based upon its brightness. Which means we were getting false assumptions because of wrongly expecting the supernovae were very similar)

The authors conclude that some of the reported acceleration of the universe can be explained by color differences between the two groups of supernovae, leaving less acceleration than initially reported. This would, in turn, require less dark energy than currently assumed.” (end quote)

What this all amounts to is, the universe while it is still expanding, may be expanding slower than we thought. They still have to crunch the numbers to see how much slower we are talking about. It also means we might get closer to understanding the amount of dark matter there is out there. As I understand it, with the previous observational data, there is too much dark matter to accurately account for. This finding could help resolve that issue. Which is cool, I’m always happy to see a missing piece of a puzzle fall into place. Especially when that piece gets us closer to understanding the things we don’t yet know. I came across this story @ Science Daily but the original source is here:

http://uanews.org/story/accelerating-universe-not-so-fast