5 June 2016

Sci-fi Tropes: Expanding possibilities...

By NASA / WMAP Science Team - http://map.gsfc.nasa.gov/media/121238/ilc_9yr_moll4096.png, Public Domain, https://commons.wikimedia.org/w/index.php?curid=23285693
By NASA / WMAP Science Team - Public Domain

I've had a pet theory for a long time now. Actually, it's more of a questioning observation:

Is the universe really expanding?

Now, don't get me wrong! I understand that we are observing the expansion of our visible universe as the physical objects in that visible sphere* are moving further apart. I just see that there is another scenario where that same local 'viewing' of our universe would result in the same or very similar understanding.

There is a recent article on New Scientist that has prompted this line of thinking to come to the fore in my mind, wherein a discrepancy between measurements of the rate of expansion of the universe means that there might be a 9% increase. It's important to note that it may be an error in our accuracy so it's still too early to get overly excited about this observation - much like the faster than light neutrinos!

If this increase in rate is true then it might lend credence to my pet theory. As a by-product, it also nullifies the dark energy theory because there is no need to "make up" an energy source to cause the expansion - the expansion we observe is just an intrinsic aspect of the universe.

Let me explain.

Glogger, water draining from a pool.

The theory is simple (at least at the basic premise) - the universe is actually contracting to a singularity.

Think of it a bit like the image above. We have a singularity at the very centre of the universe in much the same way we do at the centre of our galaxy. It's beyond our observable portion of the universe (which we predict is infinite due to space curvature). We're part of the great mass of sandy particles that lies on the inward spiralling whirlpool of contraction. You could say we're approximately just to the right of the middle of the picture and the hole in between the two 'arms' of the spirals in what is basically similar case to a spiral galaxy like below:

R. Hurt's illustration of what we think the Milky Way looks like. Plus some additional crosses from yours truly...

'X' marks the spot - or one of the potential spots where our miniscule portion of the universe lies in this scenario. All the other similar places have been left out for clarity.

Before I have to explain the fridge logic here, I should underpin this wacko theory even further: Charles Francis and Erik Anderson put forth the theory of gravitationally aligned orbits to support the formation and retention of spirals in spiral galaxies. This theory is supported by (and derived from) observation of the orbits of a good number of stars in the local space around our own. This theory is sort of a descendant of the theory put forth by C.C. Lin and F. Shu whereby stars moved around the central gravity sink (singularity) in slightly elliptical orbits caused by spiral density waves. Personally, I quite like the elegance of Francis and Anderson's suggestion and it also fits with my pet theory quite nicely.

What the theory says is that stars orbit the black hole of the Milky Way in an eccentric manner but which are also drawn to each other as their mass and the mass of clouds of stellar gas bunch together. In order words, the spirals form because the orbits of the matter around the black hole have become interlinked. According to the theory, the stars are able to leave the spiral arms that they dynamically form due to their velocity at the pericentre of their individual orbit and break free of the gravitationally dense region that comprises the spiral arm, only to join it or another arm when they near the apocentre of their orbit and their relative velocity is at its lowest.

The important thing is, as the stars leave the spiral arm on their journey to their apocentre, all the other stars and matter that is on a similar orbit will also be around those stars. The trailing stars and matter will experience more drag than those preceding them based on their proximity to the gravity well of the spiral arm. Thus to a star in the middle of an ejecting mass, the preceding stars would appear to accelerate away whilst the trailing stars would also appear to accelerate away.

Thus, if the observable universe was limited to the volume of the ejected mass then an observer in the centre of that volume of space would not understand that the universe was contracting on the large scale.

Of course, this particular example relies on a two dimensional representation of the volume of space involved and, unfortunately, I haven't seen an explanation or theory as to how the bulge of the Milky Way comes into these calculations. It's possible that matter on multiple trajectories will also join and leave the spirals as well (say from a large, globular merging galaxy or nebula), which would also explain our current observations that matter is accelerating away in all directions. This is the weakest part of this very hypothetical theory - it's entirely possible that the mathematics just doesn't work in three dimensions and you would not observe all matter moving away from you in this scenario.

So there you have it: The local universe is definitely expanding in all directions... but is the entire universe also expanding? Could we even tell? Does it even matter?

Difficult questions to answer.

*Close enough...

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