Sometimes observations are hard to explain. So you just have to tack on the best ad-hoc explanation that fits the facts, even if the explanation itself is lacking the nitty-gritty details. Astronomy went through such an exercise when anyone who was anyone said that the Earth was the centre of all things, and all things revolved around the Earth. That didn’t end very well. I suspect that modern cosmology is in a similar situation that ultimately won’t end well as far as the status quo is concerned either.
Continued from yesterday’s blog...
So how does an extreme, but brief, burst of expansion (i.e. – Inflation) solve the flatness, horizon and monopole issues?
The horizon problem is solved by inflation. While, initial pre-inflation Big Bang conditions would have provided for the required close enough contact to achieve uniformity, regions flying apart would soon acquire their own distinct ‘personalities’ and be far enough apart that equilibrium could never be restored between these regions, even at light speed. However, that additional serious bout of Inflation then rapidly expanded out that evenness, Inflation providing the extra oomph and freezing the uniformity in place to the distances we observe today.
The flatness problem is explained because an extremely rapid rate of Inflation would smooth out the Universe. If you’re bacteria on the surface of an uninflated balloon, you’ll see peaks and troughs – wrinkles. If that balloon is blown up thousands of times greater in extent, the surface will now appear flat – just like the surface of the Earth appears flat to us.
The monopole problem is solved because the volume of the Universe increased thousands of times over in nanoseconds such that monopoles were now dispersed over an incredibly large volume such that the odds one would be in our cosmic neighbourhood becomes vanishingly tiny.
The odd thing here is that I sometimes read that Inflation preceded the Big Bang, although it’s usually an after-the-fact event. Obviously cosmologists haven’t really a clue which came first – no, not the chicken or egg but the Big Bang or Inflation.
Okay, we’ve explained cosmological observations via the Big Bang and Inflation. Can we go on R&R now? No, not quite. For you see, yet another very nasty observation has surfaced that requires yet another ad hoc tack-on explanation that well, has no explanation.
We have been aware that our Universe has been expanding for going on nearly a century now. Of course we are also aware, from a quite considerable earlier time that what goes up must come down. In other words, gravity grabs. The Universe has lots and lots of gravity, so presumably, what goes up (i.e. – the expansion rate) must come down (i.e. – the expansion rate must at least slow down, maybe even stop and reverse). Cosmologists were very interested in finding out exactly what the rate of deceleration was. How fast was the Universe’s expansion rate decreasing? It’s like you car might be going uphill, but at an ever slower and slower rate.
Okay, so, several teams of astronomers did the relevant observations and crunched the numbers and guess what – the Universe’s expansion rate was accelerating, and gravity be damned. That’s sort of like driving your car uphill and having it go faster and faster without you putting the pedal to the metal. Well, that surely was an unexpected result. So, they needed an explanation. The astronomers (team leaders anyway) got the Nobel Prize, but that was for the discovery, not for the explanation. You see, there wasn’t any explanation. So, what do we want – an epicycle. When do we want it – now! What was the ad-hoc epicycle to be? It was called “Dark Energy”, a sort of antigravity that was pushing the Universe apart faster and faster and faster. Trouble is, nobody then, or now, has the foggiest idea what Dark Energy is, yet in order to account for what this epicycle does, it must represent some roughly 70% of what makes the Universe up. That’s a lot of epicycle that lacks any plausible explanation. Did someone mention rabbits and hats?
Now can we go home? Sorry, not yet.
There’s yet another astronomical observation that in fact goes back to the first half of the 20th Century that has to deal with, at least initially, our own cosmic neck of the woods, the Milky Way Galaxy. Now you’d be well aware that in our solar system, Mr. Sun is the Big Cheese and keeps all of her planets in orbit via her gravity. However, gravity weakens as you get away from the source (the inverse square relationship) so it’s not surprising that the farther a planet is outward bound from the Sun, giver the ever increasingly longer distance of its orbit around the Sun, the slower it orbits; the longer is its year. Now does that relationship apply to all the bits and pieces (i.e. – stars) that orbit around the centre of our galaxy? Well, in fact no. The outer stars whiz along just as quick-smart as the inner stars, so much so that the outer stars, given the amount of gravity the galaxy apparently has, should in fact escape altogether and head off into intergalactic space. The fact that they don’t does mean the galaxy has a lot more gravity than apparently meets the astronomical eye. Oops, there’s another epicycle coming on. This time the ad-hoc explanation is Dark Matter. It is dark because we can’t see it. It is matter because it has (all that required additional) gravity. Of course, it makes up the majority of matter in our galaxy; of course nobody has a clue what it actually is, although the astronomical powers-that-be have been able to rule out a lot of what’s dark, but common stuff like interstellar gas and dust, Black Holes, etc. So, for the here and now, Dark Matter is another epicycle, and what applies to our galaxy also has been observed for other galaxies.
The concept of epicycles was originally used in order to explain observations. That remains the case in modern cosmology, only the ad-hoc explanations themselves need explaining.
In conclusion, the state of cosmology and of our understanding of the Universe, its substance and structure, is pretty much at a crossroads where the state of our solar system was all those centuries ago. Once upon a time epicycles were heaped on epicycles in order to explain the solar system until everything fell to pieces. I suspect that history will repeat itself when it comes to the current state of cosmology. Explanations of observations are just too ad-hoc; too many things left unexplained by those ad-hoc epicycles. We’ve had the Copernican Revolution; it’s time for the equivalent revolution in cosmology.
SUMMARY
Observation: Galactic Redshifts
Observation: Cosmic Microwave Background Radiation (CMBR)
Observation: Ratio/Abundance Hydrogen & Helium
Ad Hoc Epicycle: Big Bang (no energy source given)
Observation: Horizon Problem
Observation: Flatness Problem
Observation: Magnetic Monopoles
Ad Hoc Epicycle: Inflation (many varieties, just like Heinz)
Observation: Accelerating Universe
Ad Hoc Epicycle: Dark Energy (unexplained)
Observation: Galactic Rotations with Gravity Out of Sync
Ad Hoc Epicycle: Dark Matter (unexplained)
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