Galactic Interactions

Every so often you will come across somebody who has a "killer" list of "problems" with the Big Bang. While there remain unknowns and questions about the Big Bang— just as there do with biological evolution— the basic picture of the Big Bang is rock solid— just like evolution.

Nearly two months ago, I received a query from somebody who found my name through the Clergy Letter Project "expert database" regarding one of the websites that lists these objects. I've been through quite a number of life changes in the last 6-8 weeks, and my blogging rate has suffered as a result. However, I'm finally getting to it. Nearly all of the things I will respond to here are generic responses, as these "objections" to the Big Bang are frequently brought up, but for reference I will link to the site that was given to me: Dr. Tom van Flandern's Top 30 Problems with the Big Bang. Nearly all of these objects are either a misunderstanding of the Big Bang, or an objection that is out of date. I won't address all 30 individually, but I will hit some of the highlights. The fact that I don't address a given objection should not be taken as evidence that I'm ceding the point!

Objection 1 : Bad Fits to Data

The first objection I will quote in its entirety, because not only does it contain false information, but it contains a more general canard that is often used when objecting to scientific theories:

This is incorrect on several fronts. First of all, we get very good and precise fits from the Big Bang model. Additionally, the "cosmic deceleration parameter" turns out to be negative. It was true 10 years ago that different lines of reasoning suggested different values for this parameter, but the truth was that we really hadn't been able to make a good measurement of it. Now we have, and the acceleration of the Universe fits with sundry lines of reasoning— so much so that now have what is frequently called "standard model" of cosmology, or a "concordance cosmology", with the various parameters (expansion rate, overall density, dark energy density, age of the Universe, etc.) measured each to within 5%. This agreement is now nearly a decade old; here is a link to a 1999 Science abstract about the concordance, and here is a link to a preprint site that has the full text.

This objection also points out something that I will probably devote an entire post to in the future: a misuse of Occam's Razor. Too often people object to a scientific theory on the basis that they have a "simpler" theory which must be favored because of Occam's Razor.

Objections 2 and 3: the CMB and Element Abundances aren't fit well

Both of these are quite wrong. Indeed, the cosmic microwave background is well-fit in detail in the Big Bang model; consider, for example, the recent(ish) WMAP 3-year results (paper, press release and pretty pictures.) Likewise, we do achieve consistency in Big Bang Nucleosynthesis models with observed element abundances, given uncertainties in the measurements. The number of adjustable parameters needed to match this consistency is in fact not very large, but I'll address that later.

Objections 4: Too much large-scale structure

In fact, detailed structure formation models starting from the perturbations seen from the Cosmic Microwave Background (which is 300-400 thousand years after the Big Bang) and propagating forward to today do an amazingly good job of predicting the very largest scale structure. We do have filaments and voids. Both of the two new astronomy professors at Vanderbilt, Kelly Holley-Bochelmann and Andreas Berlind, are experts on this. It was, I believe, in Andreas' job talk where he showed us two maps: one was an astronomical survey, the other was from calculations. He challenged us to tell him which was the data, which was the model; of course, we couldn't.

Objection 6: The ages of globular clusters appear older than the universe.

This objection is simply 10 years out of date. Yes, it was true 10 years ago that there was a cosmological "age crisis." The most plausible models of the Universe seemed to favor a Universe that was less than 10 billion years old, whereas the oldest globular clusters were observed to be 12-13 billion years old.

Today, there is no conflict. The major change was the discovery of the accelerating Universe. The addition of dark energy affects the age estimates we get in the Big Bang model, and now we have a measurement of the age of the Universe that is 13.6 billion years, good to about 5%... and no longer in any conflict with age data from globular clusters.

Objection 8: Invisible dark matter of an unknown but non-baryonic nature must be the dominant ingredient of the entire universe.

And?

I mean, yes, this is true. This is one of the big mysteries in cosmology (and, perhaps particle physics) right now. What is Dark Matter? The fact that it is there (and, we know it is there; see also these slides from a talk I gave back at an astronomy journal club back when I was still a professor at Vanderbilt).

The website brings up Milgrom's "MOND", which was originally put forward as an alternative to dark matter to explain galaxy dynamics. However, the aforelinked results from the Bullet Cluster have shown beyond a doubt that there is matter in the Universe that is not where baryonic matter is. Exotic Dark Matter exists. We know that, independent of any considerations involving modelling the Big Bang.

Objection 10: The open Universe requires extreme fine tuning

This one has gone away, but the whole issue of "cosmological fine tuning" hasn't; that remains an outstanding question in the Big Bang.

However, once again this website is about 10 years out of date by referring to the "open" Universe. Current cosmic microwave background data favors a flat Universe, and has since about 1998 or 1999. What's more, the most recent WMAP results linked above provide support for the "inflation" scenario that explains why the Universe should be so close to exactly the critical density needed to make it flat.

Etc.

There is other misinformation in the article. For instance, it mentions quantized redshifts, which are something that's been suggested by data in the past, but which is no longer believed to be true. Given the filamentary nature of the Universe, if you take a "pencil-beam" survey you will observe what appears to be quantized redshifts, because your pencil beam will go through voids. We now have enough large-area surveys to see the full large-scale structure, and see the shape of those voids (and the aforementioned success in modelling them) to understand why pencil-beam surveys sometimes appeared to indicate quantized redshifts. The First Law of Thermodynamics is mentioned, but just as with almost every other time somebody uses a law of thermodynamics to argue against a well-accepted theory (and you know what I'm talking about here), it represents a misunderstanding of thermodynamics.

For other detailed complaints, where I don't have the answer off of the top of my head, it would take me more work to really address it. However, the major points are addressed above. Overall, the objections in that web page— which summarize most of the objections one usually sees to the Big Bang— are either flatly incorrect, are out of date, or are outstanding questions that remain to be answered but do not invalidate the overall picture of the Big Bang.

Yes, questions remain! That's part of what's exciting about it. But the overall picture of the Big Bang is supported now by a wealth of observations, models, theory, and comparison between the three. As I noted in my classic post "Big Bang" is a terrible name for a great theory, we don't really know anything about the moment of "Bang" itself... hence the name of the theory not being so great. But the overall picture of a homogeneous and isotropic (on large scales) Universe that has expanded from an extremely hot and dense state is what all of the data point to.