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an objection that is out of date.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:
(1) Static universe models fit observational data better than expanding universe models.
Static universe models match most observations with no adjustable
parameters. The Big Bang can match each of the critical observations,
but only with adjustable parameters, one of which (the cosmic
deceleration parameter) requires mutually exclusive values to match
different tests. [[2],[3]] Without ad hoc theorizing, this point alone
falsifies the Big Bang. Even if the discrepancy could be explained,
Occam's razor favors the model with fewer adjustable parameters [than]
the static universe model.
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.
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More like this
Back with a bang :o)
Nice to see you posting again.
He makes an interesting point about the phenomenological MOND model being better than the more fundamental dark matter model because the prior doesn't have "fudge factors." Science would be a lot simpler if we replaced these complex, detailed theoretical models that have all sorts of parameters to measure with simple phenomenological models that have few or no parameters to fit! I mean, we may only be able to describe what happens and no longer why and how something happens, but who really cares about details?
Along those lines, I propose a new model of the Sun. I propose that it is basically a hot object, so that it throws off blackbody radiation and looks bright. Also, it emits neutrinos. But since it is a descriptive model and doesn't delve into explanatory details like invoking hydrogen fusion, the CNO cycle, etc., it is immune to all the problems with the Standard Solar Model, like incorrect ratios of neutrinos. By inserting adhoc assertions like neutrinos oscillate (particles with mass? Get real!), the Standard Solar Model gets complicated. By not even addressing neutrino masses, my model doesn't require them to be massive (but it allows for that to be the case), so is much simpler. Therefore, by Occam's Razor, my model is better. I'll now be waiting by the phone for that call from Stockholm.
Seriously, you cannot discount a fundamental model in favor of a phenomenological model simply because it has parameters that must be fit. For all you know, the underlying theoretical model that is the basis for the phenomenological model will have ten times as many parameters to fit.
CS -- yeah, good point.
The truth is that even just a few years ago, the observation evidence on galaxies didn't really strongly favor dark matter or MOND. Most scientists preferred dark matter because it fit a lot of other things, and because until Beckenstein, MOND really was purely phenominological.
But, now, yeah, we know there is dark matter. Kinda cool how science can advance :)
Nice to see you back.
So the present thought is that the universe will expand forever as a consequence of flatness, with the "big crunch" idea out of date? (There was a "big crunch" theory at one time, wasn't there, or did I maybe just get that "end of the universe" stuff from watching too many episodes of Dr. Who?)
JuliaL -- yes, sort of. The high probability that the Universe will expand forever is in fact not a consequence of flatness, and isn't even linked to that any more.
Before 1998, most cosmology textbooks would draw the connection between geometry and fate. A closed (spatially finite) Universe would recollapse in a Big Crunch, a flat or open Universe would expand forever. However, the connection between these two requires the assumption of no cosmological constant (i.e. no dark energy). With dark energy, it's possible to have a closed Universe that will expand forever.
So, yes, we think that the Universe will expand forever, and there never will be a Big Crunch. But that's not a consequence of flatness, it's a consequence of dark energy. The supernova results themselves pointed towards an accelerating Universe that would expand forever, but didn't provide any constraints at all on open vs. flat vs. closed geometry. The flat geometry constraints were provided by the Cosmic Microwave Background— but at least the first measurements of flatness (from BOOMERANG AND MAXIMA) didn't provide strong constraints on expand forever vs. Big Crunch, at least if you took the possibility of dark energy int account.
What do you feel about the Arp associations?
For example, there is a physical connection between the barred spiral galaxy NGC 4319 and the quasar like object Markarian 205. This connection is between two objects that have vastly different redshift values.
Mike -- that's a whole 'nuther post. ;D One year I will hopefully get to it.
Dark matter is constructed as a hypothetical explanation to help the misinterpretation of the galaxies' rotation curve where the angular velocity is mixed up with the orbital speed.
Big bang is a misinterpretation of the fractional displacement of the radiation that is an entropy-effect which causes the energy to move towards equilibrium.
No dark matter is needed.
No dark energy is needed.
No Big Bang is needed.
Ingvar, Sweden
http://www.theuniphysics.info