Expert: Philip Stahl - 8/30/2005

Question
Philip:

Has modern science proven beyond a reasonable doubt the ages of the Universe and Earth? How about the Big Bang? What is this proof exactly?

Have a friend who claims science has never proven the ages of the Universe/Earth, nor has it proven the Big Bang. He claims that the age of the earth is NO MORE than 10,000 years old. How do I answer such a claim?

Thanks.

Art Granville
Hemet, CA

Answer
Hello.

First, before addressing your specific questions, let's consider what "proof" means and if applicable to the scientific process.

Most of us who've done any scientific research - as published in peer-reviewed papers, realize it is quite impossible to "prove" a particular claim or unique solution to a scientific problem (that is, true for all times and conditions).  Solutions of scientific problems are instead assessed for adequacy, that is, in respect to the extent to which the researcher's stated aims have been carried out.

Two categories of criteria are those related to argument and to the evidence presented.  To judge adequacy then, we look for the strength and consistency of logical/mathematical arguments (preferably within self-consistent models), and the goodness of fit of the data in a given context.  By "goodness of fit" I mean that two different datasets on comparison are either strongly correlated or anti-correlated.  As an example, the rate of growth of tree rings is strongly correlated to the level of activity of a particular sunspot cycle.  There is agreement and an excellent "goodness of fit".

We also look for these to be confirmed in future investigations, and repeatedly over time. All such determinations of adequacy perform the same function for scientific research that quality control does for industry.  Most importantly, no determination of adequacy can be rendered until and unless the research is published in a refereed journal, by professionally qualified peers.


In the above context, we have ample criteria (especially radioactive isotope dating, say using Potassium-40) to show the Earth is at least 4 billion years old. We also have a means to compute the Hubble constant H, from red shift data (see below, for details) to ascertain the age of the universe. Right now, that stands at about 13.5 billion years. (I prefer not to go into the detailed mathematics of the caculation unless you specifically ask for it in a reply)

The Big Bang theory has also met all the above criteria, and even more.  The 'Big Bang' (with cosmic inflation factored in) is now accepted as fact, or as close to a firm fact as conceivable - in a setting of changing scientific
discoveries.

The 2.7 k background radiation, the same in all directions,
is one of the firmest evidentiary bases - since only a symmetric explosion (in space *and* time) would produce such an obsevation (recorded by Arno Penzias and Robert Wilson at Bell Labs in 1965, for which they won the Nobel Prize in Physics. They'd not have been honored by serious scientists in this way if their findings were so much baloney or bunkum)

In addition, there is the red shift we observe in the spectra of distant objects (outside our galaxy). That is, all the key spectral lines - one for each chemical element- are uniformly shifted to the red or long wavelength end of the electromagnetic spectrum. When the displacement is computed and related to the velocity of the object (moving away) it is always huge.

This is why we refer to it as a "cosmological red shift".

This is only explainable by an expansion model, since the expansion itself has no defined locus. Think of raisins expanding on a loaf of bread pudding, or ink dots on an inflating balloon. No single raisin (or dot) enjoys a privileged position of "center" to the particular expansion. All expand outward in relation to every other.

Thus,  such expansion would naturally have arisen from a primeval explosion.

The 1992 discovery of "relic structures" - by the COBE (Cosmic Background Explorer) craft further reinforced the findings and acceptance of the model.

Now, to get into the exact and specific data and arguments that support the Big Bang, I suggest two excellent books - which you or your friend ought to be able to find at a library. I prefer to give you these, to do justice to the nature of the arguments and details that might otherwise be omitted in a reply like this.

The first book, written at a totally popular level is:

'The Big Bang Theory - What It is, Where It Came From, And Why It Works', by Karen C. Fox, John Wiley & Sons, 2002.


The second book, a tad dated but still excellent - especially in terms of showing how and why the Big Bang is the only theory based on the isotropic background radiation, is:

'The First Three Minutes', by Stephen Weinberg, 1977.

The Appendix of his book is particularly useful, and requires no more than High school algebra to get through. He shows exactly from the mathematics how the Big Bang explains the 2.7 K background radiation.

Again, in referring any of this to your friend, try to move away from the concept of "proof" (which is really only applicable in abstract mathematics) to that of meeting scientific QA tests for adequacy - for a given stated theory.

Re: the "10,000 yrs." age of Earth claim - that is dismissable on its face since we can use radioactive dating methods to show various rocks (such as from Earth and Moon) are at least 2-3 billion years old. Also, in a relatively recent use of the Carbon -12 isotope, 'delta C 13', evidence for the existence of life on Earth has been found to date back 3.85 billion years. (See: 'Evidence for Life on Earth More than 3,850 Million Years Ago', in Science, Vol. 275, 3 January, 1997, p. 38, by H.D. Holland)

The age of the universe can clearly be discerned as very large, once we know the velocity of light is 300,000 kilometers/ sec (or 186,000 miles per second) and can find the distance to a celestial object.

Thus, if we find the (red shift) expansion velocity of the quasar 3C 273 to be 48,000 km/sec (or 16% of the speed of light) we can make use of the Hubble expansion law to find the corresponding distance:

E.g.

d =   (v/ c) 1/H

where v = 48,000 km/sec, c = 300,000 km/sec and H is the Hubble constant,  H = 71.5 km/s/Mpc (all units made consistent in the eqn. - which details I omit here):

d =  2.19 x 10^9 light years or 2.19 billion light years.

Now, this distance means that the light from the object has taken 2.19 billion years to reach us. This means that the universe (based on this object's distance alone) is *at least* 2+ billion years old - since you cannot possibly have a distance for light to travel that exceeds the age of the universe!

Hopefully, this material will prove useful, but I especially emphasize getting hold of the 2 books I referenced above. If one is going to do justice to the Big Bang, in terms of demonstrating its validity (to oneself or one's friend) the optimal approach is to go to sources dedicated to such answers - as opposed to an 'answer' board or forum such as this. Then, the exhaustive answers are available and in the required detail -  as opposed to "reinventing the wheel" here.