Expert: Philip A. Stahl - 12/3/2006

Question
Is not the Big Bank Theory more applicable on a galactic scale than a universe wide scale?

Answer
Hello,

No - if the Big Bang is applicable to anything, it is the cosmos as a whole.

First, The 2.7 k microwave background radiation, the same in all directions- discovered by Arno
Penzias and Robert Wilson at Bell Labs in 1965-
is one of the firmest evidentiary bases for a universal phenomenon. It is so because it represents the minimal temperature to which the original, primeval fireball has cooled.

Moreover, since it is *isotropic* - meaning the same in all directions - it shows that it is not a special feature of one part of space-time or the universe, but ALL of it.


This is understandable, since only a symmetric explosion
(in space *and* time) would produce such an observation as made by Penzias and Wilson radio telescope. Moreoever, hey'd not have been honored by serious scientists with Nobel Prizes, if their findings were merely applicable at a "glactic level".

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.

The fact that this only uniformly applies to galaxy *clusters* beyond our own, shows in no uncertain terms that the Big Bang -generated expansion is a cosmic wide phenomenon, not merely "galactic".

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

This is only explainable by a universal expansion model, since the expansion itself has no defined locus. (E.g. cosmic "center" to which it may be traced in origin).

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. This is analogous to what we actually observe with external galaxy clusters.

To conclude, there is NO evidence the expansion from the Big Bang is a purely localized or galactic phenomenon. There is plenty of consistent evidence that the universe-wide cosmic expansion originated from it tens of billions of years ago.