Re: heating and expanding

Anders Sandberg (
31 Mar 1999 12:30:24 +0200

Julian Leviston <> writes:

> True that I don't know what I'm talking about when it comes to things that
> aren't heat-expansion related in terms of expansion.
> I'm only talking from my own practical experience, as that's the only thing
> that I know is true. Most of the ideas that are in current science courses
> are based on theory. Theory in my definition of the word is unverified ideas.

You may define theory to mean anything, but don't expect anybody to take you seriously if you use words in ways others don't ("Could I have some democracy and chairs on my sandwich?"). Scientific theories, as the term is commonly used, are not unverified ideas but rather models that have been tested against reality and found to work better than the alternatives.

> I don't understand how scientists have arrived at the fact that the
> universe is expanding if not simply from theory.

I would suggest that you really do take a look at some books or at least websites about cosmology. They can be quite fun.

The quick answer is that the expansion is mainly supported by the redhsift of light from distant galaxies. As something receedes from us it reddens (due to the Doppler effect). The more distant (as measured by other means such as cepheid variables etc), the more redshift.

There are also consistency with other physical theories and models, such as general relativity (where most cosmologically relevant spacetimes either expand or contract), the big bang theory (in turn supported by a variety of observations), models of stellar and galaxy formation and so on.

Scientific theories form a self-supporting framework, where the success of theories depend not just on how well they explain known facts but also how well they fit with all other theories. Inconsistencies tend to invite intense research (e.g. the age of earth controversy at the turn of the century where physics and biology came to different answers, or the current attempts to unify general relativity and quantum mechanics), and ideally theories should be subjected to continous testing and challenging.

> And theory is guessing. I'd rather not accept guessings.

Exactly. But rational thinking involves setting up hypothesises, testing them against reality, modifying them as needed (sometimes by throwing them out and starting all over again). The end result is a theory, not guesswork.

> If you're going to look at new ways of doing things, you can't think in a
> mode of thought common to the old. It requires a complete, quick, snap
> turnaround. You can't keep the old if you want the new.

Newton and Gallileo overthrew the Aristotelian physics, but they didn't throw it out, they just showed that it was a (bad) approximation to what happened. Einstein did the same, showing that Newtonian physics is a good approximation as long as masses are small and not moving near the speed of light. Science advances not by throwing away everything that has been gained but by finding even better ways of explaining it.

Throwing out everything old means we don't learn anything from it.

Anders Sandberg                                      Towards Ascension!                  
GCS/M/S/O d++ -p+ c++++ !l u+ e++ m++ s+/+ n--- h+/* f+ g+ w++ t+ r+ !y