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Martin Brown · 20-02-2009, 08:59 PM posted to uk.rec.gardening

wrote:
In article ,
Martin Brown wrote:

Standard candles that can be seen at great distances are pretty well
understood these days. And lots of amateurs keep regular watch.

Their standardness is all based on indirect evidence. For example,

It is kind of difficult to go out and examine these things directly.

We can only base our models on what can be observed from the Earth.
Until fairly recently it was possible to claim that "dark matter"
consisted of old biros, chair legs and sticks of rhubarb. This is now
ruled out by observational evidence.

Don't blame cosmologists for their inability to go out and do controlled
experiments. They are stuck with the problem of trying to work out how a
forest works by looking at the trees they can see.

You can gripe about theorists though. Some of the wilder ideas of string
theory and dark energy I find hard to take seriously.

cosmologists believe that the laws of physics settled down only
shortly after the big bang, so why are we assuming that all physical
constants are the same across all space and time since then?

Actually they don't entirely assume that.

Conjectures about what would happen if the "constants" of nature were
evolving are considered in some of the classic graduate textbooks.

We have damn-all direct evidence of general relativity at high space-
time stresses,
Actually we do have some pretty good examples in the millisecond pulsars
for instance. Shortly after the first discovery of a binary ms pulsar an
error was found in the FORTRAN converter of the early VSOP computer
algebra generated planetary ephemeris thanks to a systematic error in
the GR predicted delay observed when the signals passed near to Jupiter.
The spin down rate matches the GR predictions very nicely.

That is LOW space-time stresses, not enough to distinguish Einstein's
formula from several others.

It is pretty difficult to observe things any closer into the crunch
zone. The Blandford-Znajeck model for how radio galaxies are powered
still seems to look reasonable decades later. There are refinements.

there are alternative hypotheses that are mathematically consistent
and compatible with known physics. Yes, they're probably wrong, but
that doesn't prove the current hypotheses are right.
Indeed. But the evidence for a Big Bang cosmology is pretty compelling.
There are very few die hard Steady Staters remaining these days.

Why assume that is the only alternative? There are several variants
of the big bang that would enable wildly different ages for the
universe.

Not that wildly different.
Nothing approaching the 6000 years that the dittoheads in Merkinland
tend to want (matching Bishop Ushers guestimate).

This will be my last post on this topic! Anyone who wants me to respond
further should send Email.

I'd suggest taking it to sci.astro but the place is populated with
complete nutters of the Einstein "WAS WRONG" camp.

It might be easier to continue it here with [OT] in the headers.

Regards,
Martin Brown