Science Forums 2

[PhysBang]

Originally Posted by coldcreation

Careful, your use of words is borderline ad hom. Attack the subject, not the person.

Yes, what you wrote is delusional.

You sound surprised...The origin of the quote is Scientific American.

I'm not surprised. Scientific American is often a good resource for bad physics.

The fact is, an accelerated expansion was not predicted by the standard model (which was based on the FLRW metric, the three Friedmann models).

OK, there is no FLRW metric.

There is the Robertson-Walker metric.

This is used in the Friedmann models. And it is used in the Lemaitre models. (The "F" and the "L".)

The Lemaitre models have accelerated expansion. They were developed in the 1920s and studied since then.

If the measurement of the value of lambda was pending then all possibilities should have been considered seriously as potentially operational.

Some scientists did seriously consider the possibility. The current value for the cosmological constant is very, very low compared to what it could be, so it was not measured in many tests. That it wasn't measured in so many tests (being below the threshold of measurement) could be the reason many scientists though that it was zero.

It is rather pure fantasy that 96% of the mass-energy density is thought to be "dark" stuff.

Fantasy that is actually measured in many different ways, yes.

Theories make predictions. When those predictions turn out to be erroneous, the theory is either modified or abandoned. In this case the theory (the old pre-1998 standard model) was modified (lambda-CDM). My contention (opinion) is that is should have been discarded unilaterally.

You are welcome to your opinion. I'm sure you would rather have an ad hoc explanation that doesn't fit the facts.

Neither Lemaître nor his disciples predicted an accelerated expansion.

What are your readers supposed to do when you simply outright lie? You write this crap like the only way to do science is to come up with any crazy idea as long as it has nothing to do with any measurement and then wait until there is a lucky observation. Cosmologists came up with a framework of actually measuring the properties of the universe and then actually measured these properties.

The idea was just too kooky. Why, because something outside of physics (dark energy and nonbaryonic dark matter, in profuse quantities) would be required to justify the otherwise linear regime.

WTF is a "linear regime"? The universe may simply be more than you can imagine and comprehend.

The favored possibility described a universe in which omega is precisely equal to one, the critical density, with a one-to-one relation between the density of the cosmos and its spatial curvature, i.e., this model was a flat, Euclidean (with zero curvature). The velocity of expansion tends to zero as its radius approaches infinity.


That prediction obviously failed.

This was a favoured result, but not one that was predicted. Cosmologists were committed to measuring, not dictating.

But then again, there were two other possibilities (on the back burner just in case): one with a closed spherical geometry; it expands and collapses to infinite density in a finite time. There is enough gravitating mass to halt the expansion and reverse it, leading to a big crunch.

And finally, one with a hyperbolic geometry that expands for ever, tending to infinity with a finite velocity. The galaxies are undecelerated as there is not enough gravitating mass to stop expansion or to slow it down.


The new findings reflect none of the above.

Not just matched none of the above, but showed systematic results that provided a measurement of cosmological parameters.

True, and prediction were made. It would have been sweet had predictions coincided with what is observed in nature.

That is the scientific method...

The predictions made were how to make cosmological measurements. One could also consider the measurements made by one technique to be a prediction. Then one can look at the measurements made by another technique as another prediction.

I would be interested to find out just what issue of Scientific American that original quote came from, since it is not the one that modest posted.