“SQM also suggests the possibility that past steps along our evolutionary ancestry may be so rare, that they have occurred no where else in the past history of the universe that we can observe”.

It is almost certain that life in the universe is a common phenomenon. It is also almost impossible that beings identical to ourselves exist anywhere else. One does not have to be a quantum theorist to fathom that! However it is interesting that certain quantum theories point to such an obvious conclusion about our uniqueness in the universe.

For similar reasons, related to genetic inheritance and environmental upbringing, each human individual who has ever lived is also unique. Cloning people doesn’t produce robots, just individuals with identical genetic inheritance- as identical twins. However, no pair of identical twins live exactly identical lives.

This comment in Don’s abstract has profound implications…

If anybody is into non-verbals, look at the expressions on Albert and Edwins faces!

A picture is truly worth 1,000 words!

I realize the picture was posed…for all we know it was taken in the daytime.

As for hard spheres in the contracting universe: the point is, not how they affect the forces, but they are an obstruction - I don’t think they could be just pulverized as if nothing there. There are contradiction problems if you try to imagine what happens to all the bodies in expanding/contracting universes if some things are impeded by material barriers/obstructions and other things just move like dust in free fall.

Garth: H_o*t_o is not equal to 1 with an accuracy of 0.6%.
t_o is known (but model dependent) to 1% and H_o (also
model dependent) to 4%. So while the product is very close to 1, the propagated uncertainy is 4%.

Yes Ned, although my post #22 was submitted before it was properly prepared (I have you Preview button on this Forum), I was simply using your Cosmology Calculator http://www.astro.ucla.edu/~wright/CosmoCalc.html,.

The present best accepted values of cosmological parameters
(using the table in WMAP Cosmological Parameters http://lambda.gsfc.nasa.gov/product/map/dr2/params/lcdm_all.cfm)
Ho = 70.4 km/sec/Mpsc
Omega_Lambda = 0.732
Omega_matter = 0.268

Feeding these values into your calculator I obtain:
The age of the universe is = 13.81 Gyrs.
But with h_100 = 0.704,
Hubble Time = 13.89 Gyrs. i.e. 0.6% difference!

In other words the calculated age turns out to be equal to Hubble Time to within the limits of the observational error of 4%.

Is this just a coincidence or is the universe trying to tell us something?

Garth

The discovery of the Hubble expansion was indeed a profound advance. But there’s even more to it than that, as you well know, so let me point out for your readers:

1. The pattern of Hubble’s law, that the recessional velocity of distant galaxies is proportional to their distance away, directly implies that contemporary observers on any galaxy will see the same pattern, and with the same proportionality. Thus the Hubble law contains the idea that the expansion has no preferred center.

2. If we extrapolate the Hubble-law motions of the galaxies backward, assuming no acceleration (a not entirely unreasonable thing to do), we discover that there was a singular moment at a finite time into the past when they were all on top of each other. So Hubble’s law also raises directly the idea of a Universe with finite age.

Hubble could/would have declared an expanding Universe based on any observation of velocity going up monotonically with distance. It is the special linear result v=Hd that also leads to the also profound picture of a uniform expansion with a finite history. It all came in the same package! as long ago as 1930, for which we can indeed be thankful.

Cheers,

Paul

Garth: H_o*t_o is not equal to 1 with an accuracy of 0.6%.
t_o is known (but model dependent) to 1% and H_o (also
model dependent) to 4%. So while the product is very close to 1, the propagated uncertainy is 4%.

Sean: I read Luminet’s review (pointed out by Daniel Fischer)
and it makes the point that Le Maitre’s little cited 1927 paper
in French to the Belgian Academy actually did the data analysis
and derived the Hubble constant two years before Hubble. Then
Luminet didn’t list this paper in his reference list! I wish
this 1927 paper were in the ADS, but last time I checked only
the translation in the 1931 MNRAS was there.

I did a few quick calculations using the measured angular diameter of the Moon and Sun in the sky at the apogee and perogee of appropriate orbits, and a guestimate of a rate of withdrawl of the moon from the Earth of 4 CM per year, and came up with numbers indicating it would take a full billion years for total solar eclipses to be eliminated. It seemed to me like an unbelievably long period of time for this trivial cosmic coincidence to be eliminated.

I checked with NASA and they told me that taking the increase in the size of the Suns disc into consideration and using a correct 3 CM annual withdrawl rate for the Moon, it would take a bit less than 600,000.000 years for total solar eclipses to be eliminated….a pretty stable coincidence indeed.

This has been discussed elsewhere:
http://arxiv.org/abs/astro-ph/0604011

One might want to do to read the stuff before the abstract though, … the paper did not quite manage to achieve what they had set out to do.

Yes that paper was a hoot! Notice the date and the co-author Ali Frolop = April Fool!

Garth

I’m not at all convinced, especially since we now know that the universal expansion is accelerating, that this Hubble relationship really is linear, considering our limits of accuracy in measurement. Time dilation function is a pretty straight line until we are pretty close to the speed of light.

We are dealing with relativistic relationships when are talking this distant aspect of astronomy. The simple linear relationship which Hubble proposed may not be quite so simple- or linear 13BLY out.

Today’s cosmology, is often a form of mental masturbation.

But if cosmic expansion keeps accelerating, so that the cosmological horizon shrinks, is there likely to be any change in the character of cosmic expansion if/when the cosmological horizon falls below 13 billion years so that the Big Bang is no longer “visible”?

One might want to do to read the stuff before the abstract though, … the paper did not quite manage to achieve what they had set out to do.

Why should these be approximately equal?

The two coincidences are linked because it is the mix of DE/Matter that determines the age of the universe in terms of Hubble’s constant.

Garth

If the universe is flat with a total density parameter Omega = 1 then:

if there is no DE then the Age = 2/3 Hubble Time

if there is DE that reduces the rate of then
the Age > 2/3 Hubble Time, from that value up to infinity, depending on the amount and the exact equation of state of the DE.

Garth

Here’s a nice picture of the Hubble redshift from calcium lines.