(17) It was the
1931 paper of Edwin Hubble
& Milton Humason that established the velocity-distance relation of galaxies
beyond reasonable doubt, not Hubble's 1929 paper (which had really rough data!). It is certain that Georges Lemaitre should also share the credit for discovering the expanding universe. See this paper:
http://arxiv.org/ftp/arxiv/papers/1108/1108.0709.pdf
and this thread:
http://www.iceinspace.com.au/forum/s...d.php?t=109083
(18) Otto Hahn won the Nobel for the discovery, but Lise Meitner never received a Nobel Prize for her essential role in this work!
(19) J. Robert Oppenheimer's 1939 paper (J.R.Oppenheimer & H.Snyder, 1939, Phys.Rev,
56, 455) predicted that a
hyper-dense object with sufficient gravity to stop all light escaping from it can be formed by the contraction of a sufficiently massive star at the end of its life. This work is considered one of the most important advances in relativistic astrophysics. (A few months earlier, Oppenheimer & Volkoff had published calculations of the conditions under which a neutron star could remain stable under its own gravity, finding that it would be unstable (no static solutions and no equilibrium) above a certain critical value of its total mass!). Oppenheimer & Snyder showed that if a star's gravitationally collapsing core has sufficient mass, then even neutron pressure is still insufficient to prevent its further contraction to a black hole, and that even a neutron star would continue to shrink inexorably towards an eventual fate as a possibly point-like object. To quote from their paper : ".....this contraction will continue indefinitely."(!) . And I further quote: "The star tends to close itself off from any communication with a distant observer; only its gravitational field persists." [ A history of 1930s research on the stability (equilibrium) of neutron stars & ordinary stars, and on the conditions necessary for gravitational collapse, can be found in: "The Attraction of Gravitation"(1993) ed. Earman & Janssen & Norton, part of which is available in GoogleBooks. ]
(20) It is remarkable that before the 1950s, biochemists were unable to figure out the structures of large biomolecules like proteins.
(21) Francis Crick and James Watson, who figured out the correct structure, were entirely reliant on the X-ray crystallography data of Rosalind Franklin.
(22) Pulsars were discovered in 1967 (published in 1968) by Jocelyn Bell Burnell, a PhD student at the time. Unfortunately, her
supervisor won the Nobel Prize for
her discovery! It took a lot of work for her and the said supervisor to prove that the rapid and evenly-spaced radio pulses that they had detected with their radiotelescope did not actually come from a glitch in the electronics or from radio interference, and the extreme regularity of the pulses even had people thinking that some 'Little Green Men' might have produced them. Bell Burnell was a brilliant observer; but - in my opinion - a more significant advance was actually Thomas Gold's publication in 1968 and 1969 of his theory that a pulsar is a very rapidly spinning neutron star with an extremely strong magnetic field, an idea that is still accepted and which is still consistent with all existing observations.
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23) Successive and ever-deeper imaging surveys of the sky, showing the distribution of galaxies over the face of the
apparent sky (that is, as seen from Earth), had shown that the galaxies seem to be distributed very unevenly; the distribution of luminous matter is not isotropic. The strong clumping of galaxy redshifts, in most lines-of-sight, was another early indicator that galaxies are not evenly distributed in space, that the universe contains many strong overdensities and underdensities of galaxies. Maps of the sky distribution of galaxies have not provided evidence for the homogeneity ("evenness") in the space distribution of galaxies and matter that had been predicted by the cosmologists! For instance, the two-dimensional distribution of the galaxies in Fritz Zwicky's CGCG (1961-1966), when plotted on a sky map, showed clusters and superclusters of galaxies, with the galaxies arrayed in a bubbly & foamlike structure that included "holes" where there seemed to be few galaxies . However, the nature of the actual
three-dimensional distribution of galaxies in space, at the very largest scales, remained poorly known even in the mid-1970s , though clusters of galaxies were already known, as was the tendency of several galaxy clusters to group together into a
supercluster. Fortunately for astronomers, instrumental advances beginning at the end of the 1970s gradually allowed ever-increasing numbers of galaxy spectra to be obtained, and therefore the making of distance estimates for ever larger numbers of galaxies, thereby allowing three-dimensional maps to be made of how the galaxies are distributed in the universe; in particular, the CfA1 and CfA2 redshift surveys were perhaps the first major advance in
accurately mapping the space distribution of luminous matter at the very largest scales. Since then, there have been many surveys deriving large numbers of galaxy redshifts (galaxy distances), thus probing the space distribution of the galaxies out to
ever larger distances and on ever larger scales, with the fundamental finding of an overall bubble-like and foamy structure that has
walls and shells and filaments of multiple galaxies surrounding giant
voids which contain very few galaxies. Searches for galaxies in voids have made it very likely that the space density of galaxies in voids really is unusually low, and the universe is now known to contain coherent structures as much as
1.4 billion light years long (e.g. the Sloan Great Wall). As ever more surveys have been made to map the distribution of galaxies, and as the total survey volume has progressively increased, progressively larger structures have been found....... yet cosmologists still seem wedded to the idea of an isotropic and homogeneous universe!
Here is an excellent review of the Large-Scale Structures in the cosmological context:
http://www.sns.ias.edu/pitp2/2011files/nature04805.pdf
(24) Others had also posited that the eukaryotic cell is a composite organism which had its origin in two or more free-living cells, but Lynn Margulis, over several decades, gradually collected a weight of evidence that eventually ended up convincing most biologists. The evidence is now strong that the mitochondria & chloroplasts inside eukaryotic cells are the descendents of free-living bacteria that became incorporated into a larger cell.
(25) Two teams, the Supernova Cosmology Project and the High-redshift Supernova Search Team, observed distant Type Ia supernovae and thereby established that the actual expansion law of the universe is not compatible with previously favoured models of cosmology. (observations of Type Ia supernovae, together with their known luminosities, are commonly used to make credible distance estimates for very distant galaxies). According to professional cosmologists (who are never in doubt, but often wrong......), this work showed that the expansion of the universe is actually accelerating, due to some unknown cause. The poorly-known substance or phenomenon or energy which is responsible for the acceleration of the universe is often called
dark energy , or, more accurately,
cosmic antipressure. A really clear explanation of all this can be found here:
http://www.slac.stanford.edu/econf/C...perlmutter.pdf
(26) The
apparently sudden appearance of many of the basic
body plans (=
phyla) of animals in the fossil record , was already appreciated by Charles Darwin, who lamented that the
apparently explosive nature of the event was hard to fit in with his theory of gradual biological evolution. However, the serious study of the nature of the so-called "Cambrian explosion" occurred in the 20th century, prompted by the collection of ever more Cambrian & Precambrian fossils, with the
extremely rare fossils of soft-bodied animals being key data points in the ongoing arguments. The time frame of this evolutionary radiation, the nature of the soft-bodied antecedents of the Cambrian organisms in the fossil record, and the question of exactly which phyla are represented in the Cambrian rocks, are all subjects of ongoing debate What can be said for sure is that easily fossilizable multicellular animals (that is, those with hard parts) first appeared in the Cambrian Period.
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