Abstract
The eye, human or otherwise, is one of the most wonderful creations of nature. Through the steady searching of accumulated adaptation, working through the random shuffle of mutation, and the rigid testing of natural selection, evolution has found that special sweet spot of design that has enabled life to see.
Certain it is, that although our conclusions may be incorrect,
Our judgment erroneous, the laws of nature and the signs afforded
To man are invariably true. Accurate interpretation is the real deficiency.
—Rear Admiral Fitz Roy, The Weather Book (1863)
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- 1.
Although called rays, this phenomenon is actually related to a flow of charged particles.
- 2.
The law of refraction has actually been derived independently many times throughout history. Before Snellius, the same basic relationship had been discussed by Thomas Harriot in 1602, and the geometry of the situation was outlined by Arabic scholar Ibn Sahi in 984. After Snellius, René Descartes famously re-derived the result in 1637.
- 3.
Ludwig Boltzmann provided a derivation of Stefan’s empirical results, on theoretical grounds, in 1884.
- 4.
Since stars are not perfect blackbody radiators astronomers don’t actually use Wien’s law to determine temperatures. Rather the characteristics of a star’s absorption lines are analyzed to deduce an effective temperature. The effective temperature is the temperature of a blackbody radiator having the same total energy flux as the star being observed.
- 5.
Certainly early telescope optics suffered greatly from the poor quality of glass available at the time, and it is evident from his drawings of the Moon, as presented in Sidereus Nunceus, that Galileo was seeing fictitious features.
- 6.
This is according to Wien’s law, which gives λ max ≈ 3 × 10−3/106 = 3 × 10−9 m, placing it in the soft-X-ray region of the electromagnetic spectrum (Fig. 2.3).
- 7.
The first great experiment relating to gravitational lensing, of course, was that conducted by Frank Dyson (Astronomer Royal), Arthur Eddington, and Charles Davidson during the May 29, 1919, solar eclipse, the lensing effect of the Sun then being used to verify Einstein’s newly published theory of general relativity.
- 8.
There is absolutely no hubris in this statement, and humanity can be deservedly arrogant and boastful about such incredible technological achievements.
- 9.
The paper was actually based on a talk delivered at the August 1955 meeting of the International Astronomical Union in Dublin, Ireland.
- 10.
There has been a sad trend in modern astronomy and physics textbooks to ignore the names of J. D. H Pilkington, P. F Scott, and R. A. Collins when discussing the discovery of the first pulsar. They were an integral part of the research team, and should accordingly be recognized for their role in the discovery [8].
- 11.
It is staggering to think about this incredible object (and its kin). PSRB1919 + 21 has a mass about 1.4 times larger than that of our Sun, a radius that is over 71,000 times smaller (r ~ 10 km) than our Sun, and it spins on its axis 4 times every 3 s. That such objects exist in nature is truly incredible!
- 12.
This in fact is no easy task. A few pulsars have known parallax distances (recall Fig. 1.14), but most have to be estimated by secondary association. Since neutron stars are products of supernova disruption, so the distance to a pulsar can be estimated by determining the distance to its associated supernova remnant (see Fig. 1.12).
- 13.
This is the same Taylor in the Hulse and Taylor binary pulsar that enabled the first verification of Einstein’s prediction concerning gravitational waves. Russell Hulse and Taylor were awarded the 1993 Nobel Prize for Physics for their discovery of PSR1913 + 16 (recall Fig. 2.16).
References
Interested readers will find more details on Maxwell’s ideas and the properties of electromagnetic radiation in the author’s book, The Physics of Invisibility (Springer, New York, 2012).
The spectral classification scheme was developed over several decades encompassing the turn of the 19th century. Literally hundreds of thousands of stellar spectra were recorded photographically, and numerous teams of technicians and astronomers sorted through the data looking to tease out an order sequence. Spectra were ordered in terms of line strengths (literally the area of a spectral line) and line strength ratios, and these in turn were interpreted in terms of a temperature sequence. Stars are now classified according three parameters: a spectral type, a sub-group number, and a luminosity class. There are seven principle spectral types, represented by the letters O, B, A, F, G, K and M, with the O stars being the hottest and the M stars the coolest. The sub-group number ranges from 0 to 9, with 0 representing the lowest temperature within the type and 9 the highest temperature. The luminosity class is given as a Roman numeral between I and V. Luminosity class I applies to the supergiants, which are the largest and most luminous stars; luminosity classes II, III and IV are the intermediate giant stars, while luminosity class V corresponds to the lowest luminosity dwarf stars. By this scheme, the Sun is a G2 V star. See table A1 in Appendix I for further details.
Interested readers will find more details on the experiments and development of theoretical ideas concerning atomic structure in the author’s book, The Large Hadron Collider – Unraveling the Mysteries of Universe (Springer, New York, 2010).
The energy associated with each orbital in the Bohr model of the hydrogen atom has a particularly straightforward expression, being E(n) = − R H / n 2, where R H is the Rydberg constant of 13.605 eV (see caption to figure 2.8 for a definition of the electron volt). Accordingly the energy difference between two electron orbitals having principle quantum numbers n and m (with m > n) is ΔE = E(m) – E(n) = R H (1/n 2 - 1/m 2). It is the amount of energy ΔE that an electron has to either absorb (to enable a transition from n to m), or emit (to enable a transition from m to n).
Specifically, the UV photons set up a high temperature, T ~ 104 K, ionization front that heats the outer layers of the disk, and as a consequence of this the sound speed c S ~ (T / ρ)½, where ρ is the density, associated with the disk gas is increased to about 10 km/s. For a central protostar of mass M, the radius R esc beyond which the sound speed exceeds the system escape velocity V esc is R esc = 2 G M / (c S)2, where G is the universal gravitational constant. The radius at which V esc = c S = 10 km/s for a 1 solar mass star is about 18 astronomical units. Accordingly, for radii R > R esc the gas is able to escape from the disk in the form of a thermal wind. Observations indicate that in the Orion Nebula the thermal wind can drive a disk mass loss rate of M wind = 10−7 M⨀/yr, and given a typical disk mass M disk = 0.01 M⨀, the disk lifetime is limited to t disk ~ M disk/M wind ~ 105 years.
The current grail-quest in the field of particle physics is that of finding the carrier of dark matter. That such matter, which neither absorbs nor interacts with electromagnetic radiation but has a very definite gravitational influence, exists is beyond question. What is not known yet is what kind of particle (or particles) is involved. Additionally, it is not known where the dark matter particles fit within the present plethora of possibilities offered by the beyond-the-standard models of particle physics. Interested readers will find more details on the past and present experiments relating to dark matter detection in the author’s book, The Large Hadron Collider – Unraveling the Mysteries of Universe (Springer, New York, 2010).
The Local Group of galaxies is composed of about 50 galaxies spread over a region several millions of parsecs in extent. The Milky Way and the Andromeda galaxy are the most massive members of the group and they, along with their many satellite galaxies, are located towards the system center. The Local Group is part of the much more extensive Virgo Supercluster.
There has additionally been a ridiculous amount of bluster written about the supposed denial of a Nobel Prize to Jocelyn Bell because she was a mere graduate student and/or a woman. Neither charge is remotely true. The Nobel Prize for Physics was awarded to Antony Hewish and Martin Ryle in 1974 for, “their pioneering research in radioastrophysics”. The award was not made for the specific discovery of pulsars.
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Beech, M. (2017). In the Eye of the Beholder. In: The Pillars of Creation. Springer Praxis Books(). Springer, Cham. https://doi.org/10.1007/978-3-319-48775-5_2
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