So far, we’ve examined the subject of “Time” as viewed through Scripture and Creation. The two previous blogs considered “Time” as expressed in God’s Creation through physics and earth science. This last blog will extend the discussion through astronomy.
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If you happen to be in Pasadena (CA) or the surrounding area, look at the top of the large mountain peak just north of the city. In most locations, a white telescope observatory stands majestically on the ridgeline—as a bold sentinel in the annals of science. This is the Mt. Wilson Observatory, home of the Hooker telescope.
I had the privilege of visiting and touring the observatory with friends in October, 2011 (Figures 1-3). It seemed we were standing on astronomy’s sacred ground. Some of the greatest discoveries of the 20th century were made within those curved walls and domed ceiling by a young astronomer named Edwin Hubble. We’ll examine a couple of his breakthroughs in Part 2 of this blog; but first, we need the necessary foundation. Several earlier discoveries influenced Hubble, and these provide context for our discussion of “time” as viewed through the lens of astronomy. I’ll summarize these discoveries in the following sections.
The Speed of Light
If you were able to place a large heavy curtain in front of the sun, block the sun’s view from earth, and suddenly remove the curtain, it would take 8.3 minutes before the light could reach Earth. It would require 4.1 hours for the light to travel to the planet Neptune. Light is not the instantaneous entity it seems when you flip on the switch in a darkened room.
How Fast is Light?
With today’s sensitive measurements, we know that light travels at the astonishing velocity of 186,292 miles/second. But perhaps even more amazing, the speed of light was calculated in 1727 by James Bradley1 at 183,000 miles/second (98.3% accuracy) using strictly astronomical observations (light aberration2).
The speed of light is a fundamental parameter in many equations, including Einstein’s Theory of Special Relativity (includes E=mC2; where C = speed of light). It bridges the relationship between space and time. If we know how long it takes the light from a distant star to reach earth, we know the distance to that star. Both are measured in “light years.” And, like pure mass and pure energy, we cannot grasp the vast distances traversed by light as it spans our universe.
Diminishing Luminosity
As an experiment, if I placed a strong LED flashlight directly in line with your eyes, six inches away, and turned on the light, it would be blinding. If I repeated the experiment but placed the light 100 yards away, you could easily look into the beam. And even if you used binoculars to magnify the flashlight to the same size as it appeared when six inches away, it would still be easily viewable. Why?
Think of light as the rings on a pond once you pitch a rock into the water. As the rings move outward, they diminish in size. Energy disperses with distance traveled. This physical relationship also applies to a light source, whether a beacon on earth or distance measurements to an isolated star.
Distance and Diminished Luminosity
Distance is calculated from diminished luminosity with the following simplified equation:
Distance = √(Absolute Mag/Observed Mag)
The “Absolute-” and “Observed Mag” are measures of the absolute- and observed luminosities of the source, respectively. More advanced equations are applied to distance calculations for stars3.
The absolute luminosity of a star (its true brightness) is estimated from the star’s classification, and its distance is calculated from the reduced luminosity measured on earth. This relationship is used for distances up to 25,000 light years from earth. Intervening dust, however, can dim the light; and estimates of the star’s absolute magnitude can introduce errors in the calculations.
Cepheid Variables
Henrietta Leavitt4 (Figure 4) was gifted with an amazing ability to focus on details. She received a Bachelor’s degree in 1892 and studied a broad curriculum of art and science courses, including astronomy, at Harvard. She was hired in 1903 by Harvard astronomer Edward Pickering to catalog and study stars that fluctuated in brightness (termed “variable stars”). She identified 1777 variable stars and published her results in 1908.
Henrietta had no computer or other modern instrumentation, but out of the 1777 variable stars she noticed 25 stars that pulsated on regular periods, and those with the shortest periods were extremely bright. These pulsing stars are termed “Cepheid Variables,” and their pulsing brightness was her breakthrough.5
Cepheid Variable Stars
A Cepheid Variable star is approaching death. Hydrogen fusion powers most stars. Helium fusion begins to dominate as old stars consume their hydrogen. Cepheid Variables are believed to use helium fusion, which is less energetic than hydrogen.
A complex relationship exists between gravitational collapse of the star, and its re-expansion as the internal temperature and pressure increase. Its luminosity increases dramatically as the star quickly expands—even more so if it cycles rapidly—exceeding that of our sun by approximately 10,000 times.
Leavitt eventually quantified a relationship between the Cepheid stars’ brightness (absolute luminosities) and the length of their periods (Figures 5a and b). This important relationship extended distance calculations to stars and galaxies that are millions of light years from earth. An astronomer only needs the period of days in a Cepheid star’s cycle to know it’s absolute magnitude, regardless of the distance. And with accurate absolute magnitudes, the diminishing luminosity equation can be applied (see above) with much greater accuracy.
Redshift
Vesto Slipher spent his entire career (1910-1952) as an astronomer at Lowell Observatory in Flagstaff (AZ; Figure 6a)6. In 1912, he identified a shift in the spectral lines towards the red end of the spectrum in distant galaxies (Figure 6b).7 He later equated the redshift with recessional movement of the galaxy (i.e. movement away from earth). This was a critical observation that Hubble later applied in his research.
Conclusion
The preceding sections might have contained more technical information about astronomy than you ever desired! Thank you for hanging in there! The concepts are critically important to help you understand the brilliance of Edwin Hubble and the significance of his work (Part 2).
Regarding “time” as expressed through astronomy, hopefully you noticed a phrase in the Cepheid Variable section from Henrietta Leavitt’s work “…extends distance calculations to stars that are millions of light years from earth.” The term “light year” was used to describe distance, but it also means that the light reaching earth has been traveling for millions of years.
Cosmological Redshift
If you slowly release hydrogen from a container, burn it, and look at the light through a spectrometer (similar to a prism – divides the light into a color band), several black lines are evident in the spectra. Termed “absorption lines” they occur at specific frequencies (see Figure 6b) unique for each chemical element. Vesto Slipher discovered that the absorption lines in the light spectra from distant galaxies are shifted toward the red end (Figure 6b).
Yes, the “heavens” also suggest extremely old ages for God’s creation.
Part 2 will reveal how Edwin Hubble’s work tied all this together into a complete picture of the cosmos. It also provides the foundation for how astronomy can bring astronomers to a belief in God!
1Wikipedia; James Bradley; https://en.wikipedia.org/wiki/James_Bradley
2Wikipedia; Aberration (astronomy) https://en.wikipedia.org/wiki/Aberration_(astronomy)
3Wikipedia; Luminosity https://en.wikipedia.org/wiki/Luminosity
4Wikipedia; Henrietta Leavitt https://en.wikipedia.org/wiki/Henrietta_Swan_Leavitt
5Wikipedia; Cepheid Variables https://en.wikipedia.org/wiki/Cepheid_variable
6Wikepedia; Vesto Slipher https://en.wikipedia.org/wiki/Vesto_Slipher
7Wikepedia; Redshift https://en.wikipedia.org/wiki/Redshift
Figure 1. Mt. Wilson Observatory – the Hooker telescope is enclosed within.
Figure 2. The 100 inch (mirror) Hooker Telescope
Figure 3. Original control panel and the base (mirror assembly) of the Hooker telescope.
Figure 4. Photograph of Henrietta Leavitt during her tenure at the Harvard University Observatory.
Figures 5a and b. Brightness variation of the delta-Cepheistar star showing a period of 5.4 days (Figure 5a); and, plots of Herietta’s data showing the relationship between the brightness (Y-axis) of the 25 Cepheid Variables she studied and the log of the time period (X-axis; Fig. 5b).
Leavitt, Henrietta S; Pickering, Edward C – “Periods of 25 Variable Stars in the Small Magellanic Cloud” Harvard College Observatory Circular, vol. 173 (for Figure 5b).
Figure 6a, b. Photograph of Vesto Sliper during his tenure at the Lowell Observatory (Fig. 6a) and an example of the redshift phenomenon that he observed between nearby galaxies and extremely distant galaxies.
