Thursday, October 24, 2013

Great galactic distances

Artist's rendition of z8_GND_5296.
Image source.
Science headlines today proclaimed that the most distant known galaxy, affectionately named z8_GND_5296, was discovered by a team of scientists using a new spectrograph on the Keck I telescope, located on the slopes of Mauna Kea in Hawaii.  The headlines are a bit misleading, however, in that the galaxy in question is the most distant "spectoscopically confirmed" galaxy, according to the editor's summary of the article in Nature.  There appear to potentially be several much more distant galaxies, but the distances of these have not yet been confirmed by spectoscopic methods.

Spectroscopy is not a direct method of distance measurement, which is why a specific distance is not reported.  Instead, they say that the galaxy is at "redshift 7.51" and that we see the galaxy as it was 13.1 billion years ago, 700 million years after the Big Bang.  "Redshift" refers to the tendency of light to lose energy as it travels from celestial objects to earth, causing light in the visual part of the spectrum to shift toward the red end, hence the name "redshift."  This shift is considered to be a type of Doppler effect on light, and it is normally attributed to the ongoing expansion of space, an idea which is closely associated with the Big Bang model.  It is difficult to determine just how much spectroscopic distance measurements therefore rely on the Big Bang model, so I am unsure how much interpretation is involved in these measurements.

The distance and age of stars is often a point of contention in debates about the origin of the universe.  Light, so far as we can tell, has a consistent speed in vacuum at 299,792,458 meters per second, or about 671 million miles per hour.  By definition, one lightyear is the distance light travels in a vacuum in one year, about 10 trillion kilometers (6 trillion miles).  It initially appears, then, that any object millions or billions of lightyears away, such as our friend z8_GND_5296, would have to have existed for millions or billions of years in order to give off the light that we see.  This seems to contradict the Genesis account, which places the creation of stars on Day 4 of Creation Week (Genesis 1:16).

Creationists who believe that Creation Week was only about 6000 years ago have presented several explanations for this apparent discrepancy.  First, there is the issue of the actual distances to the stars.  While most astronomers consider redshift spectroscopy to be a perfectly accurate quantitative method of measuring distances, some would disagree.  Halton Arp, an expert on quasar and galaxy observation and a non-creationist, has reported numerous problems in the process, claiming that factors other than space expansion seem to significantly affect redshift.  I will not attempt to relay all of his claims and findings here, but you are welcome to read a review of his book on the Answers in Genesis website.  As I mentioned earlier, measuring distances with this method has close ties with the Big Bang model, so if this model is inaccurate, then spectroscopy might not be as reliable as it is presented.  Granted, spectroscopy is not the only method of measuring distances to stars.  An earlier, more direct method involved measuring the precise angles formed by the sun, the earth, and a star six months apart.  Given the diameter of earth's orbit around the sun, a few trigonometric calculations easily determine the distance of the star.  A similar method uses perspective and the star's apparent position relative to other stars to determine the distance.  Even if the measuring techniques aren't entirely accurate, many stars still appear to be much more than 6000 lightyears away.

Some people claim that God could have simply created the light in transit to earth during creation week.  This is often the first explanation that creationists (including me) invent when confronted with the starlight problem.  However, I have theological issues with this explanation.  It implies that God is showing us a cosmic history that never actually happened.  We observe stars and supernovae that never actually existed.  In my opinion, this comes far too close to calling God a liar.

Dr. Russ Humphreys and Dr. Larry Vardiman of the Institute for Creation Research wrote a very interesting, and somewhat technical, article (Part 1, Part 2, Part 3) that proposes a method by which God could have used relativistic effects to effectively age the distant stars by millions of years and bring light to earth during a single 24-hour day of Creation Week.  As any evolutionist will readily point out, there is not yet any observational evidence to back up this explanation, but I believe it stands as one of the most promising models for starlight in the biblical framework.  For now, however, all we can do is speculate.

Finally, I would like to point out that z8_GND_5296 was reported to have a star formation rate over one hundred times that of our own galaxy.  The authors of the study suggest that star formation may have been more intense after the Big Bang than previously expected.  In view of Humphrey's and Vardiman's model, though, I can't help but wonder if we are watching the galaxy in fast forward due to relativistic effects.  Again, this is simply speculation, but that detail is potentially significant to the origins debate.

After several hours of research, all I can really say for sure is that astrophysics is weird and complicated.  Because of that, it is difficult to take any such findings for granted.

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