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The Transit of Venus

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June 5, 2012 Tags: Earth, Universe & Time
The Transit of Venus
Image of the last transit taken in Philadelphia on June 8, 2004, by a group of observers including Ted Davis.

Today's entry was written by Faith Tucker. Please note the views expressed here are those of the author, not necessarily of BioLogos. You can read more about what we believe here.

Today we have a chance to witness a special moment in history as Venus transits across the disk of the Sun for people across the world to see. This rare astronomical occurrence may have been witnessed by Montezuma in 1520, was first predicted by Johannes Kepler in 1631, launched Captain James Cook’s expedition around the world in 1768, helped us determine the Earth's distance from the Sun in the 1882, and will not occur again until 2117.

The astronomy community is particularly interested in this event because exoplanets throughout the Milky Way galaxy regularly transit their parent stars in just the same way. This local example will allow astronomers to test and refine techniques used to determine the composition of these exoplanets' atmospheres, providing insight into whether these distant planets could possibly harbor life.

As Venus begins to cross in front of the disk of the Sun, Venus's atmosphere will refract the Sun's light, illuminating the backlit portion of the planet's atmosphere. Telescopes on the ground and in orbit will be trained on this thin arc of atmosphere lit up by the Sun. Astronomers will use spectrometers to break the light up into its constituent colors, from which they can determine the chemical composition of our over-heated sister planet's atmosphere. Once perfected, this same technique can be used to examine the atmospheres of planets far beyond our own solar system, offering us one of our best clues as to the habitability of these distant worlds.

Not only is this process of discovery exciting for natural science, but it has profound theological ramifications as well. Surely a God capable of orchestrating both the majestic swirls of a spiral galaxy and the intricate language of DNA could bring forth life where and when He chooses, but only now are we on the verge of being able to answer the age-old question: “Did God confine His creative life-giving actions to our own planet, or does His abundant fertility extent far beyond our limited experience?”

In 1882, William Harkness, the Director of the U.S. Naval Observatory, was one of two astronomers to determine from the transit of Venus the distance from Earth to the Sun. Just as previous viewers could never have imagined calibrating the scale of the solar system from such an event, Harkness could not predict its importance in 2004 and 2012 (the most recent Venus transits). As we look to the future, we can hardly imagine what new frontiers the next Venus transit of 2117 will find us exploring.

"We are now on the eve of the second transit of a pair, after which there will be no other till the twenty-first century of our era has dawned upon the earth, and the June flowers are blooming in 2004. . . . What will be the state of science when the next transit season arrives God only knows. Not even our children's children will live to take part in the astronomy of that day. As for ourselves, we have to do with the present ..." ~William Harkness, the Director of the U.S. Naval Observatory, quoted in 1882 (source: NASA.gov)

The image above shows Venus on the eastern limb of the Sun during the 2004 transit. As described in Tucker's essay, the faint ring around the planet comes from the scattering of light through its atmosphere, which allows some sunlight to show around the edge of the otherwise dark planetary disk. The faint glow on the disk is an effect of the TRACE telescope through which the image was captured. For more on the historical significance of the transits of Venus (including the voyage of Captain James Cook), see this article from NASA, which also includes links to several live webcasts of today's transit.

Faith Tucker graduated from Whitman College in Walla Walla, WA in 2011 with Bachelor's degrees in both Astronomy and Religion. At Whitman, she was a student leader of the campus's InterVarsity chapter and gave planetarium shows to students of all ages. Since graduating she has spent time working in astronomy education and public outreach at the NASA Goddard Space Flight Center in Greenbelt, MD and is currently a Project Coordinator for the American Association for the Advancement of Science's program on the Dialogue on Science, Ethics and Religion.

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Bilbo - #70278

June 5th 2012

Thanks, Faith!  I was just going to try to find the best place to see the transit of Venus when I saw your article!  Thanks for the info!

While we’re on the topic, I was wondering if you have an opinion on the Rare Earth Hypothesis of…was it Brownlee and Ward?

Faith Tucker - #70317

June 7th 2012

I’m glad you found it helpful!
As for the Rare Earth Hypothesis - that is, the idea that the Earth is extraordinarily rare and unique and thus it is highly unlikely that there are any other planets capable of harboring life in the universe - I think it’s a very interesting conversation and a subject we still have a great deal to learn about.
The Rare Earth Hypothesis stands in contrast to the widely accepted Copernican Principle, which posits that there is nothing remarkable or exceptional about our planet, our solar system, our galaxy, etc. From this line of thinking, it follows that what we find in our own Milky Way galaxy should give us a good idea of the make up of other galaxies throughout the universe. And so, just as many stars in the Milky Way have their own exoplanets (astronomers have identified well over 2000 candidate planets already!), it would be reasonable to assume that stars in other galaxies also host planets of their own. Considering there are hundreds of millions of galaxies in the universe, each of which contains on the order of billions of stars, we are talking about billions of billions of planets in the universe!
If this is indeed the case, then it would, statistically speaking, be nearly impossible to support the idea that the Earth is the only planet that happens to have conditions necessary to support life, even as precise and delicate as those conditions are. However, just because a planet has an equivalent size, orbit, atmosphere, etc does not necessarily mean that it does indeed harbor life.
Our knowledge of exoplanets and astrobiology is increasing at a very high rate, but there is still a great deal that we don’t know. Current missions and research projects are constantly giving us new insights, but for the foreseeable future we will always be limited to the stellar systems in our local region of the Milky Way galaxy so I suspect that many of these questions will remain with us for quite some time.
I hope that helps!
Bilbo - #70341

June 8th 2012

Hi Faith,

You wrote:  “If this is indeed the case, then it would, statistically speaking, be nearly impossible to support the idea that the Earth is the only planet that happens to have conditions necessary to support life, even as precise and delicate as those conditions are.

I guess it depends how long our list of necessary conditions is, and what the probability of each condition is.  Ward and Brownlee list ten conditions (pp.274-275) they think necessary.  If we assigned a probability of 10% to each condition I think that gives us 10^-10, or about one in every 10 billion planets.  Some of those conditions may be far less than 10%.  For example, if the present theory of how we got our moon is correct (an incredibly accurate collision, at just the right angle, velocity and mass, with another planet), and if that is the only way to get a large moon (a necessary condition), we would be dealing with conditions that were far less than 10^-10, making their conclusion “that Earth indeed may be extraordinarily rare” rather reasonable.

But I don’t want to destroy your hopes.  Keep the faith, Faith.

Bilbo - #70281

June 5th 2012

I just saw the transit of Venus live through a telescope!  Absolutely cool!

KevinR - #70287

June 6th 2012

“Not only is this process of discovery exciting for natural science, but it has profound theological ramifications as well.”

Well, it certainly has theological implications - but from a different point of view. A few  scientists have actually raised the questions that have puzzled them for a long time now:

Why, if earth and Venus are so similar in size, with closely the same distance from the sun, did they get to be so starkly different. Earth is the veritable paradise as far as life is concerned whereas Venus is the bespoke hell in comparison. What they are pondering is why if the two planets formed out of the same cloud of dust and ended up with a similar terrestial makeup, did the one turn into an inferno and the other drowned in water? They cannot understand this particular issue because of their naturalistic worldview. There just is NO explanation for such an outcome from a one-cloud-of-dust origin for the solar system.

In fact, there is just no explanation for the existence and charateristics of ANY of the planets from such a naturalistic start. The nebular accretion theory of planet formation falls flat on its face for ALL of the planets in the system.

Of course, if one intelligent agent with supernatural abilities designed it and built it then there is no problem. But then one has to believe that God had a direct involvement in it. There’s no hand-off naturalistic explanation to rescue the situation.

Furthermore - the planets in the solar system defies the assumption of billions of years. Everywhere evolutionists have to make highly unjustified assumptions [ e.g. catastrophic crashing of unknown bodies] to bring actual observations evidence for a much younger age in line with the nebulous theory.

The theological implications are simply this: There is no place for billions of years in the bible and one does not have any need to try and put them in there. One can have full confidence that the bible relates the truth when read in a straighforward way.

Bilbo - #70296

June 6th 2012

Hi Kevin,

Okay, you’ve given a good example of a God-of-the-gaps argument:  We don’t have a satisfactory natural, non-intelligently-caused explanation for the origin of the planets in our solar system.  Therefore, God must have done it. 

But now let’s suppose that we find out that each and every planet has served a very specific purpose in the solar system, so that if they had been a little bit different then the purpose would not have been fulfilled.  Now we have an ID argument:  No natural, non-intelligently-caused explanation + phenomena that look like they are intelligently designed to a very specific degree = concluding or at least suspecting that these phenomena are intelligently designed is very reasonable.

Uncle Bonobo - #70304

June 6th 2012

Well, when you start with the incorect premise that Venus and Earth are"closely the same distance to the Sun” you’re bound to go astray. 


Venus is 2/3 the distance from Sun to earth.  Its relative proximity to the sun and its CO2 atmosphere explain the planetary dfferences pretty well.


It’s very difficult to practice YEC science—YEC and science don’t go well together.

George Bernard Murphy - #70310

June 6th 2012

Kevin, the planet venus does not rotate like earth 

If you were standding at the equator of Venus you would be traveling 6 miles per hour.

If you were standing on earth’s equater you would be traveling 1000 miles per hour.

 [The earth is 24000 miles in diameter and it rotates once every 24 hour.]

Earth’s rotatation which was imparted by  a collision with another planet was discovered by the Apollo program,. the greatest scientific endeavor in tha history of mankind.

 The is a video on youtube by Robin Canup which explains it.

 The people on Biologos usually block any reference to that video.

 Lets see what they do this time.

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