Bad Calculation: The Case of the Shrinking Comet and the Age of Solar System

Ten years after launching, the European Space Agency Rosetta spacecraft caught up to its target: Comet 67P.   In 2014, Rosetta, now 250 million miles from Earth, traveled along with the comet while it made its way around the Sun measuring its increased activity including classic comet tail formation as it approached the sun.  At one point Rosetta detected and measured streams of water vapor spewing out of the comet at an estimated rate of 600 milliliters per second. 

An overexposed image of Comet 67P showing jets of water vapor emanating from the comet. Image: ESA
An overexposed image of Comet 67P showing jets of water vapor emanating from the comet. Image: ESA

It was this water loss measurement that seems to have inspired then Institute for Creation Research (ICR) science writer, Brian Thomas, to crunch some numbers in an attempt to estimate the lifespan of this comet.   Where his calculator lead him was to the conclusion that Comet 67P couldn’t be billions or even millions of years old.  Here is what he concludes in an article entitled: European Spacecraft’s Comet Close-up a World First

… first measurements from the Microwave Instrument for the Rosetta Orbiter, MIRO, suggested that the comet was emitting water vapour into space at about 300 millilitres per second,” according to the ESA.

That’s over six-thousand gallons per day! At that rate, the whole comet—assuming it’s made entirely of water ice—would melt into space after only hundreds of thousands years. The dumbbell-shaped mass spans two and a half miles across its longest axis. If this comet was really a “primitive building block of the Solar System,” then it’s supposedly 4.5 billion years old. Why is it still around if it keeps getting smaller as it swings around the sun every six and a half years?

Comet 67P/Churyumov–Gerasimenko’s mass shrinks not only from water-vapor loss, but solar wind also blows away material as it orbits nearer the sun—between Earth and Mars when it’s closest. If it’s really billions of years old, why isn’t this comet old, cold, and dead—why does it exist at all? Rosetta’s investigation has not yet entered full swing, and already reveals the comet as looking young, warm, and alive.

He seems to have appoint. After all, If the comet is shedding this much mass every time is passes by the Sun then it should eventually disappear.  It appears that a simple calculator, mass loss over time and an estimate of current mass of the comet is all one needs to prove the solar system must be young.   Thomas concludes that this comet will disappear in a mere several hundred thousand years. I haven’t checked his math but he is likely right on this point: at 6000 gallons a day, this comet can’t last billions of years.

Why then are secular scientists not able to see the obvious truth?  Obviously the solar system and the Earth itself can’t be billions of years old if this comet can’t be old.

Thomas is missing quite a bit of the story but there is a critical piece of information that he should have known about had he done any background research on this comet before doing his calculations and writing his article.

For Thomas to argue that the comet can’t be 4.5 billion years old he must accept a false assumption.  He has assumed the orbit that brings the comet close to the Sun today and resulting in the loss of water vapor, is the same orbit that the comet has always maintained.  In other words, he assumes a strict form of uniformitarianism to do his calculations.  If the orbit were not the same then the amount of material being expelled from the comet would have changed over time and he could not back-calculate how long the comet would survive and conclude that it could not have existed for a billion years or more.

If the orbit of the comet in the past did not bring it in close proximity to the earth them the amount of water vapor loss would be drastically reduced.  So we need to ask the question, is there evidence that the orbit of this comet has changed in the past?  Thomas  could have spent five minutes with Google to find the answer: yes the comet has changed its orbit and not that long ago.  Here is what NASA has concluded about this history of this comet:

Analysis of the comet’s orbital evolution indicates that until the mid-19th century, the closest it got to the Sun was 4.0 AU (about 373 million miles or 600 million kilometers), which is roughly two-thirds of the way from Mars’ orbit to that of Jupiter. That far from the Sun’s heat, it would not sprout a coma or tails, so it was invisible from Earth.

But scientists calculate that in 1840, a fairly close encounter with Jupiter must have sent the comet flying deeper into the inner solar system, down to about 3.0 AU (about 280 million miles or 450 million kilometers) from the Sun. Churyumov-Gerasimenko’s (67P) perihelion (closest approach to the Sun) drifted a bit closer to the Sun over the next century, and then Jupiter gave the comet another gravitational kick in 1959. Since then, the comet’s perihelion has stood at about 1.3 AU, which is about 27 million miles (43 million kilometers) outside Earth’s orbit.

What have learned?  As recently as 1840 the closest this comet came to the Sun was 373 million miles but today–when our measurements of water vapor were made–it comes a bit closer than 120 million miles from the Sun.  In 1840 most of its orbit would have been spent much further way than 373 million miles and therefore would have been unaffected by the sun effectively expelled no water at all.  Had we used Thomas’ simply method of calculation of comet lifespan in the year 1840 we would have estimated that the comet may live for another billion years and have lived billions of years before.

This shows the path that Rosetta has taken to catch up to Comet 67P
This shows the path that Rosetta has taken to catch up to Comet 67P.  Rosetta has circled the Sun multiple times using the gravity of Earth, and Mars to help speed it on its way out to meet with the comet.  The trip has taken 10 years.  I still find it amazing that we can put something in orbit around a 1 mile diameter object almost 300 million miles away.

But where you there?  How do we know the orbit has changed in the past when no person was there to document the change?  We can know this with great confidence because scientists have a good understanding of Newtonian mechanics.  Laws of the effects of mass, gravity and motion can be used to trace the orbit of this comet back in time along with the orbits of the planets. Doing so reveals that in 1959 the orbit of the the comet brought it very close to Jupiter. We can calculate based on the mass of the comet and Jupiter what the effects would have been on both orbits.

Does it sound impossible to do these calculations?  Consider that we have sent a spacecraft to Jupiter by sling-shooting it around Earth and Mars and then have directed it around Jupiter for a decade.  We can very precisely predict the path of objects in motion in space which is why we know when we will see other comets like Halley’s comet again. The Rosetta spacecraft itself was sent on a wild set of orbits to get to the comet all calculated using Newtonian principles.

This is not rocket science! :-) These are straightforward calculations that have been used with great success to predict and send spacecraft into orbits.

If our orbit calculations are even close to predicting the history of this comet there is every reason to believe that this comet has survived quite happily in the outer solar system for billions of years.  This and other comets that come close to the Sun are not evidence of a young creation. If they tell us anything about the age of the Universe they tell us they are products of ancient processes.  See also:  As the Asteroid Tumbles: Asteroids and the Age of the Solar System

The calculations that lead us to that conclusion are not quite as simple as those performed by Thomas but he should have known that the orbit of a comet would not be expected to be the same over time since there are large planets whose gravity will cause it to change over time.   It appears that Thomas has yet again managed to illustrate his unwillingness to do basic background research before writing an article or worse yet keep his audience in the dark about evidence he knows contradicts his conclusions. This is a disservice to his audience and reflects poorly on the credibility of ICR as self-proclaimed source of science information for evangelical Christians.

By making it sound like the existence of this comet should be a mystery to astronomers and that this should cast doubt on the age of the Universe, what Thomas has written is not a science story but rather a science fiction story.

Not long before he wrote this article, Thomas he was telling us that a layer of pebbles buried 770 feet below the Dead Sea was evidence of the destruction of Sodom and Gomorrah (Origins of the Dead Sea: All Dried Up – No Room for a Dry Dead Sea in the Young Earth Timeline).  There we discovered that he hadn’t done sufficient background research to discover that articles published by his own organization contradicted his claims.  Those of us that read Thomas’ work will recognize that these examples aren’t simply rare lapses in attention to detail but rather they represent a longstanding pattern of misreading sources, not reading sources, or simply making up hypotheses to fit stories with no regard to their plausibility.

I understand that the focus of his job is to provide an alternative way to interpret current news stories to fit a young earth paradigm, and so I don’t expect him to admit or believe that the data don’t support his overall worldview.  But it is one thing to have a different interpretation of facts, and it is another to be unaware of basic information necessary to understanding a story. To be so unaware invariably leads to a wrong interpretation of the evidence.  Unfortunately, Thomas is a trusted authority for many Christians who are looking for evidence that science supports their young-earth interpretation of the Bible.  That trust is misplaced.

That misplaced trust can be seen on the Facebook comments section of ICR, AIG or CMI where so many of those comments confidently use YEC arguments that Thomas and others have provided to chastise other Christians.  One comment that really stuck out to me (unfortunately I didn’t take a screenshot at the time) proclaimed “astronomers are idiots for believing the Universe is ancient because a simple calculator will show them that it is young.” This was a clear reference to Thomas’ article on Comet 67P which had just come out.  This person believes that Thomas is doing good science and presenting them with not only facts but good interpretations of those facts.  A frustrating comment, yes, but I’m sympathetic to that person’s plight. They want to believe they have physical evidence for something they already believe must be true—that the earth is young.   What I have less sympathy and more frustration for are individuals that are in a position of authority.  They are the ones who place their followers in the position of looking foolish when they repeat their unjustified claims.

The ends don’t justify the means. God is not glorified by poor scholarship.  At times, I have been too quick in my assessment of data.  I have not done my due diligence in reading the original research articles before I comment on them or use them to support my position.  I have been quick to criticize without questioning my own assumptions. When that has happened no good has come of it.  Each time I do so, I have lost some of the trust of those that look to me to provide accurate reporting and to provide analysis that is based on thorough background research.

Our recognition of God’s glory in creation is blunted when we seek to distort its message even if we believe that we are doing so for the right reasons.  I am sure that many YECs believe I am the one that is engaged in distortion. I don’t think so for many reasons that I have discussed on this blog. But I do pray that I would be faithful in my studies of God’s creation. That I would glorify God through my love of His Word and His creation.  And if that is not the case, that He would reveal my errors to me and lovingly discipline me.

The dumbbell shaped Comet 67P.  The Rosetta satellite is presently orbiting this comet as is passes around the Sun.  Image:  Planetary Society/ESA
The dumbbell shaped Comet 67P. The Rosetta satellite is presently orbiting this comet as is passes around the Sun. Image: Planetary Society/ESA

This article is an updated version of one originally published in 2014.

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