The YORP Effect

No, I didn’t spell it wrong, and it’s not slang.

The YORP effect is named after four scientists who worked out the way that photons can cause small space objects to spin. Now, small can mean a lot of things. If we are talking about asteroids, we are talking about objects of a few miles or a few tens of miles in diameter. Since many asteroids are clumps of rocks, rather than a single rock, a spin could overbalance the light hold of gravity and cause them to break up. In fact, there are many double asteroids, and the YORP effect seems to be the reason.

By the way, the four scientists are Yarkovsky, O’Keefe, Radzievskii, and Paddack. I knew you wanted to know.

And just for the record, there is one asteroid, 1862 Apollo, which gains about 4 minutes a year in its rotations. Whopping spin! If the earth slowed like that, we’d squeeze another month into the calendar every 10,000 years. If it sped up like that, we’d lose a month and be standing still by now.

But YORP isn’t just a matter of speeding up or breaking up asteroids. We have been talking about dust in Earth rings. Individual grains of dust can also have a spin. The spin comes about because the photons hit the dust grains and push them around. Furthermore, they heat the grains unevenly because they are grains, not spheres, and then the grains give off the heat again, with the same kind of thrust we have on a rocket when it’s burned gases go out the back. It’s a very small thrust, but remember that grains of dust in space are also small, and are not floating in the sort of atmosphere that could quickly damp a tiny thrust. They’re out there in a vacuum, and whatever motion begins goes on and on. If photons hit them repeatedly – when photons hit them, all day every day, they can begin to spin and then spin up a little more and a little more. Then when they bump each other, as they are bound to do, they are going to get all ground up.

Thus, the YORP effect makes the ring material get dustier over time. We’ll come back to the dust.

Phoebe ring

I have been trying to find out the reason for the name Phoebe for the second set of rings, the ones whose orbit is tilted towards the Moon. Wiki informs us that Saturn has a moon named Phoebe, and just inside the orbit of Phoebe is a ring that is clearly composed of dust from Phoebe. It is clear for several reasons, but the simplest is that Phoebe orbits Saturn in the opposite direction of most of its other moons, and the dust in this nearby ring orbits in the same unusual direction.

So the hypothesized Moon-oriented ring is called the Phoebe ring.

And I figured out how to embed the YouTube I linked before.


The Phoebe Ring

So we have asked whether the Earth has a ring made of dust, and we suggested the Moon might supply the dust. But then… if the dust comes from the Moon, why does it form an equatorial ring around the Earth? Why isn’t it in a ring tilted towards the Moon?

Because that’s the natural way for rings to arrange themselves. No matter where the stuff comes from, if it gets into an orbit around the Earth, it will eventually get into an equatorial orbit. James Clerk Maxwell had this in his equations. The bits of dust (or rocks, whatever comes) will bump into each other as long as their orbits are irregular; once they get into an equatorial orbit, they will settle quietly and stop jostling each other so much. There will be, as we will see, still some jostling for various reasons.

So, the grains of dust will “tend” to fall into equatorial Earth orbit. But they will indeed start out in an orbit oriented towards the Moon, even an Earth-Moon orbit, circling the gravitational center of the Earth-Moon system. Step by step, the dust will fall into an Earth orbit oriented towards the Moon, and then into an equatorial Earth orbit. So: a handful of volcanic dust sweeps up into the non-atmosphere of the Moon and starts to orbit the Moon. Pretty quickly, the Earth begins to rob the Moon dust, pulling everything towards and then into Earth orbit, an orbit tilted towards the Moon, an orbit crossing the Earth’s equator but not centered on it.

Gradually, grain by grain, the dust settles into an equatorial orbit.

How long does that take?

I don’t know. A while. But we hypothesize that if there are Earth rings made of Moon dust, (nothing else could reasonably supply enough dust,) there are probably two sets of rings. One is an equatorial disc; the other disc is oriented to the Moon and for now, we are calling it the Phoebe Ring. We can draw the rings in different colors to make things clear, but in fact, both discs contain the same dust, younger, more recently arriving dust in the Phoebe ring, older dust in the equatorial ring.

Phoebe Ring

Now things get interesting, because the Phoebe ring does not follow our seasons. It continues to track the Moon until its dust either falls into the equatorial orbit or falls to Earth altogether. This is going to be very messy. The new ring-shadow is on a journey, which may cause it to fall north in winter or summer, which may bring it edge-on at any time of the year, or rather it will become edge-on at various times as the years go by. It may be more or less coordinated with the equatorial ring or completely at odds.

How well do you know the Moon calendar?

The Phoebe Ring will be cyclic because the motions of the Moon are cyclic, but it won’t be tracking our seasons, which is really the only cycle most of us notice. (Do you actually know, right now, the present phase of the Moon?) If the Phoebe Ring exists, it will, when thick, cause storms at times of the year that can only seem completely random.

Think about the date of Easter and how it floats. It’s the one part of our cultural life that is still based on the Moon. The calculation is:

  1. it’s the first Sunday
  2. after the first full Moon
  3. after the vernal equinox.

The vernal (spring) equinox is March 21 or 22. Any of the next 28 days can be the first full Moon after that. And the next Sunday could be 6 days later. This means that the date of Easter could be any one of 34 days, and that, in turn, should help you recognize that the interaction of the solar year and a Moon ring can vary quite a bit.

The tides are another reminder that the Moon affects the earth, and their phases are enormously complex. They are caused by the gravity of the Moon itself, not by rings, but because of them, we do pay attention to the tides and to the phases of the Moon; it is a cycle for which we have charts and guides.

It is not an easy cycle.

Here’s a simulation to get used to the idea of a ring… and its shadow…  and maybe peek at two rings. youtube=http://www.youtube.com/watch?v=YwO93KeCrmI

What if Earth had an equatorial ring”

The first set of rings we need to visualize simply orbits the equator of the earth. It’s not just one ring, however; it’s a whole raft of them, arranged concentrically.

To get an idea of what I am saying, look at the Saturn ring images. Here is especially good one from Astronomy Picture of the Day,  (a site that will send you daily spectacular images if you sign up.) This particular image was taken last December by our Cassini spacecraft, from the underside of Saturn’s rings, the dark side, away from the Sun. The dark band in the image is the thickest band of ring material – a bright ring as seen from Earth. Note how that dark band is casting a shadow on the lower hemisphere of Saturn.

Now let’s think about such a ring around Earth.

Earth orbits the sun, from west to east around the Sun. If its axis were perpendicular to the plane of its orbit, the Sun would simply cast the ring shadow on the equator, spring, summer, fall, and winter.

hypothetical rings

It would have weather consequences, but they would hardly be noticed because they would be the same year round and every year.

In fact, however, the axis of the Earth’s rotation is actually tipped 23° and this means that the Sun would fall differently on the rings at different seasons.

  • Near the time of spring and fall equinoxes, the rings would be oriented edge-on to the Sun, so that their shadow would not be spread out at all; it would be a thin line across the globe at the equator. A narrow and heavy ring shadow might depress the natural height of the constant equatorial ring of clouds at the equinoxes, and this could have a weather effect itself.

earth rings

  • In the summer (our summer) the sun would shine atop the rings, casting a shadow on Australia and the southern hemisphere while we have no shadow at all. This would make Australia’s winter cold, which winters are anyway, but if the ring is thicker, the winter would be even colder than usual. Our own summer would not be affected. It would just be warm.
  • In winter, (our winter) the ring would be now illumined from below and Australia’s summer would be unaffectedly warm while our winter would be colder than usual especially if the rings were very heavy with dust. So far, this does not seem very significant. The rings make winter colder. Who would notice, since winters are always cold and we can’t see the rings anyway?
  • Between the pencil-thin and the all-spread-out-in-one-hemisphere orientations, there are all the variants. This is interesting. Think of the time shortly after the pencil-thin shadow of the equinox. Now there is a wider shadow, gradually spreading north in the winter, gradually spreading south in the summer. Even if it’s so diaphanous we can’t see it, it will still have a definite edge, depending on how thick the ring is, and any shadow’s edge is going to be windy. The air in the shadow is cooled, the cool air sinks and slips in below the warm air nearby. That makes wind. Big winds make storms. Since it is all coordinated with the seasons anyway, it is not particularly noticeable, but it is real.

This is the simple part of the ring hypothesis. It’s worth taking a few minutes to get it straight, because the next part is very complicated.


This is a very long thought, but I would like to entertain this question: what if the Earth had rings?

You might answer immediately: Well, it doesn’t.

But suppose they were very light rings, just composed of dust, most of which fell to earth from time to time so that sometimes the rings were very sparse indeed, and other times, they were thicker? They might not be visible unless you knew exactly where to look for them – and unless you looked. There are always lots of things that people don’t see because they don’t know what to look for.

The most commonplace unseen is sundogs. Once you know what they are, you see then 50 times a year; maybe more. But the first time people hear about them is also the first time most people notice them. That has been true of my students and their families. Now and then, someone sees a very bright sundog and thinks it’s a rainbow. That’s because he knows so little about rainbows that having the red on the inside instead of the outside doesn’t bother him. The less you know, the less you notice.

But, you might say: For heaven’s sake, we’ve got satellites up there. We would certainly notice an earth ring. Scientists notice things.

Actually… scientists are like other people. They notice things that they are looking for, and sometimes, when they have really good instruments and are very full of curiosity, they notice something that is completely unexpected. The rings of Saturn, for example, were a complete stunner the first time we had close-up photos of them. Everyone was surprised, flabbergasted, actually. I remember. But taking the photographs was intentional.

Nobody has looked for very subtle Earth rings.

Now, if the Earth had rings, the source of the dust would have to be the Moon. In fact, it would just about have to be dust from lunar volcanism. Right now, the largest consensus says that the Moon is cold through to the center and there is no volcanism. Therefore, there is no point looking for Moon dust. So we don’t. The end.

I don’t belong to that consensus because my father did not and he knew more about the Moon than anybody.

Okay, that just sounds like, “My dad is bigger’n your dad.”

But let me mention just two more teasers for today.

First: if you read The Rime of the Ancient Mariner, you will find the line where Coleridge says,

                   Till clomb above the eastern bar,

                   the horned moon, with one bright star

                   within the nether tip.

Think about it. There cannot be a star “within” the tip of the horned (crescent) Moon because that would be a star between ourselves and the Moon. None such. But there were reports in Coleridge’s day of lights on the Moon in just that position.

Why? Maybe little green men on the moon were lighting campfires, or maybe there really is volcanism. Or maybe something else… I’m voting for volcanism, and I’m not in a crowd, but I’m not alone either. Something is going on up there and if it’s volcanism, it could throw up dust and some of the dust would not fall down on the Moon but would be caught up in terrestrial gravity.

I would like to take a few posts to explain the concept of earth rings. The reason they would be important and interesting, if they exist, is that they would have an effect on our weather. After all, they would cast a shadow. Not a big fat visible shadow, but a shadow nonetheless. The effect would sometimes be subtle and sometimes be strong depending on the thickness of the ring, and the effect would always be cyclic, but ring cycles would not necessarily match the Earth year. Instead, the cycles would match something in the lunar cycle as it interacts with the Earth year. It would be the sort of thing that you wouldn’t notice unless you knew exactly what you were looking for.

That’s my second the point. It would matter to a weather forecaster. My Ring forecaster is expecting a warm summer, likely to re-ignite the discussion of global warming, and a cold winter, likely to hush it some, and a bitter next March, likely to silence it for a bit.

There’s more.

God’s image

The universe is in God’s image: it has to be. In what other image could it be made? “Before the universe,” there was nothing, no image to copy, no starting point, no pattern. Serious “nothing” is much emptier than air and space.

Now, the image of God imprinted on the universe does not have the same aspect as the divine image that is imprinted upon us, because we are personal beings, and the universe is not. Let’s think about this a little before going on. When scripture says that we are made in the image of God, it uses a phrase that actually suggests sonship, the way that Adam’s children are in his image. The universe and its elements are not like that, and could not be.

Why not?

Take a minute to recognize that we ourselves could not be persons if our “parts,” – our hands, our feet, or our molecules – were other persons. Who would be in charge? Nor could we be persons if we were part of a planetary person, such as Gaia, because then the freedom to respond to destiny would either be located outside ourselves or else divided with others. That is what personal nature means: the capacity to seek a destiny with one’s whole being. It’s not about free will in the sense of trivial decisions, but about the capacity to seek our inwardly known destiny.

The universe cannot have this personal sense of destiny and still make room for our own. It is not part of God, and we are not part of it. But the universe does reflect the nature of God as the work of any artist reflects his nature and opinions, and for this reason it is always the case that new information about the universe, including new information from the natural sciences, can suggest new perspectives that are of interest to theologians, new ideas about God or deeper insights into his nature. These perspectives are just that, perspectives, not dogmas, and they do not excuse us from examining yet more of the universe. Each perspective has limitations; but each also has a new fund of truth.

But enough of abstractions. Let me give you an example of a perspective that was very quickly offered to counter the concept of an infinite universe which naturally arose in the wake of the Copernican insight that the universe was much, much larger than had been considered.

Olbers’ Paradox

If the universe were infinite, an infinite extension of space filled, or even just sprinkled, with an infinite number of stars, then the starlight converging on any given point of space would be infinite. For the light of an infinite number of stars, however weak, would add up to an infinite amount of light. Therefore the sky would not be black or even dark at any time, day or night.

You are thinking that if the stars were very far away, the light would not be infinite. That is an understandable objection, but it really depends on a sloppy concept of “infinite.” Infinite does not mean “really a lot” or “much more than usual.” It means there is no limit.

Somebody named Olbers pointed this out, and called it a paradox, meaning that he was surprised that these two statements should both be true: that the universe is infinite and that the night sky is dark. Actually, a paradox is only an apparent contradiction; this is a real one, meaning that one of the statements must be false. Since anyone can see that the night sky is dark, the universe must not be infinite.

There is a similar gravity paradox: If the universe had an infinite amount of matter, its gravity would be infinite, and it would disappear in a clap of thunder, or at any rate, a Great Collapse. Well, not even so; it could never break out in a Big Bang if the gravity were infinite. Again, the failure to understand this is the simple failure to understand the difference between “very large” and “infinite.”

One of the ways people try to get around these contradictions is to suggest that: in an infinite universe which is expanding (as ours is) some of the matter will expand so far away that it will move over the horizon of gravity. It will, in terms of relativity, apparently accelerate over the speed of light and its gravity will no longer affect what is left behind. But think about this. Even if gravity goes over such a horizon that it won’t affect you personally, it will affect something halfway between you and the horizon, something that does affect you. How does that work?

The answer is that it would work various ways at various times, and every so often, so much would be pulled together that it could not come apart, and over an infinite time, the Great Collapse would occur, perhaps in stages, but over an infinite time, there would be nothing left.

It could be worse: if the universe is expanding all the time, and if it is of an infinite age (infinite universes are always infinite in time as well as space) all the matter in the universe must already (in its infinite past) been completely scattered so that nothing but a tenuous puff of dust remains. How could there be a planet?

No, no, you say! The universe is constantly being created in the empty places, so its infinity keeps on going.

This is simply hilarious, and again, it is a failure of philosophy, a failure of thought, not of experiment. If the universe is self-generating in all the empty spaces, then there will be an infinite influx of matter coming towards us (towards any given point) from every horizon out there, and we will be crushed. Indeed, we will already have been crushed in the infinite past.

Stop thinking that infinite means “very big” and face it: the infinite is unimaginable. You need to think past your images; you need to use your reason all the way out to the end of the thought.

These two “paradoxes,” these twin impossibilities of infinite light and infinite gravity, were under discussion for hundreds of years, and it was a form of philosophical blindness for people to have gone on thinking the universe infinite. The progress of the natural sciences, which briefly suggested an infinite universe, very quickly turned around to demand a finite universe.

Gravity is not, as the ancients thought, just a condition of earthly things which seek the center of the earth; and light is not just a visually searchable property of celestial beings. Once these two material aspects of the physical universe were better known, once we understood that both gravity and light are law-abiding aspects of the material world and fully subject to mathematical laws, then the habit of assuming the infinity of the universe should have begun to collapse.

Instead, this habit persisted, and this was a religious and philosophical blunder. Indeed, it was a philosophical blunder whose persistence depended on the tenacity of religious unbelief and the consequent determination to avoid anything suggesting creation.

This is not to say that the finity of gravity and light prove the existence of God. We cannot jump from science to philosophy or theology in exactly that way; but the necessary finity of gravity and light do demand respect for the concept of a finite universe and attention to the implications of that finity. In that sense the face of God peers out from the mists of a dawn without a yesterday.

It is hard to be an atheist.

Whither cosmology

Cosmology and science

Let me offer two examples of the confusion of science and cosmology.

The Berenstein bears

Although I was never a fan of the Berenstein Bears, we did have at least one or two books in the house, and I remember coming across quite an odd little piece. The young bears were going on a nature walk or something, and one of them asked the fundamental question: what is nature? The answer was something like: “Nature is everything that is, or was, or ever will be.”

That’s not science, not natural science; it’s cosmology. Neither nature walks nor the natural sciences cover everything; specifically, they don’t cover the manner in which we come to make statements about all of existence throughout all of time like Papa Bear. We not only make such statements, but we believe that they are meaningful and true; again, these beliefs do not come from the realm of the natural sciences, for they cannot be verified in the quantitative, observational manner that is the hallmark of the natural sciences. Rather, they are rightly discussed from the combined perspective of common sense on the one hand and logic on the other. This combination is the leading edge of philosophy. These questions can, that is, be approached by reason, and by reasoning from evidence to conclusions, but the whole discussion is not part of the natural sciences.

In philosophy, the rules of evidence include things that cannot be measured. Philosophy works on things that are clear to us in our intellectual lives, but they cannot always be observed in the outward sense. Saying that “nature,” as in, “what you study on a nature walk,” is everything that is or was or will be is a sly reference to the prayer that praises God who is, who was in the beginning, and who ever shall be. Papa Bear is hereby suggesting that a good scientist is either a pantheist (thinking the whole cosmology is God) or an atheist who thinks there is no God, since nature is everything.

We can call him Papa Sagan, for he is taking this line from that old (20th century) pagan.

Call him what you may, this is not a correct definition of nature as the topic of the natural sciences. It is a statement of cosmology masquerading as a definition of science.

Giordano Bruno

You will have heard of Copernicus, and that he wrote a book explaining his reasons for thinking that the sun must be at the center of the cosmos. At the time he wrote it, the Church was trying to figure out the motions of the heavens so as to be able to calculate the actual date of the first day of spring and thereby plan her Easter celebration in relation to that day. Copernicus studied and wrote at the request of one pope, and his model of the universe (submitted 40 years later to a different pope) was of no concern at that time and he was not particularly criticized except in Lutheran circles where the literal reading of the Bible was a demand of doctrine.

For scientists of the day, the hardest thing about the Copernican model was the recognition that if Copernicus was right, the universe must be enormously much larger than they had thought. Saturn, for example, must be 700,000 miles away. It was simply unbelievable! (Actually, it’s more like 700 million miles away, but never mind that.)

Well, there was an Italian, named Jordano Bruno, who read Copernicus and became quite excited about the new map of the heavens. He understood the enlargement and quickly got comfortable with it. He understood and accepted the idea that the sun might be a star like other stars. So far, so good. Also, he had a prodigious memory, and he went around showing off his memory and teaching his memory tricks. Teaching the tricks was both interesting and important because some people thought he must be practicing sorcery to remember so much. Sharing his tricks helped prevent that story from becoming too dangerous.

Nevertheless, Bruno was definitely a smarty pants, deeply persuaded that his superior intelligence could not fail him. He reasoned, therefore, with no hesitation, that all the innumerable stars were other suns:

  1. in an infinite series,
  2. each with other earths,
  3. each earth with other peoples,
  4. each people with its own redeemer son of God, its own Christ
  5. and therefore the intelligent man should give up not only the celestial centrality of the sun, but also the cosmic uniqueness and centrality of Jesus Christ.

It was natural that such a string of reasoning should occur to someone, but none of the five listed steps was a necessary conclusion from the evidence, and in fact each step was erroneous, the first three being now demonstrably erroneous, and the others therefore having no reason to follow, either then or now.

What happens with a man like Bruno is that some people take his part because, in certain ways, he’s the smartest man around – or seems to be; of course you want to bet on the smart guy. Other people back away and mumble that “smarts isn’t everything,” whereupon they are considered stupid; maybe they are, maybe not; maybe they feel, correctly but without being able to express it, that he is thinking a little too fast for the size of his thoughts. There are only relatively few men who clearly see that not one of these five steps is actually demanded by logic or reason; only a few can explain why some of them must fall by the wayside.

In fact, reasons to reject Bruno’s conclusions quickly surfaced, not only in theology but in other fields of thought.

But my point is that this was a confusion of science and cosmology.

Now, just to close this topic: it is fairly well-known that Bruno was burned at stake for his opinions. His modern-day advocates claim that he was burned for being a Copernican, and he might have said so himself, but as you can see, the truth is a little larger. He was a heretic, as Copernicus was not.

Many people also know that Cardinal Robert Bellarmine stayed up with Bruno the entire night before the burning trying to dissuade Bruno from his opinions, for Bellarmine was deeply troubled about the whole business. Bruno boasted that Bellarmine was more upset about his burning than he was. In that, Bruno may have been right. It is a fact that, for the next quarter-century and not because he had nothing else to do, Bellarmine personally made sure the Galileo was protected. Galileo was not brought before the inquisition until after Bellamine died, and even at that point, the measures Bellarmine had taken probably saved Galileo’s life.

That said, let us return to the question: how much credence should we give to science? Perhaps we are asking: how much credence should we give to what some scientists call the inevitable cosmological consequences of science?

And the answer to that is: maybe some, but maybe none at all. The information we find in the natural sciences does have a cosmological echo and sometimes also consequence. But scientists are not always qualified to recognize those consequences. Sometimes they are not sufficiently restrained about drawing conclusions in a field they really don’t know.


Whither science

Whither Science?

The question was recently posed by a friend of mine: how far does science go, and how much credence should I give to it? 

It’s an interesting question because it was posed by a well-educated person with enough philosophical acumen that I knew he wasn’t trying to jettison his reason, the history of the study of motion, or the concept of cause and effect. He lives in the country and likes that life because he has a love of silence and reflection but he doesn’t live in a cave and doesn’t aspire to, and though a bachelor himself, he lives around – and enjoys — families who have children, so he sees the practicalities modern time-saving inventions.

On the other hand, I am sure he is disgusted with the interference of various bits of our digital culture and he perceives them as damaging to personal relationships including the ultimate personal relationship: the search for God.

That said, what of his questions:

  1. How far does science go?
  2. How much credence do I want to give it?

What is science?

Let’s begin by defining terms. The general term science refers to reasoning from evidence to conclusions. By this definition, even theology is a science if it is disciplined by evidence and is not merely Gnostic. It’s important to recognize this in a world where the general concept of science doesn’t include theology whatsoever. Anyway, since most people don’t think of theology as a science, and I don’t think that was what his question was about, let me orient the definition a little more specifically.

For what distinguishes the various sciences is not the use of reason, which applies to every science, but the rules of evidence. In reasoning about the way a butterfly hatches, time-lapse photography of its exodus from the cocoon would be a form of evidence. But the same video would not be worth much in reasoning about the value of a work of literature, other than as a sideline on a work like Girl of the Limberlost. Nor would photography suit as evidence in a theological discussion of the resurrection, though certain photographs might be interesting. The science of theology includes evidence drawn from scripture, from religious traditions, and from constant teachings. The science of literature includes evidence drawn from the consistent effect of clarity, beauty, and a certain luminosity that shines from the work into the hearts of many readers.

The natural sciences limit themselves to evidence that is based on observation and hearing, or weight and measurement (which are more formal kinds of observation), or certain mathematical operations which are yet a further extension of measurement. 

Please pay attention: all this does not mean that scientists only observe. That would be impossible and stupid. Scientists are people. When people say “science tells us” you can clap your hands right over your ears on the spot. Science says nothing; Science cannot talk. But scientists, like other people, make observations. Let’s talk about that.

 When you see anything at all, you are always comparing it with what you have seen before. Yes, always. That’s what the use of words means: we are putting things into categories if we can, or saying we don’t know how to if we can’t. So we see something and we compare it with what we have seen before:

  • it is the same,
  • or it is different in a way that we understand,
  • or it is different in a way that reminds us of other things we have seen, so we wonder if it will have ramifications like those things
  • or it makes no sense and we try to list its elements so we can think about them later.

It is a striking fact of experience that when we really don’t understand something, it is very hard to observe it in an orderly manner. The more you know, the more you notice; the less you know, the harder it is to sort your observations or to guess which aspects of a new observation are the important; and the easier it is to pass over something that makes all the difference.

How much credence shall I give to science?

Now, to ask “how much credence should we give to science?” might mean to ask whether we should make any observations at all. There’s a kind of Gnosticism or pseudo-mysticism that wants to make no observations. That’s not what my friend is asking about.

So perhaps he was asking, “how much credence should we give to others’ observations?” which is much harder to answer. Whose observations are we talking about? Those of an honest person? Or of someone whose preconceptions always cloud his ability to observe? Is our observer aware of his preconceptions? How carefully has he examined them? After all, when we are seeing something new, none of us know quite what should claim our attention. What are the chances he gave his attention to the wrong things and is now directing my attention the wrong way?

Some of these questions may be set aside in view of the power of modern instruments. If you have a camera, you get the exact colors of the bird’s plumage whether or not you have good color discrimination yourself. Similarly, the position of Venus in the sky can be marked with a telescopic camera and its exact relationship with “nearby” stars on a particular date is not in doubt unless someone has mixed up his photos or is flat-out lying.

But the first problem we may have in science is our personal evaluation of the guy who is claiming that his observations are what he says they are. It’s a huge problem. I’ll come back to it. But I think we agree about the value of reason, and if we disagree about purported observations, we can talk about why.

But first, there is one more piece that is often folded into observation: inevitably, observations are interpreted within larger systems, even within a cosmology. Suddenly, vast spaces open up, cosmological  chasms that can hardly be crossed but must at least be faced. And I think that is where the first part of the problem lies: What credence should I give to a man who claims to be speaking science but is speaking cosmology?