Quote of the Day - 15 July 2005

| 10 Comments

The totality of life, known as the biosphere to scientists and creation to theologians, is a membrane of organisms wrapped around the earth so thin that it cannot be seen edgewise from a spacce shuttle, yet so internally complex that most species composing it remain undiscovered. –E.O. Wilson The Future of Life (2002)

10 Comments

A low orbit for the Space Shuttle is 300 km above the surface. The biosphere is 10 km or so. Sorry, Dr. Wilson. The spirit of what you say is true, but the letter is not: the biosphere can be seen edgewise from a space shuttle.

I wouldn’t doubt that the astronauts can see a 10 kilometer high terrain feature, but I would doubt that they can see any indications of the biosphere ON that terrain feature. At those distances, the biosphere coats the corrugations of the terrain like a thin film.

That being said, I understand that certain features of the biosphere CAN be visualized, particularly man-made ones–flares from gas wells at night, city illumination at night, lakes backed up by linear features that must be dams, the green color of jungle, forests, and fields, large planktonic discolorations in the ocean, etc.

But most of these aren’t usually visualized from an edge-on perspective, so…

re: orbit of shuttle

The number Mr. Hopkins quotes forgets to account for the radius of the earth. So the correct comparison is just under 6700km to 10km. Simple trig puts that in the neighborhood of 1/12 of a degree, assuming this calculator works properly. IIRC, puts it at the edge of human acuity, but visible at that orbit. After checking, someone with 20/30 vision would just be able to discern the biosphere edge-on at low earth orbit.

Oops, my math was off a bit (didn’t draw my diagram correctly). The tangential distance at that orbit is a bit under 2200km. So a 10km biosphere would be closer to 1/4 of a degree at that orbit. Definitely visible, even to someone with 20/200 vision.

Facts are meaningless. You could use facts to prove anything that’s even remotely true!

I wouldn’t doubt that the astronauts can see a 10 kilometer high terrain feature, but I would doubt that they can see any indications of the biosphere ON that terrain feature. At those distances, the biosphere coats the corrugations of the terrain like a thin film.

That being said, I understand that certain features of the biosphere CAN be visualized, particularly man-made ones–flares from gas wells at night, city illumination at night, lakes backed up by linear features that must be dams, the green color of jungle, forests, and fields, large planktonic discolorations in the ocean, etc.

Actually, the view of earth from low orbit is not as featureless as one might expect. I’ve been told by astronauts that they were able to see such things as the wakes of large freighters in the ocean, and individual mountain peaks in ranges. They can even pick out the launch complexes at Kennedy Space Center while passing over Florida.

As John Glenn told me, the view from space isn’t very much different than the view from a high-altitute jet fighter-interceptor.

I think that most people, when they think of “the view of earth from space”, have in mind that famous shot of the earth taken from the moon by the Apollo teams, in whcih the earth is just a swirl of blue, white and brown. Low earth orbit is much much much closer.

Oh, yeah, Lenny, I agree (agreed?), I think, that you can see a lot from shuttle orbit, in the Nat. Geo. cover shot, two-dimensional pizza-toppings spread on the earth’s platter, sense.

But I think the concept we were playing with was the visibility of the “thickness” of the biosphere–

“a membrane of organisms wrapped around the earth so thin that it cannot be seen edgewise from a space shuttle”

–so we’re not talking (at least as I interpreted this image) about the two-dimensional or horizontal “spread” of the biosphere, but rather of the biosphere’s third or vertical extension.

The suggestion was then made that the biosphere was 10 km “thick” (vertical measurement, from top to bottom). Assuming we’re only talking about what’s visible (and not about the ocean’s depths or whatever microfauna may dwell deep below the crust of the earth), I took that poster to be referring to the depth or height of the surface terrain features over which the biosphere is spread. I took mild exception to that estimate, because while the surface terrain may vary by that much, the biosphere itself is spread rather thinly over that terrain.

So the question then became, in my pointy little brain, how “thick” is the biosphere “above” any particular chunk of terrain, irrespective of the height of the terrain feature itself?

There’s room for debate, depending on definition (and, unlike some of the other debates going on the other threads, this one is just for fun, I hope)–you could include everything from sea level to the heights reached by the geese that migrate over the Himalayas. You could include the rarer, higher visitations of lifeforms, like U2 overflights, the recent “edge of space” flights, heck, the space shuttle and space station themselves.

But in terms of a “visible” biosphere, it makes more sense to me to think in terms of tall trees, maybe skyscrapers. You’re not going to see birds, bats, or butterflies in mid-flight from LEO. Even if you throw those in, the typical flight-height above the nearest terrain is NOT going to be the height of the Himalayas, but the few hundred feet by which the geese CLEAR the Himalayas.

So I would argue that the “height” of the biosphere is a few hundred feet. That few hundred feet arguably is NOT going to be visible “edgewise” from LEO, though the height of the terrain on which that thin living membrane is spread might be.

All of which brings us to “edge-on.” I think I agree with a corollary of one of your points here–the shuttle can NEVER really get an “edge on” view: it’s always going to be suspended over mid-platter, and one have no way to acquire good visualization of the “thickness” of the biosphere (however we define that and whatever number of meters or kilometers we assign) because that view is only visible at the very horizon line, or as the soap opera would have it, As the Biosphere Turns.

W. Kevin Vicklund Wrote:

re: orbit of shuttle

The number Mr. Hopkins quotes forgets to account for the radius of the earth. So the correct comparison is just under 6700km to 10km. Simple trig puts that in the neighborhood of 1/12 of a degree, assuming this calculator works properly. IIRC, puts it at the edge of human acuity, but visible at that orbit. After checking, someone with 20/30 vision would just be able to discern the biosphere edge-on at low earth orbit.

Mr. Vicklung forget to account that the radius of the Earth is irrelevent. Indeed it is NEVER relevant to the calculation. The biosphere is part of the observable universe as well, but he did not cite it for some reason. We don’t care about the entire earth for the same reason we don’t care (for the purposes of this calculation) what the size of the universe is. The angle in question comes ONLY from the width of the item being observed (10 km) and how far away the observer is (300 km). That is easily visible.

Indeed you can’t even see the whole of the Earth from a Shuttle’s orbit anyways. Consider that Mr. Vicklung is currently 95.5% of the distance from the center of the earth to a low shuttle orbit (300 km). Shuttles fly VERY close to the Earth all things considered.

I also refer people to Lenny’s post. Things far smaller than the biosphere can be seen from the Shuttle orbit.

Of course what Dr. Wilson and Mr. Vicklung are thinking of is seeing the biosphere from the Moon which is over a thousand times more distant than a shuttle in a low orbit.

Mr. Vicklung forget to account that the radius of the Earth is irrelevent. Indeed it is NEVER relevant to the calculation. The biosphere is part of the observable universe as well, but he did not cite it for some reason. We don’t care about the entire earth for the same reason we don’t care (for the purposes of this calculation) what the size of the universe is. The angle in question comes ONLY from the width of the item being observed (10 km) and how far away the observer is (300 km). That is easily visible.

Bear in mind, 300 km is the height of the shuttle above the ground directly below it. For a meaningful calculation of how thick the biosphere would look at the horizon (for an “edge on” view), you have use the distance of the shuttle from its horizon. And for that, you do need to take the radius of Earth into account.

The equation looks like this:

r^2 + d^2 = (r + h)^2

where r is the radius of Earth, d is the distance from the shuttle to the horizon as seen from the shuttle, and h is the height of the shuttle above the ground.

Solving for d and simplifying:

d = sqrt( h^2 + 2hr )

If h = 300 km and r = 6378 km (taken from Google) then d = 1980 km

At that distance, something 10 km wide (w) would be

a = 2 * atan( w / 2d )

a = 0.29 degrees

Which is what W. Kevin Vicklund said.

Walter Brameld IV Wrote:

Bear in mind, 300 km is the height of the shuttle above the ground directly below it. For a meaningful calculation of how thick the biosphere would look at the horizon (for an “edge on” view), you have use the distance of the shuttle from its horizon. And for that, you do need to take the radius of Earth into account.

Thank you, this was the set of equations I was using (though your numbers are more accurate, of course). The definition of 20/200 vision is being able to discern an object that is 10 arc-minutes wide. 0.29 degrees is equal to 17.4 arc-minutes, so even humans with terrible eyesight should be able to detect the “biosphere.” The reason for the scare quotes? The biosphere is not of uniform thickness - to the best of my knowledge it never fills in the full 10km column. Also, the individual features of the biosphere are never 10km high. So unless we can make the entire biosphere observable (say by a filter over the shuttle windows that marked the biosphere as scarlet red), the 10km figure is misleading.

However, there is a potential flaw in using the equation. We haven’t demonstrated that viewing perpendicular to the plane of the edge produces the greatest a (as defined in the referrenced post) - assuming we are not restricted to viewing the horizon (ie, we can create slices). We know that when viewed from directly above, a = 0 degrees, and that if the angle of reference becomes obtuse, a decreases from that calculated above. But it is possible that the maximum value of a comes at a slice taken between vertical and the horizon. It’s too late for me (the wife wants to go to bed), but it might be interesting to figure out the optimum slice angle. Was that at all clear? Probably not.

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This page contains a single entry by Mike Dunford published on July 15, 2005 12:05 PM.

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