Hi! I'm Eric Korpela. You may know me from such blog posts as "Ewoks live under my deck" and "How Spock and Sylar are related." As part of my continuing series on what the heck scientists do, I'd like to talk about brains. You may ask, "What is it like in a scientist's brain?" Well, it's dark, it's moist, and it's as warm as Daytona in July.* Just like it is in yours.
The real answer is that I can't really tell you what's going on inside anyone's head but mine. For example, I look at my wife and think, "Why is she carrying all the groceries? And how can I make her do that again next time?" I really have no clue. That's because I've only been me.
The way my brain works now is pretty different from the way it worked when I was starting college, so I'm pretty sure that most of what I do is learned behavior. If so, maybe this scientist's brain will tell us something. Let's start with my thought processes for an everyday task like seeing an article on The Huffington Post -- for example, this one: "Venus May Be Slowing Down, New ESA Data Suggests."
Phase 1: WTF?
That makes absolutely no freaking sense! How can Venus be slowing down? It's in a periodic orbit, and we'd notice changes in the orbit without having to send a spacecraft there.
You may think that reaction is a little extreme, and maybe it is. Scientists have different expectations from a headline than editors do. A scientist might think a headline should provide enough information that you can decide whether you want to read an article. An editor knows the headline is there to make you want to read the article by not providing enough information.
Oh, its rotation is slowing... Maybe that could happen.
Phase 2: Skepticism
A 6-and-a-half-minute rotation period change... Are they sure their clock isn't just wrong? What would they have for a clock on a Venus orbiter? I'd use two temperature-controlled clocks with sync with a distance-adjusted time stream from Earth every 24 hours. That would definitely be better than 6.5 minutes, and the people who built the clocks for this orbiter thought about it for more than 30 seconds. I wonder how much they make? Do I remember this same issue happening with Magellan?
Skepticism is a very important phase. Without it a budding scientist could end up thinking that the guy in the next dorm room developed an amazing artificial intelligence program and still be embarrassed 26 years later about falling for that ruse.
Phase X: Getting Sidetracked
In a holographic universe, is information really conserved, or can the universe lie to us if there's no way we can check its answers?
Phase 3: Calculating
You can't have the rotation of Venus slowing without the rotational energy going somewhere. Where could it go? The obvious places are Mercury, the Earth, and the Moon. You'd need a gravitational torque on Venus. Is it really that lopsided? (That's what she said.) Note to self: check the Magellan gravity maps.
OK, Venus and Earth are about the same mass, and this change is small compared to the rotational energy of either, so the change in angular velocity would be inversely proportional to the angular velocity of Earth. That's a 2-millisecond change in the length of a day. Didn't happen.
Orbital energy. The earth's orbital kinetic energy is about 10,000 times its rotational energy, and that change in Venus's rotational energy was 1 billionth of that. The velocity change required would be unnoticeable, so there's probably some interaction due to the near resonance between Venus' rotation and Earth's orbit.
Could Venus have been slowing down this way for its entire history? Five billion years is 250 million times the 20 years this change took. That would give Venus a tenth the rotational energy of Earth, or a 72-hour day. Lots of assumptions there. It's probably more likely this is a periodic change as the rotation rate moves in and out of resonance with Earth's year. If we wait 20 years, I guess we'll find out.
Phase 4: Resignation:
I suppose I could read the whole article now.
Of course, there are things I left out: the internal monologue of caluclating in my head (which I am not at all good at, so please don't check my math), staring blankly into space, one or more additional episodes of getting sidetracked by random thoughts.
What does this say about my approach to science? First, my initial instinct to something new and unexpected is to try and figure out why it's wrong. When I'm asked to be a peer reviewer for a journal, I do the same thing. If I can't tell why it's wrong, maybe it's right.
I won't say I do that for articles that aren't unexpected, unless I'm reviewing it. If this article had said that Venus was rotating at exactly the same rate it did 20 years ago, I probably would have said "Yeah? So what?" and wouldn't have read it at all.
Second, when I go in, I'm going in armed. I don't want to be told what's happening; I want my own guesses as to what's going on, and I want to know what the physical limits of the problem are before I start reading. Maybe I'll still be surprised. Or maybe I'll find something they didn't think of. Think of it as a game.
What does this mean to you? Not much, probably. Your life probably isn't changed much by how you read a science article. But I do recommend skepticism to everyone, especially regarding money or your health, or anytime someone else has a lot to gain and you have a lot to lose.
I find it pretty compelling that in the climate science of today that we're up to a 97% consensus.
Earth solved that problem for itself by making lots of carbonate rocks and sequestering organic carbon as coal and oil. Tough to do without water and life. Venus also destroyed its initial water inventory, so there's probably not much hydrogen around to make water with. Terraforming Venus is probably a much tougher challenge.
What we need is wormhole technology to send Venus's atmosphere to Mars and some of Earth's water to both of them. That'll solve sea level rise, too.
So lets assume observation of missing six and a half minutes is correct, because waiting twenty years will either prove the observation is incorrect due to measurement error or it's...correct, and in that case...we wasted twenty years ignoring the puzzle. And there's no reason to expect a static rotation. After all, Earth and Moon aren't static, either.
Two unusual contrary actions are red flags: Venus moves retrograde and it's atmosphere moves retrograde to Venus. Venus isn't an ice planet. Instead, it's surface is course, irregular and likely can lose momentum over time (billions of years) with essentially unlimited renewable energy transferred somewhere (Venus).
Also, if as expected Venus has been slowing for 5 billion years, period time change would not appear linearly as suggested...it would be almost insignificant initially and only more noticeable at the end of 5 billion years with much less angular momentum.
Arecibo has some great radar images at http://www.naic.edu/~pradar/radarpage.html
But then, walking or running at 4mph in an atmosphere with about 10% of the density of water might actually be quite strenuous...
And the control room is amazing too, in that, it's a relic right out of the 60's; it's my new link reference, when attempting to persuade people manned exploration leaches too much funds from legitimate science.
Didn't realize and was pleasantly surprised (but then, not surprised because researchers are reasonable people) anyone who can successfully navigate the proposal process can compete with master, doctoral candidates and professionals for consideration. Now I'm wondering, if in addition to published results...proposals can be viewed on-line as well?
OK... I admit... I fell into the same trap for the first few minutes of reasoning... and I still don't know what the answer is... :-)
I do love the description of the reasoning process, though. That's spot on!
I have to admit that a change of moment of inertia didn't even cross my mind. The way Venus resurfaces itself every billion years or so could change the moment of inertia. That should show up in atmospheric composition, I would think.
I wish Venus Express had the SAR capabilities the Magellan had.
The interesting thing is that the atmosphere can actually absorb an amazingly large fraction of the planet's angular momentum. I was very surprised by that... Where a back of the envelope calculation runs into trouble is that shear forces are not enough to explain the required coupling... which basically means that the planet's atmosphere might rotate almost freely! I find that quite amazing, too.
"I have to admit that a change of moment of inertia didn't even cross my mind. The way Venus resurfaces itself every billion years or so could change the moment of inertia. That should show up in atmospheric composition, I would think."
My problem with that was that it would take about 100m of elevation difference over the whole planet or continent size chunks of crust rising by a km to accomplish that... I don't think anything close to that was observed by radar measurements.
I am kind of left with the coupling between a differentially rotating core and the mantle/crust... but I simply can't back that up with a simple back of the envelope.
It's a fun problem and might make a really good homework question in classical mechanics.