Is There Life on Earth?

Hello, friends!

Let’s imagine some space aliens are cruising by our Solar System.  They turn their scanners on our planet and see… what?

Among other things, they’d notice that Earth’s landmasses are partially covered with a strange, green-colored substance.  Of course, you and I know what that green substance is.  It’s chlorophyll.  But would those extraterrestrial observers, who have no prior knowledge of our planet, be able to figure that out?  Even if they did, would they realize what chlorophyll is used for?  Maybe.  Probably not, though.

Which brings me to my all-time favorite scientific paper: “A search for life on Earth from the Galileo spacecraft,” by Carl Sagan et al.  I love this paper in part because it’s so clearly and concisely written, with jargon kept to a minimum.  Sagan was, after all, a talented science communicator.  But I also love this paper because its conclusions are so shocking, so eye-opening.

In 1990, NASA’s Galileo spacecraft turned all its high-tech instruments toward Earth and detected… not much, actually.  Galileo did pick up radio broadcasts emanating from the planet’s surface.  Aside from that, though, Galileo’s data offered highly suggestive (but also highly circumstantial) evidence on Earthly life.  The lesson: finding life on other planets is hard.  Even using our very best equipment, it was hard for NASA to detect signs of life right here on Earth!

At least that’s what I got out of reading Sagan’s Galileo experiment paper.  And based on various commentaries I’ve read or heard about this paper, that seems to be the lesson other people got out of it too.  So I was surprised to hear Sagan himself, approximately seven-and-a-half minutes into this interview, saying the exact opposite.

We’ve flown by some sixty worlds.  We claim that we haven’t found life anywhere, and that that is a significant result.  That is, that we would have found life had it been there.  But this has never been calibrated.  We’ve never flown by the Earth with a modern interplanetary spacecraft, all instruments on, and detected life here.  And so Galileo, because of this peculiar gravity assist VEEGA trajectory, permits us to do that.  And as I’ll describe tomorrow, we find life five or six different ways, including intelligent life.  And this then means that the negative results that we find elsewhere are, in fact, significant.

I’ve been puzzled by this for a while now, but I think I’ve finally figured out why Sagan would say this.  It’s politics.

On the one hand, scientists need to understand the challenges they’ll face (including the limitations of their own equipment) in searching for life on other worlds.  That really is, I think, the purpose of the Galileo experiment paper.  On the other hand, it would not do to say on public television, to cantankerous taxpayers and the listening ears of Congress, that NASA spends millions of dollars on space probes that are not even capable of detecting life right here on Earth.

Space exploration is expensive.  And like all expensive types of research, sooner or later the researchers involved have to learn how to play politics.

What Color are All the Planets?

Hello, friends!

So as you know, Earth is “the Blue Planet” and Mars is “the Red Planet.”  By my math, that leaves us with six other planets in our Solar System that don’t have color-related nicknames.  Today, I’d like to try and fix that.

Jupiter was the toughest.  He’s actually lots of different colors: red, grey, white, orange… and then the Juno mission recently showed us that Jupiter’s polar regions are blue!  Of course Jupiter is most famous for being red in that one specific spot, but even the Great Red Spot changes colors from time to time, fading from red to pink to white before turning red again.

Anyway, those are my picks for the color-related nicknames for all the planets.  Do you agree with my picks?  Disagree?  Let me know in the comments below!

Sciency Words: Aerobiology

Hello, friends!  Welcome to Sciency Words, a special series here on Planet Pailly where we talk about those weird and wonderful words scientists like to use.  Today on Sciency Words, we’re talking about:

AEROBIOLOGY

You will find life pretty much anywhere you go on Earth.  Living things are in the water, on the land, and up in the air.

Aerobiology comes from three Greek words meaning “air,” “life,” and “the study of.”  So aerobiology is the study of airborne life, specifically airborne microbial life.  According to the Oxford English Dictionary, the term was first introduced in the late 1930’s.

I have to confess I am totally new to aerobiology.  I only found out about this term yesterday, and I don’t want anything I say to misrepresent the field.  But based on what I have read, it sounds like aerobiologists are primarily concerned with protecting public health from the spread of pollen and other allergens, as well as the spread of airborne diseases.

However, aerobiologists also study airborne microbes that are not a direct threat to human health—and this is the part that connects to the outer space stuff I normally write about.  For decades now, aerobiologists have known that algae and other common microorganisms can fly up into Earth’s atmosphere and travel great distances on the wind.  And according to this 2001 paper, microorganisms can (and do) remain active—growing and reproducing—inside the water droplets found in clouds.  As the authors of that 2001 paper explain it, we should start thinking of clouds as microbial habitats.

So what does this have to do with outer space?  Well, if clouds on Earth can serve as a habitat for microorganisms, then maybe microorganisms could exist in the clouds of some other planet.

And by some other planet, I mean Venus.

And by maybe, I mean stay tuned for Monday’s post.

Science is Wrong About Everything

Hello, friends!  So one day when I was a little kid, I got into a huge argument with another kid in school.  I’d said something about how Earth is a sphere, like all the other planets.  The other kid told me (firstly) that Star Trek isn’t real and (secondly) that the earth is flat.

As evidence, the other kid told me to just look around.  It’s obvious that the world is flat.  If I needed more proof, I could look at a map.  More kids soon jumped into this argument.  They all agreed: the earth is flat, and also I’m a huge nerd for watching so much Star Trek.  I was outnumbered, and being outnumbered was further proof that I must be wrong.

I went home so mad that day.  How could those other kids be so stupid?  I was right.  Everybody else was wrong.  I’m tempted to turn this into a metaphor for Internet culture, but that’s not the point I want to make today.

Yes, when those other kids said the Earth is flat, they were wrong.  But when I said the Earth is a sphere, I was wrong too.  Less wrong, obviously.  But still, I was wrong.

Isaac Asimov’s essay “The Relativity of Wrong” is a brilliant summation of how science works.  It should be required reading for every human being (click here to read it).  As Asimov explains:

[…] when people thought the earth was flat, they were wrong.  When people thought the earth was spherical, they were wrong.  But if you think that thinking the earth is spherical is just as wrong as thinking the earth is flat, then your view is wronger than both of them put together.

As Asimov goes on to explain, there was a time, long ago, when educated people really did believe the world was flat, and they had good reasons for thinking it to be so.  But then discoveries were made.  New knowledge was learned, and people came to think of the world was a sphere.  Then more discoveries were made, and people started to think of the world as an oblate spheroid (round, but slightly bulgy at the equator).  And then still more discoveries were made, and even the oblate spheroid model turned out to be slightly inaccurate.

People (including people on the Internet) will gleefully point out that science has been wrong about stuff in the past; therefore, science could be wrong about stuff today—stuff like evolution, climate change, general relativity—also stuff like vaccinations and COVID-19.  When science is wrong so much, why pay attention to science at all?

Well, it’s true.  In absolutist (this-or-that-ist) terms, science is wrong.  Science is always wrong, about everything, all the time.  Science is full of educated guesses and close approximations of observed reality.  It’s not perfect.  It will never be perfect.  But with each new discovery, science is a little less wrong today than it was yesterday.  And you can trust science to keep being less and less wrong, even if it will never be 100% right.

And that process of constant refinement and improvement, that process of getting closer and closer to the truth—that’s something worth paying attention to, something worth taking seriously, don’t you think?

P.S.: I’ll concede that those kids in school were right about one thing.  I was, and still am, a huge Star Trek nerd.

Sciency Words: Syzygy

Hello, friends!  Welcome to Sciency Words, a special series here on Planet Pailly where we take a closer look at the definitions and etymologies of scientific terms.  Today on Sciency Words, we’re talking about the word:

SYZYGY

We’ve all seen pictures like this, with all eight planets lined up in a row:

And sometimes, on extra special occasions, the planets really do line up like that, or at least they come very close to it.  When this happens, we call it a grand syzygy.

The word syzygy traces back to ancient Greek.  It originally meant “yoked together,” as in: “The farmer yoked together his oxen before plowing the field.”  According to my trusty dictionary of classical Greek, the word could also mean “pair” or “union.”

Some closely related words in Greek referred to balance, teamwork, sexy times, etc.  And our modern English words synergy and synchronized have similar etymologies.  Basically, what all these words have in common is a sense of people or things coming together, in one manner or another.

For modern astronomers, syzygy means three or more celestial bodies coming together to form a straight line.  The most commonly cited example of this is the alignment of the Sun, Earth, and Moon that occurs during either a new moon or full moon, as observed here on Earth.

But an alignment doesn’t have to be perfectly straight to be called a syzygy, especially when we’re dealing with more than three objects.  According to this article from The New York Times, a syzygy of the Sun, Venus, Earth, Mars, Jupiter, and Saturn occured between March 25 and April 7, 1981.  The Sun and five planets came “within 2 degree of arc from a perfect straight line.”  Apparently that’s close enough.

But while that 1981 syzygy was pretty grand, it was not the grandest of grand syzygies.  The planets Mercury, Uranus, and Neptune were left out.  According to another article from The News York Times, a truly grand syzygy will happen on May 19, 2161, “[…] when eight planets (excluding Pluto) will be found within 69 degrees of each other […].”

So mark your calendars, friends!  You don’t want to miss the grand syzygy of 2161!

P.S.: And if you’re a Star Trek fan, you may recall that 2161 will be an auspicious year for another reason.  That’s the year when the United Federation of Planets will be founded—a political syzygy, one might say, occurring at the same time as an astronomical syzygy.

Sciency Words: Supermoon

Hello, friends!  Welcome to Sciency Words, a special series here on Planet Pailly where we talk about the definitions and etymologies of science or science-related terms.  Today’s Sciency Word is:

SUPERMOON

I was recently part of a comment thread over on Scott’s Sky Watch.  We were talking about the term supermoon, along with other weird moon names like wolf moon, blood moon, harvest moon, corndog moon, flower power moon, gingivitis moon… you get the idea.  After that, I thought a Sciency Words post on “supermoon” was in order.

The term supermoon was coined by American astrologer (repeat: astrologer, not astronomer) Richard Nolle.  The term first appeared in an article Nolle wrote in 1979 for Horoscope magazine.  To quote Nolle himself from this 2011 webpage article, the term supermoon describes:

[…] a new or full moon which occurs with the Moon at or near (within 90% of) its closest approach to Earth in a given orbit.  In short, Earth, Moon and Sun are in a line, with Moon in its nearest approach to Earth.

This particular alignment of the Sun, Moon, and Earth is also known as a syzygy-perigee.  Perigee means the point when as object orbiting Earth comes closest to Earth, and syzygy refers to the straight line alignment of three celestial objects.

A syzygy-perigee has a marginal effect on Earth’s tides, and if the Sun and Moon are on opposite sides of the Earth (as depicted in the highly technical diagram below), then the Moon will appear to be slightly larger and slightly brighter than normal in our night sky.  Astrologers would have more to say about supermoons, but from an astronomy perspective we’re pretty much done here.

Personally, I don’t really have a problem with the term supermoon.  When the full moon or new moon happens to be 90% closer to Earth than usual, that’s kind of neat.  Sure, the term started as an astrology thing, but there’s a long history of astrology concepts and terminology being borrowed by astronomers.  Supermoon is no different.

And supermoons do tend to get a lot of attention in the popular press.  I’ve had a lot of awesome conversations with people about the Moon and space and science in general that started because of a news report about the latest supermoon.  I think that’s great.  Anything that gets people to take an interest in science is a positive thing in my book.

On the other hand, a few of those conversations have ended with people asking me about their horoscopes, which is a bit disappointing.

Next time on Planet Pailly, please don’t hate anybody, not even the people who deserve it.

Sciency Words: The Yarkovsky Effect

Hello, friends!  Welcome to Sciency Words, a special series here on Planet Pailly where we talk about those weird and wonderful words scientists use.  Today on Sciency Words, we’re talking about:

THE YARKOVSKY EFFECT

Have you ever tried to count all the stars in the night sky?  Well, that might be an easier job than finding and tracking all the asteroids that keep whizzing by our planet.  Part of the problem is due to something called the Yarkovsky Effect.

Ivan Yarkovsky was a Polish engineer working in Russia.  He was also a huge science enthusiast.  If Yarkovsky were alive today, I imagine he’d be writing a blog about all the cool sciency research he was doing in his free time.

But it was the late 19th/early 20th Century.  Blogging wasn’t an option, so instead Yarkovsky wrote pamphlets about science, which he circulated among his science enthusiast friends. And almost fifty years after Yarkovsky’s death, an Estonian astronomer by the name of Ernst Öpik would remember reading one of those pamphlets.

Imagine an asteroid orbiting the Sun.  Sunlight causes this asteroid’s surface to get hot.  Then, as the asteroid rotates, that heat energy radiates off into space.  Would this radiating heat produce any thrust?  Would there be enough thrust to push an asteroid off its orbital trajectory?

Öpik thought so, and in 1951 he wrote this paper introducing the idea to the broader scientific community.  Today’s Sciency Words post would probably have been about the “Öpik Effect,” except Ernst Öpik was kind enough to give credit to the obscure blogger pamphlet writer who originally came up with the concept.  Thus we have the Yarkovsky Effect.

And in 2003, radar observations of the asteroid 6489 Golevka confirmed that the Yarkovsky Effect is real!  The asteroid had wandered 15 km away from its original course!

Around the same time, a copy of Ivan Yarkovsky’s original pamphlet was found in Poland.  As described in this article, it seems Yarkovsky was working on the basis of some faulty premises and a few rather unscientific assumptions.  He more or less stumbled upon the right idea by accident (but let’s not dwell on that part of the story).

Next time on Planet Pailly, no one’s going to name a scientific theory after me, but maybe there’s another sciency honor I can aspire to.

Sciency Words: Superhabitable

Hello, friends!  Welcome to Sciency Words, a special series here on Planet Pailly where we talk about the meaning and origin of scientific terms.  Today’s sciency word is:

SUPERHABITABLE

The word “habitable” traces all the way back to ancient Latin.  Think of a residence or dwelling.  Think of tenants and landlords and the act of paying rent.  That’s the sort of thing words like habitabilis, habitator, or habitatio referred to.

Of course when we talk about planets, the meaning of “habitable” and “habitability” is a bit different.  Unless…

In our ongoing search for extraterrestrial life, it’s generally assumed that Earth is typical of habitable planets.  But why should we assume that?

In this 2014 paper, physicists René Heller and John Armstrong claim that Earth is not as perfectly suited for life as it seems.  In some ways, Earth is kind of a dangerous place to live, and there have been several instances where life on Earth nearly got snuffed out.  Heller and Armstrong then go on to argue that other worlds may “offer more benign environments to life than Earth does.”

If we insist on calling Earth “habitable,” then Heller and Armstrong propose calling those other worlds “superhabitable.”  Though really, if we’d stop being so geocentric and anthropocentric in our terminology, it is the “superhabitable” planets that should set the standard for habitability, and Earth would be better described as “marginally habitable.”

So what sort of planet would offer a more benign environment for life than Earth does?  Well, according to Heller and Armstrong, planets that are two to three times as massive as Earth would do nicely.  More massive planets will remain geologically active for longer, and they’ll have stronger magnetic fields to protect life from solar and cosmic radiation.  Shallower oceans and a thicker atmosphere would help too.

A smaller and cooler star would also be preferable.  A K-type “orange dwarf” would spew out less harmful radiation than our own G-type Sun, and K-type stars last longer.  A whole lot longer.  No need to worry about the day the sun dies if your planet orbits a K-type star!

Personally, I feel like Heller and Armstrong are making a lot of big assumptions in describing their superhabitable planets.  There may be some wishful thinking at work here.  But then again, it’s also a pretty big assumption to assume that Earth is a typical example of a habitable world.  There’s probably some wishful thinking at work there too.

Next time on Planet Pailly, the nearest superhabitable planet could be a lot closer than you think (unless you clicked that link above, in which case you probably know where Heller and Armstrong said the nearest superhabitable planet might be).

Sciency Words: Barycenter

Hello, friends!  Welcome to Sciency Words, a special series here on Planet Pailly where we talk about those big, complicated words scientists use.  Today’s Sciency Word is:

BARYCENTER

Excuse me, but I’m going to do that “um, actually” thing that people who think they’re really smart like to do.  Now you may think the Earth orbits around the Sun.  Um, actually… the Earth and Sun both orbit something called the barycenter.

The word barycenter comes from two Greek words meaning “heavy” and “center,” and it refers to the common center of mass for two or more celestial bodies.  Based on sources I found via Google Ngrams, the term started appearing frequently in astronomical journals during the early 20th Century, and it may have been in use as early as the 1880’s.

Let’s say you have two celestial bodies.  One is really massive, the other is much less massive.  In that case, the barycenter will probably be located somewhere inside the more massive object.  This is the case for the Earth and her Moon.  Based on numbers I got from Wikipedia, the Earth-Moon barycenter is about 1000 miles (1700 km) beneath Earth’s surface.  Or to measure that a different way, the barycenter is about 3000 miles (4600 km) away from the center of the Earth.

Now let’s say you have two celestial bodies of roughly equal mass.  In that case, the barycenter will be located somewhere between them.  Something like this has happened with Pluto and his giant moon, Charon.  Once more using numbers from Wikipedia, it looks like the Pluto-Charon barycenter is about 500 miles (960 km) ABOVE the surface of Pluto.

As for the Earth-Sun barycenter, it’s located deep inside the Sun.  So if you say Earth orbits the Sun, you’re not too far from the truth.  But of course Earth is not the only planet in the Solar System, and when you consider the Solar System as a whole, you’ll find the Sun wibbles and wobbles about in weird, loopy patterns.  As you can see in the highly technical diagram below, the Sun wibbles and wobbles so much it can wobble into a totally new position in just a few years.

Click here for an actual diagram of the Sun’s movement relative to the Solar System’s barycenter.

As explained in this paper, this is mainly due to the gravitational influences of Jupiter and Saturn. Over longer time scales (centuries rather than decades), the subtler influences of Uranus and Neptune also have a noticeable effect.

So the next time someone tells you the Earth orbits the Sun, you can do the “um, actually” thing and explain what a barycenter is.  Trust me, it’s a great way to sound smart and make lots of new friends!

Next time on Planet Pailly, what did people in 1962 think we’d find on other planets?

Sciency Words: Love Numbers

Sciency Words: (proper noun) a special series here on Planet Pailly focusing on the definitions and etymologies of science or science-related terms.  Today’s Sciency Word is:

LOVE NUMBERS

My friends, I was recently doing research about the planet Neptune.  Astronomers have a new model for the Neptune system, a model that seems to do a better job predicting the orbits of all those unruly and rambunctious Neptunian moons.  While reading about this new model, I came across the following statement: “We also investigated sensitivity of the fit to Neptune’s Love number […].”  And that gave me a delightful mental picture:

“Love numbers” are named after English mathematician Augustus Edward Hough Love.  They’re also sometimes referred to as “Love and Shida numbers” to recognize the contribution of Japanese scientist T. Shida.

In the early 20th Century, Love introduced two ratios—traditionally represented by the variables h and kh has to do with the elasticity (stretchiness) of a planetary body, and k is related to the redistribution of mass within a planetary body as it stretches.  Shortly thereafter, Shida introduced a third ratio—represented by the variable l—involving the horizontal displacement of a planetary crust.

Taken together, h, k, and l tell you how much a planet, moon, or other celestial body can flex due to tidal forces.  As explained in this paper on Earth’s Love numbers:

If the Earth would be a completely rigid body, [its Love numbers] would be equal to zero, and there would be no tidal deformation of the surface.

But of course Earth is not a completely rigid body.  Tidal forces caused by the Sun and Moon cause Earth to flex “up to tens of centimeters,” according to that same paper.  Tens of centimeters doesn’t sound like much, but as we all know, it’s enough to keep the ocean tides going!

In conclusion, I guess you might say that what’s true for planets is also true for people.  Being completely rigid produces Love numbers equal to zero.  So be flexible.  Allow yourself to stretch a little, and your Love numbers will go up.

P.S.: Being flexible is healthy in any relationship, but at the same time don’t let others tug on you too hard.  Know your limits—your Roche limit, I mean—because you don’t want to end up like this: