Sciency Words: The Fermi Paradox

March 24, 2017

Today’s post is part of a special series here on Planet Pailly called Sciency Words. Each week, we take a closer look at an interesting science or science-related term to help us expand our scientific vocabularies together. Today’s term is:


Enrico Fermi was an Italian physicist, one of the many great scientists who immigrated to the United States right before the outbreak of World War II. He is most noted for creating the first nuclear reactor and the role he played in the development of the atomic bomb.

But that’s not what we’re going to talk about today. Today we’re talking about something Fermi said half-jokingly over lunch.

Where Is Everybody?

Based on some historical detective work, we can say this probably happened in the summer of 1950. Fermi was visiting the Los Alamos National Laboratory. He and a few colleagues were having a lunchtime conversation about flying saucers. Apparently there had been an amusing cartoon about little green men in a recent edition of the New Yorker.

The conversation got serious (sort of) when Fermi suddenly asked: “but where is everybody?” Everyone at the table laughed, but Fermi’s question and the not-entirely-serious discussion that followed would become the basis of what we now call the Fermi paradox.

As a matter of statistics and probability, it seems like advanced alien civilizations should be out there somewhere. There are over 100 billion stars in our galaxy. Many (if not most) of these stars have planets orbiting them. Some of these planets must surely support life, and in at least a few cases intelligent life—life capable of developing interstellar travel.

Even without faster-than-light technology, one or more of these space-faring civilizations could conceivably spread across the whole galaxy in just a few million years. The galaxy is far, far older than that. There’s been plenty of time for the aliens to do it. So where is everybody? Shouldn’t we have heard from somebody by now?

Or so Fermi argued over his club sandwich (or whatever he was eating) in a half-serious conversation about flying saucers. Of course there are plenty of objections to Fermi’s line of reasoning here, but I’m not going to weigh in on that. Not today. I’m saving my opinion for Monday’s post.

Sciency Words: Magnetar

March 17, 2017

Today’s post is part of a special series here on Planet Pailly called Sciency Words. Each week, we take a closer look at an interesting science or science-related term to help us expand our scientific vocabularies together. Today’s term is:


Space has a lot of cool ways to kill you. This one’s especially nifty! Magnetars are neutron stars with intensely powerful magnetic fields. Like, absurdly powerful magnetic fields.

Fly your spaceship near a magentar, and that overpowered magnetic field will start pulling the electrons off your atoms. This will kill you. It’ll destroy your spaceship too. Without those electrons, chemical bonds don’t work. Your molecules will unravel, and you and your ship will just disintegrate.

Even from a distance, magnetars are a menace. In 2004, a strong burst of gamma radiation washed over Earth, compressing our planet’s magnetic field and partially ionizing our atmosphere. That gamma radiation came from a magnetar on the other side of the galaxy.

If a magnetar could do that to us from so far away, just think what it must have done to any alien civilizations that happened to live closer. I can’t help but imagine there’s a vast dead zone on the other side of the galaxy, with magnetar SGR 1806-20 right in the middle.

The good news is that magnetars don’t last long. Their magnetic fields decay rapidly, so these raging monsters turn into regular neutron stars within a few thousand years. Also, while their outbursts of gamma rays and X-rays can affect our planet, there aren’t any magnetars close enough to Earth to really threaten us.

Oh wait. Yes there are. Sort of.

Sneezing in Space

March 15, 2017

So in case you were wondering: yes, astronauts do sometimes sneeze in their spacesuits. And no, there’s nothing they can do about it when it happens. The sneeze just splatters on the helmet’s faceplate.

I believe I first read about this in one of those Time Magazine specials I reviewed last year (click here or here).

The thing I really want to know is how the force of the sneeze affects the astronaut’s motion, especially when the astronaut is not wearing a helmet. For example, what happens when an astronaut is floating freely aboard the I.S.S. or some other spacecraft and suddenly sneezes?

I’d imagine the force of the sneeze could have some amusing propulsive effects in microgravity.

TRAPPIST-1: A Sky Full of Planets

March 13, 2017

Okay, one more post about TRAPPIST-1 and its seven planets, and then I promise I’ll move on to another topic. But this is something that’s just too awesome for me to skip.

You know that goofy trope you sometimes see in Sci-Fi movies or comic books? The one where the hero is standing on the surface of some alien planet and there are a whole bunch of other planets in the sky? Like, not just a moon or two, but a ton of huge planets looming over the horizon.

Well, apparently if you stood on the surface of one of the planets in the TRAPPIST-1 system, you’d be able to look up and see the other planets in the sky. Not just as tiny points of light but as large orbs.

The planets of TRAPPIST-1 are packed extremely close together, it seems. Several articles I’ve read, such as this one from Spaceflight 101, suggest that weather patterns and surface features would be visible to the naked eye.

I’m guessing the view would not be quite as epic as what I drew for the illustration above, but still… it would be stunning to see it. Just remember to bring proper radiation gear. TRAPPIST-1 is still a flare star.

Sciency Words: Ultra-Cool Dwarf Star

March 10, 2017

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Today’s post is part of a special series here on Planet Pailly called Sciency Words. Each week, we take a closer look at an interesting science or science-related term to help us expand our scientific vocabularies together. Today’s term is:


At some point, I want to profile each of the planets in the TRAPPIST-1 system one by one for my Exoplanet Explorer series. But it’s too early for that. Right now, we don’t know much about these planets except that they’re there.

But I can say something about TRAPPIST-1 itself. It’s a type of star called an ultra-cool dwarf star.


Apparently TRAPPIST-1 has just barely enough mass to cause hydrogen fusion in its core. That means that for a star, it doesn’t produce a whole lot of energy, and thus its temperature is relatively low. Based on my rough math and statistics I got from Wikipedia, it looks like TRAPPIST-1 is less than half the temperature of our Sun.

This is one of the things that makes TRAPPIST-1 so interesting to me, and why it’s really starting to capture my imagination. It’s not just about all those Earth-like planets. The star itself helps set a lower limit for just how small and cold stars can be.

TRAPPIST-1: A Mini-Solar System

March 8, 2017

Right now, TRAPPIST-1 is getting a ton of attention. If feels like just about every single telescope on Earth or in Earth-orbit has been stealing glances of this very tiny star and its seven Earth-like planets.


But we’ve discovered lots of other exoplanets, many of them Earth-like, and many of them in multi-planet systems. So why is TRAPPIST-1 getting so much special attention?

There Could Be Aliens!

Okay, yes. There could be aliens.

But I doubt it. TRAPPIST-1 is a flare star. We’ve met flare stars before. You don’t want to live near one.

Also, these planets are so close to their parent star that they are almost certainly tidally locked, with one side perpetually facing the sun and the other side perpetually turned away from it. Katy Perry could write a song about how hot and cold these planets must get.

Still, it’s not impossible for life to evolve under these conditions. Just don’t get your hopes up.

An Astrophysicist’s Dream Come True

There’s still a lot I haven’t read yet about TRAPPIST-1, and no doubt there’s even more information still to come. But at this point, I’m getting the impression that this miniaturized solar system is like an astrophysicist’s dream come true. Here’s why I think that:

  • From our vantage point here on Earth, these planets pass directly in front of their star (i.e.: they “transit” their sun). This is convenient for us. It’s a lot easier to collect data about transiting planets than non-transiting ones.
  • These planets are all very close to their parent star, and therefore they all have relatively short orbital periods. That means more transits and more opportunities to collect data.
  • There are so many planets so tightly packed together that it’s easy for us to study the gravitational interactions between them.
  • And again, because these planets have short orbital periods, these gravitational interactions are sort of accelerated compared to similar interactions in our own Solar System or in other star systems we’re currently observing. I imagine these interactions are also much stronger, since the planets are so much closer together.

TRAPPIST-1 is basically a mini-solar system running on fast-forward. We can collect loads of data about it in a matter of days or weeks, rather than years or decades, and use that data to refine our current theories about solar system dynamics.

That, I think, is the real reason TRAPPIST-1 and its seven planets are such a big deal. At least that’s what’s got me the most excited about them, and why I think we’ll be hearing a lot about the TRAPPIST-1 system for many years to come.

If we happen to discover alien life there as well, that’ll just be an added bonus.

Sciency Words: Earth Similarity Index

March 3, 2017

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Today’s post is part of a special series here on Planet Pailly called Sciency Words. Each week, we take a closer look at an interesting science or science-related term to help us expand our scientific vocabularies together. Today’s term is:


As I’m sure you’ve heard by now, astronomers have discovered seven planets orbiting a nearby star called TRAPPIST-1. Even more exciting, most or all of these new worlds are being described as Earth-like planets. But what does that actually mean?

You’d be surprised by how many “Earth-like” planets/moons we have right here in our own Solar System.

Ag16 Earth-like Worlds

From left to right: Venus, Earth, Mars, and Titan (Saturn’s largest moon).

Earth-like is a rather vaguely defined term. So in 2011, a paper published in the journal Astrobiology attempted to establish an official mathematical system for calculating just how Earth-like an exoplanet is. It’s called the Earth Similarity Index or E.S.I.

Basically, the E.S.I. takes certain characteristics of a planet that can be quantified—such as a planet’s mass, radius, temperature, etc—and compares them to Earth’s. An E.S.I. score of zero indicates a planet that has absolutely nothing in common with Earth, while an E.S.I. of one means the planet is an exact match for Earth… at least with regard to the characteristics being measured and included in our calculations.

Of course even a planet with an E.S.I. of one is not necessarily habitable, so the same Astrobiology paper also proposes a Potential Habitability Index or P.H.I. But that, I think, is a Sciency Word for another day.

P.S.: If you want to dive into the math behind the E.S.I., click here.