Where can we actually go (now or in the near future)?
While there are certainly some fantastic science fiction stories set on Earth, I personally am always fascinated by stories of people (and aliens) visiting all kinds of interesting planets. In some stories the protagonist visits dozens of planets, seeing all kinds of amazing environments. So cool.
But what would it actually take to travel in space? Can we do it? And if not, could we one day? These are the questions I want to address (at least in brief) in this short blog series.
The Universal Speed Limit
Before we get started, it is key to mention that physics has found a limit on the fastest speed anything, spaceship, person, or bug-eyed alien, can travel. This is known as the speed of light (and yes, this is how fast light travels). This is a key component of Einstein's theory of relativity. The speed of light comes to an amazing 670 miles per hour. So light is incredibly fast.
That said, things in space are incredibly far apart. So even at the speed of light, it takes a while to get places. A lot of distances are reported in light years (or how many years it takes light to travel that far). So something 10 light years away takes at least 10 years to get to.
I'll talk in the next blog about possibly ways to circumvent this speed limit, like wormholes, but for the rest of this post I'll assume that we're limited by this universal speed limit.
One of the big topics in space news lately has been talk of sending people to Mars. Now, if you aren't too invested in conspiracy theories, we've already been able to send people to the moon. Mars is (depending on orbital alignment), roughly 1,000 times farther away than the moon, so this is a huge undertaking. That said, there is obviously a lot of reason to believe this will succeed. We've sent a number of probes to Mars already and we know how to get people in space. Put all that together and a trip to Mars can absolutely happen.
I'm not going to belabor this topic since millions of websites are rich in details about traveling to Mars. I just want to point out a few things before moving on.
'Interstellar' just means 'between stars.' So here I'm talking about traveling between stars. Now this gets much more interesting. Many instruments, most famously NASA's Kepler satellite, have found planets orbiting other stars in the Milky Way. As of now, it really looks like most stars are surrounded by planets. So interstellar travel means visiting planets unlike any we've ever seen, maybe even some with other forms of life. Amazing for human curiosity and great grounds for science fiction.
There's a lot we could say about this, but I'm going to focus now on whether we could make it to another star system.
The short answer... yes (probably), but not any time soon.
Now the long answer:
First, what are the distances involved? The nearest star to us is Alpha Centauri at just over 4 light years. Others are farther still, but we have over 40 stars within 15 light years. Plenty to choose from.
A light year is about 5.9 trillion miles! This is a really, really long way roughly 40,000 times farther than the distance to Mars. So if we say we could get to Mars in 100 days, we'd be looking at something like 4 million days (11,000 years) to get there. Hmmm so...
Okay, that sounds bad, but there's more to the story. If we could produce a sustained acceleration of one gee (9.8 meters per square second), a ship would keep speeding up the farther the trip got. This means we could make it there faster.
If we accelerated for the first half of the trip and decelerated for the second half, we could reach Alpha Centauri somewhere between 4 and 10 years! That doesn't sound too bad at all. (I'm being cagey because I haven't run the full relativistic calculation, which we'd need for a precise answer). Even if we slowed down the acceleration, a trip of 50-100 years seems possible. That's more or less within a human lifetime. (I'll get to how humans could survive such a trip in the third blog post.)
Now actually keeping up one gee of acceleration for several years straight is well beyond what we could do now. I haven't checked numbers, but the amount of chemical fuel required would likely be near to impossible to obtain. Maybe we'd get closer with nuclear fuel, but still, a tough proposition. I'll talk more about the possible technology to actually make such a trip in the next blog post so stay tuned.
One thing worth bringing up is a proposed project called Starshot. This is a probe that could travel to Alpha Centauri in as little as 20 years. Definitely a critical first step to sending people. Now the technology (lasers on Earth pushing a very tiny spaceship), wouldn't scale up easily to a manned spacecraft, but it shows that the nearby stars may not stay beyond our reach for long.
Just as interstellar means between stars, intergalactic means between galaxies. Now a galaxy is a collection of billions of stars, so these things are huge. The Milky Way is our home galaxy and it is a long way across. The stars like Alpha Centauri are our closest neighbors within the Milky Way and those are hard to get to. Crossing the Milky Way galaxy itself is well beyond our reach.
Getting to a different galaxy is, right now, as close to impossible as anything.
The nearest galaxy to us (excluding small dwarf galaxies) is Andromeda (M31) and it is 2.5 million light years away. That is nearly 1 million times farther away than Alpha Centauri, and such a ridiculous number of miles we can't even imagine it. And that is just the closest galaxy.
At this point we don't have a hint of any technology we could use to make the trip. I will mention a few of the more far out travel ideas in the second blog, but suffice to say this kind of trip is in our distant future or beyond.
So what is realistic?
Now, I think there's no need to confine fiction to the realistic. Some of the greatest science fiction stories and movies throw any realism to the wind. However, if we do want to consider what we could actually do, here's the quick summary.
Many of us are drawn to science fiction because of the exploration of new frontiers and mind-bending concepts. But let’s all be honest, most of us are a little disappointed if there aren’t a few aliens in there too. Given that, what can a scientific perspective say about aliens? Is there any truth behind some of the radical movies out there?
In this case, the news is good. A lot of astrophysicists think aliens are out there. Beyond that, they’re pretty mysterious (which is also good for science fiction). After all, no one has actually seen an alien. Here I am not counting the numerous reported cover-ups and conspiracies, but hey maybe those will pan out. Until then, here are my thoughts.
Is intelligent life out there?
Short of administering an SAT test to our extraterrestrial visitors, we have no way of knowing. However, we can (and do) speculate all day.
A naive assignment of probabilities says yes. There are ~100 billion (an insanely huge number) of stars in the Milky Way. Given our current planet detection rate, there are many more planets out there. Now, we really should only count hospitable planets, where the temperature is comfortable (read: water is in liquid form) and the surface is rocky (not some swirling gas mix). Even still, we could guess there are something like 100 billion habitable planets too. So we have a large pool to draw from as possible hosts to intelligent life.
We know intelligent life exists by looking in a mirror. Even if the odds are one-in-a-million, we’d have 100,000 other intelligent life forms in our galaxy alone. Note that this doesn’t account for the billions of other galaxies out there. In the greater universe there could easily be millions or billions of alien races.
The missing piece is figuring out those odds. Sure one-in-a-million means aliens are everywhere, but one-in-a-trillion means we’re probably the only ones in the Milky Way. What is that number?
We don’t know, but it’s probably high enough. You may have heard the term “carbon-based lifeforms.” That means carbon is one of the fundamental building blocks of life. It easily bonds with many other elements including hydrogen, nitrogen, and oxygen. These are all over; we can detect them in every star. So those building blocks are out there, and given that, it’s not a stretch to imagine them assembling to form life just like they did on Earth. (Aside – we don’t actually know how this all went down on Earth, so some speculation is built in to that conclusion).
That gets you life, but intelligence. That one I don’t think we have a good handle on yet. We think that life evolved here progressively. But evolution depends on pressure, adaptation, and time. If a planet is too nice, life wouldn’t evolve much because it wouldn’t need to. A little chaos, and even mass extinction, is good for progress. Then again, too much and complex life would get pulverized before it could form. So planet conditions really matter and we don’t yet know what is “normal.”
Still, even if that is a rare occurrence, it’s a good guess that it’s not vanishingly rare. What we know about the galaxy today suggests that the formation of intelligent life elsewhere is quite possible.
Why haven’t we seen any?
Again, I’m acting under the assumption that conspiracy theorists are wrong on this count. But in fact, we may have already seen life. If not through UFOs, then perhaps through unexplained observations in astronomy. Although there is no likely evidence, alien life could be the cause of several strange phenomena.
Otherwise, the most straightforward answer then is the size of the galaxy. Things are far apart and even if aliens had super great spaceships, it takes a long time to travel between planets – decades, millennia, maybe even millions of years. We can barely get to our own moon. That means there probably isn’t any space-faring life nearby (unless it’s hiding).
On a related point, we’re hard to find. Signals from Earth are modest at best and weaken rapidly as they travel from the planet. That limits detection range severely. So again, we’re kind of stuck with either crazy-super-advanced aliens or ones that are quite close by.
There are other, more speculative, reasons out there. Maybe the aliens are avoiding us for some reason (shouldn’t have badmouthed them behind their backs). Perhaps there is some other force (natural or artificial) that regulates intelligent life and has kept it from us. Or it could be that we really are the only ones (which also makes for a good story in its own way, as well as intense philosophical and theological debates).
Whatever the case, the absence of detection has left things wide open for stories.
Aliens in sci-fi: the (pseudo) responsible approach
If we want to restrict ourselves to the most plausible scenario our first contact would be with unicellular life (bacteria or similar). Kind of boring. One could possibly spin this into some scenario in which the bacteria cause mutations in Earth life making some horrific monsters. Or maybe they turn puppies into angels. Who knows. You’ll only get so much mileage from this one.
Then let’s jump to the other extreme. The heavily favored sci-fi aliens are humanoid. That is, they have a head, eyes (maybe three!!!), two hands, two legs, and a torso. Appealing because we can relate to these things more directly, but unlikely in reality. Stop and take a look around anywhere today. Four-legged creatures abound, but so do those with wings, flippers, and six legs. Plus we’ve got whole hosts of weird things with shells, squishy bodies, and tentacles. No shortage of shapes and sizes.
Now this is just on Earth. Imagine if conditions are different on another planet. Lighter gravity would allow bigger creatures. More water and aquatic life could dominate. A hotter sun and everything might need flat bodies to keep cool. The forms intelligent life could take are countless. Humanoid shapes are certainly still possible (and easier to cast in movies), but I’d love to see some more creative shapes working their way into popular sci-fi.
Besides looking like humans, sci-fi aliens usually act like humans. They embody our virtues and our vices. Some seek to save our planet from self-destruction (because they are more enlightened). Others want to conquer us and force humans into subjugation. While these may be thematically relevant to readers, they aren’t necessarily representative of alien behaviors.
True, evolution seems to favor competitive species. Even given that, the particular wants and needs of one alien culture, especially a space-faring one, are unlikely to resemble our own so precisely. Some species may have never faced a scarcity of resources, others could have a symbiotic relationship with sea slugs. Who knows. I think it would be fascinating to explore a species with a completely different values system.
In any case, the options are endless. Already many amazing types of aliens have been imagined, but this is a boundless pool of creativity. Imagine what we might see. I am as guilty as any writer of falling into the trap of modeling aliens after humans. That said, I’d hope to be among those who expand our minds and try to envision what true aliens might look like. Just make sure they're still fun to read about.
Science is at the core of many discussions in our modern world, yet is something which everyone interprets a little differently. Indeed, even for the professional “scientist” the word is ambiguous. I took a course in college highlighting seven different meanings of science, some leading to radically varying approaches to study.
It is not my intention here to put forth another academic treatise on the meanings of science. And, though I can be arrogant, I'm not so far gone as to believe that my thoughts are the final say on this incredibly complex subject. However, I would like describe what this word means to me, both professionally and in my approach to life. I hope that interpretations like mine can lead to understanding and open communication. After all, this topic is simultaneously powerful and polarizing.
Best to start with my definition. To me, science is an approach to understanding how the world works. That’s it.
The approach is a particular one known as the scientific method (several takes are available on what that means as well, but general references on the method abound). I just think of this as a very organized, systematic way of addressing a question. Understanding is gained in the form of generalizable knowledge (which I take to be different from human wisdom).
The method is inspired by a fundamental human curiosity. The entire point of this approach is to make sense of everything that goes on around us. The amazing part of it is that sensible patterns have emerged. What appears to be a storm of wild chaos whizzing around (weather, birds, bugs, people, cars, planets) seems to be, at least in part, based on an underlying order. A set of modest principles, when expanded to something the size of our Earth, gives rise to an astounding breadth of rich behavior.
As to what those principles are, I’ll leave that to your own study. Each field (physics, biology, chemistry, psychology, even economics) focuses on its own particular subset of the greater pattern, often at different size and timescales.
From this simple definition, subtleties abound. This has bred arguments, misconceptions, and in some cases anger. I like to think no one wants to carry it that far. In that spirit, I put forth a few of my opinions on phrases I’ve heard out there.
Science proves this.
Never the case. Inherent in the scientific method is a statistical analysis of experimental results. That means we infer the probability of an event occurring in the future given what we’ve seen in the past. Something is labeled “proven” if it is extremely likely to happen again. In reality nothing is guaranteed, only likely. Similarly, science cannot disprove anything. It can disfavor, perhaps strongly, but that is it.
Another major point that is behind the scenes-analysis of experiments nearly always relies upon some model of behavior. This is exactly like claiming a model car behaves exactly like a real car. If it is a good model, that’s almost true, but you’re never sure that you’re looking at the real thing. Science can say that a model is a good representation of the truth, but not that model=truth.
Don’t take this to mean that scientific results have no merit – I think we can all see from our recent technological boom that these probabilities and models, when understood, can change the world. Just recognize that absolute truth is harder to pin down that is often portrayed.
Science is confusing.
I won’t completely refute this one, but remember that science is not the only thing that has this reputation. However, at its core science is an organized and understandable approach to making sense of what we see everyday. If explained well, each step should be pretty clear. There are two parts that make this hard. One: there are lots of steps involved in rigorous scientific experiments. Two: the scientific method is not a natural way of thinking for most of us.
Let me illustrate. We see a few people drive past us fast on the interstate and we think “Man, people really fly here.” Everyone else in the car agrees, except for maybe Jim, and we move on with life. One step and done. End of normal approach.
A scientific approach is think, “Hmm, cars seem to go fast here, but is that true or were those last two drivers just anomalies?” One could set up an experiment to measure car speeds over a long period of time and accrue a list of man speeds. With some relatively simple math, one could analyze the car speeds, figure out the average driver speed, plus what percentage of people exceed the speed limit. Several steps, math needed, and a lot of more work than just assuming you are surrounded by speeders, but you have a much better idea of how people really drive in that area. Most of us don’t care, but civil engineers (who design the roads) and police officers might.
Of course, to do this right, a lot education is required (hence 4-9 years of college), but most people could follow this sort of experiment if they went through the schooling. Understandably, not everyone wants (or needs) to go through that, but it is nothing mysterious, just a lot of effort. In the end, a series of little steps build up a more complete picture of reality.
Nothing is valid until proven scientifically.
See the first comment on the “proven” part. What I want to get at here is that the scientific “stamp of approval” is, in my opinion, overblown.
The scientific method takes some work to implement, as we just saw with our interstate example. So going from a question to getting a definitive answer is very hard, especially when lots of variables are involved. For example, say we measured car speeds during a blizzard – we would conclude an average speed that is much lower than normal. This is most true when people are involved, as in medical research. Variability is off the charts, plus not that many people want to act as guinea pigs at any given time. So to say anything conclusive about every one of the 7 billion people on the planet from measuring a few dozen is all but impossible. Plus some rare events are super hard to measure because there is no easy way to set up a controlled experiment.
As another example, many Eastern medicines are only recently receiving widespread attention in the West, in part due to a recent scientific confirmation of their health benefits. This is also due to numerous other effects, such as the natural (and often healthy) reluctance to try something radically different. But we know that some of these practices have been effective long before they were scientifically “proven.”
My takeaway is that while scientific experiments absolutely help assess various methods and approaches to life, we still need to value human elements of tradition and social values. These have immense merit too that should not be forgotten, even in this age.
I may add to this list later, but this gets out a few of my general ideas. This one word, “science,” has become central to our culture, and to an extent our world. Of course, when an idea spreads that widely, it becomes wrapped up in many conflicting opinions and interpretations. Mine is just another one of those, but I consider myself more of a moderate (despite being a “scientist” for my day job). I am a proponent of responsible science in tandem with respectful and caring social practices. I hope that we all can go out into the world with eyes wide open, retaining both our curiosity and our humanity.
Who wouldn't be amazed by an object with such a high mass density that everything nearby, even light, is sucked in, never to escape? Black holes are one of the most fascinating astrophysical objects we've discovered. They've played a role in countless science fiction shows and books. People can't help but wonder what happens inside.
Even physicists are mystified. Well, I'm sure some of them would deny it, but they're only lying to themselves. The laws we think we know say that everything inside is compressed to a point, or as we call it a singularity. Of course, from our daily experience we're all pretty sure that such a thing isn't possible. What does that mean? New laws of physics! There are theories out there with cool names like quantum gravity to try to figure out what actually happens at the center of a black hole. We may never know the truth, but it's fun to think about (at least for a bit—eventually everyone needs a break to put their overblown minds back together).
I'm not even going to attempt to go into all of the physics of black holes here, but I wanted to point out something which, in my opinion, makes black holes even cooler. To get to that we all must first admit that, once we're past the mystery, black holes don't really look like much. I mean, they are supposedly totally black. Just picture it:
You might think you're staring straight at a black hole when an astronomer taps you on the shoulder and asks, “Why are you looking at that empty patch of space?”
Ever snappy on your feet, you would say, “Uh...I was just pondering electro-quantum-chromo, um, light-particle space physics. Um, Yeah!” Mm hmm, very convincing.
Evidence (and theory) now suggests that black holes may, in some cases, put out quite a bit of light. We still won't see any light emitted from within the Schwarzschild radius, true, but outside the black hole a lot can be going on. First, there can be accretion which is just a fancy word for stuff falling into the black hole. Since it is a massive object, matter in space is drawn toward it. I also want to point out that black holes are spinning (just like Earth). Through some fancy physics, it turns out that this spin preferentially pulls all that loose stuff into a disk around the black hole. There that stuff bumps around and gives off a ton of light, at least until it's finally sucked beyond the horizon.
Second, not all of this stuff is actually pulled into the black hole. Some of it is accelerated to relativistic speeds (which just means it's going close to the speed of light—super fast). This relativistic matter is expelled in two enormous relativistic jets, shooting out in opposite directions (perpendicular to the disk for those who care). These jets emit very high energy light, including X-rays, which we've actually seen with a special telescope in space, the Chandra satellite.
My super-crude picture:
Now, this can only happen if there is a lot of matter near the black hole, so many aren't so exciting. However, in the center of a galaxy there tends to be a lot of stuff close together, often orbiting a supermassive black hole. When these gather disks and shoot out their particle jets, we call them active galactic nuclei (AGN).
So next time you think of a black hole, picture one of these—it's a lot more fun than staring at empty space!
Science fiction draws its inspiration from...you guessed it - SCIENCE!