Professor Dave here, let’s explore the galaxy.
On July 20th, 1969, American astronauts Neil Armstrong and Buzz Aldrin landed a lunar module
on the surface of the moon, and stepped out to walk upon its surface.
It was one of the greatest moments in human history, the first time that humans set foot
upon an extra-terrestrial body, a world other than our own Earth, our home.
In that instant, humans became a space-faring civilization, as was captured in Armstrong’s
immortal words: “That’s one small step for a man, one giant leap for mankind.”
Much to the disappointment of science fiction fans everywhere, in the nearly fifty years
since the moon landing, mankind has not set foot on any other worlds.
Probes of our own engineering have touched down on or impacted the surfaces of Mercury,
Venus, Mars, Jupiter, Saturn, Titan, two asteroids, and a comet.
But not yet has a human being set foot on any of these worlds.
Plans to send humans to Mars have been underway for many years, and it is nearly certain that
this will be the next place we will visit in person.
Venus is slightly closer, but utterly inhospitable, so Mars is the most logical choice.
What will we do once we get there?
Is Mars really a good place for humans to live?
Well, the short answer is no, not at first.
It’s very cold, and there’s no oxygen.
Life would be limited to pressurized and temperature-controlled habitats, or at best a futuristic dome.
But believe it or not, we can fix that.
Just the same way that excess carbon dioxide is causing global warming here on earth, with
negative ramifications due to a greenhouse effect, we can deliberately enact this process
on Mars in order to make the climate more suitable for life.
There is a lot of carbon dioxide and water locked away in the polar ice caps, and it
wouldn’t be that difficult to blast it up into the atmosphere with some huge bombs.
Once it was distributed evenly around the planet, it would raise the temperature, which
would begin to unlock more carbon dioxide locked in all the soil, and there would be
a runaway affect, heating the planet relatively quickly, by cosmic time scales at least.
Water vapor would condense and rain down to form oceans.
Once it was warm enough, we could grow plants directly on the surface, and if the atmosphere
became oxygenated enough, it should be possible for humans to walk around the surface of Mars
with no spacesuit or protective layers of any kind, just as though we were walking around
on Earth.
This process of deliberately modifying the atmosphere, temperature, and even topology
of another world to make it suitable for Earth life is called terraforming.
And if we could achieve this on Mars, we would have a second world to live in.
Mars is much smaller than Earth so gravity is much weaker, which would make for some
incredible Martian olympic games, where all the world records from Earth for long jump
and high jump would be shattered easily by average people.
So how long would terraforming take?
Quite a long time, unfortunately.
The most liberal of estimates predict several hundred years to get things suitable for a
picnic, and more conservative ones say several thousand.
There are also many things that could go wrong in the process, so it’s not a sure thing.
If we do something wrong and Mars becomes permanently uninhabitable, it will be all
our fault, and killing a whole planet is a lot for anyone’s conscience to bear.
But perhaps one day we will get it right, and Mars will be the ultimate vacation spot.
Where else might we go?
Earlier in the series we talked about some of the moons of Jupiter and Saturn, and a
lot of these would be reasonable places to set up camp.
Europa, Callisto, and Ganymede, orbiting Jupiter, as well as Enceladus and Titan, orbiting Saturn.
As some of these are worlds that might already harbor life, a bonus could be some new friends
to play with.
We wouldn’t be able to terraform due to the ethics involved with altering such biology-supportive
worlds, so artificial habitats would be crucial.
And the low gravity on these moons would be a problem for stays of long duration.
But it seems inevitable that we will build a base on one or more of these worlds, even
if just for research purposes.
So how can we support such habitats?
It’s too expensive to bring lots of things with us from Earth.
So how will we generate the energy and resources to sustain human life in these places?
One pivotal technique would be asteroid mining.
Asteroids contain a wide variety of substances that could be of use to us, like water and
even some rare metals, like platinum.
With so many asteroids ready to be mined just beyond Mars, and the ease of lifting off from
them because of the negligible gravity, this is one method that would make living on Mars
or one of Jupiter’s moons quite a bit more feasible.
So let’s say we jump ahead a few centuries, and we’ve colonized a number of worlds in
our solar system.
What’s next?
Would it be feasible to colonize other systems?
There’s certainly nothing stopping us.
But one huge hurdle is the immense distance required to go anywhere else.
The closest star to us besides the sun, Proxima Centauri, is a little over four light-years away.
Even with the fastest speeds we have ever achieved with a spacecraft, it would take
tens of thousands of years to get even just to this nearest system.
So it is very clear that any colonization attempts of this nature would require a major
paradigm shift in propulsion.
We talked about some of these possibilities in the modern physics course, when we discussed
the future of space travel, so if you’re interested in these hypothetical propulsion
systems, check that one out now.
Otherwise, it’s not outrageous to think that such technology will come, and we will
indeed begin to spread throughout the galaxy, with large populations on massive ships that
go from one star to another within a human lifetime.
A civilization of this level will need a lot of energy to sustain these new colonies, so
fossil fuels absolutely won’t cut it.
Instead, we may need to harness the energy of the sun.
We’ve already begun doing this with solar panels, but consider what a tiny fraction
of the energy radiated by the sun is being captured by a little panel.
This radiation goes outwards in all directions, just imagine if we could harness all of that
energy?
A hypothetical structure that does just that is called a Dyson sphere.
It seems farfetched, but it might be possible to build some kind of structure comprised
of many small objects that encompass the sun at some distance.
This could be a spherical swarm of objects, or even simply a ring, and it would be able
to harvest a tremendous amount of energy from that star.
To harvest all of the energy, it would have to actually be a spherical shell, and this
would yield an amount of energy trillions of times greater than the human race currently uses.
There are a number of complications regarding gravity that arise with such a structure,
and these would have to be solved, but a bonus would be the ability to live on the Dyson
sphere itself, which would be unimaginably huge, with a surface area millions times greater
than the earth.
Whatever variety ends up being the most feasible, it seems that it will be difficult to reach
a certain level of advancement relying on the resources found within a planet, and harnessing
the power of a star will be crucial if we are to become an interstellar species.
In fact, it has been proposed that we should be looking for precisely this kind of structure
in space, as that would be pretty undeniable evidence of intelligent life.
How would we distinguish between such a civilization and our own?
There is a scale that measures how technologically advanced a civilization is.
It’s called the Kardashev scale.
This scale categorizes civilizations as being type zero, type one, type two, or type three.
Humanity comprises a type zero civilization.
We are still using crude forms of energy, and have not yet figured out how to use all
of the sun’s energy that hits earth’s surface.
A type one civilization has figured that out, and we may get to type one categorization
within the century.
We will have to be completely independent of oil and other fossil fuels, which is seeming
more and more realistic by the decade.
So the moment that humans will become a planetary civilization, or a type one civilization,
seems to be just beyond the horizon.
But if we became a civilization capable of creating a Dyson sphere, or some similar structure,
then we would be a type two civilization, or stellar civilization.
This is one that can harness all of the energy produced by a star.
Beyond this, to become a type three civilization, or a galactic civilization, we would have
to be harnessing the energy of the entire galaxy.
Perhaps this would have something to do with the supermassive black hole at galactic center,
and a strange technique called black hole farming that has been hypothesized, which
is actually quite mathematically sound.
What type of civilization will mankind become?
Will we colonize other worlds?
Can we harness the energy of the sun?
It’s difficult to predict, as self-destruction is always a very real possibility.
But that’s why it’s so important for us to be educated, so that we can remain on the
same side, and work together to create a bright future.
In terms of being on the same page, there are a number of astronomy-related phenomena
that the common public seems to be divided on, to one degree or another.
So let’s move forward and see what some of these topics could be.