Moving, it's never easy. 
The packing and unpacking, 
having to start fresh and make new friends, 
all this can be challenging. 
Let's face it, whether it's a nasty landlord 
or an imminent threat to humanity, 
sometimes you just have to move!
In another WHAT IF, 
we've looked at moving the Earth 
to avoid certain danger,
but what if that wasn't enough?
What if we had to build a stellar engine
to move our entire solar system?
To move our solar system
would require an incredible amount of energy
and careful planning.
We could potentially do this with a stellar engine,
a class of hypothetical megastructures
using a star's radiation to create usable energy. 
Thankfully, with our planets 
locked in orbit of the Sun
due to its immense gravitational pull,
we only have to find a way to propel the Sun
and our planets and moons will follow.
Russian scientist and aeronautical engineer,
Leonid Shkadov,
proposed an ingenious method to move our Sun
using a giant parabolic mirror
It works by harnessing the Sun's photons
and reflecting them back around the Sun, 
creating thrust. 
Each photon carries a tiny amount of thrust,
meaning if you were in space,
and you turned on a flashlight,
you would eventually move ... 
just very, very slowly.
The Sun produces 
10 to the power of 45 photons per second.
This impressive energy makes the Sun
the most powerful nuclear reactor ever!
As a result, we would have to position
this parabolic mirror exactly over the Sun's poles
to avoid burning one of our nearby planets.
This limits the direction we could move,
and it would likely take us 
about 230 million years to move 100 light-years. 
That's an astronomical amount of time,
so is there a faster and more efficient way
we could move the Sun?
Astrophysicist Matthew E. Caplan
of Illinois State University
has proposed a new type of engine
This stellar engine requires 
one quadrillion satellite mirrors,
known as a Dyson swarm,
to orbit the radius of the Sun.
These would reflect the Sun's energy
in a concentrated area,
heating it up and shooting the Sun's mass
and solar winds outward,
allowing us to utilize the billions of tons
of Hydrogen (H) and Helium (He) collected
using large electromagnetic fields.
A thermonuclear reactor on board
could conceivably convert
the Helium and Hydrogen
into radioactive oxygen
used as exhaust to propel the craft.
And any leftover hydrogen from the Sun
would be shot in a jet of plasma
using a particle accelerator,
pushing the Sun forward
and keeping the thruster
from being sucked into the Sun's gravity.
This delicate balancing act
would allow us to move in any direction we want
at much greater speeds.
The real challenge might be 
building the Dyson sphere itself.
For one thing, we would have to mine Mercury
for its rich supply of metals and minerals,
This would take a considerable amount 
of time and effort,
but could provide us with 
an almost infinite energy source. 
Learn more about that in our other video,
Now, what would it feel like on Earth
when our entire solar system goes
surfing through space?
Well, it turns out
everything might feel more or less the same.
Researchers at Illinois State University
believe that shifting the solar system
wouldn't disrupt our planets' orbits,
since the thrust of a stellar engine
would create just a small acceleration overall.
As we orbit the Sun,
the Sun orbits the galactic center of the Milky Way,
we don't feel this movement because it's constant.
If the Earth suddenly stopped moving, however,
we'd be in cosmic trouble!
With so many travel destinations in the universe,
we'd still be limited to 
only a small portion of it known as
This collection includes 
our massive Milky Way Galaxy, 
the Andromeda and Triangulum galaxies,
and about 50 other dwarf galaxies.
Due to the mysterious force of dark matter,
scientists have discovered
that the universe is rapidly expanding.
Even though we can see them,
all the other galaxy groups
are moving farther away from us
at speeds we will never be able to reach.
We'd be better off looking for
other habitable planets like ours 
within our own galaxy!
In approximately 4.5 billion years,
our Milky Way will eventually collide
with the Andromeda Galaxy, forming
At this point, galaxies outside the Local Group
will be so far away
we won't even be able to detect them 
like we can now. 
Future civilizations born in
the Milkdromeda Universe
may think the Local Group is all there is.
They wouldn't be able to learn about the Big Bang
and may think that the universe 
is static and never-ending.
So consider yourself lucky
to be living in a time where we can research 
the past and possible future of our own Universe. 
Maybe someday we will harness our stellar energy
and get to explore our galaxy
and make some new friends along the way.
This would make us a Type II civilization
on the Kardashev scale,
which measures a civilization's
technological ability to control and utilize energy. 
Sadly, we're barely a Type I civilization,
as we still haven't figured out
how to harness all of Earth's available energy,
but that's a story for another WHAT IF.
