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Hello, it's Scott Manley here. Now I love the Star War movies.
When I first saw Star Wars as a four-year-old, it pretty much framed my life and sent me off in my spaceship that sets the course in life.
Now Star Wars movies are actually pretty light in terms of physics and science.
They're often misclassified as science fiction when I prefer to call them high-tech fantasy.
But there's one very important question for which we can invoke real-life physics.
Just what kind of power does it take to destroy a planet?
I mean three of the seven movies involve devices that are that are able to destroy planets.
And I should mention that there's a cup of minor spoilers here,
and as it turns out, it's pretty easy to figure out how much energy you would actually take to destroy a planet.
Indeed, in 2001, a paper addressed this issue by calculating the gravitational binding energy of these spherical planet.
You know, physicists love approximating things to spheres.
By the way, at least with planets that is of course a true reality.
And with the gravitational binding energy, it's a pretty simple concept for any Kerbal Space Program player.
We know that the escape velocity is the critical speed above which an object will skip to infinity and never fall back.
Now imagine that you grab a rope from the surface of a planet, shoot it off at escape velocity.
It's an easy equation to figure out how much energy is required.
And repeat that bit by bit, rock by rock, as you go on, you'll actually need slightly less energy
because I should throw bits into space, there's a less mass of the planet left behind to hold them down,
but then, if you add them all up, using calculus, you get a very simple equation.
The energy is 3/5 times the gravitational constant times the mass of the planet squared and divided by the radius of the planet.
Now, for earth, that number is about 2.25 time 10 to the 32 Joules, or in billion speak, 225 million trillion trillion Joules.
However, in the same paper they went on to calculate that for larger planets like Jupiter.
The energy would be even higher, something like 2 times tend to the 36 Joules.
That said, 2 trillion trillion trillion Joules.
The authors hypothesize that the Death Star ** be able to destroy this by shutting down some of its non-critical system, like life support.
And he wouldn't put that past the Empire given there are spotty record on providing basic workplace safety features like handrails.
Now, this paper is actually underestimating the power of this technological terror, and by extension, the power of the Force.
In Star Wars, we see the destruction of Alderaan, in but a few second, the planet explodes, sending fragments away.
But assuming that Alderaan is similar to the earth, that exploding ball of plasma is exploding at many times the escape velocity.
Look at this demo universe as an example to show how slow escape velocity is when you're comparing it to the size of the earth.
It's now particularly dramatic unless of course you're on the surface of that planet.
This is of course dumb because Star Wars is a movie and the audience expects special effect to well reward them rather than bore them.
If we reexamine the sequences in slow move, we can see that within a second, the ball of the pulverized planet is about two to three times the size of the original planet.
So the substantial part is moving at over 10000 kilometers per second.
We're dealing with velocities many times higher than the escape velocity
and the gravitational binding energy is really a small correction compared to the kinetic energy required to accelerate a planet's worth of mass up to these speeds.
To be fair, this is an explosion and it's more like a range of velocities,
but even if we take say a baseline of 1000 kilometers per second,
the energy required to obliterate Alderaan in this manner that will satisfy movie goers, is about 3 times 10 to the 36 Joules,
are once again 3 trillion trillion trillion Joules.
Now, in the Force awakens we have a new generation of planet busting super weapon that can project its beam of destruction over interstellar distances and destroy entire solar system,
but moreover, it's powered by a star which gives me another opportunity to invoke real physics.
Our Sun emits roughly 3.85 times 10 to 26 watts of power, or again in illion speak, 385 trillion trillion Joules per second,
which means that for our law and estimate, it would take about a week of the sun's energy output to obliterate Alderaan, or 250 years if you look at my higher estimates.
No more than 10 billion year life span of a star, that isn't so bad.
But I do have some straight of problems with this,
maybe I missed it, but it seems to me that they weren't planning on moving star killer base around.
After all, the energy required to move a planet into hyperspace is probably similar to the energy required to destroy a planet by moving its different pieces at several kilometer per second in different directions.
But if you have to consume the entire star to do that, then you would need another star, and if it can't move,
will, you gonna get another star. It seems like bad planning.
I mean, you don't even need mathematics to figure this out.
Okay, look, scrip writers, hello, look, there's a way to fix this.
There are stars have luminosities that are something like a million times higher than the sun.
They're short lived, but they can generate the energy required for epic planet busting for millions of years,
long enough for any movie franchise.
Star killer base could soak up all the power of 122 from the ultra layers of these stars.
It could even make the star turn from blue through red to black, as the energy was siphoned off,
giving those X-wing pilots a way to gauge how long they had to left in a visually arresting style,
and then, of course, after the siphoning stopped, the star would return to normal energy output and be ready for firing again in a few days time.
Of course the scriptwriter never asked me, regardless if you really want to go into planetary destruction to strike fear into the heart of your enemies.
The empire and the first orders are going a way overboard, making millions of voices cry out in terror,
just requires obliterating the top of your 0.1% of the planet near the surface.
The other 99.9% of a planet is generally sinks like magma that isn't particularly hospitable to life.
I'm Scott Manley. Fly safe.
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How Much Power Do You Need To Destroy A Planet?

2423 分類 收藏
Harvey Pan 發佈於 2016 年 1 月 13 日    Harvey Pan 翻譯    Jack Lu 審核
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