The Science of Halo
You live on a giant ball of liquid metal surrounded by a thin skin of rock, hurtling through the cosmos at about 100,000 miles per hour, trapped in the gravity well of 4-billion year-old nuclear explosion. If that’s not cool enough for you, I guess you could try some escapism in a game called “Halo”, where instead you get to explore a giant metal ring. In 2001 Bungie introduced us to the fantastical sci-fi ‘Halo’ universe, the title being a reference to the ring-shaped artificial worlds, which provide the setting for much of the series’ action. But exactly how would such a ‘Halo’ work in the real world? What would it be like to visit or to live on one? What would happen if you fired a gun on a Halo? Well, make yourself a brew, sit down, and allow TheGameJar to ‘edu-tain’ you as we explore the answers!
Building a Halo.
The idea of a ring-shaped space habitat is not an original concept to the Halo franchise. Practically speaking, Halos would make pretty decent objects conducive to little blobs of flesh like you and I living on them. But how would you build one? Well, physicist Kevin Grazier (who was also the science consultant for the Syfy channel) discussed this in detail in an article back in 2007. Here I will try to pull out the best bits so that we can build a story of how the Halos would be built. Let’s tell the story as if we were going to build a Halo here in our Solar System.
First of all, we need to get planning permission. Not necessarily from the council, but we do need to choose a spot to build the Halo in. In the video game series, the Halos tend to be found in orbit of Gas Giants, so in order to stay faithful to the game, we will choose one of the four found in our Solar System.
Here’s where we walk joypad-first into our first scientific problem – radiation and debris. Earth sits in a remarkably quiet corner of the solar system. We have just one moon, which orbits us at a nice safe distance, and the planets gravity is small enough that most objects floating around the Solar System leave us alone. Jupiter, for example, has a little more of a stressful life. For a start, Jupiter has over 60 moons – that’s quite the orbital traffic-jam in comparison to lonely old Earth. Combine this with the fact that Jupiter (as with all gas giants) generates enough radiation to decimate anything electronic that gets within 300,000km of the planet. And to put the icing on the celestial cake, Jupiter’s gravity well is so damn huge that it is a common occurrence for comets and asteroids to come careering through the planet’s vicinity. You can now see why Halo’s ‘Forerunners’ could maybe have chose a more… picturesque place to locate their gargantuan creations!
We could shield the Halo from radiation using the same method that protects us from solar radiation here on Earth: magnetic fields. If you ran a huge electric cable around the entire Halo, and pumped enough current through it, you would create a magnetic field strong enough to deflect harmful cosmic rays. You’d also get some really cool ‘Northern Lights’ effects.
Where would you actually get the materials needed to build a Halo? This is actually quite an interesting question. Assuming a Halo is around 30,000km in circumference (thanks, Halo Wiki!) you’d put the volume of the ring at about 200 million cubic kilometres. That’s big. Allowing for corridors and windows etc, lets say that 50% of that volume is filled with solid structure. According to Kevin Grazier you’d need about 1,700 million billion kilograms of metal. Ouch.
Now, most of the asteroids in our solar system are made of metal, but even then Kevin Grazier calculates that “The entire asteroid belt between Mars and Jupiter would have just about enough mass to construct one Halo.”
So building the Halo would take a whole lot of mining before you even got to the construction issues!
Your Visit to the Halo.
While a gracefully floating Halo may seem like a tranquil destination with its beautiful tropical scenery, landing on a Halo really wouldn’t be a tranquil experience. You’d probably be burned to shreds, or squished to mush. Why?
A Halo with a 5,000 km radius would spin at about 15,000 miles per hour in order to simulate gravity for the people stood on the surface – that’s 21 times the speed of sound. This means that a craft approaching the surface must do so with great precision, even more so than a craft entering a planet’s atmosphere. One wrong move and you’ll be slammed against the ring, or burned to a crisp by atmospheric friction. To quote the BSG Science advisor, “without the proper approach, a ship attempting to land on the inner surface of a Halo could still be met with near-instantaneous incineration—not a particularly welcoming introduction.” Well said.
If you do manage to land on the Halo, this is when things get interesting. While ‘gravity’ on the surface would feel like Earth’s gravity, you must remember that what you are feeling is not gravity! It is ‘centrifugal force’. This means that objects in the air like a ball you throw, or a drop of rain would not simply fall like an object would here on Earth. This is because rather than ‘resting’ they would always be carrying the immense speed of the Halo’s rotation.
For example, take a waterfall 300 feet high. If the waterfall was oriented sideways in the halo, it would hit the ground two meters to the left of where it would on Earth, due to the extra change in speed of the water as it falls. Minor detail, but it would have been cool if Bungie had animated things like this into the game!
Going into Combat on the Halo.
You might say that Bungie really missed a trick here. The waterfall fact has a nasty consequence in combat, especially if you like shooting bullets, which are victims of the same speed issues as water droplets. For objects close-up, your bullets would not behave in a way noticeably different to that of a bullet on Earth. This is because bullets travel very quickly, so the subtle effect of the initial speed from the Halo’s rotation only manifests itself at long range.
So here’s where Bungie maybe missed a trick; it could have been an interesting and frankly original game mechanic to factor in the Halo’s relative speed to sniping in the game. Perhaps the sniper scope would have a computerised marker indicating where to fire to account for speed drop, but it would take a second to calculate. This could have made sniping tenser; wait for the calculation, or risk shooting by eye in crunch situations!
To sum up the worrying effects of bullet speed, think about a gunshot straight up into the sky. If there is no wind, the bullet will drop to the ground right where it was fired. On a Halo, “a round fired straight up does not, in fact, return to where it was fired, but rather eighteen kilometres downrange due to the seven kilometres per second speed that the round had before it was even fired”, according to Kevin Grazier’s calculations.
So it turns out that the covenant should have a huge battle advantage on a Halo; using Directed Energy Weapons (lasers, plasma guns etc) means that your projectiles are light-based, and wouldn’t be noticeably affected by the Halo’s rotation.
For Science!
So how did you enjoy your trip to the Halo? It seems as if we have established that building one would be very difficult, especially in our solar system. If the radiation, or space debris don’t kill you, then there’s a good chance that landing will. And if you do get there, physics will not be quite the beast you’re used to. So if you want to fight the covenant, don’t forget your laser!
Umm, about that shooting thing… Indeed, if you took a shot straight up, the bullet would fall quite far from you. But you don’t shoot straight up) You shoot dead ahead, or maybe down. And in local coordinates the spin of the ring would cause a negigible error. Also, you don’t do really long-range shots in Halo.
What if you’re shooting the sky and spinning in circles? :)
That is why COD fanboys aren’t allowed to visit.
“Directed Energy Weapons (lasers, plasma guns etc) means that your projectiles are light-based”
A Laser is indeed made of light, A plasma gun is not. Plasma is a cloud of ionised particles, so would still be effected the same as a conventional round.
Confirmed. Don’t know how I missed that!
I’m tempted to ret-con the statement by positing that the mass of the plasma fired would be vastly smaller than that of the bullet, but I know that doesn’t cut the mustard. Good catch, squire!
What if we could create on the halo ring like the covanent do on their ships?
Something to ponder:
Considering how massive the rings are, they would most definitely have to generate some sort of gravity well, though this would obviously be less than an Earth or the Moon. Not sure how the shape of the ring (not being a sphere) would play a role in that, along with it’s own tendency to want to collapse in on itself, though I suppose the diameter and density/mass plays a role in that calculation to overcome it’s own gravitational pull to collapse. I’m curious on how its spin affects a waterfall falling (even though the water and air it’s passing through should be travelling roughly at the same speed) to a degree that’s noticeable when it would clearly also have a limited gravitational pull, while the earth has gravity as well, the earth also spins at a considerably high speed.
Landing on it to me seems like it would be difficult, but air friction I don’t really understand. We have significant air friction during atmospheric re-entry on earth due to travelling ~18000 mph in relation to the surface of the earth and atmosphere). The reason being is due to being in a state of constant ‘free-fall’ in order to orbit the planet due to gravitational pull. If we are stationary over the planet in relation to ‘spin’ ; geosynchronous orbit, and just fall, the friction is relative to velocity approaching the surface and is manageable, as shown by a man recently free-falling through our atmosphere a couple weeks back.
With Halo, gravity isn’t nearly as much of an issue as is catching to the speed of the ring, but the atmosphere around the ring should be travelling roughly the same speed (Although is this more of a condition of gravity, and if it is, what would the weather/wind forces be on the rings surface if the air/atmosphere isn’t spinning with the ring’s surface?) which means matching the speed of the ring while landing should also have negligible friction to the speed of the airflow (assuming it IS travelling roughly the same speed of the ring, which I’m starting to think it wouldn’t be). If the air isn’t travelling at the same speed, I think landing on it would be the least of our worries. Hypercane winds of +500mph or something ridiculous would make this thing uninhabitable.