[personal profile] clovehitched
Disclaimer: This post might not be entirely serious, read at your own risk.

On March 3rd, 1972, NASA launched its Pioneer 10 probe. This was followed by Pioneer 11. Pioneer 10 is the one with the famous plaque showing naked human bodies on it so that the space aliens will know all about us, which is kinda cute.

In the nearly 40 years since launch, these spacecraft have gone a bloody long way, and are heading towards the heliopause.

However, something about these two probes baffles astronomers. As you might expect, the Sun's gravity is slowing them down (it shouldn't ever reclaim them - they have solar escape velocity, so they will go interstellar eventually and end up who-knows-where, in some other star system long after our species is extinct. I think Pioneer 10 is used as target practice by a Klingon in one of the Star Trek films, but I digress). The thing is, they're not slowing down as much as they should. This is known as the Pioneer Anomaly.

Scientists have proposed all sorts of explanations about why this might be. Dark matter pulling at them from outside? Our understanding of gravity or inertia being wrong? Some completely new physics? Something else?

Well, I just worked out what it is tonight. I was playing this awesome computer game on the iPad - Osmos, which is sort of a cross between Thrust and Katamari - you have this mote and it can fire off reaction mass and absorb things smaller than itself, but gets absorbed by bigger things. You have tasks on each level (usually becoming big, or absorbing a specific target). One set of levels features "attractors". This is basically where there is a central object on the level which exerts gravity, and everything orbits round it. You have to have some knowledge of how orbits work to do these levels - going away from the "star" by speeding up, changing your eccentricity, that sort of thing.

One of them has a goal of absorbing the attractor itself, and when you do something odd happens - everything else in the system stops orbiting and leaves the system on a tangential path, because once you absorb the attractor, gravity disappears.

In other words, the motes have inertial mass, but not gravitational mass. The only thing with gravitation mass is the attractor.

There is a reason for this - doing a gravitational simulation of an N-body system, where N is large (and these levels start off with hundreds or even thousands of motes) gets computationally hard really fast. There's no way the iPad with its impressive but still quite small processor (I worked for the company which designed it in a former life) could handle the maths quickly enough, so it cheats. Mostly you don't notice. except when the attractor disappears and gravity suddenly fails, because the cheat is close enough.

Various people have proposed that our universe is some kind of computer simulation. It seems likely by the sheer weight of numbers. The argument goes that we're getting quite good at computer technology, and can envisage a day when computers are really really good, and we could build one so huge, and so massively parallel, and so vastly powerful that it would be able to perform a physics simulation of an entire universe.

Take this one step further, and it would follow that intelligent life would eventually arise inside the simulation, if it has similar rules to our universe, and start building its own virtual computers. The organisms being simulated would not know they were simulations, of course - how could they? Eventually they would build a virtual computer powerful enough to simulate a universe of their own, and so it would repeat, all the way down, like Russian doll universes, with only the outermost actually being real.

Of course, if the simulations were done well enough then each universe's inhabitants would think they were living in the real one, but only one universe out of thousands, or even millions, would be right.

The odds are, therefore, that our universe is a simulation.

But this is ultimately solipsistic, or at least along similar lines. We can't know whether it's true, and even if it is we can't tell, so it's a philosophically pointless position.

Or is it?

See, I reckon the temptation might be to simulate a universe before your computer was powerful enough to do it properly. Consider if you were alive 10,000 years from now with scary powerful computer technology, and capitalism still exists and you want to make the ultimate computer game - a full immersion computer game which simulates a whole universe for players to get lost in. It would of course be populated with AIs (us), to make the game more interesting. Maybe you could rule over them as their god and torment them in interesting ways, and see if they still worship you or something equally sadistic (there's this iPhone game like that - it's quite good fun!)

You'd want to get this to market before your competitors could, to maximise your profits and fame, so you're tempted to cut corners a bit. In particular, you can make things go much faster if you don't do gravity properly. You just need to make it convincing enough that it looks real to your player, and your AIs. In other words, you cheat like mad to lower the minimum system requirements and hope nobody uncovers the corner cases.

That's why the Pioneers are speeding up. Our universe is a computer game, and the program isn't doing gravity properly.

It's a brilliant theory - it even explains George W Bush!

Where do I get my Nobel Prize?

Also posted at http://auntysarah.dreamwidth.org/244763.html - you can comment here or there.

Date: 2010-08-06 02:18 am (UTC)
From: [identity profile] natalie-i-am.livejournal.com
This makes scary sense and easily explains Alternate Realities, and multiple galaxy's and universes. Multiple shards with little bits of overlap [part of the corner cutting].
Sarah, you are a genius!

Date: 2010-08-06 02:24 am (UTC)
agent_dani: (Default)
From: [personal profile] agent_dani
Nice theory, though my read of the anomaly is the reverse; it's slowed more than expected, described as an acceleration toward the sun.

Date: 2010-08-06 11:07 am (UTC)
From: [identity profile] paulathomas.livejournal.com
Mine reading too I am afraid. It will be interesting to see whether the Voyager craft produce the same results.

But nice hypothesis!

Date: 2010-08-06 11:30 am (UTC)
ext_8007: Drinking tea (Default)
From: [identity profile] auntysarah.livejournal.com
Oh yes, it does say that, doesn't it?

Not incompatible with the theory though ;-)

Date: 2010-08-06 04:21 am (UTC)
ext_28673: (Default)
From: [identity profile] lisaquestions.livejournal.com
I just want to say that Osmos is either completely calming to play or it annoys me so much I get out a shooter instead.
From: [identity profile] christinaalley.livejournal.com
Nice! Is your theory compatible with the universe-as-hologram thesis (as evidenced by the 'graininess' and directional bias of sub atomic particles at high resolution)? And could a combined theory explain the Northern Lights?
http://www.bbc.co.uk/news/science-environment-108808

Date: 2010-08-06 07:34 am (UTC)
From: [identity profile] alicephilippa.livejournal.com
Not sure about the Nobel Prize, but you can get pizza.

Date: 2010-08-06 11:28 am (UTC)

Date: 2010-08-06 08:56 am (UTC)
From: [identity profile] meihua.livejournal.com
Far as I understand it, any simulation of a complete universe will be imperfect, because to simulate a complete universe perfectly, you need a computer the size of a complete universe, or at least one that's expanding constantly at light speed in all directions. :D

But that all kinda assumes that simulating universes can be done at all...

Date: 2010-08-06 11:29 am (UTC)
ext_8007: Drinking tea (Default)
From: [identity profile] auntysarah.livejournal.com
Surely it just needs to hold a volume large enough to allow the universe to expand into for the duration of the simulation? At some point the program will be terminated...
(deleted comment)

Date: 2010-08-06 01:54 pm (UTC)
From: [identity profile] knirirr.livejournal.com
There is a Stephen Baxter story where that happens; we extend our ability to observe the universe in detail beyond the range that the simulation can process (by bouncing a laster off an extrasolar planet) and a crash follows.

Date: 2010-08-06 01:41 pm (UTC)
From: [identity profile] meihua.livejournal.com
Stuff affecting the point of simulation reaches the point of simulation at light-speed; e.g. the gravity waves of distant stars. So, at the time at which the gravity from a star would have reached the point of simulation, that star has to exist within the simulated area - i.e. a lightsphere surrounding the point of simulation. So, yeah, I guess if you like, the computer needs to be larger in physical size than a sphere of radius t x c where t is the expected duration of the simulation. That's still, uh, pretty big.

I think. I'm not an expert!

Date: 2010-08-06 01:46 pm (UTC)
ext_8007: Drinking tea (Default)
From: [identity profile] auntysarah.livejournal.com
We don't know what the physics of the host universe are - they could be such that the computer can be smaller and more powerful, because our physics are much less exotic than theirs.

Date: 2010-08-06 02:30 pm (UTC)
From: [identity profile] christinaalley.livejournal.com
Surely, if it is a simulation, our universe requires no physical space whatsoever, or only the physical space required for a supercomputer in the host universe. We might be a sim on some kid's watch!

Date: 2010-08-06 03:10 pm (UTC)
From: [identity profile] meihua.livejournal.com
Simulations require physical space. Your computer requires physical space for its hard drive and memory. It uses up less space than, e.g. paper, because it's compressed. But you can't compress something which is at 100% entropy, such as analogue matter. There's no way to represent a grid of the smallest possible particles without using at least a handful of bits per particle (since there's more than 1 type of particle) and each bit of storage is bigger than the smallest possible particle, since it has a switching mechanism, monitoring mechanism etc.

Date: 2010-08-06 03:17 pm (UTC)
ext_8007: Drinking tea (Default)
From: [identity profile] auntysarah.livejournal.com
Cheat. Model macroscopic properties and only model at microscopic scale when people are looking/where it matters. This is similar to how I used to model CPUs when working back at ARM.

Date: 2010-08-06 03:30 pm (UTC)
From: [identity profile] meihua.livejournal.com
No way would that work. You'd end up with all kinds of crazy stuff going on, like phenomena which only resolved when observed. Why, you could put a cat in a box and--

Date: 2010-08-06 04:34 pm (UTC)
ext_8007: Drinking tea (Default)
From: [identity profile] auntysarah.livejournal.com
Be very afraid...

Date: 2010-08-06 03:07 pm (UTC)
From: [identity profile] meihua.livejournal.com
Oh, you cheat. :D

Date: 2010-08-06 12:13 pm (UTC)
From: [identity profile] becky44.livejournal.com
OMG!!!

If the super iPad - or whatever running our universe - has become self aware..... we're living inside someone's pet Cylon!

Can I have Baltar's IP address? I want to contact him and join his hareem!

Date: 2010-08-06 02:15 pm (UTC)
From: [identity profile] nicollegurrl.livejournal.com
I like the Pale Blue Dot alot! :-)

Date: 2010-08-06 03:44 pm (UTC)
From: [identity profile] gina-r-snape.livejournal.com
So, people keep insisting that CERN won't produce black holes big enough to suck us all in. But could it be possible that if it does, that will really be nothing more than someone pulling the plug on us, in our simulation? :D

Date: 2010-08-06 06:42 pm (UTC)
From: [identity profile] scribb1e.livejournal.com
>Where do I get my Nobel Prize?

Congratulations NAME HERE!!1!

You have won a Nobel Prize for your theory!

Send only £99.99 now and receive your Nobel Prize certificate and souvenir commemorative plate! For a limited time only!

Date: 2010-08-06 07:17 pm (UTC)
From: [identity profile] valeriekeefe.livejournal.com
I'm sorry but I refuse to believe in an intelligently designed universe that does not have near-universal lesbianism and birth assignment is drawn by lot... but then, I'm rather quickly turning into a cultural transfeminist.

Date: 2010-08-08 11:45 pm (UTC)
From: [identity profile] aumentou.livejournal.com
Just because the universe is intelligently designed as a set of models and processes doesn't mean the cultures of AIs within the universe are also intelligently designed. Indeed, that would be rather missing the point.

*makes equivocatory gesture*

...better porn though.

Date: 2010-08-08 11:49 pm (UTC)
From: [identity profile] aumentou.livejournal.com
I suspect the designers would cheat. Starting with a few solar systems, and fast-forwarding until it got interesting. Then they'd have to add processing capacity like crazy once interstellar expansion kicked off...

...so remember kids, don't expand exponentially into the universe. You might trigger a serious server overload.


Which raises the question: would an intelligent AI in a simulation notice if the system was suffering from lag? I doubt it. This could be a way to spot the alien players!
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