Comment by jdaley | Hacker News Reader

Comment by jdaley | Hacker News Reader

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We eventually tracked this down to some of the stabilisation algorithms – they work fine within the intended time frames, but there's an inefficiency in them that gets worse the longer the wormhole is open and eventually they can't keep up with the shifts.

An allusion to the accumulated rounding bug that caused the Patriot missile incident in 1991? That system was likewise intended to operate for only short periods.

From https://autarkaw.wordpress.com/2008/06/02/round-off-errors-a...

In the Patriot missile, time was saved in a fixed point register that had a length of 24 bits. Since the internal clock of the system is measured every one-tenth of a second, 1/10 expressed in a 24 bit fixed point register is 0.0001100110011001100110011 (the exact value is 209715/2097152).

On the day of the mishap, the battery on the Patriot missile was left on for 100 consecutive hours, hence causing an inaccuracy of 9.5E-8x10x60x60x100=0.34 seconds.

The shift calculated in the range gate due to the error of 0.342 seconds was calculated as 687m. The shift of larger than 137m resulted in the Scud not being targeted and hence killing 28 Americans in the barracks of Saudi Arabia.

Nice comparison!

But, more likely, it's just a play on a reason a Stargate (when unaided by some hostile energy source or time dilation field) just shuts off after 38 minutes with no explanation.

I agree that it is a play on that...

However in Stargate the actual 38 minutes thing isn't a computer limitation it is a physical one. In the original show (i.e. SG1) Carter said it is "impossible" due to physics for it to stay open longer, and they also established that with enough raw power (e.g. blackhole, ancient device, etc) it could be kept open longer or near indefinitely, it just wasn't possible with the normal power the Stargate needs to operate.

Keep in mind they did exceed 38 minutes many times with different explanations each time[0] none of which were computer related. It is also worth noting that earth in the show built their own DHD which presumably would have different computer limitations than the ancient built DHD (and as they established when all DHDs in the universe died except theirs due to the malware).

[0] http://stargate.wikia.com/wiki/Stargate#Exceptions

The basic conceit in writing this story is that when you only have access to an area of physics through poorly understood reverse engineered xenotech, a lot of arbitrary constraints imposed by the tech start to look like physical laws.

> In the original show (i.e. SG1) Carter said it is "impossible" due to physics for it to stay open longer

In a show like Stargate, "impossible" is really just another way of saying "It would require overcoming a series of increasingly unlikely and insurmountable problems for that to be possible." Which, of course, they then use for a plot device in later (or the same!) episodes as they blow past those increasingly unlikely and insurmountable problems. :)

> Carter said it is "impossible" due to physics for it to stay open longer

At the beginning of the story it's implied that things like that are why Carter would be upset. Because the physics they had thought they had learned from the stargate hardware turned out to be software limitations instead. It's not like humans are ever capable of creating a wormhole to test for themselves.

Later on, when Carter gives a lecture on wormhole physics at an Air Force cadet academy, the teenage protagonist of that episode reacts in the same way, and Carter gives an "I thought that way once, but then I saw enough compelling evidence to change my mind about what's possible" speech.

isn't a computer limitation it is a physical one.

Assumes facts not in evidence. That could easily be a firmware (on-gate) vs. software (DHD) argument.

Carter said it is "impossible" due to physics

Potentially unreliable narrator.

also established that with enough raw power (e.g. blackhole, ancient device, etc) it could be kept open longer

Yup, cited above.

built their own DHD which presumably would have different computer limitations

firmware vs. software

when all DHDs in the universe died except theirs due to the malware

you're not doing devops unless you have one button that can destroy your entire infrastructure

> It is also worth noting that earth in the show built their own DHD which presumably would have different computer limitations than the ancient built DHD

The gate itself has control crystals as you can dial out without a DHD if you just give it power and some elbow grease. The 38 minute cutoff is probably in that code.

They must have run out of code space in the gate and had to offload some of the code to the DHD. :D The correlative update routine for the coordinate system is in the DHD for example so the earth gate could originally only dial Abydos until they added that to their homebrew DHD.

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