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Comment by rando2195 | Hacker News Reader

Their "is hft good or is it bad? it's opinion! <but look at all these scary things they are "responsible" for>" bit is really disappointing. I see it in articles all over the place and it's really lazy research and reporting. Isn't this article about the tech? Why are we suddenly having an extremely off-the-cuff discussion on whether HFT is "good or bad"?

Also, I have trouble reading the tone of the article. I hope the "making trades in the past" and "until someone manages to break the laws of physics" are completely in jest. I know it's probably a joke, but it's a poor enough excuse for one that it just leaves me wondering if they might actually be somewhat serious.

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"Isn't this article about the tech? Why are we suddenly having an extremely off-the-cuff discussion on whether HFT is "good or bad"?"

Since when is tech automatically amoral? I mean sure, the technology itself doesn't care, but that doesn't mean we shouldn't. You can discuss both simultaneously.

Regarding the "laws of physics." Quantum mechanics does open up several possibilities for violating the speed of causality.[1] There is nothing that says any of the laws are fundamental truths, they are simply the way things always work, so far as we know. It's quite likely we will find exceptions.

1: http://www.bmeacham.com/whatswhat/Quantum.html#2.3.Causal%20...

QM does not open up any avenues for violating causality. bmeacham.com is crackpot based on my reading the first 2 paragraphs.

Usually, misunderstandings about causality come from a naive reading of the terms "advanced" and "retarded" solutions to wave equations, which also show up in classical electromagnetic theory.

https://en.wikipedia.org/wiki/Green's_function_(many-body_th...

Ok. Here is a better source for you: https://arxiv.org/abs/1401.0167

bmeacham was just the first search result that was trying to explain the general concept I was referring to, so I don't have to write an article in the comments :)

Cornell seems to like putting out phd theses on this subject:

https://arxiv.org/abs/1607.07871 https://arxiv.org/abs/1608.01528 https://arxiv.org/abs/1607.00381 https://arxiv.org/abs/1605.06022

Seems like Cornell is wasting a lot of time researching something that you've already determined is impossible.

Everything you're linking too is either highly speculative (e.g, hypothetically taking place yoctoseconds after the big bang, and completely unconfirmed) or is addressing some subtle interpretative senses of causality which are very distinct from the normal sense (such as the paper by Leifer and Pusey, who worked/work down the hall from me).

That paper is discussing nonlinear quantum mechanics, models of which are almost always internally inconsistent. More importantly, it's just speculation; the kind of quantum mechanics that has been confirmed in the lab is linear.

It's well known that quantum mechanics does not violate causality (when defined appropriately in terms of actual observations).

But my whole point was speculating that it's possible, not that it's proven to be true. So of course I am citing speculative sources, this is speculation... :\

Although it may sound like it, I don't believe it's splitting hairs to draw an important distinction between (a) speculation that might be observable in our lifetime, or might have relevance to stock trading, and (b) speculation that has fundamental inconsistencies with deep principles on which the entire known body of physics knowledge is based, and which would revolutionize our understanding of the universe and the nature of reality if true. Here's another way to say it: time travel is strictly less crazy than acausality.

Sorry, not trying to be a buzzkill :)

Not a problem. I prefer learning to being right :)

> It's quite likely we will find exceptions.

That's obviously some definition of "likely" other than the one I am familiar with.

One that refers to an larger time frame than you are probably thinking of. See several of Newton's laws of physics having exceptions the scientific community was not aware of for a long time.

I am not saying this going to happen in any of our lifetimes. But given a large enough time-frame, I am pretty sure most of our current understanding will turn out to be terribly inaccurate at an absolute level (although a good approximation based on what we currently understand)

For any time frame that spans the human race, I consider it highly unlikely that we will find any exceptions to the speed of causality.

Yes, I recognize that the possibility exists. Yes, I recognize that our understanding of the laws of physics grows over time. "Quite likely"? Still no.

I didn't say it was likely we would find something violate causality, I said it was likely we would find exceptions to some of the laws of physics.

I know those sentences were next to each other, so I could have separated the flow of my thoughts a little better.

I thought causality was something not-as-well-proven as it currently is (because the history of QM always explains lots of interpretations where causality is broken). However, I stand corrected on that point :)

> making trades in the past

The other posters' comments on QM are off the mark, this bit of TFA was a joke about special relativity.

If you can transmit information faster than the speed of light, there is an inertial reference frame in which that communication travels backwards in time, violating causality. (If the traders and the exchange are roughly comoving you won't see this effect, of course.)

Another indicator of the article's quality: The company is called Metamako[0], not Metamoko.

[0] https://www.metamako.com/

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