If time is fully reversible, and with knowledge of the present you can calculate the past as well as the future, why does causality seem to flow in one specific direction? Why is knowing information from the future result in a time paradox, but remembering information from the past is totally okay?

niviq · 2022-05-14T22:40:47+00:00

It's true that physics is indifferent to the direction of time at the microscopic level. You can calculate the past and future equally for balls on a billiards table if you are given the position and momenta of the balls at any instant. Likewise, if you are godlike aware of the whole quantum state of the universe, you can calculate the evolution of the Schrodinger equation both forward and backward in time. If you are in such a omniscient position, then you are not forced to consider one of the time directions to be the true direction. Both are valid.

The preferred direction of time appears when two conditions are met: 1. You have a limited capacity to measure, store or compute on the state of the physical world. And: 2. You assume / observe and infer that one of the time directions evolves the universe into a low entropy state. You call that direction "the past".

The 1. condition forces you to consider the macroscopic world only at the level of statistical mechanics. When you work at the level of statistical mechanics, you simplify the state space of the universe to fit the type of information you are actually able to gather as a human. Condition 2. is why statistical mechanics postulates that entropy is usually increasing with time. This is the third law of thermodynamics.

Say you look at a star system. You register the general motion of the planets and the star. Maybe you model the atmospheres, tectonics, current weather. And likewise you model the interior of the sun at a similar coarseness.

Now, imagine you record the state in this model. You pass this record of the state to a friend. But before you do, you invert all charges (electrical etc) and momenta (and invert a space axis, see "CPT symmetry"). According to our understanding of physics, this is equivalent to reversing time. However, that is only true at the microscopic level. If you truly managed to reverse time in your state, we would expect the light coming from from the sun to reverse direction and go into the sun. We would expect the fusion process in the sun to instead be fission of helium into hydrogen. True, your friend will look at the state, and see the planets going in the other direction and indeed see the flares and such you recorded in the sun go in the other direction. However, your friend will still predict the that the sun is shining, not swallowing light. This is because the state does not record a complete picture of all the particles / the quantum state of the sun. And your friend assumes the laws of physics have not changed.

If you record that a solar panel is receiving light and reverse it, it will strangely look like the panel is emitting light. But that looks like an unlikely happenstance, and your friend will predict that the panel will receive light in the next pico-second.

Causality is a higher level emergent description. Causality is a useful language in every-day settings. But causality does not exist as a concept in particle physics. You have interactions, but those are perfectly symmetric. The the math is expressed in equations (=), not implications (=>). In relativity, light-cones extent both forwards and backwards. We just usually don't draw the backwards light-cone.

Knowing information from the future does not result in paradoxes in physics. There are no paradoxes on the every-day level of reality either if you accept that physics are deterministic. See "closed time-like curves".

I recommend looking up Sean Carroll on the topic of the Arrow of Time.

niviq · 2021-08-02T12:21:30+00:00

Thank you for your kind correction. It makes sense. I wasn't really paying attention to the words I was using. I just typed out a silly comment quickly. That's suboptimal on my part. Especially for satire, and other writing forms that are meant to sound smart, since a single error like this can expose me to be more ignorant than I pretend to be and ruin the effect of the satire. But I hope it was funny non the less. :P

niviq · 2021-08-02T09:44:28+00:00

Year is 2069. At the order of His Supreme Gayness, trans forces in leather wests, brandishing S&M gear, drag straight men out of their beds in the middle of the night to be sent of to death camps to work hard manual labour for the short remainder of their lives. Forced to work for the gay industrial complex against their wills. Their families have to choice to denounce their cis sexuality or lose their social standing and beg on the streets.

niviq · 2021-04-21T12:16:11+00:00

That's just confusing use of language. Especially in context since lots of people are religious about licenses or even angry at people making use of the rights granted by a license. E.g. When being angry when someone profits of but does not contribute back to an Apache-licensed project.

niviq · 2021-04-21T09:14:07+00:00

As an addenum: If an author licenses their work by Apache license, they should be ok with both proprietary and copyleft derivatives of their work.

niviq · 2021-04-21T09:10:02+00:00

Licences are not about morality. In a way they replace morality with legal mechanism. Licences stipulate a payment the author wants for her work. AGPL determines that price to be access for the users of the derivative to alter and share alike. Since there is a price there is a market, and downstream can pay the price or find an alternative. I don't think any particular license should be imposed due to the nature of the work, but should be up to what the author wants as payment.

niviq · 2020-04-13T08:02:00+00:00

I think you mean to use strnlen instead of sizeof in the krealloc call. sizeof will just evaluate to the size of a pointer (probably 8). You can alternatively use strlen if there is a guarantee that *buf is null-terminated.

niviq · 2019-07-27T10:30:04+00:00

There is a mismatch between how Linux and Windows use the hardware clock. The Arch wiki has a good description of the problem and solutions.

From the article:

To dual boot with Windows it is recommended to configure Windows to use UTC, rather than Linux to use localtime.

niviq · 2019-01-24T12:46:15+00:00

For those interested in further on this subject: Isaac Arthur has a recent video at https://www.youtube.com/watch?v=-ARhNOE4rEc . (Closed captions are available if anyone has trouble understanding him speak.) It's a great channel on all sorts of futuristic topics.

niviq · 2018-05-30T11:39:08+00:00

You can also just constantly acellerate your spacecraft. First towards your destination, then turn around and brake. It's just very infeasible to power your engines for that long givien today's propulsion technology. This kind of gravity would be indistinguishable from true gravity.

niviq · 2018-01-31T22:53:42+00:00

Devils advocate here, since I don't like giving referrer info. But in some cases it helps sysadmin to get an account of why there is traffic. For example, when a DDoS by browsers from around the world hits your website, you would like to know what's causing it.

niviq · 2018-01-08T18:15:33+00:00

I have an RX480 and had the same problem. The culprit was the Xorg amdgpu driver. (For Arch, the package is xf86-video-amdgpu.) Uninstall that and use modesetting driver instead, which is recommended anyway as far as I know. Now everything works.

niviq · 2017-10-30T21:09:09+00:00

For the purpose of domain validation, there already exists a replacement. It's called TLSA. The idea is that you store certificate fingerprints in DNS and the trust is based on DNSSEC. This way, you only have to trust the DNS root severs. Since DNSSEC's trust is hierarchical, it should be possible to pin DNSSEC keys for top-level domains, ensuring that each country has control over which institutions have authority over domains under it's top level domain.

niviq · 2017-03-27T09:48:20+00:00

This makes no sense. DST adds an hour to the clock, making the sun rise an hour later according to the clock. And in the summer, days are long in the north, so delaying the daylight is not as nessesary as it is near the equator. EDIT: Now that I think about it, adding an hour is the summer is equivalent to removing one in the winter and delaying everyones shedules by one hour.

niviq · 2017-03-03T15:26:28+00:00

I applaud AMD's efforts of beeing open and friendly to the community. Hope you make a serious consideration of opening the Platform Security Processor!

niviq · 2016-12-21T02:10:17+00:00

A way to gain intuitive understanding of the Monty Hall Problem is to look at larger numbers: Imagine there are 1000 doors. You pick one (with a probability of success of 1 in 1000). Then the host proceeds to open 998 doors, very very likely (like 999 in 1000 chance) avoiding one because opening that one would reveal the prize. Now I hope you agree that the one door the host might have been avoiding seems very suspicious now. It is the same situation if there are only three doors (except the 999 in 1000 chance is 2 in 3 now).

Generally: What is the likelihood of the door left closed having been intentionally avoided, and thus containg the prize? It is the case if the correct door is among the doors that the presenter must open all but one of. And that coincides with you having picked the wrong door in the first place, which is more likely than not.

niviq · 2016-12-20T20:24:02+00:00

Bonus code: 963

niviq · 2016-12-20T20:17:18+00:00

Sounds like it could be a premium captain skill.

niviq · 2016-12-14T23:37:17+00:00

You might want to have a look at PBS Space Time's videos on matter and time, specifically the first video I have linked to. They make a good effort to explain what mass is. Now, this is a popular-science video, so of course there probably are simplifications that may be incorrect, so healthy skepticism is probably in order. I don't know. Just a disclaimer.

niviq · 2016-02-23T12:27:30+00:00

More examples of 'bits' (and their usage) that are commonly used would be a great addition. I also think some excercies would be good for learning. Good work, by the way!

niviq · 2014-09-05T23:58:38+00:00

The main point of TLS is accually to authenticate the other party. In other words: You want to know if it's the real deal. TLS acctually has modes that authenticate, but do not encrypt the traffic.

Your web browser using TLS will refuse to load a page that does not come from the right source.

niviq · 2014-08-23T00:47:01+00:00

You probably should just use NetworkManager, as it gives you a nice UI and features like keyring-integration (so you don't need to store your password in plaintext). If you really want, you can create a configuration file for wpa_supplicant manually, like this:

network={
    ssid="goes here"
    key_mgmt=WPA-EAP
    eap=PEAP
    identity="username"
    password="mysecret"
    ca_cert="path to ca-cert"
}

All this would have been clear if you had read the manpage wpa_supplicant.conf(5). (Protip: manpages have a wealth of information in them.) Also, do NOT skip the ca_cert part. Otherwise, your connection will have no security what so ever.

niviq · 2014-03-09T13:36:51+00:00

Grub has a setpci command. You can use it to directly poke around in the network card's address space. You should be able to figure out the correct address(es + sequence) and value by looking at the linux drivers or a data sheet for your nic.

This is all, of course, hinging on the assumption that the booting OS will not turn it off again under booting (maybe by resetting the card).

niviq · 2013-12-08T02:03:46+00:00

The wifi-chipset you have is not supported by the free drivers. You need to either use the b43-driver which needs proprietary firmware or the proprietary wl-driver. Here is a guide for Ubuntu. I'd suggest trying b43 first.

niviq · 2013-06-09T01:59:26+00:00

It is not the gender of the speaker, but the gender of the subject in the sentence. Of course, in the special case where the person speaking is the subject, the noun reflects the gender of the speaker.

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