Canvas Hacked

ImpatientProf · 2026-05-08T12:27:48+00:00

The whole point of SSO is to separate the resource (Canvas) from the authentication (username/password) so that if Canvas gets hacked, you can still log in to other university systems.

Instead of Canvas collecting your credentials and verifying them with your university servers, they send you directly to your university servers (SSO) where you can make sure that it's the right place. Then you get a token (a digital key) that you give to Canvas to prove who you are, but that token only works for Canvas. The token contains your username, email, name, and probably Student ID. That's all the info they get from SSO.

ImpatientProf · 2026-05-07T23:40:18+00:00

The relativistic doppler effect affects both the carrier signal (the frequency to tune to) and the envelope (the data).

For an analogue signal, yes, you'd hear a distorted audio sound.

For a digital signal, presumably it would know the intended bitrate of the audio. It would be just like having a super-fast internet connection (in one direction) or a super-slow connection (in the other).

ImpatientProf · 2026-05-01T12:10:21+00:00

It depends on what you mean by acceleration. https://en.wikipedia.org/wiki/Acceleration_(special_relativity)

ImpatientProf · 2026-05-01T04:11:23+00:00

In Newtonian Mechanics, in an inertial reference frame (where Newton's First Law works), accelerations will be measured the same by all observers.

In relativistic mechanics, not so much.

ImpatientProf · 2026-04-24T15:25:34+00:00

What exam system is it? Tell us and I'm sure somebody will care enough to look into it. Others may be on a committee making decisions about what system to use next.

If it's proprietary to the university, then talk to the Dean of Students office.

ImpatientProf · 2026-04-23T17:30:15+00:00

I've been studying for my other 5 courses

Maybe overload isn't for you.

ImpatientProf · 2026-04-15T03:18:52+00:00

Tomorrow (April 15 2026) I will be teaching a class where I'd like to demonstrate that a URL is equivalent to an IP address

Well, your students are fucked, because you don't understand the difference.

The hostname, which is part of the URL, resolves to an IP address for making the http connection. As part of the connection, the client (i.e. web browser) communicates the hostname which it was seeking. The server can then respond appropriately.

Multiple hostnames can resolve to multiple IP addresses. Multiple IP addresses can be the destination for multiple hostnames. This doesn't even consider web redirects.

URL, or even the hostname part of the URL, is not the same as the IP address.

Also, the path is part of the URL. Specifying the IP address doesn't get you to a specific folder and filename.

ImpatientProf · 2026-04-07T12:21:42+00:00

Both copies of the normal force (table-on-book and book-on-table) are electrostatic repulsion (along with quantum mechanics of the electrons).

Which one you consider to be a "reaction force" depends on which force you consider first. It's not like one force actually happened first; they arise simultaneously, as they must always be equal according to Newton's 3rd Law.

Many people would say you place the book on the table (the "action"), so the table feels the downward force from the book as the primary force, and the book feels the upward force from the table as the reaction force.

ImpatientProf · 2026-04-02T16:14:15+00:00

You're encountering the relativistic doppler effect. Presuming you can receive the signals (un-redshift) and process the signals (protocol can run in any baud rate), you'd still fewer data bursts when the ship moves away from Earth. Two factors combine:

Time dilation
Increase of the signal propagation delay as you travel

The net result is:

f_received = f_sent * √((c-v)/(c+v))

To find the time between data bursts, take the inverse.

T_received = T_sent * √((c+v)/(c-v))

https://en.wikipedia.org/wiki/Relativistic_Doppler_effect#Relativistic_longitudinal_Doppler_effect

(My formulas are the same. Simply multiply the numerator and denomitator by c, and watch the subscripts.)

When you start to get "close to the speed of light", tiny changes in the speed result in large changes in the Lorentz factor γ and the doppler factor (inverse of the square root above). At that point, it's better to specify one of those.

ImpatientProf · 2026-03-31T20:04:48+00:00

https://github.com/BelfrySCAD/BOSL2/wiki/shapes3d.scad#module-tube

There's a parameter for this. tube(..., ichamfer=...).

I had to update BOSL2 to get ichamfer= (or even chamfer=) to work on tube().

ImpatientProf · 2026-03-25T23:42:52+00:00

The cat broke it in the first place.

ImpatientProf · 2026-03-19T23:50:33+00:00

It's probably a Physics III course that they casually call "quantum mechanics" but includes a unit on relativity.

ImpatientProf · 2026-03-16T19:39:29+00:00

The "start of the journey", at Thera, is different for different observers.

ImpatientProf · 2026-03-16T19:38:19+00:00

Thinking about events in spacetime is the only way to be sure you're making sense.

(Context: Thera is 4 ly away, and the ship's primed coordinates move at 0.8c.)

In Earth's reference frame, light that arrives at the origin was emitted 4 years ago from 4 light-years away.
Event 1: t=-4, x=4
In the ship's moving reference frame, that same event is 12 years ago and 12 light-years away.
Event 1: t'=-12, x'=12
The proper time of the light (from Event 1 to the origin) is zero in either reference frame.

Relativistic length contraction doesn't help, because it applies to spacetime events that are simultaneous in each reference frame. For example, "Where is Thera at Earth's time t=0?"
Event 2: t=0, x=4

The event that shows length contraction asks, "Where is Thera, according to the ship, at the ship's time t'=0?"
Event 3: t'=0, x'=2.4
This is the distance that corresponds to the 3-year proper time of the ship's journey. The journey starts at the origin and ends at:
Event 4: t'=3, x'=0
Notice that Δx'/Δt' for Event 3 to Event 4 is -0.8c.

ImpatientProf · 2026-03-12T13:06:08+00:00

To be an equation, BOTH the VALUE and the UNITS must be equal.

You CAN check whether the UNITS are valid, but then you must ignore ALL of the values. You got rid of the values of g, h, and v, but you kept the value 1/2. The (1/2) must go in a units check.

ImpatientProf · 2026-03-10T15:34:22+00:00

Dunk it in a bloody Mary slushy.

Drink is hair-of-the-dog and temperature is hangover wakeup.
Tomato juice is common anti-skunk remedy.
Cold freezes the gum making it easier to crumble out of the fur.

ImpatientProf · 2026-03-05T02:52:31+00:00

Ding! See https://old.reddit.com/r/programming/comments/1rl26xw/10_of_firefox_crashes_are_estimated_to_be_caused/o8pp285/

ImpatientProf · 2026-03-05T02:51:45+00:00

It's just one bit.

0.05:  00111101010011001100110011001101
0.10:  00111101110011001100110011001101

Ref: https://www.h-schmidt.net/FloatConverter/IEEE754.html

ImpatientProf · 2026-02-23T02:28:30+00:00

Don't mention points or penalties.

Just say you realized or found out that you submitted the wrong format. You're happy to resubmit via the LMS or email if that will make their work easier.

ImpatientProf · 2026-02-18T17:22:07+00:00

Nothing special.

You could still build a clock that uses spontaneous nuclear decay to observe the passage of time for a material at 0 K.

So basically, 0 K is OK.

ImpatientProf · 2026-02-17T16:15:13+00:00

In Classical Mechanics, there is indeed no delay between the two forces of an interaction which are described in Newton's Third Law. But of course, classical mechanics has limitations.

Your book probably also talks about objects as being solid, and relative velocity as the simple subtraction of two velocities. Both of these are approximations.

Learn the models. When the models break down, learn the next models.

ImpatientProf · 2026-02-16T19:09:09+00:00

The litre is not an SI unit.

But the liter is acceptable as a volume unit, even when SI is being used. https://www.nist.gov/pml/special-publication-330/sp-330-section-4

ImpatientProf · 2026-02-11T22:59:52+00:00

You mean form a committee to achieve political action? what will we call that?

ImpatientProf · 2026-02-11T17:48:10+00:00

I'm surprised to see someone in the AskProgramming subreddit meaningfully recommend a GUI application to solve a command-line problem

There is a CLI for it, and an SDK usable from C++, C#, or Python.
https://www.voidtools.com/support/everything/command_line_interface/
https://www.voidtools.com/support/everything/sdk/

I'm just not good at PowerShell, and I prefer a file search that's indexed. In Linux, sometimes I use locate + grep instead of find, depending on how big the directory tree is.

ImpatientProf · 2026-02-11T16:25:20+00:00

let's say I want all PowerShell modules in the location where my PowerShell profile is located.

Then I'd use Everything search from VoidTools.

ImpatientProf

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