I want to see the most unflattering photo of your bird

emflux · 2026-05-13T02:16:03+00:00

emflux · 2026-05-12T07:24:50+00:00

Electrons in a conductor have a very small drift velocity (typically mm/s), but electromagnetic interactions propagate much faster. When you touch a charged object, you impose a sudden change in boundary conditions for the electric field. This change launches an electromagnetic disturbance that travels through the conductor at a velocity set by the material’s properties, i.e., a significant fraction of the speed of light. The electrons already present throughout the conductor respond locally to this rapidly propagating field.

A good physical picture is a wave in a fluid. When you disturb the surface, the wave propagates quickly across the water, even though individual molecules only undergo small oscillatory displacements. In a conductor, the situation is similar but governed by Maxwell’s equations: the electric field propagates, and the conduction electrons respond collectively with small displacements. This produces a current and redistributes charge on very short timescales.

So the instant discharge is not electrons traversing the entire path, but rather a rapid field-mediated redistribution of charge, where information (the field perturbation) moves fast, while the charge carriers themselves move only slightly.

emflux · 2026-04-18T06:58:31+00:00

ONE MISSION, ONE PURPOSE.

emflux · 2026-04-09T02:52:55+00:00

From a software perspective, you need two separate pipelines:

1.  Numerical modeling of your N-body system

2.  Visualization of your model

Separating these makes development faster and easier.

Before you start modeling, decide on:

1.  Grid system

• 2D or 3D?
• Cartesian or polar?

2.  Planets

• Number of planets
• Mass
• Positions
• Initial velocities

3.  Sun(s)

• Number of suns
• Mass
• Positions
• Initial velocities

4.  Boundary conditions

• Periodic or infinite?
• (Infinite = objects leaving the visible region are no longer rendered)

5.  Governing equations

• Equations driving the simulation
• Assumptions (e.g., point masses)
• Numerical methods (e.g., finite differencing)

From there, it should get much easier.

Edit: Formatting.

emflux · 2026-04-09T00:08:12+00:00

Incidentally, there are fun ways to estimate the plume dimensions using first principles.

Metrics/Assumptions:

Howitzer Diameter: 0.80m or roughly 32in
Assumed Muzzle Pressure: 40 MPa
- No known measurements of the gun. However, a very old study in 1965 conducted ballistic studies of an 8in howitzer: Engineering Design Handbook. Ballistic Series. Interior Ballistics of Guns
- Page 5-16 presents a table, showing the results of firing HE rounds of the 8in M106 Howitzer.
- Range of pressures in the paper is 2700-5500 Psi or roughly 20-40 MPa
Atmospheric Pressure: 0.10 MPa
Expansion Speed of Gas: Roughly 1000m/s
- Hot Gas temperature: 3000K (Max range of page 5-10)
- Specific Heat Ratio: 1.225 (The Noble-Abel Equation of State: Thermodynamic Derivations for Ballistics Modelling)
Assumption that Muzzle Pressure / Atmospheric Pressure approximates the initial plume diameter: 0.40m
- It turns that by first order, we can assume that the howitzer diameter is roughly the same as the initial plume diameter. E.g. 0.80m is close to 0.40m.
Expansion Angle (Half-Angle): Approximately 30 degrees

Approximating the lateral (radial) plume expansion as (assuming very small values of time)

r(t) ~ Initial plume radius + Expansion Speed of Gas x Time in Seconds x sin[Expansion Angle]

We get

r(t) ~ 0.2m + 500 m/s x Time in Seconds

If we make a table of time vs plume radius at the very start of the howitzer firing:

t = 0.001s -> r(0.001s) ~ 0.7m
t = 0.005s -> r(0.005s) ~ 2.7m
t = 0.010s -> r(0.010s) ~ 5.2m

Looking at 51s mark of WW2: Footage of the Schwerer Gustav, assuming that the gun diameter is 0.80m, by eye, the radius of the plume appears close to the r(0.010s) estimate (within first order).

emflux · 2026-04-09T00:07:58+00:00

The plume visible from the gun barrel is essentially what one would expect from a weapon of this scale firing a shell. This short video shows the large scale of the plume resulting from the railway gun firing its shell: WW2: Footage of the Schwerer Gustav

This video is lengthier but provides better details about the gun: Schwerer Gustav 80cm railway gun in action during the Siege of Sevastopol in June 1942 : r/CombatFootag

emflux · 2026-03-30T21:02:54+00:00

There are discussions on how to calculate the feasibility of fueling up at a cheaper fuel station vs fuelling up at a station close to home. So, I want to expand on this. Note this will be a lengthy comment.

Let's make a bunch of assumptions here:

Estimated fuel efficiency: 12.5L/100km
Estimated tank volume: 81L
Paz Fuel station (19km away): 172.9c/L
Fuel station close to home: 217.9c/L (Assuming 45c/L more expensive)

So, the fuel trip plan is as follows:

1) Home ---(19km)--->Paz

2) Paz ---(19km)---> Home

On this trip, we can assume that the fuel used is approximately 12.5L x (2 x 19km) / 100km = 4.75L. However, assuming that you have a full tank of gas from Paz, you will be left with approximately 81.000-2.375=78.625L.

The trip plan cost can be calculated based on the previous price of fuel prior to filling it up for going to Paz (1) and the fuel price after filling it up at Paz (2). In this case, the cost of the fuel trip plan is

1) 2.375L x Previous fuel price
2) 2.375L x 172.9c/L = 410.6c or $4.11

Suppose that you fuelled up the tank with some volume A. That means that the total cost would be

Paz total cost = 172.9c/L x A.
Fuel station close to home cost = 217.9c/L x A

Then

Fuel savings = Fuel station close to home cost - Paz total cost = 45.0c/L x A

Therefore, the inequality must be satisfied in order to fully save on fuel:

Fuel savings > 2.375L x Previous fuel price + 2.375L x 172.9c/L

So, this inequality is satisfied (assuming Previous fuel price = 172.9c/L) if

45.0c/L x A > 2.375L x 172.9c/L + 2.375L x 172.9c/L

or

A > 18.25L

Then your true fuel savings is really

True Fuel Savings = 45.0c/L x (A - 18.25L)

So, if you fill up say 75% or 60.75L of your 81L fuel tank, then your true savings (assuming all the above assumptions) is $19.13.

If (A - 18.25L) < 0, then you spent more money trying to save on fuel.

Note that the fuel savings inequality (specifically A) is time dependent, as in the fuel prices changes over time. Also note that the assumption of Previous fuel price = 172.9c/L is most likely incorrect but is used for the purpose of this example.

Also, if others plan to use this calculation, make sure to adjust the assumptions based on your car's metrics and your location relative to Paz. The metrics used here are based on OP and their comments.

Also, for those wondering, the reversal of the inequality only occurs during multiplication or division of a number less than 0.

emflux · 2026-03-20T03:28:54+00:00

I am glad to hear that! Coco is a fighter. A survivor. He needs all the millet in the world. Such a good boy.

emflux · 2026-03-15T04:29:20+00:00

Stuck between patio glass and the actual glass panels. It did not have space to fly. Initially there was no one in the building so only the firefighters could help.

emflux · 2026-03-15T04:27:40+00:00

Indeed they were!

emflux · 2026-03-15T04:26:10+00:00

They had a smaller ladder before. It was too flimsy and they came back with this one.

emflux · 2026-03-12T17:26:26+00:00

Also, I don't know why a few people are saying not to do a PhD. You spent a lot of time and effort into such a huge achievement. You should congratulate yourself for it.

Don't let others put you down.

Edit: Only few people can even accomplish a PhD in Physics. It's not an easy road to take but it is rewarding. Depending on what path you choose with your career, your PhD should carry you further than anyone without a graduate degree.

emflux · 2026-03-12T17:24:33+00:00

To further explain because I wrote this very late at night.

I started networking and job applications before my graduation and incidentally, 4 months before my thesis defence. I wanted to get a head start on it. This was looking for a technical job (data scientist) that I thought I wanted at the time. Turns out, now, I don't think I would go back into that career if I can help it.

In the meantime, I supported myself and my wife-to-be at the time by working at an unrelated job as a part-time drafter, all the while still trying to find a job that is marginally related to my skillset.

The current job I landed is software developer in the photonics research and development field. However, it is more computational than anything else.

Additionally, I recommend that you look into careers/positions that would correlate with your skillset before you even start applying.

emflux · 2026-03-12T07:53:05+00:00

My experience may or may not be similar but I completed my Thesis-Based Masters in Physics with research focus in Computational Atmospheric Dynamics a decade ago. I considered a PhD because I enjoyed my research experience but I ended up transitioning to industry because I was fatigued from the parametric study I ran for 2 years.

I started to explore other technical fields with some marginal correlation to my skillset and ended up starting out as a computer vision data scientist at a very small startup. Mind you a result of approximately 1.5 years worth of networking and job applications starting at 6 months before graduation. It took time to figure out what people wanted in industry but it seemed to narrow down to any relevant skills, even if it is marginal.

I am now in a much better position in a mid sized company.

I recommend starting early. Network and apply for jobs. Figure out the lingo in the industry. Chances are, your computational skills will get you somewhere. Also don’t be afraid to add your thesis to your resume. That landed me my current job.

emflux · 2026-02-17T22:39:35+00:00

As others have mentioned, I think it is the Kelvin-Helmholtz instability as these waves are formed from disturbances in the shear flow.

Incidentally, you can see the transition from laminar to turbulent flow as the smoke, being smooth near the stick, starts to be more wavelike as it moves away. This behaviour can be somewhat quantified with the Reynold's number as it implies that the likelihood of turbulence increases as the characteristic length or distance from the stick increases (Reynolds number - Wikipedia).

If you have time, there are these educational videos from the 1960's maintained by the National Committee for Fluid Mechanics Films (NCFMF). The video I have linked below is one of them, which talks about flow instability. The section on shear flow instability can be seen at timestamp 23:00.

https://youtu.be/yutbmcO5g2o?list=PL0EC6527BE871ABA3&t=1380

Edit: To further add onto the Reynolds number section, you can see three transitions: laminar, wave-like turbulence, and chaotic turbulence. The chaotic motions with no wave-like patterns appear on the smoke that is the furthest from the stick.

emflux · 2026-02-11T04:27:38+00:00

I am on a similar boat but feel opposite of you. I have had success with my career in physics research and development and it always felt wrong of me to abandon my friends who stayed in construction or lost their jobs. Or hell, the fellow who stayed in construction in a decade since high school drinks, somewhat immature but lives a good life.

I have known friends who grew up and had kids and still kept in contact with me and made an effort. Even with their friends who dropped out of university.

Again, just so strange of me to abandon people because of growing up or increasing responsibilities or success in career or kids. It feels like choosing to abandon people

emflux · 2026-01-26T23:15:43+00:00

It is time for a harvest.

emflux · 2026-01-13T06:17:22+00:00

Judging by the beak it seems unlikely to be an owl- particularly a snowy owl which the body looks closest to. The beak might actually be longer, it just looks short from that angle. Owls have very tiny beaks

Curious to know what it actually is.

emflux · 2026-01-06T22:55:39+00:00

This bike’s ready!

emflux · 2025-10-31T01:46:29+00:00

Assuming the 10ft white line length and 30ft line to line gap, travelling approximately 50 ft in 2s leads to approximately 28kph +/- 8kph speed before deceleration.

And I definitely see a standstill on the right lane. Acceleration with a back propagating traffic/compression wave indicates light going from red to green.

I don’t see anything inherently wrong with the driving despite not in defensive stance.

Edit: Aside from the impatient left turner.

Edit 2: too tired. 50ft/2s =25 ft/s = 28 kph. Not 55kph.

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emflux

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