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Monday, December 17, 2018

Happy Wright Brothers' Day, 2018

Wright Brothers' First Flight, December 17, 1903

On December 17th, 1903, the Wright Brothers, Orville and Wilbur, became the first people to achieve an accomplishment that people had been dreaming of for millenia - controlled, powered flight. Now, they weren't lone geniuses working in a vacuum. Others had had earlier limited successes, and people would have figured everything out eventually even without the Wrights (and were largely on the path to doing so, since the Wrights kept so much of their own research a secret), but the Wright brothers had a systematic, logical approach, putting them years ahead of their contemporaries. When they gave their first public demonstrations in France in 1908, crowds were awestruck. They certainly deserve the honor of being the first to flight.

To quote myself from a previous entry, "Flying has become so common place today that we take it for granted. People complain about the cramped seats, the long lines to get through security, the bad food (if you even get any) on flights. But just remember how long people have dreamt of flight, for how long people looked to the skies wanting to emulate the birds. Flying used to be the stuff of myth and legends, reserved for the gods. Now, we can all get in an airplane, and soar above the clouds. It really is something special."

Here are a few of the better aviation related pages/entries on this site that would make for good reading for Wright Brothers Day. The first entry on the last is brand new today.

So as you go about your business today, take a moment to look up and find an airplane, and marvel a little at the achievement.

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Much of the content of this entry was recycled, sometimes verbatim, from previous Wright Brothers Day entries.

Responding to a Flat-Earther Question: How Much Force Does It Take to Accelerate an Aircraft Sideways as It Flies North-South

In honor of Wright Brothers Day, I'm going to post an aviation-themed entry today. This entry started life as a comment on Quora, in response to a flat-earther. The most interesting aspect of the comment thread was a question the flat-earther raised that I'd never really thought about quantifying before.

If you think about the globe spinning, the equator has the highest velocity, going through one rotation per day. The poles have basically zero velocity, being just spinning about a point (from an earth-centric reference frame, at least).

Earth Rotation Diagram

So, if an aircraft flies directly north-south (or vice versa), in order to remain over the same line of longitude, it's sideways velocity has to change - it has to accelerate sideways*. And that means there has to be a sideways force. Just from experience, you know intuitively that it's a negligible force, but can we quantify that? How much of a force are we really talking about?

The flat-earther actually proposed a good thought experiment to think about the issue. Suppose there were a giant merry-go-round, the same diameter as the Earth, spinning at the same rate of 1 rotation per day. If you started at the center of the merry-go-round, you would have zero sideways velocity. If you walked outward on a straight line painted on the merry-go-round, your sideways velocity would start to increase, keeping matched with the merry-go-round. By the time you got to the edge, your sideways velocity would be quite high - close to 1000 mph.

So, let's actually use the merry-go-round thought experiment to determine the necessary forces. The results will be at least in the right order of magnitude, and it makes the math a whole lot simpler than trying to model all this on a globe.

So, here's a diagram of the scenario. You've got a merry-go-round spinning at some rotational velocity, ω. You have an object moving outwards on that merry-go-round at some radial velocity, Vr. That object, because it's on the merry-go-round, will also have some tangential velocity, Vt.

Figure 1

Our goal is to find tangential force, Ft, which is going to be defined by tangential acceleration, at, so we need to find changes in tangential velocity. So, let's let that object travel for some time, t. In that time, it will cover a certain radial distance, dr, which is obviously just defined by dr=Vr*t.

Figure 2

At the first point, 1, it will have a tangential velocity Vt1, where Vt1=ω*R1. And at the second point, 2, it will have a tangential velocity Vt2, where Vt2=ω*R2. Okay, I think that's got all the definitions taken care of. On to the equations:

R2 = R1 + Vr*t

ΔVt = Vt2 - Vt1
ΔVt = ω*R2 - ω*R1
ΔVt = ω*(R1+Vr*t) - ω*R1
ΔVt = ω*R1 + ω*Vr*t - ω*R1
ΔVt = ω*Vr*t

at = ΔVt/t
at = ω*Vr*t/t
at = ω*Vr

Ft = m*at
Ft = m*ω*Vr

So, things simplified quite nicely, where you don't need to worry about where exactly you are on the merry-go-round. All that matters is how fast the merry-go-round is spinning, and how fast the object is moving radially.

Let's calculate one more value, tangential load factor, nt, which is the g's the object will experience in the tangential direction, and is simply the tangential acceleration, at, divided by the regular acceleration due to gravity on Earth, g. Note that this is only dependent on speeds, not masses.

nt = at/g
nt = ω*Vr/g

Now, let's plug in some numbers, going through an example step-by-step. Let's consider a 200 lb person walking briskly at 5 mph (I'm an engineer in the U.S., so I usually stick with ft, lb, seconds, and the like). So first, rotational velocity, ω, will be one revolution per day, which works out to 6.94e-4 rpm, or 7.272e-5 rad/s. The person's mass is found by converting pounds to slugs, and since m = W/g, we get 200 lb / 32.2 ft/s² = 6.21 slugs. And their speed is 5 mph * 5280 / 3600 = 7.33 ft/s. So, we just plug those into the equations:

Ft = m*ω*Vr
Ft = (6.21 slugs)*(7.272e-5 rad/s)*(7.33 ft/s)
Ft = 0.0033 lbs

nt = ω*Vr/g
nt = (7.272e-5 rad/s)*(7.33 ft/s)/(32.2 ft/s²)
nt = 1.656e-5

To summarize, for a 200 lb person walking briskly at 5 mph, the tangential force required to accelerate them as they walk outwards is only 0.0033 lbs, or 1.656e-5 g's. That force is about equivalent to the weight of 5 staples (according to this discussion, at least). That's really, really negligible.

Let's add a few more cases, but instead of going through all the math step by step, again, let's just put the results into a table.

Person, 5 mph Car, 60 mph 747, 570 mph
ω, rev/day 1 1 1
ω, rpm 0.000694 0.000694 0.000694
ω, rad/s 7.27E-05 7.27E-05 7.27E-05
Vr, mph 5 60 570
Vr, ft/s 7.333333 88 836
Wt, lbs 200 4000 735,000
m, slugs 6.21118 124.2236 22,826.09
at, ft/s² 0.000533 0.0064 0.060796
Ft, lbs 0.003312 0.794974 1387.726
nt 1.66E-05 0.000199 0.001888


Those are all small accelerations, and correspondingly small forces (at least in relation to the size objects). Obviously, the acceleration goes up as tangential velocity goes up, but even at the 570 mph speed of a 747, the radial acceleration is still less than a hundredth of a g.

Granted, the actual magnitude of the force on the 747 looks big enough to be somewhat appreciable, but remember to keep it in comparison to size of the aircraft - 1388 lbs of side force on a 735,000 lb aircraft. To further put the force in perspective, keep in mind that if the aircraft weighs 735,000 lbs, the wings have to create that much lift. So, to get 1388 lbs of side force, the aircraft would have to be banked just 0.11°, since arctan(1388 lbs / 735,000 lbs) = 0.11°. Another way to look at it is in comparison to the engine thrust. Since a 747 has an L/D of around 15.5, that means a drag of around 47,400 lbs, and an equal thrust from the engines to counter that. Even if you completely ignored aerodynamic means of accomplishing the side force, it would mean skewing the thrust just 1.7° off of the flight path. These are very small numbers.

And, keep in mind, we simplified things with a giant merry-go-round, which is actually worse than everywhere on Earth except 2 precise locations. The only locations matching this are at the poles, where the surface actually is perpendicular to the rotation axis. Everywhere else, the surface is more angled relative to the rotation axis. Right at the equator, this force/acceleration drops to zero. All latitudes in between will have force/acceleration values somewhere in between this worst case and zero.

So, an object traveling north-south on a spinning globe does indeed have to have some side force to account for the changing tangential velocity. And while we may know intuitively that the force has to be negligible, it's nice to be able to break out the math to calculate what it would need to be.

Spinning globe image source: zaleta.pbworks.com
All other diagrams by author

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*All this actually applies any time traveling north-south, not just directly north-south along a line of longitude. I was just keeping things simple for the sake of discussion.

Friday, December 14, 2018

The Big Christmas Post, 2018

Christmas TreeChristmas is less than two weeks away, so it's about time to get up my now annual Big Christmas Post. I've written quite a few Christmas related entries over the years, and posted various comics and memes, so I've decided to gather up links to all the best stuff into one post. I know this is recycling, but it's still good stuff, especially if you've never read it before.

 

Jolly Posts

AOPA Christmas Card A Plane Christmas Greeting
This is a poem written by my late Uncle Bud. We both shared a love of aviation. This is his version of "The Night Before Christmas" (or "A Visit from St. Nicholas" for you pedants), with an aviation twist.
  
Koch Fractal Snowflakes An Early Christmas Present - Koch Snowflake Christmas Ornament 3D Printer STL Files
Last year, I played around with making snowflake ornaments for my 3D printer. But since I'm a nerd, they couldn't be any old snowflakes. These are fractal snowflakes.
  
White Wine in the Sun Merry Secular Christmas 2018 - Buy White Wine in the Sun, Support Autism Charity
I have a tradition of posting a video of this song every year around Christmas. This year was no exception. Go give it a listen, and donate to the autism charity, Aspect, while you're at it.

 

Curmudgeonly Posts

Santa in the Crosshairs War on Christmas
This was my first War on Christmas post. It covers a bit of the history of Christmas in the U.S. ("a nightmarish cross between Halloween and a particularly violent, rowdy Mardi Gras"), the Pagan origins of so many modern Christmas traditions, and in general why it's silly to get upset over an imagined War on Christmas.
  
Santa is no more Yes, Virginia, There Are Liars
I've never particularly liked lying to kids about Santa Claus, nor the whole mindset around Christmas time that kids should suppress their doubts and critical thinking skills. Playing pretend with kids is one thing, but lying is something else.
  
Scrooge When Happy Holidays Isn't Good Enough
This was an incident a few years ago that still stands out in my mind - a Salvation Army worker getting physically punched for wishing somebody a 'happy holidays' instead of a 'merry Christmas'. I included a meme that shows the appropriate response to any holiday greeting.
  
Take that, Santa Unintentionally Hilarious War on Christmas Video
Well, this could go into Jolly or Curmudgeonly depending on how you want to take it. This was a video I came across this year from a extreme right wing website - so extreme that I had to do a double take to verify it wasn't parody. Anyway, the video was so over the top that I couldn't help chuckling over it.

 

Should I Donate to _____ Charity?

Since so many people start thinking about donating to charity around the holidays, here are a couple entries on charities.

Salvation Army? The Salvation Army - To Give, or Not to Give?
As much as they try to portray a completely wholesome image, the Salvation Army isn't without their controversies. I'm not actually going to advocate that you do or don't donate to them (but if you don't, please donate to somebody else), but you should at least understand some of the activities they engage in that you may not agree with.
  
Charity Debunking an E-mail on Charities
This was written in reply to one of those email forwards, decrying all the supposed waste from certain charities, and suggesting you donate your charity money to other, more worthwhile charities. Well, suffice it to say, since it was an email forward, it wasn't particularly reliable. Granted, it's been a few years since I've looked into each of these charities, but it still gives you a sense of how legitimate various charities are, and provides links to a few watchdog groups.

 

Christmas Memes & Comics

You may have to click to embiggen to read this one.
Calamities of Nature Comic on Charlie Brown Christmas
Source: Calamities of Nature (via the WayBack Machine)

 

Santa Jesus Meme
Source: Master Marf (no idea if that's the original creator)

 


Source: Meme Generator

 

You'll never see one of those cutout plywood nativities the same way, again:
Source: Scoopnest

 

Christmas Tree Image Source: Free christmas Tree Backgrounds

Merry Secular Christmas 2018 - Buy White Wine in the Sun, Support Autism Charity

In a yearly tradition for this blog, it's time to post one of my favorite Christmas songs, White Wine in the Sun, by Tim Minchin. But more than that, this is a chance to support Aspect, an Australian charity supporting children and adults on the Autism spectrum. For the past several years, Minchin has donated all procedes from sales of the song around Christmas time to the charity (previously known as the National Autistic Society - more info). So, if you don't own a copy of the song, yet, now's a perfect time to buy it.

If you've never heard the song, there's a description on Minchin's site from 2010 which reads, "This is a captivating song and a beautiful and intelligent exploration of why Christmas can still be meaningful even without religious beliefs. There's just the right amount of sentiment and some very gentle humour illustrating Tim's feelings about Christmas and the importance of family and home. It is a heart-warming song and may make you a little bright eyed."

So, with all that out of the way, here it is, White Wine in the Sun. And new for this year is a new(ish) recording of the song (new for this site, at least):

Also new for this year, I'm including the lyrics, if you want to read along (per Google, from an older recording):

I really like Christmas It's sentimental, I know, but I just really like it I am hardly religious I'd rather break bread with Dawkins than Desmond Tutu To be honest

And yes, I have all of the usual objections
To consumerism, the commercialisation of an ancient religion
To the westernisation of a dead Palestinian
Press-ganged into selling Playstations and beer
But I still really like it

I'm looking forward to Christmas
Though I'm not expecting a visit from Jesus

I'll be seeing my dad
My brother and sisters, my gran and my mum
They'll be drinking white wine in the sun

I don't go in for ancient wisdom
I don't believe just 'cause ideas are tenacious it means they're worthy
I get freaked out by churches
Some of the hymns that they sing have nice chords
But the lyrics are dodgy

And yes, I have all of the usual objections
To the mis-education of children who, in tax-exempt institutions
Are taught to externalise blame
And to feel ashamed and to judge things as plain right and wrong
But I quite like the songs

I'm not expecting big presents
The old combination of socks, jocks and chocolate's is just fine by me

'Cause I'll be seeing my dad
My brother and sisters, my gran and my mum
They'll be drinking white wine in the sun
I'll be seeing my dad
My brother and sisters, my gran and my mum
They'll be drinking white wine in the sun

And you, my baby girl
My jetlagged infant daughter
You'll be handed round the room
Like a puppy at a primary school
And you won't understand
But you will learn someday
That wherever you are and whatever you face
These are the people who'll make you feel safe in this world
My sweet blue-eyed girl

And if my baby girl
When you're twenty-one or thirty-one
And Christmas comes around
And you find yourself nine thousand miles from home
You'll know what ever comes
Your brothers and sisters and me and your mum
Will be waiting for you in the sun

When Christmas comes
Your brothers and sisters, your aunts and your uncles
Your grandparents, cousins and me and your mum
We'll be waiting for you in the sun
Drinking white wine in the sun
Darling, whenever you come
We'll be waiting for you in the sun
Drinking white wine in the sun
Waiting for you in the sun
Darling, when Christmas comes
We'll be waiting for you in the sun
Waiting

I really like Christmas
It's sentimental, I know

Thursday, December 6, 2018

Unintentionally Hilarious War on Christmas Video

Santa in the CrosshairsI was just curious if anyone was still going on about the 'War on Christmas', so I googled it, and came across an unintentionally hilarious video, from a site named, non-satirically, ChurchMilitant.com/. At first I thought something so over the top was surely a parody like Landover Baptist, but no, it has it's own Wikipedia page and everything. Anyway, I don't think I can embed the video here, so you'll have to go watch it on the site:

DECEMBER 6, 2018--WAR ON CHRISTMAS: The advance of atheism.

The 'surely this must be parody' stuff started off from the very beginning:

Hello and welcome to The Download, live from our Church Militant studios in Detroit, Michigan. I'm Christine Niles. And, happy Feast of Saint Nicholas, the manly saint who punched the priest Arias in the face, after Arias blasphemed our Lord and rejected His divinity.

Ah, yes, manly saints punching people in the face. None of that turn the other cheek bullshit that some beatnik hippy went on about.

Then the talking head started using all the right-wing cliches you've come to expect about atheists and liberals:

The heretic Arias brought his own war against Christ by rejecting that he was God. That war on Christ continues to this day, brought by secularists who hate Christ and everything he stands for, and try to mask that hatred behind political correctness, or arguments for separation of church and state, a phrase that never actually appears in the Constitution, by the way.

Just for the record, "Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof..." while not literally using the phrase 'separation of church and state' certainly seems to be saying that government should keep its nose out of the whole business. And the phrase was coined by a U.S. president, by the way.

The segment then went on to praise Donald Trump for his support of Christmas in the face of political correctness, and showed a clip of Trump from a rally. Now I admit, I hardly ever voluntarily watch Trump, since he hardly ever has anything worthwhile (or coherent) to say. So I guess I'm just not accustomed to his mannerisms. But my goodness is he hilarious. He's like a parody. At one point while the crowd was cheering, he literally winked at someone in the crowd and then did that sleazy lounge host pointing people out move, before doing an unintentional (I hope) Elvis imitation, and then finally moving on to a brave stance in support of the single most popular holiday in the country:

Thank you. Thank you very much. And something I said so much during the last two years, but I'll say it again as we approach the end of the year- You know we're getting near that beautiful Christmas season, that people don't talk about anymore. They don't use the word Christmas cause it's not politically correct. You go to department stores and they'll say happy New Year. They'll say other things. And it'll be red, they'll have it painted, but they don't say- Well guess what, we're saying Merry Christmas again.

Wow, what an act of heroism. I mean, it's not like 81% of non-Christians in the U.S. celebrate Christmas, including a majority of Buddhists, Hindus, religiously unaffiliated, and even a third of Jews (Pew - Christmas also celebrated by many non-Christians).

And yeah, those department stores are loathe to admit what all this 'holiday' shopping is about:

Oh, wait, I did find a page on Wal-mart called Ready, Set, Holiday!, that did have a whole bunch of 'holiday' references and not so many 'Christmas' references, at least until you actually followed any of the links or looked at any of the products being sold.

It's hard to believe this is the world we live in today - a clown like Trump in the White House, and right wing kooks making websites that are barely distinguishable from SNL skits.

Oh well, I'll take the unintentional humor as an early Christmas present. Merry Christmas everyone.

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For a bit of an entertaining read, check out the following TV Tropes page. It's not about this site, per se, but it definitely reveals the mindset:
TV Tropes - Church Militant

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