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I am sure no one will crush these parking spot saving robots it will be fine.

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I am sure no one will crush these parking spot saving robots, it will be fine.
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Submitted November 19, 2018 at 08:19AM by ssnapier
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Firefox debuts experimental price-tracking feature for consumers

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Firefox debuts experimental price-tracking feature for consumers
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Submitted November 13, 2018 at 04:15PM by motang
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Doing the maths properly: why the Overwatch world definitely isn't in danger.

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Doing the maths properly: why the Overwatch world definitely isn't in danger.

So I read through this post and saw that he was doing things wrong! Because Duty Calls, I had to correct them, and slept no more than the recommended amount of <4 hours in the process -_-. The first day, that is (I may or may not have spent an entire week on this post, only to correct some random person on the Internet). It may also have something to do with that OP got 16k upvotes for not doing math, so i may be able to get... 7? upvotes for doing things properly.

Most calculations can be found in this spreadsheet.

So anyway, what do we know?

Measurements

My FOV is 103°, which results in an actual FOV of 90° because Overwatch is weird. My screen is 1920px wide, which makes the pixel radius 960px. I took screenshots of the Moon from Dorado and of the Earth from Horizon Lunar Colony as you can see here. The Moon height over horizon from Earth was such that the moon just touched the top of my screen, so the radius is 1080/2=540px.

Object Pixel radius
Moon 70.5px
Earth 323px
Screen 960px
Moon height over horizon from Earth 540px
Earth height over horizon from Moon 259px

We also know the radius and mass of the OW earth from these screens on Horizon.

Pixels and angles

We are interested in the angular radii of all our objects, but we only have the sizes in pixels. So how do we convert between the two?

We can visualize the situation with this figure where x_o is the pixel radius of the object, ɑ_o is the angular radius of the object, x_s is the screen radius and ɑ_s is the angular radius of the screen, which is half the FOV, so 45°.

If we remember our trigonometric functions, we notice that

 tan(ɑ_s) = x_s / z z tan(45°) = x_s z = x_s (Because tan(45°)=1) 

We can also use tan to calculate ɑ_o:

tan(ɑ_o) = x_o/z ɑ_o = atan(x_o/z) 

Using this formula on the known pixel widths, we get this table:

Thing Pixel radius Angular radius
Moon radius 70.5px 4.20°
Earth radius 323px 18.60°
Screen horizontal radius 960px 45°
Moon height over horizon from Earth 540px 29.4°
Earth height over horizon from Moon 259px 15.1°

Because I will use it later, also note that cos(x + 90°) = -sin(x) and that sin(x + 90°) = cos(x).

Where things get complicated

First of all, the symbols I’ll be using are:

Thing Symbol Unit
Moon radius x km
Earth radius r km
Moon angular radius α_m °
Earth angular radius α_e °
Moon height over horizon from Earth h_m °
Earth height over horizon from Moon h_e °
Earth gravity g_e m/s2
Moon gravity g_m m/s2
Earth jump duration t_e s
Moon jump duration t_m s
Latitude of Dorado φ °

Our situation is this figure where E and M are the center of the Earth and Moon respectively and that D and H are Dorado and Horizon Lunar Colony remember this, I will use it a lot. The lengths of f and g are derived from that

sin(ɑ_m) = x / f f = x / sin(ɑ_m) 

Using the law of cosines, we can write d2 in two ways: using the triangles △MED and △MEH. Moving things around, we get a quadratic equation. Solving this equation yields the value of x.

Now knowing x, d is now solvable using the law of cosines on either △MED or △MEH. (I used △MED in my spreadsheet.)

All this yields the following table:

Thing OW Real Ratio (Real/OW)
Moon radius 1203 km 1737 km 1.444
Moon-Earth distance 16428 km 384400 km 23.4

Acceleration, mass and gravity

The position of an object under constant acceleration is s = 1/2 a t^2 + v_0 t. Plugging in the numbers at the end of the jump on Earth:

v_0 t_e + 1/2 g_e t_e^2 = 0 v_0 + 1/2 g_e t_e = 0 (dividing by t_e) v_0 = -1/2 g_e t_e 

Plugging in the numbers at the end of the jump on the Moon yields:

 1/2 g_m t_m^2 + v_0 t_m = 0 1/2 g_m t_m - 1/2 g_e t_e = 0 (substituting in v_0) g_m t_m = g_e t_e (multiplying by 2 and adding by g_e t_e) g_m = g_e t_e / t_m 

Using Newton’s law of universal gravitation and Newton’s second law:

F_g = gm = GmM/r^2 g = GM/r^2 M = gr^2/G 

Plugging in the numbers yields:

Thing OW Real Ratio (OW / Real)
Moon gravity 2.43 m/s2 1.62 m/s2 1.5
Moon mass 5.270e16 kg 7.342e22 kg 1 / 1 400 000

The rest of the maths

Using the law of sines, we can calculate φ, the latitude of Dorado, remembering our figure:

sin(φ) / f = sin(h_m + 90°) / d φ = asin( cos(h_m) f/d ) 

which turns out to be ~44.78756°, which is around the latitude of Minneapolis, US or Bordeaux, FR. Not exactly Mexico...

Anyway, the thing OP thought was the big deal. Tidal acceleration is calculated using the formula 2 G m r / d^3, so calculating the effect of the moon on the earth and vice versa yields this:

Tidal acceleration on OW Real Ratio of OW/Real
Earth 5.338×10-9 1.10e-6 1/206
Moon 0.1142 2.44e-5 4680 this isn't good

The effects

As you might imagine, the Earth will be just fine with only having smaller tides: basically the exact opposite of OP:s conclusion. The Moon is in bigger danger, but it will probably just result in tidal heating (albeit a lot of it) instead of something cataclysmic, but I really do not knowScott Manley plz. I don’t know what else to say really, I can’t make an anticlimactic conclusion more interesting. But it was totally worth it just to say that OP was incorrect.

TLDR:

The Earth is definitely not in danger, but Mexico is in Minnesota.




Submitted November 11, 2018 at 05:14PM by Megafish40
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@thatbrianlee https://t.co/NbybfMB7WH

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November 05, 2018 at 03:26PM
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Hotel of Wireless Horror

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Hotel of Wireless Horror

Do you like to read in Chronological order? Here is the Index

 

$Selben: Me! At the time a recently appointed Tier II helldesk helpdesk technician for a mid-sized company, very skeleton-crew helpdesk 10 of us total for 24 hour coverage (not including supervisors) to support 2500+ company-wide.

$Sup1: Previously in sales no IT background and causes more issues than they solve.

$VP: VIP of the sales team.

$Buddy: Local IT... Buddy.

 

Thunder sounded, and lightning flashed, causing the lights to flicker and create shadows on the high ceilings. An older styled chandelier clinked as it swayed from the breeze of doors opening and closing. The room had that strong odor you get when too many people are in the same place B.O., mixed with stale coffee.

$Selben was at the entrance of the room. He was sitting behind a rickety collapsible table supplied by the hotel. $Sup1 had created a banner for the table: “Meet and Greet IT!” in Comic Sans. $Selben shuddered as he tried to take another sip of the stale coffee-like brew, but set it back down, the burnt taste making his tongue recoil. The $Company was having a sales conference and $Sup1 had come up with the idea to have someone from IT be there to have a “presence” and introduce some upcoming plans. Unsurprisingly, it had turned into everyone asking for IT support. $Selben was alone so he had to tackle them all on his own.

User after user kept coming up, but he finally got a break when the actual meeting started. With only stale bagels and burnt coffee around, $Selben was just waiting for it all to end. His countdown to escaping was interrupted when the doors opened back up and one of the sales VPs approached him.

$VP: The internet on my laptop stopped working. I need the slides in my email!

$Selben: No problem. Let me take a look—uh, what is this?

$VP: Oh, this is my “Travel” laptop!

$Selben: Oh... I see.

The machine was more than several years old, and in dire need of the embrace of death a reinstall, more memory and a modern processor, at least. Out of the corner of $Selben’s vision, he saw several other users walked towards the table, but left when they saw that $Selben was busy. The machine crawled. A password prompt came up, and the $VP snatched the machine and mashed in his password. A prompt to restart also appeared on his screen, and like an infuriated bull he clicked 'restart' before $Selben had time to react. After what felt like an eternity (5 minutes), the machine finally rebooted, and he was able to determine what was wrong.

$Selben: It looks like the hotel's Wi-Fi is down, we'll need to let them know.

With that, $Selben hurried over to the front desk and asked to speak with their IT department. The front desk was insistent everything was working fine. $Selben pointed out she was wired directly to the network and had to explain that the wireless network was separate. Eventually he managed to get her to call, and their local IT appeared instantly from around the corner.

$Buddy: Hey bud! Let’s look and see what we can do.

$Selben: I just need you to reboot the wireless, it’s not working.

$Buddy: I'm not getting any errors. Let’s go look at your machines, maybe you’re on the wrong network.

$Selben's eye twitched

$Selben: I'm...

$Selben bit his lip and showed him $VP's laptop, which he had brought with him.

$Buddy: Oh, okay, I see whatcha mean, bud!

$Selben's eye twitch intensified.

$Buddy: Okay, it’s rebooted. You should be good to go!

$Selben: Thanks.

$Selben returned to his spot to find 15 angry zombies salesmen all standing around where his table was. It was laying broken on the floor, with a pile of laptops on and around it. Apparently, they all had network issues (which were now resolved) and had brought their laptops to the IT table. Seeing $Selben gone, they started piling them on top of the table. The collapsible table did exactly what it was (debatably) designed to do, and collapsed. Three screens were lost in the fall.



Submitted October 31, 2018 at 03:22PM by Selben
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My heart just can't handle this level of cuteness

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My heart just can't handle this level of cuteness
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Submitted November 01, 2018 at 04:14PM by armadillo-rodeo
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