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/sci/ - Science, Technology, Engineering, and Mathematics

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There's a new /777/ up, it's /gardening/ Check it out. Suggest new /777/s here.

Movies & TV 24/7 via Channel7: Web Player, .m3u file. Music via Radio7: Web Player, .m3u file.

WebM is now available sitewide! Please check this thread for more info.

A nice initiative Anonymous 15/01/09(Fri)20:44 No. 16024 ID: c7d0c5 [Reply]

File 142083267722.jpg - (8.75KB , 100x100 , 7moon.jpg )

It's nice that this emerging site tries to introduce progressively the mathematics and the science at the people.
we hope that they follow other chapters, as they promise on their home page.

how to make airplane Anonymous 15/01/04(Sun)17:37 No. 16019 ID: 61d208 [Reply]

File 142038945866.jpg - (548.56KB , 1280x720 , F24F35.jpg )


Cryptoforums.net Technology Forum Cryptoforums.net Technology Forum 14/05/13(Tue)10:25 No. 15656 ID: 288b60 [Reply]

File 139996955137.png - (8.43KB , 82x77 , CF-logo.png )

Hello chans of the internet. We at https://cryptoforums.net have created a MyBB forum dedicated to the discussion of things like Bitcoin, Privacy, Security, Cryptography, GNU/Linux, Philosophy, Politics, Freedom, Cryptocurrency, Hacking and many other general subjects. We are currently in our early stages and we want to invite more members. If you like any of those subjects you should come check us out! We also respect anyone's opinion even if negative so give us all your positive/negative support/criticism!

7 posts omitted. Click Reply to view.
Anonymous 14/08/11(Mon)18:38 No. 15815 ID: d9f5aa

the joke's getting old, shillfag.

OP your forum would be a lot more appealing if it didn't require an email.
trashmail makes it easy but waiting for the email to arrive is a fucking dealbraker.
I'd probably rather enter a fucking google recaptcha and have my everchanging dynamic IP logged by some useless waste-of-money agency than wait for a shitty activation mail (and possibly still get logged if my ISP or trashmail provider is sharing data as much as google does).

Anonymous 14/08/11(Mon)18:39 No. 15816 ID: d9f5aa

>>15662, not 199869 obv.

Registration requires captcha, but none displayed for me Anonymous 15/01/02(Fri)05:55 No. 16015 ID: 226b1d

I've tried to register on cryptoforums three times tonight, using Opera, FireFox, and IE. In all three browsers, I agree to the terms, populate the fields, and submit the form, to be greeted with:

Please correct the following errors before continuing:
•The image verification code that you entered was incorrect. Please enter the code exactly how it appears in the image.

There is no captcha image to enter. There's a question to answer, which I answered correctly each time.

Is the new user registration broken, or am I the only one having this issue?

Also, your Contact Us mailto link is broken. It contains no email address. Ergo, I could find no way to reach a site administrator, hence the post here.


Anonymous 13/07/18(Thu)15:31 No. 15206 ID: 9083c1 [Reply]

File 137415428455.jpg - (94.22KB , 640x569 , turkey_roast.jpg )

I might sound like an idiot for asking this, but can somebody explain the science behind the following:

When you're grilling two steaks over a flame, it takes the same amount of time, whether it's just one or two steaks.

When you're roasting two turkeys inside an oven, it usually takes 1.5 to 1.8 times longer than when there's just one turkey inside.

Why doesn't it take the same amount of time as it does when grilling two steaks over a flame?

Why am I an idiot for not understanding this?

2 posts omitted. Click Reply to view.
CandleJack 13/07/23(Tue)22:45 No. 15220 ID: 2f260d


Ovens are not perfectly efficient. With the one turkey, say 50% of the energy goes toward heating it, while the remainder heats the air or escapes outside. With two turkeys, 75% of the heat goes to them, while the rest heats the air (which there is less of because the oven is more full) or escapes.

Have you heard how a full refrigerator is more efficient than an empty one? That's because it takes more energy to heat or cool air (and maintain it) than it does to heat or cool an object. It's just like that, but in reverse. Because there is less air in the oven, it doesn't waste energy heating that air; the conserved energy goes into heating the other turkey.

Anonymous 13/07/24(Wed)01:59 No. 15221 ID: 9083c1

Now I get it, thanks a lot!

Anonymous 14/12/30(Tue)20:13 No. 16012 ID: a607c9


Thats incorrect. It is a common misunderstanding that air needs more energy to cool down in a fridge than solid or liquid mass(like bottles full of water) does.
While it is true that a full fridge uses less energy than a empty one, that is only the case if you leave the solid mass inside. Air has a thermal capacity of roughly 1 J/gK (Joule per gram and Kelvin ). The thermal capacity of Water is very roughly 4 times higher. This means you would need 4 times the energy to cool down (or heat up) 1 kg of Water than 1 kg of air. A fridge is typically less than 200 liters big inside, which is 0,25 Kg of air. If you put something in your fridge which is at least 0,065 kg (or 65 g) heavy and mostly made of water, it will take more energy to cool down than if all the air inside the fridge would have changed.

So why is it still more efficient to have a full fridge than an empty one?
When you open the fridge there is normally no liquid or solid mass leaking. However the cold air is escaping even if you don't want cold air in your kitchen. Thus the air loss is energy loss. If you have a full fridge there is less air in it and therefore less air can escape.
Top-opening-freezers are more efficient because of that. Cold air is more dense (heavier) than warm air. The cold air stays in the top-opening-freezer while it floats out of a front-opening-freezer.

World's Simplest Electric Train Jeson 14/12/23(Tue)20:30 No. 16007 ID: 3791e5 [Reply]

File 141936303681.png - (512.38KB , 1459x468 , baterija.png )

The trick in the video is that the magnets are made of a conducting material and they connect the battery terminals to the copper wire, so the battery, magnets and copper wire make a circuit that generates a magnet field just in the vicinity of the battery. The geometry means the two magnets are automatically at the ends of the generated magnetic field, where the field is divergent, so a force is exerted on the magnets.

The magnets have been carefully aligned so the force on both magnets points in the same direction, and the result is that the magnets and battery move. But as they move, the magnetic field moves with them and you get a constant motion.

If you flipped round the two magnets at the ends of the battery the battery and magnets would move in the reverse direction. If you flipped only one magnet the two magnets would then be pulling/pushing in opposite directions and the battery wouldn't move.

What you need:
1. Neodyum magnets
2. Dry cell battery
3. Copper wire

World's Simplest Electric Train Jeson 14/12/23(Tue)20:38 No. 16008 ID: 3791e5


Seen this kickstarter, looks interesting... Anonymous 14/12/18(Thu)13:04 No. 16003 ID: 868e7f [Reply]

Youtube  A computer vision program:


Trying the demo version now

Anonymous 14/12/09(Tue)18:17 No. 15996 ID: fc1128 [Reply]

File 141814543148.jpg - (38.28KB , 549x673 , motizuki.jpg )

Are you ready for “Inter-universal Mellin transform”?


Remark 2.2.1

Mochizuki hopes to solve the Riemann Hypothesis too

Anonymous 14/12/16(Tue)03:56 No. 15998 ID: f6b29d

File 141869861769.jpg - (17.82KB , 300x375 , 1286043555673.jpg )


Anonymous 14/12/05(Fri)02:52 No. 15993 ID: 86e709 [Reply]

File 141774435457.jpg - (78.83KB , 1000x750 , formlabs-inline.jpg )

Welp, our rapid prototyping machine ist kill.

Time to get a 3D printer to use for moldmaking plugs.

Anyone have experience they'd like to share?

Sifted 14/09/26(Fri)02:55 No. 15892 ID: 96405d [Reply]

File 141169293046.jpg - (43.01KB , 290x399 , J8seKRxKdk6RNCK6ipzejQ2.jpg )

So for everyone out there I ask you what you think the universe would be like if attraction was different. If it was likes attract and opposites repulese, so two positive charges attract same with negative and then a positive and negative repulse. What do you all think?

3 posts omitted. Click Reply to view.
Anonymous 14/11/15(Sat)12:22 No. 15970 ID: c4fc35

My guess would be not much change at all in terms of how the universe works, entropy etc.

But would we exist in it? Probably not.

Effectively you are just switching the masses of electrons and protons. The atomic structure would remain relatively similar except for heavier electrons. Would this cause them to orbit much further from the nucleus? I don't know I'm not a physicist.

But yea, if atoms functioned similarly to how they do now then organic life would be very different. Depending on the properties of the new elements it would likely not be carbon based but rather a more suitable element

Anonymous 14/11/22(Sat)08:38 No. 15977 ID: abc87c

I think this was explored as a mathematical possibility in the early universe when antimatter still outnumbered matter a buttfucktruckload to one, and much weirdness abounded.

I forget what all went down but in short, that shit worked briefly, and then worked itself out. It... went away, OP.

Anonymous 14/12/01(Mon)17:08 No. 15992 ID: 972965

ITT: People not realising OP just asked "What happens if you reverse time"
>Reverse the big bang

Anonymous 14/07/25(Fri)22:51 No. 15766 ID: 86e709 [Reply]

Youtube  Everything I've read about Eugenics has been about how it's pseudoscience. Ok. but, by the sound of it, it was just a selective breeding program. If artificial selection works in every other species, and natural/artificial selection has produced us, ...where's the problem exactly? I have yet to see how a sophisticated selective breeding program couldn't produce a better human body or brain or both. It's what we do every time we pick a mate who we think will make us some primo offspring.

pic semi-related: Just try listening to this without clawing your eyeballs out (why are so many people so fucking retarded and how can we replace them with upgraded models?)

8 posts and 1 image omitted. Click Reply to view.
Anonymous 14/11/25(Tue)16:24 No. 15987 ID: e3615c

I think a better alternative would be like what appears in the movie Gattaca. You take many gamete samples from the future parents and fertilize them in vitro. You keep only the zygotes that meet certain criteria for health (optionally freezing a few in case of miscarriage or some other problem) and you implant one in the mother.

Anonymous 14/11/30(Sun)21:20 No. 15990 ID: 96b946

What about unintended consequences?

Like, for example," Oh hurray! We have bred sickle cell out of existence! But wait oh fuck now everyone is dying of malaria"

Or like how rainman idiot savants are a cunt hair away from being the next Issac Newtons.
Get rid of the retards, get rid of the possibility of greatness.

Anonymous 14/12/01(Mon)04:19 No. 15991 ID: 86e709

The downs side of that would be no greatness, unless, oh shit, a whole generation of autistic savants... because who cares, it eliminates war, and robots and androids unburden us from the shackles of menial tasks and physical labor, agriculture, maintenance, freeing us up to contemplate mathelamatiques and phirosophry and awwt aww day. They can all be sterile, finally uncoupling sex from our reckless primitive approach to reproduction, so people can mate purely for social purposes. Reproduction only happens when intended and it the parents are committed, stable, and financially sound to care for the young, in addition to engineered fetuses cleaner, healthier genomes.

Plus, bonus upside, all cunts can easily be hairless cunts.

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