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Comments

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The Quiet Before the Next IT Revolution

idji Wrong (145 comments)

No, you IT people are no longer the great revolutionists - your time is gone. You are now just plumbers, who need to fix the infrastructure when it are broken. Other than that, we don't want to hear from you, and we certainly don't want your veto on our business decisions - that is why a lot of us business people use the cloud, because the cloud doesn't say "can't work, takes X months, and I need X M$ to set it up", but is running tomorrow out of operational budget.

about a week ago
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The Technologies Changing What It Means To Be a Programmer

idji Re:Another Silver Bullet? I don't think so... (291 comments)

The most useful programming skills I learnt were in 1982 on the Sinclair ZX Spectrum. Nothing I learnt then has become irrelevant, just the languages changed. I give programming courses and am amazed how 21st century programmers are missing the basics and cannot write algorithms.

about a week ago
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Rosetta Achieves Orbit Around Comet

idji Re:In Orbit? (54 comments)

The comet 67P has a mass of 3.14E12 kg
Today the comet is 186,444,271 km from the Sun Where is Rosetta?
Using F=GMm/R^2, the Sun's gravity on Rosetta is equal to 67P's gravity on Rosetta at 700m from the center of Rosetta on 6 August 2014, which means that Rosetta will never really be completely within 67P's field. (At Perihelion on 13 Aug 2015, 67P's gravity field will be as strong as the Sun's only 250m from the centre) However, now that Rosetta is in the same orbit as 67P we can mostly disregard the Sun's gravity and the elliptical path that Rosetta and 67P now share as of today. (Earth's pull on Rosetta is at least a million times weaker than the Sun's pull - so forget any influence from the Earth's mass.)

The "orbits" at 100km are called hyperbolic because Rosetta is not trapped in 67P's gravity well since the gravity is so weak and because Rosetta is still moving FAST at 1 m/s. But this hyperbola is so weak it is effectively a straight line.
Rosetta will turn 60 degrees after every 100 km of a hyperbolic path to make a triangular "orbit". This triangular path cannot be called an orbit because it is not a conic section, nor is the comet at a focal point of the conic section Kepler's First Law.

These "straight"/"hyperbolic" paths of 100km and 50km are deliberately done for two reasons:
-to calculate exactly the gravity field of the comet, because it is clearly not a uniform sphere. They will likely use radar&cameras to continuously measure the precise distance to the comet
-to keep in front of the comet to avoid its coma and tail.
After these maneuvers, Rosetta will go into a 30 km "orbit", so that the task of mapping 80% of the surface all happens from the same distance. This orbit is not natural and will be powered because a natural 30km orbit of 67P takes 26 days.

Here's how to calculate the natural circular orbits for 67P (it won't be circular, because of the crazy shape, but close enough). Kepler's 3 Law gives us
T^2=4pi^2/GM*r^3. 4pi^2/GM=0.19 for this comet. G=6.67×1011 N(m/kg)2
if r=30km=3e4m, the natural orbit would have a period of T=2.3e6 seconds=26.11 days
If r=2.5km, the natural orbit would have a period of T=15 hours
If r= 5km, the natural orbit would have a period of T=1.77 days
If r= 100km, the natural orbit would have a period of 159 days So I could imagine that when Rosetta gets within 5km it is mostly using the natural orbit and hence saving fuel.

about two weeks ago
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Gmail Recognizes Addresses Containing Non-Latin Characters

idji Re:Dammit this is a terrible idea (149 comments)

It would be easy to WARN a USER if the name contains mixed alphabets or diacritics that differed from the user's browser's preferred language. Each Unicode Character has a name eg "Greek Upsilon With Hook Symbol", or "Latin Capital Letter R", or "Cyrillic Capital Letter Es With Descender", "Arabic Letter Qaf", or "CJK Ideograph" for Chinese/Korean/Japanese.

about two weeks ago
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Comparison: Linux Text Editors

idji Re:What's there to compare? (402 comments)

it has no code explorer, showing you the function names

about three weeks ago
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Tesla and Panasonic Have Reached an Agreement On the Gigafactory

idji Re:What makes this a gigafactory? (95 comments)

go and look at the PICTURE on TFA and you will see they want to make 35GWh/yr (35 GIGAWATT HOURS PER YEAR) of cells by 2020. So Gigafactory is quite appropriate.

about three weeks ago
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NIF Compresses Diamonds With 50 Million Atmospheres of Pressure

idji Re:Car analogy? (81 comments)

during the impact.

about a month ago
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Sand-Based Anode Triples Lithium-Ion Battery Performance

idji Re:Launch date (60 comments)

please unsubscribe from "news for Nerds". We are here for news, and we are nerds, we want new ideas.

about a month ago
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Physicists Spot Potential Source of 'Oh-My-God' Particles

idji Re:Ooh, ooh, I have a bogus theory (144 comments)

because the annihilation particles are all well known and have MUCH less energy than these particles.

about a month ago
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Police Using Dogs To Sniff Out Computer Memory

idji Re:Amazoing (415 comments)

lots of chemicals are used in making/etching circuit boards and then there is the tin&flux in solder. I am sure they have very clear smells.

about a month and a half ago
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Air Pollution Can Disrupt Pollinating Insects By Concealing the Scent of Flowers

idji Re:Easy fix (67 comments)

http://www.honeycouncil.ca/chc...
Bees need to fly twice around the word (50,000 miles) and visit 2.6 million flowers to make 1 pound of honey.
Your robots are not coming to save us any time soon.

about 2 months ago
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New Chemical Process Could Make Ammonia a Practical Car Fuel

idji Re:Now I'm confused ... (380 comments)

They have just found a cheap way to crack NH2 to N2 and H2 and are excited about that in combo with simpler fuel storage and transport - they are not focusing on the energetics of H2 or NH3 generation with the Haber-Bosch process here.
The point here is that to store Hydrogen you need 10,000 psi (http://en.wikipedia.org/wiki/Hydrogen_storage#Compressed_hydrogen) and Ammonia only needs 250 psi in a plastic container (http://en.wikipedia.org/wiki/Ammonia#Storage_information).
They are looking at the following problem
H2O+Energy->H2->H2-Storage->FuelCell->Electricity+H2O
and have worked out that they can do
H2O+Energy->H2,+N2+Energy->NH3->NH3-Storage->H2 +N2 without NOx->FuelCell->Electricity +H20
and what they are excited about is that NH3 storage and transport is a known and solved problem industrially and NH3 cracking is now cheap and clean. Now someone just needs how to work out H2O->H2->NH3 using solar and the problem is solved.

There is also the other issue that a H2 leak is benign or a quick fireball and that an NH3 leak will eat the noses and lungs of everyone nearby.... http://www.wral.com/ammonia-le...

about 2 months ago
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Elon Musk: I'll Put a Human On Mars By 2026

idji Re:At least Elon has the right goal (275 comments)

Going to Mars won't save humanity, but working out how to live away from Earth could, even if that means learning on Mars how to live under the Earth to survive the 1450's imps, 1950's Apocalypse Godzillas and 2010's Biotech Zombies...

about 2 months ago
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Unicode 7.0 Released, Supporting 23 New Scripts

idji Re:Why emoji? (108 comments)

If the emoji are standardized in Unicode, then it will be easier for any kind of software to support them.

about 2 months ago
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Dump World's Nuclear Waste In Australia, Says Ex-PM Hawke

idji Re:Commodity of the future (213 comments)

Look at Safety Advantage #11 Destruction of existing long lived wastes in LFTR What is wrong with my periodic table?

about 3 months ago
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Dump World's Nuclear Waste In Australia, Says Ex-PM Hawke

idji Re:Commodity of the future (213 comments)

exactly, burn it all in the Thorium reactors to come.

about 3 months ago
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NASA's Plan To Block Light From Distant Stars To Find 'Earth 2.0'

idji Re:Wrong focus (92 comments)

NASA is focusing on research and new tech as it should and Starshade is an excellent example.
NASA shouldn't do an orbital shipyard and asteroid hauling - that is engineering - let SpaceX and Google do that in private enterprise.

about 3 months ago
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US College Students Still Aren't All That Interested In Computer Science

idji Re:I have tried (306 comments)

it's no parlour trick. For tasks like navigating down through an xml file, parsing boolean phrases like "a and (c or (d xor e)))", searching a folder system, navigating a tree, implementing Qucksort Algorithm, Towers of Hanoi, giving change with coins, etc have NO STACK OVERFLOW issues
Show me smarter ways of solving these problems.
A while loop can have a stack overflow if you forget to increment a counter. That's just bad programming - it doesn't mean a while loop is bad.

about 3 months ago
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US College Students Still Aren't All That Interested In Computer Science

idji Re:I have tried (306 comments)

In the last 16 months I ran workshops around the world for over 200 technical consultants working for IT companies. Less than 10 of them would be able to write recursive or sort functions or other problem-solving algorithms. Most of them were what I call "configurers". A massive amount of the problem-solving burden falls on me because i learnt how to program in the 1980's before the internet and code libraries appeared.

about 3 months ago

Submissions

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How did the Moon move so far in one day?

idji idji writes  |  more than 4 years ago

idji (984038) writes "Saturday morning I woke up at 7am and looked out my south-facing window (48N) and saw the moon BEHIND a tree. Sunday morning I woke up at 8am and looked out my south-facing window. No surprise that the Moon was there. But what blew me away was that the moon wasn't behind the tree, it was ABOVE the tree, about 8(!) moon-diameters higher in the sky. I have studied planetary science, the orbit of Mercury and can derive Kepler's 3 Laws from F=ma on the back of an envelope but I didn't have an explanation for what I saw — I skipped that observational Astronomy class at university — too much trigonometry. Orbit of the Moon didn't help me either. Can any one out there explain how the Moon was 8 diameters higher in the school AFTER 25 hours?"
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idji idji writes  |  more than 7 years ago

idji writes "Astronomers meeting in the Czech capital have voted to strip Pluto of its status as a planet. About 2,500 were in Prague for the International Astronomical Union's (IAU) general assembly. Pluto has now been demoted to a pluton — transneptunian — kuiper belt object — whatever you want to call it. http://news.bbc.co.uk/1/hi/world/5282440.stm"

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