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## Comment: Re:Mass and Weight are different (Score 2)71

by necro81 (#43802099) Attached to: Rough Roving: Curiosity's Wheels Show Damage

Sure the vertical force on the tires is the same when standing still, but what about the force required to stop 342kg vs 900kg of inertia if you hit a large pointy rock at 1m/s?

That's what's referred to as dynamic acceleration. Rolling along at 1 m/s and then coming to a sudden stop by running into a rock would indeed produce some big accelerations, and the difference in mass between Curiosity and Scarecrow would be pretty significant.

However, the scenario that you and an earlier comment are talking about - coming to an abrupt, rocky stop from 1 m/s - simply does not happen. You might be envisioning Curiosity as some sort of Martian ATV bouncing off the landscape and doing power slides, but the reality is far more prosaic. Curiosity's top speed on flat, hard soil is about 0.04 m/s, not 1 m/s. Let's say that, for whatever reason, Curiosity came to a dead stop from it's top speed in, say, 100 ms (the suspension ensures the stop is not instantaneous). That's an acceleration of 0.4 m/s^2. The static acceleration due to gravity on Mars is 3.7 m/s^2, or about 10x that.

What is more: Curiosity has about a dozen people planning out its path, specifically to avoid running into things. Even beyond that: Curiosity has hazard avoidance cameras and autonomous algorithms that will slow or stop it before it hits anything.

## Comment: Re:Mass and Weight are different (Score 2)71

by necro81 (#43801901) Attached to: Rough Roving: Curiosity's Wheels Show Damage

The problem with this is that Curiosity weighs 342kg but masses 900kg. Scarecrow weighs and masses 342kg. Whatever Curiosity weighs, it hitting a rock at 1m/s is still 900 newtons of force. Scarecrow hitting a rock at 1m/s is 342 newtons. The fact it drove 12km and has serviceable wheels does not make me feel better.

That distinction is really only revelant in the case of dynamic loading: hitting things at speed, rapid straightline accerelation, or quick turning. Whether Curiosity on Mars or Scarecrow on Earth, there really isn't any of that going on. For the most part, the only loading going on is the static loading due to gravity, which they have accounted for.

You talk about hitting a rock at 1 m/s, but Curiosity's top speed on hard, flat ground is 1.5 in/sec, or about 4 cm/sec (0.14 km/h). That's only 1/25th the speed you use in your bungled calculations; 1/625 as much kinetic energy. At that slow crawl of a speed, the difference in dynamic loading between Curiosity and Scarecrow is negligible. In any event, the rover is by an large prevented from hitting anything by the route planners here on Earth and its autonomous hazard avoidance algorithms.

In other words: I trust the engineers at JPL to understand these things and account for them better than a random user on /.

## + - Transporting a 15-m, 600-ton Magnet Cross Country

Submitted by necro81
necro81 writes "Although its Tevatron particle accelerator has gone dark, Fermi Laboratory outside Chicago is still doing physics. A new experiment, called muon g-2 will investigate quantum mechanical behavior of the electron's heavier sibling: the muon. Fermi needs a large ring chamber to store the muons it produces and investigates, and it just so happens that Brookhaven National Laboratory outside NYC has one to spare. But how do you transport a delicate, 15-m diameter, 600-ton superconducting magnet halfway across the country? Very carefully."

## Comment: Re:Why not just 0? (Score 4, Insightful)985

by necro81 (#43730475) Attached to: NTSB Recommends Lower Drunk Driving Threshold Nationwide: 0.05 BAC

But you're right, we do think so little of mass shootings that we refuse to regulate the access to firearms. And we are absolutely correct to do so. 100 deaths per year in a country of 300 million is negligable.

Although mass shootings get all the headlines, controlling access to firearms will save a whole lot more than 100 lives per year. Most of the savings will come from reduced accidental deaths and suicides.

There is a widespread belief that having a gun in the house makes you safer: this is not true.

In the 1990s, a team headed by Arthur Kellermann of Emory University looked at all injuries involving guns kept in the home in Memphis, Seattle and Galveston, Tex. They found that these weapons were fired far more often in accidents, criminal assaults, homicides or suicide attempts than in self-defense. For every instance in which a gun in the home was shot in self-defense, there were seven criminal assaults or homicides, four accidental shootings, and 11 attempted or successful suicides. source

(other sources along those lines)

There is also a widespread belief a person who dies from suicide would have done so no matter what method: this also is not true. Most suicide attempts are impulsive acts, and most are unsuccessful. An impulse act with pills or slit wrists is unlikely to succeed: it takes time, the person may have second thoughts, and usually recovers through medical and psychological treatment. A suicide attempt by a gun is much, much more likely to succeed. If that suicidal person did not have ready access to a gun, and had to resort to a different method, the changes are good that most (i.e., more than 50%) of those people would still be with us today.

## Comment: Re:Moronic (Score 1)339

by necro81 (#43708979) Attached to: Ad Exec: Learn To Code Or You're Dead To Me
Or you could do like most working stiffs and brown-bag it: make a simple lunch at home and bring it to work with you. Most of my lunches consist of leftover dinners, which I cooked, or a simple sandwich, which I made at home in about three minutes. To prepare and cook a nutritious 8-serving meal, from scratch, takes only slightly longer than the same meal made for 4.

My time is important to me, and I'd rather spend it enjoying my meal, making leisurely use of my lunch break, or making productive use of that time, rather than waiting in line in the cafeteria or a food truck. The notion that my time is important to me extends to the kitchen, too: I enjoy the time I spend cooking for myself and my family, it is time that is valuable to me, not a chore that I begrudge. My money is important to me, too, and bringing lunch costs me about 1/4 what it would to buy it each day.

## Comment: Re:Lolzers. (Score 1)193

by necro81 (#43656651) Attached to: Using YouTube For File Storage
Unfortunately, I don't think you could count on steganography. YouTube transcodes, resizes, and manipulates the raw video fifty ways till sunday - whatever information you've stored in the frames could easily be lost or corrupted. What is more, you have to worry about playback problems: dynamic bitrates, dropped frames, and the like. By the time you add in all the checksums, error correcting code, and other data to make the system robust, you'd probably end up with a 10-minute video just to transmit a few hundred bytes of data. You'd do better to do something clever with the subtitles.

Steganography works quite well when you have access to the actual file, preferably in its entirety. This technique might even work under controlled conditions. But I seriously doubt that one could make it work robustly in the real world. (If you want to consider that a challenge and prove me wrong by making it work, by all means.)

## Comment: Re: Not to mention... (Score 2)455

by necro81 (#43644137) Attached to: Why Your New Car's Technology Is Four Years Old

A decent amplifier with powered USB fed DAC and a way to provide various horizontal docks for a variety of handheld devices would be cool. I don't really need much beyond that. A tablet with 64 gb or 128 gb solid state storage makes for a decent mobile AV system

Soooooo, you're looking for an iPad and about \$50 of accessories to patch it into your car? You could wander down to a big box store and get yourself outfitted today for less than the cost of a typical OEM car stereo.

## Comment: Re:Not to mention... (Score 1)455

by necro81 (#43644107) Attached to: Why Your New Car's Technology Is Four Years Old

Take a consumer SSD and put it in a deep freeze to -50C look it still works!

When the 2013 model year cars were being designed 4-5 years ago, consumer SSDs barely existed.

## Comment: Re:Orbital pickup truck (Score 2)204

by necro81 (#43591157) Attached to: Helium Depleted, Herschel Space Telescope Mission Ends
Thank you for bringing in the Blade Runner reference - very appropriate. Take it to its logical conclusion...

"I've seen things you people wouldn't believe....All those moments will be lost in time, like tears in rain. Time to die."

## Comment: Re:Figures they'd do the liver first (Score 1)62

by necro81 (#43546107) Attached to: Device Keeps Liver Alive Outside Body For 24 Hours
The liver is used to living at the tail end of the circulatory supply, after all the other organs have gotten their share. Plus, one of its main jobs is detoxifying the blood, so it can put up with higher levels of contaminants in the blood. In other words, if you are testing out an organ-sustaining machine, and you can't guarantee that you can keep the blood pristine, the liver is a pretty good choice for trying things out.

## Comment: Re:Wait a minute (Score 2)62

by necro81 (#43546077) Attached to: Device Keeps Liver Alive Outside Body For 24 Hours
It is good if you can keep it alive, because it keeps it viable for transplant to a dying patient for longer. So keeping the liver alive longer means more people receive transplants, so more people live longer, fuller lives.

## Comment: Re:Answer not in summary (Score 1)308

by necro81 (#43535159) Attached to: Cause of LED Efficiency Droop Finally Revealed
Actually, if they could form Cooper pairs, to the point where it becomes superconductive, it would be f&%\$ing awesome!

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