1119: "Undoing"

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Re: 1119: "Undoing"

Postby stephen431 » Wed Oct 10, 2012 8:03 pm UTC

tomintx wrote:
mcdigman wrote:Whose fault is it if your driverless car runs thru a group of children crossing the road?


Apple Maps.

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Re: 1119: "Undoing"

Postby Pfhorrest » Thu Oct 11, 2012 12:03 am UTC

Vroomfundel wrote:This whole cycle will be broken when we start producing fusion power on an industrial scale - it will get kick-started by some of the conventional sources (gravity-powered) but once running it will be a self-sustaining chain reaction and it will probably be the first time in the history of the universe that energy is produced that isn't caused by gravity.

By what proposed mechanism would this magical source of free energy operate? If the fusion is not being initiated by gravity, but by some other process, the energy for that has to come from somewhere, and even if somehow that "somewhere" can be a mere portion of the fusion reaction itself (the problem with cold fusion is that it takes more power input to initiate the fusion reaction than we get out of it), if that's initiated by other (ultimately gravity-derived) sources of energy, how is that the resulting energy not indirectly cause by gravity? Gravity initiated fusion which powers life on Earth which (somehow) initiates more fusion and so on.
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Re: 1119: "Undoing"

Postby jc » Thu Oct 11, 2012 12:14 am UTC

phlip wrote:Viscosity is just resistance to flowing - it slows down the flowing of the tide, so it's slightly behind where the moon is, which in turn is what causes the tidal locking effects. Anything that slows down the flowing of the tide will add to that effect.

Lots of explanations draw the picture this way, but the fact is that the tide's peak precedes the moon's passage "overhead" (i.e. past your line of longitude) about an hour later than the tide's peak. The actual time difference depends on the local underwater terrain, of course, so the time difference varies at different locations.

The reason the tidal bulge races ahead of the moon is that the Earth is rotating a lot faster than the moon, in terms of degrees per hour. The Earth's surface moves 360 degrees (actually about 361 degrees) in a day; the moon moves about 12 degrees in the sky in that time. So the land under the oceans is "pulling" the tidal bulge ahead.

The relation between the tides and the moon was understood thousands of years ago by people living near sea shores. The reason wasn't understood until a few centuries ago, but the regular relation between high tide and the passage of the moon wasn't difficult for ancient people to observe.

It is somewhat interesting, in a "human psychology" sense, that people expect the tidal bulge to follow the moon. It says something about our propensity to reason without comparing our conclusions with reality. If the Earth weren't rotating, the tidal bulge would follow behind the moon. But the Earth is rotation about 27 times faster than the moon is moving in the sky, so the frictional forces pull the tidal bulge forward.

There's a good introductory description of this on <a href="http://en.wikipedia.org/wiki/Moon#Tidal_effects">wikipedia</a>, as is so often true for factual matters. The article has an "Early studies" section that goes into a few of the ancient calculations about how the tides and moon are related.

Actually, tidal patterns are a very complex subject, and it wouldn't be surprising if there were a few places in the world where the tidal peak is after the moon passes the local longitude. But I've never read about such a place. Does anyone know? There are a few documented places where there's only one high tide per day, because water sloshing around the local terrain cancels out the somewhat smaller tidal bulge on the other side of the Earth from the moon. There are also ocean shores that show little or no tides, such as the Mediterranean, Baltic, Japan and South China seas, mostly due to their small size and poor interaction with the larger oceans. And this is made up for with places like the Bay of Fundy, with its spectacular tidal bores.

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Re: 1119: "Undoing"

Postby phlip » Thu Oct 11, 2012 12:47 am UTC

jc wrote:
phlip wrote:Viscosity is just resistance to flowing - it slows down the flowing of the tide, so it's slightly behind where the moon is, which in turn is what causes the tidal locking effects. Anything that slows down the flowing of the tide will add to that effect.

Lots of explanations draw the picture this way, but the fact is that the tide's peak precedes the moon's passage "overhead" (i.e. past your line of longitude) about an hour later than the tide's peak. The actual time difference depends on the local underwater terrain, of course, so the time difference varies at different locations.

The reason the tidal bulge races ahead of the moon is that the Earth is rotating a lot faster than the moon, in terms of degrees per hour. The Earth's surface moves 360 degrees (actually about 361 degrees) in a day; the moon moves about 12 degrees in the sky in that time. So the land under the oceans is "pulling" the tidal bulge ahead.

Well, in an inertial frame, yes. The earth is spinning (relatively) quickly from west to east, while the moon is moving (relatively) slowly from west to east, and the high tide is somewhere to the east of the moon, due to all the various effects you mention, so in that sense it's "leading" the moon. But in a rotating frame where the Earth is stationary, the high tide is still somewhere to the east of the moon (obviously), but now we see the moon as rising in the east and setting in the west, so from this POV the tide is trailing the moon. That is, a particular point on the Earth's surface (as opposed to a particular point in an absolute frame) sees the moon as "overhead" before the high tide hits. It's the same thing, just from a different point of view - what you called the motion of the terrain dragging the bulge forward, and I called the stationary terrain holding the bulge back, are just the same things in different reference frames.

Regardless, adding more things that impede the flow of the oceans would, in general, tend to increase this effect.

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Re: 1119: "Undoing"

Postby StClair » Thu Oct 11, 2012 1:23 am UTC

So he's just pointlessly increasing entropy, with no useful work being done.

Call me (or better yet, the cops) when he works his way up to retroactive abortion.

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Re: 1119: "Undoing"

Postby Ranaakamarth » Thu Oct 11, 2012 2:12 am UTC

Ahh.... it's good to see the old "My Hobby" comics. Those are some of my favorite!

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Re: 1119: "Undoing"

Postby W3ird_N3rd » Thu Oct 11, 2012 3:50 am UTC

mcdigman wrote:
Vroomfundel wrote:1 million people die on the roads per year and I don't see anyone protesting for banning cars because they are dangerous.


Of course not. But you do see people advocating banning drivers. Seriously-the drunk driving problem disappears completely if the cars are driven by computers, because computers don't drink/text and drive (perhaps excepting Bender from Futurama) and don't get sleep deprived or road rage. Forget whether driverless cars should be legal: the question is whether cars with drivers should be legal.

Driving used to be much safer really.

My grandpa once told me, when he was a little kid, the speed limit was 2 (two) mph and you had to have a bloke with a red flag walk in front of you to warn everyone you were coming.

I'm actually not kidding.
tomintx wrote:Whose fault is it if your driverless car runs thru a group of children crossing the road?

I'd say the answer is the same as the answer to the question "Who is responsible if a car blows up for no reason next to a group of children?".

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Re: 1119: "Undoing"

Postby Jamaican Castle » Thu Oct 11, 2012 4:17 am UTC

W3ird_N3rd wrote:I'd say the answer is the same as the answer to the question "Who is responsible if a car blows up for no reason next to a group of children?".


If the car literally blows up for absolutely no reason, then by definition no one is at fault.
Fortunately, it is physically impossible for things to blow up for absolutely no reason.

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Re: 1119: "Undoing"

Postby ijuin » Thu Oct 11, 2012 4:27 am UTC

super dark33 wrote:Is it like the idea i had a long time ago?

An electric engine that powers a turbine with enough power to keep the engine going, thus creating an infinite energy cycle?
or is it better?

It would only keep going if the conversion from electrical current to motion and back again was 100% efficient (it's not unless all electrical conductors are superconducting while all OTHER materials have ZERO conductivity to prevent eddy currents), and also if there were zero friction in the entire mechanism (including zero friction with air/liquid surrounding the system, so it would have to operate in a vacuum).

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Re: 1119: "Undoing"

Postby Pfhorrest » Thu Oct 11, 2012 4:56 am UTC

StClair wrote:So he's just pointlessly increasing entropy, with no useful work being done.

No, he's restoring the energy to its rightful place doing the useful work of moving air around!

It's the damn thieves who decided to steal that energy and convert it into electricity who pointlessly increased entropy during the conversion. You can be that this guy is putting as much of that back into the atmosphere as efficiently as possible; he can't help the losses incurred by its initial theft and the cost of reconverting it back to its natural form.
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Re: 1119: "Undoing"

Postby VanI » Thu Oct 11, 2012 5:36 am UTC

tomintx wrote:Whose fault is it if your driverless car runs thru a group of children crossing the road?

The children's, of course.
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Re: 1119: "Undoing"

Postby Kraller75 » Thu Oct 11, 2012 5:38 am UTC

My understanding of wind turbines is that the generator inside is an induction generator. This means that it can generate real power, but can't generate reactive power. In fact, it is a reactive load. It needs to be hooked up to the grid in order to have the voltage to generate properly. This means that when the turbine is disconnected from the grid and hooked up to the fan motor, the voltage on the line will collapse, and the fan motor will not turn.

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Re: 1119: "Undoing"

Postby Max™ » Thu Oct 11, 2012 5:41 am UTC

Matter-Antimatter annihilation in the earliest moments after the big bang along with the various phase changes that took place are responsible for a huge amount of energy still floating around the universe.

A pair production supernova (or hypernova) generates a lot of energy through matter-antimatter annihilation, and the neutrino pulse carries a large amount of energy out of the star, while they are technically triggered by gravity, that is more of an iffy area.

Massive supernovae produce heavy elements which decay and release energy, at least some portion of the geothermal energy trapped within the Earth is due to radioactivity.


It's Murphy's fault when a driverless car runs over children.
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Re: 1119: "Undoing"

Postby Pfhorrest » Thu Oct 11, 2012 6:23 am UTC

Max™ wrote:Matter-Antimatter annihilation in the earliest moments after the big bang along with the various phase changes that took place are responsible for a huge amount of energy still floating around the universe.

Is it really fair to say that the energy came from matter-animatter annihilation, rather than just that there was a lot of energy (from wherever) in one place, and thus lots of particles and antiparticles were created, and annihilated, and so on, until they stopped being created as the energy density decreased sufficiently, leaving the sparse matter we're familiar with and a lot of kinetic/heat energy (and a metric fuckton of photons, if we don't want to count them as "matter")? Or do we have well-supported theories that say "in the beginning, there was a lot of matter and antimatter, and then it annihilated"?

A pair production supernova (or hypernova) generates a lot of energy through matter-antimatter annihilation

I'm not familiar with this phenomenon, can you elaborate? Is this different from just a really big supernova? Where does the antimatter in the reaction come from?

Massive supernovae produce heavy elements which decay and release energy, at least some portion of the geothermal energy trapped within the Earth is due to radioactivity.

I was counting this as "indirect fusion" because the heavy elements got their energy from high-energy fusion in supernovae, no? Not ordinary main sequence star type fusion, but the explosion still effectively fuses lighter elements into heavy ones, doesn't it?
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Re: 1119: "Undoing"

Postby Max™ » Thu Oct 11, 2012 6:30 am UTC

Pfhorrest wrote:
Max™ wrote:Matter-Antimatter annihilation in the earliest moments after the big bang along with the various phase changes that took place are responsible for a huge amount of energy still floating around the universe.

Is it really fair to say that the energy came from matter-animatter annihilation, rather than just that there was a lot of energy (from wherever) in one place, and thus lots of particles and antiparticles were created, and annihilated, and so on, until they stopped being created as the energy density decreased sufficiently, leaving the sparse matter we're familiar with and a lot of kinetic/heat energy (and a metric fuckton of photons, if we don't want to count them as "matter")? Or do we have well-supported theories that say "in the beginning, there was a lot of matter and antimatter, and then it annihilated"?
One would expect there to have been the same amount of matter and antimatter, there was a tiny asymmetry that left a tiny bit of matter which makes up everything we see, with the rest being a mush of high energy photons.

http://en.wikipedia.org/wiki/Baryogenesis
http://en.wikipedia.org/wiki/Baryon_asymmetry
The baryon asymmetry problem in physics refers to the fact that there is an imbalance in baryonic matter and antibaryonic matter in the universe. Neither the standard model of particle physics, nor the theory of general relativity provide an obvious explanation for why this should be so; and it is a natural assumption that the universe be neutral with all conserved charges.[1] The Big Bang should have produced equal amounts of matter and antimatter, as such, there should have been total cancellation of both. In other words, protons should have cancelled with antiprotons, electrons with antielectrons (positrons), neutrons with antineutrons, and so on for all elementary particles. This would have resulted in a sea of photons in the universe with no matter. Since this is evidently not the case, after the Big Bang, some physical laws must have acted differently for matter and antimatter.

There are competing hypotheses to explain the matter-antimatter imbalance that resulted in baryogenesis, but there is as yet no one consensus theory to explain the phenomenon.


A pair production supernova (or hypernova) generates a lot of energy through matter-antimatter annihilation

I'm not familiar with this phenomenon, can you elaborate? Is this different from just a really big supernova? Where does the antimatter in the reaction come from?

http://en.wikipedia.org/wiki/Pair-instability_supernova

A pair-instability supernova occurs when pair production, the production of free electrons and positrons in the collision between atomic nuclei and energetic gamma rays, reduces thermal pressure inside a supermassive star's core. This pressure drop leads to a partial collapse, then greatly accelerated burning in a runaway thermonuclear explosion which blows the star completely apart without leaving a black hole remnant behind.[1] Pair-instability supernovae can only happen in stars with a mass range from around 130 to 250 solar masses and low to moderate metallicity (low abundance of elements other than hydrogen and helium, a situation common in Population III stars). The recently observed objects SN 2006gy and SN 2007bi[2] are hypothesized to have been pair-instability supernovae.


Photon pressure

In very large hot stars, pressure from fusion reaction gamma rays in the stellar core keeps the upper layers of the star supported against gravitational pull from the core. If the stream of gamma rays is reduced, then the outer layers of the star will start to be pulled inwards in a gravitational collapse.
Pair creation

Pair creation results from gamma-atomic nucleus reactions interacting via the coulomb force (see Pair production by gamma rays). The pair creation cross section for a given material is strongly dependent on the energy of the gamma ray photon – as the gamma rays get more energetic, they are more likely to interact with the atoms they pass through. From Einstein's equation E = mc^2, gamma rays must have more energy than the mass of the electron–positron pairs to produce these pairs.

As described in the introduction, the results of pair creation interactions are pairs of electrons and positrons. These particles are released into the star's core and usually recombine (releasing another gamma ray) in very short time periods.

Even though the energy is typically re-released rapidly by the recombination of the electron and positron, the speed at which energy (radiation) transfers through a gas is highly dependent on the average distance between interactions. A photon that is absorbed in pair creation interactions effectively is stopped, and then re-radiated in a random direction.


Massive supernovae produce heavy elements which decay and release energy, at least some portion of the geothermal energy trapped within the Earth is due to radioactivity.

I was counting this as "indirect fusion" because the heavy elements got their energy from high-energy fusion in supernovae, no? Not ordinary main sequence star type fusion, but the explosion still effectively fuses lighter elements into heavy ones, doesn't it?

http://en.wikipedia.org/wiki/Supernova_nucleosynthesis


Supernova nucleosynthesis is the production of new chemical elements inside supernovae. It occurs primarily due to explosive nucleosynthesis during explosive oxygen burning and silicon burning.[1] Those fusion reactions create the elements silicon, sulfur, chlorine, argon, sodium, potassium, calcium, scandium, titanium and iron peak elements: vanadium, chromium, manganese, iron, cobalt, and nickel. As a result of their ejection from individual supernovae, their abundances grow increasingly larger within the interstellar medium. Heavy elements (heavier than nickel) are created primarily by a neutron capture process known as the r process. However, there are other processes thought to be responsible for some of the element nucleosynthesis, notably a proton capture process known as the rp process and a photodisintegration process known as the gamma (or p) process. The latter synthesizes the lightest, most neutron-poor, isotopes of the heavy elements.
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Re: 1119: "Undoing"

Postby Hubert » Thu Oct 11, 2012 7:52 am UTC

kfitch42 wrote:This reminds me of a story I read a while ago about a company in Europe (I think it was France) that was shining lamps (fossil fuel powered) on photovoltaic cells in order to get subsidies or tax credits. Supposedly they were able to make money this way.

Can't find a link, my google-foo is failing me right now, sorry :(.


It is also similar to dams (e.g. the Grand'Maison dam in France) that are used both to generate power by letting the water flow down from the reservoir, and to store energy by pumping water up to the reservoir.

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Re: 1119: "Undoing"

Postby Willl » Thu Oct 11, 2012 9:59 am UTC

tomintx wrote:
mcdigman wrote: Seriously-the drunk driving problem disappears completely if the cars are driven by computers, because computers don't drink/text and drive

Of course we would see a new definition of "Computer Crash"

Whose fault is it if your driverless car runs thru a group of children crossing the road?

This, realistically, is going to be the reason for the biggest avoidable cause of death in humankind's history, at least until climate change gets a chance to overtake it. Driverless car technology will before long be mature enough to have a lower fatal failure rate than human drivers, and even be affordable to run, but we'll carry on mowing each other down behind steering wheels and pedals because we can't find someone to blame for the deaths that are left over by the safer technology.

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Re: 1119: "Undoing"

Postby Rotherian » Thu Oct 11, 2012 12:39 pm UTC

Willl wrote:
tomintx wrote:
mcdigman wrote: Seriously-the drunk driving problem disappears completely if the cars are driven by computers, because computers don't drink/text and drive

Of course we would see a new definition of "Computer Crash"

Whose fault is it if your driverless car runs thru a group of children crossing the road?

This, realistically, is going to be the reason for the biggest avoidable cause of death in humankind's history, at least until climate change gets a chance to overtake it. Driverless car technology will before long be mature enough to have a lower fatal failure rate than human drivers, and even be affordable to run, but we'll carry on mowing each other down behind steering wheels and pedals because we can't find someone to blame for the deaths that are left over by the safer technology.


Of course, although it would take a fair bit of monetary investment, cities could make foot bridges that go over the streets. If anyone gets hit after those are constructed, it is their own fault.
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Re: 1119: "Undoing"

Postby Whizbang » Thu Oct 11, 2012 12:54 pm UTC

Re: Driverless cars

All speed limits will be either 35mph or 100mph. 35mph on roads where people may cross. The driverless car would have, assumably, faster reaction time than a human. So, people can cross on these roads (though obiouvsly it is strongly suggested to do so at the intersection or designated cross-walk). Driverless cars would be able to sense most objects on or near the road in enough time to be able to slow, stop, or change lanes to avoid. The exception would be someone who leaps out in front of the car just as it passes. Maybe to avoid this issue, roads will have rails/guards on them to more strongly suggest crossing at cross-walks. 100mph will be used in all highways/freeways. These roads will be for cars only and be fenced/walled off from pedestrian access.

Maybe in more congested areas (eg downtown NY City) there will have to be some other special rules or something (maybe 5-10mph). I dunno.

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Re: 1119: "Undoing"

Postby J Thomas » Thu Oct 11, 2012 1:01 pm UTC

Rotherian wrote:
Willl wrote:
tomintx wrote:
mcdigman wrote: Seriously-the drunk driving problem disappears completely if the cars are driven by computers, because computers don't drink/text and drive

Of course we would see a new definition of "Computer Crash"

Whose fault is it if your driverless car runs thru a group of children crossing the road?

This, realistically, is going to be the reason for the biggest avoidable cause of death in humankind's history, at least until climate change gets a chance to overtake it. Driverless car technology will before long be mature enough to have a lower fatal failure rate than human drivers, and even be affordable to run, but we'll carry on mowing each other down behind steering wheels and pedals because we can't find someone to blame for the deaths that are left over by the safer technology.


Of course, although it would take a fair bit of monetary investment, cities could make foot bridges that go over the streets. If anyone gets hit after those are constructed, it is their own fault.


For perhaps less investment, cities could station segways at each intersection, and if you get on one it won't cross the street until it's safe.
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Re: 1119: "Undoing"

Postby mathmannix » Thu Oct 11, 2012 1:10 pm UTC

Jamaican Castle wrote:
W3ird_N3rd wrote:I'd say the answer is the same as the answer to the question "Who is responsible if a car blows up for no reason next to a group of children?".


If the car literally blows up for absolutely no reason, then by definition no one is at fault.
Fortunately, it is physically impossible for things to blow up for absolutely no reason.


Ah yes, the good old sponaneous internal combustion engine...

edit: Actually, we know spontaneous human combustion exists [1], causing humans to burst into flames for no reason. (Of course, everything happens for a reason, just not one we know about. I always liked to imagine my simcity residents wondering how they randomly get new streets and buildings, and sometimes mountains and rivers.)

* 1 - citation: Weekly World News
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Re: 1119: "Undoing"

Postby rmsgrey » Thu Oct 11, 2012 2:28 pm UTC

mathmannix wrote:* 1 - citation: Weekly World News

Fails WP:RELIABLE?

:P

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Re: 1119: "Undoing"

Postby WanderingLinguist » Thu Oct 11, 2012 3:53 pm UTC

mathmannix wrote:
Jamaican Castle wrote:
W3ird_N3rd wrote:I'd say the answer is the same as the answer to the question "Who is responsible if a car blows up for no reason next to a group of children?".


If the car literally blows up for absolutely no reason, then by definition no one is at fault.
Fortunately, it is physically impossible for things to blow up for absolutely no reason.


Ah yes, the good old sponaneous internal combustion engine...


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Re: 1119: "Undoing"

Postby Sandor » Thu Oct 11, 2012 4:37 pm UTC

Jamaican Castle wrote:Fortunately, it is physically impossible for things to blow up for absolutely no reason.

Except for maybe the universe. As Terry Pratchett put it: "In the beginning there was nothing, which exploded." Although here, "nothing" means absolutely nothing, no space, no time, no anything. So that might not fall under the definition of "things".

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Re: 1119: "Undoing"

Postby bmonk » Thu Oct 11, 2012 5:14 pm UTC

jc wrote:Actually, tidal patterns are a very complex subject, and it wouldn't be surprising if there were a few places in the world where the tidal peak is after the moon passes the local longitude. But I've never read about such a place. Does anyone know? There are a few documented places where there's only one high tide per day, because water sloshing around the local terrain cancels out the somewhat smaller tidal bulge on the other side of the Earth from the moon. There are also ocean shores that show little or no tides, such as the Mediterranean, Baltic, Japan and South China seas, mostly due to their small size and poor interaction with the larger oceans. And this is made up for with places like the Bay of Fundy, with its spectacular tidal bores.


I remember seeing a map of the tide peak as it swirls around the British Isles--there should be places there where the tides are synchronized with the moon, or after, or even in opposition.
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Re: 1119: "Undoing"

Postby Willl » Thu Oct 11, 2012 5:15 pm UTC

Whizbang wrote:Re: Driverless cars
Driverless cars would be able to sense most objects on or near the road in enough time to be able to slow, stop, or change lanes to avoid.

Never mind "would", Google's cars already do this. They just haven't been tested on millions of miles of data yet, and there's still plenty of refinement to build into their algorithms before you'd want to start comparing their pedestrian-spotting skills to those of humans.
Whizbang wrote:The exception would be someone who leaps out in front of the car just as it passes. Maybe to avoid this issue, roads will have rails/guards on them to more strongly suggest crossing at cross-walks. 100mph will be used in all highways/freeways. These roads will be for cars only and be fenced/walled off from pedestrian access.

J Thomas wrote:
Rotherian wrote:Of course, although it would take a fair bit of monetary investment, cities could make foot bridges that go over the streets. If anyone gets hit after those are constructed, it is their own fault.


For perhaps less investment, cities could station segways at each intersection, and if you get on one it won't cross the street until it's safe.

All these pedestrian protection measures would of course apply equally to drivered cars, and they mostly don't exist because of how super expensive they would be for protection against something that in principle pedestrians are entirely within their abilities to avoid. Perhaps a less out-of-this world derivative of the segway idea in a driverless world would be some RF communication protocol that would let pedestrians request crossing the road, and the driverless cars around to coordinate a stop in the flow of traffic to allow that to happen. Anyone with a compatible smartphone or similar would then be able safely to cross anywhere, and the need for fixed point pedestrian crossings greatly reduced. I'd also like to think that speeds well in excess of 100mph would be permissible on freeways, although average speeds might be more dictated by target fuel consumptions specified at start of journey rather than vehicle capability....

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Re: 1119: "Undoing"

Postby Fieari » Thu Oct 11, 2012 5:15 pm UTC

Sandor wrote:
Jamaican Castle wrote:Fortunately, it is physically impossible for things to blow up for absolutely no reason.

Except for maybe the universe. As Terry Pratchett put it: "In the beginning there was nothing, which exploded." Although here, "nothing" means absolutely nothing, no space, no time, no anything. So that might not fall under the definition of "things".


I love it when goy scientists discuss kabbalah. 8-)
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Re: 1119: "Undoing"

Postby bmonk » Thu Oct 11, 2012 5:18 pm UTC

mathmannix wrote:
Jamaican Castle wrote:
W3ird_N3rd wrote:I'd say the answer is the same as the answer to the question "Who is responsible if a car blows up for no reason next to a group of children?".


If the car literally blows up for absolutely no reason, then by definition no one is at fault.
Fortunately, it is physically impossible for things to blow up for absolutely no reason.


Ah yes, the good old sponaneous internal combustion engine...

Hollywood has a corner on that market. Some of their cars spontaneously explode shortly after driving off a cliff, even before they hit anything! And very few manage to land without spectacular explosions. Others take just a bullet or two, or a minor accident, to explode.
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Re: 1119: "Undoing"

Postby Jamaican Castle » Thu Oct 11, 2012 6:10 pm UTC

Willl wrote:Perhaps a less out-of-this world derivative of the segway idea in a driverless world would be some RF communication protocol that would let pedestrians request crossing the road, and the driverless cars around to coordinate a stop in the flow of traffic to allow that to happen.


For my part, I'd rather not give every teenager with a smartphone the ability to hold up traffic indefinitely.

Also, driverless cars need to be able to function in a hybrid situation - lots of both driverless and traditional cars, because that's what the situation will be like for a long time after their adoption. If only because there are a lot of cars in existence, and many people won't want to or be able to afford to turn them in.

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Re: 1119: "Undoing"

Postby dp2 » Thu Oct 11, 2012 6:44 pm UTC

There used to be a dam in Michigan where the owner would pump water above the dam at night, when power rates are lower, then would sell the energy generated by letting it flow through the dam during the day, when rates are higher. A net loss of energy for the universe, of course, but for the dam owner, a net monetary gain.

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Re: 1119: "Undoing"

Postby ctsketch » Thu Oct 11, 2012 6:52 pm UTC

dp2 wrote:There used to be a dam in Michigan where the owner would pump water above the dam at night, when power rates are lower, then would sell the energy generated by letting it flow through the dam during the day, when rates are higher. A net loss of energy for the universe, of course, but for the dam owner, a net monetary gain.


Not lost...just transformed

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Re: 1119: "Undoing"

Postby Pfhorrest » Thu Oct 11, 2012 7:57 pm UTC

ctsketch wrote:
dp2 wrote:There used to be a dam in Michigan where the owner would pump water above the dam at night, when power rates are lower, then would sell the energy generated by letting it flow through the dam during the day, when rates are higher. A net loss of energy for the universe, of course, but for the dam owner, a net monetary gain.


Not lost...just transformed

Free (i.e. usable) energy lost. Entropy increased.
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Re: 1119: "Undoing"

Postby Coderjoe » Thu Oct 11, 2012 7:58 pm UTC

Eutychus wrote:I've always wondered about the effect of wind turbines on the wind.

Check out this news item that showed up on various NOAA sites last year. It includes at least one interesting image showing what happens around a wind turbine.

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Re: 1119: "Undoing"

Postby exoren22 » Thu Oct 11, 2012 8:29 pm UTC

rmsgrey wrote:
da Doctah wrote:Or Steven Wright's idea for a battery-powered battery charger.


Ultimately, all our forms of "energy generation" are are ways of converting one form of stored energy into another - sometimes very volatile storage, but still ways of keeping the energy until it's used or dissipated.

In that light, the only thing that's silly about a battery-powered battery charger is that it would be "converting" energy from one form to a very similar one - with more general "batteries", that may be sensible - for example, using the flow of water from a water-tower (gravitational potential battery) to drive a turbine to power something, and tapping that power to charge your iPod at the same time...


Um, we have these. http://www.amazon.com/Duracell-Instant-Charger-Includes-Universal/sim/B002FU6KF2/2

It's pretty much the polar opposite of "silly".

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Re: 1119: "Undoing"

Postby philipquarles » Thu Oct 11, 2012 8:50 pm UTC

I accidentally poured more cream than I wanted into my coffee. Can someone show me how to stir it out?

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Re: 1119: "Undoing"

Postby Thrasymachus » Thu Oct 11, 2012 9:04 pm UTC

As soon as driverless cars become legal where I live, I'm buying a driverless taxicab or three and undercut everybody else's per-mile rates.

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Re: 1119: "Undoing"

Postby J Thomas » Thu Oct 11, 2012 9:19 pm UTC

philipquarles wrote:I accidentally poured more cream than I wanted into my coffee. Can someone show me how to stir it out?


Add enough extra coffee until you have the right amount of cream. Then stir.

Then drink the whole thing. You know you want to.
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Re: 1119: "Undoing"

Postby JJH » Fri Oct 12, 2012 12:11 am UTC

Hubert wrote:
kfitch42 wrote:This reminds me of a story I read a while ago about a company in Europe (I think it was France) that was shining lamps (fossil fuel powered) on photovoltaic cells in order to get subsidies or tax credits. Supposedly they were able to make money this way.

Can't find a link, my google-foo is failing me right now, sorry :(.


It is also similar to dams (e.g. the Grand'Maison dam in France) that are used both to generate power by letting the water flow down from the reservoir, and to store energy by pumping water up to the reservoir.

Except, of course, that it's actually legit way of storing power. Unlike the obvious photovoltaic scam above (or the wind powered atmosphere heating device somebody built as a hobby).

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Re: 1119: "Undoing"

Postby stephen431 » Fri Oct 12, 2012 12:37 am UTC

Jamaican Castle wrote:
W3ird_N3rd wrote:Fortunately, it is physically impossible for things to blow up for absolutely no reason.


You must not be married.

..or have young children.

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Re: 1119: "Undoing"

Postby Eutychus » Fri Oct 12, 2012 5:11 am UTC

Coderjoe wrote:
Eutychus wrote:I've always wondered about the effect of wind turbines on the wind.

Check out this news item that showed up on various NOAA sites last year. It includes at least one interesting image showing what happens around a wind turbine.


From the caption:
Normally invisible, wind wind wakes take shape in the clouds


Wind wind wakes?
Be very careful about rectilinear assumptions. Raptors could be hiding there - ucim


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