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Stupid science questions

 
  

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lukabeast
14:46 / 13.02.04
Hi Tom, thanks for the info and the link. Just what I was looking for.
 
 
Cheap. Easy. Cruel.
17:20 / 13.02.04
The chances of you getting electrocuted are nil, Deva. You could recieve a mild shock perhaps, but even that is pretty unlikely. While working on electrical circuits in my home, I have plugged myself in to both 110v and 220v. It did nothing more than startle me and leave my arm numb for a minute or two. Your hands would have to be dripping water and the water would have to form a path from the internal contacts of the switch to your hand to give you a jolt.
 
 
tom-karika nukes it from orbit
20:46 / 13.02.04
How exactly did you plug yourself into 220V, histrionic whack job?

A 220 V shock can knock people to the floor, or give a mild jolt, depending on the quality of the contact.

(By electrocuted, do you mean killed or shocked? I've always thought of it as beng shocked rather than killed, but looking it up, it seems to be defined as 'killed'. I suppose the chances of that are rather slim.)

Proper, death-inducing electrocution happens when the shock travels across the heart and stops it, or when the pain and shock causes death later. The stoppage of the heart is pretty unlikely. I imagine the path of least resistance from the finger to earth, when standing up, is some way away from the heart.

The very bottom of this page gives a nice (nice?) table of electrical contact and how it affects the body at different wattages. The rest of the page is just blindingly obvious advice to construction workers (Don't poke power lines with ladders, etc.)
 
 
grant
18:47 / 16.02.04
There's a difference between British and US wiring on this thing, too. I know the 220 you find in US homes (generally only around the hot water heater, the dryer and the stove, as well as the fat cable bringing power into your house) is enough to kill an average person dead if they're not particularly lucky. (I was told this by a few professionals after unknowingly meddling with a 220v box in my kitchen.)

The 110 our lights and sockets run off will leave you a bit tingly (or worse, if you've got a weak heart or if you clamp your hands down on the wire and get stuck there). There may be an amperage difference between the UK and US, I don't know. Is there?

But yeah, the problem is if a water droplet runs into the switch and forms a temporary wire plugging your wet hand into the circuit, basically.

I like that table though, with the lightbulb. That deadly lightbulb....
 
 
Cheap. Easy. Cruel.
12:10 / 23.02.04
Tom-Karikar
How exactly did you plug yourself into 220V, histrionic whack job?

A 220 V shock can knock people to the floor, or give a mild jolt, depending on the quality of the contact.


That one did not take place in my home. I was working as a quality control manager in an appliance manufacturing plant, and a technician had asked me a question about a range he had been working on. Somehow, he had managed to put a short in the power cord and powered it up while I had my hands on the range. Fortunately, it knocked me back against a railing at which time I was no longer in contact with the range. My hands and arms were numb and tingling for about 10 minutes after.

In my earlier post, I was interpreting electrocuted to mean death by electric shock. I have never heard of anyone being killed by 110v, which should be what the lights in your bathroom should be run on. You might give yourself a nasty little jolt, but even that is unlikely.
 
 
Phex: Dorset Doom
12:52 / 23.02.04
Has anyone actually BUILT a Nuetron Bomb?
Supposedly a Nuetron bomb explodes in a similar radius to a conventional nuclear weapon, the key difference being that instead of leaving a big gaping hole, it just gets rid of organic matter. Buildings and machines are left standing. How does this work, if at all?
 
 
Cheap. Easy. Cruel.
14:20 / 23.02.04
From this article:

Between 1958 and 1961 the neutron bomb idea was tested successfully, but the politicians in Washington nixed development and deployment of the weapon. Cohen persisted. As the Vietnam War began and festered in the 1960s, Cohen became an advocate of using neutron bombs there. To Cohen, his weapon was "a perfect fit" for dealing with the Viet Cong hidden in the jungles and rice paddies.


In 1979, he was in Paris helping the French build their own arsenal of neutron bombs when presidential candidate Ronald Reagan came through on a European tour. Cohen met with Reagan to brief him on the neutron bomb. Reagan grasped the idea of neutron weaponry immediately, and made a pledge to Cohen, and later a public pledge, that he would reverse Carter administration policy by building and deploying a large number of neutron bombs.

As president, Reagan fulfilled that pledge and approximately a thousand weapons were constructed. But criticism from European allies kept the weapons from being deployed across Europe.

With the fall of the Berlin Wall and the end of communism as we knew it, the Bush administration moved to dismantle all of our tactical nuclear weapons, including the Reagan stockpile of neutron bombs. In Cohen's mind, America was brought back to Square One. Without tactical weapons like the neutron bomb, America would be left with two choices if an enemy was winning a conventional war: surrender, or unleash the holocaust of strategic nuclear weapons.

Other nation's haven't been afflicted by the U.S. blindness regarding neutron bombs. According to Cohen:

Evidence exists that China has neutron bombs stockpiled, and that the United States gave the Chinese the technology to build them.

Russia has a large quantity of such weapons, as well as the world's largest arsenal of nuclear weapons.

Israel has hundreds of neutron weapons. The neutron bombs would allow Israel to stop advancing Arab armies and tank columns - even one on Israeli soil - without permanently contaminating the land.

South Africa, which constructed a cache of neutron weapons before the end of white rule, claimed it dismantled those weapons before handing over power to the Nelson Mandela government. Cohen, however, claims to have it on good authority that white military leaders still control the secret stockpile as "an insurance policy."
 
 
Phex: Dorset Doom
21:29 / 23.02.04
Dang...
 
 
C.Elseware
00:17 / 25.02.04
I've never got my head around part of relativity...

If there are 3 objects A, B & C.

B and C are both moving away from A at 75% of lightspeed in opposite directions.

How come the relative speed between B & C is not 150% lightspeed?
 
 
Lurid Archive
12:42 / 25.02.04
Always tricky, this one, but the thing to remember is that, in relativity (special or general) there is no absolute frame of reference.

Calculating speeds relative to A is not quite the same as calculating the speeds of B relative to C with a quick addition. Essentially, time and space are different for B than they are for A. Time dilation kicks in such a way that ensures the light speed restriction.

I think part of the confusion is in asking what we mean by the speed (or velocity) of C relative to B. Now, in any common sense universe, this is just the same as working out the differences in speed with respect to A. And this turns out to be the same as the speed that B would measure when looking at C.

However, we are not in a common sense universe, and the second definition takes precedence over the first.
 
 
Jackie Susann
23:54 / 27.02.04
How come people (and animals) need to sleep? Isn't it the kind of thing evolution should have gotten rid of?
 
 
grant
02:16 / 28.02.04
I don't think science has an answer for that one yet, only guesses. I know sleep (or sleep-like states) go pretty far down the evolutionary ladder; even plants undergo metabolic changes at night.
 
 
Mister Man
19:09 / 01.03.04
On a similar evolutionary theme... short sightedness, how is it this trait hasn't been weeded out of our genes? Is being able to see well, not that much of an advantage? Let's go way back.. "cavepeople" if you like. Finding food, spotting shelter, avoiding enemies, all difficult to do if you can't see well. 25% - 33% of the UK population are shorted sighted (http://www.nhsdirect.nhs.uk/en.asp?TopicID=702). A third of our cave dweller ancesters bumping into things and falling over rocks? How did they survive? Now come forwards in time, you're a short sighted soldier at Hastings or Agincourt or any other battle pre-glasses. Waggling your sword in front of your nose at those looming shadows. Hmmm, well you get the idea.

Anyway. How have the shortsighted genes lasted so long?
 
 
Phex: Dorset Doom
11:00 / 03.03.04
"I've heard Alan Moore say that modern physics presently suggests we exist in a 4th-dimensional crystal"
from: http://www.disinfo.com/site/displayarticle2340.html

What does this mean exactly? Who are the theorists expounding this view?
 
 
Saveloy
14:23 / 03.03.04
Re: Shortsightedness>

My guess is that as long as you survive for long enough to breed (and for cavepeople that'd be pretty young) and you are physically capable of breeding, then you stand as good a chance as anyone of passing on your genes (what happens to you after that doesn't really matter, as far as your genes are concerned). It seems reasonable to me to assume that short-sightedness would not have been a big killer or disabler of pre-pubescent types, and therefore there would be plenty of surviving breeders. As long as they weren't so myopic that they couldn't tell a mate from a mammoth, that is.

Btw, I know it affects people of all ages, but am I right in thinking that it doesn't usually start to affect people until their mid-teens?
 
 
grant
14:39 / 03.03.04
1. More on sleep: the prevailing *theory* is that it's a kind of downtime our brains need to reorder all the sense data it gets during the day. Therefore, the *more* developed our brains, the greater the need for sleep.

2. On 4th dimensional crystal: I think this gets into Kaku's hyperspace, and the fact that our universe might be a phenomenon "floating" or "growing" within the interface of other multi-dimensional universes. I'm not sure. The links up-thread about string theory might help explain this worldview.

3. On shortsightedness: My friend Jim is shortsighted, needs glasses to read, but is perfectly capable of surfing without 'em. Shortsightedness is really only a big deal if you need to pick out fine details, like written words at a distance. I don't think it matters for a hunter-gatherer nearly as much. I think a lot of shortsightedness cases aren't severe enough that you'd really be bumping into things and falling over rocks. Probably a small percentage are.
Also, there's that old saw about reading in the dark causing myopia... so maybe there are more environmental factors nowadays contributing to short-sightedness than in the past. Maybe there were fewer and less severe cases back in the days of Agincourt....
 
 
Lurid Archive
07:46 / 04.03.04
re 4 dimensions. I think its worth bearing in mind that when someone says the universe is a 4 dimensional crystal, like in the disinfo article, they often mean it metaphorically. That is, a physicist saying the same thing would mean something much more precise than a person with some vague intuition.

Now, the 4 dimensions of space-time are well established, relativity being almost classical now. But, as grant says, there are lots of theories about trying to unify physics by posting extra spatial dimensions. It makes the math work, but there is no evidence yet that I know of.
 
 
tom-karika nukes it from orbit
08:53 / 04.03.04
Shortsightedness:

I saw a study on Horizon a while back, concerning that very question. Shortsightedness is becoming more prevalent. And it is more prevalent in countries which have been developed the longest.

For instance, in Japan and China shortsightedness is much more prevalent than in Europe. However, arguably, China and Japan have been developed much longer than Europe (They had far higher literacy rates, more sophisticated technology etc. right up until a couple of centuries ago).

The theory being tested was that in a population which no longer needs to hunt, spot animals etc, and one which needs people doing fine detail work such as craftsmen, myopia is no longer a disadvantage. The trend in modern european societies was seen as evidence of short term (2-3 century time period) evolution/natural selection.

Another study in the programme showed that in populations which had been hunting until relatively recently (Native Americans, Australian Aborigines) had nearly no myopia.
 
 
Mirror
14:06 / 05.03.04
Stupid lightspeed and interstellar travel question:

It seems like the main limitation on interstellar travel is not necessarily the distance involved if one were able to travel at close to the speed of light, because relativistic effects would cause the traveler to experience only a minimal amount of time passing except for during acceleration and deceleration. So, my question is, how long would it take to accelerate to close to the speed of light if you limit the acceleration to something a human being could tolerate, like a few gravities?

Of course, relativity also states that the mass of a body increases as it accelerates, which means that more force is required to continue to accelerate it. In a spacecraft, acceleration is achieved by expelling reaction mass. Presumably the reaction mass is becoming more massive at the same rate as the rest of the craft, so does that mean that it takes more energy to push the reaction mass out the back end of the spaceship? Also, if one stops accelerating and just coasts, however briefly, what happens to the mass of the spacecraft? Do you still have problems with acceleration if it is pulsed?
 
 
Wombat
20:39 / 05.03.04
From the frame of reference of the space ship newtonian physics still hold. The rest of the universe slows down. The distance between the stars looks shorter as it gets near the speed of light. The force required to accelarate stays the same. When the ship hits light speed the universe shrinks to a point. In effect it is allready there. From the space ships point of view the reaction mass has the same mass as normal. Energy is conserved.

Watching the space ship from the stars it gains mass and shrinks lengthwise. Although the mass of the ship increases the mass of it`s ejected particles/reaction mass (thrust) also increases. So from the stars view it is business as usual and energy is conserved.

The mass of the space crafty depends on it`s speed realative to your viewpoint. If it coasts for a while then it`s mass is the same instead of steadilly increasing.

How long would also depend on your frame of reference. Sorry I can`t be arsed calculating it.
 
 
grant
23:44 / 05.03.04
that relative mass business is freakin' WEIRD.

According to this acceleration calculator, 1.5 gravities* is equal to 32.9 miles per hour/sec, or 14.7 meters/sec squared.

According to this site, the speed of light in a vacuum is 300,000,000 meters/sec (it also says that light slows down in water to around 225,000,000 meters per second).

So 300,000,000 divided by 14.7 is 20,408,163,265.306, which is 340,136,054.422 minutes or 5,668,934.240 hours or 236,205.593 days or 647.139 years.

A ship that took off when some of the first bubonic plague-bearing rats hit Italy would only now be reaching light speed. Columbus would not yet have taken off, and the English language still sounded more like German, with the word "knife" pronounced "ku-neef-ay".

That is, if I did the calculations right. Math, especially simple math, is not my strong suit.


* according to this page, a fighter pilot can only take 4Gs for a couple seconds before blacking out. I kinda figure anything too far over normal gravity is going to be too much of a strain for a crew over the time frame we're probably talking. It'd be like having a crew of morbidly obese osteoporosis sufferers.
 
 
Lurid Archive
14:04 / 06.03.04
Grant, its worse than that, of course. Because the amount of force required to maintain that acceleration increases as one approaches light speed and tends to the infinite. So you can never reach light speed.
 
 
Wombat
14:41 / 06.03.04
This site has some very pretty relativity movies.
A picture can explain these effects much better.
http://www.anu.edu.au/Physics/Searle/
 
 
gridley
16:20 / 12.03.04
Ok, this has been puzzling me lately. When you lose weight (fat loss), how does the fat leave your body? Is it just converted to energy with no physical by-product? Wouldn't there need to be some physical evacuation of the substance?
 
 
■
17:30 / 12.03.04
Ok, long thread just bumped back up, so I'm working through the answers that I understand. Why doesn't the earth fall into the sun? Well, in a way, it is. Constantly. However, it also has enough momentum in a direction which is perpendicular to the straight "suck" direction that by the time it has fallen, the sun is no longer there anymore. Think of standing on a cliff and firing a tennis ball in a straight line. Pretend it's a cliff in space to negate air resistance/friction, so that we're closer to how planets and satellites work. If you fire the tennis ball gently, it will fall in an arc down to the ground due to gravity.
If you imagine firing it with more energy each time, you can imagine that it will fall with a wider and wider arc. With enough energy, the arc will be so wide that it matches or exceeds the curvature of the planet you are on. It will still be falling toward the planet due to gravity, but it will never actually hit. That's an orbit. This is the principle of geostationary satellites. Send them up, getthem in place and then push them in the same direction as the earth so that they are falling all the time over the same spinning bit of earth.
Sorry if this has been said before, but I had to get it out before I get too drunk.
 
 
grant
18:11 / 12.03.04
When you lose weight (fat loss), how does the fat leave your body? Is it just converted to energy with no physical by-product? Wouldn't there need to be some physical evacuation of the substance?

The short answer to that is that it's converted to energy and that's why the process is so slow. I *think* the production of some free radicals (oxidizing compounds) would be a byproduct of that, but I get a little hazy about metabolism at the cellular level. I know that the process is an oxidation process to begin with, so the free radical thing might not make sense.

The long answer involves sentences like:
The acetyl CoA molecules formed in each cycle are oxidised to CO2 in the citric acid cycle, with the oxidation/reduction reactions coupled to the electron transport chain and further ATP synthesis.
 
 
■
18:41 / 12.03.04
Right, I have two questions.
One: How exactly do neutron bombs destroy organic matter and leave everything intact? I'm guessing they don't so much destroy (in the instant obliterate sense) as hugely reduce viability due to large doses of energy causing rupturing of cells. Is that right? If so, anyone useing a neurton bomb is going to have a city full of shit, piss and dissolving bodies to get rid of.
Two: Those hand washes which claim not to need water to cleanse your hands no matter how dirty they are. OK, they kill germs and evaporate off, but WHERE DOES THE DIRT GO?
 
 
Cheap. Easy. Cruel.
19:23 / 12.03.04
As far as the hand washes go, all of the ones I have seen only claim to be hand sanitizers. So, the dirt is still in the same place it was when you started, although a bit smeared about.

On the matter of the neutron bombs, I will have to get back to you.
 
 
Cheap. Easy. Cruel.
19:37 / 12.03.04
Neutron bombs, also called enhanced radiation weapons (ER), are small nuclear weapons in which the burst of neutrons generated by the fusion reaction is intentionally not absorbed inside the weapon, but allowed to escape. The X-ray mirrors and shell of the weapon are made of chromium or nickel so that the neutrons are permitted to escape. This intense burst of high-energy neutrons is the principle destructive mechanism. Neutrons are more penetrating than other types of radiation so many shielding materials that work well against gamma rays do not work nearly as well. The term "enhanced radiation" refers only to the burst of ionizing radiation released at the moment of detonation, not to any enhancement of residual radiation in fallout.

That is from here. Aparently, the intense blast of ionizing radiation gives a large enough dose (upwards of 8000 rads) to immediately incapacitate any living target. It just floods the entire area with enough radiation to cause cellular collapse within a matter of minutes. From the same article:

These same authorities say that the common perception of the neutron bomb as a "landlord bomb" that would kill people but leave buildings undamaged is greatly overstated. At the conventional effective combat range (690 m) the blast from a 1 kt neutron bomb will destroy or damage to the point of unusability almost any civilian building. Thus the use of neutron bombs to stop an enemy attack, which requires exploding large numbers of them to blanket the enemy forces, would also destroy all buildings in the area.

Another view of the neutron bomb and its tactics exists. The inventor of the neutron bomb, Samuel Cohen, wrote a book in which he stated that the effective range of a pure neutron bomb exceeded 10 Km of altitude. Samuel Cohen stated explicitly that "enhanced radiation" weapons deployed in Germany during the cold war were political compromises designed to have substantial blast, with radiation effects deliberately reduced to eliminate any possibility of surviving structures. He also quoted radiation releases of 100KRads at the ground from pure neutron weapons exploded at 10Km.
 
 
Phex: Dorset Doom
14:47 / 13.03.04
When I was about four years old I was taken to a bird sanctuary with an insect room where I saw a fly about the size of my head pinned inside one of the glass viewing cases.
Please somebody tell me that flies as big as my head don't really exist.
 
 
■
18:11 / 13.03.04
No, they don't. Unless you have avery small head.
I can't remember the exact details, but the the size of insects is limited by their breathing mechanism which relies on holes/tubes called spiracles. If these get too big (at they would have to be in this case) the spiracles wouldn't work. There's also something to do with the fact that insect skeletons wouldn't work if they became too big as gravity would make them useless.
Apparently some huge insects do exist, but they tend to be water based. Apparently some locusts have a wingspn of 7 inches. Still not quite head-sixed.
 
 
The resistable rise of Reidcourchie
11:32 / 15.03.04
What a wonderful thread.

As a result of this question I posted in the conversation's Q&A I have a probably quite elementary question (arts/humanities background you see, no use to anyone really) which I would appreciate if someone would

What is a singularity (see I told you they where elementary)?

Is it me or is the language of Physics actually quite beautiful?
 
 
Lurid Archive
12:13 / 15.03.04
(I should emphasise that I'm not a physicist here but...) A singularity is a point where a function or, more generally, a geometric object goes squiffy. Usually (always?) this means that some form of infinity rears its head - maybe your equations tell you to divide by zero at a certain point.

The best known example is that of a black hole where the force exerted toward the centre is inescapable and if you are making the rubber sheet version of space-time, you might draw it as a deep well. I'm not sure if that well is infinitely deep and whether the singularity depends on relativity and the speed of light as an upper limit. My (moderately educated) guess is that you can model it as an infinite attracting force but that physicists don't believe that can really be right, even though it may make no real difference.
 
 
grant
12:21 / 15.03.04
I think the deal with the rubber sheet black hole model is that it actually makes a hole, isn't it? Thus the whole idea with using black holes as gateways to other dimensions....

On the big bugs: this is a kid's-level page on the Goliath Beetle, which talks about the world's largest insect and has a menacing looking picture. And this has better images, with sizes.

The language of physics is indeed beautiful, even if (or especially if) you're an outsider like me.
 
 
Lurid Archive
12:57 / 15.03.04
A hole and a well which is infinitely deep at a point amount to the same thing. But I'm still sceptical about this. I mean, this is what the unification of physics is supposed to address, isn't it?

Other dimensions: one way to deal with the hole in spacetime is to make it a bridge - an Einstein-Rosen bridge - that allows you travel from one point to another via a non-conventional path, using black holes or, more likely, wormholes. (Like burrowing a tunnel in the earth, rather than going overland. Only much more freaky, since you would be burrowing through spacetime itself.) Also, IIRC, note that this is a hole in spacetime, so it theoretically allows time travel, too. Theoretically.

As a side note, I find some of the use of terminology confusing since physicists and mathematicians don't really think or speak in the same way. So, I wouldn't say that wormholes went through other dimensions (if they have both ends in spacetime). I'd say that they change the geometry of spacetime. Just like I'd say a hollow sphere is 2 dimensional, where a physicist would say it is 3.
 
  

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