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Comment Re:first? or third? (Score 2) 186

The galaxy rotation problem is basically this: Stars towards the edge of galaxies (mainly spiral galaxies) rotate much faster than they should based on Newtonian gravitation using only the visible material (the Einstein corrections are negligible at the speeds and distances being talked about, so they can't account for the differences). To explain this, you have basically two options: MOND, MOdified Newtonian Dynamics (ie., changing the laws of the universe at large distance scales like kiloparsecs), or dark matter (which can include baryonic dark matter as well, but generally refers to non-baryonic things), which corrects for it by assuming that there's a vast halo of objects that outweighs everything else in the galaxy and thus speeds up the rotation of objects far away from the galactic core.

The evidence at the moment seems to be in favor of dark matter, and in any event I have some doubt that we will ever see "examples at the same scale of pure baryonic matter interactions" as you put it; it may be that the phenomena in question are simply things that appear on the very large scale and aren't observable on the small scale, just the same way that relativity only becomes important under certain conditions and Newtonian dynamics works perfectly well in our "normal" world. (But I'm not an astrophysicist, just aiming to be one!)

Comment Re:What? (Score 1) 108

Well, not so much gravity as the atmosphere (drag eventually makes your orbit intersect the Earth's surface). Anyways, the license itself is reasonable enough for liability purposes (delineating who is responsible for the payload when returned), as practically all previous satellites that have reentered the atmosphere have been governmental. And this is a controlled, purposeful reentry, not a laws-of-physics demanded one.

Comment Re:My recollection is that this is not new (Score 2, Informative) 285

Check the Encylopedia Astronautica (astronautix.com). Even if they don't have your ATK/Morton Thiokol related article, they do have quite a lot of information related to spaceflight and space technology. I think you have the broad outlines correct, though, Hatch himself actually played something of a role (ISTR) in using the 156" solids instead of the Aerojet 260" (which would have been made in Southern Florida in a monocasing design and barged north to the Cape) ones. There were some other factors (mainly the use of rockets, such as the Titan III, that also used similar-sized segmented SRBs), but politics played a big role in that selection.

Comment Re:more expense (Score 1) 213

Well, there's a good reason for that; the United States doesn't need 200 knot torpedoes or supersonic anti-ship cruise missiles because it's enemies hardly even have navies worthy of the name, let alone the sophisticated anti-cruise missile defenses the US has (because of those supersonic AShMs), or our very quiet submarines (because of those torpedoes). Those kinds of weapons are only really useful for anti-ship warfare, and since other countries need to conduct that type of warfare in a hypothetical "war with US" scenario than we do, we invest much less in them than we do in other technologies that we get more use out of. For example, we have excellent smart bombs and stealth technology because we heavily rely on air power as a force multiplier and the countries with the fast torpedoes and AShMs have good air defense systems.
Science

Sciencey Heroes For Young Children? 614

An anonymous reader writes "Unhappy that all his friends have heroes he knows nothing about (they've all chosen hockey players — actually a hockey player: Sidney Crosby), my eight-year-old son asked me if I would find him a 'cool hero.' When pressed to define 'cool,' he very earnestly gave me this list of acceptable professions: 'Astronauts, explorers, divers, scientists, and pilots.' A second and only slightly less worthy tier of occupations includes 'inventors, meteorologists, and airplane designers.' To be eligible for hero status, an individual must be (1) accomplished in one of these fields, (2) reasonably young (it pains me to report that Dottie Metcalf-Lindenburger, NASA's youngest astronaut and now just 31, barely makes the cut), and, critically to my naive son's way of thinking, (3) respected by third graders nationwide. Ignoring that last criterion, or not, what heroes would you suggest from the sciences as people whose lives and accomplishments would be compelling to an eight-year-old mind?"

Comment Re:Quantum computers aren't X times faster. (Score 2, Insightful) 246

Actually, that's not true. When you factor in security theater and having to arrive at the airport early, and have fast trains, you can travel hundreds of kilometers on a train before a plane trip started at the same time can catch up. That's why high-speed rail is successful in Europe and the NE Corridor compared to most of the United States; the latter has longer distances and slower trains.

Comment Re:So convince me, then (Score 1) 1046

Hate to reply to my own posts, but oh well...

Also, just because the Earth has feedback cycles that will (probably) keep us from turning into Venus doesn't mean the new equilibrium is something we will like. In this case, it's like the a/c is being set by someone you can try to influence, but not yourself...if you do it wrong (pump loads of greenhouse gases into the atmosphere--note that people are worried about CH4, NO, etc., too--the really powerful stuff), then maybe the a/c will be set to 90 degrees (Fahrenheit) and you'll get to enjoy sweating it out inside the house...

Comment Re:So convince me, then (Score 1) 1046

If the first is false, then there is no global warming. If the second is false, there is no way to prove the third, because we would have examples of the warming going past this point and then correcting. If the third is false, then we need take no action. If the fourth is false, then we need take no action. If the fifth is false, then any action we could take would likely be meaningless.

Your statements of the meaning of the second through fourth points are off. In actuality, (2) is known to have happened; it is known that (3) is not true (ie., that there are feedback cycles that can kick in to keep the Earth from turning into Venus); however even with (2) and (3) being that way (that there have been high temperatures in the past and that there are extreme feedback mechanisms in place) that doesn't mean there won't be catastrophic impacts. A comparison might be an air-conditioning system and a space heater. Suppose the air-conditioning system is much more powerful than the space heater. However, it takes a while to kick in. In the meantime, it will get awfully hot around the space heater.

What is the optimum temperature (or range) of the Earth?

This of course will depend on who you talk to. A polar bear will want it a lot colder than a tarantula, for instance. But for our purposes, it's fine to just consider human impacts. In that case, temperatures in the range of those we had when most of our current cities and population centers grew up would be best, as that would mean that none of them ought to end up frozen, flooded, or burning. So that means the average temperature in the period 1900-1950 or so.

When has it been at that temperature in the past?

Well, obviously 1900-1950. It has surely been at about that temperature at many other times, as we know that it's been hotter and colder than that at various points

Has it ever been outside that temperature in the past?

Yep. Loads hotter in the Mesozoic or Carbonaceous. Colder in the Little Ice Age.

How, specifically, do we know this?

Well, direct measurements for the latter. Palaeontological evidence for the first two, such as the presence of huge tropical swamps and giant insects in the Carbonaceous. I'm not a geologist or palaeoclimatologist, though, so I can't really describe the methods by which they figure the temperatures of historical periods that well.

In particular, how does one define the temperature of the Earth, and how does then measure that?

Well, like I said that's not my area of expertise. I'm perfectly willing to say that the people who DO have that as their area of expertise have doubtlessly thought about it a lot and come up with some good indicators, though, based on my experience in physics.

Comment Re:Article needs a course in experimental design (Score 1) 96

However, there's no practical way for him to get data that would allow him to conclude causation. With only one test subject, and presumably being aware of the differences between regular and decaf coffee, he cannot perform a blinded study. In this case, the best he can do (without getting very silly) is to look at the data, see if it has a strong correlation (which apparently it did), and examine if there were any confounding variables that might have altered. For example, he might have changed jobs from one allowing little sleep, and much of that irregular, to one allowing much more regular sleep, which might cause similar effects. In the event that there aren't any confounding variables he can detect, then that correlation is the best evidence he can get that whatever he happens to be doing (in this case, not drinking coffee) is better than whatever else he could be doing.

(BTW, the fallacy is actually reverse ad populum. After all, he was arguing that everyone not doing it meant it was better.)

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