posted
Hey, I have a question for you. When you don't reply to someone, does that almost always mean that you think their post is stupid and there's no sense in replying, or does it mean that you just can't think of anything to say in response, so you don't say anything?
Posts: 13123 | Registered: Feb 2002
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Geoff...were you actually looking for that or did it just accidentally pop up? I loved it!! That's one of those bizarre numbers that I need to memorize to freak people out. Posts: 75 | Registered: Sep 2003
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That's wonderful. I was quizzed on a date two weeks ago about the rate of gravity - how fast something falls in earth's gravity. I couldn't answer.
That's what I get for dating science geeks. It was very funny.
Posts: 26077 | Registered: Mar 2000
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posted
Kat, it's a trick question. First second? Second second? Twentieth second? 3000th second? (yeah, ok, that's a really long fall -- so?)
Just remember, things accelerate (on Earth, at sea level or a close approximation thereof) at about 10 meter/sec/sec. So, to know how fast it's going, just multiply the number of seconds times 10. If it's been falling 2 seconds, it'll be going 20 m/sec; 45 seconds, 450 m/sec.
[And yes, it's really 9.8 m/sec/sec -- but 10 is a good enough approximation for most things.]
Posts: 32919 | Registered: Mar 2003
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quote: Hey, I have a question for you. When you don't reply to someone, does that almost always mean that you think their post is stupid and there's no sense in replying, or does it mean that you just can't think of anything to say in response, so you don't say anything?
I think it means the person is such a smarty pants that their post has encompassed all possible opinion on the subject so there is nothing more to say. At least I hope that's why, if you research it, my posts have the lowest average reply count of anyone in Hatrack history. I even tried to start a game once, and I think it went down with a blaze of non-glory.
Posts: 11017 | Registered: Apr 2003
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"If you fall into a bottomless pit, you die of starvation."
It is a trick question, but not quite for the reason you gave, rivka. If the question is, as kat reports, "What is the rate of gravity?" it doesn't have a whole lot of meaning. What rate are we talking about? The rate of change of position (i.e. velocity) due to gravity? The rate of change of velocity (i.e. acceleration) due to gravity? The rate of change of the universal gravitational constant? And even if we can assume that he wants the acceleration due to gravity, where are we talking about? At the surface of the earth? At the surface of the moon? In deep space?
Next time you get a question like that, kat, ask him to be more specific.
Posts: 4534 | Registered: Jan 2003
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if you ever have some time to kill, NPR's Science Friday had an interview with the author of Google Hacks and one of google's co-founders, 2 fridays ago. They talk about some neat stuff, and Science Friday archives all of its old shows. So check it out.
Posts: 4482 | Registered: May 2000
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Oh, great. Now I'm going to have to find a way to use this piece of information in conversation. Posts: 2454 | Registered: Jan 2003
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LOL, sax, that's the difference between an engineer's answer and a (former) science teacher's answer.
I agree with you, though. It is, sadly, a question that is often phrased exactly that way. (Including by some of my former students, who ought to know better! )
Posts: 32919 | Registered: Mar 2003
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rivka, of course, you are assuming a vacuum. In the earth's atmosphere eventually counteracts gravitational acceleration, so that the speed remains constant.
That google feature rules, it even knows Avogadro's Number:
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@------>---- White rose of peace for Saxon. I remember the warg-pile on fil when I mistook him for filletted. Fortunately for me, I don't think there has ever been a HRer named Poo.
P.S. I almost used S.S. but didn't want to evoke whatever it is that that pertains to with Nazis.
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Now that you mention it, I think that would be a pretty funny nickname for certain people whose nicks begin with the letters 'poo'. Posts: 13123 | Registered: Feb 2002
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Actually, assuming that there was an atmosphere in the bottomless pit, wouldn't you be incinerated before you starved to death? And if there wasn't a breathable atmosphere, I expect you'd asphyxiate before you starved.
Of course, for either of these, I guess that how hungry you were when you fell in the hole might be a factor. Posts: 16059 | Registered: Aug 2000
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Noeman, I kind of like it, but this is the kind of thread that gets me the eye roll from my husband. He also rolled his eyes at the math joke thread and wondered why there were so many apparently bright people here that didn't have anything better to do all day long.
Posts: 9871 | Registered: Aug 2001
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The funny think, Kayla, is that just before you posted that, I was thinking "man, this is great--we're such a bunch of geeks!"
Posts: 16059 | Registered: Aug 2000
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Hmmm... You raise an interesting point, Noemon.
Let's contemplate the so-called bottomless pit. One possible bottomless pit would be a hole that goes all the way through the earth. We'll assume that it's a wide enough hole that you wouldn't be able to grab the sides and stop or slow yourself. Now, assuming you didn't die of a heart attack upon falling into the hole, you would almost certainly be incinerated well before reaching the planet's core. The problem is that the mantle and outer core of the planet are liquid, so just digging a hole wouldn't suffice to create a permanent bottomless pit; it would fill itself in in relatively short order. So you'd have to either cool the liquid into a solid state, or erect some sort of barrier around the hold to keep it from collapsing. Now, all of the industrial construction materials I can think of would melt or burn if you tried to use them to reinforce the walls of the pit, so we will have to further assume we have a high enough level of technology to erect some sort of force field (not a terrible leap, considering we have the technology to drill a hole all the way through the earth). And if we're going to assume such a force field being capable of holding such a massive amount of magma at bay, we might as well assume that it can keep the heat at bay as well.
So we have a hole through the center of the earth being reinforced by a heat-dampening force-field. What about atmosphere? I have to admit I'm not sure about this part. Would a combination of gravity, air pressure (really just gravity) and diffusion be enough to get enough air into the hole? If we posit a hole with a radius of, say, 20 meters, then we're looking at a volume of 8.01 billion cubic meters, which is by no means an insignificant amount. But if we assume that the bulk of the earth's atmosphere is within 7 km of the surface, the entire atmosphere has a volume of 3.58e18 cubic meters, so we would need only about two billionths of the atmosphere to fill the hole. This is wild hand-waving, now, but I think it's safe to assume that if we allow enough time after the construction of the hole, it will receive sufficient atmosphere to avoid asphyxiation.
Now, of course, we have the problem that the hole we've been considering is not quite what we envision a truly bottomless pit to be. Basically, a person unlucky enough to fall in would fall for a long time, overshooting the center of the earth and subsequently fall up the other side, almost reaching the surface (air friction would slow the ascent enough to prevent the hapless victim from getting all the way there). Then the person would fall back down again, and so on in a decaying oscillatory pattern, eventually coming to rest at the earth's center. I have no idea how long that would take, though.
What might be better is to construct a really long tube, the length of the whole universe. It would need some sort of method to propel the person down its length, but since we have the engineering skill to construct what amounts to an infinitely long tube, I think we can assume that they can come up with some type of propulsion. Modern physics tells us that the universe is finite but unbounded, such that if we travel far enough in one direction, we'll come back to where we started (the debate remains as to whether our left and right sides will be reversed when we get there, though). Our tube, then, would connect back on itself. The main problem here, though, is that there's no way in, so how would anyone fall into it?
What we really need is some sort of extra-dimensional hole that only has one end. But now we're moving into realms of mathematics for which I am completely unprepared.
Posts: 4534 | Registered: Jan 2003
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I loved it!! That's one of those bizarre numbers that I need to memorize to freak people out. ![[Evil]](graemlins/evil.gif)
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It was very funny.
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