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  Discussion about math, puzzles, games and fun.   Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ • π ƒ -¹ ² ³ °

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#101 Re: Guestbook » Unusually Quiet? » 2007-06-26 02:01:55

Quite likely... I haven't met anyone around here interested in math; even those few who are good at it pretend to be terrible at it because it "isn't cool" to be smart.

#102 Re: Euler Avenue » Small numbers and measures » 2007-06-25 20:35:50

A yottameter is roughly 9000000000 ly. This is farther away than the most distant star we can observe, even if we take into account the fact that that star is moving away from us, so the image that we get is "old" in that it doesn't correspond to where the star really is.

A yoctosecond is probably the time it takes an electron to make 1/10^99 of a revolution around its nucleus.

Measures are odd in that they may seem to be infinite, but they have a finite nature to them; there is a point at which a measure is so small or large that it is meaningless. For example, a yoctosecond (20^-24 seconds) is so short that nothing can happen during that time, therefore, it is meaningless. On the other hand, a yottasecond is longer than the current age of the universe, so it's pretty meaningless; it's longer than the time it would take a photon to go one yottameter.

#103 Re: Dark Discussions at Cafe Infinity » What shape is the universe? » 2007-06-25 20:16:49

Let's pretend we didn't start this confusing "conversation", OK?

#104 Re: Dark Discussions at Cafe Infinity » What shape is the universe? » 2007-06-25 00:54:08

Ah! You mean that, because the objects that we see are no longer in the positions in which we see them now, our perspective is distorted?

You could also be talking about something known as "redshift", which is the Doppler effect that light coming from an object far away and moving away from us has.

#105 Re: Introductions » hey » 2007-06-24 01:33:21

Not I. I'm somewhere far from the US, too.

By the way, welcome.

#106 Re: Introductions » Genius stuck in France » 2007-06-22 21:08:11

Oops!

I took a few videos of Friday. I didn't bring my other camera, but I'll do it when I go back Wed. to recuperate something that I forgot; a CD of some music.

You see, the idea of the day was that the morning was just for the students to prepare stuff for the afternoon. I signed up for the music group, which was called "music of the world". I figured I'd bring just that... I brought a CD of music from Finland. However, in the afternoon, we didn't get around to playing the music which had been set aside, so it stayed in the closet. Thus, I forgot it.

#107 Euler Avenue » Small numbers and measures » 2007-06-22 07:31:43

Laterally Speaking
Replies: 8

Here are the metric prefixes for all the denominations between 10^18 and 10^-18:

Yotta: 10^24
Zetta: 10^21
Exa: 10^18
Peta: 10^15
Tera: 10^12
Giga: 10^9
Mega: 10^6
Kilo: 10^3
Hecta: 10^2
Deca: 10^1

Deci: 10^-1
Centi: 10^-2
Milli: 10^-3
Micro: 10^-6
Nano: 10^-9
Pico: 10^-12
Femto: 10^-15
Atto: 10^-18
Zepto: 10^-21
Yocto: 10^-24

An atom is roughly between 10 and 100 nanometers across.
A quark is roughly 10 to 100 femtometers across (I said elsewhere that it was 1 or 2 attometers, but that was exagerated).

An exameter is roughly 9000 light-years.
A petameter is about 9 light-years.

As for the mostrecent additions to this list (Yotta, Zetta, Zepto, Yocto), they are beyond comprehension as far as measures go (the truth is, I can't really find anything to put them in perspective).

#108 Re: Euler Avenue » Number Giants » 2007-06-22 06:59:36

Not as big as G, but still probably larger than the distance between the two farthest apart observable planets in attometers (that's pretty big, being that the distance between said planets is around 1000 light years).

#109 Re: Euler Avenue » Number Giants » 2007-06-22 06:42:25

On a loosely related issue, a very small (positive) number can be obtained in the following way: 10^-(any number that has been posted here).

#110 Re: Dark Discussions at Cafe Infinity » Rubic's Cube solution » 2007-06-22 06:25:44

http://www.youtube.com/watch?v=wX4kZ4DEfzs

This is one heck of a cheater. Try pausing the movie right before he moves the cube off-screen; it is not solved.

Of course, it probably wasn't supposed to be a serious attempt.

#111 Re: Dark Discussions at Cafe Infinity » Rubic's Cube solution » 2007-06-22 06:09:32

What would really be amazing is someone who can do it blindfolded with one hand.

#112 Re: Dark Discussions at Cafe Infinity » Relative velocity (a physical demonstration) » 2007-06-22 04:49:02

Also, the ball used is not a tennis ball, but a golf ball, which wouldn't create as much friction as a tennis ball, so the spin would have to be more accentuated to make as much of a difference.

However, I agree that the spin is the most likely contributor to the angled bounce.

#113 Re: Dark Discussions at Cafe Infinity » Global Warming scenarios » 2007-06-22 04:37:19

Can you really prove that something is definitely going to happen? The causes are quite abundant, so it's probably far more likely to happen than it is to not.

As a matter of fact, might i ask why we're using the conditional future? It's happening right now! This year, we got about 1/10 of what we usually get, in terms of precipitations. The temperatures are higher than I remember them ever being. Still, SUV and 4x4 sales are rising every day, even though most of them are driven by people who only drive about 30 miles a day, alone, on perfectly paved roads...

#114 Re: Euler Avenue » Number Giants » 2007-06-21 04:19:06

I think that it's pretty obvious that if you use both iterations, factorials, Knuth's up-arrow notation, and Conway's chained-arrow notation, you can get absolutely mind-boggling numbers.

#115 Re: Introductions » Genius stuck in France » 2007-06-21 04:11:11

Tomorrow is the "open school day", so there aren't any classes. I think I'll bring my camera, get a good picture (or two, or three) of the class; the "official" one was pretty mediocre.

I might bring a video camera, get a half-hour or so of the craziness of the class.

I'll report back, in the (perhaps vain) hope that someone will care...

Sorry, but, like I said elsewhere, it's in my nature to be cynical...

#116 Re: Introductions » Know what? » 2007-06-21 04:04:32

Did you know that 96% of all statistics are made up on the spot?

I was going to say something along the lines of "oh, my. Another spammer", but that wouldn't really be polite, would it? Anyway, welcome to the general vicinity of this particular forum.

By the way, I can't really help it; it's in my nature to be rather cynical.

#117 Re: Dark Discussions at Cafe Infinity » How fruits rot » 2007-06-21 04:01:18

I heard that an experiment was recently done, in which they took a burger from MacDonald's, and a homemade one, and some fries from MD, as well as homemade ones, and let them rot for 10 weeks.

The result: all the food shrank, much like on the video, except for the MacDonald's fries; they did not change at all.

The conclusion: they're dangerously high in preservatives.

#118 Re: Jokes » Classics » 2007-06-21 03:55:52

What do you call a dog with no legs?
Matt

What's pink and soft and found between a monster's toes?
Slow runners

#119 Re: Dark Discussions at Cafe Infinity » Relative velocity (a physical demonstration) » 2007-06-20 17:39:44

It's also probable that the speed was slightly influence by the fact that it was traveling at 100km/h at a slight angle, rather than perfectly parallel to the road, thus the fact that the ball didn't fall straight down.

The angular discrepancy could also have to do with a slight difference in speed between the two wheels. If the upper one is spinning faster than the lower one, it would seem that the launcher is at an upwards angle.

#120 Re: Dark Discussions at Cafe Infinity » Anybody know how to become a power member? » 2007-06-20 09:25:09

What do you mean what does it mean? It's relatively obvious that it means something along the line of "If you aren't going to stick with the subject, launch a thread of your own to discuss whatever subject you're drifting towards on another thread" If this isn't clear, don't worry. I just reread it, and it didn't make a huge amount of sense.

#121 Re: Dark Discussions at Cafe Infinity » Relative velocity (a physical demonstration) » 2007-06-20 09:20:23

If you look closely at the video, you can see that, while in the air, the ball travels forward (in the same direction as the truck) about 3/4'. Also, the type of launcher used, if there is the slightest speed difference between the upper and lower wheels, could easily put a fair amount of spin on the ball. It is, nonetheless, quite odd that the ball should bounce so far forward.

Also on the video, it seems that the truck is much farther away than 17, 01 cm away when the ball hit the ground.

#122 Re: Euler Avenue » Number Giants » 2007-06-19 09:35:14

Here's another:

10!!!...!!! ((10^^^^^^^^^^1000000)!!!...!!! (10! factorials) factorials)

Actually, this might be smaller than G, but it's still enormous.

#123 Re: Dark Discussions at Cafe Infinity » What shape is the universe? » 2007-06-19 09:31:20

I said this somewhere else, but I'll say it again: if the universe is truly without boundaries, then we have no way to prove it, as it would look the same as if the boundaries were simply out of sight. If the universe wraps, which seems quite possible, then, in theory, if you set off in any one direction, you would end up at your point of origin, eventually.

This isn't really getting the conversation any further, but I figured I should say something.

#124 Re: Dark Discussions at Cafe Infinity » Time as perceived by the human mind » 2007-06-19 03:45:53

I mean picoseconds, even femtoseconds, perhaps even attoseconds. Not very far into the past. Ithink the thing is that you record information about something, and having that information in existence changes what happened, whereas if you have the machine record the information and delete it instantly, it's something else... In any case, it's pretty odd.

#125 Re: Dark Discussions at Cafe Infinity » Cyphers and Codes » 2007-06-19 03:43:11

Oh, is that why? Why are seconds as long as they are? Why are minutes 60 seconds? Why are hours 60 minutes? Why are there 24 hours in a day?

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