# Very Basic Science That You Still Don't Understand **URL:** \ **Category:** Factual Questions\ **Created:** [November 20, 2001, 3:06pm UTC](https://boards.straightdope.com/t/very-basic-science-that-you-still-dont-understand/94401 "2001-11-20T15:06:26Z")\ **Posts on this page:** 16\ **Page:** 5
**Author:** ![Jman](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jman/32/4416_2.png) [@Jman](https://boards.straightdope.com/u/Jman)\ **Post date:** [November 26, 2001, 2:20pm UTC](https://boards.straightdope.com/t/very-basic-science-that-you-still-dont-understand/94401/81 "2001-11-26T14:20:09Z")
Yes, that’s exactly what they’re doing…falling horizontally fast enough that they miss the earth due to its curvature. That’s what puts an object in orbit. For a bullet to do the same thing, you’d need to have it in orbit too. You can’t have a bullet in orbit around the earth within the atmosphere due to wind resistance and friction. I’m not sure of the term that’s used for the speed to reach orbit at a certain angle. I was thinking it was “Escape Velocity,” but I believe that’s the speed needed to avoid the gravity of the earth entirely (ie, avoid going into orbit.) Jman ---
**Author:** ![lieu](https://avatars.discourse-cdn.com/v4/letter/l/c2a13f/32.png) [@lieu](https://boards.straightdope.com/u/lieu)\ **Post date:** [November 26, 2001, 2:39pm UTC](https://boards.straightdope.com/t/very-basic-science-that-you-still-dont-understand/94401/82 "2001-11-26T14:39:17Z")
You ever gotton to the end of a page and posted, only to realize later there are additional pages that have _ALREADY_ explained your answer in excruciatingly pleasant logic? My ego just encountered a mind-numming one-two punch. ---
**Author:** ![tsarina](https://avatars.discourse-cdn.com/v4/letter/t/f4b2a3/32.png) [@tsarina](https://boards.straightdope.com/u/tsarina)\ **Post date:** [November 26, 2001, 2:49pm UTC](https://boards.straightdope.com/t/very-basic-science-that-you-still-dont-understand/94401/83 "2001-11-26T14:49:17Z")
Here’s my science question that no one has ever been able to answer: When you charge up an object with static electricity, why do you need to use a natural fiber (running a comb through your hair, rubbing it with a piece of fur, etc.)? Does a natural fiber somehow move electrons easier than, say, polyester or nylon? ---
**Author:** ![RGillen](https://avatars.discourse-cdn.com/v4/letter/r/848f3c/32.png) [@RGillen](https://boards.straightdope.com/u/RGillen)\ **Post date:** [November 26, 2001, 3:34pm UTC](https://boards.straightdope.com/t/very-basic-science-that-you-still-dont-understand/94401/84 "2001-11-26T15:34:11Z")
> [@](#): > > \*Originally posted by ZenBeam \* > \*\* > > > [@](#): > > > > Which brings us to gravitons. In the current form of the standard model, doing math to find the theoretical mass of a graviton yields a relatively large number. > > The graviton is expected to be massless, like a photon. Maybe you’re thinking of the [Higg’s Boson](http://physics.about.com/library/weekly/aa092300a.htm?once=true&). Also, I don’t think gravitons are considered part of the Standard Model (yet). \*\* Yeah, you’re absolutely right. Sorry… ---
**Author:** ![billy](https://avatars.discourse-cdn.com/v4/letter/b/ecd19e/32.png) [@billy](https://boards.straightdope.com/u/billy)\ **Post date:** [November 27, 2001, 6:09pm UTC](https://boards.straightdope.com/t/very-basic-science-that-you-still-dont-understand/94401/85 "2001-11-27T18:09:19Z")
> [@](#): > > \*Originally posted by Greg Charles \* > \*\*Why does a ball with back spin tend to go up? I know it has to do with the Bernoulli principle, but it seems like the bottom of the ball is moving faster relative to the air than the top. That would mean the pressure on the bottom would be lower, and should force the ball down. \*\* The bottom of the ball is moving faster with respect to the air in the ballpark and this does involve the Bernoulli principle, but remember that air resistance is a function of speed. The bottom of the ball is moving faster so has a higher air resistance, this produces a ‘buildup’ of air at the bottom compared to the top. This ‘buildup’ at the bottom actually means that air is moving across the top of the ball faster than the bottom. And Bernoulli says that means lower pressure at the top, so it climbs. Don’t confuse the air around (and moving with) the ball with the air elsewhere. I think that is where your confusion comes from. ---
**Author:** ![billy](https://avatars.discourse-cdn.com/v4/letter/b/ecd19e/32.png) [@billy](https://boards.straightdope.com/u/billy)\ **Post date:** [November 27, 2001, 9:38pm UTC](https://boards.straightdope.com/t/very-basic-science-that-you-still-dont-understand/94401/86 "2001-11-27T21:38:21Z")
> [@](#): > > \*Originally posted by tronvillain \* > \*\*Greg Charles: > > > [@](#): > > > > Why does a ball with back spin tend to go up? I know it has to do with the Bernoulli principle, but it seems like the bottom of the ball is moving faster relative to the air than the top. That would mean the pressure on the bottom would be lower, and should force the ball down. > > [Bernoulli’s Theorem](http://dictionary.msn.com/find/entry.asp?refid=561501508&wwi=9338):the sum of the pressure and the product of one-half of the density times the velocity squared is constant along a streamline for steady flow in an incompressible nonviscous fluid at constant height. > > Looking at this, I suspect that in the ideal case the fact that the ball is spinning shouldn’t have any effect at all - the streamlines would be identical above and below and would have the virtually the same pressure (there is a small difference in height). However, we aren’t looking at the ideal case - air _is_ compressible and viscous and we have to take that into account. > > For a ball with backspin: > > 1)The top surface is trying to drag air from the front of the ball to the back, and the resulting decrease in density means lower pressure above the ball. > > 2)The bottom surface is trying to drag air from the back of the ball to the front, and the resulting increase in density means higher pressure below the ball. > > I suppose you could say that the streamlines on top are actually moving _faster_ and that the streamlines on the bottom are actually moving _slower_, but it’s not really as satisfying when you put it that way. > > Now, to sit back and hope I’m not torn apart. \*\* Sorry TRONVILLAIN, I answered before seeing you had nailed it. We used different words but said the same thing. CURTC on the otherhand, had a real departure… ---
**Author:** ![Greg\_Charles](https://avatars.discourse-cdn.com/v4/letter/g/839c29/32.png) [@Greg\_Charles](https://boards.straightdope.com/u/Greg_Charles)\ **Post date:** [November 27, 2001, 10:23pm UTC](https://boards.straightdope.com/t/very-basic-science-that-you-still-dont-understand/94401/87 "2001-11-27T22:23:44Z")
> [@](#): > > \*Originally posted by lieu \* > \*\* > My ego just encountered a mind-numming one-two punch. \*\* Plus, you misspelled “numbing”. Note to self: in the future, try to resist kicking people when they’re down. (Even if does make me feel better about continued confusion regarding spinning baseballs.) ---
**Author:** ![The\_Great\_Gazoo](https://avatars.discourse-cdn.com/v4/letter/t/67e7ee/32.png) [@The\_Great\_Gazoo](https://boards.straightdope.com/u/The_Great_Gazoo)\ **Post date:** [November 27, 2001, 10:36pm UTC](https://boards.straightdope.com/t/very-basic-science-that-you-still-dont-understand/94401/88 "2001-11-27T22:36:36Z")
> [@](#): > > \*Originally posted by CrankyAsAnOldMan \* > \*\*I’m still having trouble with string theory, but that’s not basic science so I’ll pass on asking about that one. Same with relativity. > > But here’s a basic one I don’t get. When you throw a ball up into the air, what is its speed/velocity (if any) at the apex of the arc? That is, at the moment it stops climbing up and starts falling down? My fricking physics teacher was a biology teacher who took a summer of physics to get her prepared for teaching us (science teacher shortage) and she gave us two answers and for the life of me I can’t remember which was true or if I should even believe her. \*\* I have trouble with string theory, too. Have they got the calculations to collapse to 10 dimensions yet? or is it still 24 dimensions? or is it infinite dimensions? ---
**Author:** ![Mr.Miskatonic](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mr.miskatonic/32/310_2.png) [@Mr.Miskatonic](https://boards.straightdope.com/u/Mr.Miskatonic)\ **Post date:** [November 27, 2001, 10:38pm UTC](https://boards.straightdope.com/t/very-basic-science-that-you-still-dont-understand/94401/89 "2001-11-27T22:38:32Z")
> [@](#): > > \*Originally posted by tsarina \* > \*\*Here’s my science question that no one has ever been able to answer: > > When you charge up an object with static electricity, why do you need to use a natural fiber (running a comb through your hair, rubbing it with a piece of fur, etc.)? Does a natural fiber somehow move electrons easier than, say, polyester or nylon? \*\* Not neccessarily. After all, what is that shag rug you just scuffed your feet on made of? I doubt its very natural. ---
**Author:** ![The\_Bad\_Astronomer](https://avatars.discourse-cdn.com/v4/letter/t/f05b48/32.png) [@The\_Bad\_Astronomer](https://boards.straightdope.com/u/The_Bad_Astronomer)\ **Post date:** [November 27, 2001, 11:07pm UTC](https://boards.straightdope.com/t/very-basic-science-that-you-still-dont-understand/94401/90 "2001-11-27T23:07:38Z")
> [@](#): > > \*Originally posted by Mr. Miskatonic \* > Not neccessarily. After all, what is that shag rug you just scuffed your feet on made of? I doubt its very natural. Given your alma mater, **Miskatonic** , I do _not_ want to know what _your_ shag rug is made of. ---
**Author:** ![BalmainBoy](https://avatars.discourse-cdn.com/v4/letter/b/6a8cbe/32.png) [@BalmainBoy](https://boards.straightdope.com/u/BalmainBoy)\ **Post date:** [November 28, 2001, 2:07am UTC](https://boards.straightdope.com/t/very-basic-science-that-you-still-dont-understand/94401/91 "2001-11-28T02:07:06Z")
From a Sydney poster: When you look at a full moon (next one in 7-8 days time) from Sydney, most of the grey patches (the mare, or lava fields) stretch from about the 6 o’clock to the 10 o’clock positions. We don’t see a “man in the moon”, as the moon’s disc has been rotated; due to our angle of incidence from the direction of the moon. Here’s one that puzzles me: light travels very fast - 186000 miles / second. When you look at something just above a fire, the image ripples, due to the heat in the air above the fire. But how can this affect light, due to its high speed? Since light travels in a vacuum, it doesn’t need a medium (eg air) to travel in, as sound does. So, to my thinking, the movement of air above the fire shouldn’t affect the passage of light. Anyone? ---
**Author:** ![ShibbOleth](https://avatars.discourse-cdn.com/v4/letter/s/848f3c/32.png) [@ShibbOleth](https://boards.straightdope.com/u/ShibbOleth)\ **Post date:** [November 28, 2001, 2:33am UTC](https://boards.straightdope.com/t/very-basic-science-that-you-still-dont-understand/94401/92 "2001-11-28T02:33:59Z")
> [@](#): > > \*Originally posted by BalmainBoy \* > \*\*From a Sydney poster: > > Here’s one that puzzles me: light travels very fast - 186000 miles / second. When you look at something just above a fire, the image ripples, due to the heat in the air above the fire. But how can this affect light, due to its high speed? Since light travels in a vacuum, it doesn’t need a medium (eg air) to travel in, as sound does. So, to my thinking, the movement of air above the fire shouldn’t affect the passage of light. > Anyone? \*\* Light can travel in a vaccuum, and doesn’t need a medium to travel in, but that doesn’t make it impervious to the media it does travel through. Otherwise glasses wouldn’t work. And lightshades wouldn’t keep out the light, would they? The light is affected by the movement of the hot air above the fire. ---
**Author:** ![billy](https://avatars.discourse-cdn.com/v4/letter/b/ecd19e/32.png) [@billy](https://boards.straightdope.com/u/billy)\ **Post date:** [November 28, 2001, 2:56am UTC](https://boards.straightdope.com/t/very-basic-science-that-you-still-dont-understand/94401/93 "2001-11-28T02:56:28Z")
> [@](#): > > \*Originally posted by ShibbOleth \* > \*\* > > > [@](#): > > > > \*Originally posted by BalmainBoy \* > > \*\*From a Sydney poster: > > > > Here’s one that puzzles me: light travels very fast - 186000 miles / second. When you look at something just above a fire, the image ripples, due to the heat in the air above the fire. But how can this affect light, due to its high speed? Since light travels in a vacuum, it doesn’t need a medium (eg air) to travel in, as sound does. So, to my thinking, the movement of air above the fire shouldn’t affect the passage of light. > > Anyone? \*\* > > Light can travel in a vaccuum, and doesn’t need a medium to travel in, but that doesn’t make it impervious to the media it does travel through. Otherwise glasses wouldn’t work. And lightshades wouldn’t keep out the light, would they? > > The light is affected by the movement of the hot air above the fire. \*\* Light is NOT affected by the movement of air. If it was, windy days would be like an acid trip. Light is affected by the changes in density of the air. Hot air off the flame is less dense, so has a different index of refraction. This refraction index makes a difference in how fast light travels through the medium. When the hot and cold air begin to mix above the flame, the bounderies between the hot and the cold (less dense and dense)air bend the light (like the boundy between glass and air, water and air, water and glass, etc…) and gives off the rippling effect you mention. There used to be this old guy named Hero that postulated that light will travel in whatever path will get it there fastest. Because it can get through the less dense (warm) air quicker, if needed, it will take a detour from a straight path, to get into the less dense air, and then be on it’s way… How does the light know which path will get it there fastest??? you may ask. It doesn’t, any more than water knows how to find the floor or to lay flat across the top of a lake. It just happens. ---
**Author:** ![ShibbOleth](https://avatars.discourse-cdn.com/v4/letter/s/848f3c/32.png) [@ShibbOleth](https://boards.straightdope.com/u/ShibbOleth)\ **Post date:** [November 28, 2001, 3:44am UTC](https://boards.straightdope.com/t/very-basic-science-that-you-still-dont-understand/94401/94 "2001-11-28T03:44:16Z")
**Billy** , thanks for the correction! I was a bit absorbed in trying to decide whether it was a serious question that I got a bit sloppy. It would make windy days more interesting, non? ---
**Author:** ![Ring](https://avatars.discourse-cdn.com/v4/letter/r/6a8cbe/32.png) [@Ring](https://boards.straightdope.com/u/Ring)\ **Post date:** [November 28, 2001, 3:50am UTC](https://boards.straightdope.com/t/very-basic-science-that-you-still-dont-understand/94401/95 "2001-11-28T03:50:11Z")
> [@](#): > > There used to be this old guy named Hero that postulated that light will travel in whatever path will get it there fastest. It’s Fermat – Fermat’s principle of least time. If you want to understand it look up QED (Quantum ElectroDynamics.) ---
**Author:** ![billy](https://avatars.discourse-cdn.com/v4/letter/b/ecd19e/32.png) [@billy](https://boards.straightdope.com/u/billy)\ **Post date:** [November 28, 2001, 6:17am UTC](https://boards.straightdope.com/t/very-basic-science-that-you-still-dont-understand/94401/96 "2001-11-28T06:17:35Z")
> [@](#): > > \*Originally posted by Ring \* > \*\* > > > [@](#): > > > > There used to be this old guy named Hero that postulated that light will travel in whatever path will get it there fastest. > > It’s Fermat – Fermat’s principle of least time. If you want to understand it look up QED (Quantum ElectroDynamics.) \*\* I want to be careful here because you seem to have an quantum background but I’m gonna go ahead and try not to get punked. Hero first made the case for this fastest time thing, Fermat later came along and reworded it to something akin to what I have above. Either Fermat, or someone else later massaged his thoeries into a more precise version that dealt with non-variances in optical path lengths being used to define the path, which isn’t exactly the fastest time theory but seemed close enough for this forum as I figured very few would understand what “non-variances in optical path lengths” means. **I seem however, to have underestimated the audience. My apologies.** [Previous page](https://boards.straightdope.com/t/very-basic-science-that-you-still-dont-understand/94401.md?page=4)