| Author | Message | ||
     Blake |
Tale section. Where the *hell* did your manners go?  | ||
| Blake |
Jim, Some definitions are in order... Centripetal Force: In curvilinear motion the component of force that is directed toward the center of curvature or axis of rotation and being normal to the heading of the body upon which it acts. This is the component of force of any origin acting to cause a particle or body to follow a curved rather than straight path. Gravity: The natural force of attraction between any two massive bodies, which is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. As it does on everything orbiting the Earth, gravitational acceleration can certainly act as a centripetal force, as can tire grip inthe case of an automobile or motorcycle, as can the wings, rudder, and elevators of a fighter jet with the effects of aerodynamics, as can the chords of a bolo with the effects of strong arms and simple dynamics, as can a rotating space station. Gravity and centripetal force are two independent physical phenomenon that may or may not find relation in certain scenarios. It's kinda strange. We really don't know what the heck gravity is. The most basic and powerful of common everyday physical phenomenon, and we are utterly baffled by it. If that cannot teach us humility, nothing can. | ||
| Dynarider |
Hmm, I looked before I posted that & it wasnt there? Now it is. Thanks Blakey.  And manners? Its 3am, its just you me & the snowplow drivers up. | ||
| Hootowl |
"It's kinda strange. We really don't know what the heck gravity is. The most basic and powerful of common everyday physical phenomenon, and we are utterly baffled by it. If that cannot teach us humility, nothing can." Yes, gravity sucks doesn't it? P.S. Gravity is the weakest force, not the strongest. | ||
| Jima4media |
Blake, You said - "As it does on everything orbiting the Earth, gravitational acceleration can certainly act as a centripetal force" Can act or DOES act? Can is a pretty weak statement for something that actually happens. http://www.physicsclassroom.com/Class/circles/U6L4a.html | ||
| Blake |
Jim, See my post above. Gravity is NOT synonymous with centripetal force. The statement using the word "can" is accurate. After all, it is certainly possible for gravity to pull parallel to an objects heading, or even not perfectly perpendicular to an object's heading. If something travels straight with no change in course, where is the centripetal force? Answer... There is none. | ||
| Blake |
Hoot, You are correct. I was speaking from a "human on Earth" perspective, not from a formal physics perspective. | ||
| Hootowl |
I know, I was just diggin' on you a little. I so rarely get the opportunity. | ||
| Aesquire |
I am afraid you have it sideways. Gravity is not an"attractive" force. The earth does not suck. Gravity is emitted by the background of the universe, as a repulsive force, and is blocked by matter. The universe blows.  {I could be wrong} | ||
| Jima4media |
Aesquire, I think you have it right too. Gravity is a pseudo force like centrifugal force. Another theory - gravity is neutrinos bombarding us from all directions. Now for both you and Blake - What is the force that causes electrons to orbit neutrons, the moon to orbit the earth, and the earth to orbit the sun, and galaxies to spiral? Jim | ||
| Hootowl |
Electrons do not orbit Neutrons. Nor do they "orbit" anything else. We're not exactly sure what pattern they take around the nucleus, the latest theory simply calls them an "Electron Cloud" We can't see the electrons without disturbing their position or velocity so no one really knows. Except that everyone seems to agree that they are not on orbit. Newtonian physics do not apply at the molecular level. | ||
| Aesquire |
Electrons hang out till the switch is thrown. The moon "orbits" the earth? It's falling toward it all the time but keeps missing. Ditto Earth/Sun Sun/Galactic center. Most stuff fell but didn't miss, only stuff that keeps missing "orbits". | ||
| Aesquire |
Real world physics is odd. The Moon slowly spirals AWAY from the Earth, tidal forces bleed energy through friction, producing heat & exchanging potential/kinetic energy. | ||
| Jima4media |
Ok Hoot, just seeing if anyone was awake out there. Aesquire, Where, exactly, is the friction between the moon and the tides? | ||
| Blake |
Jim, The friction is between the Earth and the tides. The Earth rotates in the same direction that the moon orbits, counterclockwise if viewed from out in space while looking down upon the north pole. The Earth rotates at a much faster rate than the moon orbits. The earth spins at 1 rpd (revolution per day) where the moon orbits at a rate of one orbit per 29.5306 days. You know of course that the gravitational pull of the moon causes two bulges (tides) in the Earths oceans, the major and minor tides. The major tide occurs due to the stronger pull of the moon on the near side of Earth. The minor tide results from the lesser pull of the moon on the far side of the Earth. Gravity being inversely proportional to the distance squared, the Earth's diameter becomes a significant factor wrt the moon's gravitational pull. Thus the Earth ends up being subjected to a differential lunar gravitational force. More on the near side, less on the far side. So anyway, the spinning solid Earth with friction acting to keep the oceans spinning at the same rate, acts to move the tidal bulges, both major and minor, a slight bit ahead of the moon. Thus the slight little bit of added mass of the major tidal bulge leads the moon by a little bit and thus adds a tiny tiny percentage of tangential (to the moon's heading) gravitational pull acting on the moon. Thus the Earth's spin is slowing due to moon gravitational effects coupled with tidal friction effects, and the moon is spiraling away (currently at 3.8 cm/yr). It is a prime example of the law of conservation of angular momentum with the system being the Earth and the moon. Cool eh?  A quick google web search yielded the following exemplary illustration...  Read more at http://www.talkorigins.org/faqs/moonrec.html. | ||
| Blake |
How's that for bringing the thread back on topic.  As to your question... What is the force that causes electrons to orbit neutrons, the moon to orbit the earth, and the earth to orbit the sun, and galaxies to spiral? Electrons? Me not know. Some kind of subatomic force. Of course there's always those pesky protons with their strong opposite charge attraction. Not gravity. Don't know what it is. Or has atomic physics advanced once again since I was in school. I don't keep up with it much. You do know that everything is mostly nothing, right? Moon orbiting Earth? Gravity and momentum, aka kinetic energy. Other factors affecting the lunar orbit are as mentioned above, tidal friction, and also there is the solar wind. Earth orbiting sun? Gravity and momentum/KE. Without the kinetic energy, there would be no orbit, no centripetal force, just a big collision of planetoids. Are you disputing that gravity "can" act as a centripetal force but that it does not *always* do so?... As in the component of gravitational force acting to cause the moon to recess, or simply the force that causes a rock to fall? Take two motorcycles into space. Tie them to opposite ends of a 30 FT long rope. Impart unto them a rotation as a system. What happens? The rope tightens and the bikes appear to orbit the center of the rope. There is no significant gravitational effect, only the force of tension carried by the rope, the force that keeps each bike from flying away in a straight path, the centripetal force. No actual motorcycles were harmed in this virtual experiment, but even if they were, AMA Pro Racing would surely specify that they be of the UJM persuasion of which we have entirely too many anyway. | ||
| Aesquire |
Blake, Thanks! Talk about a picture worth a thousand words. Centripetal force is more a condition than a "force". You can view many things from both sides of the "equation" (see semi-sarcastic gravity comment from me above). Some of what I have learned in this thread is that Gyro effects do help with turning, Precess acting to accelerate bike on roll axis (front to rear imaginary axis). I suspect the wheel gyro "inertial" effect offsets that, so net effect is more gyro effect / heavier wheel, increases steering effort. | ||
| Joey |
If that picture was drawn to scale, we would be looking at tides of over 1000 miles. | ||
| Mikej |
Someone once told me that if the earth was the size of a billiard ball that the earth would be smoother than that billiard ball. Don't know if it's true or not, but I think of that when I'm on the sides of some mountains.  Scale is everything, scale is relative. Apart from that I have nothing to add to this conversation, except that I don't like falling down on a bike. | ||
| Jima4media |
But there aren't any tidal effects on planets with moons, and without water. I guess everything got it's spin from the big bang when everything was colliding with everthing else, and the bigger objects spun smaller objects into their orbits, about 10 billion years ago. That was a good article Blake, but you do realize it was written to refute Creationist theories don't you? Everything is decaying through entropy and the end is eventually here. It seems so futile. ;-) | ||
| Blake |
Aesquire, I thought you'd like that. "Centripetal force is more a condition than a "force"." I have to disagree with you there though. It is a force, nothing more, nothing less. Not much different than a column being subjected to a "compressive" force, or a tightened cylinder head bolt being subjected to a "tensile force", or a solenoid actuating via a "magnetic" force. "Some of what I have learned in this thread is that Gyro effects do help with turning, Precess acting to accelerate bike on roll axis (front to rear imaginary axis). I suspect the wheel gyro "inertial" effect offsets that, so net effect is more gyro effect / heavier wheel, increases steering effort." If the gyro effect makes steering more difficult and sluggish, exactly how does it "help" with turning?  | ||
| Aesquire |
Blake. I was referencing your post @ Monday, December 30, 2002 - 04:30 pm in that precession does "assist" in initiating lean, re-reading that post you say (correctly) that it is an insignificant 2nd order effect. Gyro effect only "helps" as seen above. You phrased it better.  | ||
| Aesquire |
Jim. Fluids (not necc. water) see tidal forces. See Io, moon of Jupiter hot sulfer volcanos powered by tidal heating. (we think). Molten iron planetary cores, even "solid" rock flexes. of course to scale, earth is LOTS smoother than a billiard ball. My feet hurt 'cause they're on an inconveniant scale.  | ||
| Blake |
Joey, You are correct, if the illustration were drawn to scale, you wouldn't be able to see a difference. Nevertheless the effect is real and significant. Jim, "But there aren't any tidal effects on planets with moons, and without water." Not entirely true. There are secondary "tidal" effects generated in the atmosphere and also the planet's crust. But those are much less significant than the effects of liquid oceans. I'm not sure what your point is though. No one is saying that all moons recess significantly from the planet that they orbit. Our moon recesses at 3.8 cm per year. That is pretty significant when considered over a billion years. Three point eight billion cm is equal to 38,000 Km or 23,600 miles. Yes I noticed the site was intended to refute claims made by creationists. The point offered is that tidal effects at the time of Pangea (one big continent) were significantly less than they are now with basically four major land masses impeding tidal flow. The point definitely has validity. Without multiple obstacles (continents) to impede flow, the amount that the tidal bulge leads the lunar orbit would diminish significantly. Do we even have a sound idea of how the moon and its orbit came into being? The debate sure is interesting to follow. Both sides need to get real, drop their agendas and join forces in search of the truth. Either way, the effects on my spiritual beliefs and faith are nill. It is just interesting to contemplate. | ||
| Jima4media |
I subscribe to the 80% of everything we know is wrong theory. I picked that theory up from the Firesign Theatre of all places, but it continues to work pretty well. I was reading today about 30 problems with the Big Bang Theory, and why scientists think that is wrong. So, who knows how everything began? Jim | ||
| Aesquire |
I'm pretty open on origin theory's. I like the collision theory of Lunar origin. Mars size rock hits earth, big splash, pretty computer graphic. | ||
| Blake |
Jim, Even absent its scientific flaws, here's my problem with the big bang theory. It describes a cyclic never ending process, bang, expand, collapse, bang, on and on forever. It doesn't describe where all the matter comprising our universe originated. There simply had to have been a creator, something that transcends time and place, something able to separate nothing into its constituent parts, something and anti-something. The evidence is so plane and simple you'd have to be blind or exceedingly arrogant to miss it. | ||
| Joey |
Is that why the tendency is for scientists to gain more faith as they learn more? Too many things fitting together in too complex ways to have not been planned... | ||
| Rick_A |
I think the whole creator theory...which to me is obviously more theory than fact...is just man trying to explain simply that which we do not know. ...and if that theory is the case, then who created the creator, and its creator, and the creator before that...  | ||
| Jima4media |
Isn't it ironic that all conversations eventually devolve into a science/religion debate, or gun control / political debate? Even motorcycle steering. ;-) |
