syntax252 Posted February 18, 2005 Posted February 18, 2005 OK--I understand that due to the Earth's rotation, that someone standing on the equator is moving 1000 MPH West to East. And I even understand that the Earth is going around the Sun, so we are moving at a speed that could be discribed as "just a hellin'." Now I got this kid who want's to know how fast the solar system is moving in the galaxy. Can any of you smart fellers help me on this? And while you are at it, you might as well figure out how fast the Galaxy is moving through space, because that is prolly what he's gonna want to know next. By the way, how many directions are we moving in at the same time? Any why doesn't that make us dizzy?
swansont Posted February 18, 2005 Posted February 18, 2005 OK--I understand that due to the Earth's rotation' date=' that someone standing on the equator is moving 1000 MPH West to East. And I even understand that the Earth is going around the Sun, so we are moving at a speed that could be discribed as "just a hellin'." Now I got this kid who want's to know how fast the solar system is moving in the galaxy. Can any of you smart fellers help me on this? And while you are at it, you might as well figure out how fast the Galaxy is moving through space, because that is prolly what he's gonna want to know next. By the way, how many directions are we moving in at the same time? Any why doesn't that make us dizzy?[/quote'] Our rotation is somewhere around 200 km/s about the galactic center. Moving through space has no meaning until you say with respect to what you want to measure. Which way we are moving depends on your coordinate system, but we are moving in only one direction - our motion is given by a single vector. One can also argue that we are not moving at all, and everything else is.
mcoy Posted February 19, 2005 Posted February 19, 2005 well, what i can say about the direction is, that the solar system is orbiting around the galactic center like how the earth orbits the sun. However, the earth's orbit around the sun stays the same although the earth (obviously) ous around the galaxy with the sun. The milky way galaxy also moves, but the direction is still unknown. That's because we cannot create a map, or a grid which shows the exact location of the galaxy, simply because the size of the universe and the point of origin (where it all began, big bang) is unknown.
syntax252 Posted February 19, 2005 Author Posted February 19, 2005 Does anyone know how fast the solar system is moving around the center of the galaxy?
swansont Posted February 19, 2005 Posted February 19, 2005 Does anyone know how fast the solar system is moving around the center of the galaxy? Yes.
ydoaPs Posted February 19, 2005 Posted February 19, 2005 Our rotation is somewhere around 200 km/s about the galactic center. .
syntax252 Posted February 19, 2005 Author Posted February 19, 2005 Oh, that's right, I forgot that post. 200 km pr sec? Comes down to about 125 MPS. That is moving right along. I get about 9.26 MPS for the Earth's orbit around the sun. Thanks
Syd Posted February 19, 2005 Posted February 19, 2005 Id say that Earth stand's still, and all the other things move round our planet. Copernicus was right, but so as I
Janus Posted February 19, 2005 Posted February 19, 2005 I get about 9.26 MPS for the Earth's orbit around the sun. Thanks This is too small by a factor of two.
us.2u Posted February 19, 2005 Posted February 19, 2005 Id say that Earth stand's still, and all the other things move round our planet. Copernicus was right, but so as I I believe we are rotating causing centrifugal force in turn creating our gravity I think if we were stationary there would be no gravity & we would be all lost in space I think that's correct...us.2u
syntax252 Posted February 19, 2005 Author Posted February 19, 2005 This is too small by a factor of two. You are correct. I used the radius of the orbit, rather than the diameter.
syntax252 Posted February 19, 2005 Author Posted February 19, 2005 I believe we are rotating causing centrifugal force in turn creating our gravity I think if we were stationary there would be no gravity & we would be all lost in space I think that's correct...us.2u I thought that gravity was the attraction between 2 masses. You say that gravity is caused by our orbit? Why is the gravity on the moon less that on the Earth? We are both going around the sun--right?
swansont Posted February 20, 2005 Posted February 20, 2005 I believe we are rotating causing centrifugal force in turn creating our gravity I think if we were stationary there would be no gravity & we would be all lost in space I think that's correct...us.2u Then why does the moon, which rotates about once a month, have gravity that is related to its mass and radius such that it about 1/6 or ours, rather than ~1/28?
mcoy Posted February 20, 2005 Posted February 20, 2005 You say that gravity is caused by our orbit? Why is the gravity on the moon less that on the Earth? We are both going around the sun--right? Yes, gravity does cause our orbit. And, the gravity of the moon is less than on the earth, because the density and mass of the moon is smaller than of earth's. The earth and the moon goes around the sun, but technically, the moon goes on its own orbit around the earth, therefore the earth goes around the sun with the moon along with it. ---sorry, just felt like mentioning
syntax252 Posted February 20, 2005 Author Posted February 20, 2005 Yes' date=' gravity does cause our orbit. And, the gravity of the moon is less than on the earth, because the density and mass of the moon is smaller than of earth's. The earth and the moon goes around the sun, but technically, the moon goes on its own orbit around the earth, therefore the earth goes around the sun with the moon along with it. ---sorry, just felt like mentioning[/quote'] I agree to that. But I thought that us.2u was saying that out orbit caused gravity rather than our orbit being the result of gravity. Did I misunderstand him?
us.2u Posted February 20, 2005 Posted February 20, 2005 To be openly honest syntax 252 I'm not sure either but we are definately not stationary hence our one year which it takes us to orbit our sun...us.2u
Ophiolite Posted February 20, 2005 Posted February 20, 2005 I am reading us.2u the same way as you. If we are correct I think he is confusing the gravity like effects of centrifugal force (or is it centripetal? I can never get my signs right.) with gravity itself. us.2u, if this is the case, rest assured that if the Earth were not rotating we would still be held very firmly in place. In fact we would weigh slightly more since our downward acceleration would no longer be balnced somewhat by the outward (upward) force imparted by the rotation.
us.2u Posted February 20, 2005 Posted February 20, 2005 To be openly honest syntax 252 I'm not sure either but we are definately not stationary hence our one year which it takes us to orbit our sun...us.2u Also I think with the amount of mass our Earth has & the speed it revolves (1000 mph approx) I think & believe this has something to do with why our gravity is stronger than that of our moon;I may be wrong sorry if this is misleading but hopefully someone with greater knowledge will support my theory or explain otherwise...us.2u
Tommio Posted February 20, 2005 Posted February 20, 2005 If we are correct I think he is confusing the gravity like effects of centrifugal force (or is it centripetal? I can never get my signs right.) with gravity itself. The way I understand it centrofugal force does not exist. The force that you are talking about is centropital and is the acceleration towards a centre, usually motion vector perpendicular to the acceleration. This is a stable and circular orbit.
mcoy Posted February 20, 2005 Posted February 20, 2005 Its centripetal mate, next time you got to make the spelling right.... ok
us.2u Posted February 20, 2005 Posted February 20, 2005 I always understood centrifugal force is a fact; look at a spin cycle from a washing machine & the small amount of mass that bears, well I think our planet reacts in a very similar way, whether you label this centripetal or centritfugal I think the end result is much the same...us,.2u without it I don't think any of us would have our feet on the ground...us.2u
syntax252 Posted February 20, 2005 Author Posted February 20, 2005 I always understood centrifugal force is a fact; look at a spin cycle from a washing machine & the small amount of mass that bears, well I think our planet reacts in a very similar way, whether you label this centripetal or centritfugal I think the end result is much the same...us,.2u without it I don't think any of us would have our feet on the ground...us.2u I was told that centrifugal force was the force that would try to make a weight fly off into space if it wasn't attached to something that prevented it, such as a string tied to a ball, or, as you said, the wall of the basket in the washing machine. I think that the washer is indeed an example of centrifugal force being applied to extract water from the wash. This other--centripetal force--again as I understand it, is the force that makes the planet want to fall into the sun, except that it is moving on a tangent to the orbit that prevents it from actually hitting the sun. That is probably wrong, but hopefully one of these smarter guys will fill us in in layman's terms?
Ophiolite Posted February 20, 2005 Posted February 20, 2005 I hate it when you guys make me use my small geologists brain to explain fundamental physics. Geology is so much vaguer, allows one to move continents, and has a really neat range of catastrophic explosions. What more could one want? Firstly, us.2u, gravity: We remain with our feet on the ground because the Earth is attracting us towards it and we are also attracting the Earth towards us. (It's not much of a contest, even if you are the size of Pavaroti.) The rotation of the Earth has absolutely nothing to do with this. If the Earth did not rotate we would still be attracted towards it, and it towards us. This relationship is expressed in Newton's law of universal gravitation. F=GMm/d^2 where F is the gravitational force M is the mass of one of the two bodies (say the Earth) m is the mass of the other body (say a kangaroo) d is the distance between the centre of gravity of the two bodies G is the universal gravitational constant whose value depends upon what units we have selected for the variables What this equation says is that the larger the masses involved the greater is the force of attraction - hence we weigh more on the Earth than we do on the moon, while on Venus we would weigh almost as much as on Earth. The equation also says the force is greater if the masses are close together - hence the tides are effected more by the Moon than by the Sun, because the former is much closer even though the latter is much more massive. Is that clear? Now centrifugal and centripetal force. Centrifugal force is something of an illusion. Consider Newton's first law of motion (Though Rene Descartes actually postulated the principle first.) - the velocity of a body remains constant unless acted upon by a force. Now velocity is not speed, but speed in a constant direction. In other words, unless we interfere with it a body will remain at rest or moving in the same direction at the same speed for ever. This property of carrying on regardless is called inertia. In the example of the spin dryer the clothes want to carry on in a straight line, but are restrained by the walls of the dryer. The water isn't. It is simply continuing in a straight line. This creates the appearance of a force throwing the water off and trying to throw the clothes off, but in both cases it is simply inertia. Hope that makes some kind of sense.
us.2u Posted February 20, 2005 Posted February 20, 2005 I think I'm slowly understanding Ophiolite; but the clothes in a spinner mixed with the rinse water I really thought that in my humble mind a prime example of centrifugal force; maybe this is incorrect or debateable? but I guess my simple example of my own kind of physics or how I percieved it is basically inadequate? I was trying syntax 252; definately not trying to mislead, sorry about that I guess better left to the physics guys....us.2u (Thanks Ophiolite)
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