This'll probably sound quite stupid to those of you who know about this sort of thing but I'll ask anyway...
Why do objects such as planets orbit the sun rather than just falling into it?
Thanks.
[ June 07, 2003, 09:20 AM: Message edited by: Wraith ]
Posted by Krenim (Member # 22) on :
The Earth is always falling towards the sun. It's just that the Earth has such a high velocity in a direction perpendicular to that of the pull of the sun that it keeps missing it. That's how orbits work.
Posted by Jason Abbadon (Member # 882) on :
Wait, let me say the idiotic answer before some religous nut chimes in: "Because God makes it so". There! Now we can really discuss the beguiling effects of planetary gravitation.
Newton explained that the gravitational force between two objects depended on the mass of each object and the distance between them. The greater each object's mass, the stronger the pull, but the greater the distance, the weaker the pull. Our solar system is a balance of objects of differing masses moving at differing velocity around the sun (the single largest mass in the solar system). The second largest masses in the system (Jupiter and Saturn) have small sub-systems of moons and debris orbiting them in much the same way.
Posted by Cartmaniac (Member # 256) on :
All celestial bodies follow the curvature of spacetime, which we perceive as gravity.
Newton and everyone else, pre-1915: "huh?"
Posted by Jason Abbadon (Member # 882) on :
All of Einstein's theories were based on principles Newton put to paper. Even now many of Einstein's theories are under debate while most of Newtons remain immutable.
Gravitation is one of the few subjects that will be under scrutint as to it's Mechanics long after we're all dead. If that's any consolation... Posted by Cartmaniac (Member # 256) on :
True, Einstein stood on the shoulders of giants, but so did Newton. Doesn't matter, they both have their place in history, and wether Newton's mechanics will outlive Einstein's GRT is hardly a measure of individual greatness, anyway.
Posted by Jason Abbadon (Member # 882) on :
Agreed. It still leaves the ever-pending questions of gravity's origin and true nature hanging. We can measure it's effects on both energy and matter but we still don't understand it's relationship to the universe's mechanics any more than Newton did.
Posted by Cartmaniac (Member # 256) on :
Nah... but we're at the border of a whole new domain of physics, combining QM and GRT to give us insights on the guts of the universe that neither Newton nor Einstein could have possibly imagined. The nature of gravity has, I think, only a centuries' worth of mystery in it left.
[ June 07, 2003, 06:01 AM: Message edited by: Cartmaniac ]
Posted by MinutiaeMan (Member # 444) on :
Or to make the theory of relativity even more confusing, objects ALWAYS travel in a straight line... it just appears to be a curved line to us because of our point of view. We can't PERCEIVE the curvature of space-time.
Confused enough yet? Posted by Grokca (Member # 722) on :
Just to throw a wrench into this, Why then is the moon moving farther away from the earth all the time?
Posted by Cartmaniac (Member # 256) on :
Tidal friction. Because the side of the Earth that faces the moon is closer, it feels a stronger gravitational pull than the Earth's center. Similarly, the part of the Earth facing away from the moon feels less gravity. This distorts the planet's actual solid body a few centimeters, making it oblong. The parts that stick out are tidal, erh, bulges.
Now, mass produces a gravitational force, so those tidal bulges exert a tiny pull on the moon... but because the Earth rotates (much) faster than the moon orbits around it, they also "speed up" the moon by tugging it ahead slightly. Conversely, the moon slows the Earth's rotation - hence tidal movement. To cut a looong story short: the process takes kinetic energy from the Earth (through friction) and puts it into the moon, gradually stretching its orbit.
[ June 07, 2003, 11:42 AM: Message edited by: Cartmaniac ]
Posted by Wraith (Member # 779) on :
Thanks everyone, I figured it was something like that. Well, sort of. Posted by Jason Abbadon (Member # 882) on :
quote:Originally posted by Cartmaniac: [QB] Tidal friction. Because the side of the Earth that faces the moon is closer, it feels a stronger gravitational pull than the Earth's center. Similarly, the part of the Earth facing away from the moon feels less gravity. This distorts the planet's actual solid body a few centimeters, making it oblong. The parts that stick out are tidal, erh, bulges.
Ohhhh...Lunar gravitation is fun! To really fire your neurons, imagine poor Europa and Ganeymede being constatntly contracted and pulled by Jupiter's immense gravity until their internal tempature rises from tectonic friction. That's why there is the remote possiblity of life existing on icey Europa: internal tempatures may have led to a liquid ocean under all that ice. Posted by TSN (Member # 31) on :
"Poor" Europa and Ganymede? Don't let Io hear you say that...
Posted by Jason Abbadon (Member # 882) on :
How 'bout "lonely and isolated" Europa and Ganeymede?
"Barren and sterile"?
"remote and unknowable"
"Frozen and oppressed"?
I could go on and on, but you see the danger of personalizing a celestial body...unless it's Lucy Lu (drool).
Posted by Cartmaniac (Member # 256) on :
Whatever you do, don't personalize Uranus.
Posted by TSN (Member # 31) on :
My point is that the tidal forces that are tearing up Europa and Ganymede are far less than those at work on Io. Io is well-known for its non-stop volcanic activity over the whole surface due to the fact that Jupiter's bending it completely out of shape. It would be like talking to a guy who'd just had all his limbs amputated and saying "oh, look at that poor fellow over there w/ the paper cut".
Posted by Jason Abbadon (Member # 882) on :
If I saw that guy, I'd offer him a Band-Aid. It would be funny. You know it would. Admit it.
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