lawrocket 3 #1 October 17, 2003 This is not a question of accelleration. This is a question of the speed that a gravitational force travels. I remember reading a few years ago that gravity was an instantaneous force. If it is an instantaneous force, then it must be faster than the speed of light. in other words, if a barrier to gravity between the earth and the sun were put up, then taken down, how long would it take for the sun's gravity to affect the earth? Instaneous??? Doesn't this conflict with Einstein, who said that the speed of ligth through a vacuum was the fastest in the universe? Wouldn't gravity win that race? My wife is hotter than your wife. Quote Share this post Link to post Share on other sites
bmcd308 0 #2 October 17, 2003 You're going to have to wait for Kallend. Back when I was a physics major, we still thought the strong force and the weak force were different fundamental forces. ---------------------------------- www.jumpelvis.com Quote Share this post Link to post Share on other sites
lawrocket 3 #3 October 17, 2003 Hey, I don't know shit about this. That's why I'm asking. My wife is hotter than your wife. Quote Share this post Link to post Share on other sites
Beerlight 0 #4 October 17, 2003 Speed of gravity is very close to the speed of light. Quote Share this post Link to post Share on other sites
kiltboy 0 #5 October 17, 2003 I thought gravity was a force that was always acting upon an object but that the effect of the gravitational force was dependant upon other oppositte forces that would balance it out. Light as a photon is a discrete object and is treated differently. Or am I off target again? David Quote Share this post Link to post Share on other sites
Push 0 #6 October 17, 2003 Yes, changes in gravity do propagate with a finite speed. If you're interested, look up gravity waves. There's some incredible stuff. If you're curious, ask me and I will write up a brief explanation on how you can explain Newton's 3rd Law (every action has an equal opposite reaction) in terms of gravity waves. -- Toggle Whippin' Yahoo Skydiving is easy. All you have to do is relax while plummetting at 120 mph from 10,000' with nothing but some nylon and webbing to save you. Quote Share this post Link to post Share on other sites
Push 0 #7 October 17, 2003 QuoteI thought gravity was a force that was always acting upon an object but that the effect of the gravitational force was dependant upon other oppositte forces that would balance it out. In the traditional Newtonian sense, gravity is simply another force that can be computed with a certain formula. That is all it is. Not a very good explanation, huh? Anyway, the effect of any force, be it gravity, normal, acting, buoyancy, lift, drag, whatever, is dependent on the other forces. Light as a photon is complicated. The question is, does it have mass? The answer is, kind of. It carries momentum. -- Toggle Whippin' Yahoo Skydiving is easy. All you have to do is relax while plummetting at 120 mph from 10,000' with nothing but some nylon and webbing to save you. Quote Share this post Link to post Share on other sites
kiltboy 0 #8 October 17, 2003 That's what I was thinking it was the speed idea that threw me for a loop. I believed that the forces would be constantly acting upon an object with the net effect being what was observed i.e. just because you experience lift does not mean that gravity isn't still acting on an object but that the force of lift is greater with lift being the net result. As for photons and gold leaf experiments yes it behaves as a particle and a wave form and at that point I pretty much accepted behaviour in my world to be what it would be. Physics is great when you neglect friction etc. but I was more interested in what happened big scale in my world than microscale in theory. David Quote Share this post Link to post Share on other sites
JeffD 0 #9 October 17, 2003 Better yet, what the hell is gravity?!? is it magnetic? (think the High magnetic field lab at UF where they can levitate a frog) or is it pure energy confined within material? but isnt that electronegativity also? Quote Share this post Link to post Share on other sites
NoShitThereIWas 0 #10 October 17, 2003 I could be way off here if you are talking Physics over my head ... This is what I can contribute to your question: 1) Gravity is an attractive force and it has to do with the masses and distances between two objects according to Newton's Universal Law of Gravitation. 2) the greater the distance between the objects the less force. The more massive the objects the greater the force between them. This is seen through the relationship of formula: F=G(M1)(M2)/r^2. Basically, the graviational force equals a constant times the masses of the objects divided by their distance (r) squared. 3) As I understand it for time being, gravity is always attractive and you cannot reverse it. There is no "anti-gravity" so your theory of placing a barrier in between Earth and the sun to disengage its gravitational force is not possible. 4) Light or electricity on the other hand can be attractive or repulsive and when you are talking about speeds of things, you are talking about the difference of something that weighs something like 9.11 times 10^-31 kg versus something like Earth which has a mass of 5.98 x 10^24 kg. Gravity is a force that mainly deals with larger masses and electricity deals with things that have subatomic masses. This allows them them to move at speeds of 3.00 x 10^8 m/s. I hope that helps. Without getting into things like Kinetic and Potential Energy.Roy Bacon: "Elvises, light your fires." Sting: "Be yourself no matter what they say." Quote Share this post Link to post Share on other sites
mjosparky 4 #11 October 17, 2003 QuoteHey, I don't know shit about this. That's why I'm asking. You have way to much free time on your hands.My idea of a fair fight is clubbing baby seals Quote Share this post Link to post Share on other sites
lawrocket 3 #12 October 17, 2003 Actually, what I'm asking is this: Assuming there is a race to the earth from the sun between light and gravity. Which would reach the earth first? My wife is hotter than your wife. Quote Share this post Link to post Share on other sites
kiltboy 0 #13 October 17, 2003 Well isn't gravity from the sun constantly acting on the earth? Wouldn't that make it already there unlike the light which would be generated from the release of energy by hydrogen fusion? David Quote Share this post Link to post Share on other sites
deronde 0 #14 October 17, 2003 This is why I like skydiving, one moment you're talking about the gorgeous new student who just did her/his (...) first AFF at your DZ, the next moment you're discussing the finer points of gravitational forces and their influence on the space-time continium... Love, peace & blue skies to all of ya! Quote Share this post Link to post Share on other sites
Samurai136 0 #15 October 17, 2003 The actual theory of gravity is still evolving. Although you can calculate the force of gravity as a relationship between the distance and mass of objects, how gravity does it's work is still in its theoretic stages. By comparisson, in Electricity/Magnetism the interaction is between particles which can be measured by their positive or negative charge in Coulomb's. The gravitiational equation taught in basic Highschool/ College physics classes is an adaptation of Coulomb's law. My understanding is that if the Sun were to spontaneously become non-existant it would take 8minutes for the last light to reach us but the gravitational effects would be instant. Gravity is the weakest of all the forces and as such earth (and all other objects in the solar system) would continue on a path tangent to their current orbital path. Ken"Buttons aren't toys." - Trillian Ken Quote Share this post Link to post Share on other sites
turtlespeed 226 #16 October 17, 2003 what if C-A-T actually spelled Dog? Sorry, I just couldn't resist.I'm not usually into the whole 3-way thing, but you got me a little excited with that. - Skymama BTR #1 / OTB^5 Official #2 / Hellfish #408 / VSCR #108/Tortuga/Orfun Quote Share this post Link to post Share on other sites
dterrick 0 #17 October 17, 2003 Quote (think the High magnetic field lab at UF where they can levitate a frog) Don't frogs auto-levitate? I thought it was called 'hopping' Seriously, are you serious? Have they been able to magnetically levitate frogs like they do with Linear Induction Motors? Next step... transporters (a la Star Truck)? More info, requests the 'physic(s)ally' challenged ... Dave Life is very short and there's no time for fussing and fighting my friend (Lennon/McCartney) Quote Share this post Link to post Share on other sites
billvon 3,085 #18 October 17, 2003 >This is a question of the speed that a gravitational force travels. For a while it was thought to be effectively instantaneous; the contradictions to the theory of relativity were explained away by saying that gravity did not "propagate" per se but rather warped space-time in the vicinity of a mass; there is no relativistic limit on such warpage. In 1999, a physicist (Sergei Kopeikin) proposed a way to explain how the gravitational fields of moving bodies distort radio waves and light. Once you knew this, you could calculate the speed of gravity by measuring these effects on astronomical observations of light from distant objects. An event where this effect was obvious occurred in 2002; Jupiter passed near the apparent position of a quasar. From observations of how Jupiter's gravity distorted the apparent position of the quasar, Kopeikin deduced that gravity propagates at the speed of light. (At least within 20%.) Gravity is still the most poorly understood force - how it is mediated, how it propagates etc. >As I understand it for time being, gravity is always attractive and you > cannot reverse it. There is no "anti-gravity" . . . At least with normal matter. It has been proposed that a mass of negative matter (not antimatter, which is normal matter with electron and proton charges reversed) will create a negative gravitic field. And of course if you put an ultradense mass just on the other side of the earth, it would effectively cancel out the sun's gravity. BTW negative matter has some very cool uses, like keeping the throat of a wormhole open or making an inertialess drive that will accelerate a spacecraft forever with no energy input. It would also explain some of the missing-mass problem, but it is most likely imaginary. >Gravity is a force that mainly deals with larger masses and electricity > deals with things that have subatomic masses. Well, the strong and weak forces dominate in subatomic realms. Electromagnetism is, for the most part, a macroscopic effect. Quote Share this post Link to post Share on other sites
genoyamamoto 0 #19 October 17, 2003 Hey lawrocket, the answer to your question is "nobody knows". Einstein assumed gravity propagates at the speed of light but it has yet to be proven. The best way to prove this is by measuring gravitational waves. Kopeikin and Fomalont attempted to measure the speed of gravity using another method as mentioned by someone here but there have been serious issues raised with their technique (mistakes and lack of sensitivity of their method). There's an article at: http://www.lbl.gov/Science-Articles/Archive/Phys-speed-of-gravity.html That should give you an idea of where we are in answering your question. Heck, if you are really REALLY interested you should e-mail Stuart Samuel! Just look for him here: http://www.lbl.gov/ds/ -G Gotta go... plaything needs to spank me Feel the hate... Photos here Quote Share this post Link to post Share on other sites
lawrocket 3 #20 October 17, 2003 Mr. Von, you have nce again ejumacaded me. This is fascinating, and now I can report what I heard to my buddy, with whom I had this discussion months ago. Mind you, none of us knew the answer, nor what we were taling about, really. Dang, I sound like a trekkie! My wife is hotter than your wife. Quote Share this post Link to post Share on other sites
meatmissile 0 #21 October 17, 2003 Stick to law.... ~j/k -- ZZZzzzz.... Quote Share this post Link to post Share on other sites
kallend 2,113 #22 October 18, 2003 According to general relativity, a very well tested theory, gravity waves travel at the speed of light in a vacuum (c).... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites
SpeedRacer 1 #23 October 18, 2003 There's a gravity shortage, you know. Speed Racer -------------------------------------------------- Quote Share this post Link to post Share on other sites
NoShitThereIWas 0 #24 October 18, 2003 Wow, you are talking way over my head dude. Fascinating stuff if you want to keep talking. What little I do know about the topic was a treacherous learning process (my definition of physics) but it is way cool when you do understand something... Roy Bacon: "Elvises, light your fires." Sting: "Be yourself no matter what they say." Quote Share this post Link to post Share on other sites
NoShitThereIWas 0 #25 October 18, 2003 QuoteAccording to general relativity, a very well tested theory, gravity waves travel at the speed of light in a vacuum (c). What??? John, can you explain some of this general relativity stuff? Gravity is in waves??? They never told us that. I guess that's all we get out of Trig based Physics.Roy Bacon: "Elvises, light your fires." Sting: "Be yourself no matter what they say." Quote Share this post Link to post Share on other sites
