# Question about gravity. **URL:** \ **Category:** Factual Questions\ **Created:** [September 28, 2003, 5:10pm UTC](https://boards.straightdope.com/t/question-about-gravity/204314 "2003-09-28T17:10:13Z")\ **Posts on this page:** 19\ **Page:** 1
**Author:** ![Kinthalis](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kinthalis/32/16084_2.png) [@Kinthalis](https://boards.straightdope.com/u/Kinthalis)\ **Post date:** [September 28, 2003, 5:10pm UTC](https://boards.straightdope.com/t/question-about-gravity/204314/1 "2003-09-28T17:10:13Z")
Last I heard, scientists are still looking for gravitons, and I have even heard dopers on thses board refer to gravity ‘waves’ and ‘particles’. This, to my admitedly limited understanding on the subject, seems to disagree with Special relativity. Special relativity tells us that the orbital paths followed by planets, our moon, man-made satellites, in short: gravity, is nothing more than the motion of bodies through warped space-time. That is, massive objects warp space-time around them causing the phenomena we term ‘gravity’. If that is true, then what is the point of looking for gravitons, gravity waves or particles? It would appear to me that special relativity tells us that there are none. Objects are simply following the trajectory of warped space-time. And yet I must be wrong since scientist still refer to these things. Could someone explain this better to me? 😉 ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [September 28, 2003, 5:18pm UTC](https://boards.straightdope.com/t/question-about-gravity/204314/2 "2003-09-28T17:18:58Z")
Yes, but we don’t know exactly _why_ or _how_ massive bodies warp spacetime. We believe that gravitons may play a role in this process. ---
**Author:** ![Kinthalis](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kinthalis/32/16084_2.png) [@Kinthalis](https://boards.straightdope.com/u/Kinthalis)\ **Post date:** [September 28, 2003, 5:23pm UTC](https://boards.straightdope.com/t/question-about-gravity/204314/3 "2003-09-28T17:23:30Z")
Ahhh, ok. Silly me, yes I just took the fact that massive bodies warp space-time as a given without asking, how? How unscientific of me! 😉 So in a related question, since we don’t know HOW this occurs, what makes us think that particles of gravity have anythign to do with it? And what makes us think there even ARE particles at work? I’m guessing that’s a complicated question, so a link to a reference source would be much apreciated 😉 ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [September 28, 2003, 5:29pm UTC](https://boards.straightdope.com/t/question-about-gravity/204314/4 "2003-09-28T17:29:34Z")
Well, the three other forces we know about all have an associated particle to carry them. Electromagnetism has the photon, the nuclear strong force has gluons and the weak force has W and Z bosons. So, it’s natural to assmume that gravity also has a particle associated with it. Plus superstring theory contains within it one entity whose properties exactly match the predicted characteristics of the gravition. In other words, superstring theory not only explains gravity, it requires it. ---
**Author:** ![MC\_Master\_of\_Ceremonies](https://avatars.discourse-cdn.com/v4/letter/m/bb73d2/32.png) [@MC\_Master\_of\_Ceremonies](https://boards.straightdope.com/u/MC_Master_of_Ceremonies)\ **Post date:** [September 28, 2003, 5:34pm UTC](https://boards.straightdope.com/t/question-about-gravity/204314/5 "2003-09-28T17:34:41Z")
Special rleativity doesn’t deal directly with gravity, though it can be fitted into the framnework of SR. It is general relativity that introduces the concept of gtravity as curved space-time. Gravitons are very firmly predicted by theory (though no complete theory of quantized space-time exists yet), but so far due to the nature of gravity none have been detected. Infact several of the properties that i hould have are also well predicted such as that it shoild be massless and have a spin of 2. ---
**Author:** ![RM\_Mentock](https://avatars.discourse-cdn.com/v4/letter/r/e274bd/32.png) [@RM\_Mentock](https://boards.straightdope.com/u/RM_Mentock)\ **Post date:** [September 28, 2003, 6:03pm UTC](https://boards.straightdope.com/t/question-about-gravity/204314/6 "2003-09-28T18:03:18Z")
> [@](#): > > \*Originally posted by Kinthalis \* > **Special relativity tells us that the orbital paths followed by planets, our moon, man-made satellites, in short: gravity, is nothing more than the motion of bodies through warped space-time.** It’s general relativity, not special relativity, that deals with gravity. Could the warping of space be “equivalent” somehow to a gravity particle? Yes. But we’re not sure how. 🙂 ---
**Author:** ![Kinthalis](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kinthalis/32/16084_2.png) [@Kinthalis](https://boards.straightdope.com/u/Kinthalis)\ **Post date:** [September 28, 2003, 6:54pm UTC](https://boards.straightdope.com/t/question-about-gravity/204314/7 "2003-09-28T18:54:37Z")
Hmm, ok, so GENERAL relativity deals with gravity. And special relativity deals with \_\_\_\_\_\_\_\_\_. (Fill in the blank please 😉 ). ---
**Author:** ![RM\_Mentock](https://avatars.discourse-cdn.com/v4/letter/r/e274bd/32.png) [@RM\_Mentock](https://boards.straightdope.com/u/RM_Mentock)\ **Post date:** [September 28, 2003, 7:00pm UTC](https://boards.straightdope.com/t/question-about-gravity/204314/8 "2003-09-28T19:00:18Z")
time and space and light and electromagentism? They’re not mutually exclusive though. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [September 28, 2003, 7:01pm UTC](https://boards.straightdope.com/t/question-about-gravity/204314/9 "2003-09-28T19:01:38Z")
Special relativity deals with time, motion and the speed of light. ---
**Author:** ![Skeptico](https://avatars.discourse-cdn.com/v4/letter/s/e19b73/32.png) [@Skeptico](https://boards.straightdope.com/u/Skeptico)\ **Post date:** [September 28, 2003, 7:02pm UTC](https://boards.straightdope.com/t/question-about-gravity/204314/10 "2003-09-28T19:02:14Z")
**Kinthalis** , General Relativity deals with effects of acceleration and velocity, whereas Special Relativity deals with effects of velocity only. One is usually more interested in the acceleration aspects of gravity, i.e. force of gravity. ---
**Author:** ![RM\_Mentock](https://avatars.discourse-cdn.com/v4/letter/r/e274bd/32.png) [@RM\_Mentock](https://boards.straightdope.com/u/RM_Mentock)\ **Post date:** [September 28, 2003, 7:11pm UTC](https://boards.straightdope.com/t/question-about-gravity/204314/11 "2003-09-28T19:11:31Z")
> [@](#): > > \*Originally posted by Skeptico \* > **General Relativity deals with effects of acceleration and velocity, whereas Special Relativity deals with effects of velocity only.** I would disagree with this. Even Einstein’s first paper on special relativity dealt with the effects of acceleration. General relativity makes gravity and acceleration equivalent, though, and says any frames of reference are equivalent, even rotating ones. ---
**Author:** ![John\_Kentzel-Griffin](https://avatars.discourse-cdn.com/v4/letter/j/ccd318/32.png) [@John\_Kentzel-Griffin](https://boards.straightdope.com/u/John_Kentzel-Griffin)\ **Post date:** [September 28, 2003, 9:18pm UTC](https://boards.straightdope.com/t/question-about-gravity/204314/12 "2003-09-28T21:18:03Z")
In Special Relativity, your coordinate system must be inertial and the axes must be orthorgonal. This is a special case of General Relativity that allows general coordinate systems with (possibly) curved axes and not-necessarily-inertial frames. In SR, objects can accelerate, but not your coordinate systems. In SR, the speed of light is constant and has the same value in all inertial reference frames. In GR, the speed of light is not constant. In both, nothing can travel faster than light travels. ---
**Author:** ![MC\_Master\_of\_Ceremonies](https://avatars.discourse-cdn.com/v4/letter/m/bb73d2/32.png) [@MC\_Master\_of\_Ceremonies](https://boards.straightdope.com/u/MC_Master_of_Ceremonies)\ **Post date:** [September 28, 2003, 9:31pm UTC](https://boards.straightdope.com/t/question-about-gravity/204314/13 "2003-09-28T21:31:39Z")
> [@](#): > > \*Originally posted by Skeptico \* > \*\ ***Kinthalis** , > > General Relativity deals with effects of acceleration and velocity, whereas Special Relativity deals with effects of velocity only. > > One is usually more interested in the acceleration aspects of gravity, i.e. force of gravity. \*\* That’s a common misconception, Special Relativity deals with acceleration quite adequately and it can also deal with Newtonian gravity. ---
**Author:** ![RM\_Mentock](https://avatars.discourse-cdn.com/v4/letter/r/e274bd/32.png) [@RM\_Mentock](https://boards.straightdope.com/u/RM_Mentock)\ **Post date:** [September 28, 2003, 9:34pm UTC](https://boards.straightdope.com/t/question-about-gravity/204314/14 "2003-09-28T21:34:17Z")
> [@](#): > > \*Originally posted by MC Master of Ceremonies \* > \*\*it can also deal with Newtonian gravity. \*\* In what sense do you mean that? ---
**Author:** ![MC\_Master\_of\_Ceremonies](https://avatars.discourse-cdn.com/v4/letter/m/bb73d2/32.png) [@MC\_Master\_of\_Ceremonies](https://boards.straightdope.com/u/MC_Master_of_Ceremonies)\ **Post date:** [September 28, 2003, 9:39pm UTC](https://boards.straightdope.com/t/question-about-gravity/204314/15 "2003-09-28T21:39:31Z")
In the sense that you can fit gravity into the model if required. ---
**Author:** ![RM\_Mentock](https://avatars.discourse-cdn.com/v4/letter/r/e274bd/32.png) [@RM\_Mentock](https://boards.straightdope.com/u/RM_Mentock)\ **Post date:** [September 28, 2003, 9:45pm UTC](https://boards.straightdope.com/t/question-about-gravity/204314/16 "2003-09-28T21:45:16Z")
So it can also deal with economics? 🙂 ---
**Author:** ![MC\_Master\_of\_Ceremonies](https://avatars.discourse-cdn.com/v4/letter/m/bb73d2/32.png) [@MC\_Master\_of\_Ceremonies](https://boards.straightdope.com/u/MC_Master_of_Ceremonies)\ **Post date:** [September 28, 2003, 9:48pm UTC](https://boards.straightdope.com/t/question-about-gravity/204314/17 "2003-09-28T21:48:14Z")
Macro-, but not micro- 🙂 No what I mean is that there’s not fundamental conflict like there is with QM and GR between SR and pre-GR gravity. ---
**Author:** ![Scott\_Dickerson](https://avatars.discourse-cdn.com/v4/letter/s/f04885/32.png) [@Scott\_Dickerson](https://boards.straightdope.com/u/Scott_Dickerson)\ **Post date:** [September 28, 2003, 10:15pm UTC](https://boards.straightdope.com/t/question-about-gravity/204314/18 "2003-09-28T22:15:24Z")
I thought that “gravitons” are VIRTUAL particles predicted by the (Heisenberg?) principle that all field (ie, wave) phenomena can and MUST be equally describable by particle emission-and-absorption models. No? ---
**Author:** ![MC\_Master\_of\_Ceremonies](https://avatars.discourse-cdn.com/v4/letter/m/bb73d2/32.png) [@MC\_Master\_of\_Ceremonies](https://boards.straightdope.com/u/MC_Master_of_Ceremonies)\ **Post date:** [September 28, 2003, 10:37pm UTC](https://boards.straightdope.com/t/question-about-gravity/204314/19 "2003-09-28T22:37:44Z")
Gravitons are usually virtual due to the fact that most gravitaional fields are static. Hesienburg was the uncertainty principle, it’s just in QFT’s fields become quantized.