# Do all four fundamental forces have effects on spacetime?

1. Since gravity, a fundamental force, takes effect through ripples in spacetime, do the other fundamental forces do the same?

2. For example, since gravitational waves are ripples in space time, are electromagnetic waves also ripples?

3. Or is it just gravity that acts that way?

4. If so, why does gravity have that special property?

5. Side question: Since the force carriers for strong and weak forces don't exist outside their ranges, does that mean their (tiny) gravitational ripples "vanish" outside their ranges?

6. Do the strong and weak forces have their own "waves"?

• Related: physics.stackexchange.com/q/155671/2451 and links therein. Commented Aug 6, 2016 at 18:30
• Oh, I didn't see these. They're definitely useful. Thanks! Commented Aug 7, 2016 at 10:55

Electromagnetic waves (light) are ripples in the electromagnetic field, instead of the spacetime metric.

As far as other forces making waves: Each of the fundamental forces has a particle that carries that force. For electromagnetism, it's the photon, which is the minimum unit of energy in an electromagnetic wave. Similarly, a graviton is the minimum unit of energy in a gravitational wave. These are the force carrier particles for EM and gravity. The W and Z bosons carry the weak nuclear force, but they are too heavy and unstable to last long enough to identify as a wave. Nuclear forces are a little weirder than gravity and EM. I would say they do not have ripples in the same way, but you can read more here: nuclear force waves.

Any mass will, in theory, produce gravitational effects. The problem we have is that they are both 1. far too small to be measured and 2. far too weak to be noticed against the other forces. I am leaving the photon out of this answer as it is massless.

So if you took the relative strength of gravity as 1, then the other forces are something like 10$^{25}$ to 10$^{38}$ times bigger.

But if a mass does produce a gravitional effect, it will be felt outside it's "ordinary/normal" range, as gravitons (that carry gravity), are infinite in their range. But I would stress, we will almost certainly never detect an electron (or the weak force carrying W and Z bosons) by their gravitional effects.

• Smaller? Don't you mean 10^25 or 10^38 BIGGER? Also, I'm asking on a theoretical basis. Since Z bosons are virtual and don't exist outside their range- would any gravitational waves coming from them exist outside their range? Commented Aug 6, 2016 at 15:35
• Hmm- actually I think my understanding of "virtual particles" may be wrong here. I was under the impression that these particles literally don't exist outside of the effective range of their force (hence the term, "virtual particle")? Is that wrong? Commented Aug 6, 2016 at 15:41
• Bigger, sorry. The mass of a Z boson is greater than an iron atom, for its brief lifetime, it should produce gravitional effects that are, in theory, outside their range.
– user108787
Commented Aug 6, 2016 at 15:43
• No, I wondered about that too. For the time they are doing their job, the Higgs field does give them mass. I treat them as real in that case, but I do see your point.
– user108787
Commented Aug 6, 2016 at 15:46

There are some misconceptions in the question, easy to have, and a good question to clarify the concept and issues. Note below that in the end analysis we really don't know yet why gravity is so different than the other forces, but have some ideas.

Gravitational waves are ripples in spacetime, but any mass-energy varying with some quadrupole moment or higher (I.e. not too symmetrically) will cause it. Gravity does not cause gravitational waves, it is any mass-energy varying in certain ways that does. Still, any mass-energy will cause a gravitational field.

Gravity or a gravitational field, whether radiative, I.e., a wave (normally labeled as some perturbation that propagates as 1/r in the far field) or not, is caused by mass-energy, or more specifically the stress energy tensor that includes all forms of energy and mass, momentum or pressure, and stress. Any particle field that has energy (or any of those) will cause a gravitational field.

That includes the weak and strong forces, or better labeled, quantum fields. Also of course any electromagnetic field. The weak forces arise from a field, all part of the electroweak field for which Weinberg and others got the Nobel. A simpler version of the weak field wave equation is the Proca equation, see https://en.m.wikipedia.org/wiki/Proca_action.

The difference between the strong and weak forces and for instance the electromagnetic forces which are long range, is that the latter is mediated by the massless photon, but both strong and weak forces are mediated by massive gluons and the W and Z bosons, respectively. The range of the forces, or the fields, are basically determined by the bosons masses, and semi-proportional to 1/m. There is more that goes into it, and the specific dynamics and symmetries of those fields are best described through the particle standard model, for now (yes, I am using forces and fields sort of interchangeably, the quantum field are the real things, the forces are an easy way of talking simplistically and semi-classically).

The above covers your questions 1, 2 and 3, and 5 and 6.

For 4- why does gravity act that way? It is not the way it acts, it is what it is. Gravity is the effect of spacetime curvature, and we sense it as gravitational forces and waves. It is created, due to the equivalence principle, by any mass-energy. Einstein Field Equations were arrived at as the simplest way that you'd be able to have the gravitation, in a theory that is valid in any reference frame, and reduces to Newton's equations in the weak field limit, all without any quantum effects accounted for. All its predictions measured have been found to be as predicted. It includes effects never envisioned like the expansion of the universe and Black holes, as well as more conventional ones like a small deviation of orbits from pure Newtonian (the advance of the perihelion of Mercury), light lensing in a gravitational field, and others. The other forces are different things, quantum fields that interact and whose quanta are the bosons that carry the force, and the fermions that interact with them. They do not arise, as we see it now, by altering space time (but see String theory below).

For 4a: why is gravity unique that way? nobody knows yet, a quantum theory of gravity has not been formulated that has been accepted, although there are plenty attempts and research into it including string theory and loop quantum gravity. String theory says that all forces are string effects, and gravity is uniquely the spin 2 case. All the other forces are spin 1, and then the apparently spin 0 Higgs particle which leads to the mass of the elementary particles. Gravity seems to be unique because of the equivalence principle (with effect, for this, that any energy or mass gravitates), and that it is spin 2, which means attractive for positive energy and pressure). And I'm sure more that we just don't know