I don&#x27;t question that the effect is there.<p>I just wonder if it isn&#x27;t a side effect of some other (not understood) aspect of the universe rather than the result of the behaviour of some particle.<p>To illustrate, gravity per se doesn&#x27;t exist, it&#x27;s the outcome of the bending of space towards mass. So it&#x27;s effect is real but it&#x27;s not because some sort of gravitional particle is acting.