Is dark matter not a substance, but an error in the formula?
A new study suggests a radical idea: perhaps dark matter as a separate "substance" doesn't exist at all, and the effect we've attributed for decades to invisible particles could be explained by gravity behaving differently at very large distances. This is reported by Space.com, citing a paper by physicist Naman Kumar of the Indian Institute of Technology, published on Phys.org.
Dark matter has become a headache for cosmologists because, according to the standard picture, it should be approximately five times more abundant than ordinary matter, yet it remains invisible: it doesn't interact with light or electromagnetic radiation. All we have are indirect signs through gravity. The most famous argument is that galaxies rotate so rapidly that the gravity of visible stars and gas alone wouldn't be enough to keep them from flying apart. A second important piece of evidence involves gravitational lensing, where the light from distant objects is bent by the mass of galaxies more than can be explained by visible matter alone. This is where the hypothesis of giant dark matter halos around galaxies comes from.
Rather than adding new particles to physics, Kumar proposes reconsidering gravity itself at the scale of galaxies. He approaches it in terms of quantum field theory and uses the so-called "infrared" model, where the effective interaction strength can depend on scale. In the conventional Newtonian picture, gravity obeys an inverse-square law: the farther from the source, the weaker the attraction, proportional to 1/r². In his model, a deviation appears at large distances, yielding a more "long-range" behavior on the order of 1/r². According to the author, this may be sufficient to obtain the observed rotation curves of galaxies without the dominant contribution of cold dark matter.
The dark matter problem, however, isn't tied solely to galaxy rotation. In standard cosmology, it helps explain how structure grew in the Universe and why we see the particular distribution of galaxies we see, and it also helps reconcile observations of the cosmic microwave background. Kumar argues that in his "infrared" approach, corrections to gravity increase slowly and become significant only in the late stages of evolution and on large scales, so the early Universe can remain consistent with precise measurements.
Next, the theory must navigate the most painful stage: comparison with data on gravitational lensing and the dynamics of galaxy clusters, where the contribution of dark matter is generally considered key. Kumar himself emphasizes that his scheme does not yet completely replace the standard model of cosmology, particularly in the details of structure formation and lensing, but it does suggest a path in which "dark matter effects" could be a manifestation of the hidden complexity of gravity itself. The work was published in the journal Physics Letters B.
A new study suggests a radical idea: perhaps dark matter as a separate "substance" doesn't exist at all, and the effect we've attributed for decades to invisible particles could be explained by gravity behaving differently at very large distances. This is reported by Space.com, citing a paper by physicist Naman Kumar of the Indian Institute of Technology, published on Phys.org.
Dark matter has become a headache for cosmologists because, according to the standard picture, it should be approximately five times more abundant than ordinary matter, yet it remains invisible: it doesn't interact with light or electromagnetic radiation. All we have are indirect signs through gravity. The most famous argument is that galaxies rotate so rapidly that the gravity of visible stars and gas alone wouldn't be enough to keep them from flying apart. A second important piece of evidence involves gravitational lensing, where the light from distant objects is bent by the mass of galaxies more than can be explained by visible matter alone. This is where the hypothesis of giant dark matter halos around galaxies comes from.
Rather than adding new particles to physics, Kumar proposes reconsidering gravity itself at the scale of galaxies. He approaches it in terms of quantum field theory and uses the so-called "infrared" model, where the effective interaction strength can depend on scale. In the conventional Newtonian picture, gravity obeys an inverse-square law: the farther from the source, the weaker the attraction, proportional to 1/r². In his model, a deviation appears at large distances, yielding a more "long-range" behavior on the order of 1/r². According to the author, this may be sufficient to obtain the observed rotation curves of galaxies without the dominant contribution of cold dark matter.
The dark matter problem, however, isn't tied solely to galaxy rotation. In standard cosmology, it helps explain how structure grew in the Universe and why we see the particular distribution of galaxies we see, and it also helps reconcile observations of the cosmic microwave background. Kumar argues that in his "infrared" approach, corrections to gravity increase slowly and become significant only in the late stages of evolution and on large scales, so the early Universe can remain consistent with precise measurements.
Next, the theory must navigate the most painful stage: comparison with data on gravitational lensing and the dynamics of galaxy clusters, where the contribution of dark matter is generally considered key. Kumar himself emphasizes that his scheme does not yet completely replace the standard model of cosmology, particularly in the details of structure formation and lensing, but it does suggest a path in which "dark matter effects" could be a manifestation of the hidden complexity of gravity itself. The work was published in the journal Physics Letters B.
