(ORDO NEWS) — The deeper the space, the less ordered our mathematical models that describe the structure of the universe become.
A new study of the dwarf galaxy AGC 114905 has revived a controversial theory (or rather a hypothesis) about the nature of gravity and has given us more questions than answers about exactly what force makes our galaxies move.
Gravity is usually associated with dark matter, although there are no unambiguous opinions on this matter. While most cosmologists agree that there is something that makes spiral galaxies spin faster than they should, even this hypothetical substance does not provide all the answers we need.
So it would be nice to consider alternative options. And physicists just have one very curious hypothesis.
It is called modified Newtonian dynamics (MOND) or the Milgrom model of dynamics. This hypothesis, first published in 1983 by physicist Mordecai Milgrom, suggests that we don’t need dark matter to fill gravitational gaps in the universe if we calculate the gravitational forces experienced by stars in the outer galactic regions in a different way than Newton’s laws do.
How galaxies are studied
To test this idea, we need to look at the speed of galaxies – especially strange ones like ultra-diffuse galaxies. These very weak “ugly ducklings” of the galactic world have a habit of behaving differently from how a “normal” galaxy should behave.
For example, some superdiffused galaxies appear to be almost entirely dark matter, while others are almost entirely devoid of it.
This is where AGC 114905 comes on the scene. About 250 million light-years away, this ultra-diffuse dwarf galaxy was recently detailed in a paper published in 2021 on its rotation speed.
The scientists found that the galaxy’s rotation was extremely slow so slow that not only did they not need dark matter to confirm the models, but the galaxy’s rotation curve also cast serious doubt on the structure of MOND. This is not consistent with either hypothesis.
A new article “debunks” the discovery of 2021: the researchers suggest that the problem is not in MOND, but in the tilt of the galaxy itself.
When we look at galaxies far in the depths of space, it is sometimes difficult to understand from what angle we see them. The original team stated that AGC 114905 appears elliptical, suggesting that we are looking at the galaxy from an angle.
However, the new model suggests that the galaxy itself may appear elliptical, even if it is facing us directly. Changing the angle of the galaxy with respect to us will also change the speed of the galaxy’s rotation, causing all the MOND math to add up.
Who is right and which theory should be believed? Well, while scientists do not have a clear answer to this question.
In the future, they hope to either confirm the presence of dark matter in space – and then alternative theories will simply not be needed – or refute it and create a more perfect model of the structure of the Universe.
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