Dark matter: An invisible glue that may not even exist

Subject : Science and Technology

Section: Space technology

Context:

The new Euclid space telescope, set for launch on July 1, will play a key role is the search for Dark matter. Our largest space-based telescope, the James Webb Space Telescope is also on the case.
JWST has released an image of the universe, in which there is an image of Stephan’s Quintet, a group of five galaxies, as they have never been seen before.

About Dark Matter:

Scientists cannot define dark matter with any certainty and it has never been detected, only speculated. But scientists estimate that up to 85% of the matter in the universe could be made of what’s called dark matter.

An accidental discovery of Dark Matter:

In the 19th century, Lord Kelvin, a Scottish-Irish physicist, wanted to estimate the mass of our galaxy, the Milkyway, using data on how fast stars moved around the galaxy’s core.
But Kelvin found discrepancies or anomalies in the data, things which could not be explained and were attributed to “dark bodies” that we cannot see.
The galaxy seems to be rotating much faster than it should, based on estimates.
The theory is that there is an “invisible matter” responsible for the speed at which our galaxy rotates. And that may be true of other galaxies as well.
Stars have been observed to travel at higher-than-estimated speeds, especially at the edges of galaxies.
Astronomers have speculated that stars should have ripped and flown off at the speed with which they are travelling, but they do not.
The only explanation is that there must be some invisible matter (or dark matter) holding the stone in range.

We can’t see dark matter but we may see its effects

The reason we are unable to see or detect this invisible matter is that it does not interact with electromagnetic forces — things like visible light, X-ray or radio waves.
We can, however, observe some of the effects of dark matter through its gravitational force.
But we still want to detect dark matter in its own right. CERN’s Large Hadron Collider can help in detecting dark matter.
A decade ago, experiments at the LHC proved the Standard Model of particle physics by detecting the Higgs boson particle — a particle which itself had long proved to be elusive.
- The Standard Model is the idea that everything in the universe is made of a few fundamental particles and that those are governed by four fundamental forces — the strong nuclear force, the weak nuclear force, the electromagnetic force, and the gravitational force.
The dark matter can’t interact with light or electromagnetism. It can’t interact with the strong force, and it may interact through the weak force that causes radioactivity.

Measuring dark matter by what’s missing:

The Large Hadron Collider smashes particles together to create collisions. The collisions produce debris that gets caught by particle detectors.
We smash the fundamental particles up and they split and spray against the LHC detectors, and if we piece them back together, we should be able to account for all the bits that made those original particles. And if we found something missing (especially mass or energy), that could be an indication of the presence of dark matter.
The Higgs boson interacts with all the other elements that have mass. And so the dark matter must [also] have mass in order to fulfil the effect that we see in the galaxies.

New theories about dark matter:

Some scientists suggest we should think outside of the Standard Model.
One of those scientists is the physicist Mordehai Milgrom.
Milgrom has developed an alternative theory of gravity, one that suggests that gravitational force operates differently at different distances from the core of a galaxy.
While Newton’s theory of gravity explains most large-scale movements in the cosmos, Milgrom’s Modified Newtonian Dynamics suggests that a force acts differently when it is weak, such as at the edge of a galaxy.
Advocates of the theory say it predicts the rotation of galaxies and the speed of the stars better than Newton’s theory.