Context

Researchers have created a detailed map of the ‘hidden’ dark matter that makes up 85 per cent of the universe and mentioned that it agrees with Einstein’s theory of gravity.

What is dark matter?

• It is a hypothetical form of matter thought to account for approximately 85% of the matter in the universe.
• It forms the skeleton on which galaxies form, evolve, and merge.
• Dark matter is made up of particles that do not have a charge.
• So, these particles are “dark”, namely because they do not emit light, which is an electromagnetic phenomenon, and “matter” because they possess mass like normal matter and interact through gravity.

Evidence for dark matter: It comes from calculations showing that many galaxies would fly apart, that they would not have formed, or that they would not move as they do if they did not contain a large amount of unseen matter.

About the map:

• Published by:
• This research was presented at the Future Science with CMB x LSS, a conference being held from at the Yukawa Institute for Theoretical Physics, Kyoto University.
• Researchers from the United States, Canada and the United Kingdom used a ground-based telescope, Atacama Cosmology Telescope (ACT).
• The “baby picture of the universe” has been projected which consists of a cosmic microwave background (CMB) radiation or fossil radiation has left over after the Big Bang.

Key findings:

• It proved that the Gravitational field generated by these massive objects bends and distorts light that passes through them.
• Unlike normal matter that constitutes all stars and galaxies; dark matter does not absorb, reflect or emit light.
• Dark matter only seems to interact with gravity, making it challenging to detect.
• Being invisible, researchers observe how dark matter interacts with the gravity of massive objects such as galaxy clusters and lumps of dark matter.
• The clumps of dark matter magnify the appearance of objects that lie behind.
• The researchers look for this characteristic magnification in the CMB image to map the dark matter.
• The new findings agree with the standard model of cosmology based on Einstein's theory of gravity.

Einstein's theory of gravity:

• According to the theory, he proved that a mass can prod space plenty. It can warp it, bend it, push it, or pull it.
• Gravity was just a natural outcome of a mass's existence in space.
• According to relativity, anything that can happen inside of a box picking up speed — i.e., accelerating — also happens in the presence of gravity.
• For example, a horizontal laser inside an elevator that’s accelerating upward. As the light travels sideways, the elevator rises, causing the beam to strike a spot on the wall slightly lower than where it started.
• If the elevator accelerates quickly enough, the beam visibly bends toward the floor.
• Einstein showed the same thing happens to a beam inside a stationary elevator within a powerful gravitational field; the gravity bends the light.
• Similarly, he expected a beam of starlight should bend when passing through the sun’s gravity.

Theory of Einstein vs. Newton: Isaac Newton described gravity as a force, an invisible rubber band that pulls together objects with mass. Newton’s math did a good job at predicting how everything from projectiles to planets moved — but it kept gravity separate from acceleration. This link was established by Einstein in his theory. Einstein argued that gravity isn’t a force at all. He described it as a curvature of time and space caused by mass and energy.