Dark Matter and Dark Energy — Reading Comprehension

Dark matter and dark energy are two of the most mysterious components of the universe. Though normal matter—like stars, planets, and gas—makes up everything we can see, it accounts for only about 5% of the universe. The rest consists of invisible substances that do not emit or absorb light. Understanding dark matter and dark energy is crucial because they control how the universe behaves and evolves.

Evidence for Dark Matter

Scientists first suspected the existence of dark matter when they observed the rotation of galaxies. Stars at the edges of spiral galaxies move much faster than expected based on the visible mass present. According to the laws of gravity, there should be much more mass holding these fast-moving stars in place than what can be seen. Further evidence comes from observations of galaxy clusters. The total visible matter in these clusters is not enough to account for the gravitational forces measured. Another clue is gravitational lensing, where light from distant objects bends more than visible mass alone can explain. These findings suggest that about 27% of the universe is made up of dark matter. Scientists think it may be composed of unknown particles like WIMPs (Weakly Interacting Massive Particles), but no one has detected them directly yet.

Discovering Dark Energy

While dark matter pulls things together with gravity, dark energy works in the opposite way. In 1998, astronomers studying supernovae (exploding stars) found that these distant objects were dimmer than expected. This discovery meant that the universe is not just expanding, but the rate of expansion is speeding up. Dark energy is the name given to the mysterious force causing this acceleration. It makes up about 68% of the universe. Some scientists think dark energy might be a property of space itself, often described as the cosmological constant, a term first used by Albert Einstein.

Unsolved Mysteries and Interactions

Dark matter and dark energy interact with normal matter in indirect ways. Dark matter influences the formation and structure of galaxies by adding extra gravity, while dark energy affects how the universe expands on the largest scales. Despite decades of research, scientists still do not know exactly what dark matter and dark energy are made of. Their existence is one of the biggest mysteries in modern science. Understanding them could lead to major discoveries about the fate and structure of the universe.

In summary, the universe is about 68% dark energy, 27% dark matter, and only 5% ordinary matter. Studying the unseen parts of the universe teaches scientists about the underlying forces that shape everything, reminding us that there is still much to discover.

Interesting Fact: Even though scientists have built huge detectors underground and in space, no one has ever directly captured a particle of dark matter!

What percentage of the universe is made up of dark energy?

What evidence suggests the existence of dark matter in galaxies?

What is gravitational lensing?

What is another name for the possible particles that make up dark matter?

Why is dark energy important in the universe?

What does the term 'cosmological constant' refer to in the passage?

What did astronomers discover about the expansion of the universe in 1998?

Why haven't scientists directly detected dark matter yet?

True or False: Dark matter makes up more of the universe than normal matter.

True or False: Dark energy pulls galaxies together with gravity.