Briefly about what is dark matter and dark energy?

Andy Green

Transcript

00:00Dark matter and dark energy are two mysterious substances that make up most of our universe,

00:06but their nature remains largely unknown.

00:09Although we can't see them directly, scientists are confident they exist because of the way

00:13they influence stars, galaxies, and the universe as a whole.

00:18What is dark matter?

00:20Invisible but powerful, dark matter is a mysterious type of matter that doesn't emit, absorb,

00:26or reflect light.

00:28This makes it invisible to our telescopes.

00:30However, we know it exists because it affects visible objects with its gravity.

00:36Think of it like wind.

00:37You can't see the wind, but you can feel it and see how it moves leaves.

00:42How was dark matter discovered?

00:44The idea of dark matter was first proposed in the 1930s when astronomers noticed that

00:49galaxies were rotating much faster than they should be if they were made only of visible

00:53matter, like stars and planets.

00:56If only visible matter existed, the galaxies would fly apart due to the centrifugal force

01:02of their rotation.

01:03But something invisible and very massive was holding them together.

01:07That something was called dark matter.

01:10Example, gravitational lensing.

01:13One of the proofs of dark matter comes from observing a phenomenon called gravitational

01:17lensing.

01:19Light from distant galaxies bends as it passes through areas with a lot of invisible matter,

01:24dark matter.

01:25This bending of light is similar to how glasses lenses change the direction of light.

01:30Through these effects, scientists can estimate how much dark matter is in a particular region

01:34of space.

01:36How much dark matter is there?

01:38Scientists estimate that dark matter makes up about 27% of all the mass and energy in

01:43the universe.

01:44That's five times more than all the visible matter, stars, planets, and other objects,

01:50which makes up only 5% of the universe.

01:53What is dark energy?

01:55A force stretching the universe.

01:57Dark energy is even more mysterious than dark matter.

02:01It was discovered in the late 1990s when scientists found out that the universe isn't just expanding

02:06as predicted since the Big Bang, but it's expanding faster and faster.

02:11This was surprising because it was previously thought that gravity would slow down the expansion,

02:16not speed it up.

02:18Dark energy is a hypothetical force that acts like anti-gravity, making space itself

02:24expand faster.

02:25We don't know exactly what dark energy is, but essentially, it works against gravity,

02:31pushing galaxies away from each other.

02:33Example, a balloon.

02:35Imagine our universe is like a balloon with galaxies drawn on it.

02:39If you blow up the balloon, the galaxies move apart as the balloon expands.

02:44Dark energy is like the force causing the balloon to expand faster and faster.

02:49How much dark energy is there?

02:52Dark energy makes up a whopping 68% of the universe's total energy.

02:57This means that the vast majority of the cosmos is this mysterious energy that we can't see

03:02or measure directly.

03:04Why is it important?

03:05Dark matter and dark energy are crucial to understanding how our universe is structured

03:10and how it will evolve in the future.

03:12For example, the future of the universe.

03:15If dark energy continues to accelerate the universe's expansion, one day galaxies could

03:20drift so far apart that our corner of space would become completely empty.

03:25This is called the Big Rip.

03:27The shape and structure of the universe.

03:30Dark matter explains why galaxies have the structure we observe today.

03:34Without dark matter, they would have disintegrated or looked entirely different.

03:39Existing facts and evidence.

03:42Galaxies and star clusters.

03:43We can observe groups of galaxies and stars behaving as though they contain much more

03:48matter than we can see.

03:49This means there must be something invisible inside the galaxies.

03:53This is dark matter.

03:55Cosmic microwave background.

03:57This faint radiation left over from the Big Bang can be measured by scientists.

04:01Its variations confirm the existence of dark matter, which helped shape the formation of

04:06the first stars and galaxies.

04:08Dark matter and dark energy are mysterious but extremely important parts of the universe,

04:14about which we still know very little.

04:16They play a huge role in how the universe works and are among the most exciting and

04:20challenging questions in modern science.

04:23Scientists continue to work on unraveling their mysteries, and perhaps in the future

04:28we'll learn more about what makes up this vast part of the cosmos.

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