Dark Energy, Cosmology part 2: Crash Course Astronomy #43

The majority of the universe is made up of a currently mysterious entity that pervades space: dark energy. We don’t know exactly what it is, but we do know that dark energy accelerates the expansion of space. We think this means the Universe will expand forever, even as our view of it shrinks while space expands faster all the time.

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Chapters:
Introduction: The Expanding Universe 00:00
The Expansion of Space is Accelerating 2:17
What is Dark Energy? 4:19
Will the Universe Expand Forever? The Geometry of the Universe 5:20
The Cosmic Horizon of the Observable Universe 6:50
Review 10:20
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GEOMETRY OF THE UNIVERSE RESOURCES
Geometry:

Expanding faster than light:

General expansion:

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PHOTOS/VIDEOS

[caleblimb]

We better hurry, we only have a few trillion years left. I wonder if that gives me enough time to grab a coffee first.

[shiminshamim]

I never expected astronomy to be this heartbreaking and terrifying...

[AgentJohnSteed]

This is one of the most terrifying videos I have ever watched.

[icam]

The scariest thing to me is that if there is alien life, they might live in a galaxy so distant that with every second that passes, they get closer to leaving our observable universe. Forever.

And this may have already happened, many, many times...

[RafaelBenedicto]

NOTHING can go faster than light.

But space itself is literally NOTHING. So the 1st statement holds true.

[yaseenalsaif]

"if you want more information, we have links in the doobly doo"

-Phil Plait

[BearsThatCare]

I really thought I hatted astronomy. I took a class in 8th grade and I thought it was just boring calculations that were tedious to make. I thought the Universe was generally boring and the Earth incredibly amazing, but these videos have changed my mind completely.

[adriansinpilot]

"We live in a special time, the only time, where we can observationally verify that we live in a special time."

[frodiingsson]

"That would be a cosmic joke, " the skeptic told the bartender.
"What?" the bartender inquired.
"If dark energy is nothing more than mind."
"How's that?"
"You can't see or measure it, but there's no doubt it moves matter around."

The bartender smiled as she responded, "It's also what fills many of my customers' heads."
"What's that?" the skeptic asked.
"A lot of empty space."

[geniusmp]

It's one of my favorite little oddities about cosmology. The rate at which the expansion is changing is known as the deceleration parameter, because of course everyone expected the expansion to be decelerating. But the deceleration parameter is negative.

[BassWiz]

Holy fuck. Stop the universe, I wanna get off now.

[doltBmB]

"We can't see it, we can't measure it, there's literally no evidence that it's there but the math says it has to be so you better believe it."

[Leolukpeu]

6:54 who watches youtube standing up?? o_O

[pixelcraftbuilds]

I have to watch this 5 times to literally confirm what i've just heard

[brandonhall]

Why does dark energy have to be such a jerk?

[gijsklaassen]

My mouth fell open when he started talking about moving faster than the speed of light O_0

[frsn]

Although my english isn't very well because I'm french, it's very interesting, kipe going like that.

You have a new French fan.

[darkmage]

Surprised this episode isn't just 10 seconds long:

"Dark Energy: We have NO clue, people. None. Thanks for watching!"

[Physick]

I just want to say this has been the best Astronomy video series I have ever seen online. You have a great way of teaching and explaining things Phil.

[markuskekero]

I have to sleep to school but oh look another crash Irony