Collision of Milky Way and Andromeda galaxies: a simulation

- This event will take place 4 billion years from now, and will last several billion years to complete.

- Because stars in each galaxy are so far apart, very few stars may ever collide. However, some stars will be thrown out of their galaxies at high speed due to the effect of gravity.

(Taken from Cosmos episode 3: When Knowledge Conquers Fear)

For teaching: astrophysics


For many ancient cultures, a comet’s appearance in the sky was seen as a precursor to destruction, disease and other major problems that mean bad news for the people of the region.

The comet of 1664 sent shivers of threat throughout Europe, and the terror seem justify when the plague and the Great Fire of London followed soon after.

But for one child, the comet was not the least bit frightening. For him, it was a thing of wonder.”

That child was Edmond Halley, an English scientist who predicted the orbits of comets around the sun for the first time. By recognizing a pattern in his research, Halley was the first to track the period of the comet eventually named for him.

[Cosmos: A Spacetime Odyssey Episode 3, “When Knowledge Conquered Fear”]

We hunger for significance. For signs that our personal existence is of special meaning to the universe. To that end, we’re all too eager to deceive ourselves and others, to discern a sacred image in a grilled cheese sandwich or find a divine warning in a comet.
—  Neil deGrasse Tyson, Cosmos: A Spacetime Odyssey (Ep. 3: When Knowledge Conquered Fear)

“Newton’s laws made it possible for Edmund Halley to see some 50 years into the future and predict the behavior of a single comet. Scientists have been using these laws ever since, opening the way to the moon and even beyond our solar system – The baby in the basket is learning to walk and to know the cosmos." 

- Cosmos: A Spacetime Odyssey / Ep. 3 ”When Knowledge Conquered Fear

When Isaac Newton was born in this house in 1642, the world was very different. Everyone looked at the perfection of the clockwork motions of the planets in the sky and could only understand it as the work of a master clockmaker. How else to explain it? There was only one way such a thing could come about in their imagination. God. For reasons beyond our understanding, God just created the solar system that way. But that explanation is the closing of a door - it doesn’t lead to other questions.

With one foot still in the Middle Ages, Isaac Newton imagined the whole solar system. Newton’s laws of gravity and motion revealed how the sun held distant worlds captive. His laws swept away the need for a master clockmaker to explain the precision and beauty of the solar system. Gravity is the clockmaker. Newton’s answer to why the solar system is the way it is opened the way to an infinite number of questions.

—  Neil deGrasse Tyson, Cosmos: A Spacetime Odyssey (Ep. 3: When Knowledge Conquered Fear)