From StarTalk.

What would a four-dimensional being see if it looked at us? In this episode, Neil deGrasse Tyson and Chuck Nice answer fan questions covering higher-dimensional surgery, space elevators, alien intelligence, and colliding galaxies. Could spacetime itself be a cosmic crystal?

Could 2D creatures exist, and if so, how would we even know? If 4D beings turned sideways, would we disappear like cartoon characters? We wonder whether we could make 4D surgeons do our operations for us. Could the Trantor Starbridge from Foundation actually work? Neil explains the physics behind a space elevator, how it would reach geostationary orbit, and why the dream faded once rockets got efficient. Chuck wants to know what kind of music you’d play during the world’s longest elevator ride.

If a superintelligent alien could answer any one question, what would you ask? Neil wonders if the human brain is smart enough to understand the entire universe, or are we just too dumb? Can learning happen without human connection? Neil argues that even an AI tutor can’t replace the ever-changing human condition. What makes spacetime flat? Can there ever be a “universal now”?

We ask whether you’d need absolute coordinates to return somewhere, factoring in the expansion of the universe. Finally, we explore the cosmic heavyweights: supermassive black holes. Could they swallow entire galaxies? What happens when two galaxiesand their black holes collide? Neil explains why the universe is mostly empty space, how black holes grow through mergers, and whether spacetime itself might behave like a supersonic lattice or even a cosmic crystal.

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Timestamps:
00:00 – Introduction: Grab Bag
01:23 – Do 2D Beings Exist?
06:21 – Could We Make a Space Elevator?
11:36 – Neil’s Question For an Advanced Alien
17:10 – Is Human Connection Essential for Learning?
19:23 – Why is Spacetime Flat?
21:16 – Is There a Universal Now?
23:32 – Pitfalls of Time Travel
28:45 – Does Light Ever Do Work?
35:00 – Will Our Black Hole Swallow the Galaxy?
39:29 – When Galaxies Collide
41:22 – Could Spacetime Be A Crystal?

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About StarTalk:
Science meets pop culture on StarTalk! Astrophysicist & Hayden Planetarium director Neil deGrasse Tyson, his comic co-hosts, guest celebrities & scientists discuss astronomy, physics, and everything else about life in the universe. Keep Looking Up!

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