Why the Sky ISN'T Blue

TL;DR

The sky appears blue due to Rayleigh scattering, and the lack of violet light dominance. Spinning hard disk drives on laptops can cause the laptop to spin in the opposite direction due to conservation of angular momentum. Once past the event horizon of a black hole, there is no return. The universe is flat and will continue to expand, causing galaxies to eventually recede faster than the speed of light.

Transcript

Happy 500,000! Thank you guys so much for subscribing to my channel and for joining me on this scientific adventure. You know, if you got 500,000 people together and we all held hands in a line, it would stretch from Sydney to Melbourne or from San Francisco to San Diego or from London to Inverness. >> Oy. What are you forming a line here for? You ... Read More

Key Insights

• 🩵 The sky appears blue due to Rayleigh scattering, which scatters shorter wavelengths of light.
• 💻 Conservation of angular momentum explains why spinning hard disk drives can cause laptops to spin in the opposite direction.
• 🖤 Once past the event horizon of a black hole, there is no return, and time perception changes.

Questions & Answers

Q: Why does the sky appear blue?

The sky appears blue due to Rayleigh scattering, where shorter wavelengths of light, particularly blue light, are scattered more than other colors.

Q: Will a spinning hard disk drive cause a laptop to spin?

According to conservation of angular momentum, spinning a hard disk drive will cause the laptop to spin in the opposite direction at a rate relative to the speed of the hard disk drive.

Q: What happens if you pour liquid oxygen on a fire?

Pouring liquid oxygen on a fire can cause an explosive reaction, as oxygen accelerates combustion.

Q: What happens when someone goes past the event horizon of a black hole and tries to return?

Once past the event horizon of a black hole, there is no return. Time for the person entering would slow down, and to an outside observer, it would appear as though the person never returned.

Q: Is there anyone specific you would love to meet?

The speaker expressed interest in meeting Bill Nye, Neil deGrasse Tyson, Richard Dawkins, and President Obama.

Q: Will galaxies ever reach the speed of light or stop accelerating?

Galaxies are continuously accelerating away from each other, and at some point, their rate of recession will be faster than the speed of light relative to us. However, they are gravitationally bound and will not move through space faster than light speed.

Q: Is there randomness in the universe?

Quantum mechanics suggests that randomness is a fundamental part of the universe, as some events have probabilistic outcomes that cannot be determined by hidden variables.

Q: Can light from our sun go around the universe and hit the other side of Earth?

The shape of the universe appears to be flat, and therefore no large-scale curvature would allow light to go around and hit the other side of the Earth.

Summary & Key Takeaways

• The sky appears blue due to Rayleigh scattering, which scatters shorter wavelengths of light, primarily blue light.

• Spinning hard disk drives on laptops will cause the laptop to spin in the opposite direction due to conservation of angular momentum.

• Once an object passes the event horizon of a black hole, there is no return, and both the observer and the person who entered would experience a different perception of time.

• The universe is flat and will continue to expand, causing galaxies to eventually recede faster than the speed of light.