Daniel and Kelly’s Extraordinary Universe How fast are we moving?
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Jan 22, 2026 Daniel and Kelly explore the perplexing nature of velocity and how it's defined relative to objects. They dive into Earth's spin and orbit, revealing fascinating measurable effects. Discover the surprising speed at which our planet travels and the sun's impressive galactic motion. They discuss the cosmic microwave background's role in measuring our movement, along with intriguing discrepancies found in galaxy studies. Ultimately, they emphasize that motion is inherently relative and the importance of selecting a cosmic reference frame.
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Velocity Is Always Relative
- Velocity has no absolute meaning; it only exists between pairs of objects in a chosen reference frame.
- Acceleration is absolute and measurable inside a closed box, making it fundamentally different from velocity.
Acceleration Is Detectable, Velocity Isn't
- Velocity equals the change of position over time and depends on the chosen coordinate origin.
- Acceleration equals the change of velocity and can be detected inside a sealed box by simple experiments like dropping a ball.
Everyday Speeds: Spin And Orbit
- The Earth spins at about 1,600 km/h at the equator and this rotation produces measurable effects like slightly lower weight.
- The Earth's orbit around the sun yields roughly 30 km/s and this was derived from Keplerian dynamics.
