Hubble's law | Scale of the universe | Cosmology & Astronomy | Khan Academy

TL;DR

As the universe expands, objects move away from each other at velocities proportional to their distance.

Transcript

Over many videos now, we've been talking about how every interstellar object is moving away from Earth. And we've also been talking about how the further something is away from Earth, the faster it's moving. What I want to do in this video is to put a little bit of numbers behind it, or even better conceptualize what we've been talking about. So on... Read More

Key Insights

• 💨 Interstellar objects are moving away from Earth due to the expansion of the universe.
• 💨 The apparent velocity with which objects are moving away is proportional to their distance.
• 💨 Hubble's Law states that the relative velocity of objects moving away is directly proportional to their distance.
• ❓ The current Hubble Constant is approximately 70.6 kilometers per second per megaparsec.
• 😥 The expansion of the universe can be visualized as points on a grid or the surface of a sphere expanding.
• 💨 Objects closer to Earth move away at slower velocities compared to objects further away.
• 👾 The expansion of the universe affects distances between objects but not their motion in space.

Questions & Answers

Q: How does the expansion of the universe affect the distances between objects?

The expansion of the universe causes objects to move away from each other, increasing the distances between them.

Q: Why do objects further from Earth move away faster?

Objects further from Earth move away faster because they not only experience the general expansion of the universe but also the cumulative expansion from other objects in between.

Q: Can the expansion of the universe be visualized?

Yes, the expansion can be visualized as points on a grid or the surface of a sphere moving away from each other.

Q: How do we know that objects are moving away from each other?

Scientists can observe the redshift of objects, which indicates that they are moving away, and by comparing the redshifts of different objects, they can determine their relative velocities.

Summary & Key Takeaways

• Every interstellar object in the universe is moving away from Earth due to the expansion of the universe.

• The further an object is from Earth, the faster it is moving away.

• The expansion can be visualized as points on a grid moving away from each other, or the surface of a sphere expanding.