Which Way Is Down?

TL;DR

Objects fall due to the curvature of space-time, which causes them to follow a straight path in a curved space. The direction of down is relative and always changing based on the curvature of time.

Transcript

Hey, Vsauce. Michael here. Down here. But which way is down? And how much does down weigh? Well, down weighs about a 100th of a gram per cubic centimeter. It is light and airy, which makes it a great source of insulation and buoyancy for water birds. But if you let go of down... It falls down. So that's which way down is. It's the direction gravity... Read More

Key Insights

• 👾 Objects fall because they follow a straight path (geodesic) in a curved space-time caused by the Earth's mass.
• ⌛ The direction of down is relative and always changing based on the curvature of time.
• 💆 Weight is the force experienced due to the attraction of two masses, while mass is an intrinsic property that determines an object's resistance to changes in motion.
• 👾 The strength and direction of gravity are determined by the curvature of space-time caused by the distribution of mass and energy.
• 😣 The Equivalence Principle, proposed by Einstein, states that freefall and being at rest in space are indistinguishable.
• 🙂 The overall shape and composition of the Earth affect the direction and strength of gravity, causing slight variations in apparent weight.
• 🏋️ Buoyant forces, caused by the pressure differences in fluids, provide lift and make objects appear to weigh less in certain conditions.

Questions & Answers

Q: How does the curvature of space-time cause objects to fall?

The curvature of space-time caused by the Earth's mass creates a cone-shaped space-time, and objects fall because they naturally follow a straight path in this curved space.

Q: Is the weight of an object determined by its mass?

No, weight depends on the mass of the object and the mass of the attracting object. Weight can be calculated using Newton's equation, which takes into account the masses and the distance between their centers.

Q: Why do objects fall at the same rate regardless of their mass?

Objects fall at the same rate because the force of gravity is proportional to the product of their masses and inversely proportional to the square of the distance between their centers. This means that the acceleration due to gravity is the same for all objects.

Q: How does the direction of down change based on the curvature of time?

The direction of down is relative and always changing based on the curvature of time. Down is the direction of slower time, so objects naturally move towards where time is slower, which is towards the Earth's center.

Summary & Key Takeaways

• Objects fall because they follow a straight line (geodesic) in a curved space-time caused by the Earth's mass.

• Down is the direction of slower time, which is why objects are naturally steered towards it.

• Weight is the force experienced due to the attraction of two masses, while mass is an intrinsic property that determines how hard it is to change an object's motion.