# Tugging on a Chain: Earth-Moon Connection Explored

• OSalcido
In summary, tugging on a solid chain from Earth to the moon's surface would result in a shock wave traveling at 5km/s. This would cause both the attached and unattached chains to stretch and move, as no material is completely rigid. This concept is important in the development of a "space lift" or "space elevator."
OSalcido
Imagine a solid chain from the Earth to the moon's surface (which I believe is 1.5 light seconds away).

Now Imagine two scenarios.
First scenario is that the chain is attached directly to the moon's surface.
Second scenario is the chain is unattached.

What happens if I tug on the chain in both scenarios? If information travels at the speed of light, how does the universe know whether I should be able or unable to pull the chain at that moment?

What happens if I tug on the chain in both scenarios?
A shock wave creeps up the chain with a speed of ~5km/s. A highly sophisticated interferometer at the moon might have a chance (well, not really) to detect it one day later.

The answer is that no material is completely rigid and both the chains will initially stretch (by the same amount) when tugged. For the time it takes the shock wave to get to the other end of the chain (A minimum of 1.5 seconds but in practice a lot longer because shock waves in a material travel at the speed of sound in that material) the chains will both behave the same, with the end you are tugging moving while the far end is stationary.

In practice it would be difficult to find a material that will not stretch and break under its own weight even before tugging. Google for "space lift" or "space elevator" to see a related subject.

ah so that's what they mean when they talk about rigid bodies

thank you both :)

Btw, that 5km/s that Ich was talking about is the speed of sound in metal (didn't check the number, but it sounds reasonable).

## 1. What is the Earth-Moon connection?

The Earth-Moon connection refers to the gravitational and tidal forces between the Earth and the Moon, which affect the movements and behaviors of both bodies.

## 2. How does the Earth-Moon connection affect the tides?

The gravitational pull of the Moon on the Earth's oceans causes the tides to rise and fall. This is because the Moon's gravitational force is stronger on the side of the Earth that is facing the Moon, pulling the water towards it. This creates high tide. On the opposite side of the Earth, the water is pulled away from the Earth, causing low tide.

## 3. What other effects does the Earth-Moon connection have on the Earth?

In addition to affecting the tides, the Earth-Moon connection also causes the Earth's axis to tilt slightly, which is responsible for the changing of the seasons. The Moon also helps stabilize the Earth's rotation and slows it down, resulting in longer days over time.

## 4. Is the Earth-Moon connection constant?

No, the Earth-Moon connection is not constant. The Moon's orbit around the Earth is not a perfect circle, and its distance from the Earth can vary by about 30,000 miles. This means that the strength of the Earth-Moon connection can change, affecting the tides and other phenomena.

## 5. How do scientists study the Earth-Moon connection?

Scientists use various methods to study the Earth-Moon connection, including satellite data, mathematical models, and physical observations. They also use techniques like laser ranging and lunar seismometers to measure the Moon's distance from the Earth and its movements, providing valuable insights into the dynamics of the Earth-Moon connection.

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