Waves and Strings: Gravity's Impact on Plucked Strings from Earth to Orbit

  • Context: Undergrad 
  • Thread starter Thread starter Icebreaker
  • Start date Start date
  • Tags Tags
    Strings Waves
Click For Summary

Discussion Overview

The discussion revolves around the effects of gravity on waves in a string, particularly in extreme scenarios such as a string extending from Earth to a geostationary satellite and beyond, including the implications of black holes and event horizons. Participants explore theoretical aspects of wave propagation, gravitational effects, and the nature of mechanical waves in different gravitational contexts.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions whether gravity would affect the wave created by plucking a string attached to a satellite, suggesting that since the particles move sideways, gravity should not have an impact.
  • Another participant argues that gravity would affect the tension in the wire, which in turn would affect the wave speed, and clarifies that a wire from Earth to a geostationary orbit would not remain stationary due to gravitational forces.
  • A hypothetical scenario is introduced about dropping a string past the event horizon of a black hole, raising questions about the transmission of mechanical waves in such extreme conditions.
  • Some participants assert that no information can escape past the event horizon, challenging the idea that mechanical waves could be transmitted out, and question the nature of these waves in relation to electromagnetic interactions.
  • Concerns are raised about the physical integrity of a string under the extreme gravitational forces near a black hole, suggesting that matter cannot withstand such conditions.
  • A later reply introduces the concept of space around the event horizon dilating to infinity, proposing that this leads to a frequency of zero, thus preventing any information from traveling out of the event horizon.

Areas of Agreement / Disagreement

Participants express differing views on the effects of gravity on wave propagation in strings, particularly in extreme scenarios. There is no consensus on the feasibility of transmitting mechanical waves past the event horizon of a black hole, with multiple competing perspectives remaining unresolved.

Contextual Notes

Participants highlight limitations in their thought experiments, including assumptions about the nature of mechanical waves and the physical properties of strings under extreme gravitational conditions. The discussion also reflects uncertainty regarding the implications of gravitational effects on wave speed and transmission.

Icebreaker
If I attached a long string from the ground to a geostationary satellite in orbit, and plucked it, would the wave created by the string be affected by gravity? The particles in the string move sideways, so the wave itself should not be affected by the Earth's gravity, should it?
 
Physics news on Phys.org
It will be affected by gravity in a rather subtle way: the tension in the wire would vary with distance from the Earth so the wave speed would also vary.

By the way, a wire from the Earth to "stationary orbit" would not stay in position. Stationary orbit is where there is no vertical force on points at that height. Every part of the wire below stationary orbit would be pulled downward so if you stop at stationary orbit, there will be a net downward pull. Of course, if you extend past stationary orbit, each part of the wire above it will be pulled upward. In order to get zero net vertical pull, you would have to extend MANY times that distance above stationary orbit ("many times" because of the drop off in gravitational force).
 
Ok, let's assume that space station is attached with a string at a point where it will be stable. The only thing that should vary, in theory, is the wave's speed.

What if we were to drop a string strong enough, attached from a ship, past the event horizon of a black hole?
 
You would never see the string go past the event horizon...
 
No, but it is said that no information can be transmitted out of anything past the event horizon. However, since particles in a physical string are not affected by the downwards pull, it should be possible to send mechanical waves out past the EH the same way a mechanical wave would travel in the first post.
 
Icebreaker said:
No, but it is said that no information can be transmitted out of anything past the event horizon. However, since particles in a physical string are not affected by the downwards pull, it should be possible to send mechanical waves out past the EH the same way a mechanical wave would travel in the first post.

Maybe you should consider the exact nature of these "mechanical waves" and figure out why they are nothing more than EM interactions/light. If light can't escape the event horizon, how do you propose these "mechanical waves" can?

Zz.
 
If there can be no interactions between particles past the event horizon, then everything just "breaks down" when past it?
 
Icebreaker said:
No, but it is said that no information can be transmitted out of anything past the event horizon. However, since particles in a physical string are not affected by the downwards pull, it should be possible to send mechanical waves out past the EH the same way a mechanical wave would travel in the first post.
How would you get a string (even an ideal one) to stand up to a gravitational force strong enough to stop photons?

I know you're doing a thought experiment, but you must accept the fact that matter will not withstand the forces generated within a BH.
 
Ok I've just come across another explanation. Even assuming the string to be unbreakable, and I'm quoting here, "space around the event horizon dilates to infinity, and infinite wavelength = 0 frequency, therefore no info travel out of EH". Any validity in that?
 

Similar threads

Graduate Real image of a sawtooth standing wave in a musical string?
  • · Replies 41 ·
2
Replies
41
Views
17K
How can I pluck strings (with changing length) with constant energy?
  • · Replies 1 ·
Replies
1
Views
1K
Undergrad Does plucking one point on the string really can cause standing wave?
  • · Replies 4 ·
Replies
4
Views
3K
High School How can standing waves be created on a string fixed at both?
  • · Replies 2 ·
Replies
2
Views
2K
Ball on a string thrown around a spool
  • · Replies 3 ·
Replies
3
Views
1K
Undergrad How Do Waves Propagate on a String?
  • · Replies 0 ·
Replies
0
Views
5K
Question about Waves on a String
  • · Replies 2 ·
Replies
2
Views
2K
Undergrad Understanding Strings: Basic Concepts Explained
  • · Replies 2 ·
Replies
2
Views
1K
Undergrad Earth's orbit not perfect ellipse
  • · Replies 19 ·
Replies
19
Views
3K
Undergrad Mechanism of Energy Conservation in Zero-Amplitude Sum of EM Waveforms
  • · Replies 21 ·
Replies
21
Views
4K