Neutrinos & Gravity: Faster than Light?

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Discussion Overview

The discussion revolves around the relationship between neutrinos and gravity, specifically questioning whether neutrinos could travel faster than light when passing through gravitational fields. Participants explore concepts related to the nature of gravity, its propagation, and the implications of these ideas on the behavior of neutrinos.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • Some participants suggest that since gravity takes time to affect a neutrino, it might lead to a scenario where neutrinos could exceed expected velocities when entering a gravitational field.
  • Others argue that gravity is a field present at every point in space, and therefore does not have a velocity; only changes in gravity propagate at a certain speed.
  • A participant questions whether the gravitational field changes for the neutrino as it approaches Earth, noting that the gravitational gradient is not delayed.
  • There is a discussion about the implications of gravity being instantaneous versus having a speed, with references to the propagation of changes in gravity being at the speed of light.
  • Analogy of a boat on water is used to illustrate the concept of gravity as a field and the propagation of changes in that field.
  • Some participants express confusion about the nature of gravity's speed and its instantaneous effects, referencing previous discussions and contributions from others in the thread.

Areas of Agreement / Disagreement

Participants generally disagree on the nature of gravity's speed and whether it can be considered instantaneous. While some agree that gravity does not have a velocity, they acknowledge that changes in gravity propagate at the speed of light. The discussion remains unresolved regarding the implications for neutrinos and their interaction with gravitational fields.

Contextual Notes

Participants express uncertainty about the definitions and implications of gravity's properties, particularly concerning the speed of gravity and its effects on particles like neutrinos. There are references to previous statements and analogies that may not be fully resolved within the current discussion.

keepitmoving
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Since it takes time for gravity to have an effect on a neutrino, wouldn't a neutrinos velocity be greater than expected when entering and passing through a gravitational field, i.e. faster than light neutrinos passing through part of the earth?
 
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Gravity does not have a velocity. Gravity is a field. That means it has a value at every point in space. No matter where a particle is, it is under immediate influence of the gravitational field at that point.

What has a velocity is the propagation of changes in gravity.
 
keepitmoving said:
is the field changing for the neutrino as it approaches?
Certainly the neutrino experiences a gravitational gradient as it approaches Earth, but there is no delay. The gravity is not traveling from anywhere. It is present at every point, so the gradient is not delayed.
 
DaveC426913 said:
Gravity does not have a velocity. Gravity is a field. That means it has a value at every point in space. No matter where a particle is, it is under immediate influence of the gravitational field at that point.

What has a velocity is the propagation of changes in gravity.

I float in and out of here occasionally, hoping as a layman (perhaps not even that) to make sense of some of the fundamentals (such as 'curvature' on the other thread, which I hope to get to).

I could have sworn that over time, I've seen statements from serious contributors here, that gravity does have speed / velocity (if I'm mistaken, apologies up front).

Anyway, trying to understand this - gravity has no speed - it it instantaneous ? (such I would have, and do, instinctively believe).

So, if the sun for instance, was to blink out of existence at 10 PM tonight, the Earth would be free from it's infuence at that time ? Not 8 minutes later ?
 
alt said:
So, if the sun for instance, was to blink out of existence at 10 PM tonight, the Earth would be free from it's infuence at that time ? Not 8 minutes later ?
As Dave said, changes in gravity have velocity. It will take about 8 minutes after the sun disappears for this change to reach you, then you will be free of it's influence.
When people talk about the speed of gravity, they are talking about the speed at which changes in the gravitational field move at, just like the speed of light is the speed at which changes in the electromagnetic field move at. They are both c.
 
Last edited:
As a very loose analogy think about a boat on water.

Like, gravity, water is a field - it is everywhere at all times, though it may have different values at different points. The boat is always in contact with the water.

However, waves in the water have a fixed speed limit. If something occurs to change the water level (say, a lock floodgate opens), that change will only propagate at the speed of the waves.
 
alt said:
I could have sworn that over time, I've seen statements from serious contributors here, that gravity does have speed / velocity (if I'm mistaken, apologies up front).

No, as Dave has pointed out, gravity does not have a velocity. You're thinking of statements about the CHANGES in gravity, which, as he has also pointed out, propagate at light speed.

[I love repeating what Dave says ... he's so coherent :smile: ]
 
Gravity is not 'instantaneous', despite what tom van flandern suggests.
 
phinds said:
No, as Dave has pointed out, gravity does not have a velocity. You're thinking of statements about the CHANGES in gravity, which, as he has also pointed out, propagate at light speed.

[I love repeating what Dave says ... he's so coherent :smile: ]

Agree.

Dave, the boat / water analogy was a very good one. 'Splained it for me - thanks.
 
  • #10
alt said:
Agree.

Dave, the boat / water analogy was a very good one. 'Splained it for me - thanks.

See Dave ... you do the explaining and I get the thanks. This is the way it should be. :smile:
 
  • #11
phinds said:
See Dave ... you do the explaining and I get the thanks. This is the way it should be. :smile:

:curtsy:
 

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