The Naked Scientists

The Naked Scientists Forum

Author Topic: Where does the energy from a gravitational field go?  (Read 8824 times)

Offline JohnDuffield

  • Sr. Member
  • ****
  • Posts: 488
  • Thanked: 1 times
    • View Profile
Re: Where does the energy from a gravitational field go?
« Reply #25 on: 16/11/2014 12:58:21 »
The author is talking about 2 contributions. One from the mass and one from the field itself.
Interestingly, when you get down to the level of the electron, when you probe it, you don't detect anything in the middle. It's all just field.
 

Offline jeffreyH

  • Global Moderator
  • Neilep Level Member
  • *****
  • Posts: 3914
  • Thanked: 53 times
  • The graviton sucks
    • View Profile
Re: Where does the energy from a gravitational field go?
« Reply #26 on: 16/11/2014 15:05:15 »
Quote from: jeffreyH
This post made my day.
Excellent! :)

Quote from: jeffreyH
The middle is the centre of gravity and therefore within the mass itself. If this is a particle then your argument makes no sense.
What is the gravitating body that you're talking about? The center of gravity isn't always the center of mass.

Badly expressed Pete. Point taken.
 

Offline jeffreyH

  • Global Moderator
  • Neilep Level Member
  • *****
  • Posts: 3914
  • Thanked: 53 times
  • The graviton sucks
    • View Profile
Re: Where does the energy from a gravitational field go?
« Reply #27 on: 16/11/2014 15:14:28 »
Quote from: alancalverd

Quote
The field must have energy.

Not true - indeed meaningless. You need to expend energy to move a particle that interacts with the field.

Not true at all. The gravitational field most certainty does have energy. That's a well-known fact in gravitational physics. See:
http://www.grc.nasa.gov/WWW/k-12/Numbers/Math/Mathematical_Thinking/possible_scalar_terms.htm

Slight problem here. The dimensions of energy are ML2T-2 but those of gravitational field intensity are LT-2 and gravitational field potential L2T-2. No energy is involved until you introduce a mass into the field.

Thanks for this post Alan. A useful page for quick checks is http://www.ebyte.it/library/educards/sidimensions/SiDimensionsByCategory.html
 

The Naked Scientists Forum

Re: Where does the energy from a gravitational field go?
« Reply #27 on: 16/11/2014 15:14:28 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums