Reissner–Nordström metric visualization (possibly, geodesics too?)

[aSimpson02]

Created a new notebook/example focusing on the reissner nordstrom metric, a non EV metric solution.- #626

[JeS24]

@aSimpson02 Could you update the PR description with the issue number and a list of changes that you have made? I believe, the related issue is #626 (first one in the list there).

[JeS24]

Also, update the PR title accordingly.

[aSimpson02]

hi, thanks for the feedback, I will be working on this today.

[aSimpson02]

hi I have updated the PR description and title, please let me know if i need to change anything else.

[JeS24]

@aSimpson02 Thanks for the PR. Some changes & additions are needed. The referenced issue (#626) talks about adding tutorial notebooks to showcase the ability to pass custom Python functions that define a metric, to the Geodesic module, to compute geodesics in such spacetimes. See https://github.com/einsteinpy/einsteinpy/pull/625/files for an example with the Kerr metric (_kerr). Your notebook only defines and plots the metric. Can you try integrating it with Geodesic like it is done in this example: https://github.com/a3ahmad/einsteinpy/blob/e56fd9ed7a752f0997ae63a2ceee2247fc2a9019/tests/test_geodesic/test_geodesic.py#L175 with _kerr?

Besides this, there are two non-issues that should be noted regardless:

1. The RN metric is an electro-vacuum (EV) solution. Although, for the sake of this example notebook, it's not an issue.
2. The geometric unit system used by the numerical part of EinsteinPy sets $G = c = M = 1$ (so-called M-units). So, mass is technically not required, but we'll keep it as-is.

[JeS24]

Restore this file.

[JeS24]

Restore this file.

[JeS24]

1. Add a title at the top in markdown (text):

   # Reissner–Nordström metric
   

2. Fix capitalization and use markdown to style the text, like so (See: https://github.com/aSimpson02/einsteinpy/blob/main/docs/source/examples/Visualizing%20Frame%20Dragging%20in%20Kerr%20Spacetime.ipynb for an example)

   ### Importing libraries
   
   ### Defining the metric function
   
   ### Compute metric components
   
   ### Visualise the metric
   

[aSimpson02]

hi I have attempted the markdown style, please tell me if this is ideal, thank you !

[JeS24]

Looks fine.

[JeS24]

Though, the capitalization of the last header is incorrect.

### Visualise the metric

[aSimpson02]

hi apologies, I accidentally clicked resolved, I am currently working on this issue now.

[JeS24]

No problem.

[JeS24]

If you run into any problems during the restoration process, don't hesitate to ask for help.

[aSimpson02]

hi, apologies, I am struggling to restore the files that I accident deleted here in the pull request, can you recommend me any way I can retrieve them back into the project.

[JeS24]

The fastest way would be to move the Reissner-Nordström metric.ipynb notebook file out of the local git repo folder, and to reset the local git repo to the last commit, before your changes, like so:

# NOTE: First, move the Reissner-Nordström metric.ipynb out of the repo (as a backup).
# Use Finder / File Explorer for this or use the `mv` command if using terminal.

# Then, reset the repo locally:
git fetch --all
git pull
git reset --hard e56fd9ed7a752f0997ae63a2ceee2247fc2a9019 # <-- Hash of the last commit before your changes. This command would reset your local git repo to this commit. This should restore those files locally.

# Force-push the change to your fork on GitHub, so that the other files are restored everywhere
git push -f

# Move the file back to `.../docs/source/examples/`
# Use Finder / File Explorer for this or use the `mv` command if using terminal.

# Then, commit & push again.
git commit -m "Added Reissner-Nordström metric.ipynb"
git push