How do you create a link to a specific post?

  • Thread starter Imager
  • Start date
In summary, the conversation discusses the creation of a link to a specific post in PF, specifically Matterwave's post number 25. The best method is to click on the post number and copy the link location, which will include an extra number to indicate the specific post. It is also possible to highlight the post number and right click to copy the link location. However, this method may not work for all posts. Another method is to left click and drag the post number directly into the reply box. There is also a contest to rename the PF Lounge category, which can be accessed through a specific post number, such as Bernhardt's post number 102. However, there may be a slight offset in the link when using this method.
  • #1
Imager
Gold Member
112
61
How do you create a link to a specific post in PF? I want to link to Matterwave's post 25. The best I could come up with is this to the page...

https://www.physicsforums.com/threa...-energy-stress-curves-spacetime.956580/page-2
Matterwave said:
If you are looking for a nice derivation of General Relativity from first principles like you can derive special relativity from 1. The principle of relativity and 2. the constancy of the speed of light, you won't find one nearly that clean.

In GR though, you do have motivating principles that "hint at" the EFE's but none through which you can "derive" the EFEs. The principle which most motivates the EFEs is Einstein's principle of equivalence.

Your statement of "equivalence of inertial mass and gravitational mass" is the weak principle of equivalence (it's the one mostly experimentally tested for). The Einstein principle of equivalence goes beyond that statement to say essentially that there is no physical way to determine the difference between a locally free-falling reference frame and a reference frame which is truly free in the vacuum of space away from any gravitational fields (other than the gravity of the laboratory itself - i.e. not accounting for self-gravitating effects). In other words, if I stuck you in a small room that you couldn't see or hear or otherwise send signals out of, you couldn't, even in principle, tell whether you were free-falling toward's Earth at 9.8m/s^2 or whether you were floating out in the middle of space (at least, not until you crashed onto the Earth's surface - when your motion is no longer inertial).

The Einstein principle of equivalence says that not only do all bodies fall at the same rate regardless of their mass, but all physics behaves the same way in these differing reference frames. For example, light, even though it's massless, must still be affected by gravity. If, for example, massless particles are not affected by gravity, then one could differentiate the two differing situations by shining a laser (or a grid of lasers) and seeing if that laser (or a grid of lasers) curved away from you. This equivalence principle therefore suggests that it is in theory possible to describe gravity not as a force that acts on "gravitational mass", but as an inherent curvature in space-time. All material bodies are affected by gravity - not just those that have some "gravitational charge". This is very distinct from the case of e.g. the Electromagnetic force where neutrally charged bodies (that also have no magnetic dipole moment) are not affected by electromagnetism.

Einstein's EFE's which relate (the trace-reverse) Ricci curvature to stress energy directly are a beautiful manifestation of the Einstein equivalence principle, but it is not the unique possible theory that incorporates this principle. One can construct other theories which respect the Einstein principle of equivalence (e.g. Brans Dicke theory), but perhaps Einstein's theory is the most "simple" and elegant of them (this last statement is opinion based).

As a technical aside, there is also a strong principle of equivalence which is even more restrictive than Einstein's (in technical terms, it specifies that the space-time metric is the only field which can affect the space-time curvature). Apparently Einstein's General Relativity is thought to be the only theory which satisfies the strong principle of equivalence - but I am not certain of there being any proof of the fact.
 
Physics news on Phys.org
  • #2
If you click the little #25 (post number) above the post (to the right hand side, immediately left of the time stamp of the post), you will find a permalink to that particular post.
 
  • Like
Likes Imager, Greg Bernhardt and berkeman
  • #4
Imager said:
How do you create a link to a specific post in PF?
If you would like, just highlight the post number, then right click on the post number, then click copy...

You can then paste that number into your reply box... this will create an auto-link, right to that post, as such... #1 . :oldwink:

Here's a screen grab of the method...

upload_2018-10-4_16-59-14.png


I wish everybody would do this, it really saves on wasted scrolling time... especially, on long threads... . :oldsmile:

Matterwave's post 25... #25 .
 

Attachments

  • upload_2018-10-4_16-59-14.png
    upload_2018-10-4_16-59-14.png
    3.9 KB · Views: 661
Last edited:
  • Like
Likes symbolipoint, Imager and jedishrfu
  • #5
OCR said:
If you would like, just highlight the post number, then right click on the post number, then click copy...
No need to highlight it. Just use "copy link location".
 
  • Like
Likes Imager
  • #6
Thank you to all, just what I needed!
 
  • #8
Try it with a different post than the first one.
 
  • #11
This way, too...

upload_2018-10-5_2-22-35.png


.
 

Attachments

  • upload_2018-10-5_2-22-35.png
    upload_2018-10-5_2-22-35.png
    7.2 KB · Views: 579
  • #12
Lol, OK, disregard posts #4, #7, #9, #10, and #11 ... .:oops:

You can left click the post number, hold the button down, and drag and drop the number right in the reply box...

I just did that with the above post numbers... try it.Matterwave's post #25 done the same way... .
:sorry: ... Carry on.

.
 
  • Like
Likes Tom.G
  • #13
  • #14
symbolipoint said:
...an trying to pick Bernhardt's post #102...
Did you try the drag and drop method ?

#102

.
 

FAQ: How do you create a link to a specific post?

How can I create a link to a specific post?

To create a link to a specific post, you will need to find the URL or permalink for that post. This is typically located at the top of the post or in the post's settings. Once you have the URL, you can use the HTML <a> tag to create a link. Simply add the URL as the value for the href attribute, and add the post title or other relevant text between the opening and closing <a> tags.

Can I create a link to a specific post on a different website?

Yes, you can create a link to a specific post on a different website. However, you will need to know the URL for the post on that website. Once you have the URL, you can use the <a> tag as mentioned in the previous answer to create the link.

How do I ensure that the link to the specific post will open in a new tab or window?

To make sure that the link to the specific post will open in a new tab or window, you can add the target="_blank" attribute to your <a> tag. This will open the link in a new tab or window, depending on the user's browser settings.

Can I create a link to a specific post on a different page on my own website?

Yes, you can create a link to a specific post on a different page on your own website. To do this, you will need to know the URL for the post on your website. Then, you can use the <a> tag to create the link and include the full URL as the value for the href attribute.

Is it possible to create a link to a specific post without knowing the URL?

No, it is not possible to create a link to a specific post without knowing the URL. The URL is necessary to specify the destination of the link. However, if you are creating a link to a post on your own website, you can use relative URLs instead of the full URL. This means that you can use the path to the post from your current page instead of the full URL.

Similar threads

I Weak principle of equivalence (Galileo, Newton)
Replies
5
Views
992
A Why is the Principle of Equivalence Necessary for GTR?
Replies
9
Views
1K
I Gravitational wave interactions and the equivalence principle
Replies
17
Views
2K
I The Equivalence Principle as a Starting point of GR
2
Replies
44
Views
5K
I How Does Energy Source Curvature? Exploring the EEP
Replies
4
Views
2K
I Equivalence principle question
2
Replies
36
Views
3K
A Theories that respect one form of the equivalence principle but violate another
Replies
29
Views
4K
I Einstein's Equivalence Principle: Freely Falling Local Frames
Replies
4
Views
1K
B Sum up Questions for Gravitational Waves & Weighing Scales
Replies
5
Views
1K
I Evidence of Strong Equivalence Principle Violations?
Replies
3
Views
2K

Hot Threads

Recent Insights

Back
Top