# Phisicsts equations

1. Apr 21, 2013

I am wondering how physicists make such complex equations.I am not a physicist but a mid school student.
Can you give some brief outline of that?

2. Apr 21, 2013

### phinds

I do not understand the question. No one makes complex equations BECAUSE they are complex (and in fact, many equations in physics are NOT complex). Equations are made to describe reality as best we can and if that turns out to require a complex equation then that's just the way it is.

Physicists PREFER simple equations.

3. Apr 21, 2013

my question was
http://http://24.media.tumblr.com/tumblr_m28rlsC3HI1r32q38o1_500.jpg [Broken]
there is one of the pages of einsteins notebooks on attachments
I dont understand even a bit of it .That is why it is complex for me

#### Attached Files:

• ###### tn_gallery_1_173_6820.jpg
File size:
63.8 KB
Views:
153
Last edited by a moderator: May 6, 2017
4. Apr 21, 2013

### Dumte

What its the equation

5. Apr 21, 2013

### phinds

Well, if you are asking the mechanics of how they do the process of creating long equations, I can only say that they study math.

Like ANYTHING complex, you learn the simple stuff first and move on.

6. Apr 21, 2013

### phinds

That is, if you give an answer specific to THIS equation, it may not answer the question in general (although it IS likely to show the kind of process that is used)

7. Apr 21, 2013

8. Apr 21, 2013

### jambaugh

I found a Celtic song I really loved but of course not speaking Celtic I didn't understand a word of it. I finally looked it up and it turned out to be a recitation of the menu at a wedding feast. It was the language that seemed complex to me but was actually expressing simple facts.

The mathematics used in Einsteins equations are complex but it is a complex language to express and predict very precisely and unambiguously the implications of certain simple ideas. However compared to the common language (be it Celtic, French, English or Espranto) used to express the subtleties of marriage, love, food, and life, to express it in multiple ways so that the author can choose the way that best fits into the rhyme and meter of a song or poem, ... compared to that the mathematical language used in Einstein's notebooks is actually quite simple. It is just a foreign language and so like Egyptian hieroglyphs it may look more complex than it actually is.

If you are interested then by all means begin to study that language. Start with your school algebra and geometry.

9. Apr 21, 2013

Will I know all those when I graduate?

10. Apr 21, 2013

### jambaugh

The notebook page appears to be a derivation of Einstein's famous gravitation equations, or a part of them. The first line is the rate of change with respect to arbitrary coordinates of a quantity which derives from the stress energy components in space. The stress-energy's physical interpretation is the flow in space-time of the 4 components of energy and vector momentum.

The whole construct with respect to which he is taking a rate of change is a derivative quantity which must be independent of ones choice of coordinate systems for space and time. As such it must under the assumption that the physics doesn't care how we decide to draw coordinates must behave in a certain way.

He then, since the quantity is a product of component quantities expands the rates of change of the whole in terms of components and this gives a relationship between the geometry of the space-time and the presence and motion of matter and energy through it.

The two simple underlying physical principles that go into this derivation are:
General Covariance which is that the physics should not depend on the form we choose to express its component parts, and Einstein's famous Equivalence principle, which is that on a small enough scale so as not to observe any tidal effects, the effects of gravity are indistinguishable from the effects of the observer being accelerated.

11. Apr 21, 2013

### phinds

All of what? All of the equations in physics? No, I doubt it, unless you plan on MANY multiple degrees in various aspects of science.

12. Apr 21, 2013

No.I am talking about the way of creating these long and complicated ones like on einstein's notebook

13. Apr 21, 2013

### WannabeNewton

It's tensor calculus. If you want to write down stuff like that, say via problem sets in textbooks, then you have to build up your knowledge to get up to tensor calculus.

14. Apr 21, 2013