# Secret of Gravity

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1. Jun 17, 2015

### tanmay

I have a doubts related to gravity
How do this gravity come into existence?
What is a cause of gravity?
Why two masses are attracted due to gravity?

2. Jun 17, 2015

### DEvens

The best idea we have for the "how" of gravity right now is general relativity. It has been explained in colorful language like so. Matter shapes space-time, and space-time tells matter how to move. But there is really a lot of very pretty mathematics to understand the details. And that math has confronted the experimental data and done exceptionally well. With some tantalizing things like dark matter that we are not entirely sure we understand completely.

Asking "why" in science is a troublesome thing. It is difficult to know what sort of answer would be satisfactory.

Science generally works like so. You start with observations. Sometimes they start out pretty disorganized. You get an idea, maybe little better than a guess, how these things work. Then you use that idea to design tests and predict the outcomes. Then you compare the results to your predictions. Then you update your idea and make it better. Then you use the better idea to design better tests. And you cycle this. Better tests followed by better ideas, and more improvement to tests, and more improvement to ideas.

Insert a great deal of human effort with the usual degree of human failings, weirdness, and brilliance. And people slagging each other off at conferences and on web sites. And crazy ideas (that may be right or wrong) promoted by people with an axe to grind. And brilliant teachers who finally make us understand.

Eventually the idea becomes better and better at predicting test results. Or you decide the idea is hopeless and get rid of it to replace it with a completely different idea.

The key feature is, you keep updating your ideas. You keep correcting them by comparing to observation. And at any given point you have the best idea (or possibly a few competing best ideas) that explain the "how" of everything that has been observed.

Always these ideas will have some assumptions. Another word used frequently is "postulate." These are the things that are taken for granted and not explained by the theory. These are the foundations on which the theory is built. We have comfort in these foundations because they have been tested many times and worked. But, at the moment, we don't have any way to look behind this particular curtain.

This comes back to your question. What sort of observation could you make to test a "why" sort of idea? Beyond a "we think this because it works" sort of answer, it is really hard to provide an answer to "why."

3. Jun 17, 2015