What is topic number 9 on eurekalert.org and why is it important?

  • Thread starter tgin_polish
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In summary, the individual is struggling to write a report on topic number 9, quantum gravity, and is looking for some guidance or insight. They are recommended to read books by Brian Greene and Lee Smolin for a better understanding of the topic, which involves the theories of general relativity and quantum mechanics. The person offering help explains that these theories do not mix well and often lead to nonsensical results, hence the need for a new theory such as string theory. However, they caution that the information provided is not precise and the field is still a work in progress.
  • #1
tgin_polish
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Gravity - Do you know it?

I am required by my physics class to write a report concerning topic number 9 on the following site
http://www.eurekalert.org/features/doe/2002-02/ddoe-1pq061502.php

I am having a great deal a difficulty even starting to write on the topic. I am not what you would classify a bright physics student. Any incite into this topic would be greatly appreciated.
 
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  • #2
Google search for quantum gravity.

Warning: An indepth explanation is *hard* and not understood even by the best physicists in the world. I recommend you pick up Brian Greene's book the elegant universe, and Lee Smolins 3 roads to quantum gravity. They are written for the Layman, so it should be approachable especially if you have some undergrad level of understanding of quantum mechanics and special relativity.
 
  • #3
C'mon fellas. I know there are some smart people on these boards. I need to write 10 pages on this topic. For the love of God please help me.
 
  • #4
I don't know if I'm smart or not, but I do know a little something about what you're asking =)

And I'm telling you, get those books and do a little self research, b/c the answers you're looking for are not found in a paragraph on an internet forum.

Why don't you ask a very specific question, b/c frankly its akin to asking someone 'what's the history of Europe like, someone has got to know a little something?'

But here's a paragraph all the same.

General relativity is Einstein's theory of gravitation. It involves the geometrization of space and time and making that the primary source term for generating gravity, its a very large scale force. Quantum mechanics + special relativity, is the study of the very small (the remaining 3 forces in nature). Both theories are well tested experimentally in their own domains of validity. Mathematically however, they don't mix well. In part b/c GR involves compact, more or less continuous geometry, and quantum mechanics discrete 'fuzziness' and potentially nonlocal effects. When you mix them in a naive quantum version of gravity, you get a theory that involves gravitons that output pathological infinities (read nonsense). In a sense, the theory breaks down. So we expect something 'new' to emerge, in much the same way that Fermi theory of weak decay broke down and led to modern Electroweak theory.

String theory is one attempt to get past the problem, essentialy removing the point particle as a fundamental unit, and instead postulating a 1dimensional or larger 'brane' to replace it. Geometry in string theory, then is an emergent 'field' just like all others, and not truly fundamental. Particles and forces are interpreted as excitations of various 'string' modes of oscillation.

Please understand, that at the level I am talking at, these things are very unprecise and in many ways WRONG. But that's the way things are, in a field that as yet is still work in progress.
 
  • #5
Thank you much Haelfix.
 

1. What is gravity?

Gravity is the force by which a planet or other body draws objects toward its center. The force of gravity keeps all of the planets in orbit around the sun. Earth's gravity is what keeps you on the ground and what makes things fall.

2. How does gravity work?

Gravity works by the principle of mass attracting other mass. The larger an object's mass, the more gravity it has. So, objects with more mass produce a stronger gravitational pull, making them attract other objects more strongly. This is why the Earth has a stronger gravitational pull than, say, a marble.

3. Who discovered gravity?

The concept of gravity has been known since ancient times, but it was Sir Isaac Newton who first described it in mathematical terms in his law of universal gravitation. Later, Albert Einstein's theory of general relativity provided a more accurate explanation of gravity.

4. Can gravity be stopped or turned off?

No, gravity is a fundamental force of nature and cannot be turned off or stopped. It is always present and affects all objects that have mass.

5. How does gravity affect space and time?

Einstein's theory of general relativity states that gravity warps and bends the fabric of space-time. This means that the presence of massive objects, like planets or stars, creates a curvature in space-time, causing other objects to follow a curved path around them. This is what we experience as gravity.

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