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Physics, Astronomy & Cosmology / Re: How does Hawking's radiation helps in figuring out "the theory of everything"?

« on: 08/05/2016 05:50:57 »

Stacy, Jeff is right, in this section you should make it clear, in new theories you can discuss what you like.

The question is asking about a theory of everything. A theory of everything is a new theory.

But it would be helpful to the op to make it clear, yes

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Physics, Astronomy & Cosmology / Re: How does Hawking's radiation helps in figuring out "the theory of everything"?

« on: 07/05/2016 11:11:50 »

it is said that Hawking's radiation theory is a link between quantum mechanics and general relativity

The physics of black holes accreting large amounts of matter (eg dust, planets and stars) is adequately described by the general theory of relativity.

However, general relativity generates infinities in the vicinity of black holes whenever attempts have been made to combine it with the quantum effects that govern photons and subatomic particles.

Hawking radiation is a proposed quantum mechanism which would allow black holes to slowly lose mass over time. So, in a very limited sense, it does combine quantum theory and general relativity.

We don't have any nearby black holes to study (fortunately for us!), so the details are still unresolved - for example some theorists suggest that there is a "firewall" around black holes, while others  disagree.
 
That still leaves the mechanism driving the polar jets emanating from black holes; mainstream physicists think they are some form of magnetohydrodynamic phenomena in the accretion disk (rather than dark matter outflows from within the black hole, which would violate general relativity).

Hawking's radiation ... can explain the theory of everything if it is developed further.

I would rather say that a theory of everything must incorporate Hawking radiation (or prove that it does not exist).
It must also resolve the debate about firewalls.
But most importantly, it must eliminate the many infinities around a black hole.

...Then we just need some way of testing it!

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Physics, Astronomy & Cosmology / Re: How does Hawking's radiation helps in figuring out "the theory of everything"?

« on: 07/05/2016 09:02:32 »

How can the understanding about empty space possibly help us to find the "theory of everything"?

Stacyjones is promoting a pet theory and not discussing mainstream science so don't be misled.

Stacy, Jeff is right, in this section you should make it clear, in new theories you can discuss what you like.

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Physics, Astronomy & Cosmology / Re: What is the weight felt by a person in freely falling lift ?

« on: 22/04/2016 16:26:41 »

Youngsters may never have experienced this, but anhyone ofer 50 has probably push-started a car at some time. Initially, you can feel the force you are applying to get the car moving, and you continue to provide a force to accelerate the car to the point where the engine starts. Suddenly, the car is moving at the same speed as you, and the push force is zero - you might even fall over.

In the lift situation, gravity is trying to accelerate you downwards but the floor is stopping you, just like the stationary car was opposing your push. As the lift accelerates, at some point the floor will be moving and accelerating at the rate that gravity demands, so once again you don't feel any force between you and the floor. 

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Physics, Astronomy & Cosmology / Re: What is the weight felt by a person in freely falling lift ?

« on: 22/04/2016 15:52:16 »

It's zero []  But I don't know how scientifically.Can someone explain this to me?

The weight of an object can be and is defined in two ways;

1) the force due to gravity on a body
2) the force required to hold a body at rest, i.e. to prevent it from falling, in a gravitational field.

Let's use the second definition since most of us think that way. When you're in free fall there are no forces other than gravity acting on your body. The force of gravity is not something you can feel when you're in free fall because it causes every single particle in your body to fall at exactly the same rate. In your frame of reference, i.e. the frame in free fall, there is, for all practical purposes, no gravitational field. In fact in general relativity there really isn't a gravitational field in a free fall frame. It's said to have been transformed away.

Was that helpful?  []

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Physics, Astronomy & Cosmology / Re: How does earth exert same acceleration on all kinds of objects ?

« on: 21/04/2016 06:06:25 »

Would it hurt to tell H.S. students that in Newtonian theory this is a coincidence; gravitational mass & inertial mass are equal for some as yet unknown reason: in G.R., inertial mass & gravitational mass are asserted to be equal, indistinguishable; they could handle that, eh?

Sure. Of course they can handle it. Never make the mistake that high school students aren't smart. When they ask questions like this it's to learn the answer. That means they're climbing out of a state of ignorance using their inherent intelligence.

By the way. This isn't true just in Newtonian mechanics but also in GR. In both theories its an experimental fact. It's the reason why particles move on geodesics.