Bending of space and time, is it true?

[AshUchiha]

Wow, thanks it helped a lot. So the in the examples shown in the second video, I find Newton's theory more reasonable, as gravity acts on all objects with mass and energy at all times right?. Just one last question, is gravity a relative quantity??, for example let's assume a very big (such that all other celestial bodies are negligible in mass to that), is on the space. So all the objects would fall to it ? As that objects velocity and gravity is much higher compared to those. Really bugs me...

 

[phinds]

Wow, thanks it helped a lot. So the in the examples shown in the second video, I find Newton's theory more reasonable, as gravity acts on all objects with mass and energy at all times right?. Just one last question, is gravity a relative quantity??

Only in the sense that bigger masses have a stronger gravitation attraction, but "relative" is NOT a good description for gravity.

, for example let's assume a very big (such that all other celestial bodies are negligible in mass to that), is on the space. So all the objects would fall to it ? As that objects velocity and gravity is much higher compared to those. Really bugs me...

You can have a stable orbit around any size mass so things will not necessarily fall in.

Velocity is relative, so your statement about velocity doesn't make sense since you have not specified what it is that the large object has a high velocity relative to.

 

[wabbit]

Velocity is relative, so your statement about velocity doesn't make sense since you have not specified what it is that the large object has a high velocity relative to.

Actually if that big mass has a very high velocity compared to everything else, it will capture less: this means that other objects are likely to be above escape velocity relative to that big mass, so they do not fall in unless their path directly crosses that body.

 

[phinds]

Actually if that big mass has a very high velocity compared to everything else, it will capture less: this means that other objects are likely to be above escape velocity relative to that big mass, sobthey do not fall in unless their path ditectly crosses that body.

Good point.

 

[AshUchiha]

Wait phinds, Gravitation is equal to every object no matter their mass I guess (Ignoring Drag).Can you explain me how gravity isn't a "good" example for being relative quantity..? Also assuming that any object with minimum required mass would have it's own orbit , is wrong? just reference...And it's velocity is higher than any other object available in space

 

[Drakkith]

Wow, thanks it helped a lot. So the in the examples shown in the second video, I find Newton's theory more reasonable, as gravity acts on all objects with mass and energy at all times right?.

All objects have mass and energy, so yes.

Just one last question, is gravity a relative quantity??, for example let's assume a very big (such that all other celestial bodies are negligible in mass to that), is on the space. So all the objects would fall to it ?

All of the objects, including the very large one, are attracted towards the barycenter of the system.

As that objects velocity and gravity is much higher compared to those.

The velocity is only relevant for determining the orbital characteristics of the different objects. It has no effect on the strength of gravity.

 

[Drakkith]

Wait phinds, Gravitation is equal to every object no matter their mass I guess (Ignoring Drag)

A little more specificity is needed here, as 'gravitation' isn't a quantity, it is just the name of the fundamental interaction. Force and acceleration are quantities. The acceleration of two objects towards a much larger object are approximately equal, but the force between the objects is not. For example, the gravitational force between the Earth and myself is about 50% greater than the force between the Earth and my little sister. That's why she weighs less than me.

Also assuming that any object with minimum required mass would have it's own orbit , is wrong?

What 'minimum required mass'? There is no minimum.

 

[AshUchiha]

So Drakkith, if the can I conclude that, the more mass, the more Inertia and thus more Gravitation? and if it's gravity soo high that it attracts all the objects available in space and collide to each other to form one object/body. Is this possible ?, and be like it was at the very before at a very dense state.??

Big bang theory stated that at the very first the universe was very dense object right? So can it be like that again if such circumstances occur

 

[pvk21]

Creation of gravity lies in quantum mechanics.as I understood gravity can be created.particles(such as quark or electron)emit force carrying particles.this particles what make 4 fundamental forces.when particle with spin-2(also called as gravitons)interact with other graviton there is creation of gravitation force.well we can't really detect gravitons.but its what physicist believe that gravitation born from gravitons.

 

[Drakkith]

So Drakkith, if the can I conclude that, the more mass, the more Inertia and thus more Gravitation?

Sure.

and if it's gravity soo high that it attracts all the objects available in space and collide to each other to form one object/body. Is this possible ?

Not really. You've skipped an important step. You need to specify what all of those objects are doing. If they are moving at high enough velocities relative to this object, then they might simply be in a stable orbit. Gravity is not like the suction of a vacuum cleaner. If you were to replace the Sun with an equal mass black hole the planets would go right on orbiting just as they are now.

Big bang theory stated that at the very first the universe was very dense object right? So can it be like that again if such circumstances occur

Sure, but those circumstances are known as the 'Big Crunch' and requires that the universe be collapsing instead of expanding.

 

[Drakkith]

Creation of gravity lies in quantum mechanics.as I understood gravity can be created.particles(such as quark or electron)emit force carrying particles.this particles what make 4 fundamental forces.when particle with spin-2(also called as gravitons)interact with other graviton there is creation of gravitation force.well we can't really detect gravitons.but its what physicist believe that gravitation born from gravitons.

Uh, something like that.

 

[AshUchiha]

Yes, Drakkith, ofcourse it's mass is more then it's speed would be more eventually? I mean even it travels less faster, he would still be more speed than smaller object moving faster than it right?

Now you would say it isn't correctly specified, hmm.., put it this way

Suppose there is a small cricket ball , and our Earth. And let's put a specified time t.
So even if the cricket ball moves very fast, its speed is lesser than the Earth. Because Earth covers more distance than the cricket ball. And speed=Distance/Time. Time is constant for both of these object here, and Earth is traveling more distance due to its size. Thus traveling more speed than the ball. Right??

 

[phinds]

...And it's velocity is higher than any other object available in space

You keep SAYING that. You really need to get a grip on the fact that that is a meaningless statement. Velocity is only meaningful when you say what you are relating it to.

 

[phinds]

Suppose there is a small cricket ball , and our Earth. And let's put a specified time t.
So even if the cricket ball moves very fast, its speed is lesser than the Earth. Because Earth covers more distance than the cricket ball. And speed=Distance/Time. Time is constant for both of these object here, and Earth is traveling more distance due to its size. Thus traveling more speed than the ball. Right??

You have not said where the cricket ball is, and your way of describing it does NOT guarantee that the Earth is moving faster than the ball. You need to be more precise than you continue to be regarding speed.

If I throw a ball at 10 mph then as far as I am concerned, the ball is moving 10mph faster than the Earth because relative to me the center of the Earth is not moving. You really have to get past this lack of understanding of the relativity of velocity.

 

[AshUchiha]

Lol sorry phinds. But I said Speed not velocity. And there is a difference between Faster and speed right? Ball maybe faster than Earth's core but is less speed relative to Earth's Rotational Motion. Right?

 

[phinds]

Lol sorry phinds. But I said Speed not velocity. And there is a difference between Faster and speed right? Ball maybe faster than Earth's core but is less speed relative to Earth's Rotational Motion. Right?

No, if the ball is thrown in the direction of the rotation then the ball is going faster than the rotation. Once again, you have failed to really consider what you are saying relative to speed/velocity.

And "faster" is in the eye of the beholder, so again, you have to be totally clear about what you are specifying. If I say that I am running at 10mph and I throw a ball in front of me at 10mph, the to someone that I run past, the ball appears to be moving faster than me but to someone in a car going by at 20mph in the same direction I'm running, the ball is standing still and so has no speed and I'm moving backwards at a speed of 10mph

 

[AshUchiha]

Can you prove me how the ball's rotational speed is more than Earth's rotational speed.

 

[phinds]

Can you prove me how the ball's rotational speed is more than Earth's rotational speed.

I didn't say rotational speed, I said speed. If the surface of the Earth is moving at Xmph, relative to the moon say, and I throw a ball in the same direction at 10mph then the moon sees the ball moving at X+10mph.

 

[Drasberry]

Bending of space time under Einstein's gravitational theory is essentially the result of the 4 dimensional geometry used to describe observed interaction of planetary masses in orbit around the Sun. Gravity under this model is conceptually defined by a geodesic description of space/time vs the force model of Newton. It provides a more accurate model of the precession of Mercury's orbit than Newtonian physics can,which was the observable phenomenon that astronomers and physicists of the time were trying to develop an accurate mathematical theory for. The bending of light from distant stars passing near the Sun has been observed during solar eclipses too. In practice it has proved accurate enough for us to be able to launch a satellite on a 10 year mission covering millions of miles to rendevous with a comet and have it show up at exactly the right spot and time to land a probe.
There are known errors in Einstein's equations because the differential geometry system he used was itself not completed until 1926 by Elie Cartan, a decade after he first published. This is reflected in the separation of the electro-magnetic theory of special relativity from the general relativity theory of gravitation. A unified theory of general relativity in four dimensional Cartan geometry was not achieved until 2005 by the Welsh physicist Dr. Myron Evans, correcting the original errors in Einstein's model.

 

[Drakkith]

Yes, Drakkith, ofcourse it's mass is more then it's speed would be more eventually? I mean even it travels less faster, he would still be more speed than smaller object moving faster than it right?

I cannot understand what you're trying to say here.

Suppose there is a small cricket ball , and our Earth. And let's put a specified time t.
So even if the cricket ball moves very fast, its speed is lesser than the Earth. Because Earth covers more distance than the cricket ball. And speed=Distance/Time. Time is constant for both of these object here, and Earth is traveling more distance due to its size. Thus traveling more speed than the ball. Right??

Size has nothing to do with speed, and you cannot cover more distance with a slower speed.

Edit: Corrected a typo. Accidentally put "less distance with slower speed" instead of "more distance with slower speed".

 

[PeterDonis]

In GR the curvature of space-time is not zero inside the shell

No, that's not correct. Spacetime is flat inside the shell. The redshift of light going from inside to outside the shell is due to what happens to it when it passes through the shell (and then through the curved spacetime outside the shell). Light going from one point to another inside the shell has zero redshift, which is one manifestation of the flatness of spacetime inside the shell.

 

[PeterDonis]

the mass of the particles (reactants) is equal to the mass of the products

If you mean invariant mass, this is not correct; the invariant mass of the products in a nuclear reaction is less than the invariant mass of the reactants (meaning, in each case, the sum of the invariant masses of all the particles). You can check the numbers for typical reactions to confirm this.

If by "mass" you just mean the total energy of the system, yes, this is conserved, but it's just restating what you say in your next sentence.

 

[PeterDonis]

I find Newton's theory more reasonable

Since Newton's theory is just the low velocity, weak field limit of GR, then if Newton's theory is reasonable, so is GR.

 

[AshUchiha]

I didn't say rotational speed, I said speed. If the surface of the Earth is moving at Xmph, relative to the moon say, and I throw a ball in the same direction at 10mph then the moon sees the ball moving at X+10mph.

I see... but I was asking about the "rotational speed", and not by the a perceiver's eye, but say a machine or something which calculates it.

 

[Drakkith]

No, that's not correct. Spacetime is flat inside the shell. The redshift of light going from inside to outside the shell is due to what happens to it when it passes through the shell (and then through the curved spacetime outside the shell). Light going from one point to another inside the shell has zero redshift, which is one manifestation of the flatness of spacetime inside the shell.

I realize that no redshift takes place inside the shell, but I was under the impression that spacetime was still curved in some fashion compared to an observer far away from the shell. Would a clock placed inside the shell experience time dilation as viewed from this observer?

 

[AshUchiha]

Wrong. Size has nothing to do with speed, and you cannot cover less distance with a slower speed.

Let's put it this way. If the object is larger, it cover's more distance in the constant "t" rather than another object lesser in size relative to it. Both of their measurements are relative to Earth.
For ex.
Speed=Distance/time
For the object which is larger in size.
Speed=distance/time,
= d/t
Same for the smaller object
Speed=distance/time
d1/t

Now d> d1 because the "m" of the bigger object is greater than the m1 {The mass of smaller object}
The more mass the more size the more distance traveled in a specified time t , where both the objects compared are relative to anybody with mass

Can I conclude that?

 

[PeterDonis]

Would a clock placed inside the shell experience time dilation as viewed from this observer?

Yes, but that doesn't mean spacetime is curved inside the shell. It only means that spacetime has to be curved somewhere between the clock inside the shell and the observer far away. The curvature of the shell region plus the region outside the shell is sufficient to cause the observed time dilation.

The flatness of spacetime inside the shell is a simple consequence of the shell theorem, which holds in GR just as it does in Newtonian mechanics: a vacuum region of spacetime inside a spherically symmetric matter distribution must be flat.

 

[Drakkith]

Let's put it this way. If the object is larger, it cover's more distance in the constant "t" rather than another object lesser in size relative to it. Both of their measurements are relative to Earth.

I'm sorry you've lost me. What type of motion/speed are we talking about here? Rotational speed? Linear speed?

 

[AshUchiha]

I'm sorry you've lost me. What type of motion/speed are we talking about here? Rotational speed? Linear speed?

Rotational

 

[Drakkith]

Yes, but that doesn't mean spacetime is curved inside the shell. It only means that spacetime has to be curved somewhere between the clock inside the shell and the observer far away. The curvature of the shell region plus the region outside the shell is sufficient to cause the observed time dilation.

So if I place a clock inside this shell, wait a period of time, then retrieve this clock, it should read as having less time passed than a clock left behind far away from the shell. Now, what if I wait twice as long, according to the 2nd clock, before retrieving the 1st clock?