Gravity never zero

**Robittybob1** · 02-28-12, 08:23 PM

@ OnlyMe - thanks for replying and with such understanding too! I think you know your stuff very well, but you still could see the complication of acceleration that can't be measured, and the feeling of acceleration when standing still. It has left me wondering how to comprehend this?
An objects gravitational mass and inertial mass are the same. The force of one is called weight (stationary) and the other "force” calculated from Mass times acceleration.
But mass times acceleration only works when the force can overcome friction on a frictionless surface, otherwise it will show that the force will be greater that M*A.
Surfaces on which objects are resting are providing more "friction" than the G force can muster. (Sometimes very slow movements are possible - e.g. landmasses sinking, or the tilting of the Leaning Tower of Pizza.)

But gravity never gives up! It is always "forcing away", where as other forces are relatively temporary. (We push for a while and then give up.)

**hansda** · 02-29-12, 09:05 AM

Originally Posted by Robittybob1

@ OnlyMe - thanks for replying and with such understanding too! I think you know your stuff very well, but you still could see the complication of acceleration that can't be measured, and the feeling of acceleration when standing still. It has left me wondering how to comprehend this?
An objects gravitational mass and inertial mass are the same. The force of one is called weight (stationary) and the other "force” calculated from Mass times acceleration.
But mass times acceleration only works when the force can overcome friction on a frictionless surface, otherwise it will show that the force will be greater that M*A.
Surfaces on which objects are resting are providing more "friction" than the G force can muster. (Sometimes very slow movements are possible - e.g. landmasses sinking, or the tilting of the Leaning Tower of Pizza.)

But gravity never gives up! It is always "forcing away", where as other forces are relatively temporary. (We push for a while and then give up.)

Accelerometer is a device that measures acceleration . This acceleration can be horizontal or vertical . If it is vertical then the g value is considered . In free-fall , the accelerometer will measure the g value .

**hansda** · 02-29-12, 09:15 AM

Originally Posted by Robittybob1

It stands to follow if time is slowed in strong gravity fields time will be faster in low gravity fields. At the furthermost extremities if the Universe gravity would be virtually nil. Time will be a it's maximum rate.

I have no evidence for this other than logic.

You mean to say , as space expands ; time will be faster and as space shrinks time will be slower .

At the time of BigBang , there was no space . Do you think at the time of BigBang , there was no time also ?

**hansda** · 02-29-12, 09:20 AM

Originally Posted by Emil

A clue for gravity zero.
If we consider Earth as a closed system, then in the center of the Earth (we consider homogeneous Earth), the gravity is zero.

Going by your logic , the gravity will also be zero at the centre of the Sun , at the centre of all other Planets , at the centre of an atomic or sub-atomic mass .

**Emil** · 02-29-12, 04:10 PM

Originally Posted by hansda

Going by your logic , the gravity will also be zero at the centre of the Sun , at the centre of all other Planets , at the centre of an atomic or sub-atomic mass .

It was just a clue.
What do you think, if we consider our solar system a closed system, is in the space at least one point where gravity is zero?

**Robittybob1** · 02-29-12, 04:46 PM

Originally Posted by hansda

You mean to say , as space expands ; time will be faster and as space shrinks time will be slower .

At the time of BigBang , there was no space . Do you think at the time of BigBang , there was no time also ?

No time like the Big Bang! No time before the Big Bang or at least time stood still.

How would I know?

**hansda** · 03-01-12, 08:10 AM

Originally Posted by Emil

It was just a clue.
What do you think, if we consider our solar system a closed system, is in the space at least one point where gravity is zero?

I also have a feeling that , ' gravity can be zero ' somewhere in the Universe .

**hansda** · 03-01-12, 08:30 AM

Originally Posted by Robittybob1

No time like the Big Bang! No time before the Big Bang or at least time stood still.

How would I know?

If it is assumed that time and space both originated from BIGBANG ; then it also should be assumed that total mass and energy of our Universe also originated from BIGBANG .

In that case , total mass and energy of our universe was created at the BIGBANG . Consider this as statement 1 .

As per the basic Laws of Physics , mass and energy neither can be created nor can be destroyed . Consider this as statement 2 .

Compare statement 1 , with statement 2 . These two statements are contradicting . Both the statements can not be true . Only one of the statements has to be true .

I think , this is a very fundamental paradox of Physics .

**Robittybob1** · 03-01-12, 10:50 AM

Originally Posted by hansda

Accelerometer is a device that measures acceleration . This acceleration can be horizontal or vertical . If it is vertical then the g value is considered . In free-fall , the accelerometer will measure the g value .

I have never used an accelerometer but this part of the discussion originated when the Wiki article said that an accelerometer measuring acceleration of an object in free fall reads zero.
Have you got evidence this is different, have you checked it? Has anyone checked the acceleration due to gravity?

**hansda** · 03-01-12, 11:00 AM

Originally Posted by Robittybob1

I have never used an accelerometer but this part of the discussion originated when the Wiki article said that an accelerometer measuring acceleration of an object in free fall reads zero.
Have you got evidence this is different, have you checked it? Has anyone checked the acceleration due to gravity?

Wiki is right. Accelerometers are designed and calibrated that way . Accelerometers are mostly used in aircrafts . When the aircraft is in level flight accelerometer reads 'one' , meaning vertical speed of aircraft zero . So, g of gravity is balanced by lift force of aircraft .

**AlexG** · 03-01-12, 12:39 PM

I also have a feeling

Feelings? That's useful.

In that case , total mass and energy of our universe was created at the BIGBANG . Consider this as statement 1 .

As per the basic Laws of Physics , mass and energy neither can be created nor can be destroyed . Consider this as statement 2 .

Compare statement 1 , with statement 2 . These two statements are contradicting . Both the statements can not be true . Only one of the statements has to be true .

I think , this is a very fundamental paradox of Physics .
Today 09:10 AM

Conservation of energy does not apply to spatial expansion on the cosmological scale.

**Robittybob1** · 03-01-12, 02:07 PM

Originally Posted by AlexG

Feelings? That's useful.

Conservation of energy does not apply to spatial expansion on the cosmological scale.

How convenient!

**Robittybob1** · 03-01-12, 02:11 PM

Originally Posted by hansda

Wiki is right. Accelerometers are designed and calibrated that way . Accelerometers are mostly used in aircrafts . When the aircraft is in level flight accelerometer reads 'one' , meaning vertical speed of aircraft zero . So, g of gravity is balanced by lift force of aircraft .

So we are accelerating when we are standing still too then. Does the accelerometer read 1 when you hold it in your hand. Acceleration of Lift = g.

**origin** · 03-01-12, 03:37 PM

Originally Posted by Robittybob1

So we are accelerating when we are standing still too then. Does the accelerometer read 1 when you hold it in your hand. Acceleration of Lift = g.

Have you read the wiki on accelerometers. It will read zero in free fall and will read 1 g if it is in hand while standing on the ground.

Imagine it is a spring with a weight on it. Just standing on the ground the weight will stretch the spring. If the spring and weight are in free fall the spring will not be stretched. If you accelerate or deccelerate the sprign and weight it will stretch the spring. The sprind is caibrated so that the acceleration - actually the force can be measured.

**Robittybob1** · 03-01-12, 05:16 PM

Originally Posted by origin

Have you read the wiki on accelerometers. It will read zero in free fall and will read 1 g if it is in hand while standing on the ground.

Imagine it is a spring with a weight on it. Just standing on the ground the weight will stretch the spring. If the spring and weight are in free fall the spring will not be stretched. If you accelerate or deccelerate the sprign and weight it will stretch the spring. The sprind is caibrated so that the acceleration - actually the force can be measured.

I had looked at some part of and it threw me when I read about the accelerometer reading zero in free fall. Near the Earth's gravity will accelerate an object, yet the accelerometer will not pick up that acceleration. Now the fact that it reads zero is not that the object is not accelerating but a design limitation in the accelerometer.

Have I got that right?

**origin** · 03-01-12, 05:59 PM

Originally Posted by Robittybob1

I had looked at some part of and it threw me when I read about the accelerometer reading zero in free fall. Near the Earth's gravity will accelerate an object, yet the accelerometer will not pick up that acceleration. Now the fact that it reads zero is not that the object is not accelerating but a design limitation in the accelerometer.

Have I got that right?

If the frame is accelerating the accelerometer won't detect the acceleration. The easiest way to visualize this is to look at the accelerometer like a bathroom scale. If you are in an elevator in free fall and you were on the scale your weight would read zero. It would read greater than your weight when it hit bottom though.

**AlexG** · 03-01-12, 11:43 PM

Originally Posted by Robittybob1

How convenient!

Well bitty, if you actually read anything to do with cosmology, other than old copies of Cosmetology, you'd learn. But it's been a while, and learning anything hasn't happened yet.

**Robittybob1** · 03-02-12, 02:01 AM

Originally Posted by AlexG

Well bitty, if you actually read anything to do with cosmology, other than old copies of Cosmetology, you'd learn. But it's been a while, and learning anything hasn't happened yet.

Honestly I don't seem to have the time. I know you think you are an expert on Cosmology in fact if I see someone struggling I always get them to consult with you.
I accept you know what the current theory is.

**Emil** · 03-02-12, 03:40 AM

Energy conservation law does not apply in astrology !

**hansda** · 03-02-12, 09:24 AM

Originally Posted by AlexG

Feelings? That's useful.

Our Universe is also a closed system . There is no external interference to our Universe . In a closed system , at the centre ; the gravity is zero . So, this also can be said that , at the centre of our Universe ; gravity can be zero . If we believe that BigBang started from a point ; this point can be considered as the centre of our Universe .

The way there is an Event Horizon for Black-Hole . Similarly an Event Horizon for our Universe also can be considered at the farthest point of our universe , where the space is expanding . If time can be zero at the event-horizon of a black-hole , so gravity also can become zero at the event-horizon of our universe .

Conservation of energy does not apply to spatial expansion on the cosmological scale.

Why ? Does it mean that spatial expansion in cosmology happens without any energy ?

My basic argument was about creation . In Physics , it is believed that ; mass and energy neither can be created nor can be destroyed . If this is true ; then how it is also believed that mass and energy was created at the BIGBANG ?