What Is Gravity

[akyron]

In physic gravity is -9.8 meters/sec so they obviously found some way to measure it...

The numerical value for the acceleration of gravity is most accurately known as 9.8 m/s/s.

 

[akyron]

Particle and waves
Recently, scientists predicted that a gravitational field would exhibit wavelengths, similar to electromagnetic waves. Using highly sensitive instruments, experiments were made to verify that gravity is indeed a waveform of some sort.

To follow the wave-particle duality in Quantum Physics, it was also predicted that gravity consists of particles called gravitons. This is similar to the theory that light is not only a waveform, but also consists of particles called photons. Electrons are also viewed as both particles and waves.

Gravity Equations


So if gravity is a particle (gravitons) We can eventually figure out a way to manipulate it somehow. Sounds kind of dangerous to me. Whoops there goes the planet.

 

[goligoth]

Why arn't the planets pulled into one another?

Each one has it's own gravity and the sun is tugging on all of them.
I would think that the gravity of every planet would effect every other planet just a little...but enough to alter its course over time.

Is the sun really balancing us out that well?

And if gravity is the attraction force between two masses then isn't it really really bad to be sending out ships and satellites?
By doing so we are changing the mass of the earth and given enough launches and enough time our gravity will have changed just enough so that we would be pulled into the sun or (much scarier) thrown away from the sun.

Again these are questions that I posed to people like my physics teacher and I was either shrugged away or given a really stupid answer. :2brickwal

 

[tecoyah]

Why arn't the planets pulled into one another?

Each one has it's own gravity and the sun is tugging on all of them.
I would think that the gravity of every planet would effect every other planet just a little...but enough to alter its course over time.

Is the sun really balancing us out that well?

And if gravity is the attraction force between two masses then isn't it really really bad to be sending out ships and satellites?
By doing so we are changing the mass of the earth and given enough launches and enough time our gravity will have changed just enough so that we would be pulled into the sun or (much scarier) thrown away from the sun.

Again these are questions that I posed to people like my physics teacher and I was either shrugged away or given a really stupid answer. :2brickwal

1)the effects of gravity are in many ways balanced by momentum in an Orbit.
2)Yes...the Sun "Really Is" balancing us out that well...as it is the reason for said Orbital velocity in the first place.
3)the impact of Launching spacecraft is so very miniscule in comparison to the Masses involved, as to be insignificant, even in accumulation.

 

[paulmarkj]

Nobody knows what gravity is. I once asked a physicist how two bodies, say two bricks, 1 billion miles apart could attract each other. Surely, I said, there must be something coming out of one brick and travelling to the second brick to make it move. He there was, gravitons. I asked what gravitons were and he said nobody knew, but there must be something, so they called them gravitons!

Gravity is very weak, much weaker than magnetism.

The planets do affect each other, but are millions of miles apart, so the effect is small. Astronomers cannot see planets around other stars but have measured the effect of planets on the stars. As the planet moves around the star, it drags the star a little. However, the effect is so weak, it can only be measured when the planet is huge (many times the mass of Jupiter) and very close to the star. Such planets are thought to be rare because their mass and closeness to the star would normally drag them into the star. Therefore, it is thought, if over 100 such rare planets have been discovered, there must be many more 'ordinary' planets, more like those in our solar system.

Gravity is 9.8 m/s/s on Earth, but will vary depending on where you are.

Some physicists have suggested that gravity (being such a weak force) is really a strong force that has leaked out of a parallel universe that has maore dimensions than our universe. This is way beyond my understanding.

 

[Kandahar]

Why arn't the planets pulled into one another?

Because they're all attracted to the sun much more strongly than they are to each other.

Each one has it's own gravity and the sun is tugging on all of them.
I would think that the gravity of every planet would effect every other planet just a little...but enough to alter its course over time.

The orbital paths of the planets ARE changing slightly over time...but not enough to significantly change for billions of years.

Is the sun really balancing us out that well?

Yes, the planets have significant angular momentum to keep from spiraling into the sun or out of orbit for a very long time. If they didn't, they wouldn't be planets.

And if gravity is the attraction force between two masses then isn't it really really bad to be sending out ships and satellites? By doing so we are changing the mass of the earth and given enough launches and enough time our gravity will have changed just enough so that we would be pulled into the sun or (much scarier) thrown away from the sun.

The masses of spaceships are insignificant compared to the mass of the earth; no matter how many ships we build we wouldn't change the mass of the earth very much. Remember that every natural resource we use comes from the earth's crust, the entirety of which represents less than 0.1% of its total mass.

As for satellites, you can basically think of them as part of the earth since they are still in the vicinity and were made from materials that came from the earth. But aside from that, the same thing applies to them as applies for spaceships: their mass is miniscule.

 

[goligoth]

As for satellites, you can basically think of them as part of the earth since they are still in the vicinity and were made from materials that came from the earth. But aside from that, the same thing applies to them as applies for spaceships: their mass is miniscule.

Satelittes aren't part of the earth. they tug on earth's gravity so wouldn't they detract doubly from it's gravity...once for leaving, twice for tugging...again as many people redundantly pointed out it's not a lot but earth's rotation has remained 'unchanged' just as its mass has remained unchanged. Enough space ships and satelittes and in a couple million years of doing so...:boohoo: ... the people of "not tommorow but the day after" might want to look out! Plus on top of that no one can say that it won't happen just as no one can say it will. Hey gravity might be controled by a little magical leprechaun who does an uncany imitation of Jean Claude Van Dam...who's to say I'm wrong???? You tell me what controls gravity or what gravity is? Then maybe I'll doubt some of what the leprchaun says ( for those of you with no humor that was sarcasm)...











I'll never doubt what the leprechaun says.:mrgreen:

 

[Kandahar]

Satelittes aren't part of the earth.

Most satellites aren't much farther away from the center of the earth (proportionally) than you are.

they tug on earth's gravity so wouldn't they detract doubly from it's gravity...once for leaving, twice for tugging.

I'm not sure what you mean by this...every object in the universe tugs on earth's gravity, but the same mathematics applies to all of them.

..again as many people redundantly pointed out it's not a lot but earth's rotation has remained 'unchanged' just as its mass has remained unchanged. Enough space ships and satelittes and in a couple million years of doing so...:boohoo: ... the people of "not tommorow but the day after" might want to look out!

Very unlikely. We'd have to send ENORMOUS amounts of earth off in spaceships before there was any noticeable difference. And if the humans of such an era were making such huge numbers of spaceships, surely they'd be able to find the resources to build them on uninhabited worlds.

A single asteroid collision, like the one that killed the dinosaurs or the one that killed 95% of life in the Permian Era, almost certainly changed the mass of the earth more than all human interference has ever done.

 

[goligoth]

So common asteroids n' such have gravity too? Why wouldn't they just compress themselves into a giaganto asteroid? I mean if I was an asteroid I would want to be a giaganto asteroid...not to say that I'm not a giaganto asteroid :think: ...(more sarcasm)

I should probably ask the leprechaun, who's name I found out was Bill, why he does all this weird gravity stuff anyway. I'll get back to you with his answer when I have it.

 

[Kandahar]

So common asteroids n' such have gravity too?

Yes. All matter has gravity.

Why wouldn't they just compress themselves into a giaganto asteroid?

Generally they don't weigh very much (relative to other heavenly bodies) and therefore their gravity isn't strong enough to significantly alter one another. In fact, the main difference between an asteroid and a moon/planet is that the former is not spherical because its gravity is so weak.

 

[alphieb]

Scientist think gravity is bent space....but how???? What creates bent space?????

 

[goligoth]

Yes. All matter has gravity.



Generally they don't weigh very much (relative to other heavenly bodies) and therefore their gravity isn't strong enough to significantly alter one another. In fact, the main difference between an asteroid and a moon/planet is that the former is not spherical because its gravity is so weak.

What is anti-matter then?

And an asteroid belt has many asteroids. Millions upon millions of rocks floating around and playing cards. Eventually they create an alliance and turn into a planet. But why aren't all centers of mass drawn to a central point? they've had a really really long time to do so( so long of a time span that I don't even know how many years). If maybe not compacted into a central mass then they should at least show signs of moving to it...shouldn't they?

And for those of you interested...

Bill wouldn't reveal his secret to me...he says that this is a learning experience for me...

 

[tlranger]

Back in 60's we decided that basically the whole world sucks!!

Studies at Bradley show significant mass is captured each year by your gravity field, some minerals ect., but main componet is new(space) water(ice).

Peace T L Ranger

 

[Kandahar]

What is anti-matter then?

Antimatter is just like regular matter, but with the charges reversed. The positive-charged antiparticles (positrons) orbit the nucleus, and the negative-charged antiparticles (negatrons) are inside the nucleus, which is the opposite of regular matter.

But as far as gravity goes, matter and antimatter behave the same.

And an asteroid belt has many asteroids. Millions upon millions of rocks floating around and playing cards. Eventually they create an alliance and turn into a planet.

Occasionally that might happen, but it's rare.

Think of it this way: say you have a hundred racecars going around a track very fast. The other forces acting on them (i.e. an engine) are many many many times stronger than the gravitational forces between them. They rarely collide with each other, and when they do, it has nothing to do with gravity and more to do with the fact that they both happened to be heading for the same spot. Even if you let the cars go around the track for billions of years, they would never coalesce into a single object because of gravity.

But why aren't all centers of mass drawn to a central point? they've had a really really long time to do so( so long of a time span that I don't even know how many years). If maybe not compacted into a central mass then they should at least show signs of moving to it...shouldn't they?

If they weren't being acted on by any other forces, this might be the case. But the asteroids are all orbiting the sun just like the planets are. And their momentum and gravity toward the sun is much stronger than toward each other. It's the same reason that all of the planets don't combine into an uber-planet: the sun keeps them occupied orbiting it, so they never really impact each other's gravity enough to alter each other's shape.

 

[Kandahar]

Scientist think gravity is bent space....but how???? What creates bent space?????

That's a very good question that science does not yet have an answer for.

 

[The Real McCoy]

Antimatter is just like regular matter, but with the charges reversed. The positive-charged antiparticles (positrons) orbit the nucleus, and the negative-charged antiparticles (negatrons) are inside the nucleus, which is the opposite of regular matter.

But as far as gravity goes, matter and antimatter behave the same.

Which brings up another interesting topic: dark matter.

While normal matter & anti-matter share the same gravitational properties, the mysterious dark matter produces a sort of anti-gravity which shapes the grander structures in the universe.

Dark matter has yet to be directly observed but it's visible effects are profound. Our own galaxy is comprised of mostly dark matter, some astronomers estimate that over 90% of the mass of our galaxy is in the form of dark-matter.

 

[Kandahar]

Which brings up another interesting topic: dark matter.

While normal matter & anti-matter share the same gravitational properties, the mysterious dark matter produces a sort of anti-gravity which shapes the grander structures in the universe.

Dark matter has yet to be directly observed but it's visible effects are profound. Our own galaxy is comprised of mostly dark matter, some astronomers estimate that over 90% of the mass of our galaxy is in the form of dark-matter.

Actually it's dark ENERGY that is similar to an anti-gravity force. Dark matter is currently defined by its gravity; it is only observed by the fact that there doesn't seem to be enough regular matter in the universe to cause it to hold together under gravity as well as it has.

You're right that dark matter comprises most of the mass of our galaxy. It's very weird and hopefully scientists will have some understanding of what it is by the end of this decade.

 

[goligoth]

You said that asteroids and such are held more firmly by the sun then being attracted into one another. What holds the suns in rotation and keeps them from being pulled to one another?

I haven't heard anything about that dark energy stuff...is that what our scientists are calling black holes or are those still undefined?

 

[The Real McCoy]

You said that asteroids and such are held more firmly by the sun then being attracted into one another. What holds the suns in rotation and keeps them from being pulled to one another?

I don't quite understand your question... If you're asking what keeps the sun and other stars in orbit then the answer would be the super-massive black hole at the center of our galaxy known as Sagitarius A. It has a mass of over 2 and a half million times that of the sun.

I haven't heard anything about that dark energy stuff...is that what our scientists are calling black holes or are those still undefined?

http://en.wikipedia.org/wiki/Dark_matter

http://en.wikipedia.org/wiki/Dark_energy

Those links explain the 2 topics much better than I can.

Black holes are different. While black holes may (and most likely do) contain dark matter/energy, black holes are singularities, normal matter (remnants of a star) gravitationally condensed down to a single point with no dimensions. Since more mass = more gravity, the insane amount of mass in black holes creates an insane amount of gravity and at a certain point - the event horizon (http://en.wikipedia.org/wiki/Event_horizon) - not even light can escape the forces of a black hole's gravity.

There's much more to black holes, particularly concerning the warping of space and time due to the gravitational effects but my knowledge of Einstein's theory of relativity is limited.

 

[goligoth]

If light, mass, and even time can not escape the event horizon then how are we able to measure black holes? How can we have any viable guess?

Thank you for the dark energy dark matter links they're informative.

 

[dragonslayer]

Einstein said that gravity is the result of objects being distorted in a thing called, "space-time" with the largest distortions occuring with objects of great mass.

That's about all I know...lol

lol without Gravity things would be grave. We would be floating in space and have to use hooks on our feet to stay on earth.

 

[The Real McCoy]

lol without Gravity things would be grave. We would be floating in space and have to use hooks on our feet to stay on earth.

...and Earth would quickly wander into/away from the sun, destroying all life in either case.

 

[The Real McCoy]

If light, mass, and even time can not escape the event horizon then how are we able to measure black holes? How can we have any viable guess?

Thank you for the dark energy dark matter links they're informative.

Black holes (like dark matter) cannot be observed directly but their profound effects on other, nearby heavenly bodies can be seen. There are equations that calculate how massive a star has to be for it's gravity to sufficiently collapse itself into a black hole (I think it's something like more than 3 times the mass of the sun.) Also, black holes are most easily detected by gas/dust swirling into them. Before this matter reaches the event horizon, it speeds up and therefore heats up to extreme temperatures, ejecting X-Ray bursts which can be obeserved from Earth (actually from above the Earth because X-Rays don't penetrate our atmosphere.)

 

[Thinker]

So common asteroids n' such have gravity too? Why wouldn't they just compress themselves into a giaganto asteroid?

In the absence of other forces, self gravity would tend to make collections of
smaller bodies combine into larger ones; that's how stars and planets form.

In the case of the solar system's asteriod belt, there are other effects that act
against this, the most significant being Jupiter's gravity. Gravitational forces
from the combination of Jupiter and the Sun are large enough to keep stirring
things and prevent the formation of another planet between Mars and Jupiter.

 

[goligoth]

In the absence of other forces, self gravity would tend to make collections of
smaller bodies combine into larger ones; that's how stars and planets form.

In the case of the solar system's asteriod belt, there are other effects that act
against this, the most significant being Jupiter's gravity. Gravitational forces
from the combination of Jupiter and the Sun are large enough to keep stirring
things and prevent the formation of another planet between Mars and Jupiter.

Well why doesn't the sun and jupiter pull together?

Two big things each pulling on the other makes for some good attraction...