How?

[Freudian_Slit]

So, if it is not space nor spacetime, why do the rules of spacetime apply and as such we are pulled down to the greater mass, the earth, while living within the atmosphere?

I'm not certain I understand your question, but if you're referring to the fact that the apparent gravitational force due to the lithosphere of Earth is greater than that from the atmosphere, then that is because spacetime curvature (I'm being very general here) is responsive to the amount of stress-energy. There is much more mass in solid earth than in the air above and around us.

 

[Freudian_Slit]

Oh Gawd....intelligent men make me weak at the knees....


.....tumps over.

https://i.elitestatic.com/content/uploads/2015/10/15211825/50cc5b40-dbb8-0132-4633-0ebc4eccb42f.gif

 

[Colonel Hogan]

So, if it is not space nor spacetime, why do the rules of spacetime apply and as such we are pulled down to the greater mass, the earth, while living within the atmosphere?

You are never going to come close to "getting this" until you understand that as the mass of the earth is exerting a force on any "falling body of a separate mass" (be it a sky diver or a single molecule of atmospheric gas), that same "separate mass" is exerting a "force" on the earth attempting to pull it "up."

I don't know what the most sensitive machines are that could actually measure these forces. At some point, I suspect we would have to resort to mathematics to "see" the resulting effect as merely a product of a calculation. But I have no doubt that could be done.

You want to know what the force of atmospheric gas is on your little pink body? At sea level, the standard force is 14.7 pounds per square inch. Every square inch. And I guarantee you that is a complex interaction of gravitational weight of those molecules being pulled down by the earth upon you AND, (since our bodies aren't hermetically sealed containers), air and fluids (not to mention muscles and bone mass) pushing OUT.

Every single bit of it is a part of "spacetime." Has to be.

 

[doowdniw]

Mass.

I was going to say a good long Catholic one, but the Pope has already been mentioned. C of E perhaps?

 

[Fala]

We all know that he's building a spacecraft in his garage, don't we?

 

[Libsam]

I bet he is arguing with some flat earther.

 

[Liar]

So, if it is not space nor spacetime, why do the rules of spacetime apply and as such we are pulled down to the greater mass, the earth, while living within the atmosphere?

Let's oversimplify this:

1. Stuff is not spacetime. Spacetime is where stuff exists. All stuff. Including gasses like the Earth's atmosphere. Why do the rules of spacetime apply? Because the rules of spacetime always apply. To all the stuff.

2. It and you are both pulled towards the earth. But you are denser than air, so you sink to the bottom of the atmoshpere.


A book suggestion seems to be in order:
https://xkcd.com/thing-explainer/

 

[doowdniw]

Some people are more dense than others.

 

[Not Normal]

We all know that he's building a spacecraft in his garage, don't we?

Just like Salvage 1

I bet he is arguing with some flat earther.

I bet he IS a flat earther.

 

[Liar]

Some people are more dense than others.

No fat jokes, please. This is a science thread. Or something.

 

[richard_daily]

We all know that he's building a spacecraft in his garage, don't we?

Eternalfantasies... Idiot savant, or just a regular idiot?

 

[EternalFantasies]

I bet he is arguing with some flat earther.

Da man. Spot on. :thumspup:


It's someone I don't know but on my facebook for a different reason.

I don't want to argue, I didn't post anything, but want to give him a one liner only that would make him think of it differently.

He's quite convinced beyond doubt that the earth is flat. And he's a healthcare professional mind you. Educated...

 

[EternalFantasies]

Long day...

My thread here arose from someone asserting (on FB) that the earth is flat. Before I could formulate some reply, I wanted to ensure my understanding was very clear beyond the simple theories, but a logical imaginable one.

I'm not certain I understand your question, but if you're referring to the fact that the apparent gravitational force due to the lithosphere of Earth is greater than that from the atmosphere, then that is because spacetime curvature (I'm being very general here) is responsive to the amount of stress-energy. There is much more mass in solid earth than in the air above and around us.

I was replying to what you said about the atmosphere not being space nor spacetime, and was wondering if it means it is shielded from being part of the gravitational fold that the earth is in.

You are never going to come close to "getting this" until you understand that as the mass of the earth is exerting a force on any "falling body of a separate mass" (be it a sky diver or a single molecule of atmospheric gas), that same "separate mass" is exerting a "force" on the earth attempting to pull it "up."

I don't know what the most sensitive machines are that could actually measure these forces. At some point, I suspect we would have to resort to mathematics to "see" the resulting effect as merely a product of a calculation. But I have no doubt that could be done.

You want to know what the force of atmospheric gas is on your little pink body? At sea level, the standard force is 14.7 pounds per square inch. Every square inch. And I guarantee you that is a complex interaction of gravitational weight of those molecules being pulled down by the earth upon you AND, (since our bodies aren't hermetically sealed containers), air and fluids (not to mention muscles and bone mass) pushing OUT.

Every single bit of it is a part of "spacetime." Has to be.

Colonel your post actually gave me a lot of insight into this and did complement the resident doofus' strict scientific lingo in this.

It did so particularly the part of the actual falling object exerting a pull on the earth, no matter how small it is. I kinda knew that, but didn't visualize it before. What really filled much of the gap is you reminded me of atmospheric pressure here, at sea level, etc...

As such, my questions to both you & our resident doofus: Do we know for certain that the pull down force is exerted by AP alone? and, what is it that keeps the atmosphere from being yanked away by the larger exterior field?

 

[Freudian_Slit]

Long day...

My thread here arose from someone asserting (on FB) that the earth is flat. Before I could formulate some reply, I wanted to ensure my understanding was very clear beyond the simple theories, but a logical imaginable one.

Nobody cares.

I was replying to what you said about the atmosphere not being space nor spacetime, and was wondering if it means it is shielded from being part of the gravitational fold that the earth is in.

...

As such, my questions to both you & our resident doofus: Do we know for certain that the pull down force is exerted by AP alone? and, what is it that keeps the atmosphere from being yanked away by the larger exterior field?

In the GR picture of the universe, stress-energy is the stuff that inhabits spacetime. There's a very good question about the ontological status of spacetime itself: Is it a substance, a plenum, or does it exist only as spatio-temporal relations? You'll find physicists and philosophers who inhabit each position, even within the GR community. The most the theory itself will commit to is the fact of the metric, which is the object that contains information about the geometry of spacetime.

All massive objects gravitate; all mass affects the geometry of spacetime and all mass follows inertial trajectories in the absence of other forces. But as I mentioned, it is not only mass in the traditional sense, but all stress-energy that gravitates. Thus, Earth's atmosphere is held in an envelop around the surface by gravitation.

Air pressure is an ambient force, and it can be measured on all sides of an object in atmosphere. The downward "force" that you feel is actually the "normal" force - the ground or floor pushing against your feet in opposition to your body that would otherwise follow an inertial trajectory towards the center of the Earth.

What is this larger exterior field you're referring to?

 

[jaF0]

Point west and tell'em to start walking.

 

[EternalFantasies]

Nobody cares.

Apparently not. The clue was, the line wasn't directed at you.

In the GR picture of the universe, stress-energy is the stuff that inhabits spacetime. There's a very good question about the ontological status of spacetime itself: Is it a substance, a plenum, or does it exist only as spatio-temporal relations? You'll find physicists and philosophers who inhabit each position, even within the GR community. The most the theory itself will commit to is the fact of the metric, which is the object that contains information about the geometry of spacetime.

1. WTF is GR?

2. I think the answer to this question may confirm some theories, but also may disprove all current theories.

All massive objects gravitate; all mass affects the geometry of spacetime and all mass follows inertial trajectories in the absence of other forces. But as I mentioned, it is not only mass in the traditional sense, but all stress-energy that gravitates. Thus, Earth's atmosphere is held in an envelop around the surface by gravitation.

Stress-energy makes more sense than mass surely. Thanks for adding that; you lost me prior to it. But I certainly don't see what is meant by 'stress energy', it's source, etc. It seems more like a mathematical formula than anything else...

Air pressure is an ambient force, and it can be measured on all sides of an object in atmosphere. The downward "force" that you feel is actually the "normal" force - the ground or floor pushing against your feet in opposition to your body that would otherwise follow an inertial trajectory towards the center of the Earth.

I was saying how do we know the pull down force is "gravity" and not mere atmospheric pressure where the weight of the atmosphere is pushing things down.

What is this larger exterior field you're referring to?

The one exerted by larger masses than Earth like the Sun.

 

[Liar]

I was saying how do we know the pull down force is "gravity" and not mere atmospheric pressure where the weight of the atmosphere is pushing things down.

Because things don't float in a vacuum chamber.

 

[jomar]

All the National Geographics in all the grandmas attics around the world slow down the Earths rotation enough so that sunspots can efficiently recharge the gravity battery in the center of the earth.

 

[EternalFantasies]

Thanks guys.

Well he threw these at me.

https://www.youtube.com/watch?v=omrgKuy4Fj8

https://www.youtube.com/watch?v=T5MxX-rx_M0


and i'll be damned if I got the time, energy or patience to sit through them.

 

[BoyNextDoor]

Just say "OK smart guy, explain electricity."

 

[zipman]

Huge Sea Green

 

[JohnnySavage]

So far, nothing in this thread has explained why the Aussies don't fall off.

 

[4est_4est_Gump]

White men can't jump...


Just a couple of more inches and they would reach escape velocity.

 

[BoyNextDoor]

They are all holding cans of Foster's

 

[JohnnySavage]

You can't land a helicopter at the North Pole because the Earth is spinning 1,000 MPH and as soon as it touched down, it'd just take off again.