So, anti-gravity...

[Firoth]

As far as my understanding goes, the idea behind making a craft with anti-gravity abilities is that it would be completely free from the effects of gravity. Allowing it to simply move or be moved through space under its own power, without pull from a planet or any other mass.

Now, the Earth moves through space at about 67,000 miles per hour and rotates at about 1,000 miles per hour.

So, assuming my understanding of what anti-gravity is supposed to be, wouldn't anything that was suddenly free from the effects of gravity go hurtling away from us? Or, depending on what side of the Earth it was on at activation, slam into the ground?

 

[DefunctTheory]

No. Even an object that was suddenly exempt from gravity would still be locked into whatever trajectory gravity (And other forces) had forced it into. So it would still be spinning around the planet at X miles per hour, the sun at Y miles per hour, the center of the galaxy at Z miles per hour, and so forth.

Eventually, given time, forces besides gravity will begin to exert themselves more and more, and the object will get free. But it's not some sudden change or anything.

 

[Zontar]

Anti gravity is a ludicrous idea that defies the laws of physics.

Now, creating a magnetic field that repulses that of the Earth to push itself into the air like a submarine rising in water and bring you anywhere until you reach the edge of the magnetosphere (which goes up about 90,000 km), now that is something different.

 

[Firoth]

An object in motion stays in motion, etc. Yeah, I didn't take that into account. But, still, wouldn't the sudden wind resistance to it moving purely on its own momentum cause it to slow rapidly as the Earth keeps moving?

 

[Silentpony_v1legacy]

No damn it. When you use an anti-gravity engine, you roll 3d6 and try to get under your Toughness. If you don't, you're removed from the earth as a casualty and everyone around you has to take a Pinning test.

Did no one pay attention in AP Physics in high school?!

 

[Firoth]

No damn it. When you use an anti-gravity engine, you roll 3d6 and try to get under your Toughness. If you don't, you're removed from the earth as a casualty and everyone around you has to take a Pinning test.

Did no one pay attention in AP Physics in high school?!

I saw the last line of your post first, and got halfway through "Toughness" before I realized you weren't being serious. X(

 

[DefunctTheory]

An object in motion stays in motion, etc. Yeah, I didn't take that into account. But, still, wouldn't the sudden wind resistance to it moving purely on its own momentum cause it to slow rapidly as the Earth keeps moving?

Yes. The forces that are exerted on an object like friction (From solids, liquids, or gases) would eventually cause the object to get thrown out of the gravity wells it was previously anchored to. But because most of those forces are fairly trivial compared to gravity, it would take some time for them to overpower it's 'beginning' velocity. How long would depend on the physical parameters of the object, and whatever force it itself in generating, but it wouldn't be instantaneous.

 

[Firoth]

Yes. The forces that are exerted on an object like friction (From solids, liquids, or gases) would eventually cause the object to get thrown out of the gravity wells it was previously anchored to.

Ok, so because the force of the gravity of the Earth is so comparatively greater than the others it would suddenly face, those other forces would not have a great enough effect. This raises another question, wouldn't the object still be torn apart by these new forces? Particularly wind resistance, since this object would instantly be hitting something far greater than its terminal velocity.

An example, of sorts: A person sky-diving is facing wind resistance falling at a terminal velocity of about 118mph. Although they're also technically moving through space at a much greater speed, so much as "everything" around them is moving through space at the same speed, being pulled through space by Earth and its gravity. Even at a 1% decrease in speed from 67,000mph would be a large shift. The speed of sound is 767mph for comparison. That's a considerable force, I mean, I know we're talking about a human body in this example, but friction is no joke on any material at those speeds. Consider space shuttles hitting the atmosphere and catching fire.

I'm having a hard time keeping my thoughts in line here or knowing if I'm even making sense anymore (I mean, I know what I'm trying to say), but I'm trying to end up at a comparison of a sudden shift in speed akin to hitting water at a high velocity.

 

[FalloutJack]

Anti gravity is a ludicrous idea that defies the laws of physics.

As we know them. Of course, some contend that gravity is technically one of the weaker forces, and your milege may vary on that account. The idea behind it would be the cancellation of waves to some degree. We don't know how to just blatantly do that to everything, but blocking waves at all is not an unknown thing. You can Arthur C. Clarke that one, for sure, but I won't write out 'Impossible' out of hand.

So, assuming my understanding of what anti-gravity is supposed to be, wouldn't anything that was suddenly free from the effects of gravity go hurtling away from us? Or, depending on what side of the Earth it was on at activation, slam into the ground?

This wouldn't be an uncontrolled cancellation of forces if you wanna keep your test model. The scientific method doesn't go from zero to holy shit, usually. They'd work it from the daintiest, most miniscule level of power first because someone would have considered your line of thinking...since this would obviously involve a number of physicists. Your line of thinking would be for vehicles designed to fly off into space. Anything rated for in-atmo would be weak and regulated and probably end up like Back to the Future: Part II. Your line of thinking would be useful for easy departure from the planet to go off into outer space by design. They'd just let the Earth fall away from them. Clever.

 

[Mr. Popplewick]

As far as my understanding goes, the idea behind making a craft with anti-gravity abilities is that it would be completely free from the effects of gravity. Allowing it to simply move or be moved through space under its own power, without pull from a planet or any other mass.

That's not entirely wrong, but you're forgetting something, and that's the simple fact that whatever is on the Earth before you magically turn off the gravity, is ALSO moving along at the exact same clip. For the rest, see AccursedTheory

Now, the Earth moves through space at about 67,000 miles per hour and rotates at about 1,000 miles per hour.

So, assuming my understanding of what anti-gravity is supposed to be, wouldn't anything that was suddenly free from the effects of gravity go hurtling away from us? Or, depending on what side of the Earth it was on at activation, slam into the ground?

Anti-gravity would be a freaky and fucked up thing in ways that most people don't understand unless they're truly familiar with Relativity. Gravity, in the current formulation, is not a force, but a pseudoforce created as a result of the geometry of spacetime. That's spaceTIME. They're part of the same fabric, and gravity has an effect on both. Gravity, the result of mass/energy acting upon spacetime, and in turn being "guided" locally by the resulting geometry. The greater the mass, the greater the warping. Like this:

Imagine a block of spacetime, with a large star in it.

See how the clocks closer to the mass (deeper in the gravity well) move slower relative to those more distant clocks? There is no theoretical accounting for how you could achieve anti-gravity without also warping spacetime. Even in the most exotic theories involving negative energy densities, these only exist in extreme conditions such as the region within the static limit of a black hole.

But look, even if you had a magic wand that could turn off gravity for YOU, what would that mean? The least of your problems, I think, would be your relationship to the Earth. How about your place in the manifold of spacetime you call home? I think "turning off gravity" would be a similar proposition to "Leaving the universe".

Oh and in case you're thinking, "Wow, leaving the universe?! Cool!" I mean "...Through a sieve."

Anti gravity is a ludicrous idea that defies the laws of physics.

As we know them. Of course, some contend that gravity is technically one of the weaker forces, and your milege may vary on that account. The idea behind it would be the cancellation of waves to some degree. We don't know how to just blatantly do that to everything, but blocking waves at all is not an unknown thing. You can Arthur C. Clarke that one, for sure, but I won't write out 'Impossible' out of hand.

It would have nothing at all to do with waves, please don't bullshit. You're not wrong to write off nothing as impossible, but "Horrendously unlikely" is fair, or "Not without a pet black hole", or "Not survivable." As the impossible goes, FTL travel/Time Travel, Anti-Gravity, and Perpetual Motion are the BIG three that are very nearly totally ruled out by a theory that's been tested for a 100 years without showing anything like signs of being falsified.

Remember, the theory that says "anti-gravity is bullshit" is the same one that let us detect black holes merging.

 

[Mr. Popplewick]

Consider space shuttles hitting the atmosphere and catching fire.

Space objects don't catch fire when entering an atmosphere, the air around them does.

That simply isn't true, although "catch fire" isn't really the issue. The incredible heat causes the exposed outer skin to flash to a plasma, which is then blown away, and so on. The result is that you get a plasma sheathe (what we see as the "shooting star) composed of burning material from the falling object, burning atmosphere, and what amounts to a kind of slow, localized lightning blasting through the atmosphere.

In fact the reason we're not pummeled by debris all day, every day, is most of what hits us isn't massive or dense enough to survive the process; they burn up.

 

[Thaluikhain]

Yes. The forces that are exerted on an object like friction (From solids, liquids, or gases) would eventually cause the object to get thrown out of the gravity wells it was previously anchored to.

Ok, so because the force of the gravity of the Earth is so comparatively greater than the others it would suddenly face, those other forces would not have a great enough effect. This raises another question, wouldn't the object still be torn apart by these new forces? Particularly wind resistance, since this object would instantly be hitting something far greater than its terminal velocity.

Why?

If gravity doesn't affect it, it'd not be pulled to the centre of the Earth, yes. But there's plenty of ways already to avoid this...a hummingbird or helocopter can exert a force on the air around it to counter gravity, it's not immediately torn apart.

Now, if the thing was already in orbit, without gravity pulling it towards the Earth, it'd fly off on a tangent, yes.

 

[Firoth]

Why?

If gravity doesn't affect it, it'd not be pulled to the centre of the Earth, yes. But there's plenty of ways already to avoid this...a hummingbird or helocopter can exert a force on the air around it to counter gravity, it's not immediately torn apart.

Now, if the thing was already in orbit, without gravity pulling it towards the Earth, it'd fly off on a tangent, yes.

Because a helicopter is not actually nullifying the gravitational pull, just fighting it. The theory behind anti-gravity is that the object would exist outside the force of gravitational pull. The reason something that hovers needs so much power is to lift it's weight against the pull of gravity.

 

[Firoth]

Imagine a block of spacetime, with a large star in it.

Your image is borked, your argument is invalid! (jk, but I would like to see it)

Do you have anything to add or comment on for my later arguments/questions regarding deceleration and wind resistance?

 

[Thaluikhain]

Why?

If gravity doesn't affect it, it'd not be pulled to the centre of the Earth, yes. But there's plenty of ways already to avoid this...a hummingbird or helocopter can exert a force on the air around it to counter gravity, it's not immediately torn apart.

Now, if the thing was already in orbit, without gravity pulling it towards the Earth, it'd fly off on a tangent, yes.

Because a helicopter is not actually nullifying the gravitational pull, just fighting it. The theory behind anti-gravity is that the object would exist outside the force of gravitational pull. The reason something that hovers needs so much power is to lift it's weight against the pull of gravity.

Sure...so? Either way it is not being pulled to the Earth. How does this affect how much the wind affects it?

 

[Firoth]

Because a helicopter is not actually nullifying the gravitational pull, just fighting it. The theory behind anti-gravity is that the object would exist outside the force of gravitational pull. The reason something that hovers needs so much power is to lift it's weight against the pull of gravity.

Sure...so? Either way it is not being pulled to the Earth. How does this affect how much the wind affects it?

The reason it would effect the two differently is because with the helicopter, it's still being pulled along with the Earth and everything else effected by its gravity. Meaning all the air around the Earth and helicopter are still being pulled through space at the same speed. That's the reason we don't feel wind caused by the Earth moving through space or rotating, because it's all moving together. A truly anti-gravitational craft would exist outside that pull, therefor all the air still moving with the Earth would start exerting it's force on the craft since it's now moving at a separate and slower speed than literally everything around it, including the air.

 

[Thaluikhain]

The reason it would effect the two differently is because with the helicopter, it's still being pulled along with the Earth and everything else effected by its gravity. Meaning all the air around the Earth and helicopter are still being pulled through space at the same speed. That's the reason we don't feel wind caused by the Earth moving through space or rotating, because it's all moving together. A truly anti-gravitational craft would exist outside that pull

Not at all. It simply isn't being pulled towards the centre of the Earth. It's still moving the same as everything else.

therefor all the air still moving with the Earth would start exerting it's force on the craft since it's now moving at a separate and slower speed than literally everything around it, including the air.

Not true. The air et al would continue to act on it the same way it has always done, the same way it affects everything else. Being pulled towards the centre of the Earth (or not) doesn't affect changes to momentum due to the Earth's rotation.

The only way gravity makes things turn with the Earth is by helping them stick to the Earth, that is, by physically being in contact with the thing that is turning so it turns as well. Until you get beyond the atmosphere, you are still being held by the air which is moving with the planet.

 

[one squirrel]

An object on the surface of the earth that was suddenly no longer bound by gravitation would move towards the sky with a velocity of about 1.6 cm per second. Noticable, but not spectacular. It would just gently drift away, wind resistance doesn't Play a role at such low speeds.

Another thing: running an anti-gravitation engine would always consume more engergy than it would take to overcome gravitation conventionally. Otherwise we could just lift an object into the sky, then deactivate the engine and get potential energy out of nothing. That would contradict the 1st law of thermodynamics.

Edit: 0,016m are 1,6cm and not 1,6mm... stupid me