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Old 08-17-2012, 09:17 PM
 
Location: Chesterfield,Virginia
4,919 posts, read 4,225,777 times
Reputation: 2639

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I think that I have outdone myself on dumb questions and stupid scenarios here!

(My last question dealt with the sky stairway)

This months dumb question and stupid scenario is: The earth rotates at or around 1,000 mph, correct?

Now, let's say that I invented a machine that when activated, would nullify gravity.

The Dumb Questions .. of which there are three:

1) If I were to take my 'machine' outside and flipped the anti gravity switch .. would the machine Rocket itself into outer space?

2) If it were to Rocket into space .. at what speed would it do so?

3) Now for a worst case scenario, (and the reason for the 1,000 mph rotation mentioned above) .. If the anti gravity machine just hovered, slightly above the terrain when activated .. wouldn't those skyscrapers and mountains .. rushing at you at 1,000 mph present a problem?

I can assure you of one thing .. whichever scenario happens to be the correct one .. I wont be 'sitting' in the machine when the switch is flipped!

I Warned you about the stupid questions part!

Last edited by MrClose; 08-17-2012 at 09:33 PM..
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Old 08-17-2012, 10:08 PM
 
28,673 posts, read 41,214,087 times
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#3 If that were the case you would want to stop jumping off the ground.
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Old 08-17-2012, 10:51 PM
 
Location: Chesterfield,Virginia
4,919 posts, read 4,225,777 times
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I could always 'schlep' my machine to the North or South Pole .. unless the following story turns out to be closer to the truth!

One of my favorite Sci Fi writers and a Professor of biochemistry, Issac Asimov did a short story (that he almost called dirty pool but didn't) that dealt with something like this.

Quote:
The Billard Ball is the story of a journalist's recollection of the events surrounding the discovery of an anti-gravity device in the mid-21st century.

Heavy with physics theory, the story describes the relationship between the creator of the device, the billionaire inventor Edward Bloom, and his former classmate James Priss, a Nobel Prize-winning theoretical physicist who had discovered most of the theory that made the device possible.

The men are expert billiards players and bitter rivals. Challenged to execute a shot on a table which is equipped with the device, Priss sends a ball on a complicated trajectory which finishes when it enters the device's field.

At that point the ball vanishes and Bloom collapses, dead. There is a mysterious hole drilled completely through his chest.

Central to the story is the concept of a pure anti-gravity machine that turns out to be a perpetual motion machine of the 1st order.

Energy can be freely created in a volume of space time which is pulled 'flat' as defined within the Theory of Relativity as determined by Einstein.

However, this field possesses remarkable properties, which are the centerpiece of the story: any object which enters the field is reduced to zero mass, and hence must assume the speed of light.

There is also the unprovable speculation as to whether Priss knew, from his own theory and the nature of the blue glow produced by the field (possibly due to Cherenkov radiation), what would happen, and if he then directed the ball in such a way as to kill Bloom.

Asimov himself had some reservations about the name of the story, and noted that his friend Frederik Pohl's suggested title of "Dirty Pool" was far better than his own. The story retains its title despite the feeling of its author, as he preferred to remain consistent.
Neat Huh?
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Old 08-17-2012, 11:39 PM
 
Location: Chesterfield,Virginia
4,919 posts, read 4,225,777 times
Reputation: 2639
For a fun read .. I found Asimov's short story The Billiard Ball .. in it's entirety, on line .. Here: The Billiard Ball - Asimov's Mysteries
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Old 08-18-2012, 08:42 AM
 
Location: Seattle, Washington
3,733 posts, read 6,705,860 times
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#3 I think you would just be kind of "pulled along" with the Earth, rather than staying stationary. The Earth is moving in multiple directions at once. It is spinning on its axis, it is also moving on its orbital path around the sun, it wobbles slightly, it is moving with the sun in its orbital path around the galaxy.... As someone above said, you had better stop jumping off the ground if you fear moving out of place (in relation to the ground beneath you) when you aren't physically attached to it.

Last edited by cjg5; 08-18-2012 at 09:10 AM..
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Old 08-18-2012, 09:03 AM
 
Location: Westwood, MA
3,829 posts, read 4,944,987 times
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Quote:
Originally Posted by MrClose View Post
I think that I have outdone myself on dumb questions and stupid scenarios here!

(My last question dealt with the sky stairway)

This months dumb question and stupid scenario is: The earth rotates at or around 1,000 mph, correct?

Now, let's say that I invented a machine that when activated, would nullify gravity.

The Dumb Questions .. of which there are three:

1) If I were to take my 'machine' outside and flipped the anti gravity switch .. would the machine Rocket itself into outer space?

2) If it were to Rocket into space .. at what speed would it do so?

3) Now for a worst case scenario, (and the reason for the 1,000 mph rotation mentioned above) .. If the anti gravity machine just hovered, slightly above the terrain when activated .. wouldn't those skyscrapers and mountains .. rushing at you at 1,000 mph present a problem?

I can assure you of one thing .. whichever scenario happens to be the correct one .. I wont be 'sitting' in the machine when the switch is flipped!

I Warned you about the stupid questions part!
You've asked an ill-posed problem because its not clear [i]how[i] your machine would nullify gravity. Would it simply provide a force equal in magnitude but opposite in direction to any gravitational forces? Would it simply reduce the gravitational mass of any objects to zero? In both cases, you'd simply continue the trajectory at the time the switch is flipped. There's a lot of motion that you're going through that is directly influence by gravity while on Earth. To list the three most obvious:

a) You're orbiting around the Earth's axis on the Earth's surface, kept there by the gravity of the Earth.
b) You're orbiting around the Sun, kept in that orbit by the Sun's gravity.
c) You're orbiting around the galactic center, kept in that orbit by the gravity of the galaxy.

The rotation of the Earth is such that it makes one complete rotation about its axis is a sidereal day; that gives about 8 km/s at the equator and proportionally lower at higher latitudes. The orbit of the Earth around the sun is such that it makes a complete orbit in one year; that gives about 30 km/s. The sun orbits the galactic center slightly faster than 200 km/s. Taking these three motions in to account, you' can see the direction you're travelling at any instant will vary depending on the time of year and the time of day, especially as the sun's velocity overwhelms the Earth's orbital or rotational velocity.
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Old 08-18-2012, 10:31 AM
Status: "chickpea soup" (set 28 days ago)
 
18,765 posts, read 56,521,786 times
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The very concept of a massless object is an oxymoron. Consider that mass is a fundamental property of matter.

Besides, if there was no mass, gravity could not interact with that mass, and the other forces still around the object would then assert dominance. In the case of a zero mass billiard ball, it would be pushed by air currents, but because of the lack of mass it would quickly drift upwards to the ceiling like a balloon from air pressure. Also, a billiard ball without mass would not puncture a body. F=MA (force equals mass times acceleration) It literally would not have the force of a speck of dust. Asimov depends on the billiard ball retaining mass and acceleration being instantaneous. According to Newton:
Every particle of matter in the universe attracts every other particle with a force that is directly proportional to the product of the masses of the particles and inversely proportional to the square of the distance between them. The momentum of the billiard ball at the time of earth gravity nullification will keep in in relation to other nearby objects as those smaller gravitational forces begin to act upon it - slowly.
I've never considered Asimov's story to be particularly accurate, even though it is cute. Much of his work is juvenile fiction (a sub-genre of SF, not a put down).

If you were to precisely offset the gravity of earth on a particular mass while maintaining the mass of the object, say with a very small singularity, -and maintain that earth gravity nullification over time - the object would tend towards a tangential path away from earth, with that trajectory being slowed by air friction.

The larger question you are asking, "Is it possible to have a fixed point in space?", is similar to asking "Can a point have a relationship to itself?" Placement in space is all relationship based. Space itself continues to expand. The only "fixed" reference point would be the object itself.
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Old 08-18-2012, 12:05 PM
 
Location: Westwood, MA
3,829 posts, read 4,944,987 times
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Default Answered the wrong question

Quote:
Originally Posted by jayrandom View Post
You've asked an ill-posed problem because its not clear [i]how[i] your machine would nullify gravity. Would it simply provide a force equal in magnitude but opposite in direction to any gravitational forces? Would it simply reduce the gravitational mass of any objects to zero? In both cases, you'd simply continue the trajectory at the time the switch is flipped. There's a lot of motion that you're going through that is directly influence by gravity while on Earth. To list the three most obvious:

a) You're orbiting around the Earth's axis on the Earth's surface, kept there by the gravity of the Earth.
b) You're orbiting around the Sun, kept in that orbit by the Sun's gravity.
c) You're orbiting around the galactic center, kept in that orbit by the gravity of the galaxy.

The rotation of the Earth is such that it makes one complete rotation about its axis is a sidereal day; that gives about 8 km/s at the equator and proportionally lower at higher latitudes. The orbit of the Earth around the sun is such that it makes a complete orbit in one year; that gives about 30 km/s. The sun orbits the galactic center slightly faster than 200 km/s. Taking these three motions in to account, you' can see the direction you're travelling at any instant will vary depending on the time of year and the time of day, especially as the sun's velocity overwhelms the Earth's orbital or rotational velocity.
Centripetal acceleration at the equator is about a = 3.4 cm/s^2. Without gravity you'd appear to float up with that acceleration. Eventually you'd hit a terminal velocity, but that would depend significantly on the shape of the object. Let's assume your time machine is a sphere with a drag coefficient of 1/2. The centrifugal force will be m * a, the drag force at terminal velocity will be rho * v^2 * A / 4 (rho = density of air, v = terminal velocity, A = pi * r^2 = cross-sectional area of sphere). Equating these gives terminal velocity of

v = sqrt(4 * m * a / rho * pi * r^2)

Let's say your anti-gravity machine weight is 500 kg, this gives a terminal velocity of about 5 m/s. Of course as you went up the density of air would go down, so your terminal velocity would increase accordingly. The nearest spot on Earth would start moving slightly west of where you "took off".

The other centripetal accelerations are significantly smaller and you wouldn't notice them.
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Old 08-18-2012, 03:40 PM
 
Location: Chesterfield,Virginia
4,919 posts, read 4,225,777 times
Reputation: 2639
Quote:
Originally Posted by jayrandom View Post
Centripetal acceleration at the equator is about a = 3.4 cm/s^2. Without gravity you'd appear to float up with that acceleration. Eventually you'd hit a terminal velocity, but that would depend significantly on the shape of the object. Let's assume your time machine is a sphere with a drag coefficient of 1/2. The centrifugal force will be m * a, the drag force at terminal velocity will be rho * v^2 * A / 4 (rho = density of air, v = terminal velocity, A = pi * r^2 = cross-sectional area of sphere). Equating these gives terminal velocity of

v = sqrt(4 * m * a / rho * pi * r^2)

Let's say your anti-gravity machine weight is 500 kg, this gives a terminal velocity of about 5 m/s. Of course as you went up the density of air would go down, so your terminal velocity would increase accordingly. The nearest spot on Earth would start moving slightly west of where you "took off".

The other centripetal accelerations are significantly smaller and you wouldn't notice them.


My Thoughts Exactly!
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