When will we have anti gravity?

In summary: If you could cancel out that gravity then the air would stay in place just as a helium balloon does not float away when you blow on it. It is not being held in place directly by the air above it, but by the air below it.In summary, the conversation discusses the possibility of counteracting the force of gravity, considering the theory of general relativity and the concept of dark energy. The manipulation of gravity is also mentioned, with some disagreement on whether it is possible or not. The conversation also touches on the limitations and incompatibilities of the theories of general relativity
  • #36
SpaceTiger said:
How are we defining "space" in this discussion? If gravity were suddenly turned off for the atmosphere, the pressure gradient would act (at the speed of sound) to force many of the molecules away from the Earth's surface.
We are turning gravity off for one nitrogen molecule starting out at mean sea level (MSL) and at standard temperature and pressure (STP), and then trying to quantify how fast it would work its way out into space. My initial guess was that it would be out in space within a matter of minutes, and DaveC426913 thinks that this would not happen rapidly.
 
Last edited:
Physics news on Phys.org
  • #37
Aether said:
We are turning gravity off for one nitrogen molecule starting out at mean sea level (MSL) and at standard temperature and pressure (STP), and then trying to quantify how fast it would work its way out into space. My initial guess was that it would be out in space within a few minutes, and DaveC426913 thinks that this would not happen rapidly.

If you mean one nitrogen molecule by itself, then it seems like a no-brainer. It'll just move towards space with a speed on the order of the sound speed in the gas.

If you mean that there are other nitrogen molecules around, but gravity is not turned off for them, then the "gravity-free" nitrogen molecule will have to make its way out by diffusion. This will take:

[tex]t=\frac{N^2l}{v_s}=\frac{h_{atm}^2}{lv_s}=\frac{h_{atm}}{l}t_{free}[/tex]

In other words, it will take N times longer than the first scenario, where N is the number of mean free paths to the top of the atmosphere. The mean free path of particles in the atmosphere is very small (less than a micron, I think), so this would take a very long time.
 
  • #38
SpaceTiger said:
If you mean one nitrogen molecule by itself, then it seems like a no-brainer. It'll just move towards space with a speed on the order of the sound speed in the gas.

If you mean that there are other nitrogen molecules around, but gravity is not turned off for them, then the "gravity-free" nitrogen molecule will have to make its way out by diffusion. This will take:

[tex]t=\frac{N^2l}{v_s}=\frac{h_{atm}^2}{lv_s}=\frac{h_{atm}}{l}t_{free}[/tex]

In other words, it will take N times longer than the first scenario, where N is the number of mean free paths to the top of the atmosphere. The mean free path of particles in the atmosphere is very small (less than a micron, I think), so this would take a very long time.
We mean that there are other nitrogen molecules around, but gravity is not turned off for them. Thanks for the Eq..
 
  • #39
Aether said:
We mean that there are other nitrogen molecules around, but gravity is not turned off for them. Thanks for the Eq..
Ah. Then for sure, it would take a long time.

I wish I could remember where it was, but I once read a description about how long it takes on average for a given molecule to make its way across a room. It has to encounter countless molecules on its way, bouncing off each. The motion is a random walk.



Note: The nitrogen atom has a buoyancy equivalent to vacuum. How fast would a volume of vacuum rise?
 
Last edited:
  • #40
DaveC426913 said:
Ah. Then for sure, it would take a long time.
Agreed.
I wish I could remember where it was, but I once read a description about how long it takes on average for a given molecule to make its way across a room. It has to encounter countless molecules on its way, bouncing off each. The motion is a random walk.
For the same reason, it takes millions of years for photons to make their way from the interior of a star.
Note: The nitrogen atom has a buoyancy equivalent to vacuum. How fast would a volume of vacuum rise?
That depends on how big the volume is. A volume of vacuum the size of a weather balloon would rise faster than a weather balloon. I should have stuck with the one cubic foot of air that RandallB wanted to talk about originally. :grumpy:
 
  • #41
Interesting all thanks for this, how would a non standard 9.8m/s fit into the equation since as gas rises away from Earth gravitation decreases or wouldn't this have any apreciable effect, excuse my ignorance. Are we talking about something complicated like an integration of the effect of gravity to fit a model, or are we just ignoring it because the influence is negligable, just a thought? Let's take Jupiter as an example, how would the gaseous effects differ?
 
  • #42
Schrodinger's Dog said:
Interesting all thanks for this, how would a non standard 9.8m/s fit into the equation since as gas rises away from Earth gravitation decreases or wouldn't this have any apreciable effect, excuse my ignorance.
The Earth's gravitational acceleration at the top of the standard atmosphere is about 2% less than it is at sea level. Here is the calculation:

1. [tex]g(m, r)=G \frac{m}{r^2}[/tex]
2. [tex]G=6.67 \times 10^{-11} m^3/(kg \cdot sec^2)[/tex]
3. [tex]r_{earth}=6.38 \times 10^6m[/tex]
4. [tex]h_{atm}=70.1km[/tex]
5. [tex]m_{earth}=5.98 \times 10^{24} kg[/tex]
6. [tex]g(r_{earth})=9.80 m/s^2[/tex]
7. [tex]g(r_{earth}+h_{atm})=9.59 m/s^2[/tex]

Are we talking about something complicated like an integration of the effect of gravity to fit a model, or are we just ignoring it because the influence is negligable, just a thought?
http://en.wikipedia.org/wiki/Hydrostatic_equilibrium" [Broken] article on hydrostatic equilibrium explains how gravity compresses the atmosphere (for example, of the Earth, Jupiter, Sun, etc.) until a pressure gradient force substantially equals the gravitational force. The large number of gas particles per cubic meter in such an atmosphere presents a huge "hall of mirrors" to any small particle bouncing around inside it. Does this answer your question? If not, please let me know a little more about what it is that you're thinking of.
Let's take Jupiter as an example, how would the gaseous effects differ?
Perhaps you could look up the stats for Jupiter and substitute them into the above equation to get the gravitational acceleration at some radius, r? Then look up the average pressure, temperature, and composition of the gasses at that radius? The calculation gets a little more complicated when you're actually inside the atmosphere because some of the mass of the planet is above the radius, r, so it might be best to pick a radius that is not too deep within the planet.
 
Last edited by a moderator:
  • #43
That's exactly what I was looking for, the integration is when you try and work out how long it would take say a Nitrogen molecule or anything to move by diffusion or otherwise from the Earths surface to the edge of the atmosphere assuming there are no other factors but gaseous equilibrium or gm/r^2 with in t(s).

It was something that came up in my maths course about firing a rocket it running out of fuel and falling back to Earth. A colleague at work mentioned the gravity becomes less with distance, obviously because of the inverse square law, and it interested me because obviously astronauts may well need this sort of precision, athough in my example the height reached by the rocket was only 280 M so it was irrelevant. He then showed me whow you could integrate gm/r^2 for t, which came out as a very complicated looking equation which I really can't remember of the top of my head :smile:, that frankly was beyond my simple level of comprehension, which is what made me think of exactly the same thing with this particular question. I wonder if we'll ever get to the stage we're we use Einsteins equations in space travel rather than Newtons :smile:
 
  • #44
Found this thread on google while searching for a wieght training program and just had to post.

k your talking about creating an anti-gravity shield so you could put a wheel in it and it would spin forever. I see 2 problems

1. The energy from the wheel probably would not be enough to power the shield.
2.It is way to complicated to make a shield and get something spinning inside it when we do not even have the technology yet.

Keep it simple here and stick to modern day technology.

Think for a second. Where could something spin forever and not be effected by gravity or air?

For bonous points what would keep it in place?:confused:

Don't think like a scientist. Think like an normal person. It's a simple question. Don't think about equations.

Good Luck:rolleyes:
 
  • #45
Blades said:
Don't think like a scientist. Think like an normal person.

I tried that, it hurts my head.
 
  • #46
I find it quite the opposite. Thinking for too long like a scientist makes my head hurts. I need constant breaks.
 
  • #47
While reading along, I had a thought that I hadn't seen brought up yet.

I find it easiest to think of a rock or solid object being subject to the anti-gravity machine. As soon as a volume of material (or in this case a rock) was freed from the clutches of gravity, it would be traveling at 463 m/s tangential to the Earth's curvature (assumed to be located at the equator, 24hs in a day), while everything else would continue along its circumferential path around the earth, rather like launching something from the outside of a spinning disc. This would make the weightless volume tend to move upwards WRT the ground from which it came. As the Earth rotated farther and farther, the volume would move higher and higher, subject to drag in the atmosphere. It would continue spinning outward in an ever-increasing spiral; the only acceleration it would be subject to would be drag from the atmosphere, tending to pull it in a circular path about the planet as the volume continues to try and travel in a straight line. As the atmosphere grew thinner, the spiral path of the volume would become closer and closer to a straight line (less atmospheric drag), until at the absolute edge of the atmosphere it would shoot off into space tangentially (although not very quickly, probably around the speed of the atmosphere at that altitude, about 470 m/s).

This is assuming of course the anti-gravity machine could either follow the volume, or target its volume accrodingly. Kind of an interesting way to launch things into space...
 
Last edited:
<h2>1. When will anti-gravity be invented?</h2><p>The development of anti-gravity technology is still in its early stages and there is no definitive answer as to when it will be fully realized. Scientists are constantly researching and experimenting with different methods, but it may still take many years before a viable solution is found.</p><h2>2. How does anti-gravity work?</h2><p>The concept of anti-gravity is based on the idea of manipulating gravitational forces, which is currently not fully understood. Some theories suggest using powerful electromagnetic fields or creating a negative mass, but these are still hypothetical and require further research and experimentation.</p><h2>3. Will anti-gravity be available for everyday use?</h2><p>It is difficult to predict if and when anti-gravity technology will be available for everyday use. While it has the potential to revolutionize transportation and other industries, it also presents many challenges and safety concerns that need to be addressed before it can be widely implemented.</p><h2>4. Can anti-gravity be used to defy the laws of physics?</h2><p>No, anti-gravity does not defy the laws of physics. It is simply a proposed method of manipulating gravitational forces, which are governed by the laws of physics. Any advancements in this technology will still have to abide by these fundamental laws.</p><h2>5. Are there any potential risks associated with anti-gravity?</h2><p>As with any new technology, there are potential risks and uncertainties that need to be carefully considered. These include the potential impact on the environment, potential side effects on human health, and the possibility of misuse or accidents. Extensive research and testing will need to be done to ensure the safety and ethical implications of anti-gravity technology.</p>

1. When will anti-gravity be invented?

The development of anti-gravity technology is still in its early stages and there is no definitive answer as to when it will be fully realized. Scientists are constantly researching and experimenting with different methods, but it may still take many years before a viable solution is found.

2. How does anti-gravity work?

The concept of anti-gravity is based on the idea of manipulating gravitational forces, which is currently not fully understood. Some theories suggest using powerful electromagnetic fields or creating a negative mass, but these are still hypothetical and require further research and experimentation.

3. Will anti-gravity be available for everyday use?

It is difficult to predict if and when anti-gravity technology will be available for everyday use. While it has the potential to revolutionize transportation and other industries, it also presents many challenges and safety concerns that need to be addressed before it can be widely implemented.

4. Can anti-gravity be used to defy the laws of physics?

No, anti-gravity does not defy the laws of physics. It is simply a proposed method of manipulating gravitational forces, which are governed by the laws of physics. Any advancements in this technology will still have to abide by these fundamental laws.

5. Are there any potential risks associated with anti-gravity?

As with any new technology, there are potential risks and uncertainties that need to be carefully considered. These include the potential impact on the environment, potential side effects on human health, and the possibility of misuse or accidents. Extensive research and testing will need to be done to ensure the safety and ethical implications of anti-gravity technology.

Similar threads

  • Beyond the Standard Models
4
Replies
105
Views
10K
  • Special and General Relativity
2
Replies
50
Views
2K
  • Beyond the Standard Models
Replies
19
Views
2K
  • Science Fiction and Fantasy Media
Replies
4
Views
2K
  • Special and General Relativity
3
Replies
95
Views
4K
Replies
72
Views
5K
  • Special and General Relativity
Replies
9
Views
1K
  • Astronomy and Astrophysics
Replies
30
Views
3K
  • Beyond the Standard Models
Replies
0
Views
898
  • Special and General Relativity
Replies
27
Views
4K
Back
Top