Can Negative Mass Really Defy Gravity?

In summary: He's probably used to dealing with people who don't understand what he's saying.What then is negative mass?I see nothing wrong in having questions about negative mass, which is not a priory excluded by GR.
  • #1
stglyde
275
0
Michio Kaku mentions in his TV series "Physics of the Impossible" about negative mass being able to repel gravity. I haven't heard much about this before.

How would the negative mass affects the geodesic in spacetime manifold? Perhaps by causing negative curvature of spacetime? Would this actually make object float without propulsion but merely maintaining or stabilizing the negative mass?
 
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  • #2
"Beam me up, Scotty." You haven't heard much about negative mass, stglyde, because it doesn't exist. They don't call the program "Physics of the Impossible" for nothing. Kaku has discovered how much money can be made by talking about fantasy physics as if it were real. There's apparently a big audience for this. If you want to learn about physics, TV is not the place to do it.
 
  • #3
Bill_K said:
"Beam me up, Scotty." You haven't heard much about negative mass, stglyde, because it doesn't exist. They don't call the program "Physics of the Impossible" for nothing. Kaku has discovered how much money can be made by talking about fantasy physics as if it were real. There's apparently a big audience for this. If you want to learn about physics, TV is not the place to do it.

No. Kaku didn't invent the term. It's just an uncommon term that is even mentioned in peer reviewed journal:

http://rmp.aps.org/abstract/RMP/v29/i3/p423_1

Anyway. Wiki mentioned it as:

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

"In theoretical physics, negative mass is a hypothetical concept of matter whose mass is of opposite sign to the mass of the normal matter. Such matter would violate one or more energy conditions and show some strange properties such as being repelled rather than attracted by gravity. It is used in certain speculative theories, such as on the construction of wormholes. The closest known real representative of such exotic matter is a region of pseudo-negative pressure density produced by the Casimir effect."
 
  • #4
Bill_K said:
"Beam me up, Scotty." You haven't heard much about negative mass, stglyde, because it doesn't exist. They don't call the program "Physics of the Impossible" for nothing. Kaku has discovered how much money can be made by talking about fantasy physics as if it were real. There's apparently a big audience for this. If you want to learn about physics, TV is not the place to do it.

+1 on that !
 
  • #5
Bill_K said:
"Beam me up, Scotty." You haven't heard much about negative mass, stglyde, because it doesn't exist. They don't call the program "Physics of the Impossible" for nothing. Kaku has discovered how much money can be made by talking about fantasy physics as if it were real. There's apparently a big audience for this. If you want to learn about physics, TV is not the place to do it.
+2 on that!

I am getting to despise those kinds of TV shows. A good measure of the non-scientific nature of the spoutings of Kaku/Greene/pick your poison spout is to look at the traffic on this site. It spikes. We have to clean up after their mess.
 
  • #6
OK, am not a Kaku fan (at least his pop sci personality, some of his technical books have been quite helpful for me) and have never seen Greene, but is it possible to find a good question in the nonsense?

Eg. Are Barcelo and Visser justified in claiming the null energy condition "moribund"?
 
  • #7
atyy said:
OK, am not a Kaku fan and have never seen Greene, but is it possible to find a good question in the nonsense?

Eg. Are Barcelo and Visser justified in claiming the null energy condition "moribund"?

Violation of the energy conditions is not at all the same as negative mass. It's been a little while since I looked at the paper you reference (I had a thread about it here, to discuss alternatives to energy conditions), but I don't recall negative mass in any of their motivations for the limitations of energy conditions.
 
  • #8
PAllen said:
Violation of the energy conditions is not at all the same as negative mass. It's been a little while since I looked at the paper you reference (I had a thread about it here, to discuss alternatives to energy conditions), but I don't recall negative mass in any of their motivations for the limitations of energy conditions.

What then is negative mass?
 
  • #9
I see nothing wrong in having questions about negative mass, which is not a priory excluded by GR. Also I do not see any point in slandering Kaku or Greene.

Frankly I do not understand the arrogant attitude of some of those who have the label "science advisor" on this forum.
 
  • #10
One reason I thought "negative mass" could be a handwavy reference to an energy condition violation is eg. Thorne refers to exotic material in a wormhole having negative energy density, says that energy is mass, and this negative mass defocusses light beams http://books.google.com/books?id=GzlrW6kytdoC&dq=thorne+worm&source=gbs_navlinks_s p488.

Passionflower said:
Also I do not see any point in slandering Kaku ...

I'm sure he'll take our "slander" as a compliment! He writes technical books too which are sane, sane, sane. I'm sure this is his stage personality! Reminds me of :biggrin:
 
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1. What is negative mass and how does it relate to gravity?

Negative mass is a hypothetical concept in physics that refers to a type of mass that has a negative value. It is believed that negative mass would behave differently than regular mass, causing it to repel rather than attract other objects. This would have implications for the force of gravity, as negative mass would theoretically create a repulsive force against positive mass, counteracting the force of gravity.

2. How does negative mass repel gravity?

The exact mechanism of how negative mass would repel gravity is still a topic of debate among physicists. However, it is believed that negative mass would interact with positive mass through a repulsive force, acting in the opposite direction of normal gravity. This would result in an overall weakening or even reversal of the gravitational pull between two objects with opposite masses.

3. Is negative mass a proven concept?

No, negative mass is purely theoretical at this point and has not been observed or proven in experiments. It is a concept that has been proposed in certain theories, such as the theory of dark matter, but it has not been confirmed by any empirical evidence.

4. What are the potential implications of negative mass for our understanding of the universe?

If negative mass were to exist, it would have significant implications for our current understanding of the universe and the laws of physics. It could potentially help explain phenomena such as dark matter and dark energy, which are still poorly understood. It could also have implications for space travel and the possibility of anti-gravity technology.

5. Are there any experiments being conducted to test the existence of negative mass?

There have been some attempts to observe and measure negative mass, but so far, no conclusive evidence has been found. Some ongoing experiments, such as the Laser Interferometer Gravitational-Wave Observatory (LIGO), are looking for anomalies in the behavior of gravity that could potentially be attributed to negative mass. However, further research and experimentation are needed to determine the validity of this concept.

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