Understanding Negative Pressure and its Role in the Expansion of the Universe

In summary, the conversation discusses the concept of negative pressure being responsible for repulsive gravity and its relationship to the expansion of the universe. It also mentions the idea of negative gravitational energy balancing out the total energy in the universe. However, there is no conclusive evidence for repulsive gravity and the concept of negative energy in gravity is a matter of convention. The conversation also briefly touches on the topic of dark energy and its role in the expansion of the universe.
  • #1
zeromodz
246
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I read somewhere that negative pressure is responsible for repulsive gravity that is increasing the expansion of the universe. Can repulsive gravity exist? and if so how is it related to negative pressure?

I also heard that the negative gravitational energy compensates for all other energies in the universe making the total energy in the universe zero.
 
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  • #2
zeromodz said:
Can repulsive gravity exist? and if so how is it related to negative pressure?
There is no evidence for repulsive gravity, there are possible measurements that suggest the normal law of gravity isn't quite right on large scales (gravity is weaker than it shoudl be) but nothing conclusive.

I also heard that the negative gravitational energy compensates for all other energies in the universe making the total energy in the universe zero.
This isn't 'negative gravity' it's just how you do the calculation. If you start with the mass in one point and lift the masses outward it's easier to make that energy negative, so when the mass is attracted back inward, that movement is postive - but it's purely a question of convention. It was once thought that the energy of the gravity expansion balanced the mass-energy of the rest if the universe - that isn't true.
 
  • #3
mgb_phys said:
It was once thought that the energy of the gravity expansion balanced the mass-energy of the rest if the universe - that isn't true.

On what premise have we discredited this? Did we disprove this somehow?
 
  • #4
mgb_phys said:
There is no evidence for [..]
It sounds like the OP is referring to dark energy which, if I understand correctly, can be represented as negative pressure in GR's source tensor, has a repulsive consequence of accelerating intergalactic expansion, and still figures prominently in the mainstream picture.
 
  • #5
ok - I thought they mean the pioneer anomoly
 

1. What is negative pressure?

Negative pressure refers to a situation where the pressure in a system or space is lower than the surrounding atmospheric pressure. This can occur naturally or be artificially created through various methods.

2. How is negative pressure created?

Negative pressure can be created through mechanical means, such as using a vacuum pump, or by controlling the airflow in a system. It can also occur naturally, for example, when air moves from an area of higher pressure to an area of lower pressure.

3. What is the purpose of negative pressure?

Negative pressure can serve various purposes, including maintaining a clean environment by preventing the spread of contaminants or controlling the temperature and humidity in a controlled space. It is also commonly used in medical settings to contain infectious diseases.

4. Is negative pressure safe?

Negative pressure is generally considered safe when used appropriately and in controlled environments. However, it is essential to follow safety protocols and use protective equipment when working with negative pressure, as it can pose a risk of injury if mishandled.

5. What are some examples of negative pressure applications?

Negative pressure is commonly used in industries such as healthcare, pharmaceuticals, and research laboratories. It can also be found in everyday applications, such as vacuum cleaners, air conditioning systems, and ventilation systems in buildings.

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