# Alcubierre Metric: York Time Cause and Effect

• MattRob
In summary: The paper talks about the energy density magnitude and York time. It states that by creating this toroidal geomoetry of energy density, the York time magnitudes will come as a result. At least, that's the impression the paper gives me.I'm left puzzled as to why it would be necessary, then, to invoke negative energy density to generate this "warp field"?
MattRob
So, there's a paper here that I'm a bit confused about. On pages 3 and 4, it talks about energy density magnitude and York time.

What I'm a bit confused about, is in the article that linked me to it, the scientist makes mention of eventually generating negative vacuum energy.

However, from reading the paper, I get the impression that the energy density distribution is the cause: That by creating this toroidal geomoetry of energy density, the York time magnitudes will come as a result. At least, that's the impression the paper gives me.

To quote:
... While this line of reason seems to resolve the paradox, it also suggests that the York Time may not be the driving phenomenon, rather a secondary result. In this physical explanation of the mathematics, the York Time might be thought of as perhaps a Doppler strain on space as this spherical region is propelled through space. A pedestrian analog to use to help envision this concept would be to consider the hydrodynamic pressure gradients that form around a spherical body moving through a fluid – the front hemisphere has a high pressure region while the rear hemisphere has a low pressure region. Analogously, the warp bubble traveling through space-time causes space to pile up (contract) in front of the bubble, and stretch out (expand) behind the bubble.

But if that's the case, then why is generating negative vacuum energy necessary: Is that just to better understand negative York time, or is it necessary? Which causes which? Does the York time geometry result in the energy density distribution, or does the energy density distribution cause the York time geometry?

Because while it seems to really heavily indicate that the toroidal placement of energy density causes the York time curvature, I'm left puzzled as to why it would be necessary, then, to invoke negative energy density to generate this "warp field"?

Because if the York time is a result of the toroidal energy density, then wouldn't negative energy density be unnecessary to generate the "warp field", but rather come as a consequence of generating it with positive energy density?

xs2022
Harold White's work is not generally accepted in the GR community. Matt Visser and many others have published multiple different proofs that negative energy is required to create any warp drive or any stable wormhole.

pinball1970
MattRob said:
So, there's a paper here that I'm a bit confused about. On pages 3 and 4, it talks about energy density magnitude and York time.
In the pdf at the bottom of this link, it states everywhere that negative energy is required. How do conclude it says otherwise?

## 1. What is the Alcubierre Metric?

The Alcubierre Metric is a mathematical model developed by physicist Miguel Alcubierre in 1994. It describes a hypothetical way of achieving faster-than-light travel by manipulating the fabric of space-time.

## 2. How does the Alcubierre Metric work?

The Alcubierre Metric suggests that by creating a "warp bubble" around a spacecraft and expanding the space behind it while contracting the space in front of it, the ship could effectively move faster than the speed of light. This is known as "warp drive" or "warp speed."

## 3. What is the York Time in the Alcubierre Metric?

The York Time is a concept within the Alcubierre Metric that refers to the time experienced by an observer within the warp bubble. It is named after physicist James W. York Jr., who contributed to the development of the Alcubierre Metric.

## 4. Is the Alcubierre Metric possible?

The Alcubierre Metric is currently considered a theoretical concept and has not been proven to be possible. It relies on the manipulation of space-time, which is not yet fully understood or achievable with current technology.

## 5. What are the potential implications of the Alcubierre Metric?

If the Alcubierre Metric were to be proven possible, it could potentially revolutionize space travel by allowing for faster-than-light travel. This could have significant impacts on space exploration, communication, and travel within our solar system and beyond.

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