# Is this solution for interstellar travel viable?

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• Giovanni Cambria
In summary, the conversation discusses the possibility of enabling FTL travel through the use of negative energy between two Casimir plates. This is based on the concept of negative mass and the Shapiro time gain, which suggests that in the presence of negative mass, light can cover distances faster than the speed of light. However, it is pointed out that the Casimir effect is short range and not relevant for interstellar distances. Additionally, the idea of using negative mass for FTL travel is debunked, as it is based on a misunderstanding of the effects of negative energy on spacetime.
Giovanni Cambria
TL;DR Summary
Does Casimir Vacuum gravitationally repeal matter? If so, there is a way to enhance the effect through B field? If so, what are the consequences for interstellar travel?
I have in mind a way to enable FTL travel. Is this way viable?

In the paper: "Weighing the vacuum with the Archimedes experiment"

we can see the dependency of the gravitational repulsion exerted by Casimir Vacuum on the energy between the plates. The force goes as E / c^2.

In the papers: "Casimir effect with quantized charged spinor matter in background magnetic field"

we can observe that negative energy between the plates can be arbitrarily low if a B field sufficiently strong is provided. Moreover when the B field diverges the total energy (field energy + Casimir vacuum energy) goes to minus infinite. (see equations 85, 106, 107 for the Casimir vacuum energy) So this implies that, if a B field sufficiently strong is provided, we can have an arbitrarily strong repulsive gravitational force: it is exactly what we need in order to make FTL travel possible.

To understand why, read the following: fact is that, when negative mass is involved, the Shapiro effect changes sign so, instead of a Shapiro delay, you'll have a Shapiro 'early arrival'. So, in presence of a negative gravitational mass, light (and ultra relativistic particles or spaceships) cover the distance between A and B in a time shorter than d(A,B)/c0. Where d(. , .) is the ordinary euclidean distance. For the same reason, in presence of a positive gravitational mass, light (and ultra relativistic particles) cover the distance between A and B in a time higher than d(A,B)/c0.

The aforementioned idea (the Shapiro time gain) is not new but was presented in

"Microlensing by natural wormholes: Theory and simulations"

The Casimir effect is very short range. It is irrelevant over interstellar distances.

Casimir effect is short range.
But gravitationally speaking 2 Casimir plates are equivalent to a (very tiny) negative mass. (see also: How does Casimir energy fall? II. Gravitational acceleration of quantum vacuum energy)

Using an externally generated B field you could make this (usually super-tiny) negative mass as large as you want so enabling negative Shapiro delay.

Giovanni Cambria said:
gravitationally speaking 2 Casimir plates are equivalent to a (very tiny) negative mass.

No, they're not. Dark energy, which is basically what the region between two Casimir plates is being described as in the references you give, has positive energy density and negative pressure. This does lead to effects like the accelerated expansion of the universe, but it in no way allows FTL travel.

Giovanni Cambria said:
negative Shapiro delay

Which just means that the path of light through spacetime is different from what one would expect if spacetime were flat, in such a way that the travel time is shorter. But that is a change in the structure of the light cones in spacetime. It is not a way for anything to travel FTL, i.e., outside the light cones.

In short, you have a fundamental misunderstanding.

Dale

## 1. What is interstellar travel and why is it important?

Interstellar travel refers to the ability to travel between stars and explore the vastness of space. It is important because it allows us to expand our knowledge and understanding of the universe, and potentially discover new resources and habitats for humanity.

## 2. What are the current limitations of interstellar travel?

The main limitations of interstellar travel are the vast distances involved and the lack of technology that can travel at speeds close to the speed of light. Additionally, the effects of cosmic radiation and the need for sustainable energy sources are also challenges that need to be addressed.

## 3. What are some proposed solutions for interstellar travel?

Some proposed solutions for interstellar travel include using advanced propulsion systems such as nuclear fusion or antimatter engines, developing faster-than-light travel technology, and harnessing the power of black holes or wormholes.

## 4. Is there any current research or progress being made towards interstellar travel?

Yes, there is ongoing research and progress being made towards interstellar travel. Scientists and engineers are constantly exploring new technologies and concepts that could potentially make interstellar travel a reality in the future.

## 5. What are the potential risks and challenges of interstellar travel?

Some potential risks and challenges of interstellar travel include the high cost and resources needed for development, potential dangers from cosmic radiation and debris, and ethical considerations such as the impact on other civilizations or ecosystems that may be encountered during the journey.

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