Creating a Better Vacuum in Outer Space
The air we breathe on Earth contains approximately (10^{25}) molecules per cubic meter, whereas the vacuum of interplanetary space near Earth is described by as few as 5 particles per cubic centimeter. In the vast void of interstellar space, the density drops to approximately one particle per cubic meter. The intergalactic vacuum is even more emptier, with the mean distance between hydrogen nuclei estimated at around a billion light years. No earthly vacuum chamber could ever match the purity of these cosmic vacuums. Even the best ultra-high vacuum chambers on Earth can only reach about 100 particles per cubic centimeter, significantly lower than the conditions found in space.
Space Vacuums: Easier, Not Better
While the vacuum of space is nearly perfect for practical purposes, it is not necessarily better than the best vacuums on Earth. NASA has reported that there are about 8 million particles per cubic meter of dust and particles in space. In contrast, the best vacuum on Earth, such as those used in the LIGO observatory, can reach pressures as low as (10^{-12}) torr, while space offers a vacuum even purer, with pressures as low as (10^{-17}) torr. This means that even with the most advanced technology, we are still far from equaling the vacuum found in space.
Understanding the Basis of Vacuum
It's important to note that there is no such thing as a perfect vacuum, even in the best terrestrial chambers. In the best vacuum conditions, virtual particles continuously pop in and out of existence. Furthermore, the 16 or 17 known quantum fields are always present, further complicating matters. Therefore, when referring to a better vacuum in space, it's more accurate to say that space is easier to achieve a high vacuum state rather than it being inherently superior.
Practical Applications and Simplicity
Given the ideal vacuum conditions in space, creating a vacuum is simply a matter of opening a container to space. As one astronomer humorously pointed out, "You just need a glass jar or any container, put a lid on it, and voila! You have a vacuum in a bottle."
Challenges in Achieving Vacuum on Earth
Getting a really tough vacuum with current technology is incredibly challenging. The very best ultra-high vacuum chambers can only reach about 100 atoms per cubic centimeter. In comparison, the space between galaxies is ten million times better, with densities estimated at just 10 atoms per cubic meter. A significant challenge lies in the out-gassing from the surfaces of pump and container components. Even solid materials, like sheet metal, will release a few atoms due to these processes, which limits the effectiveness of the vacuum.
Despite these limitations, there are ongoing efforts to develop new materials and technologies that might one day rival the purity of space vacuums. However, until then, the vacuum of space remains a truly unparalleled state of matter, offering insights into the fundamental nature of the universe and providing a benchmark for understanding material behavior under extreme conditions.