# If we *had* to make a perfect vacuum....

• B
• Andreas C
In summary, the conversation discusses the possibility of creating a perfect vacuum and explores different techniques and challenges involved in achieving it. The hypothetical scenario involves a green alien who gives humanity a task to create a vacuum with less than one molecule per cubic centimeter in exchange for solving world problems. The conversation also touches upon the issue of outgassing and the need for a cost-is-no-object approach to eliminate economic objections.
Andreas C
Suppose a green alien came down to Earth in his big spaceship. Suppose that alien was the alien who brought life on Earth and created humanity. Suppose that alien is a bit dissatisfied with us. So basically God, if you're a christian (only green instead). So, what does he do? He asks us to create a perfect vacuum.

"You have a couple of centuries to create a perfect vacuum" he says. "No need for anything fancy, all I care is to have a space at least a tenth of a cubic centimeter that is completely devoid of any atoms, I don't care much about neutrinos and photons and other silly stuff. But it has to remain like that for at least another century, otherwise I'll bring my death beam and kill you all. If you do it, I'll solve world hunger, give you the cure to cancer, tell you the meaning of life and abolish pop up ads".

Yes, I know, "We can't create a perfect vacuum, blah blah blah..." but what if we really had to? And what if we could concentrate all of humanity's efforts on that? According to Wikipedia, concentrations of about 100 molecules per cubic centimeter have already been reached. For a space of 1/10cm^3 it gives us about 10 molecules. I know there are probably many problems other than pumping molecules out that should be addressed, such as diffusion, but these can probably be solved.

So, can it be done? If yes, how?

TL;DR: Make perfect vacuum, how?

One approach could be something like a scaled up version of a Mercury thermometer.
The vacuum above the Mercury would i guess have some small but detectable amount of Mercury vapor though.

rootone said:
One approach could be something like a scaled up version of a Mercury thermometer.
The vacuum above the Mercury would i guess have some small but detectable amount of Mercury vapor though.

Yes, I thought of that, but the vapor is a big issue...

Why can't people ask a simple question like "Can one make a vacuum so good there is less than one molecule per cubic centimeter?" without getting all cutsie-pie and bringing in aliens and death beams and God? If I were to answer a question with green aliens, you'd be annoyed at me for wasting your time.

Andreas C said:
but these can probably be solved.

So you're saying, "I am not a vacuum expert, but I am sure those of you who are aren't doing as well as you could." Do you have any idea how offensive this sounds? Especially coupled with the cutsie. Here's a suggestion - if you want an answer from an expert, don't talk down to them.

Your problem is that you had to build your box out of something. That something will outgas when you start pumping its interior down. When you get to a very good vacuum you can't really pump any more - the pump has nothing left to pump on. Furthermore, you are left with so little gas than any tiny bit of trapped gas will ruin your vacuum. Tiny like the little bits of gas trapped between screw threads. (Which is why you don't use screws)

Fervent Freyja
Andreas C said:
...,
So, can it be done? If yes, how?
TL;DR: Make perfect vacuum, how?

I see only one way of interpreting this as a sensible question: you are asking whether there are techniques that might produce better vacuums than we have produced so far, but that we haven't developed for economic reasons. You're constructing a "cost is no objection" hypothetical to eliminate any hypothetical economic objections.

If that's what you're asking, let's start over again in another thread. This one is closed.

Bystander

## What is a perfect vacuum?

A perfect vacuum is a space that contains no matter, including particles, atoms, and molecules. It is completely devoid of any substance, making it the absolute lowest pressure possible in a given space.

## Why would we need to make a perfect vacuum?

A perfect vacuum is necessary for various scientific experiments and technologies. It allows for the study of particles and gases in isolation and can also be used in the production of certain electronic devices, such as vacuum tubes.

## How is a perfect vacuum created?

A perfect vacuum cannot be created in the traditional sense, as even the most advanced vacuum pumps can only achieve extremely low pressures. However, scientists can create a near-perfect vacuum by removing as much matter as possible from a given space.

## What are the challenges of creating a perfect vacuum?

The main challenge in creating a perfect vacuum is finding a way to remove all matter from a given space. Even the tiniest particles or molecules can affect the pressure and make it difficult to achieve a perfect vacuum. Additionally, maintaining a perfect vacuum can be challenging, as any small leak can disrupt the equilibrium.

## What are the potential applications of a perfect vacuum?

A perfect vacuum has a wide range of potential applications in various fields such as physics, chemistry, and engineering. It allows for the study of fundamental particles and their interactions, as well as the production of specialized electronic devices. A perfect vacuum can also be used in industries such as semiconductor manufacturing and space travel.

• Other Physics Topics
Replies
52
Views
4K
• Electromagnetism
Replies
4
Views
781
• Sci-Fi Writing and World Building
Replies
11
Views
1K
• Other Physics Topics
Replies
0
Views
795
• Sci-Fi Writing and World Building
Replies
15
Views
3K
• General Discussion
Replies
19
Views
2K
• Science Fiction and Fantasy Media
Replies
12
Views
3K
• Sci-Fi Writing and World Building
Replies
7
Views
2K
• Other Physics Topics
Replies
6
Views
2K
• Cosmology
Replies
25
Views
2K