Question

can you measure a vacuum?

Answer 1

how?

Answer 2

What does it exactly mean to 'measure' vacuum. We can only measure physical quantities. Do you mean that you want to measure the 'amount' of vacuum?

Answer 3

Sure. A vacuum is defined as having zero pressure (the lack of molecules is inferred from this).

Just hook up a pressure gage. If it reads -1 atm, -14.7 psi, or -101 kPa, we have a vacuum.

Answer 4

is there really such a thing as a vacuume

Answer 5

I don't know if a true vacuum can be created. Space isn't even a true vacuum. We can get pretty darn close in the labs these days. Ultra-high vacuums can get as low as 100nPa absolute pressure or 100 particles/cm^3. Space is less than this, with hydrogen atoms being miles apart from each other. Quantum physics seems to argue that a true vacuum could never exist.

Refer to the second intro paragraph: http://en.wikipedia.org/wiki/Vacuum

Answer 6

I guess i am arguing that even if one could theoretically exist , it could not be measured

Answer 7

I don't see why not. If we can measure an Ultra-high vacuum why shouldn't we be able to measure a true vacuum?

Answer 8

When we measure a ultra high vacuum we are measuring how many particles are in the space, if there are no particles how can we measure them?

Answer 9

The lack of a reading at all would indicate to me that no particles exist, and therefore a vacuum has been achieved.

If we use a thermometer to measure temperature, we are reading the thermal energy present in a chunk of matter. How would we know that matter has a temperature of 0K? The thermometer would read zero.

Our vacuum-o-meter would also read zero in a perfect vacuum. Or it's broken.

Answer 10

well it cant be perfectly accurate can it, there will be a distribution of measurements

Answer 11

Indeed not. Every measurement we ever take has a certain degree of uncertainty. We cannot say with 100% certainty that we have achieved a true vacuum, but I bet we could be 95% sure. There is a certain amount of "acceptable" uncertainty that we must deal with.

Answer 12

This goes with anything. We cannot measure temperature with 100% certainty. If your argument is whether or not we can measure a vacuum with 100% certainty, than the answer will be no regardless of what we are measuring.

Answer 13

But temperature is different,
Temperature is not defined for a small system

Answer 14

Nothing can be measured with 100% certainty is the point I'm trying to get across. It seemed like that was the argument you were making.

Answer 15

yeah i agree,

Answer 16

We actually belive there may be a true vacuum in the universe, there is an area of about 400 Light years in volume if I remember correctly where there is absolutly NOTHING there, nothing we can see anyways, no light, no x-rays, nothing. maybe that is your perfect vacum?

Answer 17

I will go look up the name we gave that area, one moment.

Answer 18

Road trip!

Answer 19

!

Answer 20

Aparently it is much larger then I remembered, lol, sending you a link to a small detail on it. http://www.space.com/4271-huge-hole-universe.html

Answer 21

Does that satisfactorily answer your question?

Answer 22

cool