Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Bobsey on 04/01/2023 15:42:19
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A vacuum is a construct created by humans that sucks all the air out of a containment here on Earth .
It is said that the speed of light is c in a vacuum and I wondered if this has been tested in a vacuum ?
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Yes, every time you use a GPS.
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Yes, every time you use a GPS.
A GPS doesn't use a vacuum , it uses the spacing between things .
A vacuum is a human constuct of a containment with the air sucked out .
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A vacuum is a human constuct of a containment with the air sucked out .
Vacuums aren't a human construct. The majority of the Universe is a vacuum. However, the speed of light has been measured in a man-made vacuum, if that's what you are asking.
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A GPS doesn't use a vacuum , it uses the spacing between things .
....which are separated by a vacuum.
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A vacuum is a human constuct of a containment with the air sucked out .
Vacuums aren't a human construct. The majority of the Universe is a vacuum. However, the speed of light has been measured in a man-made vacuum, if that's what you are asking.
That is all I was asking but the Universe isn't a vacuum , humans didn't make that I'm sure . It's not like there is some humans outside of what we see that have sucked all the air out of the space .
Thanks for your answer , question answered .
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but the Universe isn't a vacuum
Most of it is.
That's part of the reason they call it "space".
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the Universe isn't a vacuum , humans didn't make that
A trivial google search says otherwise:
"The best vacuum ever constructed on Earth was done at CERN at reported to achieve a density of about 1000 atoms per cubic centimeter. While this is astonishingly low, it is still over 2 million times more dense than interstellar space!"
https://sites.coloradocollege.edu/pc357ml/2014/04/10/space-as-a-vacuum/#:~:text=The%20best%20vacuum%20ever%20constructed,more%20dense%20than%20interstellar%20space!
I googled vacuum and the defintion says ,
A vacuum is a space devoid of matter. The word is derived from the Latin adjective vacuus for "vacant" or "void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressure. Wikipedia
I always thought a vacuum was a process of extracting the air from a containment . Are you saying the universe is contained or something similar ?
As well , when we suck the air out of a containment like CERN , isn't there still some sort of energy field in their like the earths magnetic field ? Does a compass work in a vacuum ?
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but the Universe isn't a vacuum
Most of it is.
That's part of the reason they call it "space".
Is't space full of particels ? How can space be a vacuum ?
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Vacuum is the space between particles. The universe contains a lot more space than particles.
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A vacuum is a space devoid of matter.
A vacuum is a space devoid of matter according to google . Space contains planets and other matter , how can space be classed as a vacuum when it contains lots of matter ?
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Interesting & Amusing OP.
👍
Welcome to the Forum Bob!
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A vacuum is a space devoid of matter according to google
The space between the particles is devoid of matter, hence a vacuum.
Welcome to the Forum Bob!
I don't think this is his first time here. Not by a long shot.
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I always thought a vacuum was a process of extracting the air from a containment . Are you saying the universe is contained or something similar ?
Actually, while it was forming, the baby Earth extracted any nearby atoms out of space by its gravitational field, interacting with the protoplanetary disk
- The same goes even more so for the Sun (mostly hydrogen and helium) and the large planets (Jupiter, Saturn, etc)
The Sun blows out a high-speed Solar Wind, but its density is far less than the density at the surface of the Sun.
- Since the surface of the Sun is strongly compressed by gravity into the sphere we see in the sky
- By the time this Solar Wind reaches the Voyager spacecraft, its density and speed have dropped enormously. In this region, the extremely low density of the interstellar medium dominates.
CERN uses very fancy vacuum pumps, but for most of space, gravity is the invisible "pump" which keeps the air out of space.
https://voyager.jpl.nasa.gov/mission/status/
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I always thought a vacuum was a process of extracting the air from a containment . Are you saying the universe is contained or something similar ?
Actually, while it was forming, the baby Earth extracted any nearby atoms out of space by its gravitational field, interacting with the protoplanetary disk
- The same goes even more so for the Sun (mostly hydrogen and helium) and the large planets (Jupiter, Saturn, etc)
The Sun blows out a high-speed Solar Wind, but its density is far less than the density at the surface of the Sun.
- Since the surface of the Sun is strongly compressed by gravity into the sphere we see in the sky
- By the time this Solar Wind reaches the Voyager spacecraft, its density and speed have dropped enormously. In this region, the extremely low density of the interstellar medium dominates.
CERN uses very fancy vacuum pumps, but for most of space, gravity is the invisible "pump" which keeps the air out of space.
https://voyager.jpl.nasa.gov/mission/status/
I have no idea of the science you mention . I am not understanding how a space that is't empty can be classed as a vacuum .
I think the word is contradictory ?
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There is no such thing as a perfect vacuum.
But the space between the stars + planets is a much better approximation to a vacuum than any ever produced by man.
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There is no such thing as a perfect vacuum.
But the space between the stars + planets is a much better approximation to a vacuum than any ever produced by man.
I wasn't expecting weird answers , people are telling me that if one of my hands is empty and the other has coins in it , that is the same thing . A vacuum is empty of things , the space that contains millions of stars is't empty .
Am I missing something here ?
I think the word is volume ? An empty volume isn't the same as a volume with things in it ?
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Do you understand that a vacuum is impossible?
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Fortunately for science and all rational humans, Bobsey's personal problems including his philosophical definition of a vacuum are of no importance.
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Am I missing something here ?
Yes.
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Has the speed of light been tested in a vacuum?
When it comes to the speed of light, air at sea level is a pretty good vacuum.
Light slows down in a medium, compared to its speed in a vacuum
- For example, in glass, light is slowed by a factor of about 1.5
- In air at sea level, light is slowed by a factor of 1.0003
- The amount of slowing is measured by the "Refractive Index"
- See the Refractive Index list at: https://en.wikipedia.org/wiki/List_of_refractive_indices#List
For non-magnetic materials, you can calculate the amount of slowing from the measured relative permittivity of the medium.
- For air at sea level, the relative permittivity is already close to 1 (almost the same as a vacuum)
- For achievable vacuums (eg at LHC), the relative permittivity is immeasurably close to 1
- See the list at https://en.wikipedia.org/wiki/Relative_permittivity
From a totally different viewpoint, gravitational waves also travel at "c" (commonly called "the speed of light in a vacuum", but its more fundamental than that).
- Gravitational waves travel almost unaffected through the high density of the Earth, the Sun and neutron stars
- The LIGO observatory observed a neutron star merger, which was accompanied by a gamma-ray burst starting 1.7 seconds later. The source was in a galaxy 130 million light years away.
- This suggests that light travels at a speed through intergalactic space at a speed that is reduced by at most 1.7 seconds in 130 million years, ie pretty much the speed of light in a vacuum.
- See description at: https://en.wikipedia.org/wiki/Neutron_star_merger#Observed_mergers
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Or that gravitational waves travel slightly faster than light in a vacuum, or that the gamma ray burst really did occur slightly after the neutron star merger, or that the merger generated an intense local gravitational field that bent spacetime by 1.7 seconds.
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people are telling me that if one of my hands is empty and the other has coins in it , that is the same thing
That's not what we are saying at all.
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Has the speed of light been tested in a vacuum?
When it comes to the speed of light, air at sea level is a pretty good vacuum.
Light slows down in a medium, compared to its speed in a vacuum
- For example, in glass, light is slowed by a factor of about 1.5
- In air at sea level, light is slowed by a factor of 1.0003
- The amount of slowing is measured by the "Refractive Index"
- See the Refractive Index list at: https://en.wikipedia.org/wiki/List_of_refractive_indices#List
For non-magnetic materials, you can calculate the amount of slowing from the measured relative permittivity of the medium.
- For air at sea level, the relative permittivity is already close to 1 (almost the same as a vacuum)
- For achievable vacuums (eg at LHC), the relative permittivity is immeasurably close to 1
- See the list at https://en.wikipedia.org/wiki/Relative_permittivity
From a totally different viewpoint, gravitational waves also travel at "c" (commonly called "the speed of light in a vacuum", but its more fundamental than that).
- Gravitational waves travel almost unaffected through the high density of the Earth, the Sun and neutron stars
- The LIGO observatory observed a neutron star merger, which was accompanied by a gamma-ray burst starting 1.7 seconds later. The source was in a galaxy 130 million light years away.
- This suggests that light travels at a speed through intergalactic space at a speed that is reduced by at most 1.7 seconds in 130 million years, ie pretty much the speed of light in a vacuum.
- See description at: https://en.wikipedia.org/wiki/Neutron_star_merger#Observed_mergers
:o I think that information is beyond the level of my understanding and question . If I have this right you are saying that the speed of light through the spacing between particels in space is the speed of light ?
Then you are saying it slows down if it is't a vacuum like space ?
Thats all good but how can space be a vacuum when it has things in it ?
I'm so confused of your answers
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Am I missing something here ?
Yes.
What am I missing ?
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people are telling me that if one of my hands is empty and the other has coins in it , that is the same thing
That's not what we are saying at all.
You said the speed of light has been tested in a vacuum , by this I assume you meant a human made vaccuum where they suck out all the air ?
This vacuum hasnt got planets or stars in it like space , I can't understand how space is a vacuum ?
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What am I missing ?
It appears that you are missing the ability to read and understand the replies you've received. All the answers seem extremely straight forward and easy to understand yet appear to be way over your head.
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I can't understand how space is a vacuum ?
You seem to be confusing "space" with the universe, which is mostly space with a few bits of matter scattered through it. The matter either emits or absorbs light, which travels between the bits at c.
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I always thought a vacuum was a process of extracting the air from a containment .
That would make a bottle of helium a vacuum.
What am I missing ?
A bit of common sense.
I'm so confused of your answers
No you aren't, you're just being deliberately obtuse.
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I always thought a vacuum was a process of extracting the air from a containment .
That would make a bottle of helium a vacuum.
What am I missing ?
A bit of common sense.
I'm so confused of your answers
No you aren't, you're just being deliberately obtuse.
I arent been deliberately anything
In mathematics, the empty set is the unique set having no elements; its size or cardinality (count of elements in a set) is zero.[1] Some axiomatic set theories ensure that the empty set exists by including an axiom of empty set, while in other theories, its existence can be deduced. Many possible properties of sets are vacuously true for the empty set.
Any set other than the empty set is called non-empty.
In some textbooks and popularizations, the empty set is referred to as the "null set".[1] However, null set is a distinct notion within the context of measure theory, in which it describes a set of measure zero (which is not necessarily empty). The empty set may also be called the void set.
{}≠{1}
According to the math , space can't be a vacuum because it isnt a empty set
The number of elements of the empty set (i.e., its cardinality) is zero:
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What am I missing ?
It appears that you are missing the ability to read and understand the replies you've received. All the answers seem extremely straight forward and easy to understand yet appear to be way over your head.
If space is a vacuum it isn't a very good vacuum because I can see lot of matter [ Invalid Attachment ]
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According to the math , space can't be a vacuum because it isnt a empty set
The empty set is a mathematical entity, not a physical one, so that makes no sense.
The set theory has absolutely nothing to do with where the speed of light has been measured.
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If space is a vacuum it isn't a very good vacuum because I can see lot of matter
You can only see the matter because there's a vacuum between you and it.
BTW, you keep refusing to answer this.
Do you understand that a vacuum is impossible?
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If space is a vacuum it isn't a very good vacuum because I can see lot of matter
Seriously?
Just out of curiosity...
You seem to agree that we can create a vacuum in a container on earth. According to your understanding, if we had a marble in the container when we drew the vacuum would that container still be under a vacuum?
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If space is a vacuum it isn't a very good vacuum because I can see lot of matter
Seriously?
Just out of curiosity...
You seem to agree that we can create a vacuum in a container on earth. According to your understanding, if we had a marble in the container when we drew the vacuum would that container still be under a vacuum?
If you place a marble in a container then that container wouldn't be devode of all matter . People are telling me space is a vacuum devode of all matter , I can see that space isn't devode of all matter . Are they suggesting what we see doesn't exist ? In a vacuum it suppose to be empty , nothing to see and no atmosphere .
I understand thier stance , the spacing between planets is empty of atmosphere . But the space isn't empty of particles or other things . Space has lots of space dust from the stars and planets and stars
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If space is a vacuum it isn't a very good vacuum because I can see lot of matter
You can only see the matter because there's a vacuum between you and it.
BTW, you keep refusing to answer this.
Do you understand that a vacuum is impossible?
Impossible ? No i do't know this . I know we can make partial vacuums
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This vacuum hasnt got planets or stars in it like space , I can't understand how space is a vacuum ?
Steve, it's the space between the planets and stars that is a vacuum.
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According to the math , space can't be a vacuum because it isnt a empty set
The empty set is a mathematical entity, not a physical one, so that makes no sense.
The set theory has absolutely nothing to do with where the speed of light has been measured.
My speed of light question was answered but the thread developed into a what i s a vacuum thread .
There is no reason a mathematical entity can't be applied to a physical process
Volume 1 is set A and Volume 2 is set B
Set A is a empty set (vacuum)
Set B has elements (matter)
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There is no reason a mathematical entity can't be applied to a physical process
There is if it gives the wrong answer.
So please stop trying to do it.
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I know we can make partial vacuums
On a big enough scale, the universe is a pretty good partial vacuum.
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This vacuum hasnt got planets or stars in it like space , I can't understand how space is a vacuum ?
Steve, it's the space between the planets and stars that is a vacuum.
Steve?
The universal volume , isn't a empty set , vector space has particels and comets passing through it all the time , it is never really empty space . It can't be a vacuum when it isn't devode of all matter .
You all explained a vaccum is devode of all matter , space , the universe , is't devode of all matter .
I ca't understand why you cosider space is a vacuum when it isn't devode of mattter .
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I say again: space is a vacuum. The universe is mostly space, plus some matter. Do not confuse "universe" and "space"- this is a science forum, not a bunch of bad journalists torturing the language.
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I know we can make partial vacuums
On a big enough scale, the universe is a pretty good partial vacuum.
Vaccuums have vac pressure , I don't think the universe has a vac pressure
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I say again: space is a vacuum. The universe is mostly space, plus some matter. Do not confuse "universe" and "space"- this is a science forum, not a bunch of bad journalists torturing the language.
I say again , but space is't devode of all matter
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Steve?
Thebox, Starlight, DarkKnight or whatever you prefer to be called.
The universal volume , isn't a empty set , vector space has particels and comets passing through it all the time , it is never really empty space . It can't be a vacuum when it isn't devode of all matter .
You all explained a vaccum is devode of all matter , space , the universe , is't devode of all matter .
I ca't understand why you cosider space is a vacuum when it isn't devode of mattter .
You're arguing semantics and I don't really get why you're so hung up on this.
As an analogy, let's use the word "ocean" as an example. An ocean is defined as being made of water. That's simple enough. But if I started to argue that an ocean isn't really an ocean because it has islands in it (which aren't made of water), then that would be similar to what you are arguing. The ocean is what is between the islands.
Vaccuums have vac pressure , I don't think the universe has a vac pressure
What is "vac" pressure?
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Steve?
Thebox, Starlight, DarkKnight or whatever you prefer to be called.
The universal volume , isn't a empty set , vector space has particels and comets passing through it all the time , it is never really empty space . It can't be a vacuum when it isn't devode of all matter .
You all explained a vaccum is devode of all matter , space , the universe , is't devode of all matter .
I ca't understand why you cosider space is a vacuum when it isn't devode of mattter .
You're arguing semantics and I don't really get why you're so hung up on this.
As an analogy, let's use the word "ocean" as an example. An ocean is defined as being made of water. That's simple enough. But if I started to argue that an ocean isn't really an ocean because it has islands in it (which aren't made of water), then that would be similar to what you are arguing. The ocean is what is between the islands.
Vaccuums have vac pressure , I don't think the universe has a vac pressure
What is "vac" pressure?
Suck the air out of a plastic bottle , it collapses under the vac pressure . Thats what I mean by vac pressure .
Your oceans and Islands are all within the set volume , you are looking from within the volume raather than an external view of the volume with all due respect .
If you removed the islands and oceans from the set , then you'd be left with a empty set
I'm hung up on this because I think science should be precise in explanation with no room or doubt for critism .
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Suck the air out of a plastic bottle , it collapses under the vac pressure . Thats what I mean by vac pressure .
Why did you invent a worse way of saying air pressure or external pressure?
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I say again: space is a vacuum. The universe is mostly space, plus some matter. Do not confuse "universe" and "space"- this is a science forum, not a bunch of bad journalists torturing the language.
I say again , but space is't devode of all matter
Nothing is devoid of all matter.
There is no true vacuum.
All you can hope for is a partial vacuum and, on a big scale, the universe is a pretty good partial vacuum.
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I think science should be precise in explanation with no room or doubt for critism
You should start by learning some science.
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If you place a marble in a container then that container wouldn't be devode of all matter .
Well there is your problem, you don't know what a vacuum is.
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Suck the air out of a plastic bottle , it collapses under the vac pressure . Thats what I mean by vac pressure
That's not "vac" pressure, that's just the external air pressure crushing the bottle because it isn't balanced by the internal pressure of the bottle.
Your oceans and Islands are all within the set volume , you are looking from within the volume raather than an external view of the volume with all due respect .
If you are within the Universe (which you are), then you are "looking from within the volume" just as a person on an island would be "looking from within the volume" of the ocean. The analogy is still perfectly apt.
If you removed the islands and oceans from the set...
...then you would no longer be talking about an appropriate analogy, so it's irrelevant.
I'm hung up on this because I think science should be precise in explanation with no room or doubt for critism .
You're not arguing the explanation (a vacuum isn't an explanation, it's a concept), you're arguing the definition. A sufficient explanation of the definition has been given in this thread.
After getting banned from Scienceforums.net for denying the expansion of space based on bad arguments, you've decided to come back here and cause trouble for us again?
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You're not arguing the explanation (a vacuum isn't an explanation, it's a concept), you're arguing the definition. A sufficient explanation of the definition has been given in this thread.
I googled the definition and it says a vacuum is
vacuum, space in which there is no matter or in which the pressure is so low that any particles in the space do not affect any processes being carried on there. It is a condition well below normal atmospheric pressure and is measured in units of pressure (the pascal). A vacuum can be created by removing air from a space using a vacuum pump or by reducing the pressure using a fast flow of fluid, as in Bernoulli’s principle.
The universe space is not without matter . You are arguing that something that has lots of matter in it is a vacuum and I disagree because the space has matter in it . Definition disgrees with you not me .
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If you place a marble in a container then that container wouldn't be devode of all matter .
Well there is your problem, you don't know what a vacuum is.
Consider a vector space and we call this vector the earths orbital path . The vector is a empty set , what you call a vacuum . When the earth changes position as it travels the vector , the earth occupies the vector space it has moved too . The empty set isnt totally empty because the earth occupies a portion of the set .
{1}→{}
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denying the expansion of space based on bad arguments, you've decided to come back here and cause trouble for us again?
Expansion of space ? What do you mean by that ?
Causing trouble ?
I do't understand what you talking about , do you find questioing a subject offensive ?
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a vacuum, space in which there is no matter ... A vacuum can be created by removing air from a space using a vacuum pump
In physics, we can also mathematically remove the air from a space.
Assumptions
In physics we often start with a few simplifying assumptions:
- Air is 80% nitrogen, so let's assume that it is 100% nitrogen
- Lets assume that nitrogen gas is a lot of little balls bouncing around, with space (vacuum) in between them*
- Lets assume that liquid nitrogen is a lot of little balls jostling around, with no space in between them
Data
- The density of nitrogen gas at sea level is 1.25 grams per liter
- The density of liquid nitrogen is 807 grams per liter
Calculation
The volume taken up by the tiny nitrogen "balls" in 1 litre container of nitrogen gas = 1.25/807 = 0.0015 liters, or 1.5 ml.
- The remaining 0.9985 litres (99.85%) is vacuum
Conclusion
Air at sea level is 99.85% vacuum.
Check calculation
The refractive index of liquid nitrogen is 1.25
- ie light is slowed down by a factor of 1.25 when passing through liquid nitrogen.
- Air is composed of 99.85% vacuum + 0.15% matter (from above)
- If light is slowed by the presence of matter, then the refractive index of air should be somewhere around 1 + 0.25x0.0015 = 1.0004
- Which is not too far off the measured value of 1.0003 as the refractive index of air.
- So light is slowed by a factor of 1.0003 when passing through air, compared to the speed if we physically (or mathematically) removed all the matter from air.
*This has a historical precedent in assuming "a spherical cow in a vacuum" when determining whether "a cow jumped over the Moon"...
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Causing trouble ?
I do't understand what you talking about , do you find questioing a subject offensive ?
No, but inventing rubbish is offensive:
Consider a vector space and we call this vector the earths orbital path . The vector is a empty set , what you call a vacuum . When the earth changes position as it travels the vector , the earth occupies the vector space it has moved too . The empty set isnt totally empty because the earth occupies a portion of the set .
{1}→{}
Sufficient and accurate answers have been given and will help others understand.
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You suppose to be English but the americans own your asses .
I'm not aware of any mass purchases of English donkeys by the Americans.
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I think science should be precise in explanation with no room or doubt for critism .
It is, which is why you are wrong. There's little point shouting in English if you are in France, or reasserting your own ignorance of scientific terminology in a science forum.
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Hey... Does anyone have any comments on my back-of-the-envelope calculation of air being 99.85% vacuum?
Especially the part where I try to derive the refractive index of air from the refractive index of liquid nitrogen
- The method I used for that calculation used a lot of hand-waving
- What would be a better method of calculating it?
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Hey... Does anyone have any comments on my back-of-the-envelope calculation of air being 99.85% vacuum?
Especially the part where I try to derive the refractive index of air from the refractive index of liquid nitrogen
- The method I used for that calculation used a lot of hand-waving
- What would be a better method of calculating it?
While your calculation isn't precise, it's a whole lot better than lots of the ideas put forward in this thread.
Ignoring the oxygen is not a serious problem because the refractive indices of O2 and N2 are pretty similar.
It's possible to measure the speed of light in a gas at varying pressures and then plot a graph and extrapolate to zero pressure, which will give you the speed of light in a vacuum.
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Hey... Does anyone have any comments on my back-of-the-envelope calculation of air being 99.85% vacuum?
It depends on how you measured the refractive index of liquid nitrogen! Most of us would start with a light ray in air and apply a 0.03% correction, which is a bit circular to say the least.
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A small tweak to the calculation:
Solid nitrogen, at 1038 g/l has even less space between the atoms than liquid nitrogen.
https://en.wikipedia.org/wiki/Solid_nitrogen#Bulk_properties
- This gives 0.12% matter in nitrogen gas at STP
- The refractive index of solid nitrogen is 1.25
- So the calculated refractive index (assuming linear change with density) is 1 + 0.25 x 0.0012 = 1.0003
- Which is a little closer to the measured value of 1.00027
https://en.wikipedia.org/wiki/List_of_refractive_indices#List
I agree with BC that graphing the value at various attainable pressures would give an accurate trend that you could extrapolate to a perfect vacuum. This would also account for possible non-linear effects.
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This gives 0.12% matter in nitrogen gas at STP
By mass, certainly, but maybe even less by volume as the N2 molecules are tightly bound and presumably take up a bit less space than two N atoms.
Do you have data for solid argon? And if so, I wonder what impelled anyone to measure it?
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Do you have data for solid argon?
https://www.sciencedirect.com/science/article/abs/pii/S0031891463801688
I wonder what impelled anyone to measure it?
One possible reason is that solid argon is used as a "container" for reactive chemicals.
The chemicals are created by photolysis and then studied by spectroscopy while "dissolved" in frozen argon.
If you are doing spectroscopy, you need to know how much light is lost by reflection etc and knowing the refractive index would help calculate that.