# How Much Does Space Weigh?

#### Da Blob

##### Banned
So vacuum is an ideal state, so that the space of Outer Space is only relatively a vacuum. So space has a range of density from the heavy space near black holes to the space between galaxies at the fringes of the universe. So how much does all of that light-filled space weigh?

#### Proletar

##### Deus Sex Machina
Nothing. It's in space.

#### Nick

##### Frozen Fighter
A range from 0.1–1000 atoms/cm^3,
want to play it safe, the interstellar medium I would say is 1 atom/cm^3, now you just to figure out how much 'space' you want to measure and you'll have some sort of weight. The weight usually from hydrogen atoms.

#### walfin

##### Democrazy
Da Blob said:
So how much does all of that light-filled space weigh?
Nothing, because there's nothing pulling the entire universe gravitationally.

#### kurt_cagle

##### Redshirt
Weight is meaningless in space because you have to have a reference force vector as a point of comparison - your weight near a black hole will be considerably higher (by several orders of magnitude) than your weight on earth, and the weight of your feet will be far greater than the weight of your head (usually leading to rapid spaghetification).

You can talk about density, which is an indication of the mass of a particle per unit area. Density of particles in the solar system is fairly high - hundreds of atoms per cubic centimeter, mostly due to the stellar wind. In interstellar space, that number drops to perhaps 10s of atoms per cubit meter. In intergalactic space, the number is probably only one or two atoms per cubic kilometer. When you get to the voids, it's conjectured that you may be looking at handfuls of particles per light year. The voids are very, very empty.

However, even that's not a clean answer, because space itself has vacuum energy - because Planck's constant is not quite zero, there is a small probability that at any given point a particle may be brought into existence due to the energy of the vacuum. Thus, while the density of an arbitrary region in space may be close to zero, it will never be at zeron.

#### just george

##### Bull**** Artist ENTP 8w7
gravity is an energetic field that affects mass. Weight is a measure that reflects the effects of gravity on mass. Without knowing what mass is where, and what gravity is where, this question makes no sense - unless you assume that the universe is infinite, in which case mass and gravity are for all intents and purposes infinite, in which case the mass of the universe is infinite.

The thing is though (and the purpose of the previous paragraph), is that you're talking about space, not mass. Space is not mass, and is therefore not affected by gravity. Hence, the measure of weight does not apply to space, and so the answer is either nothing, or "does not apply", depending on your point of reference.

#### Architect

##### Professional INTP
It's more complicated than that folks, here are the components

• Interstellar gas and matter occupying the region
• Dark matter occupying the region
• "Quantum foam"* occupying the region
• Curvature** of the region

* particle/anti particle creation/destruction occurring at the Planck length. If the region happens to have an intense gravitational field across it (say it's at the edge of a black hole) then the particle pair creation will get ripped apart and the particles (or anti-particles) will count in the mass.

** Does a spacetime region with curvature (gravitational field) have mass? I should know this, table it for now - too early.

#### Wolf18

##### a who
How much space? Outer space? The space between mass? There are particles roaming around out there - the occasional hydrogen or carbon atom... but your question is too broad. I'd say that every stray hydrogen atom in "outer space" all added together would equal about 100kg, but I have no evidence. It's just a hypothesis. However, as @Architect said, there's also time, quantum foam and the stuff we don't know about.

SW

#### Vrecknidj

##### Prolific Member
Answering the question "Does space have mass" requires that we know what space is. Unfortunately, that's a complicated question. And, presently, (pardon the pun), this question is actually quite important in physics.

#### gilliatt

##### Active Member
There is space between two objects, space like time is a relationship. Two objects occupy different positions. Space is a relational concept, it isn't anywhere, not an entity. Ex: you are in Berlin, I am in Chicago. That is where we stand in the universe, just a relationship in a container called the universe.

#### TheScornedReflex

##### (Per) Version of a truth.
Space weighs nothing. Now the things filling space up, well, that's another story.