How can space be both infinite and a vacuum at the same time?

SixPapaCharlie

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Space is a vacuum correct?
Then it has to be sealed right? :dunno:




sorry... Just popped into my crazy brain.
 
1) It's not a vacuum.


2) Gravity is a *****.
 
It's not?

It's pretty close to a perfect vacuum, but it there are particles floating around in interstellar space.


Tell me about it.
Gravity attracts matter. It's why our atmosphere is here instead of floating around in space.

Gravity > vacuum on a large scale.



ps, lovin' the tampico :)
 
If exposed, the whole "body swelling up" , "Blood boiling" etc suggests there is negative pressure. Space if infinite should be neutral. no pressure at all.

What am I missing?
 
You should watch the Cosmos series with Neil DeGrasse Tyson.

Linky

They are really quite good.
 
If exposed, the whole "body swelling up" , "Blood boiling" etc suggests there is negative pressure. Space if infinite should be neutral. no pressure at all.

What am I missing?
Blood boiling is not negative pressure. Consider high altitudes...higher you go, the lower the air pressure. You can "boil" liquids long before you get to zero pressure.

Negative pressure - interesting concept.

Space is not a vacuum. In fact current astrophysics thinking is that what we know as "space" is really a small part of the overall universe, that "dark matter" and "dark energy" is much larger (if such concept can exist or even be imagined) than what we are used to.
 
If exposed, the whole "body swelling up" , "Blood boiling" etc suggests there is negative pressure. Space if infinite should be neutral. no pressure at all.

What am I missing?

It doesn't take 'negative pressure' for your blood to boil. What you are thinking of as "negative" is only in relation to the weight of the atmosphere as measured at Sea Level on the surface of our planet. In an absolute sense, there is no such thing as vacuum in our universe.
 
Oh jeez, don't get all philosophical about this. Just do the math.

p(rho) = m/V

When the volume is infinite, I don't care what the mass is. Viola, a vacuum(very, very low pressure if that makes you happy) in the infinite universe.

BTW, mass represents some microscopic percentage of just this galaxy, and the other galaxies can be more or less dense. But - for the purposes of evaluation lets say the Milky Way models all galaxies within about a std dev. That puts the density at some microscopic level.

Where did anyone ever get 'sealed'? Please, leave physics to physicists.
 
"Trust me, I'm a physicist."

Not really, but I have pretended to be a doctor before.
 
Not sure what "sealed" means in this context, but space isn't a very good vacuum. I can make a much better one with an ion pump and cryogenic cold trap. Just don't get any fingerprints in the chamber.

Interstellar space has rarified gasses that can be observed in absorption from background stars.
 
Space is neither infinite nor a vacuum.

It IS however very, very big- big enough to give the illusion of infinity better than infinity itself. Similarly, it is very, very low density and pressure- not enough to be a true vacuum, but close enough for many purposes.

And it's expanding at the speed of light. Unless it's contracting. Or maybe it's staying still. We don't really know either way.
 
And it's expanding at the speed of light. Unless it's contracting. Or maybe it's staying still. We don't really know either way.

We say this because we observe evidence that generally the space between massive bodies seems to be increasing, giving credence to the theory that all matter was once much more compact. We also suppose that nothing can travel faster than certain massless particles do at the great speed limit of light, provided they aren't warped and trapped by gravity.

All of this supposition followed by a great deal of Maths carrots the donkey of the mind to the conclusion that there was some event including a large explosion that sent matter and light speeding away resulting in the observed expanding universe.

Some have said that since light can only have traveled so far since the initial event (given a finite speed limit and all) that our universe has, for all practical purposes, edges. Some folk call that a closed system. Maybe that's what sealed might mean. Maybe not.

There are other theories. I love cyclic universe theories personally. They are pretty.

And docmirror, it was Richard Feynman himself who would disagree with "leaving physics to the physicists". He had a number of zingers on the subject both ways. One of my favorite anecdotes is:

Richard Feynman, the late Nobel Laureate in physics, was once asked by a Caltech faculty member to explain why spin one-half particles obey Fermi Dirac statistics. Rising to the challenge, he said, "I'll prepare a freshman lecture on it." But a few days later he told the faculty member, "You know, I couldn't do it. I couldn't reduce it to the freshman level. That means we really don't understand it."

He also had a nice quote that it is more important that language be clear than precise.
 
All of this supposition followed by a great deal of Maths carrots the donkey of the mind to the conclusion that there was some event including a large explosion that sent matter and light speeding away resulting in the observed expanding universe.

Yeah, I was going to quote Douglas Adams since he has some good zingers about ways to wrap your head around the entirety of Creation, but couldn't find them online.

6PC- don't try to figure out the nature of the universe from pop science; your brain will hurt and you still won't have all the answers.
 

Found It!

The Guide said:
Population:
None. Although you might see people from time to time, they are most likely products of your imagination. Simple mathematics tells us that the population of the Universe must be zero. Why? Well given that the volume of the universe is infinite there must be an infinite number of worlds. But not all of them are populated; therefore only a finite number are. Any finite number divided by infinity is as close to zero as makes no odds, therefore we can round the average population of the Universe to zero, and so the total population must be zero.
 
Oh jeez, don't get all philosophical about this. Just do the math.

p(rho) = m/V

When the volume is infinite, I don't care what the mass is. Viola, a vacuum(very, very low pressure if that makes you happy) in the infinite universe.

BTW, mass represents some microscopic percentage of just this galaxy, and the other galaxies can be more or less dense. But - for the purposes of evaluation lets say the Milky Way models all galaxies within about a std dev. That puts the density at some microscopic level.

Where did anyone ever get 'sealed'? Please, leave physics to physicists.

Okay, what does a Viola have to do with it? Where's Ben when we need him :D
 
Space is neither infinite nor a vacuum.

It IS however very, very big- big enough to give the illusion of infinity better than infinity itself. Similarly, it is very, very low density and pressure- not enough to be a true vacuum, but close enough for many purposes.

And it's expanding at the speed of light. Unless it's contracting. Or maybe it's staying still. We don't really know either way.

At the speed of light?

No. The universe is known to be expanding, and the rate was measured long ago. More recently with some precision. It's proportional to distance from the observer (for redshifts well below 1), with a value of about 68 km/s/Mpc.
 
At the speed of light?

No. The universe is known to be expanding, and the rate was measured long ago. More recently with some precision. It's proportional to distance from the observer (for redshifts well below 1), with a value of about 68 km/s/Mpc.

The Observable Universe is expanding at the speed of light, as our cosmic horizon gets a foot bigger every nanosecond.
 
meh, ya bunch of cosmos weenies. So educated you have forgotten how to think for yourselves.

Space is infinite
Even photons have a finite mass lifetime before they change back to energy - so we can only see so far - which makes us think that the receding tail of of the visible wave front is the end of the universe, as the photons convert back to energy and disappear
Space is a vacuum only when compared to the mass aggregation of baryons that we call an atmosphere/matter
Baryons pull each other together forming aggregations of mass
Saying that space sucks overlooks the reality that space pushes
This expansive force is what we currently call dark energy/mass
The Dark Force (to borrow a cheesy movie term) pushes Baryonic matter apart which is why the localized knots of baryons we call galaxies are receding from one another.
Space is a seething cauldron of energy
When the energy in a given volume of space reaches/exceeds a threshold, then a tiny fragment of matter called a Proton pings into existence as the overload of energy collapses into a singularity. (also called hydrogen)
This background roar of pings coming from all directions and distances/time, including infinite, makes up the electromagnetic roar that the big bang weenies believe came from the "Big Bang"
You do know that when Fred Hoyle coined the term big bang it was a term of derision, do you not?

ah well, back to your regularly scheduled reruns of threes company to maintain your insulation from the disturbance of thought
cheers, eh wot
 
http://www.asu.edu/clubs/sps/phun/sucker.html

For years, it has been believed that electric bulbs emit light, but recent information has proved otherwise. Electric bulbs don't emit light; they suck dark. Thus, we call these bulbs Dark Suckers.
The Dark Sucker Theory and the existence of dark suckers prove that dark has mass and is heavier than light.

First, the basis of the Dark Sucker Theory is that electric bulbs suck dark. For example, take the Dark Sucker in the room you are in. There is much less dark right next to it than there is elsewhere. The larger the Dark Sucker, the greater its capacity to suck dark. Dark Suckers in the parking lot have a much greater capacity to suck dark than the ones in this room.

So with all things, Dark Suckers don't last forever. Once they are full of dark, they can no longer suck. This is proven by the dark spot on a full Dark Sucker.

A candle is a primitive Dark Sucker. A new candle has a white wick. You can see that after the first use, the wick turns black, representing all the dark that has been sucked into it. If you put a pencil next to the wick of an operating candle, it will turn black. This is because it got in the way of the dark flowing into the candle. One of the disadvantages of these primitive Dark Suckers is their limited range.

There are also portable Dark Suckers. In these, the bulbs can't handle all the dark by themselves and must be aided by a Dark Storage Unit. When the Dark Storage Unit is full, it must be either emptied or replaced before the portable Dark Sucker can operate again.

Dark has mass. When dark goes into a Dark Sucker, friction from the mass generates heat. Thus, it is not wise to touch an operating Dark Sucker. Candles present a special problem as the mass must travel into a solid wick instead of through clear glass. This generates a great amount of heat and therefore it's not wise to touch an operating candle.

Also, dark is heavier than light. If you were to swim just below the surface of the lake, you would see a lot of light. If you were to slowly swim deeper and deeper, you would notice it getting darker and darker. When you get really deep, you would be in total darkness. This is because the heavier dark sinks to the bottom of the lake and the lighter light floats at the top. This is why it is called light.

Finally, we must prove that dark is faster than light. If you were to stand in a lit room in front of a closed, dark closet, and slowly opened the closet door, you would see the light slowly enter the closet. But since dark is so fast, you would not be able to see the dark leave the closet.

Next time you see an electric bulb, remember that it is a Dark Sucker.
 
Even photons have a finite mass lifetime before they change back to energy - so we can only see so far - which makes us think that the receding tail of of the visible wave front is the end of the universe, as the photons convert back to energy and disappear

What?

Photons don't "convert back to energy". Photons are energy. They are the force mediating particles* of the electromagnetic force, just like gluons carry the strong forse and W/Z bosons carry the weak force.

They don't "expire" or "burn out" in any way. The Cosmic Background Radiation consists of photons that have been travelling since the time the universe cooled to the point that atoms formed (~380,000 years after the Big Bang)

Heck, photons don't even experience time. As they are massless and travel at the speed of light, time does not pass from a photon's perspective.



* Normally referred to as particles, however they have both particle and wave characteristics as described in quantum dynamics.
 
The Observable Universe is expanding at the speed of light, as our cosmic horizon gets a foot bigger every nanosecond.

That has nothing to do with the expanding universe. It just means finite age.

If the universe were contracting, the horizon would still grow.
 
so Space is infinite but space is not infinite
It is not a vacuum but it is a vacuum and it is not a good vacuum
It is expanding at the speed of light no its not.


It has to be infinite. We are not in s snow globe and if so, what's beyond the glass?
An infinite series of increasingly larger snow globes maybe?

I have always heard the phrase "vacuum of space"
Possibly that is a misnomer? I think even in physics it was discussed that space was a vacuum.


I sometimes think it might be more like pacman.
You go far enough in one direction, and you show up back on the other side
 
Vacuum is simply the absence of pressure much like cold is the absence of heat.
 
Yeah it's more accurate to say space in general is an area of no pressure and we live on a planet which has it's own area of some pressure.
 
Okay, what does a Viola have to do with it? Where's Ben when we need him :D

To play some dramatic music, of course.

I assume he meant "Voila!", which is French for "There it is." Personally, I prefer the English version, "Bob's yer uncle", since it makes no sense whatsoever.
 
To play some dramatic music, of course.

I assume he meant "Voila!", which is French for "There it is." Personally, I prefer the English version, "Bob's yer uncle", since it makes no sense whatsoever.

I was always partial to "I'm all sixes and sevens"
 
Lately, I 've been wondering if the universe is really expanding, or are our units of measurement shrinking?
 
Lately, I 've been wondering if the universe is really expanding, or are our units of measurement shrinking?

Well, the speed of light is known not to change or molecular hydrogen hyperfine emission lines in distant galaxies would be spaced differently than nearby, and they aren't. They are easily observed with radio telescopes at a wavelength of 21 cm.

The second is defined in terms of the cesium atomic clock, which is a Cesium hyperfine transition. Also observable (in the microwave) in very distant objects, and it's not different.

So, the meter hasn't changed in cosmological time.

Cosmic expansion is directly observable in the redshift of emission lines, by an amount proportional to their distance. Since the meter itself can't have changed, something else has to.
 
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At the speed of light?

No. The universe is known to be expanding, and the rate was measured long ago. More recently with some precision. It's proportional to distance from the observer (for redshifts well below 1), with a value of about 68 km/s/Mpc.

No, that's the matter IN the universe. The edges of the universe - the "space bubble" itself - would be expanding at the speed of light.
 
No, that's the matter IN the universe. The edges of the universe - the "space bubble" itself - would be expanding at the speed of light.

It's wildly misleading to be talking about the "edge of the universe."

There is no edge. What you're talking about is your own personal edge-like construction. It is different for any other observer in the universe.

It's more than a little like saying that a 50 year old guy defines the universe as 50 light years from himself. That defines every object he could possibly have interacted with, so it is a horizon, in a very real sense. And it does grow at the speed of light. But I think you'll agree that the universe is a bit bigger than that.

Have you observed any matter or energy not in the universe? We regularly observe effects from outside the horizon -- that's the cosmic microwave background. But no one serious I've ever come across has claimed that the CMB emission was not in the universe.
 
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It's wildly misleading to be talking about the "edge of the universe."

There is no edge. What you're talking about is your own personal edge-like construction. It is different for any other observer in the universe.

It's more than a little like saying that a 50 year old guy defines the universe as 50 light years from himself. That defines every object he could possibly have interacted with, so it is a horizon, in a very real sense. And it does grow at the speed of light. But I think you'll agree that the universe is a bit bigger than that.

The 'edge' of the universe is the speed of light, that's where time ends, and therefor matter and space since matter and space require time to exist.
 
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