[onemind]

Hi, I was wondering if anyone knew how cold complete coldness is? Is it measurable? eg its 36 degrees celsius where i'm at at the moment. If I was to zoom straight up beyond the atmosphere, it would be pretty cold but the temperature would still be affected by the sun. If I was then to zoom off out into space well beyond all the stars created by the big bang to a totally isolated spot that is not touched by any light or energy, so you cant see any stars ect, complete black. How cold would it be? Is this known?
Thanks for any info :-)

[mustang292]

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We usually use the Kelvin temperature scale, where Zero Kelvin is this "absolute zero" temperature -- or -273 degrees C. Water freezes at +273 Kelvin and water boils at +373 Kelvin.

If we put a thermometer in darkest space, with absolutely nothing around, it would first have to cool off. This might take a very very long time. Once it cooled off, it would read 2.7 Kelvin. This is because of the "3 degree microwave background radiation." No matter where you go, you cannot escape it -- it is always there.

Jonathan Keohane
for Ask a High-Energy Astronomer

Go here for more--->http://imagine.gsfc....rs/980301b.html

[onemind]

Wow, thanks Mustang :-)

[J.C.MacSwell]

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Hi, I was wondering if anyone knew how cold complete coldness is? Is it measurable? eg its 36 degrees celsius where i'm at at the moment. If I was to zoom straight up beyond the atmosphere, it would be pretty cold but the temperature would still be affected by the sun. If I was then to zoom off out into space well beyond all the stars created by the big bang to a totally isolated spot that is not touched by any light or energy, so you cant see any stars ect, complete black. How cold would it be? Is this known?
Thanks for any info :-)

It is 2.7 K because of the minimal light or energy you would still receive and, after reaching equlibrium, emit. This is assuming you are "on the big bang track" with the energy coming in balanced/equal from all directions. The "night sky" would look basically the same except you may not recognize the patterns/constellations depending on how far off you moved.

[swansont]

Mustang -
If you are not actually Jonathan Keohane you should be more clear when you are quoting someone else and differentiate between quoted material and your own contributions.

You also should consider that what you quoted is copyrighted. "Fair use" allow you to quote passages, but not whole articles or large chunks of them.

[Johnny5]

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Hi, I was wondering if anyone knew how cold complete coldness is? Is it measurable? eg its 36 degrees celsius where i'm at at the moment. If I was to zoom straight up beyond the atmosphere, it would be pretty cold but the temperature would still be affected by the sun. If I was then to zoom off out into space well beyond all the stars created by the big bang to a totally isolated spot that is not touched by any light or energy, so you cant see any stars ect, complete black. How cold would it be? Is this known?
Thanks for any info :-)

Absolute zero, provided that your thermometer can read temperature perfectly.

If you were to put that very same thermometer around our location, then it will read 2.7 degree background radiation, but we are located within the sphere of explosion of Big Bang. But, exterior to that explosion, there is true vacuum.

With that firmly in mind, there can't be any radiation there, whence I say your thermometer would read zero.

[mustang292]

Swansont How much clearer do I need to be? I put his name to show it was his statement, And I Put the link so onemind could go read the complete information on it. If I wanted credit, I would not have included his name or a link.

I gave pertinent information to onemind about his question with the reference of where I got it from. I helped him to answer his question, which is something I don't see much of anyone else in this forum do.

[ecoli]

You should still put quotes, or a quote box around the text, in order to avoid the confusion.

[5614]

Johnny5 said:

Absolute zero, provided that your thermometer can read temperature perfectly.

But the 3rd law of thermodynamics says that you cannot reach absolute zero, you can reach 0.000000000000000000000000001K but you can never reach 0K.

[Johnny5]

5614 said:

But the 3rd law of thermodynamics says that you cannot reach absolute zero, you can reach 0.000000000000000000000000001K but you can never reach 0K.

Do you mean Nernst's theorem?

[5614]

The third law of thermodynamics was developed by Walther Nernst and is sometimes referred to as Nernst's theorem - they are the same thing.

[Martin]

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Absolute zero, provided that your thermometer can read temperature perfectly.

If you were to put that very same thermometer around our location, then it will read 2.7 degree background radiation, but we are located within the sphere of explosion of Big Bang. But, exterior to that explosion, there is true vacuum.

With that firmly in mind, there can't be any radiation there, whence I say your thermometer would read zero.

the standard picture is the CMB temp is 2.7 kelvin throughout all space.

the Big Bang is not imagined to be an "explosion" of material (you get words suggesting that in popular non-mathematical accounts because it gives the readers an image to put in their minds)

so there is no way to go "outside the sphere of the big bang"

big bang refers to an expanding space model that is the predominant standard picture among working cosmologists, it comprises all of space
and the CMB fills all space (in this prevailing standard model)

J5 the picture you are giving, of an explosion of material that you could get outside of, is very much a personal vision of your own. You should probably preface it by letting people know that.

In the conventional cosmology picture, the CMB used to be around 3000 kelvin, the radiation consisted of highfrequency short wavelength photons (rather like sunlight but a bit redder)
the CMB has since COOLED DOWN A THOUSAND-FOLD because the space thru which the photons are traveling has expanded 1000-fold and made their wavelengths expand out 1000-fold.
actually the figure is estimated to be 1100, not 1000

Now all those professional cosmologists could be wrong! And you, J5, could be right! that is logically possible. but it would be nice of you J5 to let people know that you are presenting a personal vision that is totally different from the conventional picture.

[Johnny5]

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J5 the picture you are giving, of an explosion of material that you could get outside of, is very much a personal vision of your own. You should probably preface it by letting people know that.

You are absolutely right Martin. But you know, it's not possible for space to be expanding though. I don't think that doubling the amount of words for things is exactly right either. I will think about it, and change the way I discuss big bang in the future.

Standard Model

Supermass explosion model.

There you go. ;)

Regards

PS: You know what Martin, I'm not sure the models are all that different though. I personally do envision the early universe as having all the material which is currently dispersed, centered around what is now the center of mass of the universe, forming a single body, surrounded by an infinite vacuum.

I believe part of the standard model, is that space did not exist, hence neither did matter at the big bang singularity. Doesn't creation ex nihilo contradict something somewhere somehow?

At any rate, my question would just be, does the standard model also have a logical mechanism for matter explosion as well?

[Johnny5]

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the Big Bang is not imagined to be an "explosion" of material (you get words suggesting that in popular non-mathematical accounts because it gives the readers an image to put in their minds)

You know what, lets do something which will be constructive for me.

In the standard Big Bang model, if space didn't exist at the first moment in time, then matter didn't exist at the first moment in time.

Then later, space existed, and matter was where exactly?

Thank you Martin

[Johnny5]

5614 said:

The third law of thermodynamics was developed by Walther Nernst and is sometimes referred to as Nernst's theorem - they are the same thing.

Yes they are the same thing. Can you state Nernst's theorem?

[Martin]

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At any rate, my question would just be, does the standard model also have a logical mechanism for matter explosion as well?

No, there is no mechanism for pushing matter apart.

that is, no physicist or cosmologist that I know of has ever speculated about a matter-type explosion or proposed any mechanism

because the big bang theorists have never contemplated a matter-type explosion, they have always had in mind an expansion of space (for which we have a good clear mechanism called Gen Rel)

since gen rel was invented in 1915, and the specialized friedmann version of it that applies to cosmology, in 1922, the picture has always been that matter just sits still (and attracts itself together somewhat) and is carried apart by expanding space----one can put this more abstractly in terms of the time-varying metric, so dont think of it as if space were a material.

of course the matter in the early U is hot and so it is doing its random whizzing about and creating and annihilating and all the usual high energy stuff, but on average it does not go anywhere, it is just gently carried apart by the expansion

the fundamental reason people (scientists) accept this is because Gen Rel is phenomenally accurate in predicting stuff and no other theory of gravity can match it-----many people have tried to go better on einstein, and failed.

and if you accept Gen Rel then the only solutions are ones where there was no matter explosion but space itself is either expanding or contracting. there is no steadystate stable solution to the Gen Rel equation (and this is the equation that is so successful in predicting experimental measurement)

it's simple. either you have to fight einstein out at the 7th or 8th decimal place (where he is predicting orbits of pairs of pulsars, a kind of neutron star which astronomers observe very accurately over decades, and you fight him where he is predicting tiny deviations in the atomic clocks carried by GPS satellites) or you have to accept that space (or if you prefer, the metric) can expand

(that is that distances can increase in a systematic way, there is no assumption that space is in any way material, it is more abstract: the metric that describes space can change with time and the distance-readings taken from this metric can increase with time)

[Johnny5]

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No, there is no mechanism for pushing matter apart.

that is, no physicist or cosmologist that I know of has ever speculated about a matter-type explosion or proposed any mechanism

because the big bang theorists have never contemplated a matter-type explosion, they have always had in mind an expansion of space (for which we have a good clear mechanism called Gen Rel)

since gen rel was invented in 1915, and the specialized friedmann version of it that applies to cosmology, in 1922, the picture has always been that matter just sits still (and attracts itself together somewhat) and is carried apart by expanding space----one can put this more abstractly in terms of the time-varying metric, so dont think of it as if space were a material.

of course the matter in the early U is hot and so it is doing its random whizzing about and creating and annihilating and all the usual high energy stuff, but on average it does not go anywhere, it is just gently carried apart by the expansion

the fundamental reason people (scientists) accept this is because Gen Rel is phenomenally accurate in predicting stuff and no other theory of gravity can match it-----many people have tried to go better on einstein, and failed.

and if you accept Gen Rel then the only solutions are ones where there was no matter explosion but space itself is either expanding or contracting. there is no steadystate stable solution to the Gen Rel equation (and this is the equation that is so successful in predicting experimental measurement)

it's simple. either you have to fight einstein out at the 7th or 8th decimal place (where he is predicting orbits of pairs of pulsars, a kind of neutron star which astronomers observe very accurately over decades, and you fight him where he is predicting tiny deviations in the atomic clocks carried by GPS satellites) or you have to accept that space (or if you prefer, the metric) can expand

(that is that distances can increase in a systematic way, there is no assumption that space is in any way material, it is more abstract: the metric that describes space can change with time and the distance-readings taken from this metric can increase with time)

This was a wonderful answer, which will take me sometime to digest, but certainly appropriate to give to any person who doesn't know GR.

Setting your response aside, which is going to require some time to digest. You make the predictions of GR seem formidable.

Let me ask you this...

I can easily conceive of a grenade exploding.

I can also conceive of a star exploding, say a Red Giant, then later a supernova.

This happens all the time, in our current universe.

Why oh why, can't the universe have started off as a matter explosion, into pure vacuum, not unlike a supernova, and the distance increase is just the centers of inertia of the shrapnel obeying the law of physics, which is that things move in a straight line at a constant speed, unless acted upon by an external force?

[Martin]

Johnny5 said:

Why oh why, can't the universe have started off as a matter explosion, into pure vacuum, not unlike a supernova, and the distance increase is just the centers of inertia of the shrapnel obeying the law of physics, which is that things move in a straight line at a constant speed, unless acted upon by an external force?

according to what law of gravity would the pieces of shrapnel slow down?
if newtonian gravity, it is not accurate
what you call "obeying the law of physics" is not a true fact
unless you accept the curved (expanding or contracting) space of gen rel

what do you mean by "in a pure vacuum"? I suppose you have Euclidean 3space in mind. It is not accurate. it does not exist in nature. things do not follow the "straight lines" of euclidean space.

the picture is too full of models that are only approximately right
(satisfied the likes of newton, and highschool teachers, but not people who measure carefully)

[swansont]

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I can easily conceive of a grenade exploding.

I can also conceive of a star exploding, say a Red Giant, then later a supernova.

This happens all the time, in our current universe.

Why oh why, can't the universe have started off as a matter explosion, into pure vacuum, not unlike a supernova, and the distance increase is just the centers of inertia of the shrapnel obeying the law of physics, which is that things move in a straight line at a constant speed, unless acted upon by an external force?

Nature is under no obigation to behave according to what you (or anyone else) can understand.

[Rekkr]

Absolute zero. 0 degrees Kelvin or -273 degrees Celsius.