[Martin]

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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...

Unfortunately you cannot do that. You would have to exit from the universe, and get out of space itself. And then you would not be measuring the temperature of space.
You can't get out of range of the big bang because space expanded from the big bang (the BB is best not thought of as a material explosion).
As long as you are anywhere in space, you will be touched by some energy, at the least by the long wavelength light of the microwave background. you would have to stop existing, in order to get out of space itself, and
the threadstarter asked WHAT TEMPERATURE IS SPACE?

according to the standard picture in cosmology, all space is filled with the cosmic microwave background. the temperature of (darkest possible coldest possible) space is the same as the temperature of the CMB

Rekkr said:

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

Rekkr please, what reason can you have to say a thing like that?
did you read post #2 in the thread, the NASA link?

the temperature of space was measured around 1990 very accurately by the COBE satellite. I am proud to say that at the moment I am just a few blocks away from where one of the directors of COBE, George Smoot, has his office.

they got it accurate to within maybe 4 decimal places, they mapped minor variations in the temperature, when COBE team delivered its findings to astronomical association they got a rare standing ovation. it was an historic step in astronomy----first accurate map of CMB sky temperature

the temperature of space is not zero kelvin
you cannot get out the CMB unless you get out of space itself (which I guess means entirely cease to exist)

[onemind]

First, a big thanks to everyone. This thread has really changed the way i think about the universe. There have been alot of great theories mentioned in this post. Well, off to the library to read up on cosmology :-) Anyone know any good non math lay people books on the subject?

I have my own view of where the universe is located. Now I know you are all a bunch of hardcore scientists and the mere mention of anything remotely religious makes your skin crawl but I'll throw it out there just for the hell of it.
If you turn off your sense of sight where is the universe? If you then turn off your sense of hearing, taste, touch and smell what is left? Only mind. Mind without objects. Except for thought. Now turn thought off. Only pure mind is left. No universe. Nothing to measure. Way back when the universe first started to expand, before the human race and animals ,whether by an expansion of matter in an infinte vacuum or by the very expansion of space itself, what was there to witness it? If there were no obserservers, was it there?
Is it not possible this very expansion happened in the mind? And that all that exists is mind made? The buddha said not to belive anything but to find out for yourself. Since I have no direct experience with it i cant believe it. just another spin on things :-)

Who knows. :rolleyes:
Thanks again :-)

[Martin]

onemind said:

First, a big thanks to everyone. This thread has really changed the way i think about the universe.

reciprocal thanks from here back to you----that was a great question to ask! lots of angles. lots of discussion

[J.C.MacSwell]

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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)

)

Steady State Models can account for GR. The Hoyle model used "continuous creation" to fill in the ever increasing "void" of space-time.

It could not reasonably explain the CMB, though there may be other reasons as well that it fell out of favour.

[Martin]

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Steady State Models can account for GR. The Hoyle model used "continuous creation" to fill in the ever increasing "void" of space-time.

It could not reasonably explain the CMB, though there may be other reasons as well that it fell out of favour.

I wonder if the nightsky darkness had anything to do with dooming steady state

[J.C.MacSwell]

Martin said:

I wonder if the nightsky darkness had anything to do with dooming steady state

Not the Hoyle Model. A Horizon would be maintained by the "Hubble flow" (and in this case the Hubble constant really was "constant")

[Martin]

J.C.MacSwell said:

Not the Hoyle Model. A Horizon would be maintained by the "Hubble flow" (and in this case the Hubble constant really was "constant")

I see! Interesting to look at these old models.
since the Hubble parameter was constant, the Hubble radius could not go roaring out into space the way it has been doing
so light from any galaxy receding at speed c or better would never reach us. the Hubble radius was constant and therefore acted as a bound on the observable universe. So in that steadystate model the night sky could be dark!

fascinating. and then our own hubble volume of space would tend to get emptier and emptier, so hoyle had to postulate something that kept replenishing it, the constant creation of atoms out there in the void.

I guess the "steady state" school of cosmologists are getting pretty old now. I saw a news item about the passing of one of the founders of that model, just last week I think.

[Skye]

Considering that there's very little in space, and so there's minimal heat exchange, would it then feel nice and warm (body temp.)?

[Martin]

Skye said:

Considering that there's very little in space, and so there's minimal heat exchange, would it then feel nice and warm (body temp.)?

I believe that in the shade the problem would be dumping waste heat from your body. but maybe it is not too bad.
maybe you need to vent expendable gas to carry off heat,
or you need something like a heatpump and a radiator surface to radiate it away. or an even larger radiator surface with no heat pump

I am just guessing

If you were not in the shade the problem would be much worse because of sunlight

maybe someone familiar with manned space program engineering knows definitely?

[swansont]

Skye said:

Considering that there's very little in space, and so there's minimal heat exchange, would it then feel nice and warm (body temp.)?

There's radiation heat transfer. Since you're radiating to a 2.7 K background, and it's the only game in town, it's significant. Radiation goes as T⁴. You would eventually get cold.

[J.C.MacSwell]

swansont]There said:

4[/sup']. You would eventually get cold.

Inspite of virtually no conduction or convection losses you would freeze your butt in a hurry without adequate protection/spacesuit, would you not?

[swansont]

J.C.MacSwell said:

Inspite of virtually no conduction or convection losses you would freeze your butt in a hurry without adequate protection/spacesuit, would you not?

If I took your question excruciatingly literally, using the equation here, I find that a 90 kg perfect radiatior with a surface area of a square meter would reach freezing in ~1.5 hours, and that ignores the fact that we generate about 100 Watts. A 37 C body with those properties radiates about 525 Watts. Since that is long compared to the time you can hold your breath, I wouldn't worry about literally freezing your butt.

You'd certainly feel extremely chilly, though - we are much more sensitive to heat transfer than we are to temperature. That's why a good heat conductor like metal feels colder than an insulator, like wood, even if they are at the same temperature.

[Johnny5]

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according to what law of gravity would the pieces of shrapnel slow down?
if newtonian gravity, it is not accurate

Let us start out using Newton's formula as a first approximation at least.



Now what is wrong with this?

I expect you to say something about R(t).

[Johnny5]

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maybe someone familiar with manned space program engineering knows definitely?

That is the kind of person I need to speak to. I have some simple questions that someone with that kind of expertise could answer. And NASA should come out with some videos of experiments done in space, for those of us not fortunate enough to go into space.

[J.C.MacSwell]

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I see! Interesting to look at these old models.
since the Hubble parameter was constant, the Hubble radius could not go roaring out into space the way it has been doing
so light from any galaxy receding at speed c or better would never reach us. the Hubble radius was constant and therefore acted as a bound on the observable universe. So in that steadystate model the night sky could be dark!

fascinating. and then our own hubble volume of space would tend to get emptier and emptier, so hoyle had to postulate something that kept replenishing it, the constant creation of atoms out there in the void.

I guess the "steady state" school of cosmologists are getting pretty old now. I saw a news item about the passing of one of the founders of that model, just last week I think.

So what background temperature would the Hoyle Model be?
I don't know if Hoyle looked at it, although he was pretty thorough in a lot of his work which contributed to the big bang models also, even though he didn't believe in them.

Edit: OK, I just read (in "Companion to the Cosmos" by John Gribbin) that Hoyle didn't think that his creation field model would have a background radiation. Anyone have an idea why not? I can't picture that. It seems to me that this model puts a limit on "Olber", not snuff him out.