Fifty years ago today, Apollo VIII brought us to the moon for the first time ever.

[mordorbund]

4 hours ago, unixknight said:

I've been wondering that  myself since, as I mentioned, space isn't cold.

Only a fool contradicts Kahn!

 

[unixknight]

3 minutes ago, mordorbund said:

Only a fool contradicts Kahn!

You know, I was just mentioning that very example in a conversation last night.  This is a trope that a LOT of sci-fi gets wrong.  When sci-fi gets it right however... it's awesome.  

[Traveler]

4 hours ago, unixknight said:

From Sunday's lesson:

Matthew 19:21 Jesus said unto him, If thou wilt be perfect, go and sell that thou hast, and give to the poor, and thou shalt have treasure in heaven: and come and follow me.

What's your take on this?  Sounds like the Lord finds monetary donations to be worthy to me.

As members of the Church - we need to understand that Charity is "The Pure Love of Christ".   Giving money to the poor can be a good thing, it can be a noble thing, it can be a compassionate thing and it could be a kind thing.  But if someone is give to Charity - they must follow Jesus Christ.  That is more than giving (especially money) to those in need.  If anyone can show me where Jesus Christ gave money to someone in need - then I stand corrected.  If we are interested in charity the operative notion in Matt 19:21 is that they follow Christ.

 

The Traveler

[unixknight]

1 minute ago, Traveler said:

As members of the Church - we need to understand that Charity is "The Pure Love of Christ".   Giving money to the poor can be a good thing, it can be a noble thing, it can be a compassionate thing and it could be a kind thing.  But if someone is give to Charity - they must follow Jesus Christ.  That is more than giving (especially money) to those in need.  If anyone can show me where Jesus Christ gave money to someone in need - then I stand corrected.  If we are interested in charity the operative notion in Matt 19:21 is that they follow Christ.

Ok, so we agree that giving money to the poor can be noble.  That's the point I've been making.  Now, you seem to be using 'Charity' in a slightly different way than most, and it helps that you capitalized it to draw attention to it.  

As to whether giving money, in general, is 'Charity' in the way you use it, I don't know if I agree or not since I don't generally use the term in the same way you seem to.

So in short, maybe this is a good place to leave it?  Unless I've misrepresented something here.

[Guest]

6 hours ago, unixknight said:

I've been wondering that  myself since, as I mentioned, space isn't cold.  A vacuum cannot have a temperature, by definition.

Depends on your definition of "temperature".  And even in physics, there are a couple that come to mind.  I'm sure there are more.

[unixknight]

31 minutes ago, Carborendum said:

Depends on your definition of "temperature".  And even in physics, there are a couple that come to mind.  I'm sure there are more.

What definition makes space, an empty void which has no matter in it, have temperature, a property of matter?

[Guest]

3 hours ago, unixknight said:

What definition makes space, an empty void which has no matter in it, have temperature, a property of matter?

I'll answer this question with the following disclaimer.  My physics professor that taught temperature said,

Quote

In common language, we know what temperature is.  We deal with it every day.  But in physics, we truly have a hard time defining what temperature actually is.  Once we think we have a clear definition, we come across a scenario where it doesn't seem quite right.  Yet, we have to have some working definitions.  And we have many.  Each one for the specific measurement we're concerned with.

DEFINITION 1:

One definition of temperature of a gas is known as "gas kinetic temperature" ("mean kinetic temperature" applied to a gas).  This is often considered a useless metric.  But in some instances it is the primary metric that is observable.

It essentially means that gas particles have a certain amount of kinetic energy given an STP (Standard Temperature & Pressure) environment.  Then it stands to reason that a single average molecule in that mass of gas would have that same kinetic energy even if it were moving around by itself.  So, if that same molecule were moving around in a vacuum, that molecule could be said to have a "gas kinetic temperature" equal to the temperature of a group of molecules with the same kinetic energy in an STP environment.  It is basically an extrapolation of the ideal gas law to the extreme.

As such, the single particle can be considered to have a very high temperature.  But the total energy of a single molecule is near nothing.  So, we have molecules in the upper atmosphere have a gas kinetic temperature of 1000K.  Yet people would freeze rather than burn up -- if left unprotected -- because there are so few molecules up there that a body would not be warmed by that air. Paradox,

On the surface of the moon, we have almost the same number of air particles as the very limits of our atmosphere. (Remember, even the vacuum of space has trace amounts of gas in it).

DEFINITION 2: Same as above, with a different perspective.

Now forget that such a thing as "gas kinetic temperature" exists.  Imagine that temperature is a measure of the TOTAL kinetic energy of the system of particles (which is what we're used to thinking about).  We have some magic way of measuring it.  Now stick that magic thermometer into the vacuum.  How much energy is there?  Zero. (neglect background radiation which would make everything about 3K).

By either of these definitions, the temperature of a vacuum could be considered zero or it could be considered "undefined".  Truly, the math would give you 0 divide by 0 (undefined).  However, the graph of a scatter chart would gradually point to a limit of zero, even if we'd have an empty circle at the origin.

Edited January 8, 2019 by Guest

[unixknight]

11 hours ago, Carborendum said:

I'll answer this question with the following disclaimer.  My physics professor that taught temperature said,

DEFINITION 1:

One definition of temperature of a gas is known as "gas kinetic temperature" ("mean kinetic temperature" applied to a gas).  This is often considered a useless metric.  But in some instances it is the primary metric that is observable.

It essentially means that gas particles have a certain amount of kinetic energy given an STP (Standard Temperature & Pressure) environment.  Then it stands to reason that a single average molecule in that mass of gas would have that same kinetic energy even if it were moving around by itself.  So, if that same molecule were moving around in a vacuum, that molecule could be said to have a "gas kinetic temperature" equal to the temperature of a group of molecules with the same kinetic energy in an STP environment.  It is basically an extrapolation of the ideal gas law to the extreme.

As such, the single particle can be considered to have a very high temperature.  But the total energy of a single molecule is near nothing.  So, we have molecules in the upper atmosphere have a gas kinetic temperature of 1000K.  Yet people would freeze rather than burn up -- if left unprotected -- because there are so few molecules up there that a body would not be warmed by that air. Paradox,

On the surface of the moon, we have almost the same number of air particles as the very limits of our atmosphere. (Remember, even the vacuum of space has trace amounts of gas in it).

DEFINITION 2: Same as above, with a different perspective.

Now forget that such a thing as "gas kinetic temperature" exists.  Imagine that temperature is a measure of the TOTAL kinetic energy of the system of particles (which is what we're used to thinking about).  We have some magic way of measuring it.  Now stick that magic thermometer into the vacuum.  How much energy is there?  Zero. (neglect background radiation which would make everything about 3K).

By either of these definitions, the temperature of a vacuum could be considered zero or it could be considered "undefined".  Truly, the math would give you 0 divide by 0 (undefined).  However, the graph of a scatter chart would gradually point to a limit of zero, even if we'd have an empty circle at the origin.

(Apologies for the length of my reply here.  I just really  love talking about this stuff.  I don't mean to be obnoxious.  😊)

All of that is great, but doesn't provide any utility in a practical sense.  What I mean by that is this:  If you and I were to sit down together to design a spacecraft, one of the factors we'd have to consider is temperature regulation.  Will we need to insulate the ship against hot or cold?  Will we need to paint the ship in light or dark colors (to either reflect or absorb sunlight)?  Will we need to include heating or cooling systems?  

It is inaccurate to say "Space is cold."  It is much more correct to say "Objects in space will eventually become cold."  Now THAT is true, with the lower temperature limit being a function of proximity to other sources of radiation.  If I  take a baseball and place it in the intergalactic void, it's going to get REALLY close to absolute zero.  If I take the same baseball and toss it into a solar orbit at about the same altitude as the Earth, it'll stabilize at a much higher temperature.   

Remember that the ONLY mechanism for transferring heat in a hard vacuum like space is radiation.  So going back to our spacecraft project, we know our ship will radiate heat.  Do we want to minimize that or maximize it?  Let's take a look at a couple of real life examples.

The interior of the Apollo 13 Command and Lunar modules during its trip around the Moon and back were depicted as becoming so cold that one of the astronauts was able to  tap a frozen hot dog against a piece of equipment to demonstrate how cold it had become inside the spacecraft.  Now, in real life it didn't get quite that cold, but still we can go with it because it's close.  

Was the ship insulated against heat or cold?  Neither.  Apollo Command Modules were "in some places, not much thicker than a couple of sheets of aluminum foil."  According to Jim Lovell.  That doesn't sound very insulating to me.  Instead, the ship was designed to radiate as much heat as possible while reflecting away sunlight.

Not absorbing a lot of warmth from the Sun, that.

The thing is, the inside of the spacecraft could get pretty hot.  There were computers, fuel cells and other equipment that generated a good bit of waste heat.  I don't know this for a fact, but I bet the heaters were run using that waste heat.  (That's how cars do it, anyway.)  The rest of the heat had to be radiated away.  Even in a spacecraft designed specifically to radiate heat, it took 2 days to go from room temperature to near freezing, and that's with the ship being on the side of the Moon opposite the Sun for a while. 

The new generation of space suits being designed are like body glove suits, using the tension of the fabric to compensate for the lack of pressure, instead of the balloon-like spacesuits in use now.  The problem they're trying to solve is cooling, since the wearer gets REALLY hot in that thing really fast.

[Guest]

10 hours ago, unixknight said:

(Apologies for the length of my reply here.  I just really  love talking about this stuff.  I don't mean to be obnoxious.  😊)

No worries.  I can use the diversion.  I'm getting pretty stressed with reality at the moment.

10 hours ago, unixknight said:

All of that is great, but doesn't provide any utility in a practical sense. 

That's kind of what I said.  But it really does depend on what aspect of "temperature" you're trying to analyze.

10 hours ago, unixknight said:

It is inaccurate to say "Space is cold."  It is much more correct to say "Objects in space will eventually become cold."  Now THAT is true, with the lower temperature limit being a function of proximity to other sources of radiation.  If I  take a baseball and place it in the intergalactic void, it's going to get REALLY close to absolute zero.  If I take the same baseball and toss it into a solar orbit at about the same altitude as the Earth, it'll stabilize at a much higher temperature.   

Well, you're only looking at radiation now.  And that's not the only source of heat on the surface of the moon.

10 hours ago, unixknight said:

Remember that the ONLY mechanism for transferring heat in a hard vacuum like space is radiation.  So going back to our spacecraft project, we know our ship will radiate heat.  Do we want to minimize that or maximize it?  Let's take a look at a couple of real life examples.

Are we talking about floating in space, or on the surface of the moon?  Communion, Aldrin, remember?

10 hours ago, unixknight said:

The interior of the Apollo 13 Command and Lunar modules during its trip around the Moon and back were depicted as becoming so cold that one of the astronauts was able to  tap a frozen hot dog against a piece of equipment to demonstrate how cold it had become inside the spacecraft.  Now, in real life it didn't get quite that cold, but still we can go with it because it's close. 

It didn't get to 32 deg F or colder?  I could actually see that happening.  I'm not sure.  I haven't looked it up.  But it is plausible.

10 hours ago, unixknight said:

Was the ship insulated against heat or cold?  Neither.  Apollo Command Modules were "in some places, not much thicker than a couple of sheets of aluminum foil."  According to Jim Lovell.  That doesn't sound very insulating to me.  Instead, the ship was designed to radiate as much heat as possible while reflecting away sunlight.

Not absorbing a lot of warmth from the Sun, that.

Half true.

Foil would reflect solar radiation away from the craft.  But it would also prevent radiation FROM the craft.  Remember, a black body is a perfect radiator.

[unixknight]

17 hours ago, Carborendum said:

That's kind of what I said.  But it really does depend on what aspect of "temperature" you're trying to analyze.

I'm really not looking to analyze any aspect of it.  We have a practical understanding of temperature that we use in 99% of conversations outside a laboratory.  That's where I"m at.

17 hours ago, Carborendum said:

Well, you're only looking at radiation now.  And that's not the only source of heat on the surface of the moon.

Is there another significant source?

17 hours ago, Carborendum said:

Are we talking about floating in space, or on the surface of the moon?  Communion, Aldrin, remember?

I've been making generalized statements about space.  So, the former.  

17 hours ago, Carborendum said:

It didn't get to 32 deg F or colder?  I could actually see that happening.  I'm not sure.  I haven't looked it up.  But it is plausible.

Yeah I believe it got down to the neighborhood of like 36 or 39... so close enough for our purposes but if we wanted to be technical it wasn't freezing temperatures.

17 hours ago, Carborendum said:

Half true.

Foil would reflect solar radiation away from the craft.  But it would also prevent radiation FROM the craft.  Remember, a black body is a perfect radiator.

Foil would.  The CSM wasn't made of foil.  When I went to look up what, exactly it was made of, I discovered I was mistaken earlier when I described it as being thin and uninsulated.  It was indeed as thin as .25 inches in places, but that was the inner pressure shell.  Between that and the outer shell there was indeed insulation, to protect against heat.  (presumably because even as shiny and polished as it was, the outer shell was exposed to direct sunlight which would heat it, albeit slowly.  This is why the ship had to occasionally do the "barbecue roll" to keep from having the same side always facing the Sun.)  The outer shell was made from steel.  From Wikipedia:

Quote

The outer structure was made of stainless steel brazed honeycomb brazed between steel alloy face sheets. It varied in thickness from 0.5 inch to 2.5 inches. Part of the area between the inner and outer shells was filled with a layer of fiberglass insulation as additional heat protection.

 

Edited January 9, 2019 by unixknight

[Guest]

1 hour ago, unixknight said:

I'm really not looking to analyze any aspect of it.  We have a practical understanding of temperature that we use in 99% of conversations outside a laboratory.  That's where I"m at.

That is exactly why I began this whole thing with that quote from my physics professor.  If you're just talking about vague concepts and what we generally feel and are familiar with, then you can't talk about the physics behind it.  Because, guess what?  We don't "feel" the physics of thermal transfer in outer space.  We're totally unfamiliar with it.  The rules that physics have discovered are not the same as what we're familiar with when we're in an alien environment.  It behaves in a different manner than the simple common knowledge rules we think of on earth.

1 hour ago, unixknight said:

Is there another significant source?

Well, let's see.  What GIANT MASS around there has any kind of thermal properties?

1 hour ago, unixknight said:

I've been making generalized statements about space.  So, the former.  

Then you're moving the goalposts.

1 hour ago, unixknight said:

Yeah I believe it got down to the neighborhood of like 36 or 39... so close enough for our purposes but if we wanted to be technical it wasn't freezing temperatures.

Like I said, I don't know the actual record of that purported event.

1 hour ago, unixknight said:

Foil would.  The CSM wasn't made of foil.  When I went to look up what, exactly it was made of, I discovered I was mistaken earlier when I described it as being thin and uninsulated.  It was indeed as thin as .25 inches in places, but that was the inner pressure shell.  Between that and the outer shell there was indeed insulation, to protect against heat.  (presumably because even as shiny and polished as it was, the outer shell was exposed to direct sunlight which would heat it, albeit slowly.  This is why the ship had to occasionally do the "barbecue roll" to keep from having the same side always facing the Sun.)  The outer shell was made from steel.  From Wikipedia:

OK.  So, what was it you were trying to get at with the outer surface?  And what does this have to do with it?

I thought your point was that the highly reflective surface made it so that it both reflected and radiated well.  My point was that it did not radiate well, only reflected well.  What was your point?

[unixknight]

17 minutes ago, Carborendum said:

That is exactly why I began this whole thing with that quote from my physics professor.  If you're just talking about vague concepts and what we generally feel and are familiar with, then you can't talk about the physics behind it.  Because, guess what?  We don't "feel" the physics of thermal transfer in outer space.  We're totally unfamiliar with it.  The rules that physics have discovered are not the same as what we're familiar with when we're in an alien environment.  It behaves in a different manner than the simple common knowledge rules we think of on earth.

People going by "simple common knowledge rules we think of on earth" is exactly the problem.  People talk about space as if the environment itself were cold.  Now, if you want to argue that it is, and start talking about the energy of individual gas molecules, then from where I sit that feels more like trying to come up with a way to justify saying the opposite.  I'm making a very simple statement that isn't inaccurate just because I'm not being hypertechnical.  Space is not a cold environment.  Every single spacecraft and space suit designed in the history of the world demonstrates that the challenge for regulating the temperature inside is not about keeping the occupants warm, but rather keeping them cool due to:

• Internal sources of heat, like the human body or fuel cells
• External sources of thermal radiation like the Sun

I'm interested in a practical discussion of these things, not a gotcha game.

17 minutes ago, Carborendum said:

Well, let's see.  What GIANT MASS around there has any kind of thermal properties?

I am going to assume that wasn't intended to talk to me like I'm stupid.

Of course the surface of the moon has temperature.  It has mass, therefore it has the property of temperature.  If an astronaut is standing on it, then there are two ways in which heat is exchanged between him and the surface:

• By conduction through the soles of his feet. 
• By radiation

Neither of which is going to affect an object held in his hand in a short amount of time.  My point still remains the same, even applied to the surface of the Moon.  

Note in the illustration below that the backpack contains a cooling unit, not a heater.  Furthermore, notice the tubing which carries coolant.

 

31 minutes ago, Carborendum said:

Then you're moving the goalposts.

How am I moving the goalposts, exactly?

32 minutes ago, Carborendum said:

Like I said, I don't know the actual record of that purported event.

I know... which is why I was trying to let you know what I read, in a friendly way.  Is there some reason you seem to be assuming that every single thing I say must be some kind of argument?

33 minutes ago, Carborendum said:

OK.  So, what was it you were trying to get at with the outer surface?  And what does this have to do with it?

I thought your point was that the highly reflective surface made it so that it both reflected and radiated well.  My point was that it did not radiate well, only reflected well.  What was your point?

I said: "Was the ship insulated against heat or cold?  Neither.  Apollo Command Modules were "in some places, not much thicker than a couple of sheets of aluminum foil."  According to Jim Lovell.  That doesn't sound very insulating to me.  Instead, the ship was designed to radiate as much heat as possible while reflecting away sunlight."

(As I already said, I was mistaken about the lack of insulation, but the point remains that the ship was designed to get rid of waste heat and avoid being heated by solar radiation, not keep the crew warm.) 

Then, you said:  

"Half true.

Foil would reflect solar radiation away from the craft.  But it would also prevent radiation FROM the craft.  Remember, a black body is a perfect radiator."

(Which I found irrelevant, since neither I nor Jim Lovell ever said that foil was radiating anything.  The only mention of foil was a comment about the thickness of the spacecraft's inner shell.  You're the one who brought up the question of how it radiates.)

To which I responded:

"Foil would.  The CSM wasn't made of foil.  When I went to look up what, exactly it was made of, I discovered I was mistaken earlier when I described it as being thin and uninsulated.  It was indeed as thin as .25 inches in places, but that was the inner pressure shell.  Between that and the outer shell there was indeed insulation, to protect against heat.  (presumably because even as shiny and polished as it was, the outer shell was exposed to direct sunlight which would heat it, albeit slowly.  This is why the ship had to occasionally do the "barbecue roll" to keep from having the same side always facing the Sun.)  The outer shell was made from steel. "

(To clarify what the outer shell WAS made of as well as acknowledge my earlier error on insulation.)

Clearer?

[Guest]

@unixknight,

You're beginning to go all over the board.  I can't follow you anymore.  Sorry.