When you eat a sandwich in space flight, does your craft lose mass?

Originally posted by Illustronic

But the inside heats the outside that loses heat and that's why there is thermal protection, so heat/energy is not mass?

Heat loss occurs on Earth because thermal energy is transferred between the molecules of a material (like the wall of a house) and those of a surrounding medium (like the air outside). But, in a spacecraft, there is no medium outside for thermal energy to escape to. Therefore, there is no heat loss from inside the craft.
The only potential heat loss is the "heat" associated with radioactive decay, such as that which powers the battery on New Horizons.

no matter how small the loss is heat energy has mass and when the heat is lost into space there is still a loss of mass. all be it a very small amount of mass but it is still a loss. i`m no physicist but i`m pretty sure everything has mass no matter how small with the exception of some crazy massless things coming out of the Large Hadron Colider that i cant even begin to understand

reply to post by CLPrime


Funny stuff, thanks for the joviality. We do come to the question of if energy and heat is mass though. There is that pesky E=MC2 thing, and the bomb works to prove the theory, is real. The spacecraft does lose heat to cold space, it expends energy to keep heat in the craft.

Lets disregard propulsion and just consider unpowered cruse in space. It should be measurable that the craft loses mass during cruse, also disregarding micrometeorite impacts. A pure physics and biological, lets call it, curiosity, for lack of better terms, an exercise in physical math.

After I posted this I saw someone mention the bodily use of contained mass, starvation. Like a mountain climber that doesn't piss for two days but continues to consume water during the climb. Perspiration would release enough of that water the body didn't turn to waste. I mean there is a discharge of mass even when you breath. Should equal the mass consumed. The bodily heat is pure energy discharge and I wonder if it has weight/mass.

reply to post by James1982


Most of that mass is lost through dehydration, in which water is expended and passed from the body. In extreme starvation, muscle is "eaten" by the body for energy, and any waste from that would be gotten rid of in the usual way. Usually, though, muscle will be broken down into its constituent nutrients, and these will be used for energy, so there will be very little waste (if any) from the breaking down of muscle tissue.

Originally posted by CLPrime

Originally posted by Illustronic

But the inside heats the outside that loses heat and that's why there is thermal protection, so heat/energy is not mass?

Heat loss occurs on Earth because thermal energy is transferred between the molecules of a material (like the wall of a house) and those of a surrounding medium (like the air outside). But, in a spacecraft, there is no medium outside for thermal energy to escape to. Therefore, there is no heat loss from inside the craft.
The only potential heat loss is the "heat" associated with radioactive decay, such as that which powers the battery on New Horizons.

Ok so what about the sun or do we imagine the heat from it

Originally posted by James1982
I understand that mass is not lost, but a simple question here.

Say a person is starving, and they loose 20lbs while they are starving. Where does that mass go? If someone hasn't eaten anything for 2 weeks they can't be pooping out 20lbs of waste? Where is all that fat and muscle going if it's not being consumed and turned into heat/energy?

Yes, they do poop (or vomit) out close to 20lbs... also a lot of it is lost as water in the form of sweat and water vapor in our breath, etc. More of it is lost as dander and hair falling out.

Originally posted by CLPrime

Originally posted by Illustronic

But the inside heats the outside that loses heat and that's why there is thermal protection, so heat/energy is not mass?

Heat loss occurs on Earth because thermal energy is transferred between the molecules of a material (like the wall of a house) and those of a surrounding medium (like the air outside). But, in a spacecraft, there is no medium outside for thermal energy to escape to. Therefore, there is no heat loss from inside the craft.
The only potential heat loss is the "heat" associated with radioactive decay, such as that which powers the battery on New Horizons.

Actually, heat is lost in space in the form of infrared radiation. That is why we thermally insulate satellites.

reply to post by BinaryG


Heat from the sun is in the form of EM radiation.

reply to post by rogerstigers


You might not believe it, but I was including that in radioactive decay, as it's heat loss through the expending of radiation.

reply to post by CLPrime


do you agree that radiation has mass?

I wouldn't think so, I mean, the sandwich is still there in some form after all.
Maybe when he visits the bathroom (do they eject it? I wouldn't think so)

Originally posted by Illustronic

The bodily heat is pure energy discharge and I wonder if it has weight/mass.

edit on 12-8-2011 by Illustronic because: (no reason given)

Infrared energy, a wavelength of light, is effected by gravity so to my simple mind it must have some mass

reply to post by BinaryG


No, I don't. Electromagnetic radiation is massless. When it's the result of radioactive decay, however, that radiation represents the conversion of some amount of mass into energy. That is how mass is released, in this case.

I guess if I understand correctly, it would be like a 9v battery, when the energy is drained, the battery stays the same weight as if fully charged, so the eating of the sandwich would be the same as the charging of a battery, energy is converted but no weight is lost? Does that make sense? Am I understanding it?

reply to post by Darkblade71


That makes sense to me.

reply to post by rogerstigers


Yes, a spacecraft must get to be a messy place if a ventilation problem occurs. But in microgravity we observe another phenomena that supports the ToR and basic gravitational thermodynamics. That bodies in the vacuum of space attract, and in microgravity the bodies themselves would defeat the gravitational attraction of a distant larger body and attract each other, if the distance is right. I suspect the human 'dander' attaches itself to the walls and floors and ceilings of the ISS before it just floats around endlessly, but I suppose some time elapses before the dust settles so to speak. I do suppose a liquid spill on the ISS eventually attaches itself to the container walls also. So cleaning may not be as big of an issue as I first thought.

The earth gravity on the ISS is still the strongest force for dander, I suspect most land on the floor if the floor is closer to the earth, to them it really doesn't matter, once dander is attached to a wall earth gravity wouldn't move it from there, hence, microgravity.

A better sandwich would matter more, maybe with some special sauce, messy is tastier.

reply to post by CLPrime


Are you sure? Apollo 13 got really cold inside. One of the main threats to life support other than the immediate obvious.

reply to post by Illustronic


The answer is no

reply to post by Illustronic


The Apollo craft would have radiated heat in the form of EM radiation.

when you post on ATS,
does your brain lose mass?

OK, I see I'm being humiliated, so on with our regularly scheduled thread topics. We have reached that point (a while ago) that makes this thread stupid. Something I am acquainted with.