Reflecting cold

[Roger Chapman]

So something gets heavier (or perhaps lighter) depending how hot it is is a new one on me. Were can I find the details of this certain fact?

[Ian Jackson]

Surely it depends what effect the heat has upon its volume? If it didn't, hot air balloons wouldn't work.

[The Natural Philosopher]

Relativity says that hot things get (incredibly slightly) more massive. As do charged batteries etc.

The same way mass increases with velocity, reaching infinity at C..the slight speedup of molecules in a hot material gives a very slight mass increase.

etc..

[dennis]

He was the one arguing with me when I said the theory of relativity didn't actually say that.

[The Natural Philosopher]

That's because, in fact, it does.

[dennis]

I say its a theory, not fact. I also say that the theory has been revised in the past and will be in the future. To a scientist that means its not fact. Scientists don't have tiny closed minds like you, they accept that if the evidence shows a theory to be wrong, you change it.

[Martin Brown]

However, the theory of relativity and in particular the strong mass energy equivalence principle is well verified despite what all the anti-Einstein nutters and cranks on the internet would have you believe.

A rough handwaving explanation of how tiny the corrections are for modest amounts of energy is given on Wiki:

is for the moment the prevailing orthodoxy and experimentally verified. Close enough to describe as a fact in common parlance, even though scientific theories are always subject to revision as new data becomes available. There is enough data already on this topic to say that "whenever energy is added to a system, the system gains mass".

It is a corollary of the famous E = mc^2 equation.

[The Natural Philosopher]

The point is that it is a fact that the theory says that.

Whether the fact of the indicated mass increase occurs in some 'real world' apart from that detected by instrumentation is a deep philosophical point

Dennis' physics doesn't extend to relativity.

[Martin Brown]

>> Dennis' physics doesn't extend to relativity.

To be fair it isn't often needed for DIY work!

Even today you can still find far to many electronics engineers that do not believe in relativity (IMHO something wrong with the teaching). Denying them access to GPS Satnav would seem like a suitable punishment.

[Dave Liquorice]

Scientists don't deal in facts as they don't exist, all they deal in is theory and probabilty. If observation supports a theory with good repeatabilty then the theory has some element of correctness. The theory then maybe useful for developing further theories or making predictions about how a system will behave under given circumstances. But there is no fact that X will *always* result from starting point Y with conditions Z.

[Ghostrecon]

url:

>>>>>>> Reflecting cold? That's an interesting concept.

the method of heat transfer is not at issue - the body will come to thermal equiibrium by whatever heat transfer mechanism :-)

[Gib Bogle]

Of course. I was just pointing out that the focus on radiant heat is misplaced.

[Roger Chapman]

I really must read up on relativity. I haven't really taken much notice since the sixth form and back in 1960 much of the more readable works on relativity were full of garbage.

How safe is wikipedia of such a serious subject?

And has anyone any suggestions for reading to bone up on modern relativity that is not absolutely stuffed full of mathematics I no longer (or quite possible never did) understand?

We had a lecturer at college who took us through a quick proof of that (which I can no longer remember) before saying that the real proof was a good deal longer and a good deal harder to understand (or words to that effect). My impression at the time was that there was some sort of fallacy involved and ISTR that it wasn't something in a maths lecture but a bit of a diversion by one of the lecturers in engineering.

[dennis]

Would that be the theory of relativity or the special theory of relativity?

The changes are so small you could ignore relativity anyway.

And where does that say that if you increase the energy in a system you increase its mass?

[The Natural Philosopher]

Somewhere around the 'E' bit and the 'm' bit, dennis.

>

[Martin Brown]

Reasonably so. The Young Earth Creationists occasionally take potshots at Geochronology pages and edit the Earths age to Bishop Ushers 6000y but most of the hard sciences and mathematics pages have had sufficient experts look them over to keep them on average in good condition.

Doubtless you can find birthers tweaking Obama's life history to say he is an alien lizard from Venus in a skin suit. But for the most part Wikion science is fairly reliable and the bibliography and links/references to primary literature at major national labs is extremely reliable.

Afraid the mathematics goes with the territory. There is a proof of special relativity which relies on nothing more than the basic axioms that the laws of physics should be the same for all observers and considering the mutual events of two 1m rulers passing each other. The algebra is a bit tedious but the final result is rather pleasing.

Mathematicians will spend half a term proving 1 != 0 too.

Engineers and physicists tend to accept a somewhat less rigorous approach. One cute feature is that if you take the first velocity dependent leading term of the full relativistic treatment E= mc^2 you get the classical Newtonian kinetic energy = 1/2mv^2

(which of course is as it should be)

[Martin Brown]

Are you really so thick that you cannot rearrange the equation?

m = E/c^2

c^2 being a rather large number makes the change in mass effect small for modest energies but it is not always negligible.

[The Natural Philosopher]

I am afraid that is almost certainly the case..

[Grimly Curmudgeon]

The purveyors of MBS, who were the ones who sat up the back of class in Physics, passing notes, cracking jokes, and ogling the girls' skirts by dropping pencils, probably think that 'cold' is some negative-going quasi-waveform of metaphysical aether that crystal theory can generate when rubbed with the skin of a dead cat in a box. To these people, the concept of heat flows is utterly alien - they didn't grasp it.

[dennis]

So if you move an object on Earth to a larger distance you increase the potential energy. Which one actually increases in mass, the Earth or the object?