No Witnesses

...Im not entirely sure what you're asking.But star-magnitude heat can come from several sources. Nuclear fusion is one; others include nuclear fission (which also does happen in stars), antimatter annihilation, even lightning (for a brief fraction of a second).Stars are primarily fusion reactions, but the intense heat and pressure along with the fact that fusion creates heavier elements also result in fission. Friction isn't so much of an issue - the magnitude of energy released by fusion and fission dwarfs that of friction.

This is very true...and it's exactly why science involves attempting to falsify hypotheses.Let's carry on with the Sun example. We know how hot the sun is because we can directly measure it. We know of at least a few candidates for generating that much heat. How do we tell what really drives the Sun?Falsification. Don;t look for confirmation, look for evidence that contradicts each individual hypothesis so that you can narrow down the field until you have one candidate that's more likely than any others.Friction can't generate enough energy to duplicate what we observe in the Sun.We can tell the chemical makeup of a star by analyzing the spectrum of its light, and we can see that our Sun (as well as other stars) are primarily Hydrogen, Helium, etc, with much smaller amounts of heavier elements. We also see that younger stars contain more of the lighter elements, while older stars contain heavier. Hydrogen and Helium are not fissionable elements - they don't tend to spontaneously split the way that, as an example, Uranium-235 does. Fission is unlikely to by more than a small contributor to the energy observed.Lightning is an atmospheric phenomenon, not a stellar phenomenon...but even if we assume an analogue in a star, the lightning bolt would need to be a constant arc rather than a quick discharge in order to continuously generate that much heat. We have never observed any electrical discharge that can just go on for billions of years like that, so pseudo-lightning is likely out.Antimatter annihilation would generate too much energy by multiple orders of magnitude. The Sun wouldn;t look like it does at all - in fact (and I haven't done the math), I would wager that antimatter annihilation would overpower the gravity that holds the Sun together and look more like an immediate supernova rather than a star, ripping apart the Sun and most of the solar system.But fusion does happen when Hydrogen or Helium are exposed to sufficient heat and pressure. We know those elements are abundant in the Sun, along with the products of their fusion. We see telltale neutrino emissions characteristic of fusion reactions. Most importantly, we don't see any evidence that would falsify the hypothesis the way we do for the other ideas.The idea here, foreveryoung, is that while a given set of evidence can fit multiple potential explanations, further investigation tends to falsify most of them.Let's imagine that there's been a murder. There's a bloody knife, and a single black hair. Who did the murder?It could have been Bob - he has black hair. But so do Susan, and Greg, and Nancy and a few thousand other people in the city...and the real killer could even have been from out of town! The evidence supports many different possible explanations.So how do we figure out the facts? We look to the evidence. Who has an alibi for the time of the murder? Who was near the scene at the time? Does anyone have a reason to kill the victim? Can we test the hair to see if it's natural vs dyed? Maybe we can get DNA evidence? Are there fingerprints in the house? Did the hair actually come from the victim, not the killer? All of these would be indirect evidence, but combined we can use them to narrow down our list of suspects from "anyone with black hair" to possibly just the killer.When the evidence equally (really equally, as in the world would look the same to us in either case, not just that there's some evidence that supports A a little, and some other evidence that supports B a bit) supports multiple hypotheses, it means you need more evidence (or at least more consideration) to find the real answer.Most people don't look for falsification, they look for confirmation. You look at the evidence, come up with an initial idea, and then set out to try to see if further evidence confirms your idea, rather than coming up with multiple possibilities and then trying to falsify each one to see which is left standing. Confirmation is a trap - humans have this thing called "confirmation bias," where we unconsciously tend to count confirmation of what we already think as more meaningful than evidence that doesn't support our pet hypotheses. In this way, we can often convince ourselves that we're on the right track...and then find out later we were completely wrong.To prevent this, once you have several hypotheses supported by the evidence, look at each hypothesis again. Imagine what you should not see if each hypothesis were true. Re-examine your evidence, and see if your observations falsify any of those hypotheses. After all, the evidence will never falsify the real answer - and the only one left after you've falsified the others will almost certainly be accurate.BTW - there's an exercise you can do to very clearly illustrate confirmation bias. It's actually pretty interesting and entertaining, or at least I found it to be. It's best done through PMs, so if you're interested, feel free to PM me.