# where does light from a torch go?

Discussion in 'Physics & Math' started by emanresU, Apr 13, 2014.

1. ### Russ_WattersNot a Trump supporter...Valued Senior Member

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Arright, I guess I have to do it for you:
You are more or less right in that that radiation is a two-way street and the temperature of both the source and sink determine the heat transfer. So the Stefan-Boltzmann equation predicts the heat loss of an object by radiation toward another object of a known temperature and thus also the temperature of the object given a certain constant heat input. If your idea is correct, we could simply put an object into space with a constant heat generated and see what the resulting temperature is. From that we can calculate the temperature of whatever it is exchanging radiation with.

If your idea is correct, we can use this experiment to detect the temperature of what the radiation is exchanged with - even if we can't see it, based on the energy exchange. Agree?

And if the object is exchanging heat with nothing, it should get very, very hot according to you: which would also indicate the Stefan-Boltzmann equation breaking-down since the Stefan-Boltzmann equation predicts that if you take away the other object by making the heat sink temperature 0, you actually get the best heat transfer, not the worst. Agreed?

So we can test your idea against the Stefan-Boltzmann law and see whether your idea is correct or if the Stefan-Boltzmann law is correct about this special/limiting case. Right?

3. ### dav57Extraordinary Thinker ThingyRegistered Senior Member

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No. I wonder where the heat eventually gets transferred to in our closed Universe.

5. ### dav57Extraordinary Thinker ThingyRegistered Senior Member

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Russ, i'm struggling because we live in a closed Universe where em waves appear to always have somewhere to go.

7. ### dav57Extraordinary Thinker ThingyRegistered Senior Member

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Ok, this sounds interesting and i need to think about this because there are a couple of obvious complications: the observer could interfere due to heat ingress and also how can you rule out the object connecting with distant objects to transfer heat which is my first postulate to start off with! Difficult.

I know, could we encase the experiment in a big spherical internally-mirrorored contraption which would effectively reflect back all of the infrared? Actually, I'm not sure that would help. I'm starting to think that my idea is completely impossible to prove either way.

8. ### originIn a democracy you deserve the leaders you elect.Valued Senior Member

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Assume an EM wave of any energy left earth right now, since the farthest reaches of the universe are receding from us faster than the speed of light the EM wave could conceivable travel forever. I suspect that is a concept that you won't like but the universe, it seems, doesn't really care what we think.

9. ### Russ_WattersNot a Trump supporter...Valued Senior Member

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1. Have you read up on standard cosmology yet? Do you understand that finite and closed doesn't mean all radiation will eventually hit something?
2. Even if the radiation eventually hits something currently unseen, it doesn't have any impact here more on that with the experiment...

10. ### Russ_WattersNot a Trump supporter...Valued Senior Member

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Yes, in real life, the problem is not one dimensional. The radiation from earth and the sun must be accounted for. That's not an intractable problem.
That is not a complication, it is your claim and the very thing this experiment is designed to measure!
Sorry, no, your idea is quite easy to prove. In fact, it is being proven wrong right now, with thousands of satellites that are testing your idea..... not to mention the temperatures of the earth, sun and all the planets and stars!

11. ### Russ_WattersNot a Trump supporter...Valued Senior Member

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Here is another simple experiment:

You claim that heat transfer is based on future interaction. So try this: walk outside into the sun. Did you start feeling warm 8 minutes ago or exactly when the sunlight started to hit you?

12. ### originIn a democracy you deserve the leaders you elect.Valued Senior Member

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Don't you mean 8 min after, instead of before he walked into the sunlight (not that it makes that much difference)? Maybe the photons 8 minutes ago knew he was going to walk into the sunlight.

Why are all these crazy threads in the science section? It seems like the physics moderators are on extended vacations or something. This thread should clearly be in the alternative section. QQs thread ran its course pages ago and should be in the cesspool.

13. ### exchemistValued Senior Member

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Even the sensible threads are getting infected with incoherently argued eccentricity.

14. ### nimbusRegistered Senior Member

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What,there are moderators here?

15. ### Russ_WattersNot a Trump supporter...Valued Senior Member

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I'm not sure. I realized after I posted that I didn't think it through.

[Pause]

I think you are right: Dav is talking about the emission being dependent on instantaneous action at a distance with an object not yet in sight, but in the line of sight. That means the sun starts radiating to you the instant you step outside, but the sunlight gets to you 8 min later. I flipped it over to be about the receipt of that energy, but then got it backwards.

That also means your shadow follows you around from far behind and when you put your hand up to shield your eyes, you still see the sun for 8 minutes.... unless he's doing away with the finite speed of light altogether, which he implies he wants to.

Obviously, any wrong idea will by definition create/contain contradictions internally or versus reality.

16. ### originIn a democracy you deserve the leaders you elect.Valued Senior Member

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Yeah, it all makes sense when you look at the following facts.
1. the earth is moving at about 1000 miles/min around the sun.
2. The diamter of the earth is about 8,000 miles.
3. It takes a photon about 8 minutes to go from the sun to the orbit of the earth.
4. [dav57 fact] Photons only leave the sun when there is something to hit.
5. [dav57 fact] By the time the photons travel from the sun to the orbit of earth the earth will no longer be there.
6. [dav57 conclusion] The earth is shrouded in perpetual darkness.

What?!?:bugeye:

17. ### exchemistValued Senior Member

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Well done guys, I think you finally nailed this. It seems to have kept DAv57 quiet, at any rate.

But at least this means Dav57 isn't just a troll, or so cracked as to be impervious to argument.

18. ### dav57Extraordinary Thinker ThingyRegistered Senior Member

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I haven't finished yet, will be back at computer in a few days, you'll be please (or not so pleased) to hear!

And by the way, 3 is wrong because photons don't exist until they interact. They don't fly through space and thus their lifespan is negligible during the whole process.
Also, 4 must be wrong because photons don't leave, do they? It's em waves that supposedly leave.
5 therefore must also be wrong because photons don't travel.
And 6 must be wrong because I am writing this and can see the Sun. Actually, i can't see the Sun. I can only see the waves collapsing on my retina.

2 out of 6 isn't bad though!

19. ### Russ_WattersNot a Trump supporter...Valued Senior Member

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Um...do you recognize he was consolidating/summarizing your idea? Yes, we know there is a lot wrong with it: that's what we've been trying to tell you!

20. ### originIn a democracy you deserve the leaders you elect.Valued Senior Member

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An electro-magnetic wave IS a photon.

In light of that your statement does not make sense.

What to you mean their lifetime is negligable? Do you think photons (light) move from point to point instanteously?

21. ### dav57Extraordinary Thinker ThingyRegistered Senior Member

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Yes and no, so I thought. an em wave has no mass. But a photon has a rest mass. That's a difference in itself. To me they are fundamentally different based on that fact alone.

Their rest mass only comes into play when they smack into something. That's not very long considering the journey could have taken light years. And yes, instantaneous communication appears possible based on entanglement. That's the part I'm exploring with regards to source and observer. It appears that light, based on various experiments, knows its future path. Even if I'm wrong, there sure as hell is something else weird going on!

22. ### Russ_WattersNot a Trump supporter...Valued Senior Member

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No it doesn't.
No it doesn't/that's not what he asked.
No it doesn't, at least not in the way you describe
No, because you are wrong, it means all that weirdness is in your head!

I've noticed you are no longer exploring the implications of your idea with any rigor. You appear to prefer a scattered approach to actually constructing some logic and applying it to reality (the experiment you suggested and we were discussing). That's a wrong approach.

So basically, another post where essentially everything you said was wrong and the approach itself was wrong too. Nice work!

23. ### AlexGLike nailing Jello to a treeValued Senior Member

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There is no difference between a photon and and em wave. They are the different aspects of the same thing. A PHOTON HAS NO REST MASS. And if you don't know that, you shouldn't have left school.