Why the sky is dark in the night

[Russ_Watters]

Quite an angry young man.....sounds more like resident PHD Physbang..

Angry? No. I just have no tolerance for being trolled. Clearly you are actually not interested in learning about the subject of your own thread.

 

[Farsight]

...The Big Bang is another example of science run off the end of the rails in terms of extrapolating science we don't yet know that cannot be accomplished by any means other than indefinitely suspending the science previously considered established. and so the conservation of energy in connection with the Big Bang must be jettisoned...

I disagree with this, Dan. IMHO when you understand general relativity and black holes, Big Bang cosmology makes perfect sense. I'm not a fan of inflation myself, or point singularities, and I can't explain why the Big Bang occurred or what the universe was like "before the big bang". But I am a fan of general relativity and conservation of energy, and I know of no examples where energy is not conserved. We have good scientific evidence for the expansion of space, and even if we didn't I'd be saying space just has to expand. What I don't understand is why Einstein didn't predict it.

 

[Russ_Watters]

There are in excess of 10^30 stars in the universe.........(surely we don't see any star of any Galaxy other than MW) still if we receive on an average 10 photons from each star (not a high number)....

On what did you base that 10 photons (it is very wrong)?

Pray, first tell me what is the original Black Body at the time of BB ?

If you read the wiki article on the CMBR you should already know the answer to that.

 

[rpenner]

Can you offer any example where energy conservation is definitely broken as opposed to appears broken?

As in my post #77 and those that followed, I am taking a principled stand on Emmy Nother's theorem. You want to break energy conservation? Break time translation symmetry. You want to show there is a conservation law analogous to Newtonian conservation of energy, then you had better be exact about your definitions so we may see how your analogy is similar and dissimilar.

See what I said above about gravitational field energy being positive rather than negative.

Thank you for pointing it out when I might have let it slide. You have been issued a formal warning for making a controversial claim in the field of gravitation without support via citation and specific quote or even calculation.
That it is a controversial claim should not even be a question since you just quoted Sean Carroll as saying the opposite and Wikipedia writes: "According to classical mechanics, between two or more masses (or other forms of energy–momentum) a gravitational potential energy exists. Conservation of energy requires that this gravitational field energy is always negative.[2] " This should be abundantly clear in orbital mechanics where you need to inject energy to kick a satellite to a higher orbit.

 

[James R]

Farsight:

Next time, I hope you'll support a claim like "gravitational field energy is positive" with some kind of argument, proof, demonstration, or at least a reference.

You are talking about gravitational potential energy, right?

I mean, I can think of ways that it could be positive, but I'm not convinced you can come up with any such explanation.

 

[The God]

On what did you base that 10 photons (it is very wrong)?

.

Then what should I take ? 100 ? 1000 ? 1 ? 0 ?

If you read the wiki article on the CMBR you should already know the answer to that.

I am copy pasting from wiki link......please identify the original Black Body..

I
In the Big Bang model for the formation of the universe, Inflationary Cosmology predicts that after about 10−37 seconds[11] the nascent universe underwent exponential growth that smoothed out nearly all inhomogeneities. The remaining inhomogeneities were caused by quantum fluctuations in the inflaton field that caused the inflation event.[12] After 10−6 seconds, the early universe was made up of a hot, interacting plasma of photons, electrons, and baryons. As the universe expanded, adiabatic cooling caused the energy density of the plasma to decrease until it became favorable for electrons to combine with protons, forming hydrogen atoms. This recombination event happened when the temperature was around 3000 K or when the universe was approximately 379,000 years old.[13] At this point, the photons no longer interacted with the now electrically neutral atoms and began to travel freely through space, resulting in the decoupling of matter and radiation.[14]

The color temperature of the ensemble of decoupled photons has continued to diminish ever since; now down to 2.7260±0.0013 K,[5] it will continue to drop as the universe expands. The intensity of the radiation also corresponds to black-body radiation at 2.726 K because red-shifted black-body radiation is just like black-body radiation at a lower temperature. According to the Big Bang model, the radiation from the sky we measure today comes from a spherical surface called the surface of last scattering. This represents the set of locations in space at which the decoupling event is estimated to have occurred

 

[Russ_Watters]

Then what should I take ? 100 ? 1000 ? 1 ? 0 ?

You shouldn't "take" (wild guess) )any of them. You should calculate it. If that is too hard, you could always try calculating the simpler problem you suggested with Andromeda...

I am copy pasting from wiki link......please identify the original Black Body..

It is stated in the second last sentence.

 

[The God]

You shouldn't "take" (wild guess) )any of them. You should calculate it. If that is too hard, you could always try calculating the simpler problem you suggested with Andromeda...

It is stated in the second last sentence.

Define it, it is a wiki stuff, need not be very accurate...be precise...

 

[Russ_Watters]

Define it, it is a wiki stuff, need not be very accurate...be precise...

Define what?

 

[The God]

As in my post #77 and those that followed, I am taking a principled stand on Emmy Nother's theorem. You want to break energy conservation? Break time translation symmetry. You want to show there is a conservation law analogous to Newtonian conservation of energy, then you had better be exact about your definitions so we may see how your analogy is similar and dissimilar.

Hope your dad is fine now..

I am gathering my wits to respond to your lengthy post...but meanwhile, please throw some conserved energy (light) on following...

The present GW detection, 1.3 bly away two BHs merged they lost 3M, since mass was to be conserved (I hope in GR too) so 3M equivalent energy created ripples in the curvature of spacetime...which travelled upto us.......the point is, it was all through a GR excercise from extremely curved spacetime (BH merging) to almost flat spacetime (Earth)...was the energy remained conserved ? or we are being choosy here too ?

 

[Farsight]

As in my post #77 and those that followed, I am taking a principled stand on Emmy Nother's theorem. You want to break energy conservation? Break time translation symmetry. You want to show there is a conservation law analogous to Newtonian conservation of energy, then you had better be exact about your definitions so we may see how your analogy is similar and dissimilar.

I must reiterate: can you offer any example where energy conservation is definitely broken, as opposed to appears broken?

Thank you for pointing it out when I might have let it slide. You have been issued a formal warning for making a controversial claim in the field of gravitation without support via citation and specific quote or even calculation.

Here's my citation: "For this reason we have here deduced it from the requirement that the energy of the gravitational field shall act gravitatively in the same way as any other kind of energy". That's from The Foundation of the General Theory of Relativity. Gravitational field energy is most definitely positive. I'm sure I can give you more references should you wish. Meanwhile see gravity gravitates.

That it is a controversial claim should not even be a question since you just quoted Sean Carroll as saying the opposite

Sean Carroll was wrong when he said gravitational field energy is negative.

Wikipedia writes: "According to classical mechanics, between two or more masses (or other forms of energy–momentum) a gravitational potential energy exists. Conservation of energy requires that this gravitational field energy is always negative.[2]"

That's wrong too. Because it's a classical article, which suffers from the convention wherein the potential is said to be zero at infinity. As for the satellite, I shall simplify the scenario: when you lift a brick you do work on it, you add energy to it. The Earth didn't move in any detectable fashion, so we ignore the Earth. The energy you added to the brick is positive. When you drop the brick, this potential energy is converted into kinetic energy, which is also positive. When you dissipate this kinetic energy you're left with a mass deficit. See Wikipedia. The brick now comprises less mass-energy than it did before you dropped it. But the brick's energy is still positive. At all points in the scenario energy was conserved, and whilst we talk of binding energy as negative energy, binding energy is not gravitational field energy, and at no point was there any actual entity involved that consisted of negative energy.

 

[The God]

You shouldn't "take" (wild guess) )any of them. You should calculate it. If that is too hard, you could always try calculating the simpler problem you suggested with Andromeda...

It is stated in the second last sentence.

You said it is very wrong....10 is very wrong ? Then tell me what is right ?

 

[The God]

Define what?

Define the original Black Body....what is that surface of last scattering and how it was Black Body ? Even our atmosphere dust particle's can produce a surface of last scattering for outbound photons....

 

[Russ_Watters]

You said it is very wrong....10 is very wrong ? Then tell me what is right ?

No - it is your responsibility to do the calculations behind your claims, not mine or anyone else's. You're making wild guesses and that isn't acceptable. This is your deal, not mine. I can help you do the calculation, but I won't do it for you.

 

[Russ_Watters]

....what is that surface of last scattering and how it was Black Body ?

Ah, so you do know the name now. Good! Now, did you read the rest of the paragraphs you quoted? They are the definition you are asking for.

 

[Farsight]

Next time, I hope you'll support a claim like "gravitational field energy is positive" with some kind of argument, proof, demonstration, or at least a reference.

I didn't do it initially because I thought everybody knew this because it's in The Foundation of the General Theory of Relativity. See above. Electromagnetic field energy is positive, so is gravitational field energy.

You are talking about gravitational potential energy, right?

Not as such. Gravitational potential energy is said to be negative because the convention is to set the zero at infinity, and say it's negative at a lesser distance.

I mean, I can think of ways that it could be positive, but I'm not convinced you can come up with any such explanation.

The energy density of space just above the surface of the Earth is higher than the energy-density of space midway between two galaxies.

 

[The God]

Angry? No. I just have no tolerance for being trolled. Clearly you are actually not interested in learning about the subject of your own thread.

You have not offered anything.........I asked you two questions, you have not answered..

Q1. at what CMBR temperature, the sky will not appear to be dark in night (absence of Sun light) ?

Q2 And when possibly this temperature would have occured after BB ?

Q3. If 10^31 stars cannot make the night sky bright, then how many stars could do that ?

The infinite universe is debunked as it leads to infinite brightness based on obvious caluclation (that caluclation may be faulty)....but we do not need infinite photons to make our night sky bright...as I said roughly around 10^31 (few zeroes here and there) photons per second would be sufficient to give us full moon type brightness....How many stars would be required for that ?

 

[The God]

Ah, so you do know the name now. Good! Now, did you read the rest of the paragraphs you quoted? They are the definition you are asking for.

You are resorting to adhoms.............I got you, you are as shallow as few people around, who just make noise in support of mainstream, that too from a position of ignorance.

 

[Russ_Watters]

You have not offered anything........

That's a lie. In particular, I provided a method for calculating the brightness of Andromeda(per your question in post #10) - twice - and you have ignored it.

Q1. at what CMBR temperature, the sky will not appear to be dark in night (absence of Sun light) ?

Several people including me answered that. The problem is that it is a bad question. There are ways to reformulate it into a better question, which were pointed out to you, but you didn't respond.

I guess i'll give you a specific answer, just to see where it goes: 5,800k.

Q2 And when possibly this temperature would have occured after BB ?

Don't know/not relevant, but if you can explain why you think it is relevant, maybe a better answer is possible.

Q3. If 10^31 stars cannot make the night sky bright, then how many stars could do that ?

Again, it is your responsibility to do this work. I can help, but you need to show you are working on it in order for me to be able to help you with it.

 

[Russ_Watters]

You are resorting to adhoms......

I don't think you know what that term means. It appears to me that you are getting frustrated that your wild goose chase has ended. Everything you said you wanted to know is there in what you read....which for some odd reason seems to annoy you. Shame.


...that and you appear upset that your wild guess was called out.