Olbers' Paradox - A Level Physics

Olbers' Paradox - why is the sky dark at night - explained

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  Science & Technology

[Guentereconomy]

Great video, but what if a a planet is in between your view of a star, blocking it's light? I am at 10:37 in the video at the moment, great video.

[DrPhysicsA]

The general argument is that if you had as much radiation energy coming from a "white" sky as might be thought to exist, then any obstacle would absorb that radiation, would heat up and would then begin to radiate it again (and in the visible region). So an obstacle would itself become bright.

[Arghya Chatterjee]

Sir, please publish more video............

[DrPhysicsA]

Thanks for kind comment. My channel has over 100 videos on it. Hope they are of interest.

[fico tronic]

Hello Sir, I cant begin to explain how much do I appreciate your videos as a physicist to be. and also more personally thank you for your kindness and conviction for teaching and sharing knowledge with humanity, and I hope it doesnt have too much to do with lucrative or status benefits. Which I can imagine it isn't the case. For your time, thank you. Warm regards all the way from México.

[DrPhysicsA]

Thanks for your kind comments. I enjoy making them and very pleased if others find them helpful.

[bbysf]

great video, biologists answer to why the sky is dark at night - because our eyes are not sensitive enough to see the light...

[Ben Reynolds]

And depending on your/their definition of 'light', they would be right?

Over simplified, perhaps, but our eyes are not sensitive enough to detect the photons carrying 'light' outside of the visible spectrum? So CMBR is 'light' just red shifted to the point that our eyes cannot see it...

Of course, there are many arguments that this does not counter, but there is an element of overlap, surely?

[CC3GROUNDZERO]

But Olbers couldn't take into account cosmic inflation, right? So there *could* be an infinite number stars, just that their light hasn't reached us and never will.

[Bougainvella]

this video is so good! Thank you so much it helps me a lot since I am doing this topic now, it is hard to understand by reading the textbook, your explanation makes everything clear and interesting, I watched it 2 times ! I started with nothing and finished watching with many things going around in my mind and I understand them :)

[chudzo skruo]

Assumption have to be wrong. Since if true You have to see on the sky not the stars as a point, but you have to see whole sky as one big star.

Again when you canceled R^2 in numerator and denominator these are not the same. Since if they are same number of stars have to grow through universe by R^2 which is not truth. 4×(distance between earth and sun) you cannot to find 4×4 stars.

Quit contrary if neareast galaxy does not provide enough light furthermost so also.

We are fortunately near the sun

[Gaetumrex]

The "counter-luminous points" could only be black holes. again many believe that there are black holes just because of what I said earlier. Because the stars , the black holes and earth are not permanently situated on the same axis we can tell that there are black holes. Unless of course you would be bold enough to propose that there are black holes big enough to block light coming from distant galaxies that are situated on same axis and also situated in the space between galaxies.

[Gaetumrex]

Then you have another problem. For a "non-luminous shadow-producing object" to interact with light coming from distant galaxies in such way that we cannot see it means that the respective object and the light we don't see to be situated on the same line with earth at all times. Really how plausible does that seem to you?

[Gaetumrex]

You can only go to a certain point with the first theory. Earth for instance blocks sun's light up to a certain point after which you would have a difficult time noticing the earth because of the sun's light.

You cannot have a celestial body that is close enough to earth to block a chunk of light coming from distant galaxies and with enough volume.

If there is such a case then you can tell that the object is there