Particle Physics (22 of 41) What is a Photon? 6. Gravitational Redshift

In this video I will explain how photon is affected by gravity can lose or gain energy.

Next video in the Particle Physics series can be seen at:

[GermanSnipe]

Is there anything you don't know?!?!?!

[ohiovic]

In general relativity, as the photon gets closer to a heavy star or black hole, it doesn't gain energy but its wavelength decreases, and also its velocity also decreases (no change in energy). The photon velocity approaches zero at the event horizon. The reverse takes place as the photon goes away from the heavy star or black hole.

[barrybryant]

You're my go-to guy when I want to know anything about anything! Thanks so much for all your uploads!

[khaledmaarouf]

Thank you these lectures are very helpful! Keep it up sir

[gorkematay]

You and the educators like you are one of the most precious people in the world. I love your videos. Understandable for most people, professional and entertaining. Thank you Sir.

[zakirhussain-jsku]

If photon is massless why we have to rely on mass even if equivalent mass. What is the difference b/w actual & equivalent mass if they produce same effects.

[industrialautomaticworks]

now i have a better understanding of objects shifting to red
thank you !!

[Axlg]

I dont think black holes bend light, i think it bend the material what create light. So it is not bending or change the direction of the photons.

[tankp]

Should it not be h*f0/(c*c) in the last equation ?

[jartsajartsa]

That's wrong.

Blueshift of a radio broadcast to downhill is particularly easy to debunk.

I'll explain if anyone is interested.

[jakubkusmierczak]

Now I know how the red shift appears and this is quite something 😁 (I will never knew) thank You.

[mairisberzins]

But where does that energy which photon lost go? Does it contribute to mass of the black hole?

[Smierdzoncy]

Michel van Biezen you don't see a paradox in this? In Friedman theory, formula for energy of photon says that energy of photon depends inversely proportional to the oscillation period of electromagnetic field or inversely to wavelenght, is that correct? However concept of photon proposed by Einstein in 1905 says that energy of photon SIMULTANEOUSLY depends inversely to period and inversely to wavelenght right? Now in Friedman theory of expanding universe time is Newton-ish so if energy of photon depends inversely proportional to period then color of light should not change because in Friedman theory time isn't deformed. If light is slowed by gravity like you just said then Hubble law is wrong and our universe isn't expanding. That leads to a new cosmological model of universe with Earth in its center (because of Gauss law where gravity grows linear from center of spherical bodies).Light goes into redshift because of gravity not because galaxies are runnig away from us. Watch my movies for more if you're interested.

[tankp]

Also G*M/(R*C*C) has to be smaller than 1?

[siddiki]

At 4:20 "Blue light has the shortest wavelength"? Shouldn't Violet have the shortest wavelength from the visible spectrum? Thanks for the video though! Really enjoy watching & learning about these things.

[JoeDeglman]

Finally, that is the first thing I've heard about light and photons that actually made sense.  Most of the theories from Einstein about light propagation always seemed counter-intuitive to me.  Thinking we could scrap All Einstein theories save the photo-electric effect.  The other thought I have about this is maybe the same thing that causes an electronic clock to run slower near the earth then in space might change the spectral absorption frequency of an atom near a star and cause an apparent redshift as well?

[Danielagostinho]

I dont understand something.As Newton, the gravitational force decreases with increasing of the distance, because they are inversally proporcional, so the Potential energy decreases, therefore, the photon would require less energy to go farther away. So how is the photon energy decreasing.

[vanubatimajhi]

Thanks for your answer but I think photons have mass which is very rare that is why it is not apparent and beyond observable, which act as if mass.i am not sure but hypothetical.

[jimyguitar]

Space rushing into earth causing weight.
Space rushing faster into a black hole causing extreme weight.
Rushing space near a black hole causing red shift.
Similarly a force from accelerating in space is space passing through objects on earth.

[vincentgrimes]

This way, photons have no mass, cleaning up a good sized portion of the Standard Physics Model, I think?