#5minphysics 21: Black hole Paradoxes!

Classical Black holes didn't seem that strange, but when general relativity and quantum mechanics are introduced they become stranger, as exemplified by Hawking Radiation. All this leads to 3 paradoxes: 1. time appears to stop at the event horizon, 2. Black Hole evaporation appear to violate a central tenet of quantum mechanics, 3. If black holes radiate at some finite temperature, then something very strange must be happening near the event horizon, which is inconsistent with the fact that a classical observer notices nothing strange when they fall through. I try and show how all this arises in a 15 min #15minphysics episode.

[stavrosmaiden]

I love the fact that #5minphysics is always more than 5 minutes!!
Thanks Lawrence!!!

[GETMEASTRAITJACKET]

Stay safe Lawrence, thanks for this series of vids.

[woody]

We need to spread more light on black holes! Mindboggling stuff, thank you, professor.

[haimkohan]

Fascinating. Thank you for doing these videos and congratulation on finishing the manuscript for a new book!!

[sphinxtheeminx]

How I laughed at 2.05 when he speaks about 'getting on to the mysteries' - like the preceding two minutes hadn't ruined my mind with the unmysterious stuff I'm not equipped to compute.

[ahmedsyed]

Thank you Dr. Krauss for explaining complex topics to a layman like me. 🙂

[Rog]

This is the first time I've agreed with an eminent physicist, I also think it's a mystery.

[olafgusten]

just find out that you have a youtube channel, and your #5minphysic are didactic as well refreshing. Thanks for making us able to grasp complex ideas, making your field of work more a tangible for us. continue the great work.

[Bazzo]

Fascinating paradoxes. I'd read that the entropy of a black hole was proportional to its area but now I understand why - thank you. Looking forward to reading your new book.

[paulc]

Hi Prof. Krauss,
Thanks for another interesting Talk. I am a bit surprised that you didn't mention Leonard Susskind's "Holographic Principle", which I think is quite amazing. And it could even be correct !! All the best, Paul C.

[naturediary]

Thanks again Lawrence, you explained in beautifully clear way these 3 paradoxes around Black Holes which make viewing this video so interesting. I'm really looking forward to your new book being published. Take care. Doug

[АлександрВасильев-нуэ]

I'm Russian and never heard the term "Frozen Star" especially applied to Black Holes. Maybe it is due to the fact that I'm a chemist and not physicist, but I read a lot of physics and cosmology related books in my time.
And btw big thanks for your greatly entertaining content.

[eduverse]

This video itself experienced time dilation. A 15 minute video was time dilated and became an hour long video in my frame of reference. That's because I took a lot of notes. Thanks professor.

[sunshineconch]

I'm going to have to watch this one again. Didn't get my head fully wrapped around it the first time.

[RobertCleggRC]

"Dimmer and Dimmer": That's when the movie Dumb and Dumber travels to an event horizon.

[sirwilliamkarl]

Glad to hear there's a new book coming. Still months away I'd guess...?

[markmd]

I love paradoxes even if I'm not a physicist, here's my thoughts:

The explosions are the creators of information - Big Bang created the fundamental particles and stars and supernovae created heavier elements.
While the black holes are the erasers of information - an object falling into it will break into molecules, molecules into atoms, atoms into plasma, plasma into neutrons and neutrons into quarks, quarks into energy and all the information is lost in this work of decomposition.

If to imagine and observer falling into a black hole his time will begin to slow down until it stops. What does this mean - "there is no time"? It means he is dead! and he not even realized it. Of course there can't be any talking about firewalls with dead men.

[AnishDharmakkan]

Last :'( Thoroughly enjoyed this series. Thanks @Lawrence Krauss

[abhikrishnaravi]

Hlo Mr Krauss, In any of the coming videos of #5minphysics can you please explain the recent attempts to solve the theory of everything, including the string theory . I hope for it.

[gilbertengler]

I understand that energie is conserved, but I have problems to understand why information should be conserved.
If a person dies, his body still has all the molecules present when alive containing all the energy, but what happens with all the knowledge you (eventually) had in your brains, what happens with the millions of patterns of reactions that was perfectly orchestrated going on in living cells and tissues? This information is simply gone in a second (or minutes) and what is here conserved??
Thanks for your excellent explanations!