Introduction to black holes 2

Clip 2 from Yale University video lecture: Introduction to black holes presented by Professor Charles Bailyn. Date- 23 Dec 07 Source- http://video.google.com/videoplay?docid=-6215434494081736769&hl=en

Category:

Science & Technology

Tags:

• black
• holes
• event
• horizon
• schwarzschild
• radius
• escape
• velocity
• neutron
• star
• collapse

[Jiibrael]

This is rather amusing to dare define the fact that black holes don't let light escape by using Newtonian Mecanic.

Let just not forget that photons have no mass and while the definition of the Schwarschild radius is valid for matter, it is not for light.

Of course the reason for that is that this is just a limit and Newtonian theory is just not applicable in case of relativistic objects (like photons traveling at the speed of light in a vaccum).

[stevebd1]

I suppose you could think of the Schwarzschild radius, which is derived from the Newtonian equation for escape velocity, as a vacuum solution as in the Schwarzschild metric (i.e. event horizon=infinite curvature) which takes care of the massless photon.

[Jiibrael]

I agree ... although I'm not discussing the validity of the Schwarschild radius determination ... I am just surprised by its interpretation in this context and considering that this is a college lecture (not a broad public seminar) it is very surprising.

Btw, the determination of the Schwarshild radius from special and general relativity in modified space-time geometry give the same value ;) ... what a relief :D

[stevebd1]

In most cases, when physicists start to talk about black holes they begin with escape velocity. If they jumped straight into GR & talking about curved space & metric, it might put some people off..

[stevebd1]

..Starting with Newtonian equations also tells us something of the history of understanding black holes as it's speculated that Newton may have unknowingly predicted the event horizon when looking at escape velocity (which can also be derived from metric and expressed in negative form as velocity induced by curvature).

[adamjaffrey89]

3 x 3 = 10? Lol.

Love the video though!

[Hartman4Guiness]

I saw a few of Prof. Bailyn's lectures on Google video, and by typing his name into YouTube I've found these gems, ta for uploading. ^^

[KyotoMelody]

lol no, I dont get u wrong. I was just surprised because someone was talking my language... that he or she was surprised because of having a free college lecture. I love this channel too. Its fascinating :)

[Jiibrael]

lol, don't get me wrong I love this channel and all those videos

[KyotoMelody]

Im a bit surprised too, its for the first time I've had a free college lecture this way. I so hope to have more. Thanks, Steve.

[KyotoMelody]

Im happy that I m not orbiting around other living creatures on the Earth lol. However, Im kinda orbiting around this channel. Thanks, Steve.