Black Holes - PowerPoint PPT Presentation

Loading...

PPT – Black Holes PowerPoint presentation | free to download - id: 586e50-ZjgzN



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

Black Holes

Description:

The End of Space and Time Topics Introduction Black Holes Static Rotating Detection Summary Introduction Gravity (1600s) Introduction 1783 John Michel, a ... – PowerPoint PPT presentation

Number of Views:77
Avg rating:3.0/5.0
Slides: 21
Provided by: Harri88
Category:
Tags: black | holes

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: Black Holes


1
Black Holes
  • The End of Space and Time

2
Topics
  • Introduction
  • Black Holes
  • Static
  • Rotating
  • Detection
  • Summary

3
Introduction Gravity (1600s)
All objects fall at the same rate
But how can this be?
4
Introduction
  • 1783
  • John Michel, a Cambridge professor, noted that a
    sufficiently massive and compact star could have
    an escape speed vesc that exceeds that of light,
    in which case light would be unable to escape
    from it.

5
Introduction II
  • 1907
  • Einstein had a crucial insight
  • A person falling off a building experiences no
    gravity!
  • The happiest thought of my life

6
Introduction III
  • This insight led Einstein to propose the
  • Principle of Equivalence
  • A local frame of reference (for example, the
    inside of a small elevator) in free fall is
    indistinguishable from a local frame of reference
    in free space. 

7
Introduction IV
Principle of Equivalence
8
Introduction V
  • Einstein's great leap of imagination
  • He suggested that objects in a gravitational
    field move as they do, not because of a
    mysterious force called the force of gravity,
    but, because the space and time in which they
    move is warped by the presence of matter and
    energy.
  • Consequently, objects of differing mass fall
    towards the ground with the same acceleration
    because they follow the same space-time
    contours.

9
Gravity as Curved Spacetime
  • Spacetime
  • Is warped by matter and energy
  • All objects
  • Experience the same hills and valleys of
    spacetime.

10
Introduction General Relativity (1915)
Bending of star-light by the Sun
Sir Arthur Eddington Eclipse Expeditions 1919
11
The Schwarzschild Solution (1916)
  • Karl Schwarzschild
  • Karl Schwarzschild found the first exact solution
    of Einstein's equations.
  • It describes the space-time geometry around any
    spherical object.

http//scienceworld.wolfram.com/biography/photo-cr
edits.htmlSchwarzschild
12
Static Black Holes
Photon sphere
Event horizon
Escape speed light speed
3RS/2
RS
RS is called the Schwarzschild Radius RS 3 km
for the Sun
Singularity A boundary in space and time
13
Time-Warps Near the Event Horizon
  • Time-Warps
  • The event horizon is a one-way boundary You can
    enter, but in the words of a famous song, You
    can check out anytime you like but you can never
    leave
  • Moreover, from the viewpoint of a traveler who
    crosses the event horizon the crossing occurs in
    a finite amount of time.
  • But from the viewpoint of someone far from the
    black hole, the traveler takes an infinite amount
    of time to cross!

14
Space-Warps Near the Event Horizon
15
  • Rotating Black Holes
  • Black holes have two
  • special boundaries
  • Event Horizon
  • Stationary Limit
  • For static holes these boundaries coincide, but
  • differ for holes that rotate.

Fig. 14-7, p.284
16
Detecting Black Holes Or how to find the grin
of the Cheshire cat
Fig. 14-8, p.285
17
The Grin of Cygnus X-1
Fig. 14-10a, p.286
18
Fig. 14-11, p.288
19
Super-Massive Black Holes
Galaxy M87 Distance 50 million ly Length of
jet 4000 ly MassBH 2 billion M? RadiusBH 3km
x 2 billion 6 billion km 40 AU
20
Summary
  • The finite speed of light allows, in principle,
    the existence of objects from which light cannot
    escape.
  • In Einsteins theory of gravity the latter is
    explained as a warping of space and time of which
    black holes are the extreme examples.
  • Evidence is mounting suggesting, amazingly, that
    such objects actually exist.
About PowerShow.com