Black Holes: the Reith Lectures - Deepstash
Black Holes: the Reith Lectures

Black Holes: the Reith Lectures

Stephen Hawking

7 ideas


2K reads


Conversation Starters

Learn more about scienceandnature with this collection

How to ask open-ended questions

How to avoid awkward silences

How to show interest in others

Conversation Starters

Discover 66 similar ideas in

It takes just

9 mins to read

What is a Black hole ?

What is a Black hole ?

Black holes cannot be seen as they don't reflect any light.

The centre of black hole is called singularity - a point of infinite density i.e the space curvature extends to infinity.

According to scientists, billons of black holes exists of which millions are having the abode Milky way galaxy


719 reads

Can‘t see , but how do we know their existence

Can‘t see , but how do we know their existence

  • But scientists know they exist because they rip apart stars that get too close to them and because they can send tremors through space.
  • It was a collision between two black holes more than a billion years ago that triggered what are called ‘gravitational waves’.
  • Albert Einstein even wrote a paper in 1939 claiming that stars could not collapse under gravity because matter could not be compressed beyond a certain point.
  • The principal exception was the American scientist John Wheeler,emphasized that many stars would eventually collapse, and pointed out the posed for theoretical physics.


299 reads

Formation of Black holes

Formation of Black holes

  • During most of the life of a normal star, over many billions of years, it will support itself against its own gravity by thermal pressure, caused by nuclear processes which convert hydrogen into helium.
  • The explosive force of nuclear fusion inside them creates outward pressure which is constrained by gravity pulling everything inwards.
  • Eventually, however, the star will exhaust its nuclear fuel. The star will now contract.
  • For more detail , check out Chandrashekhar limit and Tolmann Volkoff Oppenheimer approximation


255 reads



  • if you take pressure out of the calculation,a uniform spherically symmetric star would contract to a single point of infinite density,I.e,Singularity.
  • A singularity is what you end up with when a giant star is compressed to an unimaginably small point.
  • It refers not only to the end of a star but also to a far more fundamental idea about the starting-point for the formation of the entire universe.
  • All our theories of space are formulated on the assumption that space-time is smooth and nearly flat,so they break down at the singularity.In fact, the singularity marks the end of time itself.


192 reads

Einstein‘s View

  1. It was already clear that a uniform spherical star would contract to a point of infinite density, a singularity.
  2. Einstein’s Theory of General Relativity says that objects distort the space-time around them.
  3. At this point of infinite density, one can’t predict the future, which in turn implies that something strange could happen whenever a star collapsed.


184 reads


  • All the black hole will remember is the total mass, the state of rotation and the electric charge.
  • A black hole has a boundary, called the event horizon. This is where gravity is just strong enough to drag light back and prevent it escaping.
  • Because nothing can travel faster than light, everything else will get dragged back also.
  • There is a black hole with a mass of about four million times that of the sun at the centre of our Milky Way galaxy.
  • Scientists believe that there are huge black holes at the centre of virtually all galaxies.


169 reads



  • With no light escaping from the black hole, there is no way that anyone watching from a distance could actually witness your descent. In space, no one can hear you scream; and in a black hole, no one can see you disappear.


190 reads

Read & Learn

20x Faster





Access to 200,000+ ideas

Access to the mobile app

Unlimited idea saving & library

Unlimited history

Unlimited listening to ideas

Downloading & offline access

Personalized recommendations

Supercharge your mind with one idea per day

Enter your email and spend 1 minute every day to learn something new.


I agree to receive email updates