# ACC As Per Stephen Hawking Bl

1) Stephen Hawking proposed that black holes will evaporate over a long enough time scale. In other words, a black hole that is isolated will eventually disappear. The following link will be used to help create a graph.

**Before opening the link, there is a lot of intimidating mathematical formulae that you don’t need to concern yourself with.**

This link will be used to find the size primordial black hole that will still be present in the Universe today. The first input box is for mass, and you should make sure that units of kilograms (kg) is selected. The last input box is for lifetime, and you should make sure that units of gigayears is selected. A gigayear is one billion years. The age of the Universe is thought to be roughly 12.5 gigayears.

2) Create a data table where the values for lifetime are 1.0, 2.0, 4.0, 6.0, 8.0, 10.0, 12.5, and 15.0. This will go on the horizontal axis.

Use the link below to determine the mass in kilograms for each lifetime. You will want to record the answer in units of 10^11 kg. This means that 2.0e+11 would be 2.0 * 10^11 kg and would simply be recorded as 2.0 for the graph.

Similarly, a value of 3.0e+10 would be 3.0 * 10^10 kg and would be recorded as 0.30 for the graph.

3) Once you have the data table created, construct the graph. Remember that the age of the Universe is thought to be 12.5 billion years old. Indicate on the graph where this point lies.

4) Theoretically, black holes of any mass could be created. Let’s say a black hole of mass 10^6 kilograms was formed just after the big bang. What would be its lifetime (use the link provided)? Would this black hole still be in existence today?

5) Finally, again consider the point from question (3). Would a black hole that formed just after the Big Bang with this mass be the same size today? [Hint: it is evaporating.] What does this mean about detecting primordial black holes and determining what their mass was when they formed?

Black Hole link: https://www.vttoth.com/CMS/physics-notes/311-hawking-radiation-calculator