When The Data In A Cell Changes, Automatically Take A Record Of This Change Data

I am not sure how to go about creating a spreadsheet that does this:

I have a number much like a stock market index which is in cell A1 for instance, and this data changes every second,

And I wish to create my spreadsheet to automatically make a record of this change value and populate it at the last available blank row, so ultimately, I have a full history of how this number changes during the course of time.

5450 in cell A1
a second later, it changes to 5430
and so I want to populate 5430 to A2

and then another second, it changes from 5430 to 5470 and so i want to populate 5470 to A3 and so forth....

does anyone know how to do it?