You don't need to fully understand something to know that it will die. I don't need to know what the billions of transistors in a MacBook CPU do in order to und

You don't need to fully understand something to know that it will die. I don't need to know what the billions of transistors in a MacBook CPU do in order to understand that the CPU will cease to compute if placed in an incinerator and burned to gas and ash. I don't need to understand how the human brain works in order to understand that it will no longer work when our star balloons to a red giant and incinerates the brain to gas and ash. You don't need to understand things in order to understand that they will end when physically destroyed. Everything in our universe will be physically destroyed at the Heat Death. Time, Space, Matter, and Energy will all end. There is no "middle ground". It will all end. If there is an eternal God who exists outside the universe and who will sustain the immortality of souls, as Plato thought 2400 years ago and all noteable Judeo-Christian philosophers have held, then something of humans will exist after the Heat Death. Otherwise, we know it will all die, and we don't need to know how it works to know that it will die.