At the age of 80, Siddhartha Gautama ate his last meal (either pork or truffles) which he had received as an offering from a blacksmith. Gautama Buddha realized that his end was fast approaching and indeed, he passed away  the following day, during a full moon in May.

The Buddha’s final words were, “All things must pass away. Strive for your own salvation with diligence.”

The Buddha’s words warn us of impermanence. We must remember that all formations are impermanent and that whatever is subject to origination is subject to cessation.  Though things seemed fixed and solid, they are actually in a constant state of change.  Hence arises the  illusory nature of appearances.

You cannot step into the same river twice, as Heraclitus so famously observed. “All things must pass” also perfectly expresses the second law of thermodynamics.  Known as entropy, it is an expression of the universal principle of decay observable in nature. Scientists esteem it to be one of the most infallible laws ever studied.

“The law that entropy always increases holds, I think, the supreme position among the laws of nature… If your theory is found to be against the second law of thermodynamics I can give you no hope; there is nothing for it but to collapse in deepest humiliation.” — Sir Arthur Stanley Eddington, The Nature of the Physical World (1927)

George Harrison addresses the concept of impermanence in his song, "All Things Must Pass."

All Things Must Pass by George Harrison  1969

Sunrise doesnt’t't last all morning
A cloudburst doesnt’t't last all day
Seems my love is up and has left you with no warning
Its not always going to be this grey

All things must pass
All things must pass away

Sunset doesnt’t't last all evening
A mind can blow those clouds away
After all this, my love is up and must be leaving
Its not always going to be this grey

All things must pass
All things must pass away
All things must pass
None of lifes strings can last
So, I must be on my way
And face another day

"An Eastern monarch once charged his wise men to invent him a sentence, to be ever in view, and which should be true and appropriate in all times and situations. They presented him the words: "And this, too, shall pass away." How much it expresses! How chastening in the hour of pride! How consoling in the depths of affliction!" -Abraham Lincoln, September 30, 1859

Now the darkness only stays the night-time
In the morning it will fade away
Daylight is good at arriving at the right time
Its not always going to be this grey

All things must pass
All things must pass away
All things must pass
All things must pass away