Q: What is absolute truth?

A: Let me derive the answer. Brahma Samitaa 5.1 says:

ईश्वरः परमः कृष्णः सच्चिदानन्द विग्रह ।
अनादिर् आदिर् गोविंदः सर्व कारण कारणम्  ॥

In my words it means:
The supreme controller is Krishna (The Supreme God).
He is sat chit aaanand muurti.
He is the oldest of all, meaning He is eternal, exists for ever.
He is the cause of all causes.

Now the cause of something has to be a truth, else it is not a cause.

A cause also has one or more causes, and that second level causes also have 3rd level causes.
Thus the final cause is Krishna/God. There is no cause beyond Him.
So He is the supreme cause, ultimate cause, and therefore absolute truth.

Any cause below the absolute is relative cause that only some understand, all do not understand or see or realize.

Scientists' business is to dig higher level truths.
Usually they make a theory that seems to agree with the observed phenomena.
But after some time it may happen that the theory cannot explain some phenomenon.
Then the scientist revise the theory. So, we can say that scientists know only the relative truth, which could be useful as an absolute truth for some time till a time comes when the truth they know becomes doubtful. E.g. Newtons' laws of gravity failed to explain inter-atomic phenomenon. So quantum mechanics theory was developed to explain it.

Hope this helps.

BTW, I write in bold because it is more readable. I am not shouting.

jai sri krishna!
[Suresh Vyas <skanda987@gmail.com>]