Status of the Guru..
Age is not essentially a yardstick for guru-shishya relationship..
Just think of the the young guru sitting under the peepul tree in silence and the aged disciples sitting in front of him..
The silence of the Guru gets communicated to the disciples as explanation for everything and the disciples are relieved from all doubts.
chitram vata tarormooley vridha shishyaaH gurur yuvaa, guroshtu mounam vyakyaanam shisyaastu chchinna samasayaaH..
चित्रं वततरोर्मूले वृद्ध शिष्याः गुरुर्युवा गुरोस्तु मौनं व्याख्यानं शिष्यास्तु च्छिन्न संशयाः
this would tell everything..
In fact such a situation is said to have arisen in the life of Kalidasa..
He married the princess before whom he was presented by deceit through the nasty tricks of some failed lovers of hers who ensured that the princess got married to the doubly distilled idiot.
When she came to know of the trick and the misfortune that had befallen her because of that, she advised the unlettered cowherd that was her husband to approach Mother Kali, and when the Divine mother, in Her infinite mercy, gave him enlightenment, the first thing he remembered was that his wife had assumed the role of his guru who guided him to divinity..
He could not treat her as a wife anymore..
To avoid such situations, in our tradition, all factors including age, relationship etc., were considered very seriously before accepting the guru-shishya relationship..
Getting a very bad and undeserving guru can be considered only as the result of sins we would have incurred in this life and earlier lives.. Mahaapaapashakthi..
What to do?
But once we have chosen the the guru, we cannot brand the reverse learning process as taboo or impossible and cannot treat the guru irreverently. Anyhow our old social norms over the years viewed such reversals in age or education as odd.
In the long history of a society like ours the rules sometimes tend to get biased, sometimes straitjacketed even, and grain and chaff get mixed up.
We have to use our good sense, and avoid the chaff.
Moreover, any action taken in good faith should not be considered as sinful..
The principle shaastraaya cha sukhaaya cha (शास्त्राय च सुखाय च ) always worked. Whoever or whatever is the guru, he has to be accorded great respect .
Learning under a pratiloma ( lesser in age, status etc ) Guru was not envisaged in our Varna based rigid system. I can cite an example. You might have heard of Melpathur Narayana Bhattathiri, the scholar and author of Narayaneeyam.. He was a man of loose morals up to a particular stage in his life and good sense was driven home on him by one Achyutha Pisharodi, a great astrologer and scholar. Melpathur wanted to study vedas too but insisted that he should get the training from Achyutha pisharodi, who was ineligible to learn or teach vedas..
However on Bhattathiris insistence one scholar rendered Vedas to Pisharody and Pisharody in turn taught Bhattathiri..
Consequently sin overtook Pisharody and he was afflicted with Vataroga..
Bhattathiri is said to have taken over the disease and by worshipping Guruvayurappan through Narayaneeyam got relief for himself form Vatarogam.
Here apart from the Bhakti line, the lesson is that an ineligible person teaching someone does not deprive the former of his status as a guru, but only deposits durithams to his own account.
By the same logic, Vidya, whether spiritual or temporal is accepted by us from someone, we have to accept him as our guru..
Definitely Einstein and Newton are our gurus just as Vyasa and Shankara..
I believe so..
Views and opinions can vary..