In Sanskrit, Linga means a 'mark' or a symbol, which points to a timeless inference. Thus the Shiva Linga is a symbol of Lord Shiva - a mark that reminds of the Omnipotent Lord, which is formless, cosmic. From ancient times sculptor represents mind by male body because male genitalia shows dramatic metamorphism between excited and relaxed states. His bodily response is not dependent on some external cause and its causeless.
The Linga was originally worshiped by Vayu in Maha Kailasha on the peak of Sivanandaikanilaya. In Kritayuga it was shining link gold and was worshiped by Brahma, Agastya, Devi Parvati, Yogini Neela, Harahara, Mayura, Bheema, Chandra, Surya and Indra. During this time Lord Brahma brought the peak called Sivanandaikanilaya from Kailasha and fixed it here. Sage Agastya brought down Ganga in the form of Swarnamukhi. In Tretayuga the Linga was shining like silver and was worshipped by Hari, Brahma, Devi Lakshmi, Subramanya, Sri Rama, Rishi Markandeya, Kanappa, Spider (Sri), Serpent (Kala), Elephant (Hasti) and Sudarshana.
In Dwaparayuga the Linga was like steel and was worshiped by celebrated couple Subhaga and Vijaya, Japala, Mrutyunjaya, Narada, Suka, Sanatkumara, Parasara and a group of thousand gods. In Kaliyuga the Linga was like a rock with the glow of camphor and was worshiped by Saranga, Varaguna Pandya, Rajendra Chola, Neelakantha, Chakradhara, twin princesses Amritalatha and Kanthimathi, Padmasena etc. In Netyuga, there are millions of twisted Bhakts... real genes are diluted thanks to character of looting cronies and business of religion!
So basically a self stirred male part is physical expression of an idea known as sat-chitta, ananda which means ananda that follows when chitta (mind) discovers truth about this in nature and human condition (sat) by purging itself of all memories and prejudice. Tapa cleanses mind, purges all memories and prejudices so that it experiences sat-chitta-ananda. Tapsivis refuses any connection with the material world because everything is mortal in nature and they want to break free from this mortality and seek immortality, siddha. To procreate the semen should flow downwards but that will result in mortality. It can be make to flow upwards with yoga, this generates wisdom and ignites the spiritual fire of Tapa and result in immortality. This upward movement of semen is described in Tantra as Urdhvaretas. In the Linga Purâna, the same hymn is expanded in the shape of stories, meant to establish the glory of the great Stambha and the superiority of Mahâdeva.
Shiva is considered to be the most powerful as well as the most destructive God or Deity. Reverse movement of semen is also metaphor for reversal of senses so that we pay less attention towards outside material world and more attention to the inside spirituality. It is depicted in art as a erected phallus in a tapasvis whose eye are shut. Shiva is the greatest tapasvin in whole universe, therefore shiva linga is the symbol of self stirred phallus of the that great tapasvin, the burning of tapa, reverse flow of semen. It also depicts shiva among all the gods as formless , not contained, bounded by any material form.
The one who is here before the start of time and will be there after the end of everything, something beyond time, infinite. It also represents holding infinite energy in Cosmic form (so is the shape of Nuclear reactors, Electric Bulb etc.). Nuclear energy is constructive and destructive at the same time. Famous Historian Late P.N. Oak described 12 Molecular Energy Center of Ancient India in Chapter 21 of First Block in his famous book "Vaidik Vishwa: Rasthra Ka Itihaas". According to OAK, there are 12 Jyotirlinga, though there could be much more unexplored, the creations cannot be smarter than creators! All high-energy nuclear reactors were located at these 12 Jyotirlinga to tap some cosmic energy.
1. Somnath (Gujarat).
2. Malikaarjun (Andhra Pradesh)
3. Mahakal (Ujjain)
4. Onkareshwar (M.P)
5. KedarNath (Uttarakhand)
6. BhimShankar (Maharashtra)
7. Kashi Vishvanath (Kashi)
8. Shrambhkeswar (Nasik)
9. Baidnath (Bihar)
10. Nageshwar (Gujarat)
11. Rameshwar (TamilNadu)
12. Ghaneswar (Aurangabad)
षष्ठी स्थानेयोगा - स्थानेऽन्तरतमः - आदिरन्त्येन सहेता - अकः सवर्णे दीर्घः
Panini, was a student at a Gurukula (a system of education in the 4th century BC). He was a dull student, and was often teased by his friends. So, worried about his situation, the Gurumata (the wife of the Guru) advised him to go to the Himalayas to do tapas. So he went to the Himalayas and started meditating on Lord Shiva, pleased with Panini's strong tapas, Lord came and danced before him. While dancing, sound from his Damaru was heard by Panini as Maheshwara Sutrani. Thus, Panini wrote Maheshwara Sutras and formed Sanskrit grammar - शिवताण्डवस्तोत्रम् |