First of all, Krishna did not stop time, when He spoke Bhagavad Gita. It took Him about an hour to speak the 700 verses that comprise Bhagavad Gita. Secondly, God is not subject to the laws of nature. He created those laws, so He can suspend them, as well.
In fact, Krishna is Time, so He can do with time what He wants. Is it scientifically possible to stop time? No. Can God stop time? He certainly can. It is said that in the eternal, spiritual world, time is conspicuous by it’s absence. So both Krishna and the spiritual world, as well as all the liberated souls there, are not influenced by time.
Like when Arjuna, during the battle, went after Jayadratha, who had killed his son Abhimanyu, Krishna delayed the setting of the sun, so Arjuna had time to kill Jayadratha before the sun set. Arjuna had vowed to kill Jayadratha that day, before sun down, and if he didn’t succeed, he would enter fire and kill himself.
So Arjuna plowed through 12 miles of warriors, that Duryodhana had arranged around Jayadratha to protect him, and just as Arjuna was within sight of Jayadratha, the sun set. Jayadratha and all the Kauravas, thinking they had baffled Arjuna in his vow, and that he would now have to enter fire, were jubilantly dancing and shouting with glee.
But at that time Krishna, just as the sun was disappearing under the horizon, pushed the sun up again, and Arjuna swiftly fired a crescent shaped arrow that cut off Jayadratha’s head.
Jayadratha’s father had given Jayadratha the benediction that anyone, who made his head touch the ground, that person’s own head would explode. Knowing this, Arjuna directed, by mantras, the crescent shaped arrow carrying Jayadratha’s head, to the place where Jayadratha’s father was sitting in meditation, and dumped the head in his lap. When Jayadratha’s father felt a head being dumped in his lap, he looked down and revulsed, causing his son’s head to drop to the ground, and his head exploded. So it’s no problem for God and His devotees to break the laws of nature :D
In his book, Teachings of Queen Kunti, Srila Prabhupada writes:
It is described in Srimad-Bhagavatam that when Krishna first appeared, He did not take birth from the womb of Devaki; rather, He first appeared in the majestic four-armed form of Vishnu, and then He became a small child on Devaki's lap. Therefore Krishna’s birth is transcendental, whereas our birth takes place by force, by the laws of nature. Krishna is not under the laws of nature; the laws of nature work under Him (mayadhyaksena prakrtih suyate sa-caracaram [Bg. 9.10]).
Prakriti, nature, works under the order of Krishna, and we work under the order of nature. Krishna is the master of nature, and we are servants of nature. Therefore Kuntidevi says, kecid ahuh: "Someone may say that the unborn has taken birth."
It may appear that He has taken birth just like us, but in fact He has not. Kuntidevi distinctly says, kecid ahuh: "some foolish persons may say that He has taken birth." Krishna Himself also says in Bhagavad-gita (9.11), avajananti mam mudha manusim tanum asritam: "Because I have appeared just like a human being, those who are rascals think that I am also just like an ordinary human."
Param bhavam ajanantah: "They do not know the mystery behind God's taking birth like a human being."
Krishna is everywhere. The Lord is situated in everyone's heart (isvarah sarva-bhutanam hrd-dese 'rjuna tisthati [Bg. 18.61]). And since He is within us and is all-powerful, why should it be difficult for Him to appear before us?
When the great devotee Dhruva Maharaja was engaged in meditation on the four-handed form of Vishnu, all of a sudden his meditation broke, and he immediately saw before him the same form upon which he had been meditating. Was it very difficult for Krishna to appear in this way? Of course not. Similarly it was not difficult for Him to appear before Devaki in the same four-handed form.
Therefore Krishna says, janma karma ca me divyam: [Bg. 4.9] "One must understand My transcendental birth and activities." Kuntidevi has this understanding. She knows that although to some fools Krishna appears to take birth, in fact He is unborn.
But why should Krishna perform the pastime of taking birth? Kuntidevi replies, punya-slokasya kirtaye: [SB 1.8.32] to glorify those who are very pious and very much advanced in spiritual understanding. Krishna comes as the son of Devaki to glorify His devotee Devaki.
Krishna becomes the son of Yashoda to glorify Yashoda. Similarly, Krsna appears in the dynasty of Maharaja Yadu, His great devotee, just to glorify Maharaja Yadu. Thus Krishna is still known as Yadava, the descendant of Maharaja Yadu.
Krishna has no obligation to take His birth in a particular family or country, but He takes birth to glorify a certain person or a certain family because of their devotion. Therefore His birth is called divyam, transcendental.
The Lord is not obliged to take birth, but we are obliged to do so. That is the distinction between our birth and the birth of Krishna. If by our karma, or activities, we are fit to take birth in a good family in human society or demigod society, we shall do so, but if our activities are low like those of animals, we shall have to take birth in a family of animals. That is the force of karma. Karmana daiva-netrena jantor dehopapattaye (SB 3.31.1). We develop a certain type of body according to our karma.
The human form of life is meant for understanding the Supreme, the Absolute Truth (athato brahma jijnasa). But if we do not endeavor for this, if we misuse this opportunity and simply remain like animals, we shall return to an animal form of life. Therefore the Krishna consciousness movement is trying to save people from going down to animal life.
The appearance of Lord Krishna is compared to the growth of sandalwood trees in the Malaya Hills (malayasyeva chandanam [SB 1.8.32]). There are two Malayas -- the Malaya Hills and the part of the world now known as Malaysia.
The chandana tree, or sandalwood tree, can grow anywhere -- there is no rule that it has to grow in Malaysia or the Malaya Hills -- but because this sandalwood grows in large quantities in those parts of the world, it is known as malaya-chandana. In the Western countries there is scented water known as eau de cologne. It can be manufactured anywhere, but because it was originally manufactured in the city of Cologne, it is known as eau de cologne.
Similarly, sandalwood can grow anywhere, but because it was originally very prominent in Malaysia and the Malaya Hills, it is known as Malayan sandalwood. Kunti offered this prayer five thousand years ago, and this indicates that sandalwood was growing five thousand years ago in Malaysia. Malaysia is not a new name; it was known thousands and thousands of years ago to the followers of the Vedic culture.
Nowadays, of course, Malaysia is growing rubber trees because there is a good demand for rubber, but formerly Malaysia grew sandalwood on a large scale because there was a great demand for sandalwood, especially in India.
Because India is a tropical country and sandalwood is very cooling people in India use sandalwood pulp as a cosmetic. Even now, during the very warm days of the summer season, those who can afford to do so apply sandalwood pulp to their bodies and feel cool all day. In India it was the system that after bathing and sanctifying the body by applying marks of tilaka, one would offer obeisances to the Deity, take some chandana-prasada from the room of the Deity, and apply it as a cosmetic to the body. This was called prasadhanam. But it is said that in Kali-yuga, the present age, snanam eva prasadhanam (SB 12.2.5): if one can even bathe nicely, that is prasadhana.
In India even the poorest man will take an early morning bath every day, but when I came to America I saw that even taking one's daily bath may be a difficult thing and is often not the practice. In India we are accustomed to see people bathe thrice in a day, but in New York I have seen that one may have to go to a friend's house to bathe because one may not have facilities to do so at home. These are symptoms of Kali-yuga. Snanam eva prasadhanam. In the Kali-yuga it will be very difficult even to take a bath.
Another symptom of Kali-yuga is daksyam kutumba-bharanam (Bhag. 12.2.6): one will be famous for his pious activities simply if he can maintain his family. The word daksyam, meaning "famous for pious activities," comes from daksa, which means "expert."
In Kali-yuga one will be considered expert if he can maintain a family consisting of himself, his wife, and one or two children. In India, of course, the traditional family is the joint family, consisting of a man and his wife, their parents and children, their in-laws, and so on. But in Kali-yuga it will be difficult to maintain a simple family of oneself, one's wife, and a few children.
When I was living in New York, among the people coming to our classes was an old lady who had a grown son. I asked her, "Why doesn't your son get married?" She replied, "Yes, he can marry when he can maintain a family." I did not know that maintaining a family was such a difficult job here. But this is described in the Bhagavatam: if one can maintain a family, he will be considered a very glorious man, and if a girl has a husband she will be considered very fortunate.
It is not our business to criticize, but the symptoms of Kali-yuga are very severe, and they will grow more severe. The duration of Kali-yuga is 432,000 years, and although only 5,000 years of it have passed, already we find so many difficulties, and the more we grow into this Kali-yuga, the more the times will be difficult. The best course, therefore, is to complete our Krishna consciousness and return home, back to Godhead. That will save us. Otherwise, if we come back again for another life in Kali-yuga, we shall find difficult days ahead, and we shall have to suffer more and more.