Hare Krsna-Below you will find a lot of nectar by SP regarding universal makeup, its creation, pathways between planets and much more. All this was in letters he wrote to his scientist disciples. I took these from the
Prabhupada Siksamrta, Volume #1. This 3 book volume is full of unlimited nectar.
damaghosa das
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March 9 1970 letter to Hayagriva
Regarding your question do the Vedic histories refer to this planet only. No. Vedic history means of this universe. Our history begins from the beginning of the creation because the creation takes place with the birth of Brahma from the abdomen lotus flower of Lord Visnu. Then Brahma gradually creates. He begets so many sons known as Prajapatis who are supposed to be the generators of living entities, and therefore the history begins from Brahma. In the Bhagavad-gita this is confirmed in the 15th chapter. It is said there that the root of this big universal banyan tree is on the top; therefore history begins from the top.
Yes. This planet comes later on. We can take the idea from the tree—the tree grows gradually, and the different fruits, branches, and twigs gradually appear. Therefore it is to be understood that this planet has grown later on. Besides this we understand that although the planet was later on grown up, it was covered with water—pralaya payodhi jale **, merged into the water after devastation. Then gradually it emerges from water. That we can experience, that gradually land is coming out of the oceans. Because of its being merged into water, it is natural to conclude that the beginning of life was aquatic. This is confirmed in Padma Purāṇa that the species of life evolved from aquatics to plants, vegetables, trees; thereafter insects, reptiles, flies, birds, then beasts, and then human kind. This is the gradual process of evolution of species of life.
But we do not accept Darwin’s theory. According to Darwin’s theory, homo sapiens came later on, but we see that the most intelligent personality, Brahma, is born first. So according to Vedic knowledge, Darwin or similar mental speculators are rejected so far the fact is concerned

Note-SP is not saying all these life forms evolved from one into another , lower to higher.

Jan 20 1968 Rupanuga letter
Regarding your question of the planetary systems, the planets are arranged in each universe in layers like the petals of a lotus. But in each layer there is mixed both heavenly, hellish and middle planets. On the outside layer there are these three kinds of planets, on the middle layers there are the three kinds of planets and on the inner-most layer there are found these three kinds of planets. Above these layers, in the center, is the Brahmaloka where Lord Brahma, the creator is residing. So the earth planet and the moon planet are both on the same layer but the earth is middle planet and the moon is heavenly planet.

July 9 1971 letter Jadurani
Krishna appeared as Narayana and when requested, he became a baby. But the picture is all right; The position of the four symbols for all three purusa avataras is the same; All the planets within the stem, that is to be understood. But they are seedling planets and are coming out of the stem, all below the lotus flower, just as seedling universes come out from the body of Maha Visnu; You don’t have to paint the subtle bodies

April 27 1976 letter Svarupa damodara
Please accept my blessings. Now our Ph.D’s must collaborate and study the 5th Canto to make a model for building the Vedic Planetarium. My final decision is that the universe is just like a tree, with root upwards. Just as a tree has branches and leaves so the universe is also composed of planets which are fixed up in the tree like the leaves, flowers, fruits, etc. of the tree. The pivot is the pole star, and the whole tree is rotating on this pivot. Mount Sumeru is the center, trunk, and is like a steep hill, like the alps mountains which also have very high peaks. I have seen in Switzerland one mountain peak which was so high that is penetrated through the clouds. The tree is turning and therefore, all the branches and leaves turn with the tree. The planets have their fixed orbits, but still they are turning with the turning of the great tree. There are pathways leading from one planet to another made of gold, copper, etc., and these are like the branches. Distances are also described in the 5th Canto just how far one planet is from another.
We can see that at night, how the whole planetary system is turning around, the pole star being the pivot. Each planet has its orbit fixed but the sun is moving up and down, north and south. It is not that we shall accept the theory that the sun is fixed up and the others are all going around the sun. That is not correct. Even the 7th star is rotating once around the pole star in each 24 hours. The whole universe is just like a big tree, that is a fact. I do not think that the modern astronomers have any such idea that the whole universe is like a big tree. The planets which are full of living entities are one after another, one above the other. The relative positions of the planets is fixed up but the whole thing is turning. The sun is going north and south, it has its own orbit below the moon. So now you all Ph.D.’s must carefully study the details of the 5th Canto and make a working model of the universe. If we can explain the passing seasons, eclipses, phases of the moon, passing of day and night, etc. then it will be very powerful propaganda.
I am sending this letter to you, and you can make photocopies of it and send to our other Ph.D.’s and begin serious research into the matter in detail. But one thing, I am convinced that the universe is just like a great tree as described therein.

Aug 27 1967 letter Jananivasa
Yes, anything of which we have no conception, the unknown particle, that is the representation of Paramatma. Yes, your interpretation is quite feasible, because from the Vedic literature that spiritual particle is measured as 1/10,000 part of the upper portion of the hair. So if the physicist’s conclusion about the measurement of the soul, that is 100 times finer than what they are already discovered. But however fine and smallest it may be, there is measurement of spirit soul, maybe beyond the experimental knowledge of human scientists. The confusion must continue because this measurement of spirit soul is beyond the range of experimental mind, and understanding. Therefore, confusion. Therefore you have to accept the experience of spirit soul from Vedic literature. If one tries to understand otherwise they will remain in confusion. Subject which is beyond their understanding by experimental knowledge, and if they try to understand it by the same experimental knowledge, that means confusion. This has to be understood by descending process of disciplic succession, or by deductive process, meaning for instance, my mother says this man is my father, I accept, there is no experience. God’s name is therefore Adhoksaja which means beyond experimental knowledge. You can inform them that here is statement in Vedic literature (Padma Purāṇa) that the measurement of soul is 1/10,000 of the upper portion of the hair. You are meant for doing this and I shall assist you as far as possible. I thank you for your promise to send me one letter a week.

Feb 10th 1969 letter to Govinda dasi
Regarding your German acquaintance, I understand that he may be a very intelligent man and believes in science. But even the most advanced scientist depends on the statements of authorities. Science begins on some definite data, just like Sir Isaac Newton discovered the law of gravitation, and so much scientific advancement depends on such authoritative statements. So even scientific knowledge has to stand on the evidence of authority. He admits that we are all spirit soul inside the body entrapped, and he believes this body is composed of various chemicals about which we know a great deal. But unfortunately, with all this chemical combinations combined together, we can not produce a body like this; this is also a scientific fact. Just like rasgulla is a milk product everyone knows. But how to make a rasgulla from milk requires expert further knowledge. Therefore, simply to know that this body is made of chemicals is not sufficient knowledge. When one can reproduce a similar body with the known chemicals, then he is to be considered as the expert scientist. The spirit soul is impossible to find out by materialistic scientific means, but if one will hear from the right authority, he may understand.

March 2 1969 letter to Janardana
We should train our disciples as well as ourselves in such a spirit that even if the whole world is against us, which is impossible to happen, the Sankirtana Movement must be pushed on without any reference to archeological evidence or any such scientific advancement of knowledge. Besides that, the argument that archeological evidence will lead many people to accept the philosophy of Lord Caitanya has no evidence. For example, the Christian religion principle is now established in archeological evidence, but still it is not that the whole people of the world are attracted by Christian religion. Even a great scientist, Professor Albert Einstein, was Jewish by religion, but because the Christian religion gives evidential proof of archeological discovery, still he did not become a Christian. No religion or no principle is accepted by the whole world; that is a fact. I can give you a statement of Albert Einstein in which he says “The most beautiful and most profound emotion we can experience is in the sensation of the mystical. It is a shower of all true science. He to whom this emotion is a stranger, he who can no longer stand rapt in awe, is as good as dead. That deeply emotional conviction of the presence of a superior reasoning power which is revealed in the comprehensible universe forms my idea of God.”

Dec 12 1971 letter Danavir
Also it is nice that you are infiltrating into the schools and colleges. These are the best customers for our philosophy. Give them nice philosophy, let them challenge us with any mundane philosophy and we shall very scholarly defeat them. The difference is that we have got absolute authority from the Source of Knowledge, Krishna, while your western mundane philosophers are simply speculating on the mental platform, which is always changing. Therefore, a philosopher is not a philosopher unless he refutes his predecessor and produces something new. This kind of knowledge is useless. Actually, no one has got any philosophy nowadays, everyone is acting according to his own whims. Therefore there is no security, no peace, everything is unpredictable and dangerous. Therefore all the young boys and girls in your country—and all over the world—are fed up with this lack of philosophy and they have taken to the philosophy of hopelessness: Everything is empty, therefore let me enjoy, it doesn’t matter. But this philosophy is also useless. Because if you want to enjoy and I also want to enjoy, there will be clash, fighting. And we have seen in Moscow that Marx and Lenin philosophy is no better. God is dead, the State is God: this philosophy has killed the spirit, and the Russian people are very morose and unhappy. They want to join us, that is a fact. So now you defeat all sorts of philosophies, become very convinced yourself and learn our Krishna philosophy perfectly. In this way, any sane man will listen to you and become convinced. Our philosophy is practical. Actually, philosophy means practical application—if it is mere theory then it has no value. But our Krishna philosophy is working now in modern society to solve all kinds of problems, all over the world, never mind white man, black man,

Nov 7 1972 letter Krsna dasa
Please accept my blessings. I beg to acknowledge receipt of your letter dated October 30, 1972, and I have noted the contents. It appears that you are again constantly disturbed by the same nonsense doubts. These things are not very important, we may not waste our time with these insignificant questions. If we are seeking to find out some fault, maya will give us all facility to find any small thing and make it very big, that is maya. But such questions as yours: why there is so-called discrepancy between the views of Bhagavat and modern scientists regarding the moon and other planets, and whether Hitler is good or bad man, these are most insignificant matters, and for anyone who is sincerely convinced that Krishna is the Supreme Personality of Godhead, for him these questions do not arise. Our information comes from Vedas, and if we believe Krishna, that
vedaham samatitani vartamanani carjuna bhavisyani ca bhutani mam tu veda na kascana [Bg. 7.26] that He knows everything, and “vedais ca sarvair aham eva vedyo vedanta-krd veda-vid eva caham [Bg. 15.15],” that Krishna is non-different from Vedas, then these questions do not arise.

Jan 21 1968 letter Janardana
Yes, anything of which we have no conception, the unknown particle, that is the representation of Paramatma. Yes, your interpretation is quite feasible, because from the Vedic literature that spiritual particle is measured as 1/10,000 part of the upper portion of the hair. So if the physicist’s conclusion about the measurement of the soul, that is 100 times finer than what they are already discovered. But however fine and smallest it may be, there is measurement of spirit soul, maybe beyond the experimental knowledge of human scientists. The confusion must continue because this measurement of spirit soul is beyond the range of experimental mind, and understanding. Therefore, confusion. Therefore you have to accept the experience of spirit soul from Vedic literature. If one tries to understand otherwise they will remain in confusion. Subject which is beyond their understanding by experimental knowledge, and if they try to understand it by the same experimental knowledge, that means confusion. This has to be understood by descending process of disciplic succession, or by deductive process, meaning for instance, my mother says this man is my father, I accept, there is no experience. God’s name is therefore Adhoksaja which means beyond experimental knowledge.

Feb 10 1969 letter to Govinda
The spirit soul is impossible to find out by materialistic scientific means, but if one will hear from the right authority, he may understand. The gentleman is disappointed that probably no one will ever know about spirit, but this is not true. We know what is spirit, how does it work, how does it transmigrate from one body to another or from one planet to another. We know these very scientifically, and we are firmly convinced about it. We can refute any dogmatic arguments against this conviction, and how do we do that? Simply because we start our understanding from the data of authoritative sources like Krishna or His representative. In the Bhagavad-gita, Lord Krishna speaks about spirit soul from the very beginning. Unless one understands what is this spirit soul, his further advancement of the Supreme Spirit God has no value.

Jan 23 1970 letter Hamsadutta
Regarding your question: you are right when you write to say that everything about us, tables, chairs, bricks etc. is originally emanating from sound vibration. This is also admitted in the Christian Bible wherein it is said that God said, Let there be creation. And there was creation. So, “said” means it was sound vibration; but this sound vibration is not material sound vibration because before creation of material sky and sound, transcendental sound was there. So actually the transcendental sound is the cause of creation, but material sound is not transcendental sound. We have to receive transcendental sound through the transcendental channel, therefore, Vedas are called Sruti. That means transcendental sound can be received through the ear. And by hearing this transcendental sound through the ear our heart becomes spiritually purified, and we can realize at that stage the transcendental Name, transcendental Qualities, transcendental Form, transcendental Pastimes etc. That is the way of descending process.

Nov 17 1971 letter to Brhaspati
Try to interest these students in our books. If you simply stick to the textbook teaching becomes very easy. Philosophy is the highest, but even higher than philosophy is practice of philosophy. So when your students apply Krishna philosophy to their lives, they will feel the beneficial result, and this will make your teaching work very easy. Just like you add hydrogen and oxygen and get water. So let them chant and learn Bhagavad-gita and they will get Krishna’s mercy. I am successful in my teaching work because I have not deviated one inch from my Spiritual Master’s instruction, this is my only qualification.

Dec 8 1971 letter Upendra
You say that you have met people who claim that by evolution we are approaching a higher stage of existence. That is true in one sense, that anyone who takes to Krishna Consciousness may elevate himself to the highest status of life. Krishna mentions many types of higher beings in Bhagavad-gita, such as demigods and those who dwell on higher planets. We have information that there are 8,400,000 species of life. Out of these, 400,000 species are considered human life. Of these 400,000, how many species do we find in our experience? Not many, probably less than 1,000, so we must conclude that there are hundreds of thousands of higher and lower types of human forms. But this does not mean that automatically one body evolves into a higher body. No. It is described by Krishna how the soul becomes embodied according to his desire. So there are 8,400,000 types of bodies eternally existing. Not that the appearance of a new form in this world means that form has never existed previously. No, as conditions change on this earth planet, the living entities here desire to enjoy in a different way, so they take a different type of body. Even that body may be new here, it has always existed also somewhere else. So if a man qualifies for that body, he may be rewarded the body of superman, as he desires. So if someone wants such body, he must learn the process for acquiring it, that is Bhagavad-gita.

Dec 8 1971 letter Upendra
Practically speaking, history tells us that human life is becoming more and more degraded in respect of good qualities. Even there may be some temporary advancement of technology, where is the question of being higher than previously? In Vedic literature we find description of all kinds of wonderful machines, like great airplanes which moved as fast as the mind on the principle of sound vibration. Where is that science now? And how is their science advancing when their sons are all becoming hippies who have no interest in such science? Compare our so-called knowledge today with the giant brains who gave us Vedic literature. No poetry, no science, no philosophy, no religion, no culture, no knowledge we have today can be said to be superior to that we find 5,000 years or more ago in India. So where is the question of advancement of civilization? We cannot create even one flower, what to speak of one sun, so we should not be hopeful that in this material atmosphere there will be any kind of improvement at all. Better to become closely associated with the Supreme Perfect, then we shall know what is perfection of our life. This is the culmination of evolution.

June 5 1973 letter Revatinanda
Yes, your article is very nice. It is very important that we now expose the nonsense theories of these rascal scientists who assert that life comes from matter. They say that life comes from some chemicals, but they cannot say wherefrom these chemicals have come. Actually, if we examine carefully, chemicals are coming from life, not life from chemicals. Just like the lemon tree. It is producing so many lemons. In each lemon there is so much citric acid. So, due to the presence of life, so many chemicals are being produced. Also, I have experienced, that one of my toenails has come off due to infection, but now my body is replacing that nail with another one of the exact size and shape as the one I have lost. If I have got such a potency to create, then what to speak of the Supreme Living Being lord Sri Krsna. If the sub-living entities can produce so much chemicals then what to speak of the Supreme living entity. This is called inconceivable potency. The living being has got an inconceivable potency to create. I do not know how my nail is coming. And the Supreme Living Entity or God, has got unlimited potency to create. I do not think that any reasonable intelligent man or scientist can deny. Aham sarvasya prabhavo, I am the source of everything, [Bg. 10.8].

Oct 24 1975 letter Svarupa damodara
In the words of Bhagavad-gita, they are described as mudhah, mayaya-apahrta jnana. Besides that, can you tell me what is the scientific opinion of the days being consecutively Sunday then Monday, then Tuesday, Wednesday, Thursday, Friday, and last Saturday? What is the history of this set-up? (from Sunday to Saturday).
According to our sastra, sun is first, then moon, then Venus, Mercury, Mars, Jupiter, and Saturn, like that. In other words, from Bhagavatam we understand that the moon is 1,600,000 miles above the sun. If that is true, then is it possible to go to the moon planet by persons who can never imagine to go the distance to the sun planet? Under the circumstances, if we say that they have never gone to the moon planet, is it exaggeration? You are a scientist, I hope you will reply these 2 points scientifically. If the moon planet is actually far away from the sun planet, how they can go there and publish in the paper that the moon planet is the nearest planet.

July 27 1973 letter Karandara
When my Guru Maharaja was present even big, big scholars were afraid to talk with His beginning students. My Guru Maharaja was called “Living Encyclopedia”, he could talk with anyone on any subject. He was so learned—so we should be like that as far as possible. No compromise—Ramakrishna, avataras, yogis, everyone was enemy to Guru Maharaja—he never compromised. Some God-brothers complained that this preaching was chopping technique and it would not be successful. But we have seen that those who criticized, they fell down. For my part I have taken up the policy of my Guru Maharaja—no compromise. All these so called scholars, scientists, philosophers who do not accept Krsna are nothing more than rascals, fools lowest of mankind etc..
So you go on with your work, it is very encouraging to me. Thank you.