|Model of the Golden Altar [A]|
|Olfactory - Brain Connection [B]|
One theory why smell is so powerful goes back to the garden of Eden.
Why incense? the Bnei Yissakhar explains that when man sinned in Eden all the senses were corrupted, save one: Eve listened to the words of the Serpent, she saw the tree, touched the tree, ate from the tree; the only sense not corrupted was the sense of smell. Therefore when the kohen gadol (high priest) enters the Holy of Holies to seek forgiveness for the transgressions of the nation, he arms himself with incense, falling back on the one remaining oasis of purity. (Echoes of Eden: Sefer Shmot, By Ari D. Kahn) 
After Eating the Forbidden Fruit [C]
One could argue that smell is involved in taste, which would invalidate Mr Kahn's assertion, but smell is not mentioned in the text of Gen 3. And note that incense is put on the golden altar twice a day, not just on Yom Kippur.
What does incense have to do with the birth of Christ?
The priests that served at the temple in Jerusalem gathered every morning to cast lots for their service that day.
The first lot was for cleansing the altar and preparing it; the second, for those who were to offer the sacrifice, and for those who were to cleanse the candlestick and the altar of incense in the Holy Place. The third lot was the most important. It determined who was to offer the incense. If possible, none was to take part in it who had at any previous time officiated in the same capacity. The fourth lot, which followed close on the third, fixed those who were to burn the pieces of the sacrifice on the altar, and to perform the concluding portions of the service. Then something miraculous happened concerning Zacharias, the father of John the Baptist.
It is this burning of incense which in the Gospel is alluded to in connection with the birth of John the Baptist (Luke 1:9). Zacharias had come up from the hill country of Judea, from the neighbourhood of priestly Hebron, to minister in the Temple. His course--that of Abia--was on duty for the week, and the house of his fathers' for that special day. More than that, the lot had fallen on Zacharias for the most honourable service in the daily ministry--that of burning the incense on the golden altar within the Holy Place. For the first time in his life, and for the last, would this service devolve on him. As the pious old priest ministered within the Holy Place, he saw with such distinctness that he could afterwards describe the very spot, Gabriel standing, as if he had just come out from the Most Holy Place, between the altar and the table of shewbread, on the right side of the altar.' So far as we know, this was the first and only angelic appearance in the Temple. 
Zacharias Sees Gabriel [D]
Luke's account is more modest, not mentioning the fact that being the "incensing priest" was a big honor, once in a lifetime. But that big honor was dwarfed by meeting angel Gabriel and receiving news that he and Elizabeth would have a son, who would be great in the sight of the Lord. What a day for Zacharias. Then he was struck dumb until John was named.
5 In the days of Herod, king of Judea, there was a priest named Zacharias, of the division of Abijah; and he had a wife from the daughters of Aaron, and her name was Elizabeth. 6 They were both righteous in the sight of God, walking blamelessly in all the commandments and requirements of the Lord. 7 But they had no child, because Elizabeth was barren, and they were both advanced in years. 8 Now it happened that while he was performing his priestly service before God in the appointed order of his division, 9 according to the custom of the priestly office, he was chosen by lot to enter the temple of the Lord and burn incense.
11 And an angel of the Lord appeared to him, standing to the right of the altar of incense. 12 Zacharias was troubled when he saw the angel, and fear gripped him. 13 But the angel said to him, "Do not be afraid, Zacharias, for your petition has been heard, and your wife Elizabeth will bear you a son, and you will give him the name John. 14 "You will have joy and gladness, and many will rejoice at his birth. 15 "For he will be great in the sight of the Lord;
Edersheim fills in details. Note the expectation of silence
Slowly the incensing priest and his assistants ascended the steps to the Holy Place, preceded by the two priests who had formerly dressed the altar and the candlestick, and who now removed the vessels they had left behind, and, worshipping, withdrew. Next, one of the assistants reverently spread the coals on the golden altar; the other arranged the incense; and then the chief officiating priest was left alone within the Holy Place, to await the signal of the president before burning the incense. It was probably while thus expectant that the angel Gabriel appeared to Zacharias. As the president gave the word of command, which marked that the time of incense had come,' the whole multitude of the people without' withdrew from the inner court, and fell down before the Lord, spreading their hands in silent prayer. 
But if it had been the duty of Zacharias, as incensing priest for the day, to lead in the priestly blessing, we can all the better understand the wonder of the people as he beckoned unto them, and remained speechless' (Luke 1:22) while they waited for his benediction. 
Zacharias was alone in the Holy Place, and all the people outside waited in silent prayer till he lit the incense and came out to do the blessing. In other words, they expected silence, but not that long.
Zacharias' wife Elizabeth became pregnant in her old age, her son was John the Baptist - he would have been a priest. Elizabeth was a cousin of Mary, mother of Jesus. John the Baptist would be six months older than Jesus.
Bible scholars use these events to date the birth of Jesus. Unfortunately, they don't all agree.
Silence In Heaven For Half An Hour
One piece of foreshadowing occurs in this story as well. Just as silence is expected from the worshipers before the lighting of the incense, there is silence in heaven "for about a half hour" right after opening the seventh seal, right before lighting the incense.
My take is it's like a parent who is really mad doesn't say anything at all. Or maybe the divine silent treatment.
Rev 8;1And when he opened the seventh seal, there followed a silence in heaven about the space of half an hour. 2And I saw the seven angels that stand before God; and there were given unto them seven trumpets. 3And another angel came and stood over the altar, having a golden censer; and there was given unto him much incense, that he should add it unto the prayers of all the saints upon the golden altar which was before the throne. 4And the smoke of the incense, with the prayers of the saints, went up before God out of the angel’s hand. 5And the angel taketh the censer; and he filled it with the fire of the altar, and cast it upon the earth: and there followed thunders, and voices, and lightnings, and an earthquake.
Scroll With Seven Seals [E]
Bitter Makes It Better
|Ferula gummosa, from which galbanum comes. [F]|
One More Thing
In Heb 9:3-4 we read "Behind the second curtain was a room called the Most Holy Place, 4 which had the golden altar of incense and the gold-covered ark of the covenant." But in Exodus, it clearly says the golden altar is in front of the veil. Is God rearranging furniture in the tabernacle? Does the author of Hebrews not know where the golden altar is? Not at all. The confusion is in the word translated as golden altar. The commentaries agree that it also means golden censer, the pan used to burn the incense. Many translations in fact say golden censer. Beware of theology based on the altar inside the Holy of Holies. By tradition, the golden censer was only used on Yom Kippur - every other day it was silver. That is, the subject of Hebrews 9 is Christ entering the Holy of Holies in heaven itself pictured by the High Priest on Yom Kippur.
3. https://books.google.com/books?id=pXYIf4BeOkQC, p228
4. Edersheim, Alfred. The Temple- Its Ministry and Services (Kindle Locations 1486-1489).
5. Edersheim, Alfred. The Temple- Its Ministry and Services (Kindle Locations 1581-1587).
6. Edersheim, Alfred. The Temple- Its Ministry and Services (Kindle Locations 1678-1681).
7. Edersheim, Alfred. The Temple- Its Ministry and Services (Kindle Locations 1713-1715).