Hi, Exporter.
When I see a question such as yours, I rely heavily on the “Catechism of the Catholic Church”. I fear that my wording may be inaccurate or may unintentionally mislead.
So, I’m a friendly fellow, despite the quotations of the CC, which may appear to be a “sterile” way to answer.
Exporter:
Some how that word “sacrifice” isn’t understood by me. When during the Mass does the “sacrifice” take place. Am I to believe that Christ’s agony and death on the cross actually is taking place on the Alter? Or is it a contenuation of His death on the cross in Jerusalem?
It’s is not a “continuation” of His death, as He died ONCE.
The more accurate word is “re-presentation”. The Sacrifice of Calvary is made present during Holy Mass. We are AT Calvary.
I italicize portions of the CCC.
*1330 The memorial of the Lord’s Passion and Resurrection.
The Holy Sacrifice, because it makes present the one sacrifice of Christ the Savior and includes the Church’s offering. The terms holy sacrifice of the Mass, “sacrifice of praise,” spiritual sacrifice, pure and holy sacrifice are also used,150 since it completes and surpasses all the sacrifices of the Old Covenant*
[snip]
*1365 Because it is the memorial of Christ’s Passover, the Eucharist is also a sacrifice. **The sacrificial character of the Eucharist is manifested in the very words of institution: “This is my body which is given for you” and “This cup which is poured out for you is the New Covenant in my blood.”**187 In the Eucharist Christ gives us the very body which he gave up for us on the cross, the very blood which he "poured out for many for the forgiveness of sins."188
1366
The Eucharist is thus a sacrifice because it re-presents (makes present) the sacrifice of the cross, because it is its memorial and because it applies its fruit:
[Christ], our Lord and God, was once and for all to offer himself to God the Father by his death on the altar of the cross, to accomplish there an everlasting redemption. But because his priesthood was not to end with his death, at the Last Supper “on the night when he was betrayed,” [he wanted] to leave to his beloved spouse the Church
a visible sacrifice (as the nature of man demands) **by which the bloody sacrifice which he was to accomplish once for all on the cross would be re-presented, its memory perpetuated until the end of the world, and its salutary power be applied to the forgiveness of the sins we daily commit.**189
1367 The sacrifice of Christ and the sacrifice of the Eucharist are one single sacrifice: “The victim is one and the same: the same now offers through the ministry of priests, who then offered himself on the cross; only the manner of offering is different.” "And since in this divine sacrifice which is celebrated in the Mass, the same Christ who offered himself once in a bloody manner on the altar of the cross is contained and is offered in an unbloody manner. . . this sacrifice is truly propitiatory."190 *
I hoped that helped you some.
The way that I explain it (and I am Joe Average, not a licensed theologian) is this:
Imagine that in heaven above the Earth is a string of light down to the Last Supper, which is the First Mass. (in Earth chronological terms) And from that same source of Light, Christ himself, is another string of light to Calvary
And from that same source of Light. Christ, is a string of light to each and every spoken Holy Mass throughout time.
And around that same source of Light are the angels and Saints who are actively participating in worshipping the Lord. This heavenly worship is THE Mass.
All the masses through time are THE Mass.
We humans perceive the chronologically separate individual “events” as 'Masses", yet these are ONE Mass.
