Missing Mass without grave reason on a Holy day of obligation such as Sunday or any of the prescribed days for your nation or congregation is classified as breaking the fourth commandment "to keep the Sabbath day". Depending on the circumstances and intent of the will, this can be a mortal or venial sin and should be brought up with a priest in confession.
A mortal sin
Roman Catholic AnswerYes, missing Mass on a Sunday is a sin, if it is deliberate then it can easily be a mortal sin (for those who do not know, one mortal sin is all it takes, if you die with one mortal sin on your soul, you are denied heaven for eternity). It is covered in both the Ten Commandments and the Precepts of the Church, you must attend Mass on all Sundays and Holy Days of Obligation. You may not receive Holy Communion at Mass if you have previously missed a Sunday or Holy Day and have not been to confession.
If a Catholic, without very good reason, misses a Sunday Mass or a Mass on a Holy Day of Obligation, it could be considered a serious sin.
Missing Mass became a mortal sin in the Catholic Church when it was officially declared as such during the Council of Trent in the 16th century.
Not going to mass on Sundays or holy days is considered a mortal sin in the Catholic Church.
To participate in the Eucharist, you must be a confirmed Catholic who is in a state of grace (i.e., who has not committed a mortal sin since the last confession). If you are not Catholic, it is permissible to attend mass, but not partake of the Eucharist.
Roman Catholic AnswerThat would depend on how "bad" you are talking. I live in the southeast and two of our Masses were canceled this weekend due to a hurricane and the resulting curfew in effect. If a priest is physically able, he should always been celebrated Mass for the people on Sunday even if no parishoners can get there. Parishoners obligation to Sunday Mass is contigenent on it being possible to make it there. When looking at how serious it is, remember that normally missing Sunday Mass willfully is a mortal (serious sin that would keep you out of heaven for eternity) sin.
Three things are necessary for a sin to be mortal: It must be grave matter (it must be seriously wrong: murder, missing Mass on Sunday, etc.) One must know that it will offend God. One must choose one's own will anyway. "Look, God, I know that I should get up and go to Mass, I know that you want me to, but I want to lay in bed/go to the beach/whatever so I'm not going to Mass."
MORTAL SIN keeps your soul farther from god
Cloning of humans is definitely a serious (mortal) sin.
Mortal Sin - film - was created in 1970.
One is required to go to Confession if one has mortal sin upon one's soul. The conditions for committing a mortal sin are 1) that the act committed must involve a gravely serious act. 2) One must have full knowledge of the evil of the act. 3) One must give a full consent of the will (Catechism of the Catholic Church 1855, 1857) For Catholics, there exists a grave obligation to attend Sunday mass. "The Sunday Eucharist is the foundation and confirmation of all Christian practice. For this reason the faithful are obliged to participate in the Eucharist on days of obligation [this includes Sunday], unless excused for a serious reason (for example, illness, the care of infants) or dispensed by their own pastor. Those who deliberately fail in this obligation commit a grave sin." (Catechism of the Catholic Church 2181). Thus, if a Catholic knows that he is supposed to go mass on Sunday and that it is a grave sin not to do so, but he willfully decides not to go to mass, then yes a mortal sin is committed. And, if one desires to be forgiven of that mortal sin which has killed ones relationship with God than he/she must go to Confession. If the person is lacking in knowledge of the sinfulness of the act or does not do so willingly (he can't get a ride to mass because his parents don't want to go), then the sin is not mortal but merely venial, wounding one's relationship with God but not killing it. In this case it is not necessary to go to Confession, however, a Catholic may decide to go if he/she wishes.