Both reactions involve the nucleus of an atom, and in both reactions, lots and lots of energy are released. Other than that, the two reactions are pretty much opposite. Fission involves the splitting of an atomic nucleus. Fusion involves the fusing of two or more smaller units to create a new, heavier nucleus.

Answered by Nitheesh S , an ibibo Citizen, at 10:15 AM on November 18, 2008

In nuclear physics and nuclear chemistry, nuclear fusion is the process by which multiple like-charged atomic nuclei join together to form a heavier nucleus. It is accompanied by the release or absorption of energy. Iron and nickel nuclei have the largest binding energies per nucleon of all nuclei. The fusion of two nuclei with lower mass than iron generally releases energy while the fusion of nuclei heavier than iron absorbs energy; vice-versa for the reverse process, nuclear fission.
Nuclear fusion occurs naturally in stars. Artificial fusion in human enterprises has also been achieved, although not yet completely controlled. Building upon the nuclear transmutation experiments of Ernest Rutherford done a few years earlier, fusion of light nuclei (hydrogen isotopes) was first observed by Mark Oliphant in 1932, and the steps of the main cycle of nuclear fusion in stars were subsequently worked out by Hans Bethe throughout the remainder of that decade. Research into fusion for military purposes began in the early 1940s, as part of the Manhattan Project, but was not successful until 1952. Research into controlled fusion for civilian purposes began in the 1950s, and continues to this day.

Answered by Amar Jha , an ibibo Advisor, at 1:31 AM on November 14, 2008

fussion join two lighter elements formimg a more massive element and releasing more enrgy .
fission splits massive element into fragments ,releasing energy in the process.

Answered by Aryan Raj , an ibibo Citizen, at 12:23 PM on November 13, 2008

fusion reaction:-
nuclear fusion is the process by which multiple like-charged atomic nuclei join together to form a heavier nucleus. It is accompanied by the release or absorption of energy.

fission reaction:-
nuclear fission is a nuclear reaction in which the nucleus of an atom splits into smaller parts, often producing free neutrons and lighter nuclei. Fission of heavy elements is an exothermic reaction.

Answered by Ajay Kumar , an ibibo Citizen, at 11:14 AM on November 12, 2008

Fission is the process of splitting of a heavier nucleus into fragments of smaller mass by bombardment with slow moving neutrons.
Fusion is the is a process in which lighter nuclei of atoms fuse together to form a heavier nucleus.

Answered by Abhijeet , an ibibo Citizen, at 8:59 PM on November 11, 2008

NUCLEAR FUSION is the fusing of two particles,i.e. two particles combine togrther into one and in this process they release energy. FOR EX--- atom bombs use the nulear fission process.

NUCLEAR FISSION is the process where a big particle break downs into many more such relatively small particles.This process again releases nuclear energy.

In other words you can simply say that fission involves the breakdown of the big particle whereas FUSION involves the combinning of the many paricles ti form a single particle
AND in both these processes NUCLEAR ENERGY is released.

Answered by Abhinav , an ibibo Citizen, at 3:39 PM on November 11, 2008

fission is a reaction where big molecules breaks into small molecules and makes energy. This is the reaction which happens in Atom Bomb.
Fusion is just reverse in this small molecules meets and make big molecule. This is the reaction which happens in SUN.
Also refer to following websites :
http://www.lancs.ac.uk/ug/sutton d1/

Answered by ASHISH , an ibibo Citizen, at 2:52 PM on November 11, 2008