Question

what is mass?
what is time? define them

Answer 1

Mass is a measure of how much matter is in an object. What do you mean by define time?

Answer 2

I am only beginning, but here is what I learned so far:

Mass: According to the Standard Model, mass is the aggregation of Higgs' bosons around a particle. The consequences of this aggregation are the known phenomena of inertia and gravity.

Time: According to the Relativity Theory, time is a component of the space-time continuum, which means that it is closely related to space and can only exist in association with it. As a dimension, time can be modeled as an axis along which events can be placed in an ordered manner, forming notions of "after", "before", "future", "past" and the notion of simultaneity. As a part of the space-time continuum, time can be bent by the presence of massive objects and this bending is part of the phenomenon we call "gravity". Also, time can be expanded around an object as it accelerates, culminating in the theoretical possibility of the object to become almost "frozen" in time, if it accelerates to a speed which corresponds to a sufficiently high percentage of the speed of light. Time is also thought to be infinitely stretched at the event horizon around a black hole (the frontier where the escape velocity for the gravity field of the black hole equals the speed of light).

Hope this was helpful.

Answer 3

To put it in simple words, Mass is a property of the things around us which shows their resistance to change in velocity.

Actually, Mass is of 2 types.The one I mentioned is the Inertial mass.
The other is the gravitational mass: A property of matter by the virtue of which one object attracts another.
I am not sure whether both these masses of the same body agree with each other all the time.

Time is the perception that gives an order of occurrence events taking place in the universe.This perception can vary from species to species.
For example: The perception of time by a snail is so poor that, when it looks at itself walking, It doesn't find that it is slow at all.
While for certain birds, the human movements look like picture in a very slow motion. It is because their perception is so sharp.

Answer 4

Siva, I guess we can add our responses together:

Mass is better defined as the measure of the strength of the interaction of a particle with the Higgs Field. The mass of a particle is a constant and works equally for both gravitation and inertia (but see the MOND hypothesis by Mordehai Milgrom).

Tim, on the other hand, can have two interpretations:

a) Under the perspective of Physics, it is a dimension, just as height, width and length), the properties of which are still a matter of debate and intense research.

b) Under the perspective of neuroscience, it is a property of the mind that tries to order events in an intelligible way (for significantly sentience-capable brains) and can be quite different from species to species, from person to person and event from moment to moment in a same person (time flies when we have fun).

There are other interpretations (I remember a Rabbi who introduced the notion of a "hypertime" to be used when analysing the flow of events related to the jewish god, as an example), but those are the most fitting in science that I can remember right now.