Is the mass of the universe constant?

Question

Is there an estimate for the mass of the universe? Has it allways been this, even at the time of the big bang?

Answer 1

The energy of the universe is constant. This doesn't imply that the mass of the universe is constant. The make up of the universe can consist of matter, which has mass, and non-matter, like light, which exists and has a certain energy but no mass. So if you look at the equation just mentioned E=mc^2 as applied to a nuclear reaction you will find that the energy in this reaction is the same before the reaction and after the reaction, but some of the mass dissapears. This is because some of the mass was converted into energy, such as emission of light. So the most exact answer to your question is that the mass of the universe is not constant but the universe has a limited makeup consisting of matter and energy, and the sum of these two never changes.

Answer 2

After reading the highly intelligent and well reasearched answers below I have been hardly game "to go where no man has ever gone before".

If there is an estimate for the mass of the Universe its like asking how many angels are there on a pin head. As galaxies move beyond our vision we can only guess at what has happened to them. The nature of entropy suggests some sort of over all stasis but Hawkins quixotic suggestions about black holes and dark matter make any confidence in any thing, especially something so simple as E=MC^2 silly. It has not even been established that there is only one universe (here we have semantic problems entering the argument.)

Some day in a million years or so, we will have progressed at hopefully a faster rate than our ancestors from the stone age to have a pretty good of what's going on.

In the meantime research and give Nobel Prizes for brilliant science but don't really expect any irrefutable answers soon.

Answer 3

Wow, another great question.

The mass of the universe is NOT constant.

You know of

E=mc^2

?

Well all those stars gotta keep shining some how and the enery comes from destroying mass.

4x Hydrogens turn into 1x helium in a typical reaction in a star.

There is a loss of [i think] 0.07% mass in doing this. Why? It just seems to be the way it is....ask God. .....I'm not kidding, nobody else has a better answer. hehe.

since C is the speed of light [big], E=MC^2 is FLIPPIN ENORMOUS. It keeps the sun shining and us warm[ish]

However, theres a general drain on the universe's mass. Not very big, but still a drain.

That means the universe is getting lighter. According to my Weight Watchers leader, the universe is the only one...

mmmm pi

Answer 4

Ever since physics was developed into its modern form around the time of Newton there were several "conservation laws" which it was believed that all physical theories must conform to. Among these was conservation of mass and conservation of energy. With Einstein's theory of relativity it became apparent that mass and energy can be converted, for example through nuclear reactions that happen in the core of the sun and in nuclear warheads, but also in more mundane situations such as when atomic nuclei absorb and emit photons such as in a flourescent lamp. In this sense, the mass of the universe is constantly changing.

The view of physicists since Einstein is that a more general conservation of mass-energy law is in effect. This means that if one were to add up all the energy, then add in the equivalent energy contributed by the mass, this total would be invariant under any physical process. All our experimental evidence so far supports this theory, up to fundamental uncertainties introduced in quantum mechanics caused by finite measuring times. This would indicate that the mass-energy of the universe is indeed constant and has been up to the time of the Big Bang.

Answer 5

That's a hard question. It's more a question of philosophy than physics.

For the part of the universe that we can see, the assumption that the mass is constant works better to explain the observations.

Note: I'm including the mass equivalent of all the energy out there. E = m c^2, so m = E / c^2.

Answer 6

Cosmologists and particle physicists don't really distinguish between mass and energy. They are one and the same thing.

That said, the total energy appears to be constant over time. There's no reason to think that any disappeared or was created.

A good estimate of the OBSERVABLE mass is 3x10^55 grams.

The expansion rate of the universe would indicate that the total mass is more than that, which has cosmologists and particle guys speculating about dark matter/energy.

Answer 7

No how can it be the mass is being displaced all the time think about it! How can any human calculate the mass of the universe we are not that advanced.Even though some people will try to guess they will be wrong.

Answer 8

Density doesn't have to be constant - it's not implied by the mass / energy equivalence.

Answer 9

I'd have to say no.
The sun and other stars, now even we are changing matter to energy.
The amount of matter and energy in the universe is constant. The ratio of matter to energy would determine the mass.

Answer 10

well.the obvious quick answer is no..because rocks break up and the sun burns gas..and blah blah blah.. but youre asking the UNIVERSE... so rocks break up but where do they go?? theyre still in the universe right? but gas... the suns in the universe burn gasses....well.. arent those gasses heavier after being burned ... or lighter>??? and if a rock hits a sun..it gets burned up.. so no.. because there are CHEMICAL reactions going on ..not just physical..then no,.,, the mass of the universe isnt set.. it does change.. and also on earth... you think the earth gets heavier whith more steel production and more people.. so no.. it does change all the time