# Does the amount of matter in the universe stay at a constant amount?

## Main Question or Discussion Point

I was wondering if matter stays at a constant amount. You cannot really destroy anything really because crushing it just turns it into smaller pieces of itself, decomposition turns matter int separate elements, vaporizing just turns matter into gas and burning is a combination of all of the above. I do believe that matter cannot be pulled out of the vacuum of space so it cannot increase. There is no such thing as infinite (in my perspective) because "infinite" does not mean unlimited but rather "uncountable." Therefore finite just means that it can be measured.

*Please go easy on me if I am wrong. I'm only in junior high so I have not taken physics or inorgrganic chemistry as a subject. I've only used what I know so if this sounds illogical or farfetched, please don't judge me

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phinds
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Think about an atom bomb. What does it do?

Bandersnatch
Do you know how nuclear reactions work? Like those in A and H-bombs, or in stars? These reactions convert matter into radiation.
As long as the stars are burning, the total amount of matter in the universe (assuming it's countable) will keep going down.

However, it's a (cough) matter of what you mean by amount of matter. Take a simplified fusion reaction where two deuterium nuclei combine to form a helium nucleus. There's the same number of 'building blocks' the input and output products are made of - two protons and two neutrons on each side of the reaction. And yet, due to their new arrangement they have less mass when combined in a helium nucleus than before (excess being re-radiated). Does it mean there is less matter afterwards (there's less mass in a nucleus) or not (the same number of building blocks)?

You decide!

edit: normal burning (like oxidation) does the same thing, by the way. A molecule after burning is more tightly bound (=less mass) than the progenitors taken separately, with excess being re-radiated.

phinds
Gold Member
2019 Award
Ah ... you spilled the beans. I was trying to get him to check it out himself. Fortunately, he has you to do his research for him

Bandersnatch
Sorry old horse, we posted at the same time. I'm not sure if you can expect a junior high schooler to easily understand mass deficit in nuclear reactions, though. I know it'd fly over my head at that age.

berkeman
Mentor
horse
Dat's a funny looking horse! :-)

Bandersnatch
Dat's a funny looking horse! :)
Sorry, old beast, I can't hear you over all the Monty Python sketches I've been watching recently.

phinds
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2019 Award
Sorry old horse, we posted at the same time. I'm not sure if you can expect a junior high schooler to easily understand mass deficit in nuclear reactions, though. I know it'd fly over my head at that age.
Yeah, I agree but I was trying to get him to do a bit of research, which would have quickly introduced the concept of matter turning into radiation.

phinds
Gold Member
2019 Award
Dat's a funny looking horse! :)
Arf ! I agree.

By matter decreasing, I'm not referring to it's mass. What I mean is that could matter be destroyed with there being no remnants of it. Antimatter collisions can cause all "building blocks" to explode. My question is can matter be destroyed completely. No transmutation, no mass decreased atoms no trace of the matter. Sort of like extinction a family. No direct generations left to continue the genetic code.

mathman
Matter can be converted to energy and vice versa. A more fundamental question - does the total remain constant?

Bandersnatch
By matter decreasing, I'm not referring to it's mass. What I mean is that could matter be destroyed with there being no remnants of it. Antimatter collisions can cause all "building blocks" to explode. My question is can matter be destroyed completely. No transmutation, no mass decreased atoms no trace of the matter. Sort of like extinction a family. No direct generations left to continue the genetic code.
I'm not sure I get your question. Are you pointing out annihilation as an example of what you're looking for, or are you pointing to it as a something that you wouldn't count because it leaves some trace of the input matter in the form of radiation?
In the former case, it's happening all the time as a result of beta+ decay in stellar fusion. In the latter, you can't have anything like that due to the mass-energy conservation requirement.

edit: horrible, horrible grammar misteaks

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I mean there being absolutely no trace of it. Sort of like an antimatter collision

Bandersnatch
But, as I said, antimatter annihilation with matter does leave a trace - the energy of resultant radiation is exactly equal to the energy contained in the input particles.

And, again, antimatter (positrons) is produced in stellar fusion. Soon after it annihilates with a free electron.

Oh. Now I get what your saying. Does this mean that no substitute for the destroyed particle will be created?

Bandersnatch
Not in the sense of another massive particle. You could count the photons as substitutes for the destroyed particles, though. And indeed, most physicists would. They still carry some of the properties of the annihilated matter - energy and momentum.

Thank you. Honestly for once someone has given a definite answer to me. I now understand this.

sophiecentaur