Noodle Posted August 13, 2002 Report Posted August 13, 2002 Does the universe require energy to expand? Which law states that energy cannot be created or destroyed?
Noah Posted August 13, 2002 Report Posted August 13, 2002 Yes, the universe does require energy to expand, and it got that energy from the big bang. However, if some theories are true, that the universe is accelerating, then where THAT energy is coming from, I have no idea. And here are the laws of conservation of mass and energy. The law of conservation of matter states: Matter is always conserved, which means: The total amount of matter in the universe remains constant. Matter is neither created not destroyed. It is only changed in form. The law of conservation of energy states: Energy is always conserved, which means: The total amount of energy in the universe remains constant. Energy is neither created not destroyed. It is only changed in form. However, when Einstein came along, he discovered that matter could be changed into energy, and the other way around. So the law of conservation of mass-energy was developed. It states that mass and energy are always conserved and that their SUM cannot increase or decrease. Noah
michaelchang Posted August 13, 2002 Report Posted August 13, 2002 IF the universe is accelerating, the energy comes from what they call dark energy (or is it dark matter?!). It's something like mass, but it does the opposite. Instead of pulling objects together, it pushes them apart. As for the law of conservation of energy, I believe the original version is the first law of themodynamics: Increase in internal energy = Energy gained by heating + Energy gained by working. If you supply energy to a system by working and heating, the internal energy increases by the total of amount of energy supplied. Another way saying it, in addition to what Noah mentioned, is "Total energy of an isolated system remains constant".
Tormod Posted August 13, 2002 Report Posted August 13, 2002 Just to chip in, here's a link for you: http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/990210a.html Tormod
Noodle Posted August 15, 2002 Author Report Posted August 15, 2002 To summarize your responses: All of the energy that ever existed/exists is expanding the universe at an ever increasing rate until entropy (which is not only keeping up, but gaining) eventually snuffs out relative energy resulting in the "heat death of the universe". There is no energy required for this expansion: it has already been supplied to this closed system called "the universe". If the universe doesn't die a "heat death" it may coalease back into a grandmother black hole and re-bang ad infinitum. In the beginning, then, there was only energy and mass (a variation of energy) developed a few milliseconds later? Entropy is a condition of energy? The universe is a closed system of various energy states which lasts forever? Is this [universe] a perpetual motion machine?
Tormod Posted August 15, 2002 Report Posted August 15, 2002 There are so many theories on how the universe came into being, how it grows, (and even whether it in fact does expand or not), whether there have been different growth periods in the past...I don't think it fair so summarize our feedback so soon. I suggest you read the book "Five Ages of the Universe" which is an excellent book with refreshing theories about the past and the future of the universe. We have a review of it at http://www.hypography.com/Article.cfm/29590.html You should also look around the other reviews - energy, entropy and expansion is truly among the central issues in cosmology. Stephen Hawking's book "The Universe in a Nutshell" is also a good read on this.
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