I was reading a book by Stephen Hawking, it was written that universe is made up of 2 ingredients,i.e., space and energy and space was the negative energy, so they add up to 0. But since space is energy does that mean it is finite?
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1$\begingroup$ Just don't take that simple "equation" too literal $\endgroup$– Hagen von EitzenCommented Jun 14, 2019 at 18:09
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$\begingroup$ I thought so, but still how can i know how it works? Thanks $\endgroup$– raptorAcrylycCommented Jun 14, 2019 at 18:10
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2$\begingroup$ Is the universe finite? We can have models about whether its shape (closed, flat or open) suggests it's finite or infinite, but there's no way we can ever be sure, since we can only see a portion of it. NB Hawking was great at writing books in simple language to explain the complex physics (i.e. mathematics) of things like black holes, but his examples break down if you examine them too closely. :-) $\endgroup$– Chappo Hasn't ForgottenCommented Jun 16, 2019 at 1:23
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$\begingroup$ Never understood a single book of SH. I must say my copies were translated, I think is important when it comes to already stretched analogies and examples. $\endgroup$– AlchimistaCommented Jun 17, 2019 at 12:47
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2 Answers
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As everyone is saying, this is a very loose "plain English" version of some complex ideas, but if space was infinite, you could view this suggestion (that the overall total energy of the universe is zero) as applying to any sufficiently large region of space. So if you pick any 10 billion lightyear diameter sphere you would expect to find the energy of the matter in that sphere more or less cancelled out by the gravitational potential energy arising from the separation of that matter.
answered Jun 18, 2019 at 13:32
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In his book "Brief Answers to the Big Questions" completed by his colleagues after his death, Stephen Hawking does sort of mention that the negative energy created (along with equal amount of positive) at the time of Big Bang is in space now or is space as both matter-energy and space were created after the Bang. The universe is the ultimate free lunch. As galaxies are moving faster the farther they are, more space is being generated at the same time absorbing the increased magnitude of negative (gravitational potential) energy. The total sum remaining always zero. It is has no implication about whether the space is finite or not. What it does imply is linkage between motion (all mass-energy is the energy of motion of quarks, gluons, or change in motion due to Higgs field) and gravity, given by Newton's two laws: the law of motion and gravitation.
