If the universe is ever expanding?

Question

wouldn't that make it like a perpetual motion machine?

well what i meant was, if it's ever expanding, how does it continue to expand unless there is something makeing it expand. and if it expands forever... then it has infinate energy.

oh i read about negative energy before i had no idea it was related to dark matter. er thats what it is? it seems to me that would be anti gravity? or it doesn't quite work like that?

Answer 1

The force that is driving the Universe's expansion is known as "vacuum energy" or sometimes "dark energy". Einstien's rehashing of gravity (viz. special and general relativity) imply that energy equates to a gravitational field.

Specifically, positive energy creates a perfectly normal gravitational field. So if the earth spun far faster than it does now (an increase in kinetic energy), it would aquire a greater gravitational field.

However, in some cases, "negative" energy can create a negative gravitational field. A rubber band stretched between the inner faces of a box, tugign inwards, would represent negative nergy and would actually decrease the weight of the box ever so slightly.

It turns out that space is suffused with a particular kind of negative nergy (the origin of which is a story unto itself) that acts as a negative gravitational field, driving everything apart.

Perpetual motion machines do not exist because nothing violates the laws of thermodynamics (so far as we know). The universe obeys these laws because the expansion of space actually constitutes an increase in entropy.

Answer 2

The definition of a machine is that it performs useful work through a conversion of energy. A perpetual motion machine would be a machine that conserves energy and continues to operate from the same exerted force gained from one injection of a measured amount of energy and any additional energy would then create useful work with no measuable loss of energy due to heat or other energy waste.

The expanding universe (if that actually is the case) does not meet the criteria of a machine based on the definition of a machine.

Answer 3

perpetual motion is where an event is set in motion and it continues forever unchanged...
by 'growing' the event is continually changing
so NO
plus its not a machine

Answer 4

Is there only one Universe??? I wonder...maybe this one will eggspand into the next one, and it could then be a Duoverse.Then there might be a third and so-on. Could it be endless?? could this all ready have happened? several times??
But What about atrophy?

Answer 5

scientists i think are still finding out whether the universe is gonna contract or expand

Answer 6

no. just objects in motion.
Not a machine.

Answer 7

YES

Answer 8

if it were man/alien/god-made...

Answer 9

no.