Cyclone Posted October 3, 2012 Share Posted October 3, 2012 Couldn't the expansion of the universe (and everything in it) be counted as perpetual motion? Firstly you'd have to prove that it isn't going to stop, that's not certain at the moment. But more importantly, the expansion of the universe isn't physical movement, it's a stretching of space/time, so I don't think that really counts. Link to comment Share on other sites More sharing options...
maxmaximus Posted October 3, 2012 Share Posted October 3, 2012 Couldn't the expansion of the universe (and everything in it) be counted as perpetual motion? If the universe is self sustaining with no beginning and no end then I think it could be described has a perpetual motion machine. But if it started from nothing and will one day end then no its not. Link to comment Share on other sites More sharing options...
howden Posted October 3, 2012 Share Posted October 3, 2012 Thanks for once again making the effort to keep the forum alive - otherwise we would all be talking about wheelie bins or the weather! Eureka, Put two of those on the wheelie bin. Forget fortnightly collections, perpetual bin emptying. Link to comment Share on other sites More sharing options...
PeteMorris Posted October 3, 2012 Author Share Posted October 3, 2012 Firstly you'd have to prove that it isn't going to stop, that's not certain at the moment. But more importantly, the expansion of the universe isn't physical movement, it's a stretching of space/time, so I don't think that really counts. :huh:..Hang on, I'm confused! The expansion of the universe isn't physical movement? So the earth doesn't physically rotate? The earth doesn't physically traverse the sun in orbit? All the other planets don't physically move? So we've kind of reached an impass, whereby nobody can actually prove whether the universe will expand infinitely, or reach some point whereby it stops and then contracts. Therefore, it cannot be disproved that it's not in perpetual motion! I'm off to hide again!................Whooooosh! Link to comment Share on other sites More sharing options...
Mr Bloke Posted October 3, 2012 Share Posted October 3, 2012 :huh:..Hang on, I'm confused! The expansion of the universe isn't physical movement? So the earth doesn't physically rotate? The earth doesn't physically traverse the sun in orbit? All the other planets don't physically move? So we've kind of reached an impass, whereby nobody can actually prove wherether the universe will expand infinitely, or reach some point whereby it stops and then contracts. Therefore, it cannot be disproved that it's not in perpetual motion! I'm off to hide again!................Whooooosh! I wonder if I could interest you in buying a new stick - one previous owner and carved by a local craftsman who specialises in recycling old wooden chair legs? It could come in handy if you intend to make stirring your new hobby... Link to comment Share on other sites More sharing options...
PeteMorris Posted October 3, 2012 Author Share Posted October 3, 2012 I wonder if I could interest you in buying a new stick - one previous owner and carved by a local craftsman who specialises in recycling old wooden chair legs? It could come in handy if you intend to make stirring your new hobby... Stirring?...Me?.....Perish the thought!...It's undumucashunnel! :hihi: Link to comment Share on other sites More sharing options...
Obelix Posted October 3, 2012 Share Posted October 3, 2012 Why? Why is it turning? That's a remnant of the angular momentum that the Solar System gained when it contracted from the original gas cloud that formed everything. The Earth is slowing down for two main reasons - tidal friction of the tides converts momentum to heat, and the Moon is moving outwards, somewhat slowly but it is definitivly moving. Link to comment Share on other sites More sharing options...
Cyclone Posted October 3, 2012 Share Posted October 3, 2012 :huh:..Hang on, I'm confused! The expansion of the universe isn't physical movement? So the earth doesn't physically rotate? The earth doesn't physically traverse the sun in orbit? All the other planets don't physically move? The things you describe are physical movement, but are not the expansion of the universe. So we've kind of reached an impass, whereby nobody can actually prove whether the universe will expand infinitely, or reach some point whereby it stops and then contracts. Therefore, it cannot be disproved that it's not in perpetual motion! I'm off to hide again!................Whooooosh! We simply don't have enough data yet, it will be proven (or accurately predicted at some point). But given that it isn't physical movement I don't think the heat death of the universe can be described as perpetual motion (particularly not if you use the accurate definition that Medusa mentioned). Link to comment Share on other sites More sharing options...
PeteMorris Posted October 3, 2012 Author Share Posted October 3, 2012 That's a remnant of the angular momentum that the Solar System gained when it contracted from the original gas cloud that formed everything. The Earth is slowing down for two main reasons - tidal friction of the tides converts momentum to heat, and the Moon is moving outwards, somewhat slowly but it is definitivly moving. I think the slowing and retrograde movement of the moon giving around 2 milliseconds per century of slowing of the earth, although technically not perpetual motion seems pretty negligeable to me! Link to comment Share on other sites More sharing options...
Obelix Posted October 3, 2012 Share Posted October 3, 2012 I think the slowing and retrograde movement of the moon giving around 2 milliseconds per century of slowing of the earth, although technically not perpetual motion seems pretty negligeable to me! It might be, but over time it does add up of course, proving that the Moon and tides are extracting energy from the Earth's angular momentum. If you go bakc and look at corals from the seas back in the Devonian you see that they have growth bands for each day of growth and a year band over the course of the seasons, and they have something like 400 days in a year. The length of the year hasn't changed but the length of the day certainly has. Link to comment Share on other sites More sharing options...
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