Weird Science

Weekend Herald - - Science & Tech - With Her­ald science writer Jamie Mor­ton @jamien­zher­ald

Easter Is­land’s famed stat­ues have long cap­ti­vated our imag­i­na­tions . . . and our prac­ti­cal minds.

How did the mono­lithic gi­ants get there? How were they built?

Now a new study has worked out how Poly­ne­sian ar­chi­tects were able to mount 13-tonne red hats on their heads.

The is­land in the South­ern Pa­cific Ocean is thought to have been first in­hab­ited in the 13th cen­tury by Poly­ne­sian trav­ellers.

Its stat­ues, carved from vol­canic tuff, came from one quarry, while the hats, made of red sco­ria, came from a quarry on the other side of the is­land.

Pre­vi­ous re­search has de­ter­mined that the stat­ues, which can be up to 10m tall and weigh 81 tonnes, were moved into place along well-pre­pared roads us­ing a walk­ing and rock­ing mo­tion, sim­i­lar to the way a fridge might be moved.

The hats, each weigh­ing 13 tonnes, might have been rolled across the is­land, but once they ar­rived at their in­tended stat­ues, they still needed to be lifted on to the stat­ues’ heads.

The is­landers prob­a­bly carved the hats cylin­dri­cally and rolled them to the stat­ues be­fore fur­ther carv­ing them to their fi­nal shapes, which vary from cylin­dri­cal to con­i­cal and usu­ally have a smaller cylin­dri­cal pro­jec­tion on the top.

“We were in­ter­ested in fig­ur­ing out the method of hat trans­port and place­ment of the hats that best agrees with the ar­chae­o­log­i­cal record,” Penn­syl­va­nia State Univer­sity’s Sean Hixon said.

The re­searchers took mul­ti­ple pho­to­graphs of many hats to see what at­tributes were the same through­out.

The only fea­tures they found the same were in­den­ta­tions at the bases of the hats, and these in­den­ta­tions fit the tops of the stat­ues’ heads.

If the hats had been slid into place on top of the stat­ues, then the soft stone ridges on the margin of the in­den­ta­tions would have been de­stroyed.

Pre­vi­ous re­searchers sug­gested that the stat­ues and the hats were united be­fore they were lifted into place, but the rem­nants of bro­ken or aban­doned stat­ues sug­gested this wasn’t the ap­proach used.

More likely, the hats were raised to the top of stand­ing stat­ues, us­ing large ramps. But, once the hat was at the top of the ramp, it could not sim­ply be pushed into place be­cause of the ridges on the margin of the hat base in­den­ta­tion.

Rather, the re­searchers be­lieve the hats were tipped up on to the stat­ues, where they could be ro­tated us­ing levers.

Easter Is­land and cli­mate change

An­other strange study, partly draw­ing on Easter Is­land, asks whether sus­tain­abil­ity is pos­si­ble.

As­tronomers have in­ven­to­ried a size­able share of the uni­verse’s stars, gal­ax­ies, comets, and black holes.

But does the uni­verse con­tain plan­ets with sus­tain­able civil­i­sa­tions?

Or does ev­ery civil­i­sa­tion that may have arisen in the cos­mos last only a few cen­turies be­fore it falls to the cli­mate change it trig­gers?

A group of re­searchers have tack­led the ques­tion from an as­tro­bi­o­log­i­cal per­spec­tive.

“Astro­bi­ol­ogy is the study of life and its pos­si­bil­i­ties in a plan­e­tary con­text,” said Pro­fes­sor Adam Frank, of the Univer­sity of Rochester.

“That in­cludes exo-civil­i­sa­tions or what we usu­ally call aliens.”

By think­ing of civil­i­sa­tions and plan­ets — even alien ones — as a whole, re­searchers can bet­ter pre­dict what might be re­quired for the hu­man project of civil­i­sa­tion to sur­vive.

“The point is to recog­nise that driv­ing cli­mate change may be some­thing generic,” Frank said.

“The laws of physics de­mand that any young pop­u­la­tion, build­ing an en­er­gy­in­ten­sive civil­i­sa­tion like ours, is go­ing to have feed­back on its planet.

“Seeing cli­mate change in this cos­mic con­text may give us bet­ter insight into what’s hap­pen­ing to us now and how to deal with it.”

Us­ing their model, the re­searchers found four po­ten­tial sce­nar­ios that might oc­cur in a civil­i­sa­tion-planet sys­tem.

They in­cluded mass “die-off ” sur­vived by only a frac­tion of the world’s pop­u­la­tion; a shift to a sus­tain­able fu­ture that avoided the most cat­a­strophic ef­fects; a pop­u­la­tion col­lapse that came with­out any change to the world’s re­sources; or a pop­u­la­tion col­lapse that came in spite of a late shift to sus­tain­abil­ity.

“The last sce­nario is the most fright­en­ing,” Frank said.

“Even if you did the right thing, if you waited too long, you could still have your pop­u­la­tion col­lapse.”

The re­searchers cre­ated their mod­els based in part on case stud­ies of ex­tinct civil­i­sa­tions, such as the in­hab­i­tants of Easter Is­land.

Peo­ple be­gan colonis­ing the is­land be­tween 400AD and 700AD and grew to a peak pop­u­la­tion of 10,000 some­time be­tween 1200AD and 1500AD.

By the 18th cen­tury, how­ever, the in­hab­i­tants had de­pleted their re­sources and the pop­u­la­tion dropped dras­ti­cally to about 2000 peo­ple.

The Easter Is­land pop­u­la­tion die-off re­lated to a con­cept called car­ry­ing ca­pac­ity, or the max­i­mum num­ber of species an en­vi­ron­ment can sup­port.

The Earth’s re­sponse to civil­i­sa­tion build­ing is what cli­mate change is re­ally all about, Frank said.

“If you go through re­ally strong cli­mate change, then your car­ry­ing ca­pac­ity may drop, be­cause, for ex­am­ple, large-scale agri­cul­ture might be strongly dis­rupted.”

He is­sued a sober warn­ing. “If you change the Earth’s cli­mate enough, you might not be able to change it back.”

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