Links to gi­ants like Sir Isaac New­ton, Alan Tur­ing pro­vide food for thought

Montreal Gazette - - WEEKENED LIFE + WEATHER - JOE SCHWARCZ The Right Chem­istry joe.schwarcz@mcgill.ca Joe Schwarcz is direc­tor of McGill Univer­sity’s Of­fice for Sci­ence & So­ci­ety (mcgill.ca/oss). He hosts The Dr. Joe Show on CJAD Ra­dio 800 AM every Sun­day from 3 to 4 p.m.

Sci­ence is all about com­ing to the right con­clu­sion based on an ob­ser­va­tion, of­ten a chal­leng­ing process. One might ob­serve that when­ever roost­ers crow, the sun comes up.

If some­one were un­e­d­u­cated, it might be tempt­ing to con­clude that the crow­ing is re­spon­si­ble for the ef­fect. But we know that roost­ers do not make the sun come up, and the con­clu­sion that they do would be wrong, even though it is based on an ac­cu­rate ob­ser­va­tion.

Per­haps the most fa­mous case of an ob­ser­va­tion lead­ing to a cor­rect con­clu­sion is that of New­ton for­mu­lat­ing the the­ory of grav­ity af­ter watch­ing an ap­ple fall. No ap­ple fell on New­ton’s head, but the fall­ing ap­ple story seems to be oth­er­wise cor­rect, if we are to be­lieve Wil­liam Stuke­ley, who was a con­tem­po­rary of New­ton and one of his first bi­og­ra­phers.

In a book writ­ten in 1752, he re­counts the ap­ple story as told to him by the great sci­en­tist him­self. As the weather was warm, the fu­ture Sir Isaac went into the gar­den to drink tea un­der the shade of some ap­ple trees. When he ob­served a fall­ing ap­ple, he be­gan to con­tem­plate the event.

Why should the ap­ple fall per­pen­dic­u­lar to the ground? Why not side­ways or up?

He be­gan to think. The ap­ple starts out a zero ve­loc­ity and speeds up as it trav­els to­ward the ground, so there must be a force act­ing on the ap­ple that causes this ac­cel­er­a­tion.

That force of at­trac­tion be­tween the ground and the ap­ple was what New­ton called grav­ity from the Latin word for “heavy.” What if the ap­ple tree were twice as high, New­ton mused. The ap­ple would still be at­tracted to the ground. And what if the ap­ple tree reached all the way to the moon? The fall­ing ap­ple would still be at­tracted to the Earth, he thought. And that would mean the moon should also be at­tracted to the Earth. But why wasn’t it crash­ing into the Earth?

Some 1,500 years be­fore New­ton, the Greco-Egyp­tian astronomer Claudius Ptolemy had de­ter­mined that the moon or­bited the Earth, but it re­mained for New­ton to pro­vide an ex­pla­na­tion. The moon in­deed was at­tracted by the Earth, but its for­ward ve­loc­ity was just enough to can­cel out the grav­i­ta­tional pull. An anal­ogy would be swing­ing a weight at the end of a rope around one’s head.

The weight is be­ing pulled by grav­ity, but the force of the swing can­cels out the grav­i­ta­tional at­trac­tion. New­ton even­tu­ally for­mu­lated his fa­mous law that every ob­ject in the uni­verse at­tracts every other ob­ject with a force that is pro­por­tional to the prod­uct of their masses and in­versely pro­por­tional to the square of the dis­tance be­tween them. This law was crit­i­cal in cal­cu­lat­ing the speed that had to be achieved to put a satel­lite into or­bit around the Earth.

Thanks to New­ton, the ap­ple has be­come a sym­bol for dis­cov­ery. If you ever visit Manch­ester in the United King­dom, don’t miss the bronze sculp­ture of Alan Tur­ing, the bril­liant math­e­mati­cian who is said to have short­ened the Sec­ond World War with his de­sign of a com­puter that was able to de­ci­pher coded mes­sages the Al­lies had in­ter­cepted.

The bronze re­pro­duc­tion of Tur­ing sits on a bench in­scribed with an en­crypted text as it would have ap­peared had it been gen­er­ated by the “Enigma ma­chine,” a de­vice the Ger­mans be­lieved trans­lated text into code that could not be bro­ken. When de­coded by Tur­ing’s com­puter, the script on the statue reads, “Fa­ther of Com­puter Sci­ence.”

Of course, the truth is that com­puter sci­ence has many fa­thers. But Tur­ing did in­deed play a piv­otal role in its de­vel­op­ment, as well as in­tro­duc­ing the no­tion of ar­ti­fi­cial in­tel­li­gence.

Why is Tur­ing’s statute hold­ing an ap­ple? The most likely ex­pla­na­tion is that it is a tribute to New­ton, whose con­tri­bu­tions to math­e­mat­ics and physics make him one of the most in­flu­en­tial sci­en­tists of all time.

There are some, how­ever, who pro­pose an­other sce­nario. Tur­ing was pros­e­cuted for en­gag­ing in a ho­mo­sex­ual re­la­tion­ship and ac­cepted chem­i­cal cas­tra­tion with di­ethyl­stilbe­strol as an al­ter­na­tive to prison.

In 1954, he was found dead, with a half-eaten ap­ple by his side, a vic­tim of cyanide poi­son­ing.

The sug­ges­tion is that he had doped the ap­ple with cyanide and com­mit­ted sui­cide.

Tur­ing, though, also ex­per­i­mented with elec­tro­plat­ing cut­lery, a process that uses cyanide. It is there­fore pos­si­ble he poi­soned him­self by ac­ci­den­tal in­hala­tion.

The ap­ple was never tested for cyanide, but per­haps the sculp­tor used it to com­mem­o­rate the dread­ful per­se­cu­tion of ho­mo­sex­u­als at the time.

There’s one more ob­ser­va­tion lead­ing to a con­clu­sion to deal with. The Ap­ple Com­pany’s logo is an ap­ple with a miss­ing bite.

It has been sug­gested that this is a tribute to Tur­ing. How­ever, when Steve Jobs was asked if this were true, his an­swer was a cryp­tic “we wish it were.”


Wil­liam Stuke­ley re­counted the story of Sir Isaac New­ton’s ob­serv­ing of an ap­ple fall­ing, and New­ton’s sub­se­quent won­der about why it would fall per­pen­dic­u­lar to the ground; why not side­ways or up?


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