"...even the most respected history of an event is at best an approximation."~James Cameron, writing in the preface to The Titanic Disaster Hearings
"The whole incident can’t be verified, yet can’t be dismissed."~Walter Lord, referring to the alleged suicide of William Murdoch.
Perhaps nothing is more controversial regarding Titanic (even today) than exactly why she steamed headlong into disaster. And not just into an iceberg but into an enormous ice field--that fact was clearly established in both the US and British inquiries and by reconstruction of extant the facts from other ships in the vicinity of the disaster. Here's a good visual of what Titanic came upon that night:
In the initial days following the disaster, a Titanic crew member alleged that the bridge had ignored 15 minutes of warnings from the crow's nest. From the book, The Sinking Of The Titanic And Great Sea Disasters, published in 1912 (I've footnoted subsequent historical challenges):
SUNDAY night the magnificent ocean liner was plunging through a comparatively placid sea, on the surface of which there was much mushy ice and here and there a number of comparatively harmless-looking floes. The night was clear and stars visible. First Officer William T. Murdock was in charge of the bridge. The first intimation of the presence of the iceberg that he received was from the lookout in the crow's nest.
Three warnings were transmitted from the crow's nest of the Titanic to the officer on the doomed steamship's bridge 15 minutes before she struck, according to Thomas Whiteley, a first saloon steward (waiter).
Whiteley, who was whipped overboard from the ship by a rope while helping to lower a life-boat, finally reported on the Carpathia aboard one of the boats that contained, he said, both the crow's nest lookouts.  He heard a conversation between them, he asserted, in which they discussed the warnings given to the Titanic's bridge of the presence of the iceberg.
Whiteley did not know the names of either of the lookout men and believed that they returned to England with the majority of the surviving members of the crew.
'I heard one of them say that at 11.15 o'clock, 15 minutes before the Titanic struck, he had reported to First Officer Murdock, on the bridge, that he fancied he saw an iceberg!' said Whiteley. "Twice after that, the lookout said, he warned Murdock that a berg was ahead. They were very indignant that no attention was paid to their warnings.' Murdock's tardy answering of a telephone call from the crow's nest is assigned by Whiteley as the cause of the disaster.
When Murdock answered the call he received the information that the iceberg was due ahead. This information was imparted just a few seconds before the crash, and had the officer promptly answered the ring of the bell it is probable that the accident could have been avoided, or at least, been reduced by the lowered speed.
The lookout saw a towering "blue berg" looming up in the sea path of the Titanic, and called the bridge on the ship's telephone. When, after the passing of those two or three fateful minutes an officer on the bridge lifted the telephone receiver from its hook to answer the lookout, it was too late.
The speeding liner, cleaving a calm sea under a star-studded sky, had reached the floating mountain of ice, which the theoretically "unsinkable" ship struck a crashing, if glancing, blow with her starboard bow.
Had Murdock, according to the account of the tragedy given by two of the Titanic's seamen, known how imperative was that call from the lookout man, the men at the wheel of the liner might have swerved the great ship sufficiently to avoid the berg altogether. At the worst the vessel would probably have struck the mass of ice with her stern.
Murdock, if the tale of the Titanic sailor be true, expiated his negligence by shooting himself within sight of all alleged victims huddled in life-boats or struggling in the icy seas.
When at last the danger was realized, the great ship was so close upon the berg that it was practically impossible to avoid collision with it.
The first officer did what other startled and alert commanders would have done under similar circumstances, that is he made an effort by going full speed ahead on the starboard propeller and reversing his port propeller, simultaneously throwing his helm over, to make a rapid turn and clear the berg. The manoeuvre was not successful. He succeeded in saving his bows from crashing into the ice-cliff, but nearly the entire length of the under body of the great ship on the starboard side was ripped. The speed of the Titanic, estimated to be at least twenty-one knots, was so terrific that the knife-like edge of the iceberg's spur protruding under the sea cut through her like a can-opener.
The Titanic was in 41.46 north latitude and 50.14 west longitude when she was struck, very near the spot on the wide Atlantic where the Carmania encountered a field of ice, studded with great bergs, on her voyage to New York which ended on April 14th. It was really an ice pack, due to an unusually severe winter in the north Atlantic. No less than twenty-five bergs, some of great height, were counted.
|Icefield in the vicinity of the Titanic sinking April 15, 1912. original|
 Murdoch did not survive. Several books and movies portray him committing suicide, including James Cameron's 1997 Titanic. Walter Lord, the first Titanic historian, had discounted Murdoch's suicide in his 1955 book A Night To Remember but reversed his opinion when letters written by survivors to family members surfaced. Lord was a technical consultant to Cameron's 1997 film and passed away in 2002. Interestingly, when Murdoch's living descendants complained of Murdoch's portrayal in Titanic and threatened to sue, Cameron responded by endowing a scholarship in Murdoch's Scottish hometown. The facts of the alleged Murdoch suicide are explored in most detail here. <-- a website devoted to Murdoch.
 The lookout on duty, Fredrick Fleet, survived in lifeboat No. 6. He was subpoenaed at both the US and British inquiries. He denied Whiteley's claims. The other lookout, Reg Lee, was saved in lifeboat No. 13. and subpoenaed at the British hearings. He also denied the claims.
 This has been factually contested. Whiteley was not picked up in life boats No. 6 nor No. 13 which contained the two lookouts. Instead he appears to have been saved by climbing aboard overturned collapsible boat B. Whiteley is an interesting character and appears to have gone on to have some interesting Rose Dawson-like adventures: flying ace, & stage and film actor. He has no Wikipedia page entry but is covered by Encyclopedia Titanica here. Whiteley actually sued the White Star Line in 1914 for "steering error" and negligence, but the suit never went to trial.