Easther said he had met Hawking for lunch a couple of times and had met him at Cambridge University in the United Kingdom.
"In that sense he is a normal person, except he is not, he's Hawking."
Conversing with Hawking was an interesting experience, often Easther and other physicists would be talking shop and Hawking would chime in on something that had been said a minute or so ago, "ping-ponging" the conversation back.
Stephen Hawking died today at 76 years old. Photo / RTRoe, MediaPunch, IPX
"I knew him as a colleague. He was brilliant and was one of the top scientists in the 20th Century."
His primary contributions were understanding the connections between thermodynamics, black holes and quantum mechanics, Easther said.
University of Canterbury Canterbury Distinguished Professor Roy Kerr said Hawking was "an incredible strength of spirit and character".
Kerr first met the degenerative motor neuron disease sufferer when Hawking was 25.
"At that time he walked with difficulty and his diagnosis was poor and he was given only a few more years to live.
"Fifty years later he was still working with help and retained his quirky sense of humour."
Kerr and his wife had dinner with him at his home in May last year and came away marvelling at his sheer positivity.
"He was never a victim.
"His most notable contribution to science was the conjecture that black holes evaporate," Kerr said.
University of Otago department of physics professor David Hutchinson said he attended a workshop headed by Hawking in Santa Barbara in California back in 1999.
Canterbury Distinguished Professor Roy Kerr said Hawking was "an incredible strength of spirit and character". Photo / John Borren
Although he was attending a workshop for ultra-cold atomic physics, he went to see Hawking speak about cosmology anyway
Hawking had an "Interesting sense of humour", Hutchinson said.
"It takes a long time for him to respond, it was a single word answer like 'no' then there was a pause then he would say 'just kidding'. He was a humorous person."
He also had a connection to Hawking through his first honours student Dr James Fergusson who now works at University of Cambridge at the department of applied mathematics and theoretical physics where Hawking was a professor.
"He wasn't directly a student of Hawking but worked in the same group."
Hawking's legacy for motor neurone disease sufferers was noted by the Motor Neurone Disease Association of New Zealand.
"Stephen Hawking left a great legacy to people with motor neurone disease (MND), by showing the whole world that those with great disability may also be in possession of bright, active and nimble minds.
"Most people die within three years of their diagnosis. There are no clear reasons why Hawking lived so long with MND, though many neurologists tried to gain understanding," a spokeswoman said.
In May last year, Hawking warned that humans should leave earth within 100 years if we wanted to survive.
The renowned theoretical physicist believed that life on Earth was at an ever-increasing risk of being wiped out by a disaster, such as asteroid strikes, epidemics, over-population and climate change.
As our world became less suitable for life over the next century, Professor Hawking would warn in a new documentary that future generations must forge a new existence in space.
