Let's start a discussion about the Halley's Comet. Do you know that it appears on Earth in the year of 1991 and It was already been predicted that it will appear again on 2061. Halley Comet was named after the astronomer Edmund Halley who was born in London, England.

The only comet that can be predicted.

Let you read some background history of the comet. 

Halley's Comet or Comet Halley (officially designated 1P/Halley) is the most famous of the periodic comets, and is visible from Earth every 75 to 76 years. Many comets with long orbital periods may appear brighter and more spectacular, but Halley is the only short-period comet that is clearly visible to the naked eye, and thus, the only naked-eye comet that might appear twice in a human lifetime. During its returns to the inner solar system, it has been observed by astronomers since at least 240 BC, but it was only recognized as a periodic comet in the 18th century when its orbit was computed by English astronomer Edmond Halley, after whom it is named. Halley's Comet last appeared in the inner Solar System in 1986 and will next appear in mid-2061.

During its 1986 apparition, Halley's Comet became the first to be observed in detail by spacecraft, providing the first observational data on the construction of the comet nucleus and the mechanism of tail formation. These observations supported a number of longstanding hypotheses about comet construction, particularly Fred Whipple's "dirty snowball" model, but also provided data which substantially reformed and reconfigured these ideas.

Discovered by prehistoric (observation);
Edmond Halley (recognition of periodicity) 
Orbital characteristics (Epoch 2449400.5)
(February 17, 1994) 
Aphelion 35.1 AU
(December 9, 2023)
Perihelion 0.586 AU
last perihelion: February 9, 1986
next perihelion: July 28, 2061 
Semi-major axis 17.8 AU 
Eccentricity 0.967 
Orbital period 75.3 a 
Inclination 162.3° 
Physical characteristics 
Dimensions 15×8 km[3], 11 km (mean) 
Mass 2.2 × 1014 kg 
Mean density 0.6 (estimates range from 0.2 to 1.5 g/cm³) 
Sidereal rotation
period 2.2 d (52.8 h) (?) 
Albedo 0.04
Apparent magnitude 28.6

Let's start the discussion with: How old are you when Halley's Comet will appear on Earth on 2061?

Looking forward for your answers my friends!!!