Answer:
b. Hold up your hand in front of your face, and alternately close your left and right eyes.
Explanation:
The angle due to the change in position of a nearby object against the background stars is known as parallax.
This angle is gotten when the position of the object is measured from the Earth in January and then in July according to the configuration of the Earth with respect to the Sun in those months.
It is define in a analytic way as it follows:
[tex]\tan{p} = \frac{1AU}{d}[/tex]
Where d is the distance to the star.
[tex]p('') = \frac{1}{d}[/tex] (1)
Equation (1) can be rewritten in terms of d:
[tex]d(pc) = \frac{1}{p('')}[/tex] (2)
Equation (2) represents the distance in a unit known as parsec (pc).
The parallax angle can be used to find out the distance by means of triangulation. Making a triangle between the nearby star, the Sun and the Earth(as is shown in the image below), knowing that the distance between the Earth and the Sun (150000000 Km) is defined as 1 astronomical unit
That can be represented if you hold your thumb in front of your face and alternately close your left and right eyes, then, you will able to see how the thumb changes its position with respect to the background.
The angle between your eyes with respect to the thumb represents the parallax angle, and when you close one of your eyes that simulates the position of the Earth in January and then in July.
Key terms:
Parsec: Parallax of arc second
