What is the approximate mean distance between the Earth and the Sun expressed in kilometres?

Introduction / Context:
This question examines basic astronomical geography by asking for the approximate mean distance between the Earth and the Sun. This distance is fundamental in space science and is commonly referred to as one astronomical unit. Many other measurements in the solar system are expressed as multiples of this unit. For competitive exams, it is important to know at least the approximate value in kilometres, because it appears in questions on seasons, planetary orbits and solar radiation.

Given Data / Assumptions:

• The question is about the mean or average distance, not the minimum or maximum distance during orbit.
• Options are 149,502,000 km, 150,503,000 km, 148,000,000 km and 150,000,000 km.
• We assume the standard scientific value around 149.6 million kilometres.
• The aim is to choose the option closest to the generally accepted figure.

Concept / Approach:
The Earth follows an elliptical orbit around the Sun, so the distance between them is not constant. However, astronomy defines one astronomical unit as the mean distance, which is about 149.6 million kilometres. In competitive exams, approximate values are used, usually given as 149.6 million km, or about 150 million km. Among the options, 149,502,000 km is very close to 149.6 million km and is more accurate than round figures like 150,000,000 km. Therefore, we select the value that best represents one astronomical unit in standard references.

Step-by-Step Solution:
Step 1: Recall that one astronomical unit is about 149.6 million kilometres. Step 2: Compare this with the given options and identify which number lies closest to 149.6 million. Step 3: Option 149,502,000 km is approximately 149.5 million km, very close to 149.6 million km. Step 4: Option 150,000,000 km represents a slightly more rounded value, about 0.4 million km higher than the mean distance. Step 5: Conclude that 149,502,000 km is the most precise representation of the mean distance among the options.

Verification / Alternative check:
To verify, consider that many school textbooks mention 1 astronomical unit as approximately 149.6 million km or 150 million km. If the exam wants the closest scientific value, it will usually provide a number near 149.6 million. 149,502,000 km is within about 0.1 million km of this widely accepted figure, which is a very small relative error. In contrast, 150,000,000 km differs by about 0.4 million km. Options 148,000,000 km and 150,503,000 km are even further away. Hence, 149,502,000 km stands out as the best match to the average Sun Earth distance used in astronomy.

Why Other Options Are Wrong:
150,503,000 km is significantly larger than the accepted mean distance and does not match standard approximate values used in teaching material.
148,000,000 km is lower than the mean by more than one and a half million kilometres and is closer to one of the orbital extremes rather than the average.
150,000,000 km is a popular rounded approximation but is slightly less precise than 149,502,000 km, which better matches the defined astronomical unit.

Common Pitfalls:
Many students remember only the rounded number 150 million km and immediately choose that option without comparing more precise alternatives. Others may confuse the mean distance with perihelion (closest distance) or aphelion (farthest distance), which are slightly different. Some candidates simply look for the most rounded or neat looking number instead of recalling the scientific definition of an astronomical unit. To avoid such errors, remember both the rounded figure of about 150 million kilometres and the more accurate value around 149.6 million kilometres. Practice comparing options numerically so that the closest scientific value can be selected quickly.

Final Answer:
The approximate mean distance between the Earth and the Sun is 149,502,000 km, which closely represents one astronomical unit used in astronomy.