RADAR Method
The word RADAR stands for Radio Detection and Ranging. A radar can be used to accurately measure the distance of nearby planets such as Mars. In this method, radio waves are transmitted from a source and, after reflecting off the planet, are detected by the receiver.
By measuring the time interval (\( t \)) between the transmission and reception of the radio waves, the distance to the planet can be determined using the formula:
Here, \( v \) is the speed of the radio waves. Since the time measured is for the radio waves traveling to the planet and back, it is divided by 2.
Example
Let's calculate the distance to Mars if the time interval (\( t \)) measured is 8.0 minutes (480 seconds). The speed of radio waves (\( v \)) is approximately \( 3 \times 10^8 \) m/s.
Distance (\( d \)) = \(\frac{3 \times 10^8 \, \text{m/s} \times 480 \, \text{s}}{2}\)
Distance (\( d \)) = \( 7.2 \times 10^{10} \, \text{m} \)
Thus, the distance to Mars is \( 7.2 \times 10^{10} \) meters.
Table of Range and Order of Lengths
| Size of Objects and Distances | Length (m) |
|---|---|
| Distance to the boundary of observable universe | 1026 |
| Distance to the Andromeda galaxy | 1022 |
| Size of our galaxy | 1021 |
| Distance from Earth to the nearest star (other than the Sun) | 1016 |
| Average radius of Pluto’s orbit | 1012 |
| Distance of the Sun from the Earth | 1011 |
| Distance of Moon from the Earth | 108 |
| Radius of the Earth | 107 |
| Height of Mount Everest above sea level | 104 |
| Length of a football field | 102 |
| Thickness of a paper | 10-4 |
| Diameter of a red blood cell | 10-5 |
| Wavelength of light | 10-7 |
| Length of a typical virus | 10-8 |
| Diameter of the hydrogen atom | 10-10 |
| Size of atomic nucleus | 10-14 |
| Diameter of a proton | 10-15 |
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