How long does it take for a radio signal to go from Earth to Mars?

Asked by: Richard Boulais


Radio signals are electromagnetic waves, such as light or X-ray. The speed of electromagnetic waves in vacuum, is 300000km/sec (approximately).

In order to calculate the time of travel with this speed from Earth to Mars, we need to know the distance.

When the Mars and the Earth are at the opposite sides of the Sun, the distance is the largest: approximately: 378 million km. The time needed for an electromagnetic wave to cover this distance is approximately: 21 minute.

The closest distance between Mars and Earth is 78 million km, the time in this case is: 4.3 min.

So the time of travel between Earth and Mars is between 4.3 minutes and 21 minutes, depending on the actual distance between the two planets.

Answered by: Ferenc Szekely, Ph.D., Physicist, ELTE, Budapest, Hungary



Science Quote

'As far as the laws of mathematics refer to reality, they are not certain; and as far as they are certain, they do not refer to reality.'

Albert Einstein

Top Selling

Here are our physics & astronomy bestsellers:
Magnetic Levitator - Classic
KonusScience 5 Way Microscope Kit
CHEM C2000 Chemistry SuperKit v2.0
Snap Circuits Jr.
Space Wonder Gyroscope
Solar Radiometer
Mini Plasma Ball
Smart Robot 4M Kit
130 Electronics Projects Kit


USC University of Southern California Dornsife College Physics and Astronomy Department McMaster University Physics and Astronomy Department