Скачать или смотреть What Is The Distance To Mars?

When we see all these beautiful images of Mars coming back from the Curiosity Rover, it's easy to forget... that's another planet!

And that planet is really really far away.

So, how far away is Mars?

The answer to that question changes from moment to moment because Earth and Mars are orbiting the Sun.

At times they're on the same side of the Sun - their closest point, also known as opposition. From our perspective, Mars and the Sun are on opposite sides of the Earth. They are in opposition in our sky.

And other times, Mars is on the other side of the Sun, at its most distant point - known as conjunction. We see Mars and the Sun in roughly the same spot in the sky.

But it gets even more complex than that.

Both Earth and Mars follow elliptical orbits around the Sun. When their orbits match up, we can get very close oppositions, or very distant conjunctions.

In the next opposition of Mars, on April 8, 2014, Mars will get as close as 93 million kilometers.

But back in 2003, Mars got as close as 56 million kilometers, the closest it had been in thousands of years.

We'll get another close approach in 2018.

And so the conjunctions can vary too.

The most recent conjunction, in April 2013, Mars was 364 million km away from Earth, on the other side of the Sun.

And in June, 2015 it'll be 384 million kilometers.

The vast distance between Earth and Mars has a real impact on our communications to the Red Planet.

NASA engineers controlling the Curiosity Rover and other spacecraft have to consider the time it takes for signals to reach Mars and then return.

When Mars is at its closest point, it only takes about 4 minutes for light to travel to Mars, and then another 4 minutes to get back.

So, if an engineer wants to take a picture of a rock on Mars, it'll take about 8 minutes to see the results of that command.

But when Mars is at its most distant point, that round trip takes much longer.

A signal from Earth takes 20 minutes to reach Mars, and then 20 minutes back.

The first person to ever calculate the distance to Mars was the astronomer Giovanni Cassini, famous for his observations of Saturn.

Giovanni made observations of Mars in 1672 from Paris, while his colleague, Jean Richer made the same observation from Cayenne, French Guiana.

They used the parallax method to calculate the distance to Mars with surprising accuracy.

However, astronomers now calculate the distance to objects in the Solar System using the speed of light.

They measure the time it takes for signals to reach spacecraft orbiting other planets.

They can bounce powerful radar off planets and measure the time it takes for signals to return.

This allows them to measure the distance to planets, like Mars, with incredible accuracy.

The distance to Mars is far... Really really far.

And yet, Mars, and the rest of the planets are right next to us when you consider the vast distances of the cosmos.