i was told ther is no cadinal point in space..?

Question

so how does one know which direction to head...if you head to pluto..what is the direction..if you head to mercury..what is the direction?

Answer 1

Gerry H has it about right. Instead of up/down, left/right, there is a standard XYZ system, called the International Celestial Reference System (ICRS). Using several 100 extragalactic radio sources (mostly quasars), we can define the X, Y, and Z directions. The center origin is the center of the solar system (the barycenter).

Answer 2

True, there is no up or down or North or South in space, or any other absolute direction in space. But for navigation, we can use very distant relatively "fixed" markers, like stars, as reference points, and plot directions relative to them.

For example, suppose you are going to send a probe to Pluto. At the speed that the probe will travel, you know that it will take 9 years to get there. Knowing Pluto's current position, speed, and direction, you calculate that, in 9 years, Pluto will lie in the direction of say "midway between Betelguese and Sirius". So you program the guidance of the probe to meet it there.

Answer 3

To navigate in space, one selects a frame of reference suitable to the task. For scientific purposes, there is a defined reference system ( http://www.iers.org/MainDisp.csl?pid=96-107 ), but actual space mission navigation calculations will be done in whatever reference frame makes the math easiest. For interplanetary probes, that would be a sun-centered system, while shuttle missions and Earth satellites use an Earth-centered system. For practical purposes it works out best if you choose a reference frame centered on the center of gravity of the system you're navigating through. The orientation of the axes can also be arbitrarily chosen, but again, practicality suggests you should align one axis with a significant rotational axis of the system. This gives you your center point and your z axis.

The fact that there is no cardinal point just means that all these frames of reference are equally arbitrary.

Answer 4

Mercury is close to the sun, so go toward the light.
Pluto could be anywhere in the planetary plane, I recommend you check before ordering tickets from Virgin. In general head away from earth (your first point of reference) and find out where your target is going to be at the speed you are traveling. Most planets are somewhere around the equator of the earth and of the sun. None are toward the north pole or the south pole.