Big gap in aligned equations

Question

I am trying to write some aligned equations, but a get a big gap in the result. Here is my example:

   \usepackage{amsmath}
   \begin{document}
     \begin{align}
       \mathbf{x}(0)&=\mathbf{x}_0; && \mathbf{v}_x(0) &=\mathbf{v}_{x0}; && \dot{\mathbf{v}}_x(0)&=\omega_c\mathbf{v}_{y0}; \\
       \mathbf{y}(0)&=\mathbf{y}_0; && \mathbf{v}_y(0) &=\mathbf{v}_{y0}; && \dot{\mathbf{v}}_y(0)&=-\omega_c\mathbf{v}_{x0}; \\
       \mathbf{z}(0)&=\mathbf{z}_0; && \mathbf{v}_z(0) &=\mathbf{v}_{z0}; && \dot{\mathbf{v}}_z(0)&=0.
       \label{eq1}
    \end{align}        
\end{document}

And this is the output:

How can I get rid of the space in the second row?

Answer 1

In the align environment there are pairs of right and left aligned columns; automatically computed space separates those pairs of columns. To go from a column to the next one you use &.

Thus your code should be

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{align}
\mathbf{x}(0)&=\mathbf{x}0; & \mathbf{v}_x(0) &=\mathbf{v}{x0}; & \dot{\mathbf{v}}x(0)&=\omega_c\mathbf{v}{y0}; \
\mathbf{y}(0)&=\mathbf{y}0; & \mathbf{v}_y(0) &=\mathbf{v}{y0}; & \dot{\mathbf{v}}y(0)&=-\omega_c\mathbf{v}{x0}; \
\mathbf{z}(0)&=\mathbf{z}0; & \mathbf{v}_z(0) &=\mathbf{v}{z0}; & \dot{\mathbf{v}}_z(0)&=0.
\label{eq1}
\end{align}
\end{document}

However, you seem to want to label this with just one number, judging from the single label you set, so you probably want aligned nested in equation.

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{equation}\label{eq1}
\begin{aligned}
\mathbf{x}(0)&=\mathbf{x}0; & \mathbf{v}_x(0) &=\mathbf{v}{x0}; & \dot{\mathbf{v}}x(0)&=\omega_c\mathbf{v}{y0}; \
\mathbf{y}(0)&=\mathbf{y}0; & \mathbf{v}_y(0) &=\mathbf{v}{y0}; & \dot{\mathbf{v}}y(0)&=-\omega_c\mathbf{v}{x0}; \
\mathbf{z}(0)&=\mathbf{z}0; & \mathbf{v}_z(0) &=\mathbf{v}{z0}; & \dot{\mathbf{v}}_z(0)&=0.
\end{aligned}
\end{equation}
\end{document}