Extra large gap in article where figure code is, even though figure is at top of page

Question

I writing an article using the amsart document class and whenever I use \begin{figure}...\end{figure} to put a figure into the article, it places the figure at the top of the page (which is fine), but leaves an extra space between the paragraphs.

To be more specific:

Paragraph zero text...
Paragraph one text...
begin{figure}...\end{figure}
Paragraph two text...
Paragraph three text...

Produces:

Figure
Paragraph zero text...
Paragraph one text...

Paragraph two text...
Paragraph three text...

When I intend to have the paragraphs follow the same spacing as the others:

Figure
Paragraph zero text...
Paragraph one text...
Paragraph two text...
Paragraph three text...

Is there a way to adjust the document setting so that that extra space does not appear?

Edit: Preamble and specific code:

\documentclass[reqno]{amsart}
\usepackage{amssymb,latexsym}
\usepackage{graphicx}
\usepackage{setspace}
\usepackage{cite}
\usepackage{fullpage}
\usepackage{subfig}
\captionsetup[subfigure]{margin=0pt, parskip=0pt, hangindent=0pt, indention=0pt, labelformat=parens, labelfont=rm}
\newtheorem{theorem}{Theorem}
\newtheorem{lemma}{Lemma}
\newtheorem{definition}{Definition}
\newtheorem{notation}{Notation}
\linespread{1.6}
\begin{document}
...vertices arranged in a circle, one of Dante's favorite Euclidean shapes. 

\begin{center}
\begin{figure}
\includegraphics[width=5.5in,height=5.5in]{graphn33} 
\caption{A complete graph with 33 people in heaven, $K_{33}$.}
\label{fig:graphn33} 
\end{figure}
\end{center}

This highly mathematical object displays...
\end{document}

If I don't have the spacing between the figure code and the paragraphs, the gap still remains but the paragraphs don't indent properly.

Answer 1

The problem is the center environment. It adds some vertical space, that is not floated to the top because it is outside the figure. You should replace it by \centering inside the figure (inside because you only want it to apply to the figure). \centering doesn't add any space.

\begin{figure}
    \centering
    \includegraphics[width=5.5in,height=5.5in]{graphn33} 
    \caption{A complete graph with 33 people in heaven, $K_{33}$.}
    \label{fig:graphn33} 
\end{figure}

Answer 2

You could try \raggedbottom in your preamble, for the case that it's caused by a \flushbottom or similar setting. During testing, I noticed vertical stretching even with amsart defaults, which have been canceled by \raggedbottom.