I've been trying to make a wordpress theme from scratch, but when I open the index.php page in localhost I get an http 500 error.

Apache is installed and configured correctly (Another site I have displays just fine).

the only difference is that the index.php of the old site begins with an HTML declaration.

header.php contains the proper declarations shouldn't this be enough?

navigating to localhost/new_site/index.php gives 500 error:
Code:
<?php get_header(); ?>
    
<div id="main">
  <div id="content">
    <h1>Main Area</h1>
    <?php if (have_posts()) : while (have_posts()) : the_post(); ?>
    <h1><?php the_title(); ?></h1>
    <h4>Posted on <?php the_time('F jS, Y') ?></h4>
    <p><?php the_content(__('(more...)')); ?></p>
    <hr>
    <?php endwhile; else: ?>
    <p><?php _e('Sorry, no posts matched your criteria.'); ?></p>
    <?php endif; ?>
  </div>

  <?php get_sidebar(); ?>

  </div>

<div id="delimiter"></div>

<?php get_footer(); ?>
I've been trying to start this new site but am frustrated that right at stage 1 I can't even view the page correctly on my computer... any suggestions?