$block['content'] should be an array, like in the example for hook_block_view:

$block['content'] = array(
    '#theme' =&gt; 'feed_icon',
    '#url' =&gt; 'rss.xml',
    '#title' =&gt; t('Syndicate'),
  );


For more examples, see Examples for Developers project, block_example module.

If you are putting array there, it must be a renderable array. If it's not, then either:


Implode it into string. With nested arrays, it can get a bit complicated.
Put it as an element in $block['content'] array, and set $block['content']['#theme'] element to something that can theme it. More complicated, but also more versatile and cleaner solution.


How to display JSON returned (from external REST API) in a Block? [my code attempt inside]
What maintains quark spin alignments in baryons?

The $uud$ proton and $udd$ neutron are both spin 1/2, implying that two of their spin 1/2 quarks are always parallel and the other is always opposed.

In contrast, the $\Delta^+$ particle (which like the proton is $uud$) and the $\Delta^0$ particle (which like the neutron is $udd$) are both spin 3/2, implying presumably that the same principle keeps their internal quark spins all parallel.

What principle keeps trios of quarks aligned or anti-aligned in such specific ways?
