I’m sorry, I can’t resist a classic bad joke. But have you ever wondered why the past simple and past participle forms of the verb to read look identical to the present form, but sound different (“red”)?
To read is quite an oddity among verbs. With regular verbs, you just add (e)d to the end to change it to one of the past forms, and while there are many different irregular verbs, there are no others that chance pronunciation but not spelling. None that I can think of off the top of my head anyhow.
There are a few similar verbs that change their pronunciation, but also their spelling. For example: creep/crept/crept, sleep/slept/slept, meet/met/met, feed/fed/fed, lead/led/led. It’s a common enough pattern, but all change their spelling. The reason for the existence of this pattern is something known as the Great Vowel Shift. This was a long process between the 12 and 15th century in which the sounds of strong vowel forms in many English verbs gradually shifted over time. Many verbs that now have the /i:/ sound (e.g. feed) would have sounded something like fehd before the shift. However, the shift mainly affected present forms of verbs, so their past simple and past participle forms retained their pre-shift sounds: a shorter form of the original long vowel sound, e.g. fed. Now that I think of it, this is probably why some Irish people pronounce the past-simple form of to eat as “ett:” it’s probably a holdover from the original pronunciation before it morphed to ate and eaten.
So now we can see why the sound changes, but why not the spelling? Unlike any detailed synopsis of the Great Vowel Shift you might read, this answer is pretty straightforward. It simply seems that the a remained in the past forms of the verb to avoid confusion with the word red, as in the colour. And presumably, so that in some far-off future, someone would invent newspapers, and therefore allow us to finally take full advantage of the Great Vowel Shift to make really bad jokes (which, yes, I realise don’t actually work when you type them out as the title of a blog post instead of reciting them, but I just couldn’t stop myself using that title).