Learn Hardcore Russian: Я испытываю любопытство, когда читаю о новых открытиях. - I feel curiosity when I read about new discoveries.

In Russian you can express “to experience a feeling” by pairing испытывать (to experience) with a noun that names that feeling, e.g. испытывать страх, испытывать радость. Here испытываю любопытство literally means “I experience curiosity.” By contrast, я любопытен uses the adjective любопытный in the short-form masculine to mean “I am curious.” Both are correct, but:

испытывать + noun emphasizes the sensation or state as something you go through.
я любопытен simply describes a permanent or general trait (“I’m a curious person”).

What’s the difference between испытываю and чувствую in contexts like this?

Both verbs can introduce emotional or sensory experiences, but with slight nuance:

чувствовать (to feel) is more general and colloquial: я чувствую радость, я чувствую холод.
испытывать (to experience) sounds more formal or literary and often pairs with abstract nouns (страх, любопытство, приятные ощущения).

In everyday speech you might say мне любопытно or я любопытен, but испытываю любопытство is perfectly correct if you want a slightly elevated style.

Why is it о новых открытиях? What case is used and why does новых end with -ых and открытиях with -ях?

The preposition о (about) always takes the prepositional case. In plural that means:

Adjectives get -ых or -их (here новых).
Nouns get -ах or -ях (here открытиях).

So о новых открытиях literally means “about new discoveries.”

Why is the verb читаю in the present tense, and could you use a perfective instead?

Читаю is the present-tense form of the imperfective verb читать, which describes an ongoing or habitual action (“I read / I’m reading”). If you used a perfective like прочитать, you couldn’t form a present tense (there is no present прочитаю meaning “I am reading” – that means “I will read”). Perfectives focus on completed actions, so you would say когда я прочитаю о новых открытиях, я ... to mean “when I have read about new discoveries, I ...”

How does the conjunction когда work here, and can I put the time clause first?

Когда means “when” and introduces a subordinate clause of time (когда читаю о новых открытиях). You can place it either after the main clause or before it with no change in meaning:

Я испытываю любопытство, когда читаю о новых открытиях.
Когда я читаю о новых открытиях, я испытываю любопытство.

Both are correct; dropping я in the subordinate clause is also common if the subject is obvious.

Can I drop the pronoun я in я испытываю любопытство?

Yes. Russian is a pro-drop language: the verb ending -ю in испытываю already shows first-person singular. You could simply say Испытываю любопытство, когда читаю о новых открытиях. Including я adds a bit more emphasis or clarity, but isn’t grammatically required.