People commonly make appeals to authority in arguments. But how do you know how much authority there is on each side of an issue?
You'll have to think about it. Make conjectures, use criticism, and so on.
If you're going to do that, why not just do it about the issue directly? If it's hard because you don't know about the issue, you aren't going to be much good at judging who the proper authorities are either. You'll just have to go on what people tell you. In other words, find an authority on authority, like a university that grants certificates of authority (degrees).
An authority on authority does not solve the dilemma. How do you know he/it truly has the authority to make the pronouncements he/it does? Better ask an authority on authorities on authority. So you have a turtles all the way down dilemma (infinite regress).
So this appeal to authority approach fails.
But there's more. Isn't this a lot of trouble to avoid thinking and learning about stuff yourself?
It fails in that way, too! Trying to make it work, and defend it, and make judgments about who has authority, is itself a way of approaching issues that takes a lot of thought. So you haven't saved any thinking or effort.
You could always not think and hope that works. But then appeals to authority still make no sense. If you pick who to call an authority thoughtlessly or pick which side has more authority thoughtlessly, you are no better off than if you just directly pick a side of the issue thoughtlessly.
We agree on appeal to one authority, Guru or scientist.
But what about appeals to science itself, meaning the interauthority of many scientists.