I would take a pic of a middle-ages person with my phone, show it to them and tell them I stole their soul. Then I'd be beaten, hanged, burned, and drowned for witchcraft. Still, it'd be hilarious.

We have sigils carved into refined rocks that can simulate the universe

I live in the here and now, and I’m still baffled by wireless internet. It’s modern sorcery

I read somewhere that we are going to set up solar panels in space convert the electcity to radio radios, beam it to earth, then convert it back to electricty.

To anyone that wasn't Nikola tesla, that just sounds insane.

Wireless telephone and internet would baffle even someone from the sixties.

l can think of one magic-technology that appeared during my lifetime:

E-Ink-Readers.

I mean, script suddenly appearing out of thin air on flat, solid surfaces? WTF?

I even studied enginering in the early 90's and would not have been able to come up with a technological explaination if I had encountered one of those back then...

The entire advanced mathematics. Go sufficiently far and mundane matrix multiplication will look like daemonic sigils. Write out a moderately complex math proof and you're essentially commanding inhuman tongue. Then when you convince them that it's really not devil summon spell you can tell the old era folks, that all these symbols is why the sun rises as fast as it does and moon has phases.

Smart phones. Not even Star Trek could predict we would all be walking around with a slab of glass that is exponentially more powerful than computers that took up entire rooms, can communicate with others sub-second via voice, images, video, or text, can access the sum total of public human knowledge at the blink of an eye, and can guide you to any location with a map for everywhere you want to go. It’s really powerful stuff and it’s in everyone’s hands.

The more time I've spent studying and researching new tech, the more I feel like, even to people today, our technology is magical.

I'm a medical diagnostic technologist. I understand how a CT and MRI machine work. They're still the stuff of magic imo. A lot of people take these technologies for granted because they're fairly prominent, but do you have any idea how a spinning magnet produces high quality, 3d images of the inside of your body? Very few people do. It's still freaking amazing and ingenious when you do understand it. Remodeling a CT scan into a 3d render is similarly impressive. The amount of calculations that take place within the space of seconds would take years for someone to do on paper, and we do 25-30 patients a day in our one machine at my location.

AI is making a big wave in my field too. Pretty soon we may only need radiologists to oversee AI rather than having to diagnose every exam themselves. AI on our consoles will be able to diagnose before we even send our images to a rad since they're so good at pattern recognition. Their readings have shown to be more accurate than a radiologist in some studies.

50 years ago we didn't even have consumer computers. Now our computers can diagnose and type a pneumothorax more accurately and faster than a doctor who has spent his whole life diagnosing xrays.

I’m 46 years old. In my lifetime, we’ve gone from being able to put half an hour on one side of an LP or cassette to being able to put a full album on a CD to being able to put a few hundred songs on an early MP3 player to being able to stream unlimited music almost anywhere in the world. That feels like magic to me.

Well we'd all be burned as witches, so hopefully you are bringing people forward in time, not tossing them backwards. I'd expect my time traveler to be stunned by nearly everything:

Flush toilet

Electrical anything

Telephone, speakers, TV

I took a networking course in college and loved it but you still can't convince me that radio isn't magic. Even knowing the mechanics of it doesn't help - it's so freaking crazy. Fiber optic data transmission is such an awesome technology but even that doesn't confuse me like radio, or broadcast tv.

Photography. Simple as that, would blow people's minds.

I mean we gather these black rocks called silicone and refine them, then we cut them to plates and inscribe them with microscopic runes using light and very secret mixtures. Next we use lighting on it to make it think for us.

An LED flashlight.

You have a device you can fit in your pocket that can shine a light so bright that it looks like day.

This sphere has an evil magical aura that really wants to tear your body apart. Now watch what happens when I remove the screwdriver!

I mean, any lcd screen. It's a magical flat surface that can display any image. Add a battery and now it's completely untethered and silent.

High speed rail, they would probably not believe their eyes if they saw a train going by with 300 kmh.

Quikclot. "Wait it's just clay powder?"

Smart phones. The caveat being you couldn't take one back in time and impress them because the internet and cellular network wouldn't be there.

I remember a great answer to this somewhere and they said a solar powered 4 function calculator is the simplest thing we have today that would blow people's minds. You really don't even need a scientific one to achieve the effect. Apart from the obvious (quick math, LCD display, and solar power) it also uses plastic.

Try explaining titanium bone implants or the process of getting metallic aluminum to a Sumerian coppersmith

Just about anything to do with a smart home. I can control lights and appliances in my home from anywhere in the world using my phone (magical) or just my voice.

Also appliances of most any type. A refrigerator magically contains winter all year 'round, a heater, oven and electric cooktop provide heat without the fire, and a microwave heats things without heat.

I can't believe 3D Printing hasn't been mentioned. Summoning figures from the ether would almost certainly get you tried as a witch.