Would a flashlight turn on at lightspeed?

Moment Of Um

Brains On Universe

Kids & Family, Education For Kids

4.4 • 1.5K Ratings

🗓️ 15 March 2024

⏱️ 5 minutes

🔗️ Recording | iTunes | RSS

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Summary

What do a cheetah, a rocket ship, and champion sprinter Usain Bolt have in common? If you guessed they’re all way slower than your average beam of light, you’re correct! Nothing in our universe moves faster than light. But recently, we got an interesting puzzle from a listener: if you were able to travel at lightspeed, and you turned on a flashlight, would it turn on? We asked astrophysicist Amanda Farah to help us investigate.

Got a question that has you feeling in the dark? Send it to us at BrainsOn.org/contact, and we’ll help you see the light.

Transcript

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0:00.0	From the brains behind brains on, this is the moment of um.
0:03.7	Um, um, um,
0:08.0	moment of um comes to you from APM studios.
0:11.3	I'm Mark Sanchez.
0:13.0	We got a real puzzler of a question from one of our listeners, and I'm about to go find
0:20.4	out the answer. All I need is my handy-dandy flashlight and my nifty
0:25.7	thrifty jet pack. I built it myself from spare parts. I'm trying to reach
0:31.5	light speed which is about 186 miles per second.
0:38.0	Let's see what this baby can do.
0:42.0	Here I go!
0:45.0	Phew!
0:49.0	Nothing like the wind in your hair.
0:51.0	I must have been pretty close to light speed, right? Let's see.
0:55.4	12.6 miles per hour. Oh, man, my bike goes faster than that.
1:03.0	Looks like I'm going to need to do some more tinkering.
1:07.0	And in the meantime, I guess I'll call an expert to answer Leo's question.
1:11.0	If you're traveling at light speed and you turn on a flashlight,
1:15.0	would it turn on?
1:17.0	I love this question. I talk to a lot of people about it.
1:22.0	First of all, any human... I talked to a lot of people about it.
1:22.7	First of all, any human or anything with mass
1:26.7	can't reach the speed of light.
	...

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