The following science joke involving photons has been very popular:
 
“A photon checks into a hotel. A bell hop asks him if he needs any help with his luggage. The photon says, ‘No, thanks. I’m traveling light.’”
 
The joke has been cited in print since at least 2009.
 
   
Wikipedia: Photon
A photon is an elementary particle, the quantum of light and all other forms of electromagnetic radiation, and the force carrier for the electromagnetic force, even when static via virtual photons. The effects of this force are easily observable at both the microscopic and macroscopic level, because the photon has zero rest mass; this allows long distance interactions. Like all elementary particles, photons are currently best explained by quantum mechanics and exhibit wave–particle duality, exhibiting properties of both waves and particles. For example, a single photon may be refracted by a lens or exhibit wave interference with itself, but also act as a particle giving a definite result when its position is measured.
     
Compu-Diva.com
Bad Science Joke Day 
Posted by bc
November 23rd, 2009
A photon checks into a hotel. The bell hop asks him ” Can I help you with your luggage?” To which the photon replies, “I don’t have any. I’m traveling light.”
 
Black Maps
A Virus Walks Into A Bar… and other Science jokes 😛
This entry was posted on December 7, 2009 at 1:34 PM
(...)
A photon checks into a hotel. The bell hop asks him ” Can I help you with your luggage?” To which the photon replies, “I don’t have any. I’m traveling light.”
 
Tanya Khovanova’s Math Blog
Physics Jokes
24th December 2009, 04:21 pm
I could no longer resist: I added a section of physics jokes to my math jokes collection:
(...)
A photon checks into a hotel. The bellhop asks him, “Can I help you with your luggage?”
To which the photon replies, “I don’t have any. I’m traveling light.”
     
JoyReactor
16:00:00; 30 Mar 2010
anon
demotivation posters auto
A PHOTON CHECKS INTO A HOTEL AND IS ASKED IF HE NEEDS ANY HELP WITH HIS LUGGAGE.
“NO THANKS, I’M TRAVELLING LIGHT.”
 
Twitter
Best Roof Talk Ever
‏@BestRTE
A Photon Checks Into a Hotel… - The bell hop asks him ” Can I help you with your luggage?” To which the… http://tumblr.com/xzgigfaou
12:00 PM - 13 Sep 2010
 
Fun Corner
17th Sep 2011
A PHOTON CHECKS INTO A HOTEL AND IS ASKED IF HE NEEDS ANY HELP WITH HIS LUGGAGE.
“NO THANKS, I’M TRAVELLING LIGHT.”
 
Google Books
The Mammoth Book of One-Liners
By Geoff Tibballs
London: Constable & Robinson Ltd.
2012
Pg. ?:
A photon checks into a hotel and is asked if he needs any help with his luggage. “No, thanks,” he says, “I’m travelling light.”
 
Google Books
More One Liners, Jokes and Gags
By Grant Tucker
London: The Robson Press
2013
Pg. ?:
A photon checks into a hotel and the porter asks him if he has any luggage. The photon replies, “No, I’m travelling light.”
 
Twitter
Oisin O’Callaghan
‏@oisinoc89
@LuigiMalonesDub A photon walks into a hotel and is asked does he need any help with his bags.
“No thanks, I’m travelling light.” #luigilol
11:56 AM - 26 Jul 2014
 
Twitter
Thomas Dehart
‏@ThomasDehart
A photon checks into a hotel.
The clerk asks if he needs any help with his luggage.
He replies. No, I am traveling light. #Science
1:32 PM - 26 Jul 2014