Today Wonderopolis is talking about mercury. Or is it Mercury? If you know much about mercury (or Mercury!), you know that a little clarification is in order!

In ancient Roman mythology, Mercury was one of the gods. Specifically, Mercury was the Roman version of the Greek god Hermes. As the messenger of the gods, Mercury was often portrayed as a sleek figure with winged sandals.

Of course, Mercury isn’t just a “who.” It’s also a place. Named after the ancient Roman god, Mercury is the name of the planet closest to the Sun. It’s also the smallest planet. It orbits the Sun once every 88 days.

Mercury looks a lot like Earth’s Moon. It has next to no atmosphere, which means it has radical swings between hot and cold temperatures every day. A single day on Mercury can see temperatures as low as -300° F and as high as 800° F!

Since Mercury is smaller than Earth, it has less gravity. If you weigh 70 pounds on Earth, you’d weigh only about 27 pounds on Mercury! Mercury is composed of mostly heavy metals, such as iron. That’s only appropriate, since the planet gave rise to the name of one of the chemical elements found on Earth: mercury.

Mercury — the chemical element — is a metal with the symbol Hg. Hg stands for Hydrargyrum, which means liquid silver. The element mercury is sometimes also called quicksilver.

Mercury is one of the few elements — and the only metal — that is a liquid at regular room temperature and pressure. It can become a solid if it freezes at about -38° F. It can also become a gas if it boils at a temperature of about 674° F.

A heavy, silvery metal, mercury and its compounds are highly poisonous. Pure mercury is rarely found. Instead, most mercury is found in the form of an ore called cinnabar (mercuric sulfide or HgS). To extract the mercury, cinnabar is heated and then its vapor is distilled into liquid mercury.

Mercury is used in a wide variety of products today. Some of the most popular include thermometers, barometers, mercury vapor lamps, mercury switches, pesticides, batteries, pigments, and dental products.

96 Join the Discussion

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  1. Thoughts: This text was interesting because it told us three different meanings of Mercury (mercury). (Leslie) It was interesting to learn that Mercury, the god, was a messenger. (Cristian)

    Connections: This reminds me of the wonder where we learned about the falcons that sent messages during the war because Mercury, the god, was a messenger. (Luis) This reminds me of when we watched a wonder about the moon because Mercury is like Earth’s Moon. (Joaquin)

    Predictions: Have you ever been in a barrel wave? (Michelle) Who is Bethany Hamilton? (Maria) What is a maverick? (Jake) How do you surf? (Pedro) Why do sharks attack surf boards? (Briahna) What does surfing mean, bra? (Andrew) Have you seen the movie Soul Surfer? (Gabrielle)

    • HOORAY, we’re so glad that Mrs. Hess’ Class is here today! We are thrilled that you’ve been WONDERing about Mercury and mercury with us this morning! Leslie and Cristian learned some new things, Luis and Joaquin made some awesome connections, and Michelle, Maria, Jake, Pedro, Briahna, Andrew and Gabrielle have been predicting an ocean Wonder for tomorrow! Great work, Wonder Friends! Have a terrific Thursday! :)

  2. This was a beautiful video. I have seen a whole documentary on sharks and planets. It was so cool! Prediction: What causes Tsunamis?

    • WOW, that’s super cool, Taylor! We’re glad to hear about this interesting documentary you watched. Thanks for sharing your big wave Wonder guess for tomorrow! :)

  3. Hey guys you remided me that this summer I will be going on a science expedition and I will be sampling sharks. I will tell you how it went.

    • WOW, what an amazing summer that will be, Justin! It sounds like an adventure for sure– have fun on your science explanation! We CANNOT wait to hear more about it! HOORAY! :)

  4. I love looking at Mercury with my telescope! Roody is scared of everything but the telescope, so he likes it, too. I have a question that the passage or video did not answer: How close to Earth?

    • We are so excited that you enjoy WONDERing with us, Roody and I! It sounds like you two are a great scientific team! Mercury is pretty far from Earth… more than 50 million miles! Mercury is often difficult to see from the Earth, so we’re glad your super telescope can help you! :)

  5. Hi Wonderopolis!

    We didn’t know that Mercury wasn’t just a planet!
    How did you get the camera under the water to see the sharks in the video? We thought a lot about that video.
    We predict tomorrow’s wonder will be about Hawaii, a person surfing and maybe falling in the water, or waves.

    • Hey there, Froggy1! It’s so exciting to hear about all you learned today. There are very cool and advanced cameras that can capture things underwater– isn’t that cool!? We look forward to catching a wave with you tomorrow! :)

  6. Sorry I wasn’t on yesterday, the Internet in the school was off because of a storm. In our upstairs hallway we had a barometer that had mercury in it. I also know that eating to much tuna will make you sick, because tuna contains mercury. ;)

    • Oh, we’re so glad you’re back Claudia! We’re sorry to hear about the big storm near your school! We are glad about all your awesome connections to today’s Wonder, and you’re right… too much tuna can lead to too much mercury! :)

  7. We wondered how Mercury could get so cold when it is so close to the sun. But then we learned that it has no atmosphere to hold in the heat.
    We really liked the video!

    • Hello Sanaa, Kassidy, Big Madi, and Mrs. McNab’s 1st Grade Class! Thank you for WONDERing with us today – it’s been great! :)

      We’re happy to hear that you all enjoyed the video, and you learned a few new things with us today! HOORAY for all of you and your great work! We look forward to seeing you soon! :)

  8. We learned mercury can be deadly and we also learned that Mercury was a Greek god in mythology. We thank you again for the great informative video.
    We “wonder” about tomorrow’s clue. We are thinking…..
    Tsunami’s or surfing the ocean or one more clue from our super sleuths… what are surf boards made of.

    • Hello pinkpopstars, Hayden and Mrs. Larsen’s Detectives! Pinkpopstars and Hayden, we’re glad you learned all about sharks today!

      Mrs. Larsen’s Detectives, thank you for visiting us today! We sure did learn a lot about mercury, and Mercury! Thanks for sharing your wave of a Wonder guess! :)

  9. Thoughts, Connections, Questions: Savion- Can mercury kill someone instantly? Josh- I play a computer game that involves mercury. I already knew about it before this. Hayden- At my old school, we did a science project about the planets and mine was about Mercury. Bryan- I played Earthworm Jim and there was a level that looked like Mercury. Aaliyah- How many colors can mercury be? David- I played a game that you are actually on Mercury.

    Predictions: Bryan- How can you surf? Cassie- How do you make a surf board? Savion- Who was the first surfer? Sierra- What is in water? Hayden- Have you gone surfing? Aaliyah- What causes waves? David- What is the biggest wave? Trevon- How do produce waves? Christian- Have you ever been to Hawaii?

    • It appears that many of our Wonder Friends are familiar with mercury… or Mercury! Thanks for sharing your comments, Savion, Josh, Hayden, Bryan, Aaliyah, and David! Your computer games, science projects and thoughts are spectacular! :)

      Bryan, Cassie, Savion, Sierra, Hayden, Aaliyah, David, Trevon, and Cristian, thank you for your awesome Wonder predictions! You’ve made quite a splash! :)

  10. New learnings: I didn’t know that mercury could be so deadly (James). We were excited to learn the multiple meanings of mercury (Bailey). I learned that mercury came from volcanoes (Mihir). The whole idea of the element mercury was new to me (Kambry). I did not know that mercury turned to little beads when spilled. (Gabe).

    Thoughts: It is interesting that something you put in your mouth like a thermometer, has mercury inside of it (Maya). I always thought that mercury (element) only came from Mercury (Kaden).

    Can’t wait for tomorrow!

    • Thank you for your awesome thoughts about today’s Wonder, Mrs. Curry’s Class! We are glad you all shared what you learned today, especially because there are so many meanings to the word mercury! :) Thanks to James, Bailey, Mihir, Kambry, Gabe, Maya, and Kaden for sharing your connections and thoughts! WOOHOOO for learning and WONDERing! :)

  11. Hey Wonderopolis! I know all of the types of Mercury/mercury and I’m proud! Sorry I haven’t been on for a while, I have been really busy. P.S., do you have any wonders about The Titanic, Horses, or Rattlesnakes? P.P.S, I think tomorrow’s wonder is about surfing or bodies of water. ;) (;

  12. Now I know why mercury was no longer used in thermometers because they bcome a solid when under 38 degrees below zero. Thanks Wonderopolis!

    • You’re learning something new with us, how great, Walter! Thanks for telling us about what you enjoyed as you WONDERed today! :)

  13. We didn’t know that mercury could have iron in it or that it is poisonous!

    It is so cool that people weigh less on Mercury than on Earth! We can’t imagine living on a planet that only has 88 days in a year!

    We predict that tomorrow’s WONDER will be about surfing, the beach, the ocean, or waves.

    • Hey there, Mrs. Tompkins’ Class! We are glad you shared your Wonder comments with us today… we think an 88 calendar year would take some getting used to, also! WOW! We’d feel light as a feather during our short year on Mercury! We’d have to get used to the weather, too! :)

      Thanks for sharing your splash-tastic Wonder predictions! :)

  14. I knew both types of mercury the planet mercury and the element of mercury. The element is on the periodic table of elements and the symbol on the periodic table of element is Hg also mercury is known as quicksilver and Hydrargyrum. Mercury is also a planet but mercury is the closest planet to the sun and first in our solar system it’s also the hottest planet in the solar system which is sort of bad because we can’t live on Mercury because we would burn to death from the sun.

    • Thanks for sharing your comments, Tony, Cody and Madison! We’re glad you’re here today! :)

      Tony, you did a fantastic job of summarizing today’s Wonder, and what you learned, too! It would be quite difficult to live on the planet Mercury without proper attire! :)

      Cody, mercury can be dangerous in large quantities. For example, it’s important to limit your intake of certain fish, like tuna, due to mercury. :)

      Thanks for sharing your comment, Madison! We are glad you’re here today! :)

  15. Dear Wonderopolis,

    We liked learning about the different types of Mercury and we really liked seeing the sharks in the video. Some of us just thought Mercury was a planet. Thank you for teaching us something new!

    Predictions: We think tomorrow’s wonder will be about how waves are made, a surfer, about the game called Subway Surfers, Hawaii, or surfing the internet.

    Your wonder friends,

    Ms. H’s class

    • Hooray for Ms. H’s Class! You certainly did learn something new today, and we’re happy to hear it! Thanks for all your awesome predictions for the next Wonder of the Day®, Wonder Friends! We are glad you’re liked the sharks in Wonder video today! :)

    • We think Wonder Friend Mystery, Brittany and Opinion_girl.13 are on the same page with tomorrow’s Wonder! Thanks for sharing your predictions to the next Wonder of the Day®! Thank you for visiting us today! :)


    We are so scared we’re going to eat too much seafood because we don’t want to eat the poison mercury!

    Why do they put that metal thing into the sharks? Why would they put mercury in dental products if we put them in our mouth?

    We think tomorrow’s wonder of the day is going to be surfing in the ocean!


    • Hey Ms. G’s Class, we don’t want you to be scared! Mercury is an important metal, but it can be harmful if swallowed. Mercury is in a lot of different products, but it’s only harmful when ingested. Thank you for sharing your comment and for telling us your prediction, too! :)

  17. Did you know that the Chinese Emperors used to use mercury to torture people? The people were quite a gruesome sight after they were tortured. :( Also, tuna contains mercury, and that’s why my dad doesn’t let me eat tuna.

    • Hey there, Calvin, Ethan and Madeline! We enjoyed reading your comments today, and we’re glad you have been WONDERing on your own!

      Calvin, thanks for your awesome prediction!
      Ethan, Mercury is more than 50 million miles away from Earth- what a trip!
      Madeline, we are quite sorry to hear about the Chinese Emperor and former practices with mercury. We are glad you’re thinking about keeping yourself safe from mercury, too! :)

  18. Mercury is the 7th planet in the solar system. People say that it is covered in water and that it has oxygen like the Earth.

  19. I didn’t know that Mercury wasn’t just a planet. I wonder if you can die from how hot it is on Mercury if there was life on it. I had no idea that Mercury is a place named after a Roman god. That is so cool. I wonder what the next wonder will be.

    • Hey there, Daniel, Alex V. and Brooke!

      Daniel, thanks for summarizing what you learned from today’s Wonder about mercury, and Mercury. Great work! :)
      Alex, nice work today! Mercury is a very cool planet to Wonder about! :)
      Brooke, we like your comment, but don’t forget that Mercury was a Greek god! :) We hope to Wonder with you again soon! :)

  20. I can’t believe that if you weigh 70 pounds on Earth you only weigh 27 pounds on Mercury, that’s crazy. This is because of gravity. I still wonder how much I would weigh on Mercury, being 75 pounds.

  21. Why would mercury be in dental products if it’s poisonous? I wonder why mercury is so easy to melt if it is metal? :)

  22. I had no idea Mercury was also a god’s name that’s very interesting. I think Mercury sounds like an interesting planet!!! I also had no idea where the name Mercury came from!!! So that’s nice to know!!!

    • McKenna, Michael, and Amme, you did a SUPER job of WONDERing with us today! Thanks for visiting! :)

      McKenna, we bet it would be super cool to travel to a place where we were nearly weightless! We bet you would only be a few pounds heavier… perhaps close to 30 pounds?!

      Michael, great questions! Mercury is a very interesting metal, and it’s used in many products for the right reasons, like dental products. You won’t ingest it while you’re at the dentist!

      Amme, we are glad you’ve been thinking about all the definitions of the word Mercury… and mercury! We are excited to Wonder about the solar system and science with you! :)

  23. I think it is really cool how there is living life on Mercury. I think Mercury is a great place for scienctists to discover because, of the living life and water and land there is. I think sciectists might discover different things and items on Mercury than planet Earth.

  24. Mercury seems like a really cold planet! (Hannah)

    I didn’t know Mercury was very cold and very hot! I thought it was only hot. (Alex)

    Mercury seems really dangerous. I’m talking about the chemical element – like on the water they were talking about. (Rahil)

    Thank you Wonderopolis for always teaching us something new! (Mrs. Zitar)

    I think tomorrow’s wonder is going to how to surf. (Paige)

    I think the next wonder is about the beach. (Allen)

    I think the next wonder is about tsunami (Lucas)

    I think the next wonder is about surfing too.

    • Hey there, Aubree and our Wonder Friends in Mrs. Zitar’s Class! Thanks for joining us today for our Wonder! It was out of this world! :)

      Aubree, you’ve been doing a fantastic job of using your SUPER imagination today! :) We really enjoy thinking about cool planets, too!

      It’s awesome that our Wonder Friends have shared so many SUPER comments with us! Thanks, Hannah, Alex, Rahil, Paige, Allen, Lucas, and Mrs. Zitar for using your context clues to Wonder and predict! GREAT WORK! :)

  25. Mercury is a planet and a mineral type thing.
    The planet Mercury is the closest to the sun. It is the smallest planet, it only orbits around the sun in eighty-eight Earth days.
    The Greek believed that Mercury was a god.

    P.S. If your wondering why I have two posts was because I accidentally pushed the post button and I wasn’t done.

    • Hey there, Justin, Dillon and Kelsey! It sounds like all of you have a cool connection to today’s Wonder! Justin, great points! It would take some adjustments for us to live comfortably on the planet Mercury! Dillon, thanks for sharing what you have been up to in school- what a great connection to your science unit! Kelsey, thanks for summarizing what you WONDERed about today! Great work! :)

  26. I think Mercury is actually a really cool because it’s a really pretty planet and there are a lot of things that you probably do not know about mercury that are really cool. I think it’s cool that you are a different weight if you go on Mercury or another planet. It’s like you’re a whole different person on another planet.

    • Great points, Laura Y! We are so excited that you’ve been thinking about how different life would be on Mercury! We’d have to get used to the weight and the temperature! Thanks for sharing your comment and WONDERing with us today! :)

  27. So why do scientists look at sharks so much and not fish? Wouldn’t fish have a better chance of mercury than sharks because don’t the fish eat the mercury?

    • Happy Friday, Wonder Friend! You have some really awesome questions! The school library has TONS of information to share with curious WONDERers like you! Don’t forget to share what you discover with your Wonder Friends here are Wonderopolis! See you soon! :)

    • Isn’t WONDERing awesome!? There are new things to learn every day! Thanks for stopping by to Wonder with us, Zach!

  28. Before I read this I thought there was only two Mercurys(planet and Roman God.) When I read this I said “Oh.” because there is more than 2 mercurys! Which I find super cool. But I’m wondering why the third mercury is in Dental Products because is it in toothpaste or the stuff that the dentist uses? I’m figuring it’s supplies by how poisinous it is but i’m still wondering.

    • Hey there, Wonder Friend Paula! We love to hear that you are learning new things here at Wonderopolis! We Wonder how smart your dentist will think you are if you ask him if there is Mercury in any of the products he uses! Have a WONDERful day! :)

  29. Hey wonderopolis do you have anything about basketball or dolphins or sharks?

    I also think that tomorrows wonder of the day will be about how do you surf?

    • Fantastic question, Kate! Interestingly, no human has ever gone to any other planet other than Earth! The moon isn’t technically considered a planet, even though it looks like one in the sky! Scientists are hoping to walk on Mars soon, though! How cool would that be?! Thanks for WONDERing with us! :)

    • Hey there, Wonder Friend! We are so glad you are WONDERing with us today! Mars could be quite dangerous without the correct protective gear! Scientists are developing that gear so that one day, they might be able to put a man on Mars! How awesome is science?! See you again soon, Cool5!

  30. I think that mercury is a mineral thing that people might want to build stuff with it. I think mercury is really cool.

    • What a SUPER connection to what you’ve been doing in class, Wonder Friend! Thanks for sharing your comment with us! :)

  31. Hi! This is a Wonderful :) Wonder!
    Next time, if you are doing a planet, can you do it about Jupiter (<3)?

    Thank you! This will really help me in science class!

    • Thanks so much for sharing your awesome comment, Rainbow Dash! We are so excited that you are WONDERing about the solar system with us! We think tomorrow’s Wonder will be out of this world! :)

  32. This wonder was awesome so now I know way more stuff about mercury we are doing space in science at scool and this is going to help soooooo much thank you very very much wonder.

    • We are so glad this Wonder connects to what you’re learning in school, Eve! Keep up the great work and we hope to Wonder with you soon! :)

  33. Thanks so much for all that great info. We are doing space in science right know and all this info will be great. I can not believe that mercury was one of the gods. That is so cool I did not know that. Anyway thanks so much wonderopolis!

    • Hey Kaite, thanks for sharing your comment! It’s great that you learned something new with us today– what a STELLAR connection to what you’re studying in school right now! Keep up the great work, and we will Wonder with you soon! :)

    • Great work, Timothy, we’re glad you shared what you learned about the planet Mercury! We Wonder if you would like to go to space in the future? :)

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Have you ever wondered…

  • What is mercury?
  • Who was Mercury?
  • Where is Mercury?

Wonder Gallery

921Vimeo Video

Try It Out

Recruit a few friends or family members to help you explore one or more of the following fun activities to extend your learning about mercury (or Mercury!):

  • Would you want to live on Mercury? Jump online to explore Mercury in greater detail. Based upon what you learn, decide whether you would want to live on Mercury or not. Discuss your opinion with friends or family members. Do they agree? If you wouldn’t give up Earth for Mercury, would you ever want to visit there? Why or why not?
  • Have you ever seen a thermometer with mercury in it? For most kids, a mercury thermometer is one of the few times they’ll see mercury in action. Did you know that you can make your own thermometer without mercury? It’s true! All you need are a few simple supplies, such as a clear bottle, water, rubbing alcohol, a straw, modeling clay and food coloring. If you need any of these items, ask a friend or family member to take you to the store to get what you need. When you have your supplies ready, just jump online and follow the simple directions to Make A Thermometer!
  • Up for a challenge? Head over to the Internet to do some basic research on the Roman god Mercury. What was he like? Do you share any traits with Mercury? Once you have a grasp of who Mercury was and what he was all about, write a short story featuring Mercury. It can be based upon something you learned about Mercury, or it could be a completely fictional account of what would happen if Mercury discovered a time machine and landed on modern-day Earth. It’s up to you. Be as creative as you want to be!

Still Wondering

Science NetLinks’ Day on Mercury tool allows the user to experience a typical day on Mercury, which is actually 176 Earth days.

Wonder What’s Next?

Tomorrow’s Wonder of the Day might have you saying, “Surf’s up!”

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