In this lesson, students will learn how scientists like Robert Ballard use sonar to investigate the depths of the ocean. They will learn that some animals have an unusual way of figuring out what is around them in the dark. They will study the echolocation capabilities of bats and think about how ocean scientists can learn from these animals to develop deep-sea exploration techniques.

Geography, physics, earth science

Standard 15: "How physical systems affect human systems"
Standard 17: "How to apply geography to interpret the past"
Standard 18: "How to apply geography to interpret the present and plan for the future"

Two to three hours

• Computer with Internet access
• Bucket or other container filled with water (to demonstrate the weight of water)
• Model, puppet, or drawing of a bat

Students will

• discuss their experiences with echoes;
• discuss how echoes work and how they are used in deep-sea exploration;
• view pictures of deep-sea exploration vehicles;
• hear a story about a bat using echolocation; and
• teach a friendly bat about its own echolocation abilities and how these special abilities might help ocean scientists.

To introduce the concept of water pressure, ask students whether a bucket filled with water is light or heavy (do a demonstration in the classroom, if possible). Ask them to imagine being at the bottom of the ocean with the weight of an ocean's worth of water pressing down on them. Explain that, because the weight of the ocean is so extreme, scientists who want to study the deepest parts of the ocean must use special equipment.

Then ask students if they have ever heard an echo. Perhaps they were in the school gym or auditorium, a long hallway, or a valley. What did the echo sound like? If they were with other people, did everyone's echoes sound alike? Were they able to make the echo happen again, even if they moved to another location?

Explain to the class that echoes are produced when sound travels from its source (e.g., their mouths) to a solid object (e.g., a wall) and bounces back to their ears. We don't always hear echoes, of course; the situation has to be just right. If possible, take the class into a large empty room or corridor (a school gymnasium, for example) and see if they can make their own echoes. Ask them to notice whether any particular areas seem to facilitate echoes and whether the echoes they can produce in this place are as substantial as echoes they have heard elsewhere.

Tell students that in order to explore the bottom of the ocean, scientists use equipment that creates echoes. This equipment sends sound out to the ocean floor, and the sound bounces back in different patterns. The scientists then use special equipment to turn the sound into pictures that show what the ocean floor looks like. Just as their echoes might sound different in different parts of a room or valley, the deep-sea equipment "hears" echoes that sound different in different areas of the ocean; shallower areas make different echoes than deeper places. The equipment used to send and receive the sound is called sonar, and the process is called echolocation.

Have students go to the following Web sites to look at pictures of remotely operated deep-sea vehicles and ask them to contribute words describing what these vehicles look like. Would they want to go under water in one of these vehicles?

NOAA: Ocean Explorer—Submersibles
PBS: Into the Abyss—Deep-Sea Machines

Inform students that some animals, such as some bats and some whales, use a similar method to find out what's around them. Read to the class the story of Echo the Bat, or just read the part that discusses Echo's echolocation capabilities. After reading the story, discuss the bat's echolocation ability and compare it to the echoes they are capable of making.

Ask students how they think deep-sea scientists can learn from bats. It may sound like a strange combination, but the bats are naturals at an activity that the scientists want to learn how to do well. Would students recommend that ocean scientists spend some time learning about bats?

Show students a picture of a bat, or bring in a stuffed or puppet bat. Have the bat tell the class that it is really interested in learning more about the ocean floor and thinks it might be able to help scientists do this, but it needs your students to show it how. Lead students in a discussion and/or have them draw pictures that will help the bat understand how its echolocation capabilities can teach scientists how to develop their own sonar techniques. Students need not worry about the scientific and technical equipment but should just focus on how the bat uses echolocation.

Have students simulate an echo by asking one student to get behind a screen or door and mimic another student who will call out words in the first student's direction. The student behind the door will be the "echo." Ask other students to explain how the echo would have worked had it been real. One or two students can get out of their seats and trace the movement of the sound from one place to another by walking across the room.

Then have students simulate echolocation in the deep-sea by holding a model submersible (it could just be a cup that represents a submersible) up in the air above the classroom floor, which will model as the ocean floor. They should then move their hands in the direction that the sound will travel from the vehicle to the ocean floor and back to the vehicle.

• Ask students to think of other animals that have interesting behaviors. Can they think of any behaviors that people can or should learn from these animals?
  
  
• Have students take another look at the deep-sea vehicles they have seen on the Internet and discuss or write stories describing what it might be like to spend a few hours in one of them.

NASA/GSFC: Echo the Bat
NOAA: Ocean Explorer
National Geographic: Deep Sea VentsScience at the Extreme
PBS: NOVA OnlineInto the Abyss