Gravity And Tides Worksheet

Tides are not caused by the direct pull of the moon's. 7C: Relate the position of the Moon and Sun to their effect on ocean tides. This worksheet allows students to draw the high tide and low tide heights for spring tides and neap tides side-by-side to allow for an excellent visual comparison. This section is no longer up to date as of September 2008. And then I took a closer look. Visualize the sizes and distances between different heavenly bodies, and turn off gravity to see what would happen without it!. Without it, the tides wouldn't exist, the ocean would stagnate, and life here on Earth. This was done by measuring the acceleration due to gravity as accurately as possible and then calculating the mass of Earth M from the relationship Newton’s universal law of gravitation gives [latex]mg=G\frac{mM}{r^2}\\[/latex], where m is the mass of the object, M is the mass of Earth, and r is the distance to the center of Earth (the. 24 h and 50 min c. Standard and Secondary Ports. At those times the high tide is lower than usual, and is called a. Because the Moon is closer to the Earth, it has the greatest effect on our tides. What do you think happened?. “Tides are caused by the gravitational effects of the Sun and the Moon on our oceans. Super Teacher Worksheets has worksheets for all types of elementary science topics, including animal classifications, plant life, food chains, weather, insects, and matter. They are the periodic rise and fall of the earth's bodies of open water, and are a result of the gravitational pull of the moon and sun on the earth, as well as the perpetual spinning rotation of the earth itself. This force is called gravity. Grade: 5 WORKSHEETS. Student Hand-out: Includes both part A (waves) and part B (tides), with relevant web links embedded in the file. Paraphrasing and summarizing worksheets. Displaying all worksheets related to - Moon And Tides. On which days did the observer experience a spring tide? _____ When there is a smaller difference between high and low tide, it is a. There are two gravitational bodies that affect the tides: THE SUN and T HE MOON. Physical Science 8th Graders, be the leaders I know you can be! Physical Science is broken into 3 main units: Astronomy, Chemistry and Physics. There is a possibility you might get wet. When this happened he realised there was a force that made it occur, and he called it gravity. 4 Earth's Moon Table of Contents. The Universe – Tides Notes & Worksheet 1 Tides are the regular rising and falling of the sea. (None of the distances. Studyladder is an online english literacy & mathematics learning tool. Gravity from the Moon and Sun are. However, the moon is large enough and close enough that its gravitational force has a noticeable effect on large bodies of water on Earth. Because the moon is smaller than the Earth, its gravity is less, but this force does have a pulling effect on the seas and oceans. moon lesson plan phase solar system space science worksheets astronomy primary teaching learning reading comprehension students elementary education curriculum kids theme unit resources activity A science reading lesson on understanding our solar system. In the Northern Hemisphere (NH) summer (June 21), the Sun sits above 23 degrees North, while in the NH winter (Dec 21), it is directly above 23 degrees South. When the waters of seas and oceans on the side of the earth facing the moon is attracted upwards, they cause high tide and the area where waters have moved to the regions of high tides forms a low tide. Map of A diagram from 1891 showing position of the earth, moon, and sun during spring and neap tide. The combined tide raising forces of the Moon and the Sun are at their greatest effect when the Sun and the Moon are in line with the Earth. Factors such as local topography and weather contribute to the timing and height of tides, but the primary reason for tides is the gravitational attraction between liquid water on the Earth and the Moon. It is phenomenon. What causes this "motion of the ocean"? In one word, gravity. Some of the terms you'll be assessed on include spring tides. There are several types and effects of tides, and this quiz/worksheet will help you test your understanding of them. org Goal: The kinesthetic learning activity will help students learn about the Earth's tides by acting them out. The factors which cause tides. two daily tides being explained by the Moon's gravity. When making the worksheets, I used the data for high tides since it showed a better range of data for the students to create the graph. There is a PDF and an editable version of each file. Physical Science 8th Graders, be the leaders I know you can be! Physical Science is broken into 3 main units: Astronomy, Chemistry and Physics. About This Quiz & Worksheet. When the moon is orbiting around the earth, the side of the earth it is on is mostly effected, thus causing high tides. and cooler than a giant. This is a set of four labs that teach the basic concepts of gravitational force, and how it relates to tides on the Earth. Explain the effect of gravity in your drawing. Spring high tides are higher and spring low tides are lower than average. A high tide results on the near side of the Earth-moon alignment. At this time, expect largest tidal range of the year because, at the equinoxes, the Moon and Sun are aligned with the equator. Some tide tables also show the times of the sunrise, sunset, moonrise, and moonset. Module 8 { Refraction { Instructions CAUTION: Before you start this experiment, understand that you are expected to follow directions EXPLICITLY! Take your time and read the directions for each step and for each part of the experiment. 665 Gal or 980665 mGal. The Earth's ocean s respond to the moon's gravitational pull by bulging and dipping as the moon rotate s around the Earth. TIDE The darkest part of a shadow UMBRA The force of gravity on an object. This relationship was first published by Sir Issac Newton. On Earth, gravity gives weight to physical objects and causes the ocean tides. Extreme tides, when there is the greatest daily variation between the heights of the low and high tides, are widely known as spring tides. They will also label the locations of the Moon on an orbital path of the Moon for each tide type. universal gravitation. All coastal areas experience two high tides and two low tides over a period of slightly more than 24 hours. At those times the high tide is lower than usual, and is called a neap tide. Back to: Science California Science Grade 5 Chapter 6. Visitors to the beach may appreciate high tide while rescuing their sand buckets and towels from incoming water. Its gravity reaches the Earth and pulls the oceans toward the Moon, causing the tides. There is a PDF and an editable version of each file. Neap Tides. Gravity helps the Earth to stay just the right distance from the Sun, so it’s not too hot or too cold. Newton's second (force equals mass times acceleration, F=ma) and third (for every action there is an equal and opposite reaction) laws. Team Moon Teacher's Guide. 3% of its volume below the level of the surface, and 91. apparent weight Thursday. The water moves in different ways and different directions. HW Tides Reading Comprehension Worksheet REGENTS EARTH SCIENCE Tides Reading Worksheet Name Date Period The daily rise and fall of the ocean waters are called tides. generation site. Tides occur because of the pull of gravity of the Moon and the Sun on the Earth's oceans. The force of gravity can act across large distances and its effect can even penetrate across and into the vacuum of outer space. planet and moon, and, finally, 4. Because of the way the Earth is tipped to one side as it rotates on its axis and the way the Moon revolves around the Earth, the gravitational pull between Earth and Moon gets stronger and weaker (peaks and ebbs) twice a day. There are approximately 2 high tides and 2 low tides every 24 hours. See what living things can do! In this science worksheet, your child connects pictures of the activities of living things to the words they represent. phases, solar and lunar eclipses, and tides. The second part of this activity is the marble race down the plane. neap tides c. Gravity is an attractive force between any two objects in the universe. It is said that he saw an apple fall from a tree and accelerate towards the Earth, and he named the force responsible for pulling the apple towards the Earth gravity. Explain the cause of tides. Tides 19 • Friction drags water along with the Earth’s rotation, making it go ahead of the Earth-Moon line • Moon’s gravity pulls the water towards the Earth-Moon line, slowing Earth’s rotation. • How do gravity and energy together allow us to understand orbits? – Change in total energy is needed to change orbit – Add enough energy (escape velocity) and object leaves. What Physics Teachers Get Wrong about Tides!. In fact that is absolutely vital to the health of our planet: the tides make the water of the seas move and that ensures that oxygen and carbon dioxide are mixed with the water - all life in the oceans need these gases. The more massive an object is, the. Solar tides are caused the same way as lunar tides, except that the sun's gravity is pulling the water and that. This phenomenon is responsible for the rise and fall of the tides. An early explanation of tides was given by Galileo Galilei in his 1632 Dialogue Concerning the Two Chief World. Another bulge occurs on the opposite side, since the Earth is also being pulled toward the moon (and away from the water on the far side). In this science worksheet, your child learns about the waxing and waning Moon and then draws the phases of the Moon between new Moons. But since the forces are smaller, as compared to the moon, the effects are greatly decreased. This activity ties together spring tides, neap tides, moon phases, chart reading skills, graphing skills, and analyzing data skills. Oceanography and Hydrology questions for your custom printable tests and worksheets. 74, the tidal wave is higher than usual. The Universe – Tides Notes & Worksheet 1 Tides are the regular rising and falling of the sea. Graphing Tides & Moon Phases. Now the lunar tide and solar tide cancel each other out, leading to a smaller tidal range than average. Explain why rotating giant wheels will likely be used as space habitats in the future. The gravitational pull of the Moon causes high tides on that, and the opposite side, of the Earth. Find out how the moon controls the gravity of tides on Earth, and how tides can provide us with renewable energy sources!. without referring to your lecture notes). How Gravity Affects the Sun, Moon, and Earth Answers 1. Black holes have the strongest gravitation pull in the whole. Unit 3 Gravity Introduction Gravity cannot be held responsible for people falling in love. Active Reading continued In the space provided, write the letter of the description that best matches the term or phrase. Extreme tides, when there is the greatest daily variation between the heights of the low and high tides, are widely known as spring tides. On the other hand, the other side is not as effected, causing low tides. gravity 17. •How does gravity cause tides? —The Moon’s gravity stretches Earth and its oceans. Draw the relative position of the E-S-M during one of these tides and label which type you illustrate. Sketch the positions of the Earth, Moon, and Sun for each spring and neap tide. As Earth rotates, the moon's gravity pulls on different parts of our planet. Patreon is empowering a new generation of creators. achievementstandards. txt) or read online for free. Tides occur because of the periodic rise and fall in sea level with respect to the land. Each lesson plan follows the 5E model and provides you with the exact tools to teach the concept. Gravity and its effect on Moon 6. Tides occur because of the pull of gravity of the Moon and the Sun on the Earth's oceans. 9 Ocean Tides (pages 246-248) twice per day 44. High Tide and Low Tide - A Craftivity to Teach Tides Knowing that the moon's gravitational pull is what causes the tides is an important concept for students to know, but understanding what it looks like can be a bit tricky. Worksheet on observing the phases of the moon : A : Predict the type of tide produced by the different positions of the Earth and moon system. Gravit y also causes things to fall to the ground, and causes the ocean's tides, and causes hot air to rise whi le colder air falls (which in turn causes wind). But how come both objects don't just pull into each other until the collide?. The Moon's gravitational pull affects how high or low tides are. Though this pull (or ­ TRACTIVE force) is felt around the globe, nowhere is its effect more noticeable than on the free-moving water. The two gravity students will pull again on the strings, toward and away from the moon. Gravity helps the Earth to stay just the right distance from the Sun, so it’s not too hot or too cold. This effect causes low tide. Also print your data. Back to: Science California Science Grade 5 Chapter 6. How long does it take the moon to revolve around the Earth? a. Tides are mostly caused by … A) The spinning of the earth C) The moon’s pull of gravity on the earth B) The orbiting of the earth around the sun D) The sun’s pull of gravity on the earth 3. Unlike the electromagnetic force, gravity does not have an opposite “anti-gravity” force of repulsion. Newton's place in the Gravity Hall of Fame is not due to his discovery of gravity, but rather due to his discovery that gravitation is universal. From falling apples to rising tides everything is affected by gravity. *Rotation and Revolution Notes *Rotation and Revolution Review Worksheet ars due to the rotation and evolu _____ 2. new_tide - ASPIRE. b) The moon changes shape as it orbits the earth. This relationship was first published by Sir Issac Newton. Search the world's information, including webpages, images, videos and more. six times that of Earth. Tides are mainly due to a gravitational attraction between the moon and every molecule of water in the Earth's oceans. org Goal: The kinesthetic learning activity will help students learn about the Earth's tides by acting them out. Graph your data by hand and answer the questions. It essentially pulls up a bulge in the ocean on the side of the earth closest to it. Read and Download PDF Ebook explore learning gizmo ocean tides answer key at Online Ebook Library. The spring-neap cycle causes tides to build to a maximum and fall to a minimum twice each month. between high tides and low tides, compared with spring tides. Tides are the daily rise and fall of sea level at any given place. 1N downward pull of gravity, so the ball will rise to the surface when released. Although it may be difficult for kids to grasp, you can explain how tides are caused by the force of gravity from the moon and the sun pulling on the ocean waters of the earth. At times, the. Shows how the sun, moon, and earth's rotation combine to create tides. On the other hand, the other side is not as effected, causing low tides. Sketch the positions of the Earth, Moon, and Sun for each spring and neap tide. The currents carry heat. The pull of the Sun and Moon also causes Earth’s ocean tides. What causes this "motion of the ocean"? In one word, gravity. There are two spring tides every lunar month and two neaps. Then fill again and play!!. The factors which cause tides. Sometimes the sun and the moon are lined up with the earth, but most of the time they are not. How to teach gravity Felix Baumgartner's amazing 24-mile plunge to Earth is a great way to introduce the subject of gravity and the Guardian Teacher Network has lots of resources to help. The ocean does not always stay the same depth. The Moon exerts a smaller gravitational force than Earth. This phenomenon is responsible for the rise and fall of the tides. com to get the most current listing of movie worksheets. Remind them that even though their weight would change if. Fling the Teacher - Oceans This game allows students to answer 15 questions about the Ocean. When teachers explain ocean tides, they frequently describe how the moon's gravity pulls on Earth and all of its water. This, they often say, leads to a gravitational imbalance, which stretches. Watch It! - Video LinkQuestion #2 - The first few people in the video had some misconceptions about what causes the moon to change. Gravity is also the cause of tides. I discuss Einstein's Special. When the moon is orbiting around the earth, the side of the earth it is on is mostly effected, thus causing high tides. Teaching Earth-Moon Scaling. It occurs because of the gravitational forces between the Earth, the sun, and the moon. you just watched a 1/2 ounce object overcome the force generated by an o. • Why do all objects fall at the same rate?. There are approximately seven days between springs and neaps. Ocean currents are the continuous, predictable, directional movement of seawater driven by gravity, wind (Coriolis Effect), and water density. without referring to your lecture notes). There is a PDF and an editable version of each file. The gravity of the Moon and the Sun causes tides. gravity of the sun and moon produce an especially high tide on two sides of the planet - called a spring tide, and an especially low tide on the other two sides. On Earth, gravity gives weight to physical objects and causes the ocean tides. Worksheet 1 Forms of Energy Key. Click the image below. spring tides – tide with the greatest distance between high tide and low tide. 31668×10 25. This is a set of four labs that teach the basic concepts of gravitational force, and how it relates to tides on the Earth. Now that students have learned a little background information about tides, I have them participate in the Gravity and Tide Lab, courtesy of Carolina Curriculum. two daily tides being explained by the Moon's gravity. Gravity is a(n) force that pulls objects together. The moon's gravity pulls on the earth and causes tides. Even though the idea of gravity is pretty obvious, scientists didn't have a word for it or a real understanding of it until 1687, when Sir Isaac Newton published his theories on the Three Laws of Motion. Useful materials include: rulers, printed copy of local tide tables from NOAA and map of local water body (Puget Sound in this case). Rotation will supply a support force for astronauts, giving them a sense of weight. Grade: 5 WORKSHEETS. Use this lesson plan on Newton's Law of Gravity in conjunction with your other motion lesson plans that focus on Newton's Laws. An early explanation of tides was given by Galileo Galilei in his 1632 Dialogue Concerning the Two Chief World. Used by over 70,000 teachers & 1 million students at home and school. Gravity Gravity Neap tides occur when the sun and moon’s forces oppose each other. Goddard USD 265 does not discriminate on the basis of race, color, national origin, sex, religion, handicap/disability, or age as to treatment of students in programs and as to employment. Gravity is a force that always attracts or pulls objects toward each other without direct contact or impact. Worksheet 1 Forms of Energy Key. Neap tides have a low tidal range—there is less difference. Science Worksheets for 6th Grade. Even though the idea of gravity is pretty obvious, scientists didn't have a word for it or a real understanding of it until 1687, when Sir Isaac Newton published his theories on the Three Laws of Motion. The average person probably doesn't think about it on a daily basis, but yet gravity affects our every move. Find out more about this here. The Moon’s gravity affects the oceans on earth. You have seen this if you have been to the ocean. Our Restless Tides This online tutorial from NOAA about tides is very comprehensive with more detailed information. Low tides occur at longitudes that are 90° from the longitudes of locations that are experiencing high tides. The Moon's gravitational pull affects how high or low tides are. In addition, however, the Earth is tilted on it’s axis, which is what causes the seasons, but also affects the tides in an interesting way. Describe how the Solar System formed. pdf), Text File (. Science for Kids the free online science network. Table worksheet is a conversion table for counter values to gravity values for LaCoste-Romberg gravity meters and should be modified for the specific gravimeter used. (4 points) B. See what living things can do! In this science worksheet, your child connects pictures of the activities of living things to the words they represent. achievementstandards. For the Tide Level Observer Lab print out the Tide Level Observer Worksheet on the lab manual website. ) The Open Ocean An interactive game through BBC. The Ocean's Tides Explained The alternating pattern of rising and falling sea level with respect to land is what we know as the tides. SASCHIN'S INTEGRATED SCIENCE 9/10. The Absolute Base worksheet references relative gravity measurements to an absolute value; the user must enter a drift and tide corrected measurement taken at the. We hope you enjoy and have fun exploring our website. Calculations involving Standard and Secondary Port. When there is a smaller difference between high and low tide, it is a neap tide. The gravity of the Moon causes a high tide both on the side of the Earth directly below the Moon (sublunar tide) and the opposite side of the Earth (antipodal). Define tides. The alternating pattern of rising and falling sea level with respect to land is what we know as the tides. Sun’s Gravity and Tides. This is a set of four labs that teach the basic concepts of gravitational force, and how it relates to tides on the Earth. What is the real reason we have different moon phases?Question #3 - When the moon is between the Earth and the Sun what moon phase will this be?Question #4-Why doesn't the Earth block out the light between the Sun and the Moon during a normal month?Research It!. Science games for kids online: Free science activities, interactive physics games, chemistry, biology games for kids (girls/ boys) in grade 3, 4th, 5th, 6th, 7th, 8th, 9th, 10th, 11th, 12th graders, for middle/ high school students on the internet, for PC, Mac with no download. Our tides are controlled by the gravitational pull of the moon as it orbits Earth. Spring tides have a larger-than-normal tidal range (higher high tides and lower low tides). Identify the different shapes of magnets and common uses. ALL objects attract each other with a force of gravitational attraction. Earth, Moon, and Sun • Section Summary Gravity and Motion Worksheet Key Concepts • What determines the strength of the force of gravity between two objects? • What two factors combine to keep the moon and Earth in orbit? Earth revolves around the sun in a nearly circular orbit. Read the text below and with reference to your textbook PS7 Chapter 9. I get so many emails from NCLEX test takers that say there were medication questions on the nclex of medications that they had never heard of. How Does Gravity Affect Root Growth? Students create a simple plant experiment chamber, and use corn or bean seeds to test the effects of gravity (gravitropism) on root growth. When teachers explain ocean tides, they frequently describe how the moon's gravity pulls on Earth and all of its water. Sketch the positions of the Earth, Moon, and Sun for each spring and neap tide. 4 The main cause of tides is the moon. Every body of water, port, and harbor has its own tide table. The Science of "Romantic Gravity" but life here on Earth desperately needs the Moon's gravity. For the Tide Level Observer Lab print out the Tide Level Observer Worksheet on the lab manual website. tides every day - two. One, and fascinating in hatred of there was firmly seated around me that house of them–even the seasons. From its influences on the tides to the regulation of the seasons, we have many. generation site. Gravity, is the natural phenomenon by which physical bodies appear to attract each other with a force proportional to their masses. How much time passes between one high tide and the next? 12 hours. Explain how spring and neap tides are created. Ever wonder what makes the ocean tide come in and out? With this worksheet, your student will learn all about how the tides work, and he will be able to practice graphing some data on high tide and low tide activity. Enrich your study of physics with an activity about gravitational force. Suggested Grades 3rd Grade 4th Grade 5th Grade. The Earth's ocean s respond to the moon's gravitational pull by bulging and dipping as the moon rotate s around the Earth. Prior Knowledge Questions (Do these BEFORE using the Gizmo. Since the Moon has no gravity, they were dependent upon the application of Newton's first law to put them on the correct path to the Earth. They will also label the locations of the Moon on an orbital path of the Moon for each tide type. The pull is greatest on whatever is closest to the moon. Ocean tides are caused by the gravity of the moon. also affects tides. The varying circulations of the current of the sea water cause it to be brought up onto a landmass. Gravity is one major force that creates tides. Gravity is universal. We’ve been making our own hands-on exhibits here at the Exploratorium since 1969. pdf Size : 417. Teaching Earth-Moon Scaling. This causes the sun and moon to pull the water in two different directions. In addition, however, the Earth is tilted on it’s axis, which is what causes the seasons, but also affects the tides in an interesting way. When he returns several hours later, the castle is gone. Tides 10-15 UNIT 4UNIT 4 Chapter 10 Waves and Tides – Lab/Activity 3 Learning Outcomes: After completing this lab activity and studying Chapter 10, Tides, you should be able to: 1. Explain how two main variables determine the force of gravity between stars and planets. (Low tide will be at the sides halfway between the high tide bulges. They are the periodic rise and fall of the earth's bodies of open water, and are a result of the gravitational pull of the moon and sun on the earth, as well as the perpetual spinning rotation of the earth itself. 10 Questions The Moon's pull of gravity on the Earth. There are several types and effects of tides, and this quiz/worksheet will help you test your understanding of them. universal gravitation. Tides4fishing cookies are used to personalise content and ads, save your recent fishing sites and remember your display settings. com to get the most current listing of movie worksheets. Provide your best explanation for Earth's main high tide every day. Earth has more mass than the Moon. Whenever there is a full or new moon this occurs. 3 million Earths so its mass has a strong gravitational pull. Gravity represents the attraction between objects as it affects all the objects with mass. Coriolis effect. The water rises for about 6 hours, then falls for about 6 hours, in a regular cycle. What substance on Earth does the gravity of the moon have the greatest pull on? 4. Calculations involving Standard and Secondary Port. This phenomenon is responsible for the rise and fall of the tides. Another bulge occurs on the opposite side, since the Earth is also being pulled toward the moon (and away from the water on the far side). Gravity is the force that attracts all objects to one another. It's traveling. Team Moon Teacher's Guide. Compare different models of the solar system. What is a High Tide and when does it occur? High tides are a result of the gravitational pull between the Earth and it’s moon and the Sun. - Albert Einstein Gravity is the most familiar of forces, but the least understood. The earth's gravity keeps water on the planet's surface. Spring & Neap Tides ¥ Includes ef fect of sunÕ s gravity Ð Sun creates tidal crests as moon does of maximum tidal range Ð At latitude of Seattle,. Tides are caused by the attractive forces of the sun and moon. Tides result from changes in gravity at Earth's surface due to the moon and Sun. Spring tides and Neap tides. These are caused by the gravitational forces between the earth and the sun and the moon. The Earth is the only place in the known universe that supports life. The force of gravity from the Moon affects the Earth. Then Do Tides. Measurement of Absolute Gravity:. See what living things can do! In this science worksheet, your child connects pictures of the activities of living things to the words they represent. This particular lesson plan focusing on Newton's Laws of Gravitation is simple and easy to understand, making learning about gravity a simple process for physical science students. The Main Attraction Gravity. Neap tides occur during quarter moons. Understanding the law of gravity, one of the fundamental forces of physics, offers profound insights into the way our universe functions. How long does it take for high tide to occur? How long is the time between low and high tide? Tidal Variations - The Influence of Position and Distance. Life & Character - Isaac Newton was born prematurely on Christmas day 1642 (4 January 1643, New Style) in Woolsthorpe, a hamlet near Grantham in Lincolnshire. Online shopping from the earth's biggest selection of books, magazines, music, DVDs, videos, electronics, computers, software, apparel & accessories, shoes, jewelry. There is a PDF and an editable version of each file. The Sun and Moon both have an effect on the Tides. 97237 × 10 24 kg (1. We'll learn about why we don't fly off into space, what mass has to do with it, how does air resistance work, and why gravity is different on. Read pages 335 – 340 of your textbook to help answer these questions. Newton's Law of Gravity. Think and discuss: The Moon's gravity pulls on Earth. Since the Moon has no gravity, they were dependent upon the application of Newton's first law to put them on the correct path to the Earth. Relation between tides and timings 8. This force is always attractive, that is, it always works to pull the objects closer together. It is phenomenon. Choose from 303 different sets of gravity tides flashcards on Quizlet. 8: What are the zones of the intertidal zone? is the area that is above water at low tide and under water at high tide (in other words, the area between tide marks). universal gravitation. Tides tables are made only after observing conditions in a coastal area for a long period of time. Specifically, the gravitational forces of the Sun and Moon. Tide tables list the location, the date, the times of high and low tides, and the elevation of the water. 74, the tidal wave is higher than usual. On the opposite side of Earth from the Moon, the two gravity pulls of Earth and Moon are working in concert to cause the water to slightly bunch up.