Equator Definition and 102 Threads

The Earth's equator is an imaginary planetary line that is about 40,075 km (24,901 mi) long in circumference. The equator divides the planet into the Northern Hemisphere and Southern Hemisphere and is located at 0 degrees latitude, the halfway line between the North Pole and South Pole.In spatial (3D) geometry, as applied in astronomy, the equator of a rotating spheroid (such as a planet) is the parallel (circle of latitude) at which latitude is defined to be 0°. It is the imaginary line on the spheroid, equidistant from its poles, dividing it into northern and southern hemispheres. In other words, it is the intersection of the spheroid with the plane perpendicular to its axis of rotation and midway between its geographical poles.
When the Sun is directly above the Earth's equator (on the equinoxes of approximately March 20 and September 23), sunlight shines perpendicular to the Earth's axis of rotation, and all latitudes have a 12-hour day and 12-hour night. On and near the equator sunlight comes from almost directly above every day year-round, and thus the equator has a rather stable daytime temperature the whole year.

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  1. M

    I Gravity at Earth's poles vs equator

    I just saw a StarTalk video where Neil deGrasse Tyson says that gravity at the poles is lower than at the equator because, even though you are closer to the center, the mass around the equator outside the sphere below you somehow does not count (skip to 4:21 in the video). He is obviously wrong...
  2. Vic43

    Counteracting the inertia of Earth's rotation

    I am at the equator with a drone capable of 1000mph speeds and the ability to hover. If the sun (or another fixed point in space) was directly overhead and I waited for the earth to rotate 1000 miles then launched the drone and flew 1000mph against the earths spin till the sun was directly...
  3. G

    I Fake water spin experiments around the equator

    Hi. I just visited the equator in Ecuador, where they perform those fake water spin experiments on and a few meters north and south of the line. I know that the Coriolis effect is way too small on that scale, so how do they do it? They even let spectators pull the plug.
  4. H

    Equator of a Planet with Four Spatial Dimensions is a 4D Torus

    A 4D planet has no axis of rotation. Nothing special about planets, all freely rotating 4D bodies have two perpendicular planes of rigid rotation. (Clifford proved this in the 19th century.) Now there is nothing stopping us from thinking of planes of rotation here in 3D Universe. It's the...
  5. Trikenstein

    I Ball free fall 100m at equator, where is the landing spot?

    We have a weekly fun random chat to break from the routine of WFH. A science quiz poped up. There is no consensus on the good answer. We need 3rd party opinion. You are at the equator, dropping a steel ball into a dry well, the depth is 100 meters, the mass of the ball is 1kg. The starting...
  6. jk185

    I Coriolis acceleration of a projectile launched at the equator

    I have a question about the Coriolis acceleration experienced by a projectile launched from the surface of a rotating body. Say a ball is launched at 45 degree angle relative to the surface at some initial velocity v0. Let's further specify that the ball is launched due north from the equator...
  7. P

    A Carnot engine between the Earth's poles and equator

    Earth absorbs and releases a massive amount of energy as a part of the day night cycles.(~100 Peta watts of solar radiation received) And the temperature difference between the poles and equator drive weather phenomenon, which happens at an energy scale beyond technology. I am wondering if one...
  8. bo reddude

    B Why doesn't the Earth at the equator experience a sonic boom?

    The Earth's circumference at the equator is 24,901 miles, or 40.075 million meters. It rotates completely once a day or in 86400 seconds. The speed of sound is 343 m/s and the Earth moves at the equator at 40.075 million m/86400 s = 463.831019 m / s which is clearly faster than the speed of...
  9. L

    Find g, measured to be 9.78 at the equator, when Earth is still

    If we think about the forces acting on an object at the surface of the Earth, these forces would be the weight force (mg) pulling downwards and the normal force (N) acting upwards . If the Earth were to stop rotating, then according to Newton's first law the forces must balance, meaning the net...
  10. D

    Endless bridge around the equator and gravity

    Hi, I’ve got a question. it seems that engineers, structural mainly, don’t seem to understand how gravity works regarding an endless stationary (steel) ring/bridge around the equator. Many if not all have said that such a ring would be modeled as two half circles pushing into each other. So the...
  11. P

    Why do hurricanes always turn north, away from the Equator?

    Hurricanes tend not to move towards the Equator for very long, turning north fairly soon, and have never been known to reach it, I think. Likewise cyclones in the southern hemisphere, which turn south before reaching it. Why is this? I have two tentative explanations. 1. Hurricanes start out...
  12. J

    Frame of reference question: Car traveling at the equator

    Earth rotate from west to east with 460m/s at equator. Car travel at equator from east to west at speed 460m/s. 1- What is car speed from inertial ref.frame? zero?How is zero if car travel in curved line? 2-What is car speed from rotational frame ? 3-How much is car weight,compare to car...
  13. JD_PM

    I Why launching closer to the equator constitutes an advantage

    I recently realized that some of the most used Space Centers (for instance the Kennedy Space Center, Merritt Island, FL (US), by NASA, the Guiana Space Center ,French Guiana, by ESA and the Baikonur Space Center ,Kazakhstan's area leased to Russia, by Roscosmos) are relatively close to the...
  14. AN630078

    Gravitational Field Strength at the equator and poles

    1. The centripetal force is equal to F= mv^2/r. The velocity of the Earth can be found by: V=2πr/T T=1 day = 24 hr*60min*60sec=86400 s v=2π*6.4 x 10^6/86400 s v=465.4211 ... ~465 ms^-1 to 3.s.f Therefore, F=1*465/6.4 x 10^6 F=98/1280000=7.265626 *10^-5 ~7.3 *10^-5 N Would this be correct since...
  15. L

    Explaining Earth's Lower Gravity at the Equator

    The apparent ##|\vec{g}|## at the equator, away from Earth's axis of rotation is lower. I know how to calculate this difference of about ##0.03\ \frac{m}{s^2}##. However, I do not intuitively understand this. The closest I've come to an intuitive understanding: An object, whether it is on the...
  16. S

    I Speed Difference of Time on Poles vs Equator of Earth and Other Planets

    I had the wonder of whether, due to the speed difference, clocks ran at a different speed on the equator than on the poles. I then researched this, and found that, due to being closer to the centre of the Earth at the poles due to the bulging of the Earth due to spinning, the two essentially...
  17. R

    What is the Sun's energy content at the Earth's equator?

    Hello, I am looking to find out the energy (or power) content of the sunlight incident on the equatorial region during summer months. I assume, this is highest in that region. I actually want the direct energy content - not, say, the electrical output from a solar panel. This could be, in some...
  18. D

    Period of Oscillations near equator

    Homework Statement A bead slides along a frictionless wire which lies in the N/S direction, midpoint at the equator. All points along the wire are the same distance from the center of the earth. The bead is initially at rest then released a small distance, δ, to the north of the equator...
  19. Grimble

    I Is a clock on the equator time dilated?

    Clocks in orbit are time dilated due to their orbital velocity. Do we measure a similar effect for clocks on the equator when measured against clocks at the poles?
  20. M

    B Exploring the Effects of a Tower at the Earth's Equator

    The Earth rotates around its own axis within 24 hours. Theoretically, if at the equator perform a tower with a height - H, ignoring its effect on the slowdown of the Earth's rotation (we assume that the material of low density), objects and other complications, at a certain height, the linear...
  21. P

    Magnitude of the electric field at equator (measured in kV)

    Hi there Only known variables include the solar flux on the Earths atmosphere at the equator is 1.5 kWm^ -2. I've calculated the total energy from the Sun as 4 x 10^26 W, but can't seem to get to a calc of the mag of electric field at equator (measured in kVm^-2).
  22. J

    B The Moon's inclination to Earth's equator

    Is there an on-line calculator or a table that would allow me to plug in a date (year) which would give me the moon's inclination to the plane of the equator on that date? Thanks for any help.
  23. B

    Distance from the equator and human evolution

    I was pondering human evolution on different continents recently and some thoughts occurred to me: 1# the distance a region is from the equator determines the temperature of a climate all over the Earth 2# humans have probably been in regions of varying distances from the Equator long enough for...
  24. J

    Run Fastest to Weigh Most at Equator!

    Homework Statement What speed you have to run on the equator to weigh as much as possible (the greatest weight) if you do choose the right direction? Do not consider relativity. Homework Equations ravitational acceleration is 9.78 m/s2 at the equator and 9.83 m/s2 at the poles, so you weigh...
  25. bri7

    Astronomy : Velocity of approach of the Sun's equator

    The sun's rotational period is 25 days at the equator. Given that the radius of the sun is 700,000 km, calculate the max velocity of approach or recession of the Sun's equator as viewed from Earth. Find the max change in wavelength of a spectral line due to the rotation and express it as a...
  26. P

    Why is there atmosphere at the equator?

    The bulge at the equator, which Wikipedia says is 42km, means that a point on the equator (at sea level) is 21 km further away from the centre of the Earth than the poles. That's two and a half Everests! I think that the difference in the force of gravity (gravity only) between the equator and...
  27. Liam A

    I Understanding the Polar and Equatorial Temperature Differences on Planets

    on earth, we have the poles being very cold and mostly frozen, while the equator is very warm and humid. i would like to know specifically what causes this. i know it is partially because of their exposure to the sun, but i'd like to know some of the details and factors involved. i'd also like...
  28. DarkMatter5

    Coriolis Force Across the Equator

    Homework Statement A fast sprinter with a mass of 80 kg runs across the equator. What is the value of the Coriolis force he experiences? Homework Equations F=ma a=2ωVradial ω=7.27 x10-5 rads-1 Earth rotates from west to east. The Attempt at a Solution I pick a direction of travel - South to...
  29. P

    Weight is less at equator than poles -- Acceleration vectors involved?

    Neglecting equatorial bulge and using 'g' (9.81m/s^2) as standard before calculations, I wanted to see if I could calculate the change in 'g' before looking it up. Obviously this not a difficult sort of problem but I am finding myself a tad confused about something. It seemed intuitive to me...
  30. prashant singh

    I Why Are Longitudinal Lines Perpendicular to the Equator?

    I think its a defination to have infinite longitudnal lines , if line are not perpendicular than the infinite point will not add up to give the circumferance of equator, please help
  31. A

    Normal on a mass have different values at pole and equator

    why does the normal on a mass have different values at pole and equator
  32. Kernul

    Weighing a Man on the Equator: Solving the Puzzle

    Homework Statement A man that has an ordinarily weight of 780 N stands on a libra on the equator. Homework Equations What is the weight measured by the libra? The Attempt at a Solution I thought it was simple, so I just did: P = m * g Since it gives me P I can simply do: m = P / g = 780 /...
  33. gracy

    Equator and perpendicular bisector

    The pointed line is equator as well as perpendicular bisector.Right?
  34. Y

    Satellite orbiting around Earth over equator

    Homework Statement A satellite is in a circular equatorial orbit around the Earth (over the equator). If the satellite flies over Singapore 9 times a day, what is the radius of the orbit? Homework Equations r3 = T2GME/4π2 The Attempt at a Solution G = 6.67x10-11 ME = 5.97x1024 T =...
  35. R

    Why does gravity decrease at the equator ?

    I know that radial force comes into the play but the direction of gravity (9.8) is also the same as radial acceleration so instead it should increase on equator
  36. avito009

    Why Equator only exists for a rotating body like Earth?

    I read that a non rotating planet like Lubricon VI does not have equator because it does not rotate. So why only rotating planets have equator?
  37. D

    Sagnac Effect on Equatorial Plane: MG-P Exp & GR Twist

    If one were to send two light beams around the equator east and west, would the Sagnac effect occur? I know Michelson-Gale-Pearson measured it, but in their experiment the two beams would each travel both directions in separate rectangles, so I wonder if the effect would be weaker/stronger. How...
  38. F

    Inclination of Equatorial North Pole relative to Galactic Equator

    If the axis of the Earth is tilted at 23.4 degrees away from the North Ecliptic Pole, and the Ecliptic Plane is tilted at 60.2 degrees away from the North Galactic Pole, then why is the Earth's rotational axis inclined at 27.13 degrees relative to the Galactic Equator instead of (90-(60.2+23.4))...
  39. S

    Centrifugal force? Why does the Earth bulge at the equator?

    I'm trying to understand why a superdeformed nucleus may be represented as bulging perpendicular to the axis of rotation, and I'm guessing this is akin to why the Earth does so too. I've gone through secondary school and 3 years of University to have professors/teachers snigger every time they...
  40. binbagsss

    Quick EMF question - Spherical Shell- North/South Pole, Equator

    The question is: a conducting spherical shell of radius a rotates about the z axis with angular velocity ω, in a uniform magnetic field B= B_{0}\hat{z} . Find an expression for the EMF developed between: i) the north pole and the equator (2 marks); ii) the north pole and the south pole (1...
  41. C

    Compare weights at equator and poles?

    Hello, I need some help understanding this question. If we take a mass of a person as 100kg, what would he weigh at the poles and the equator, in Newtons? How do I do this please? Thanks and much appreciate some help.
  42. M

    Weight at North Pole and on the Equator

    Homework Statement You stand on a spring scale at the norh pole and again at the equator. Which scale reading will be lower, and by what percent will it be lower than the higher reading? Assume g has the same value at pole and equator. I have no need for the answer to this question but...
  43. Q

    Why do geosynchronous satellites have to orbit above the Equator?

    I get that they have to be at the same position relative to the earth but why is it that they have to be specifically above the equator? thats the sense I get from the textbooks, they all seem to emphasize the satellite being above the Equator can't you have a geosynchronous satellite...
  44. G

    DIffering Weight at equator and poles

    Homework Statement 23) A person weighs less at the equator than at the poles. The main reason for this has to do with A) the spin of the Earth. B) the shape of the Earth. C) both the spin of the Earth and the shape of the Earth. D) the influence of the sun, moon, and all the planets...
  45. Lebombo

    Sun's path in the sky during Equinox if watching from equator?

    Suppose it's the equinox, when the Earth's closest point to the sun is the equator. Would people who live somewhere along the equator see the sun rise directly from the east, move directly above so, and set directly to the west? For instance, if someone, living on the equator, were to put a...
  46. F

    Why should you feel lighter at equator if normal force is weaker?

    Ok forgetting everything about how Earth is not a perfect sphere, the greatest centripetal acceleration is at the equator. So if you say N - Mg = -Mac, N should equal M(g-ac) which gives a weaker force than the gravitational force. If the net force is a force towards the center of earth...
  47. P

    What causes the change in velocity from pole to equator on Earth?

    Assume there's a person standing at the pole of the earth. When the Earth rotates, he/she has no tangential velocity because the person is at the pole. Now if the person were to take a trip by plane and land at the equator, the person would now have a fairly large velocity because the...
  48. D

    What is the Linear Velocity of a Location on Earth's Equator?

    Homework Statement Earth rotates in on axis that goes through both the North and South Poles. It makes one complete revolution in 24 hours. If the distance from the axis to any location on the equator is 3960 miles, find the linear speed (in miles per hour) of a location on the equator...
  49. G

    Standing on a scale at the equator

    Homework Statement Homework Equations F→scale + F→g = ma That's my guess. The Attempt at a Solution Well, I'm reading it in the book. It's an example with the answer that the scale reading will be less than my weight. But I still don't understand how that works out to be...
  50. J

    Why Do We Use a Mean Sun That Moves Along the Equator Instead of the Ecliptic?

    Hi, Due to Earth's axial tilt, the Sun's annual motion is along the ecliptic that is tilted to Earth's celestial equator. When the Sun crosses the equator at both equinoxes or solstices, the Sun's daily shift is at an angle to the equator, so we have to do the projection of this shift onto...
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