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The Sun crosses the meridian (the imaginaryline in the sky from due north to due south and passing directly overhead) at solar noon. The period between two successive solar noons is a "solar day".

When you reckon the period of time between two successive meridian transits of a distant star, or the vernal equinox, that is a "sidereal day".

In simple terms the sidereal day is the rotation period of a planet.

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10y ago
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10y ago

The Earth's "sidereal day" is simply the planet's rotation period. This is not affected by the Earth's orbiting the Sun.

The Earth's "solar day" is about 4 minutes longer than the sidereal day, and this is affected by the Earth's orbital motion. The solar day is based on the Sun's position in the sky.

The Sun seems tomove slowly eastwards across the sky during the year because of the Earth's changing position as it orbits. So, each day the Earth has to rotate for aboutan extra 4 minutes to get the Sun back in the same place in the sky. I won't go into the exact definitions here, but that's thebasic idea.

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12y ago

Because a sidereal day is determined by the direction one part of the Earth is pointing to. This direction is always the same. However, with solar days, that part has to point at the sun. From the direction the earth is pointing to, to the part of the earth that is pointing towards the sun, the difference is 1 degree. This is roughly 4 minutes more. That's why the solar day is longer.

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11y ago

The sidereal day is about 243 Earth days. That is the time for the planet to

rotate once .

The solar day is 117 Earth days,roughly. That is a big difference. On Earth

the difference between these two days is only about 4 minutes.

The reason for the big difference on Venus is that Venus rotates very slowly.

The solar day depends on the rotation of a planet AND its orbital motion.

The slow rotation makes the effect of the orbital motion much greater on

the length of the solar day.

Incidentally Venus rotates in the opposite direction to Earth. That's why

the solar day is shorter than the sidereal day. On Earth it's the other

way round.

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11y ago

On Earth, a sidereal day is shorter than a solar day. The sidereal day is 23 hours 56 minutes and some odd seconds. This is the time it takes for the Earth to rotate once on its axis relative to the far distant stars. In this period of time, the Earth also revolves around the Sun a little bit, enough to require nearly four additional minutes for the Earth to "catch up" with the Sun and arrive at the same point relative to the Sun, completing its Solar day.

For most planets this is typical. However for a planet like Venus, which has "retrograde" rotation, the sidereal day is the longer day.

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8y ago

A sidereal day is 23 hours 56 minutes, which the period the Earth rotates in, relative to the stars. It takes another 4 minutes for the Sun to cross the meridian as it did yesterday, because, since yesterday, we have moved 1 degree round our orbit.

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8y ago

Normally a sidereal day is just a bit shorter than a solar day, but because the direction of the rotation of Venus is opposite the direction of its revolution, and because it takes more time for Venus to complete one sidereal rotation than to complete one orbit of the sun, a sidereal day on Venus is 108% longer than a solar day on Venus.

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11y ago

A solar day is usually longer. However a planet like Venus has a longer sidereal day than solar day. That's because of its "retrograde" rotation.

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Q: Is a sidereal day longer or shorter than a solar day?
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What are some major characteristics of Venus?

Venus has 95 percent carbon dioxide in it's atmospheric composition therefore it has the strongest green house effect in the whole solar system. Venus shows Retrograde rotation. A sidereal year on Venus is shorter than a sidereal day on Venus. Venus's rotation is slowest in the whole solar system.


Which is longer the stellar day the sidereal day or the solar day?

Usually the solar day is the longest. The other two are very similar in length to each other. For example, the solar day on Earth is about 4 minutes longer than the other two "days". However, for the planet Venus the solar day is the shortest. That's because Venus has retrograde rotation.


Is a lunar year longer than a solar year?

No, a lunar year is shorter than a solar year. A lunar year is based on the time it takes for the moon to orbit the Earth, which is about 354 days. In contrast, a solar year is based on the time it takes for the Earth to orbit the sun, which is about 365 days.


Is visible light a shorter or longer wavelength energy in this spectrum?

Shorter or longer than what ? The wavelength of visible light is shorter than that of radio and heat, and longer than the wavelength of X-ray and gamma radiation. And the wavelength of green light is shorter than red light but longer than blue light.


Which planet's day is closest in length to its year?

Venus. The rotational (day) period is243.2 earth days, and the sidereal (year) period is 224.7 earth days, the only planet in our solar system that has a year that is shorter than a day.

Related questions

What planets days are longer than your year?

Venus "sidereal day" is longer than its year. Mercury's "solar day" is longer than its year. However, there is no planet in our solar system with a day longer than our year on Earth.


Why the length of day appears to be 4 minutes longer than it actually is?

There is more than one definition of "day". On the Earth one "day" is about 4 minutes longer than the other. Both are correct. The "solar day" is 24 hours, but the "sidereal day" is about 4 minutes shorter. The sidereal day is the time the Earth takes to rotate once. The solar day is the time taken (on average) for the Sun to complete its apparent daily journey around the sky. The solar day is a bit longer because the Earth orbits the Sun and that affects the position of the Sun in the sky. The Earth needs to rotate for about 4 minutes more than the "sidereal day" to have the Sun in the same place in the sky again.


Is a solar year longer than a year?

The lunar year is in fact shorter than a solar year,it consists in the region of 354 days a year.


What are some major characteristics of Venus?

Venus has 95 percent carbon dioxide in it's atmospheric composition therefore it has the strongest green house effect in the whole solar system. Venus shows Retrograde rotation. A sidereal year on Venus is shorter than a sidereal day on Venus. Venus's rotation is slowest in the whole solar system.


How long is earth time?

One complete sidereal revolution of Earth takes about 365.25636 days. That is a little longer than a solar or tropical year, which last about 365.2422 days.


If the direction of rotation of the Earth were reversed and the direction of revolution remained the same would the sidereal day be longer than the solar day?

Yes, I believe you have that correct.


Why is the longer leg longer than the shorter leg if the shorter leg is longer than the longer leg?

Because if the shorter leg was shorter than the longer leg was long, then the longer leg wouldn't be longer than the shorter leg is short. The short leg would be the longer one rather than the long one being the short one.


How long is Earth revolution time?

One complete sidereal revolution of Earth takes about 365.25636 days. That is a little longer than a solar or tropical year, which last about 365.2422 days.


Which is longer the stellar day the sidereal day or the solar day?

Usually the solar day is the longest. The other two are very similar in length to each other. For example, the solar day on Earth is about 4 minutes longer than the other two "days". However, for the planet Venus the solar day is the shortest. That's because Venus has retrograde rotation.


What is the difference between a sidereal month and and a synodic month?

A sidereal month is the time it takes the moon to complete one orbit of earth. A synodic month is longer than a sidereal month because it takes longer for the moon to go through it's phases


Is 44mm longer or shorter than 5cm?

shorter


Is a lunar year longer than a solar year?

No, a lunar year is shorter than a solar year. A lunar year is based on the time it takes for the moon to orbit the Earth, which is about 354 days. In contrast, a solar year is based on the time it takes for the Earth to orbit the sun, which is about 365 days.