At a full moon, the size of the moon is the same in different places?

The moon is the most familiar celestial body. Few people know that it comes in different sizes, except rain or shine. For example, 65438+1October 3 1 is the smallest day of the full moon. Come August 18, the astronomical phenomena that only appear once a year!

2012165438+1the minimum full moon on October 28th.

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In astronomy, the size of objects in the sky is usually described according to the angular diameter observed from the earth. Angular diameter is the "apparent diameter" obtained by observing an object from a specific position when the angle is taken as the unit of measurement. The apparent diameter is the diameter of the perspective projection produced by the observed object on the plane perpendicular to the center of the observer's line of sight.

Seen from the earth, the apparent diameter of the sun is about 32', which is simply 0.53 degrees.

The size of the moon is also related to its distance from the observer. Because the orbit of the moon around the earth is an ellipse, according to astronomical observation data, the nearest (perigee) to the moon and the earth is 357 thousand kilometers, and the farthest (apogee) can reach 406 thousand kilometers.

The orbit of the moon around the earth is an ellipse with an eccentricity of about 5.5%.

The difference between apogee and perigee is about 50 thousand kilometers.

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How small is this minimum full moon?

The minimum full moon is smaller than the maximum full moon, so how much difference can there be between perigee full moon and apogee full moon? As mentioned earlier, when the moon is at perigee, it is about 360 thousand kilometers away from the earth, and the apogee can reach more than 400 thousand kilometers. It can be calculated that the apparent diameter of the moon at perigee is about 14%, and its area is about 30% larger than that at apogee, and the difference is quite obvious.

If two moons, one big and one small, are hung in the sky at the same time, the difference in size is very obvious. However, when there is only one moon in the sky and there is no reference object, this so-called size difference is difficult to distinguish with the naked eye and can only be found through astronomical photos.

Today, the full moon happens to be at the apogee. You can take pictures of Zhang Yueliang with a camera connected to a telescope or telephoto lens tonight. When the "super moon" appears on May 26th next year, you can take another photo of Zhang Yueliang with the same equipment, and the comparison between the minimum full moon and the super moon will be clear at a glance.

Comparison of Full Moon Size between Perigee and Apogee in 2007

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See the full moon from different areas

In ancient times, we had a saying that "the moon grew up on the sea now, and the horizon is * * *". So, do people in different areas, such as Mary in London and Li Lei in Beijing, see the full moon the same?

Strictly speaking, it's different. Due to the relative position (latitude and longitude) and other natural conditions, even at the same time on the same day (for example, 8 pm Beijing time and 8 pm London time), the size of the full moon people see is slightly different. Because the moon has a certain inclination with the equatorial plane when it revolves around the earth, there will be a small deviation in height (distance) when it runs over Beijing and London. Due to the scattering of light by the earth's atmosphere, the longer the path of moon light passing through the atmosphere, the stronger the scattering, and the bigger the moon will be. However, because the average distance between the earth and the moon is about 380,000 kilometers, under such a small height (distance) deviation in different areas of Beijing and London, the difference in the size of the full moon in different areas is obviously invisible to the naked eye and almost negligible.

The full moon in the Palace Museum in Beijing

Full moon in London's Fragments Building

The combined satellite of Mars and Uranus is in full operation.

It is worth mentioning that in addition to this "minimum full moon", just one day ago (101October 30), there was a full moon phenomenon on Mars. The combination of Mars and the moon means that Mars moves to a point near the moon in its orbit. At this time, people can see that the silver moon and the red Mars in the sky are close together, reflecting each other and shining together.

The time for the merger of Mars and the moon is usually very short, about 10 minutes to about 20 minutes, mainly to watch the process of the gradual merger of Mars and the moon. And this astronomical phenomenon appears almost every year.

This photo was taken on the Black Sea coast of Bulgaria before sunrise. When Mars meets the moon, if you look up at the starry sky, you will find such a beautiful scene.

Because Mars is a big planet, people can observe this phenomenon with the naked eye, not to mention astronomy enthusiasts using small telescopes.

In addition, tomorrow morning (1 65438+1October1) is the time when Uranus will collide with the sun. Uranus covers the sun, which means that Uranus and the sun are just on both sides of the earth, almost in a straight line. At this time, Uranus is closest to the earth and has the highest brightness, which is the best time to watch Uranus in a year.

Astronomical enthusiasts can vaguely see its blue-green circular surface through astronomical telescopes. Most of us can see its "beauty" vaguely with the naked eye in places far away from light pollution, such as suburbs or hilltops.

Telescopes and related shooting equipment are good helpers for astronomy enthusiasts to observe Uranus rushing to the sun in the earth sky. The above picture is a carefully designed composite photo with multiple exposures. Uranus is in the red circle in the upper left corner.

Living in a bustling city, we pay less and less attention to the starry sky overhead. Although our Chang 'e project has put the lunar rover on the surface of the moon, our simple wishes since ancient times should not be forgotten.