[scientist@work (OP)]

I thought for my entire life I can only see the moon during the night.
But the other day I just saw the moon during the day which up my mind how this is possible?

[syhprum]

The moon is large 30"" and quite close it would suprising if you could not see it during the day provided it is not to close to the Sun

[Kryptid]

Light from the Sun can still reflect off of the Moon during the day, and the Moon circles the Earth about once a month. That allows the Moon to be seen on Earth's daylit side fairly often.

[Zer0]

We can see the moon during the day for the same reason we see the moon at night. The surface of the moon is reflecting the sun's light into our eyes.

When we see the moon during the day it's because the moon is in the right spot in the sky and it's reflecting enough light to be as bright, or brighter, than the sky.

P.S. - 👍

[Janus]

P.S.  When it is at its brightest, and you know where to look,  you can even see Venus during the daytime.

[charles1948]

P.S.  When it is at its brightest, and you know where to look,  you can even see Venus during the daytime.

Yes, Venus can be seen in daytime.  I've observed it a few times.  But only when the daytime sky was absolutely clear, and showed a rich blue colour.  This provided sufficient contrast-effect, to make the tiny, white, gleaming dot of Venus stand out from the blue sky background.

These observations were made only with the naked-eye.  But if the eye is assisted by an optical instrument, such as  binoculars, Venus can be picked up quite easily in daytime.   I've found that my old pair of 5 X 40 prismatics are ideal.  These glasses have a very wide field of view.  So even if the exact position of the planet isn't known, the glasses will soon spot it by sweeping the general area.

And when the planet is found, the 5X magnification is sufficient to show the partial and crescent phases of Venus, which are pleasing to see.

[Petrochemicals]

I my entire life

How old are you?

[evan_au]

Why can I see the moon during the day?

The Moon spends a part of each day visible in the sky during daylight hours
- Apart from the day of a full Moon (when it is in the opposite direction from the Sun)
- and a few days around a New Moon, when the Moon is in the sky during daytime, but we are trying to view the dark side of the Moon, which is practically invisible close to the very bright Sun.

Overall, the Moon should be visible in the sky during some part of daylight hours for about three-quarters of the days of the month (assuming no clouds, of course!).

[charles1948]

Why can I see the moon during the day?

The Moon spends a part of each day visible in the sky during daylight hours
- Apart from the day of a full Moon (when it is in the opposite direction from the Sun)
- and a few days around a New Moon, when the Moon is in the sky during daytime, but we are trying to view the dark side of the Moon, which is practically invisible close to the very bright Sun.

Overall, the Moon should be visible in the sky during some part of daylight hours for about three-quarters of the days of the month (assuming no clouds, of course!).

I commend Evan's post, which explains it exactly.  The Moon is present in our sky just as much during the day, as during the night.

The only reason we associate the Moon with night, is because we notice it more at night than during the day.

[scientist940]

You can see the moon during the day because it always reflects the sun light! It is actually the same reason why we see the moon during the night! 
This is the case no matter if you are in Europe or travel to <tourism link removed>

[alancalverd]

Why can you see the moon at all? Because it's there.

[VannyTr]

Because only one half of the earth is illuminated by the sun during the day, we perceive the moon more at night than during the day. The sunlight also hits the moon during the day, but we rarely see it on Earth because the glow is hidden by the shine of the air illuminated by the sun.

The daytime half of the Earth is illuminated by full sunlight, which is why the moon often appears so inconspicuous and pale. But that is not the reason why we can only observe it sometimes.
 

[William Hardy]

Primarily, there are two reasons why we sometimes see the moon during the day. First of all, the moon is bright and close enough to be seen against the blue hue of the sky. Secondly, the duration for which it is above the horizon of Earth coincides with the sun, making it possible to be seen during the daytime.

[Bored chemist]

Are you stealing other people's work?

https://www.scienceabc.com/eyeopeners/why-do-we-sometimes-see-the-moon-during-daytime.html

[Zer0]

🙄

Primarily, You have quite an eye for Details.
👍

Secondary effects of looking thru a microscope, is it?
🔬

P.S. - 😁

@William Hardy
Wish you had Something NEW to Contribute to the OP.
Anyways, Welcome!
🙏