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Questions tagged [astronomy]

The study or observation of objects or phenomena outside the Earth, including the Sun, Moon, planets, and stars.

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How precise were the Temples' directions (East/North)

Calculating the true astronomical North/South is very simple - find the longest way and cast a shadow. Are there sources on how precise those directions in the Temples were? Are there special Jewish ...
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2answers
90 views

Biblical description of the firmament vs. round earth in the Zohar

Zohar description of the Earth: "The entire world and those upon it, spin round in a circle like a ball,' both those at the bottom of the ball and those at the top. All God's creatures, wherever ...
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How do the outer planets: Uranus, Neptune and Pluto fit into Judaism?

It is not a secret that we discover new things in all fields of science, not mentioned in our sources all the time. We know that in Judaism the 7 planets represent/aligned with 7 spiritual forces ...
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46 views

Does Judaism differentiate between a planet and a star?

On the 4th day, G-d created Sun, Moon and the stars. Besides the Moon, Mercury, Venus, Mars, Jupiter, and Saturn were known since ancient times (not mentioning the existence of the real stars). ...
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2answers
170 views

Rabbinical sources that support the Flat Earth view

While many people are busy looking for the slightest hints of the vast scientific knowledge possessed by our Sages, I've bumped into Rasa"G's interpretation of Sefer Hayetzirah 4,2 (c.900) (is there ...
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2answers
141 views

Sources for the Earth rotating round the sun

Are there any Jewish writings that suggest the Earth rotates around the sun and is not the center of the universe?
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73 views

For the start of the day, is “sunset” astronomical or visible?

Yesterday was the equinox and I noticed that the day was longer than 12 hours according to the (secular) sunrise/sunset times. Curious, I did some investigation. One reason for the difference is how ...
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77 views

Keeping Two-day Shabbos in the Pacific Islands? [duplicate]

What's this I see about people in the Pacific Islands keeping two days of Shabbos? If it is true: Who, how, since when, and why?
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1answer
44 views

Counting and naming the stars

Why does Hashem count and name the stars in Heaven? This is mentioned in the first Rashi on Shemot, see below. I would like an explanation on this... Quote from Rashi: And these are the names of the ...
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3answers
195 views

Photographing an Eclipse

There is a general prohibition on depicting and/or owning depictions of celestial bodies, such as the sun and moon (see, e.g., the Rambam Hilkhoth Avoda Zara 3:18). Nonetheless, there are opinions ...
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3answers
200 views

Is there any evidence that Chazal knew what caused eclipses?

Many ancient cultures believed that eclipses are caused by things other than syzygy. The Egyptians had Apophis. The Hindus had Rahu. (The interested reader can see more here.) In light (ha) of the ...
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1answer
107 views

Parameters of the bad omen for eclipses

The Gemara in Succah 29a says that solar eclipses are bad omens for the nations, while lunar eclipses are bad omens for the Jews. The Gemara compares an eclipse to a king who leaves his guests sitting ...
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The moon in the future [duplicate]

We say in Kiddush Levanah, יהי רצון מלפניך...למלאת פגימת הלבנה ולא יהיה בה שום מיעוט May it be Your will...to fill the reduction of the moon, and that there should be no diminishment in it. ...
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1answer
157 views

Source for the Earth being Tilted at the Time of the Flood

In Oorah's 2009 Shmorg video, one of the tracks is about Birchat Hachama, and at around the 10 minute mark, the narrator states the following (I'm paraphrasing): The Sforno writes that before the ...
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1answer
122 views

Why did Hashem create only one planet (Earth) in the whole entire universe that can support intelligent life

Is there any rabbinic literature explaining why Hashem created only one planet (Earth) in the whole entire universe that can support intelligent life?
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2answers
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Is there lunar drift in the fixed Hebrew calendar?

It is known that there is a slight discrepancy in the average length of a year according to the Hebrew calendar and the average length of an astronomical solar year which causes a seasonal drift in ...
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0answers
194 views

Shooting Stars and Luck

There seems to be a non-Jewish association of good luck with seeing a shooting star. Is there any source for this in Judaism?
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5answers
6k views

What is the firmament?

In Genesis 1:6-8 the firmament and its creation are mentioned for the first time: And God said: 'Let there be a firmament in the midst of the waters, and let it divide the waters from the waters.' ...
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2answers
200 views

Illustrated hilchot Kiddush Hachodesh

I remember seeing about 20 years ago a beautiful annotated commentary on Rambam's hilchos kiddush hachodesh, with extensive illustrations and calculations, explained according to both ancient and ...
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498 views

Minyan, netz hachamoh, and precision in time

There are halachic sources that discuss the importance of davening shemona esrei at netz (at sunrise), some of which state that it is preferable to daven at netz over davening with a minyan (at least ...
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1answer
281 views

Is there any evidence of time-zones in Talmud? (Tanaim and Amoraim only)

There are many verses in the Talmud, Midrash and Siddur that state that the sun and moon rise and set through gates in the firmament. This would imply that there are no time-zones. To this world view ...
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1answer
410 views

Solar Power on Shabbos

What's the deal with using solar power on Shabbos? Cooking is permitted, but what of the following cases: 1) Heating water (Dud-Shemesh style) 2) Solar-powered watches 3) Solar-powered toys What ...
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1answer
181 views

What's the earliest “acknowledgement” of Heliocentrism in Judaism? [closed]

The English Wikipedia says that Heliocentrism was "official" in Judaism only by the 20th century: In later periods there were no explicit attacks on heliocentrism, although some Rabbis were not ...
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1answer
91 views

Are star stickers mutar?

Do any contemporary poskim discuss the usage of star stickers with regard to the prohibition of depicting celestial bodies (e.g. the glow-in-the-dark ones people put on walls and ceilings)? What if ...
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1answer
477 views

We're not supposed to point at stars?

I'm an Israeli Jew living in Israel. I often give "sky tours" where I show children and adults different stars and a view through a powerful binocular at objects of interest. Recently a young boy ...
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2answers
4k views

What time is sunset?

Is sunset (Shkiya) the time the sun hits the horizon or when it sunk completely below it? What about sunrise?
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4answers
310 views

How accurate is the Molad?

To the best of my knowledge the Molad is every 29.5 days + 793 Chalakim. Is there any information showing if the current Molad calculation is accurate scientifically? If it is off by how much is it ...
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3answers
200 views

Depicting a constellation

Assuming the intention is at least partly for educational purposes, Is it mutar to arrange star stickers in the form of actual constellations (say, on a ceiling) or is that included in the prohibition ...
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1answer
91 views

Where does Rashi say that Jews will be revered for knowledge of astronomy?

I remember reading a Rashi that says that the Jews will be revered for their knowledge of the stars. What's the location of this Rashi?
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1answer
101 views

Does the verse in Tehillim 147:4 imply that one cannot name a star after a person?

Usually, around Mother's Day and Valentines Day, I hear a radio commercial suggesting that, as a gift to your loved one, you can name a star after him / her. (Amazing gimmick - no inventory!!) In ...
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4answers
264 views

Why did Hashem create the world in such a way that a leap year is needed?

I understand why we have a leap year; to keep the sun and moon cycles in sync, so that Pessach is always in the spring. That's all technical, as a result of the moon orbiting too slowly - or the sun ...
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1answer
83 views

Counting years according to the solar calendar

I once heard there is an opinion in Rishonim (maybe Gaonim?) that says we count ones years of life according to the solar calender. So for example a boy would become bar mitzvah when he would turn 13 ...
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What does “shachar” in “alos hashachar” mean?

We find a number of terms referring to when morning starts and then perhaps a similar term used to refer to the time of shachris. Alos HaShachar (עלות השחר) Ayeles HaShachar (אילת השחר) and Shacharis ...
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1answer
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What b'racha do you say on seeing the Aurora Borealis (if any)?

If one is so lucky as to see the Aurora Borealis (northern lights) or its southern equivalent, does one say a b'racha? If so which one? I've heard that oseh ma'aseh v'reishit applies to comets and ...
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4answers
436 views

Plants before the Sun in the Order of Creation

Why does plant life precede the Sun in the order of creation given that plants need the Sun to do photosynthesis?
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2answers
210 views

Conservative Kiddush Levanah

The version of Kiddush Levanah printed in the Conservative movement's siddur omits the verse "כשם שאני רוקד כנגדך..." I've heard that this is because the Conservative movement believes that in an age ...
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2answers
332 views

Stars are living creatures?

the Rambam in yesodei torah says that stars are creatures with intellect. how do we reconcile this with modern science which says that they are merely inanimate balls of hydrogen and helium gas.
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4answers
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How many stars did Rashi think there were?

According to the Chabad translation, Rashi on Deut. 1:10 implies that there are more than 600,000 stars: The Lord, your God, has multiplied you, and behold, you are today as the stars of the ...
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1answer
97 views

Can one say the b'rocho of borai meorai hoeash on stars

On motsai shabbos we make havdala and also make a b'rocho borai morai hoeish on what is called today the havdala. If one does not have one and no means of making a 'light' can one make the b'rocho on ...
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3answers
282 views

Significance of number 613 regarding the mitzvot

According to the Talmud (Makos 23b) "Moshe received 613 Mitzvos. They are 365 Lavim (negative commandments), corresponding to the days of the (solar) year, and 248 Mitzvos Aseh (positive commandments),...
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2answers
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Is the midrash about the moon and sun being the same size intended literally?

The Rambam in his introduction to perek Chelek discusses midrashic literalist, and classifies different approaches of different groups to midrash. He writes: You should know that as to [...
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1answer
235 views

Aruch Hashulchan's moon-distance estimate

Aruch Hashulchan (1829–1908), Orach Chayim 397:1, says that a מיל is the same as a Russian верста (verst) or 500 сажен (sazhen), which comes to 1066.8 meters. In 426:2, he says the distance to the ...
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4answers
162 views

How to care about the molad

I have read the great answers to Purpose of announcing Molad and understood that the halakhic reason to know the molad is to know what the Sanhedrin would know when they declared a new month. But ...
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0answers
47 views

Why did God create outer space? [duplicate]

Everything God does has a reason. He created the world for us to serve him. How does most of outer space help us serve God. Or just plainly why was space created?
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1answer
171 views

Levana or Yareach?

In the entire Tanach the moon is generally called Yareach. There are 3 instances where it is called Levana: 1) ישעיהו: כד. כג. וחפרה הלבנה ובושה החמה 2) ישעיהו: ל. כו. והיה אור הלבנה כאור ...
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1answer
285 views

What defines “on this earth” from a halachic standpoint?

Rabbi Ben-Zion Firrer asked whether Torah Law must be observed in space, since Deuteronomy 12:1 says one should follow the Commandments "all of the days which you are alive on this earth." What ...
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2answers
235 views

Shouldn't the flood have ended on the 18th of Cheshvan?

Inspired by this question: New date at sunset: question on Sifse Chachamim The Torah tells us that the Flood started the 17th of Cheshvan (Bereshit 7:11) and concluded the 27th of Cheshvan (Bereshit ...
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2answers
303 views

On what basis do we understand references to Orion and the Pleiades in Iyov?

Iyov 38:31-32 reads: הַתְקַשֵּׁר מַעֲדַנּוֹת כִּימָה אוֹ מוֹשְׁכוֹת כְּסִיל תְּפַתֵּחַ: . הֲתֹצִיא מַזָּרוֹת בְּעִתּוֹ וְעַיִשׁ עַל בָּנֶיהָ תַנְחֵם: Can you tie the chains of the Pleiades ...
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5answers
756 views

Permissibility of images of celestial bodies

There is precedent in halachah that one may not create images of celestial bodies such as the moon and stars; see here for background. This is derived in the Gemara from the pasuk "Do not make [images ...
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3answers
661 views

When did hashem stop the sun?

As in the time of milchemes Ay, Hashem stopped the sun for 36 hours . Where else in Tanach did it happen? I need more then one.