Why Were Planets Visible to Ancient People but Not Us?

[lucivaldo]

Let's be honest...Why were planets visible to the ancient people and not to us humans any longer? Is it because the planets distanced? How can some planets distance themselves while others don't? It's said that light pollution has affected the visibility of planets in the sky, whereas there still reports of people seeing at least one planet in the sky. So how come ancient astrology was on right before the telescopes?

 

[Orodruin]

Why were planets visible to the ancient people and not to us humans any longer?

This is an incorrect supposition. Many planets are visible to the naked eye - brighter than the stars. Most notably Venus and Mars, but I regularly see Mercury, Jupiter, and Saturn too.

Is it because the planets distanced? How can some planets distance themselves while others don't?

It is unclear what you mean by this. The planets all have different orbits, resulting in different periods and therefore varying distances.

So how come ancient astrology was on right before the telescopes?

You have to separate astrology from astronomy. The latter is an empirical science, the former is hokum.

Ancient astronomers could easily measure the movement of the planets. Saturn and closer planets are visible to the eye without problem. Uranus was not discovered until the 18th century and Neptune 19th.

 

[lucivaldo]

This is an incorrect supposition. Many planets are visible to the naked eye - brighter than the stars. Most notably Venus and Mars, but I regularly see Mercury, Jupiter, and Saturn too.It is unclear what you mean by this. The planets all have different orbits, resulting in different periods and therefore varying distances.You have to separate astrology from astronomy. The latter is an empirical science, the former is hokum.

Ancient astronomers could easily measure the movement of the planets. Saturn and closer planets are visible to the eye without problem. Uranus was not discovered until the 18th century and Neptune 19th.

How come i haven't been capable of pointing out any planets on my own? and the only one planet that i was pointed to looked allot like a normal star in the same white seeming color. What colors do you see the planets you pointed out in?

 

[phinds]

How come i haven't been capable of pointing out any planets on my own?

I don't see how you can expect us to know why you fail to do what most of the rest of us do easily.

 

[mfb]

To the naked eye, planets look very similar to bright stars. The most notable difference is their position in the sky which varies a bit from day to day. They also tend to flicker a bit less in turbulent air.

 

[lucivaldo]

I don't see how you can expect us to know why you fail to do what most of the rest of us do easily.

Im being honest i don't see any planet and the only one shown to me didn't look like a planet it looked more like a star I don't need your insult at all...how long does one have to look in the sky without a telescope until they notice the orbit of a planet?

 

[1oldman2]

Combine this info http://www.space.com/5743-storied-history-word-planet.html with the fact that the "Ancients" compiled generations of observations, let me know your thoughts.

 

[fresh_42]

Light pollution plays a crucial role. Especially if you live in an urban area. And other than phinds, I doubt that I could find or see Mercury. Venus isn't difficult. She is a little brighter than stars and changes position within hours. Sometimes Mars is easy, too, if it can be seen at all, because it really appears to be a little orange and as Venus, is slowly moving. I haven't seen Jupiter or Saturn either, although I tried. But I guess my main problem (beside light pollution) was, that I didn't knew very well where to search for. And this might be another essential point. You have to know where and also when to look at. If you have plenty of time, as your ancient astronomers probably had, you could watch and see which points are slowly moving (differences between half an hour or so). In addition you have to rule out high flying aircrafts, ISS, and some other man made satellites.

 

[Astronuc]

As Orodruin mentioned, the planets, notably Venus and Mars, as well as Mercury, Jupiter, and Saturn are readily visible. It helps when they are on our side of the sun. Mercury might be a challenge given it's proximity to the sun, but Venus and Mars are readily visible.

how long does one have to look in the sky without a telescope until they notice the orbit of a planet?

If Venus is visible, it's readily apparent. Venus has been incorrectly called the 'Evening Star' or 'Morning Star'. It is very bright, and as mfb indicated, the planets do not flicker like the stars do.

https://stardate.org/astro-guide/ssguide/venus

There are numerous astronomical resources, which provide information on the planets, their positions and when they are visible.

For example,

You can see all five bright planets in the evening this month! But you’ll have to look hard for two of them. First, the easy ones … Jupiter, Mars and Saturn pop out as darkness falls in July 2016. Jupiter, brightest of the bunch, is found in the western half of the sky until late evening. Mars is still a bright beacon, although fainter than Jupiter at nightfall and early evening, still in a noticeable triangle with Saturn and the bright star Antares. Jupiter, Mars and Saturn are visible throughout July. Now the more difficult planets … Mercury and Venus. In July 2016, they’re low in the glare of evening twilight, quickly following the sun below the horizon before nightfall. But, as the days pass, both Mercury and Venus get higher in the sky. By mid-July, you can start searching for them with the eye, in the west after sunset. By late July, you might be able to see all five bright planets at once, briefly, after sunset. Follow the links below to learn more about July planets in 2016.

http://Earth'sky.org/astronomy-essentials/visible-planets-tonight-mars-jupiter-venus-saturn-mercury
http://Earth'sky.org/astronomy-esse...onight-mars-jupiter-venus-saturn-mercury#mars

 

[lucivaldo]

Combine this info http://www.space.com/5743-storied-history-word-planet.html with the fact that the "Ancients" compiled generations of observations, let me know your thoughts.

before i do that answer my question...how long does it take for anyone to measure the orbit of a planet without telescope?

 

[Astronuc]

how long does it take for anyone to measure the orbit of a planet without telescope?

One would have to take several measurements over days for Venus, and perhaps weeks for Mars to months for Jupiter and Saturn, keeping careful note of date and time, and positions with respect to the coordinate system.

There are plenty of astronomical resources that map the planets' orbits. Why would one bother to repeat such measurements?

One should study some basic astronomy, including understanding about the ecliptic.
http://Earth'sky.org/space/what-is-the-ecliptic

 

[fresh_42]

how long does it take for anyone to measure the orbit of a planet without telescope?

I would say it took Copernicus half a lifetime. There have been column after column of notes on positions, entire fully written books.
I don't know whether it would be easier today as we know Kepler's laws.

 

[lucivaldo]

One would have to take several measurements over days for Venus, and perhaps weeks for Mars to months for Jupiter and Saturn, keeping careful note of date and time, and positions with respect to the coordinate system.

There are plenty of astronomical resources that map the planets' orbits. Why would one bother to repeat such measurements?

Yep...Yet it seems very tiresome to me to do all that work. Do you possesses any links to the first and all records left behind by ancient people about jupiter, venus, saturn...etc?

 

[1oldman2]

Yet it seems very tiresome to me to do all that work.

 

[Astronuc]

Yep...Yet it seems very tiresome to me to do all that work. Do you possesses any links to the first and all records left behind by ancient people about jupiter, venus, saturn...etc?

I don't know about ancient data sources, but current sources are available from various national observatories. In the US, the US Naval Observatory publishes data on the moon and planets.

Depending on where one lives, one could probably contact a local (regional or national, that is) and see if they offer a publication (either hard copy or pdf) or software to determine the position or orbits of the planets.

https://en.wikipedia.org/wiki/List_of_astronomical_observatories

 

[russ_watters]

how long does it take for anyone to measure the orbit of a planet without telescope?

For the brightest planet, Venus, you really can't miss it since it is the brightest object in the night sky that isn't the moon. And if you are paying attention, you should be able to notice its movement over a period of a few weeks (or even a few days if you are really paying attention). So the problem is, quite simply, that you are spending very little time looking at the sky.
[edit]
About every other year, Jupiter and Venus are very close to each other in the sky. For an ancient with nothing else to look at at night that isn't lit by a campfire, they'd pretty much have to be blind not to notice them changing position from one day to the next:

Jupiter, Mars, Venus and Mercury are so bright and therefore so noticeable that the ancients simply couldn't help but realize they weren't stars, what with Pokemon Go and Must See TV not being available yet to occupy their time at night.

 

[1oldman2]

what with Pokemon Go and Must See TV not being available yet to occupy their time at night.

Those were the days.

 

[fresh_42]

So the problem is, quite simply, that you are spending very little time looking at the sky.

I have also the problem, that I don't have a horizon nearby and it's difficult to see objects that don't rise very far in the sky. Plus light pollution is bigger the closer it comes to human housing. So sometimes it is not as easy as simply look out of the window.

 

[fresh_42]

Just found:

http://www.sciencealert.com/look-up-5-planets-will-align-in-the-night-sky-next-month

 

[davenn]

Sometimes Mars is easy, too, if it can be seen at all, because it really appears to be a little orange

Mars ranges from easy to that flaming bright you can't miss it, as it has been for the recent months
has also been very easy to see its motion relative to the background stars. It has just finished doing a big loop into the constellation of Scorpio and back outDave

 

[rootone]

I think Jupiter is the most easy planet to spot since it's very bright when near to Earth, not so much as Venus, but Venus is only visible in the sky just after the Sun sets, or soon before Sun Rises - because it's nearer to the Sun than we are.
Jupiter is often the only bright object that can be seen in the sky at any time of night other than the Moon, if there is a thin cloud cover.
The thin clouds are enough to block almost all stars, but Jupiter still can be seen.

 

[Chronos]

All planets out to saturn are easily visible to the naked eye most of the time.

 

[sophiecentaur]

How come i haven't been capable of pointing out any planets on my own?

Partly for the same reason that you may not be able to point out a rare summer visiting bird in your local park or an unusual version of a well known saloon car. You need to get at least partially immersed in any topic before you start to get any success.
There is a small matter of Dark Adaption, which can help you, even in urban conditions. You need to spend several minutes / best part of an hour and you start to see stuff up there that was not there when you stepped outside your door.
It's along these lines:-
Q: "Can you play the piano?"
A: "Dunno, I've never tried."

As for the Ancients, people tend to confuse technology with intelligence and ingenuity. These old guys were just as smart as us and have only been proved 'wrong' in the light of some serious help from later technology. The lack of light pollution was a significant advantage that they had. Plus enough money to employ servants (or slaves) to allow them to devote their lives (24/7) to their study.

 

[Astronuc]

To determine how long it would take to calculate or plot the orbit of a planet, one would need to determine how accurate one wishes the calculation to be. Consider the following:

Planet         Distance from     Mass
             Sun (millions km)  10^22 kg         Solar orbital period
Jupiter             778         190,000          4332 days (10.87 years)
Saturn             1429          56,900         10760 days (29.48 years)

So for the orbit of Jupiter, it would take nearly 11 years to find Jupiter in the same region of sky (against the stellar background) and nearly 30 years for Saturn. One would need a very good surveying instrument. One could make yearly measurements against the stars, then gradually construct an orbit based on the geometry between the Earth and the star field.

http://www.telescope.org/nuffield/pas/solar/solar7.html

 

[1oldman2]

The thin clouds are enough to block almost all stars, but Jupiter still can be seen.

Here is a good example.

 

[mfb]

You won't see that much with the naked eye however.

 

[sophiecentaur]

Technically, though, the ancients must have been really on the ball. Distances had to be done with trigonometry - as with a rangefinder and with a maximum baseline of hundreds of km. As far as I can estimate, this would need measurement of the difference in angle of two views of, say, the Sun against the 'fixed' stars from two terrestrial sites. A baseline of 150km and the Sun's distance being 150 X10⁶ km would give a difference in angle of 10^-6 radians, which is less than 1" of arc. Good stuff, that you would find difficult to do with stuff out of your garage. (No Scientific Equipment supply shops in those days.)
EDIT: The Sun was a daft example, of course. You can't see any fixed stars when the Sun's out. But you could do it with Mars or Venus.

 

[mfb]

The distance of Moon got estimated via triangulation with a somewhat reasonable accuracy. The sun is too far away for that. In principle you can use the Earth/Moon baseline if you estimate the fraction of the visible part of the moon that gets sunshine (it is a bit more than 50% if the sun is just at the horizon for you and moon is directly above you), but that method needs telescopes and ideally cameras to be reliable. The speed of light plus precise timing of Jupiter moons and later previously Venus transits (for triangulation) gave more reliable estimates around ~1650-1750.

 

[sophiecentaur]

Interesting and it resolves my problem with such tiny angles - but they didn't have telescopes and the early instruments were not too good.
They must have used many different measurements of as many different astronomical objects as they could. Their advantage was that they had a lot of time to play with.
Once they had the Sun's distance, they could invent the Astronomical Unit and could use parallax for finding some of the bigger distances from different places in the Earths orbit. An impressive network of information and measurements which pulled itself by its bootstraps from relatively small distances to larger ones.
I was gobsmacked when I learned how the oscillation rates of the Cepheid variables would tell you the absolute magnitude and that would give you the distance of amy variable you saw from its relative magnitude. But that was all relatively recent. It wasn't until the 1920s (iirc) that other galaxies were recognised as being outside of our own. That's nearly in my lifetime - at least my Dad's lifetime.

 

[mfb]

Once they had the Sun's distance

They did not have that. Here is a summary table. All the Greek estimates were not better than guesses. Wendelin (1635, Earth/Moon baseline triangulation) and Horrocks (1639, size of Venus during transit) were the first estimates that were somewhat reasonable - both got the distance wrong by a factor 2.

Huygens got a good estimate in 1659, but probably more based on luck than on actual precision.

Cassini and Richter used the Mars parallax in 1672, their value was just 10% off. The venus transits in 1761 and 1769 then allowed to narrow down the distance to sun to ~2% uncertainty, and the next set of transits 1874 and 1882 together with abberation and the known speed of light brought it down to 0.1% uncertainty.

Modern radio astronomy allows to measure the distance with a precision of meters.