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What kind of planetary conditions would be required to make a place with really intense winters and summers? Is it even possible? For example on the poles they can go with out the sun for half a year in the winter but even in the summer the angle of the sun is comparable to evening near the equator, so it never gets warm

Clarification, 25°C average in summer, -40°C in winter

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    $\begingroup$ What do you mean by "really intense"? Ranging from +40C in the summer to -40C in the winter (104F to -40F)? That's definitely possible, since it exists on earth (it's a fairly typical year in Minnesota). Or how much more extreme are you looking for? $\endgroup$ – Dave Sherohman Oct 25 '18 at 7:30
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    $\begingroup$ +25C in summer and -40C in the winter isn't that extreme. Northern Scandinavia comes somewhat close already, and that's hardly at an extreme latitude. $\endgroup$ – a CVn Oct 25 '18 at 14:20
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    $\begingroup$ The more continental climate regions of earth already have a temperature gradient that is more than what you describe. Central Northern USA / Southern Canada can experience such temperatures (as mentioned) as does central Asia. From Iran, Pakistan, Afghanistan through Khazahstan or Mongolia up to espeically Russia you can notice some extreme temperature gradiants from season to season. $\endgroup$ – Adwaenyth Oct 25 '18 at 14:31
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    $\begingroup$ I live in Winnipeg. It can be +47C on Monday, and -47C on Tuesday. This is just normal. So the planet you are looking for is Earth. $\endgroup$ – Trevor D Oct 25 '18 at 17:37
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    $\begingroup$ @TrevorD Winnipeg has never even recorded +47, the record max is +42. Similarly, the all time record low inWinnipeg is -47, which was decades ago. The last occurrence of -40 was 2007. The greatest temp change in Winnipeg for a single 24 hour period was approximately 40 degrees, nothing close to what you say. $\endgroup$ – Shalop Oct 25 '18 at 21:02

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Nothing says the orbit of your planet has to be as close to circular as the Earth's. All orbits are elliptical, with the sun at one of the two foci. (Even a circle is an ellipse, it just has both foci in the same space).

The eccentricity of the ellipse is a measure between 0 and 1 of how stretched out it is; if it is very small the orbit is nearly circular. Earth's eccentricity is 0.02.

Regardless of any axial tilt; if the orbit of your planet is stretched enough, it will be close to its sun for part of the year (closest at perihelion) and far from its sun for part of the year (furthest at aphelion), and these can correspond to a hot summer and cold winter, respectively. On Earth, this is a variation of just 3%, but it can be made longer.

No elliptical orbit is off limits; Haley's comet is in orbit around the Sun, and it's distance varies from 88 million km to 5.2 Billion kilometers; i.e. inside the orbit of Venus (108 million km) to outside the orbit of Neptune (4.5 billion km); with corresponding super-heating and deep freeze.

So just a very little bit more eccentricity (stretching) of your orbit can do this, it doesn't have to be extreme. I don't have the formula for computing the solar energy reaching the planet (should follow a square law I think) or for translating that into average temperatures; but that is where I would take the research next. Perhaps other readers know this off the top of their head. I think this is the least exotic method of increasing the extremes between summer and winter, just make the planet about 10% further away from its sun in winter than it is in summer.

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    $\begingroup$ I think increasing the axial tilt is a less exotic method than to render the orbit more elliptical. And now I wonder what the most exotic method would be... $\endgroup$ – Battle Oct 25 '18 at 11:44
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    $\begingroup$ @Battle I think there is a limit to what range the axial tilt can accomplish (specifically a limit of 45 degrees). There is no limit to the range of temperatures that greater eccentricity can accomplish! And we don't know how the axial tilt came to be (probably the moon-forming collision, which is presumably a very exotic causation), but orbits can naturally occur at any degree of eccentricity. $\endgroup$ – Amadeus Oct 25 '18 at 11:51
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    $\begingroup$ Relating to the last sentence, it's worth noting that Earth's distance to the Sun varies from 147M km to 152M km (an about 3% difference), yet summer in the northern hemisphere occurs when Earth is at the farthest from the Sun. This is because of axial tilt. $\endgroup$ – a CVn Oct 25 '18 at 12:17
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    $\begingroup$ @αCVn This! Anyone should be aware that the varying distance of the Earth to the Sun has a negligable effect on the seaons. However, if we think on deep sky objects that come to the Sun much closer than 1 AU and depart far beyond Pluto, the effect becomes more interesting. $\endgroup$ – rexkogitans Oct 25 '18 at 12:49
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    $\begingroup$ @Amadeus - I don't think that's right. At 90⁰ the arctic/antarctic circles lie at the equator. A pole at midwinter will be a very long way from any ground that is receiving sunlight, and at mid-summer will be a long way from ground that is not sunlit (and the pole will have the sun at the zenith all day - it's going to get hot). $\endgroup$ – Martin Bonner Oct 25 '18 at 13:17
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If you want averages of 25 degrees C during summer and -40 degrees C during winter, you don’t really need an axial tilt which is higher than that of the earth, or even a higher eccentricity.

Indeed there are real places in Siberia which already have averages comparable to the ones you prescribed.

Perhaps the closest such climate is Yakutsk, with a July mean of 20C and a January mean of -39C. Other comparable ones include

Oymyakon: January -46C, July 15C

Verkhoyansk: January -45C, July 17C

Seymchan: January -38C, July 16C

Notice that the key feature of these climates is the tremendous continentality caused by the lack of nearby water bodies, which allows the Siberian high to form and thus allows for such massive seasonal fluctuations. Hence, one possible solution to this is just to make our own planet more continental (e.g. get rid of the Arctic and Pacific oceans).

All climate data comes from Pogoda Climat: 1 2 3

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    $\begingroup$ Interesting, that's a little further North than I was expecting - clearly continentality is much more important than latitude. $\endgroup$ – Martin Bonner Oct 25 '18 at 19:58
  • $\begingroup$ Bodies of water make for very effective 'thermal capacitors' and damp out temperate fluctuations quite nicely. $\endgroup$ – Sobrique Oct 26 '18 at 15:28
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The answer by Jannis explains that increasing the axial tilt of your planet will do this.

The other thing that will help is a large continent at mid-latitudes. "Large" so that the middle is a long way from the moderating effect of the oceans (water heats up and cools down much more slowly than rock). If it is too near the equator there isn't much variation in sunlight over the year; if it too near the pole there isn't enough sunlight in summer to get it hot.

Not very coincidentally, Minnesota (with a range of ±40 C) as pointed out by Dave Sherohman is right in the middle of the North American continent at about 46⁰N.

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As you might know: the seasons are related to the earths not linear axis.
The earth 'flies' like that around the sun:

The effect of the axial tilt means more and 'stronger' sunlight for summer the summer season, while less for winter season. If you shift the axis much more, seasons will get stronger and with that more area has the polar night and day.

Hope it helps :)

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    $\begingroup$ True, but that's only a part of itma lot depends on landmass distribution. $\endgroup$ – Mołot Oct 25 '18 at 7:43
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Per Amadeus's answer, increasing the planet's orbit sufficiently should, indeed, make for warmer Summers and colder Winters. (This should be a comment but I'm a little short of the requisite reputation for it.) However, it must be noted that seasons produced in such a fashion would not be of equal length. Haley's comet, for example, spends well under a tenth of its time anywhere even near the Sun.

This need not be a problem, of course, but it must be noted. Summers on such a world would be unusually short and the Winters excessively long. You may be able to counter this but only by softening the extreme changes you are after.

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For an exotic choice, your Summers and Winters could be literally day and night. Venus's day-night cycle lasts 116.75 Earth days. You could do the same for your world. Six months of nighttime and six months of daylight would make for an fascinating--albeit deadly--world.

You'd need ways to keep the place halfway livable as I expect this would result in temperatures far more extreme than what you want. Perhaps something like the jetstream but as a river carrying warm waters into the night side and cold waters into the day side? Or the world could be an archipelago and allow the entire ocean to flow in circles. (Do note that I've no idea if the ocean would actually behave this way.)

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Another possible twist: a planet rotating around double star. Given a right orbit and the fact that one star is going around another in the same time, you can get superhot seasons when the planet is close to the "outer" star and supercold seasons when it's on the opposite side from the main star.

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  • $\begingroup$ You're going to have a hard time getting that effect; the two stars are likely to orbit much too far from each other for this to work out. Consider Alpha Centauri AB, a binary-star system where the two stars orbit each other with a period of almost 80 years and the distance between the stars varies between 11.2 and 35.6 AU. The distance from the Sun to Earth is 1 AU. $\endgroup$ – a CVn Oct 25 '18 at 14:18
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Another interesting option would be having an elliptical orbit mixed with a fast precession) or even a variable axis tilt, not sure if this is possible).

This has been used in Tom Godwin's "The Survivors" --- you can have two different cycle mixing: for example, a series of mild seasons, corresponding to low tilt, followed by a period of harsh one, with high tilt in the case of variable tilt.

In the case of a strongly elliptical orbit, precession can change if the northern winter solstice occurs when the planet is nearer to the sun or farther away --- that can create a difference in how harsh are seasons between the two hemispheres (that could be interesting in itself). F

See also A Planet Where The Four Seasons Occur Multiple Times In One Year?

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We call it Mercury... (Actually you want much less extreme than this, so you should have no problem scaling it back by a lot.)

https://solarsystem.nasa.gov/planets/mercury/in-depth/

Temperatures on the surface of Mercury are extreme, both hot and cold. During the day, temperatures on Mercury's surface can reach 800 degrees Fahrenheit (430 degrees Celsius). Because the planet has no atmosphere to retain that heat, nighttime temperatures on the surface can drop to minus 290 degrees Fahrenheit (minus 180 degrees Celsius).

  • Variable distance orbit...but this is actually less important than:
  • Thin atmosphere -- this way the night side can get really cold. This is true for even objects like Earth's moon.
  • Reasonably close to the sun, so you get HOT and cold... if you are further out like Pluto, you just get "really cold" and "even colder".
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A point to note about using high-excentricity orbits is that winters will last longer than summers due to lower orbiting speeds farther from the star; a classical example of this is Verne's Off on a Comet.

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  • $\begingroup$ Correct me if I'm wrong, but I don't believe seasons have any correlation to a planet's distance from the sun. When it's summer in the Northern Hemisphere, it's winter in the Southern Hemisphere, yet they're both (obviously) the same distance from the Sun. $\endgroup$ – F1Krazy Oct 26 '18 at 12:22
  • $\begingroup$ @F1Krazy Correct $\endgroup$ – Jan Doggen Oct 26 '18 at 12:41
  • $\begingroup$ @F1Krazy Yes, but that holds for seasons caused by axial tilt, not by orbit excentricity. $\endgroup$ – Jan Šimbera Oct 29 '18 at 18:10

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