Would seasons still exist if Earth wasn't tilted?

[requirer]

And why?

[Genady]

Do you mean seasons as in spring-summer-fall-winter?

[Lorentz Jr]

Maybe a tiny bit from the eccentricity of Earth's orbit, but I don't think it would be noticeable.

The tilt of Earth's axis is about 23 degrees. So, at 37 degrees latitude (the United States and Europe), the angle between a vertical on Earth's surface and the line to the sun is 14 degrees in Summer and 50 degrees in Winter (37-23 vs. 37+23). The cosines of those angles are .97 and .64 respectively, so the ground gets about 50 percent more sunlight in Summer than it does in Winter (.97/.64 = 1.5). Without that, no, there would be no seasons.

Edited December 29, 2022 by Lorentz Jr

[MigL]

21 minutes ago, Lorentz Jr said:

Without that, no, there would be no seasons.

I tend to agree. We wouldn't get seasons as we now know them, but I wouldn't word it as strongly as you have.
Earth's orbital eccentricity is 0.6; not that great, but enough to have some measurable effect

[Lorentz Jr]

3 minutes ago, MigL said:

Earth's orbital eccentricity is 0.6

0.017

[MigL]

Sorry, my mistake.
Max eccentricity is listed as 0.057 
I rounded up to 0.06 , but forgot to add a zero.

Maximum eccentricity and minimum vary over a period of 92000 years, and the minimum is 0.005.
Your value is the current eccentricity.

[sethoflagos]

7 hours ago, requirer said:

And why?

The poles would be in permanent twilight which would I guess tend to stabilise the Antarctic ice sheet and see the northern ice sheets extend over northern Eurasia and North America.

The ITCZ would stabilise over the equator giving permanent cloud cover to the tropics, and reducing seasonal rains in the subtropics. Subtropical deserts would therefore extend towards the temperate latitudes, which would enjoy an 'interesting' climate given the intensification of the north-south temperature gradient.

Most of these processes would markedly increase the earth's albedo and perhaps even reverse the current warming trend.

Sounds like a good attempt at restablishing snowball earth. 

So no noticeable seasons. Not much of anything really.

[Genady]

Not only that seasons would not exist, but also a year would not have any meaning, except for a purely astronomical curiosity of repeating star patterns.

[Sensei]

The seasons are here only temporarily..
After billions of years, the Earth will face the same problem as the Moon, i.e., a tidal lock towards a heavier space object..

[Janus]

16 hours ago, Sensei said:

The seasons are here only temporarily..
After billions of years, the Earth will face the same problem as the Moon, i.e., a tidal lock towards a heavier space object..

Assuming the Earth isn't engulfed when the Sun enters its red giant stage, you'd be looking at something more like trillion of years, with a lot happening along the way.

Right now, the Moon exerts the largest tidal effect on the Earth,  So, first it will lock to it.  Tidal braking from the Sun will continue to work to slow its rotation, But the Moon will fight it. The basic effect will be that as the Sun slows the Earth, it begin begins to rotate slower than the Moon orbits.  In this scenario, the Moon-Earth tidal reaction is for the Moon to give up some of its angular momentum back to the Earth, dropping into a lower, even faster orbit.   Even if, at first, the Sun has the advantage, the Moon will eventually move in close enough to once again be the dominate tidal effect,  The Earth's rotation will begin to speed up again, with the Moon getting closer and closer.

Then eventually, the Moon would pass below the Roche limit and break up into a ring.  With its mass spread out in evenly around the Earth as a ring, it loses it tidal influence, and now the Sun could eventually lock it to itself.

And even being tidally locked to the Sun wouldn't guarantee an end to "seasons".  The Earth could be tidal locked to the Sun and still have an axial tilt. It would rotate once per orbit, but the North pole would still lean towards the Sun at one part of the orbit, and away half an orbit later.  We see this with the Moon, which is tidally locked to the Earth, it has a small axial tilt of 6°  It alternates between showing us more of its North pole or South pole during it orbit.

[TheVat]

On 12/29/2022 at 8:07 AM, Lorentz Jr said:

Maybe a tiny bit from the eccentricity of Earth's orbit, but I don't think it would be noticeable.

Thanks to Milankovich cycles, however, that eccentricity gets more pronounced every 100,000 years or so.  When Earth’s orbit in the Milankovich cycle is at its most elliptic, about 23 percent more incoming solar radiation reaches Earth at our closest approach to the Sun each year than does at its farthest from the Sun. (it's currently at 6.8% because we are at the least elliptical part of the cycle) This would have a sort of seasonal effect even without an axial tilt.

The effect wouldn't be as pronounced as we get from obliquity, but it would be something.  

[Lorentz Jr]

15 minutes ago, TheVat said:

eccentricity gets more pronounced every 100,000 years or so.

That's a long season!

[Saber]

Once i  made an Excell  file  that   you  gave  your Lat.   and  it  showed  @ what Lat. you  would be in  each  of the  years 52  weeks if  we assume that the place   sun in  perpendicular  is  0 Deg.

[vishvajit]

If the Earth were not tilted on its axis?.

The tilt of the Earth's axis causes the variation in the amount of sunlight received by different parts of the Earth throughout the year, which leads to the seasons. Without the tilt, the amount of sunlight received by different parts of the Earth would be more consistent, the seasons could be different from what we know.